Vocab v50

"diverse" means now "not white"

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Flyback diode

A flyback diode is a diode connected across an inductor used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply current is suddenly reduced or interrupted. It is used in circuits in which inductive loads are controlled by switches, and in switching power supplies and inverters.

Voltage multiplier

A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to a higher DC voltage, typically using a network of capacitors and diodes. Voltage multipliers can be used to generate a few volts for electronic appliances, to millions of volts for purposes such as high-energy physics experiments and lightning safety testing. The most common type of voltage multiplier is the half-wave series multiplier, also called the Villard cascade (but actually invented by Heinrich Greinacher).

full e=mc equation

Also E=mc^2 is the low-momentum approximation, the full equation is E^2 = m^2 c^4 + p^2 c^2 where p is the relativistic momentum. Gravity and quantum mechanics can alter the results given by special relativity.

interferometer

Collection of two or more telescopes working together as a team, observing the same object at the same time and at the same wavelength. The effective diameter of an interferometer is equal to the distance between its outermost telescopes.

how many satellites does earth have?

Currently there are over 2218 artificial satellites orbiting the Earth. Heliocentric orbit: An orbit around the Sun. In our Solar System, all planets, comets, and asteroids are in such orbits, as are many artificial satellites and pieces of space debris.

Which subatomic particle does each company use in quantum computing?

Google, IBM and Rigetti use transmon qubits; these are basically fancy LC circuits where there is a josephson junction coupled to a superconducting island. Because of this, they are also often referred to as superconducting qubits. The qubit states are the various charge levels that can exist on the circuit; since the lowest two levels are separated in energy with respect to the higher levels, a two-level system arises. Intel also used superconducting qubits, but lately has also been interested in quantum dot qubits. A quantum dot is like a 0-dimensional island on which a single electron can be placed; since the electron is a fermion it has only two natural states (and therefore makes a good qubit). The encoding can also be different, by encoding the qubit into two rather than one electron in the quantum dot. These quantum dots are built on semiconductors (like silicium, known as the go-to material in classical computing). Therefore they are also known as semiconducting qubits. Microsoft is trying a different route: they are trying to built a topological quantum computer. This is a different type of quantum computer where the qubits are encoded in topological states of matter, using quasi-particles known as (non-Abelian) anyons. A likely candidate for a physical implementation is the Majorana fermion, which can act as an anyon. You can think of these quasi-particles as a delocalized pair of electrons on a super-conducting bridge. It is worth noting that this is a considerably harder design than your 'run of the mill' transmons etc, but these topological states are intrinsically protect to many types of noise, thereby reducing or even omitting the need for quantum error correction. D-Wave's systems is based on a yet more different method of quantum computing: the adiabatic quantum computer. The way computations are performed on these computers are not alike the circuit model (which is the most used model, exploited by transmons, super-conducting and semi-conducting qubits and the like). Moreover, the qubits themselves act very differently, and the comparison of 'adiabatic-syle' qubits and 'circuit-type' qubits is not a good or well-defined comparison. An adiabatic quantum computer needs many more qubits to have the same computational power as a circuit-based quantum computer, but they are (at least on paper) equally powerful (in terms of complexity classes). There are also other types of qubits (that are not used by any of the companies you listed). Two to look out for are: Trapped-ion qubits. Qubits are encoded into states of ions; these ions are trapped by optical tweezers (light) and therefore localized and isolated. Photonic quantum computation. Qubits are encoded into degrees of freedom of photons (=light), most often the polarization. These photonic machines normally use the computation model of measurement based or one-way quantum computation, which is comparable to the circuit model but creates all entanglement in the beginning of the computation. There is no clear best implementation (yet). Transmon qubits are the most mature by most standards, but they are relatively big which will give big implications and problems when these devices will be scaled to include millions of qubits. Semiconducting qubits are a very interesting candidate because they are much smaller and implemented on (the very well developed technology of) semiconductors, but not much has been developed. Trapped ions are promising as well, but they can only be manufactured in a line (as a one-dimensional array of qubits). I'm interested to see what will happen with photonic quantum computers; they can be very promising but not many large companies are working on them; the measurement based model of QC is less popular. A topological quantum computer is the dream of many, but for now it seems out of reach in the near future, due to the exceedingly exotic nature of its design.

Rayleigh-Jeans law

In physics, the Rayleigh-Jeans Law is an approximation to the spectral radiance of electromagnetic radiation as a function of wavelength from a black body at a given temperature through classical arguments.

Forces do not exist

Most people first hear about forces in high school, with Newton. But the reality is that forces do not exist. Instead, what we have is something similar to particle physics tennis: two particles exchange another one and get either closer and closer or further and further apart. Imagine you're in outer space with a friend. You take a tennis ball and you throw it at your friend: now, you are thrown backwards because of recoil. In more physical terms, this is an example of momentum conservation: the momentum the tennis ball carries has to be equal to your momentum going the other way. When your friend catches the ball, they will also be pushed, in this case in the direction of the ball. If they now return the ball to you, the process will happen again and you and your friend will be moving further and further apart from each other. It's as if there was a force pushing you apart: however, there is no force. You are just passing a tennis ball around. With particles, something very similar happens. An electron will give off a photon, a type of boson, which will be caught by another electron. The momentum of that photon will propel both particles in opposite directions, causing what looks as a repulsive force. The force between opposite charges The situation for opposite charges is a bit more complex. My explanation may strike as unorthodox to some particle physicists, but it is the only intuitive one I could find. The trick is to consider opposite charges as if they were moving back in time. Back when Quantum Mechanics was starting, Paul Dirac made a startling discovery: the electron had to have an evil twin with positive charge, which he called the positron. Later on, Richard Feynman suggested you could view these positrons as electrons travelling back in time: a positron will do exactly the opposite of an electron, which means you can't tell between a video of a positron and a video of an electron being played backwards. When dealing with the effects of photons, this becomes important. Imagine an electron gives off a photon, which then hits the positron. An electron would be pushed forward, so the positron will do the exact opposite: it will move towards the electron! Then the positron will also give off photons, but those photons will also do the opposite of what the electron's photons would do: this means that, instead of pushing the electron away, they will pull it closer together! This means that oppositely charged particles will attract, whereas same-charge particles will repel. We can explain all of this using only particles: forces do not exist. Virtual and real particles The story above is understandable and quite close to reality, but far from a complete description. For example, if electrons are giving off photons in all directions, there shouldn't feel pushed in any direction more than any other. The trick here is that only the photon that ends up being absorbed by a nearby particle "counts": the other ones have energies that are too small to have an effect. In fact, all of those photons, including the one that gets absorbed, are undetectable and live only in our calculations: we call them virtual photons. Only the photons we get to detect are real photons. Virtual photons live within the uncertainty principle. They are allowed to exist for a brief time, as long as their energy does not exceed a certain threshold. The less energy they have, the longer they can survive. This is why forces that are transmitted by massive particles, like the weak nuclear force, have such a short range: the virtual particles are not allowed to exist for long enough to get far! However you consider this, one thing is still clear: forces do not exist. They are a side-effect of particle exchange, but have no existence of their own.

particle horizon

The "edge" of the universe. Light beyond this has not reached us yet. The particle horizon is the maximum distance from which light from particles could have traveled to the observer in the age of the universe.

Gravitational waves

The key is something called "gravitational waves." In General Relativity, space and time are not passive spectators, but the source of what we called the gravitational "force." Matter bends space and time around it, which causes trajectories that were initially straight to curve, giving rise to the familiar orbits around the Sun, for example. There is no force: particles just move in a "straight" line, it's just that this straight line is in a curved space. This is similar to being on Earth and starting to walk forward: even though our path feels "straight", we will eventually arrive at the same point because the space we live in is curved. The moment you accept that matter bends space, you realise that the curvature should be able to travel around. If I move my rubber duck back and forth in my bath, it will create ripples moving through the water; in the same way, fast-moving, massive objects will create ripples that move through space. We call these ripples "gravitational waves." Everything creates gravitational waves. However, since gravity is such a weak force, they are really hard to detect. Only massive objects like black holes will emit waves powerful enough to be felt on Earth, at least with current technology. That's why people at LIGO expected to see only events such as the merger of two black holes, which are massive enough and move fast enough to create a noticeable effect. Waves carry energy, it's kind of their thing. The energy carried by a wave is proportional to its frequency (think about it: would you rather be hit in the head 2 or 20 times per second?). When two black holes spin around each other, the frequency of the waves they give off is the same as the frequency of their spin. As they get closer, the black holes spin faster, which means they give off higher energy waves, which means they lose energy faster and get even closer. Therefore, if we ever saw the gravitational waves given off by two black holes merging, we should see waves of a frequency that is increasing faster and faster. This is exactly what LIGO has seen, which is the graph on the last frame of the comic strip. The tricky part in all of this is, of course, seeing the gravitational waves. We know they are a ripple in space and time, but what does that translate to? A ripple in space and time should mean that space contracts and expands periodically between two points. That is, if a gravitational wave goes through you right now, your head will get a bit smaller, then a bit bigger, then back to normal. The problem is that rulers will also shrink and expand, so you can't use them to figure out whether a wave just passed you! Thankfully, there's a way around. What you can do is send a photon between the two points and see how long it takes. Since the speed of light has to be the same for everyone, you should see a difference in the time and use that to detect the wave. But measuring the time it takes for a photon to do anything is not easy, because photons take almost no time to travel between places. What LIGO does is use a phenomenon called interference: it sends two photons against each other and sees if they disappear. This is based on the idea of quantum clocks that I talked about here: every particle has a little timer attached to it, which spins faster or slower depending on the energy of the particle. If two identical particles (like two photons) meet at the same place and their clocks are pointing in opposite directions, they will annihilate: they'll both disappear. I can use this to figure out if a gravitational wave has gone through. To do that, I need an L-shaped device, where I send photons which are perpendicular to each other to a certain point. I make certain that, under normal conditions, the photons disappear: we call this destructive interference. Now, what happens if a gravitational wave goes through my L-shaped device? Then, the length of one of the arms will change. This means that those photons will take longer to reach the same point, which in turn means their quantum clocks will have run for longer than those in the other arm. Therefore, now the quantum clocks of the photons coming from both sides are not exactly opposite any more, which means I should see some photons where there were none. Therefore, every time I detect a photon, it means a gravitational wave went through my device. Clever! The problem, of course, is getting a device that is sensitive enough to detect these differences. In LIGO, the arms are roughly 4 km in length and there are two L-shaped devices, which allows them to pinpoint the location of the source of waves. In general, the bigger the arms, the easier it is to detect the waves, since the change in length is proportional to the length of the arm. In fact, there is already a project under way to build a gravitational wave detector in space! It will be called LISA and made up of satellites beaming lasers at each other. Now you're in a position to understand what LIGO will announce this Thursday: they have seen the merger of two black holes with masses equal to 36 and 29 Suns into a bigger black hole with 62 masses. Now, a some quick math will show you that the total mass of the two black holes is 36 + 29 = 65, whereas the resulting black hole only has 62 solar masses. Where did the 3 missing solar masses go? They were converted into the energy of the gravitational waves. Yes, that's right: just the waves carry the equivalent of 3 solar masses worth of energy. Mind-boggling stuff. Apparently, LIGO have seen the exact frequency increase predicted by Einstein's relativity, which is yet another confirmation of his theory. The merger has been seen by both their devices, with the correct delay between them, showing that gravitational waves travel at the speed of light. Exciting times to be a physicist!

Flashtube

The lamp comprises a hermetically sealed glass tube, which is filled with a noble gas, usually xenon, and electrodes to carry electrical current to the gas. Additionally, a high voltage power source is necessary to energize the gas as a trigger event. A charged capacitor is usually used to supply energy for the flash, so as to allow very speedy delivery of very high electrical current when the lamp is triggered.

upper vs lower respiratory tract

The upper airways or upper respiratory tract includes the nose and nasal passages, paranasal sinuses, the pharynx, and the portion of the larynx above the vocal folds (cords). The lower airways or lower respiratory tract includes the portion of the larynx below the vocal folds, trachea, bronchi and bronchioles.

difference between a neutrino and an antineutrino?

Their lepton number. An antineutrino is the antiparticle partner of the neutrino, meaning that the antineutrino has the same mass but opposite "charge" of the neutrino. Although neutrinos are electromagnetically neutral (they have no electric charge and no magnetic moment), they may carry another kind of charge: lepton number.

Low-pass filter

blocks high frequencies

"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man."

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"Those that can make you believe absurdities can make you commit atrocities" - Voltaire

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A compressed spring is heavier than a relaxed spring.

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Having the opportunity to see extraterrestrial life forms would be kinda cool, but not as cool as being able to listen to their ideas and see the artwork they create. A visible representation of a being is trivial relative to the ideas that persist within that beings mind.

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Mold spores can be asexual (the products of mitosis) or sexual (the products of meiosis); many species can produce both types.

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People with aphakia, a condition where the eye lacks a lens, sometimes report the ability to see into the ultraviolet range.

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Self improvement is just a dressed up version of self conflict.

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The difference with a three-phase motor is in the stator. Where the three phase motor has three coils aligned at 120° in the stator, the capacitor start motor holds one main winding and one auxiliary winding aligned at 90°. The phase shift of 90° between the main winding and the auxiliary winding is achieved by a connected capacitor which feeds the auxiliary winding and is connected on the single-phase AC mains. The capacitor will achieve a phase shift of 90° between the main and the auxiliary winding, producing an acceptable initial torque. This motor is intended for continuous operation.

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The element Selenium conducts electricity only when a light is shined on it. In the dark, it is an insulator. As selenium(Se) element number is 34 having 2 ½ spins are vacancy. So, it mostly it acts as photocells which takes the energy from sun as solar energy as charge. Obviously, we can say it acts as conductor in light conditions and insulator in dark conditions. So, that again it needs light to act as conductor.

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Black hole starship

A black hole starship is a theoretical idea for enabling interstellar travel by propelling a starship by using a black hole as the energy source. The concept was first discussed in science fiction, notably in the book Imperial Earth by Arthur C. Clarke, and in the work of Charles Sheffield, in which energy extracted from a Kerr-Newman black hole is described as powering the rocket engines in the story "Killing Vector" (1978). In a more detailed analysis, a proposal to create an artificial black hole and using a parabolic reflector to reflect its Hawking radiation was discussed in 2009 by Louis Crane and Shawn Westmoreland.[2] Their conclusion was that it was on the edge of possibility, but that quantum gravity effects that are presently unknown will either make it easier, or make it impossible.[3] Similar concepts were also sketched out by Bolonkin. Although beyond current technological capabilities, a black hole starship offers some advantages compared to other possible methods. For example, in nuclear fusion or fission, only a small proportion of the mass is converted into energy, so enormous quantities of material would be needed. Thus, a nuclear starship would greatly deplete Earth of fissile and fusile material. One possibility is antimatter, but the manufacturing of antimatter is hugely energy-inefficient, and antimatter is difficult to contain. The Crane and Westmoreland paper states:

blackbody spectrum

A blackbody is a theoretical or model body which absorbs all radiation falling on it, reflecting or transmitting none. ... The spectral distribution of the thermal energy radiated by a blackbody (i.e. the pattern of the intensity of the radiation over a range of wavelengths or frequencies) depends only on its temperature.

hernia

A bulging of an organ or tissue through an abnormal opening. A hernia occurs when an organ pushes through an opening in the muscle or tissue that holds it in place. For example, the intestines may break through a weakened area in the abdominal wall. Many hernias occur in the abdomen between your chest and hips, but they can also appear in the upper thigh and groin areas

Ion

A charged atom due to the gain or loss of electrons

dust mite

A cosmopolitan pyroglyphidae that lives in human habitation. Allergens, such as Der p 1, produced by house dust mites are among the most common triggers of asthma. The average life cycle for a house dust mite is 65-100 days. A mated female house dust mite can live up to 70 days, laying 60 to 100 eggs in the last five weeks of her life. In a 10-week life span, a house dust mite will produce approximately 2,000 fecal particles and an even larger number of partially digested enzyme-covered dust particles. They feed on skin flakes from animals, including humans, and on some mold. Dermatophagoides farinae fungal food choices in 16 tested species commonly found in homes was observed in vitro to be Alternaria alternata, Cladosporium sphaerospermum, and Wallemia sebi, and they disliked Penicillium chrysogenum, Aspergillus versicolor, and Stachybotrys chartarum. House dust mites, due to their very small size and translucent bodies, are barely visible to the unaided eye.

Crystal oscillator

A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency. This frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators,[1] but other piezoelectric materials including polycrystalline ceramics are used in similar circuits. A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. Almost any object made of an elastic material could be used like a crystal, with appropriate transducers, since all objects have natural resonant frequencies of vibration. For example, steel is very elastic and has a high speed of sound. It was often used in mechanical filters before quartz. The resonant frequency depends on size, shape, elasticity, and the speed of sound in the material. High-frequency crystals are typically cut in the shape of a simple rectangle or circular disk. Low-frequency crystals, such as those used in digital watches, are typically cut in the shape of a tuning fork. For applications not needing very precise timing, a low-cost ceramic resonator is often used in place of a quartz crystal. When a crystal of quartz is properly cut and mounted, it can be made to distort in an electric field by applying a voltage to an electrode near or on the crystal. This property is known as electrostriction or inverse piezoelectricity. When the field is removed, the quartz generates an electric field as it returns to its previous shape, and this can generate a voltage. The result is that a quartz crystal behaves like an RLC circuit, composed of an inductor, capacitor and resistor, with a precise resonant frequency.

Diode

A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p-n junction connected to two electrical terminals.[4] Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other materials such as gallium arsenide and germanium are also used. The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction), while blocking it in the opposite direction (the reverse direction). As such, the diode can be viewed as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used to convert alternating current (ac) to direct current (dc). Forms of rectifiers, diodes can be used for such tasks as extracting modulation from radio signals in radio receivers.

Fluorescent lamp

A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps. The typical luminous efficacy of fluorescent lighting systems is 50-100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. Fluorescent lamp fixtures are more costly than incandescent lamps because they require a ballast to regulate the current through the lamp, but the lower energy cost typically offsets the higher initial cost. Compact fluorescent lamps are now available in the same popular sizes as incandescents and are used as an energy-saving alternative in homes. The fundamental means for conversion of electrical energy into radiant energy in a fluorescent lamp relies on inelastic scattering of electrons when an incident electron collides with an atom in the mercury gas. If the [incident] free electron has enough kinetic energy, it transfers energy to the atom's outer electron, causing that electron to temporarily jump up to a higher energy level. The collision is 'inelastic' because a loss of kinetic energy occurs. This higher energy state is unstable, and the atom will emit an ultraviolet photon as the atom's electron reverts to a lower, more stable, energy level. Most of the photons that are released from the mercury atoms have wavelengths in the ultraviolet (UV) region of the spectrum, predominantly at wavelengths of 253.7 and 185 nanometers (nm). These are not visible to the human eye, so they must be converted into visible light. This is done by making use of fluorescence. Ultraviolet photons are absorbed by electrons in the atoms of the lamp's interior fluorescent coating, causing a similar energy jump, then drop, with emission of a further photon. The photon that is emitted from this second interaction has a lower energy than the one that caused it. The chemicals that make up the phosphor are chosen so that these emitted photons are at wavelengths visible to the human eye. The difference in energy between the absorbed ultra-violet photon and the emitted visible light photon goes toward heating up the phosphor coating. When the light is turned on, the electric power heats up the cathode enough for it to emit electrons (thermionic emission). These electrons collide with and ionize noble gas atoms inside the bulb surrounding the filament to form a plasma by the process of impact ionization. As a result of avalanche ionization, the conductivity of the ionized gas rapidly rises, allowing higher currents to flow through the lamp. The fill gas helps determine the operating electrical characteristics of the lamp, but does not give off light itself. The fill gas effectively increases the distance that electrons travel through the tube, which allows an electron a greater chance of interacting with a mercury atom. Argon atoms, excited to a metastable state by impact of an electron, can impart this energy to a neutral mercury atom and ionize it, described as the Penning effect. This has the benefit of lowering the breakdown and operating voltage of the lamp, compared to other possible fill gases such as krypton.[22]

Fusion rocket

A fusion rocket is a theoretical design for a rocket driven by fusion propulsion which could provide efficient and long-term acceleration in space without the need to carry a large fuel supply. The design relies on the development of fusion power technology beyond current capabilities, and the construction of rockets much larger and more complex than any current spacecraft. A smaller and lighter fusion reactor might be possible in the future when more sophisticated methods have been devised to control magnetic confinement and prevent plasma instabilities. Inertial fusion could provide a lighter and more compact alternative, as might a fusion engine[1] based on a field-reversed configuration. Fusion nuclear pulse propulsion is one approach to using nuclear fusion energy to provide propulsion for rockets. For space flight, the main advantage of fusion would be the very high specific impulse, and the main disadvantage the (likely) large mass of the reactor. However, a fusion rocket may produce less radiation than a fission rocket, reducing the mass needed for shielding. The surest way of building a fusion rocket with current technology is to use hydrogen bombs as proposed in Project Orion, but such a spacecraft would also be massive and the Partial Nuclear Test Ban Treaty prohibits the use of nuclear bombs. Therefore, the use of nuclear bombs to propel rockets on Earth is problematic, but possible in space in theory. An alternate approach would be electrical (e.g. ion) propulsion with electric power generation via fusion power instead of direct thrust.

Gerotor

A gerotor is a positive displacement pump. The name gerotor is derived from "generated rotor". A gerotor unit consists of an inner and outer rotor. The inner rotor has n teeth, while the outer rotor has n+1 teeth; with n defined as a natural number greater than or equal to 2. The axis of the inner rotor is offset from the axis of the outer rotor and both rotors rotate on their respective axes. The geometry of the two rotors partitions the volume between them into n different dynamically-changing volumes. During the assembly's rotation cycle, each of these volumes changes continuously, so any given volume first increases, and then decreases. An increase creates a vacuum. This vacuum creates suction, and hence, this part of the cycle is where the inlet is located. As a volume decreases compression occurs. During this compression period, fluids can be pumped, or, if they are gaseous fluids, compressed. Gerotor pumps are generally designed using a trochoidal inner rotor and an outer rotor formed by a circle with intersecting circular arcs.[1] A gerotor can also function as a pistonless rotary engine. High pressure gas enters the intake and pushes against the inner and outer rotors, causing both to rotate as the volume between the inner and outer rotor increases. During the compression period, the exhaust is pumped out.

Gluon

A gluon (/ˈɡluːɒn/) is an elementary particle that acts as the exchange particle (or gauge boson) for the strong force between quarks. It is analogous to the exchange of photons in the electromagnetic force between two charged particles.[6] In layman's terms, they "glue" quarks together, forming hadrons such as protons and neutrons. In technical terms, gluons are vector gauge bosons that mediate strong interactions of quarks in quantum chromodynamics (QCD). Gluons themselves carry the color charge of the strong interaction. This is unlike the photon, which mediates the electromagnetic interaction but lacks an electric charge. Gluons therefore participate in the strong interaction in addition to mediating it, making QCD significantly harder to analyze than quantum electrodynamics (QED). The gluon is a vector boson. Like the photon, it has a spin of 1. While massive spin-1 particles have three polarization states, massless gauge bosons like the gluon have only two polarization states because gauge invariance requires the polarization to be longitudinal to the direction that the gluon is traveling. In quantum field theory, unbroken gauge invariance requires that gauge bosons have zero mass. Experiments limit the gluon's rest mass to less than a few meV/c2. The gluon has negative intrinsic parity. Unlike the single photon of QED or the three W and Z bosons of the weak interaction, there are eight independent types of gluon in QCD. This may be difficult to understand intuitively. Quarks carry three types of color charge; antiquarks carry three types of anticolor. Gluons may be thought of as carrying both color and anticolor. This gives nine possible combinations of color and anticolor in gluons. The following is a list of those combinations (and their schematic names): These are not the actual color states of observed gluons, but rather effective states. To correctly understand how they are combined, it is necessary to consider the mathematics of color charge in more detail. Since gluons themselves carry color charge, they participate in strong interactions. These gluon-gluon interactions constrain color fields to string-like objects called "flux tubes", which exert constant force when stretched. Due to this force, quarks are confined within composite particles called hadrons. This effectively limits the range of the strong interaction to 1×10−15 meters, roughly the size of an atomic nucleus. Beyond a certain distance, the energy of the flux tube binding two quarks increases linearly. At a large enough distance, it becomes energetically more favorable to pull a quark-antiquark pair out of the vacuum rather than increase the length of the flux tube. Gluons also share this property of being confined within hadrons. One consequence is that gluons are not directly involved in the nuclear forces between hadrons. The force mediators for these are other hadrons called mesons. Although in the normal phase of QCD single gluons may not travel freely, it is predicted that there exist hadrons that are formed entirely of gluons — called glueballs. There are also conjectures about other exotic hadrons in which real gluons (as opposed to virtual ones found in ordinary hadrons) would be primary constituents. Beyond the normal phase of QCD (at extreme temperatures and pressures), quark-gluon plasma forms. In such a plasma there are no hadrons; quarks and gluons become free particles.

High-voltage direct current

A high-voltage, direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway)[1][2][3] uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current (AC) systems.[4] For long-distance transmission, HVDC systems may be less expensive and have lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance each cycle. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be justified, due to other benefits of direct current links. Most HVDC links use voltages between 100 kV and 800 kV. A 1,100 kV link in China was completed in 2019 over a distance of 3,300 km with a power of 12 GW. [5][6] With this dimension, intercontinental connections become possible which could help to deal with the fluctuations of wind power and photovoltaics. High voltage is used for electric power transmission to reduce the energy lost in the resistance of the wires. For a given quantity of power transmitted, doubling the voltage will deliver the same power at only half the current. Since the power lost as heat in the wires is directly proportional to the square of the current, doubling the voltage reduces the line losses by a factor of 4. While power lost in transmission can also be reduced by increasing the conductor size, larger conductors are heavier and more expensive.

microbe

A microorganism, or microbe,[a] is a microscopic organism, which may exist in its single-celled form or in a colony of cells.

how does a microphone work

A microphone converts sound into a small electrical current. Sound waves hit a diaphragm that vibrates, moving a magnet near a coil. In some designs, the coil moves within a magnet. Other microphones, such as condenser microphones, work on the principle of capacitance. A crystal microphone or piezo microphone[27] uses the phenomenon of piezoelectricity—the ability of some materials to produce a voltage when subjected to pressure—to convert vibrations into an electrical signal. An example of this is potassium sodium tartrate, which is a piezoelectric crystal that works as a transducer, both as a microphone and as a slimline loudspeaker component. Crystal microphones were once commonly supplied with vacuum tube (valve) equipment, such as domestic tape recorders. Their high output impedance matched the high input impedance (typically about 10 megohms) of the vacuum tube input stage well. They were difficult to match to early transistor equipment and were quickly supplanted by dynamic microphones for a time, and later small electret condenser devices. The high impedance of the crystal microphone made it very susceptible to handling noise, both from the microphone itself and from the connecting cable. Fiber-optic microphones are used in very specific application areas such as for infrasound monitoring and noise-canceling. They have proven especially useful in medical applications, such as allowing radiologists, staff and patients within the powerful and noisy magnetic field to converse normally, inside the MRI suites as well as in remote control rooms.[30] Other uses include industrial equipment monitoring and audio calibration and measurement, high-fidelity recording and law enforcement.[31]

Polyphase system

A polyphase system is a means of distributing alternating-current electrical power where the power transfer is constant during each electrical cycle. Polyphase systems have three or more energized electrical conductors carrying alternating currents with a defined phase angle between the voltage waves in each conductor; for three-phase voltage, the phase angle is 120° or ~2.09 radians. Polyphase systems are particularly useful for transmitting power to electric motors which rely on alternating current to rotate. The most common example is the three-phase power system used for industrial applications and for power transmission. Compared to a single-phase, two-wire system, a three-phase three-wire system transmits three times as much power for the same conductor size and voltage.

Electrolysis

A process by which an electric current breaks chemical bonds. In chemistry and manufacturing, electrolysis is a technique that uses a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. The voltage that is needed for electrolysis to occur is called the decomposition potential. Electrolysis is the passing of a direct electric current through an ionic substance that is either molten or dissolved in a suitable solvent, producing chemical reactions at the electrodes and decomposition of the materials. The main components required to achieve electrolysis are an electrolyte to carry the ions from one electrode to the other, and a direct current which drives the reaction. The electrolyte is a chemical substance (such as an ion-conducting polymer) that contains free ions, and carries electric current in between the electrodes. If the ions are not mobile, as in most solid salts, then electrolysis cannot occur. The direct current (DC) electrical has to be supplied externally. This provides the energy necessary to create or discharge the ions in the electrolyte. Electric current is carried by electrons in the external circuit. Electrodes of metal, graphite and semiconductor material are widely used. Choice of suitable electrode depends on chemical reactivity between the electrode and electrolyte and manufacturing cost. Historically, when non-reactive anodes were desired for electrolysis, graphite (called plumbago in Faraday's time) or platinum were chosen.[19] They were found to be some of the least reactive materials for anodes. Platinum erodes very slowly compared to other materials, and graphite crumbles and can produce carbon dioxide in aqueous solutions but otherwise does not participate in the reaction. Cathodes may be made of the same material, or they may be made from a more reactive one since anode wear is greater due to oxidation at the anode.

Quadrupole

A quadrupole or quadrapole is one of a sequence of configurations of things like electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure reflecting various orders of complexity.

Quartz clock

A quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks are at least an order of magnitude more accurate than mechanical clocks. Generally, some form of digital logic counts the cycles of this signal and provides a numeric time display, usually in units of hours, minutes, and seconds. In modern quartz clocks, the quartz crystal resonator or oscillator is in the shape of a small tuning fork (XY-cut), laser-trimmed or precision lapped to vibrate at 32768 Hz. This frequency is equal to 215 cycles per second. A power of 2 is chosen so a simple chain of digital divide-by-2 stages can derive the 1 Hz signal needed to drive the watch's second hand. In most clocks, the resonator is in a small can or flat package, about 4 mm long. The 32768 Hz resonator has become so common due to a compromise between the large physical size of low-frequency crystals for watches and the large current drain of high-frequency crystals, which reduces the life of the watch battery. During the 1970s, the introduction of metal-oxide-semiconductor (MOS) integrated circuits allowed a 12-month battery life from a single coin cell when driving either a mechanical Lavet-type stepping motor, a smooth sweeping non-stepping motor, or a liquid-crystal display (in an LCD digital watch). Light-emitting diode (LED) displays for watches have become rare due to their comparatively high battery consumption. Chemically, quartz is a specific form of a compound called silicon dioxide. Many materials can be formed into plates that will resonate. However, quartz is also a piezoelectric material: that is, when a quartz crystal is subject to mechanical stress, such as bending, it accumulates electrical charge across some planes. In a reverse effect, if charges are placed across the crystal plane, quartz crystals will bend. Since quartz can be directly driven (to flex) by an electric signal, no additional transducer is required to use it in a resonator. Similar crystals are used in low-end phonograph cartridges: The movement of the stylus (needle) flexes a quartz crystal, which produces a small voltage, which is amplified and played through speakers. Quartz microphones are still available, though not common. Quartz has a further advantage in that its size does not change much as temperature fluctuates. Fused quartz is often used for laboratory equipment that must not change shape along with the temperature. A quartz plate's resonance frequency, based on its size, will not significantly rise or fall. Similarly, since its resonator does not change shape, a quartz clock will remain relatively accurate as the temperature changes. The electronic circuit is an oscillator, an amplifier whose output passes through the quartz resonator. The resonator acts as an electronic filter, eliminating all but the single frequency of interest. The output of the resonator feeds back to the input of the amplifier, and the resonator assures that the oscillator "howls" with the exact frequency of interest. When the circuit starts up, even a single shot can cascade to bringing the oscillator to the desired frequency. If the amplifier is too perfect, the oscillator will not start. The frequency at which the crystal oscillates depends on its shape, size, and the crystal plane on which the quartz is cut. The positions at which electrodes are placed can slightly change the tuning as well. If the crystal is accurately shaped and positioned, it will oscillate at a desired frequency. In nearly all quartz watches, the frequency is 32768 Hz,[3] and the crystal is cut in a small tuning fork shape on a particular crystal plane. This frequency is a power of two (32768 = 215), just high enough to exceed the human hearing range, yet low enough to permit inexpensive counters to derive a 1-second pulse.[4] A 15-bit binary digital counter driven by the frequency will overflow once per second, creating a digital pulse once per second. The pulse-per-second output can be used to drive many kinds of clocks.

Radioisotope thermoelectric generator

A radioisotope thermoelectric generator (RTG, RITEG) is an electrical generator that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This generator has no moving parts. RTGs have been used as power sources in satellites, space probes, and uncrewed remote facilities such as a series of lighthouses built by the former Soviet Union inside the Arctic Circle. RTGs are usually the most desirable power source for unmaintained situations that need a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical. Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. The expense of RTGs tends to limit their use to niche applications in extreme situations.

recombinant protein vaccine

A recombinant vaccine is a vaccine produced through recombinant DNA technology. This involves inserting the DNA encoding an antigen (such as a bacterial surface protein) that stimulates an immune response into bacterial or mammalian cells, expressing the antigen in these cells and then purifying it from them.

Resonant transformer

A resonant transformer is a transformer in which one or both windings has a capacitor across it and functions as a tuned circuit. Used at radio frequencies, resonant transformers can function as high Q factor bandpass filters. The transformer windings have either air or ferrite cores and the bandwidth can be adjusted by varying the coupling (mutual inductance). One common form is the IF (intermediate frequency) transformer, used in superheterodyne radio receivers. They are also used in radio transmitters.

Scalar boson

A scalar boson is a boson whose spin equals zero. Boson means that it has an integer-valued spin; the scalar fixes this value to 0. The only fundamental scalar boson in the Standard Model of particle physics is the Higgs boson. Various known composite particles are scalar bosons, e.g. the alpha particle and the pion.

Silverfish

A silverfish (Lepisma saccharina) is a small, primitive, wingless insect in the order Zygentoma (formerly Thysanura). Its common name derives from the animal's silvery light grey colour, combined with the fish-like appearance of its movements. The scientific name (L. saccharina) indicates the silverfish's diet consists of carbohydrates such as sugar or starches. Before silverfish reproduce, they carry out a ritual involving three phases, which may last over half an hour. In the first phase, the male and female stand face to face, their quivering antennae touching, then repeatedly back off and return to this position. In the second phase, the male runs away and the female chases him. In the third phase, the male and female stand side by side and head to tail, with the male vibrating his tail against the female.[10] Finally, the male lays a spermatophore, a sperm capsule covered in gossamer, which the female takes into her body via her ovipositor to fertilize her eggs. The female lays groups of fewer than 60 eggs at once, deposited in small crevices.[11] The eggs are oval-shaped, whitish, about 0.8 mm (0.031 in) long,[12] and take between two weeks and two months to hatch. A silverfish usually lays fewer than 100 eggs in her lifetime.[1]

Solid-state relay

A solid-state relay (SSR) is an electronic switching device that switches on or off when a small external voltage is applied across its control terminals. SSRs consist of a sensor which responds to an appropriate input (control signal), a solid-state electronic switching device which switches power to the load circuitry, and a coupling mechanism to enable the control signal to activate this switch without mechanical parts. The relay may be designed to switch either AC or DC to the load. It serves the same function as an electromechanical relay, but has no moving parts. An SSR based on a single MOSFET, or multiple MOSFETs in a paralleled array, can work well for DC loads. MOSFETs have an inherent substrate diode that conducts in the reverse direction, so a single MOSFET cannot block current in both directions. For AC (bi-directional) operation two MOSFETs are arranged back-to-back with their source pins tied together. Their drain pins are connected to either side of the output. The substrate diodes are alternately reverse biased to block current when the relay is off. When the relay is on, the common source is always riding on the instantaneous signal level and both gates are biased positive relative to the source by the photo-diode.

Synchronous circuit

A synchronous circuit is a digital circuit in which the changes in the state of memory elements are synchronized by a clock signal. In a sequential digital logic circuit, data is stored in memory devices called flip-flops or latches. The output of a flip-flop is constant until a pulse is applied to its "clock" input, upon which the input of the flip-flop is latched into its output. In a synchronous logic circuit, an electronic oscillator called the clock generates a string of pulses, the "clock signal". This clock signal is applied to every storage element, so in an ideal synchronous circuit, every change in the logical levels of its storage components is simultaneous. Ideally, the input to each storage element has reached its final value before the next clock occurs, so the behaviour of the whole circuit can be predicted exactly. Practically, some delay is required for each logical operation, resulting in a maximum speed at which each synchronous system can run.

Tattoo machine

A tattoo machine is a hand-held device generally used to create a tattoo, a permanent marking of the skin with indelible ink. Modern tattoo machines use electromagnetic coils to move an armature bar up and down. Connected to the armature bar is a barred needle grouping that pushes ink into the skin. Tattoo artists generally use the term "machine", pen, or even "iron", to refer to their equipment. The word "gun" is occasionally used but is widely considered derogatory or even offensive by some professional artists. In addition to "coiled" tattoo machines, there are also rotary tattoo machines, which are powered by regulated motors rather than electromagnetic coils. "The basic machine is pretty much unchanged today, in recent years variations of the theme have crept into the market, namely Manfred Kohr's Rotary machine of 1976 or Carson Hill's pneumatic machine that uses compressed air rather than electricity, but the principle is essentially the same."[1]

Thermocouple

A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor. In 1821, the German physicist Thomas Johann Seebeck discovered that when different metals are joined at the ends and there is a temperature difference between the joints, a magnetic field is observed. At the time, Seebeck referred to this consequence as thermo-magnetism. The magnetic field he observed was later shown to be due to thermo-electric current. In practical use, the voltage generated at a single junction of two different types of wire is what is of interest as this can be used to measure temperature at very high and low temperatures. The magnitude of the voltage depends on the types of wire being used. Generally, the voltage is in the microvolt range and care must be taken to obtain a usable measurement. Although very little current flows, power can be generated by a single thermocouple junction. Power generation using multiple thermocouples, as in a thermopile, is common. Nickel-alloy thermocouples Platinum/rhodium-alloy thermocouples Tungsten/rhenium-alloy thermocouples Chromel-gold/iron-alloy thermocouples Iridium/rhodium alloy thermocouples

Thyristor

A thyristor (/θaɪˈrɪstər/) is a solid-state semiconductor device with four layers of alternating P- and N-type materials. It acts exclusively as a bistable switch, conducting when the gate receives a current trigger, and continuing to conduct until the voltage across the device is reversed biased, or until the voltage is removed (by some other means). There are two designs, differing in what triggers the conducting state. In a three-lead thyristor, a small current on its Gate lead controls the larger current of the Anode to Cathode path. In a two-lead thyristor, conduction begins when the potential difference between the Anode and Cathode themselves is sufficiently large (breakdown voltage). The first thyristor devices were released commercially in 1956. Because thyristors can control a relatively large amount of power and voltage with a small device, they find wide application in control of electric power, ranging from light dimmers and electric motor speed control to high-voltage direct-current power transmission. Thyristors may be used in power-switching circuits, relay-replacement circuits, inverter circuits, oscillator circuits, level-detector circuits, chopper circuits, light-dimming circuits, low-cost timer circuits, logic circuits, speed-control circuits, phase-control circuits, etc. Originally, thyristors relied only on current reversal to turn them off, making them difficult to apply for direct current; newer device types can be turned on and off through the control gate signal. The latter is known as a gate turn-off thyristor, or GTO thyristor. A thyristor is not a proportional device like a transistor. In other words, a thyristor can only be fully on or off, while a transistor can lie in between on and off states. This makes a thyristor unsuitable as an analog amplifier, but useful as a switch.

Vacuum furnace

A vacuum furnace is a type of furnace in which the product in the furnace is surrounded by a vacuum during processing. The absence of air or other gases prevents oxidation, heat loss from the product through convection, and removes a source of contamination. This enables the furnace to heat materials (typically metals and ceramics) to temperatures as high as 3,000 °C (5,432 °F) [1] with select materials. Maximum furnace temperatures and vacuum levels depend on melting points and vapor pressures of heated materials. Vacuum furnaces are used to carry out processes such as annealing, brazing, sintering and heat treatment with high consistency and low contamination. Vacuum furnaces are used in a wide range of applications in both production industries and research laboratories. At temperatures below 1200 °C, a vacuum furnace is commonly used for the heat treatment of steel alloys. Many general heat treating applications involve the hardening and tempering of a steel part to make it strong and tough through service. Hardening involves heating the steel to a predetermined temperature, then cooling it rapidly in water, oil or suitable medium. A further application for vacuum furnaces is Vacuum Carburizing also known as Low Pressure Carburizing or LPC. In this process, a gas (such as acetylene) is introduced as a partial pressure into the hot zone at temperatures typically between 1,600 and 1,950 °F (870 and 1,070 °C). The gas disassociates into its constituent elements (in this case carbon and hydrogen). The carbon is then diffused into the surface area of the part. This function is typically repeated, varying the duration of gas input and diffusion time. Once the workload is properly "cased", the metal is quenched using oil or high pressure gas (HPGQ). For HPGQ, nitrogen or, for faster quench helium, is commonly used. This process is also known as case hardening.

Voltage regulator

A voltage regulator is a system designed to automatically maintain a constant voltage level. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages. A simple voltage/current regulator can be made from a resistor in series with a diode (or series of diodes). Due to the logarithmic shape of diode V-I curves, the voltage across the diode changes only slightly due to changes in current drawn or changes in the input. When precise voltage control and efficiency are not important, this design may be fine. Since the forward voltage of a diode is small, this kind of voltage regulator is only suitable for low voltage regulated output. When higher voltage output is needed, a zener diode or series of zener diodes may be employed. Zener diode regulators make use of the zener diode's fixed reverse voltage, which can be quite large.

Alternator

AC generator. A car's alternator produces ac voltage and is then converted to dc voltage

spacetime interval

An "interval" in spacetime is analogous to a "distance" in space or a "duration" in time. Where a distance is the difference in location between two points in space, and a duration is the difference between to instants in time, an interval is the difference between two events in spacetime.

Einstein ring

An Einstein ring, also known as an Einstein-Chwolson ring or Chwolson ring, is created when light from a galaxy or star passes by a massive object on route to the Earth. Due to gravitational lensing, the light is diverted, making it seem to come from different places.

LC circuit

An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuit's resonant frequency. LC circuits are used either for generating signals at a particular frequency, or picking out a signal at a particular frequency from a more complex signal; this function is called a bandpass filter. They are key components in many electronic devices, particularly radio equipment, used in circuits such as oscillators, filters, tuners and frequency mixers.

crystal radio

An antenna in which electric currents are induced by radio waves. A resonant circuit (tuned circuit) which selects the frequency of the desired radio station from all the radio signals received by the antenna. The tuned circuit consists of a coil of wire (called an inductor) and a capacitor connected together. The circuit has a resonant frequency, and allows radio waves at that frequency to pass through to the detector while largely blocking waves at other frequencies. One or both of the coil or capacitor is adjustable, allowing the circuit to be tuned to different frequencies. In some circuits a capacitor is not used and the antenna serves this function, as an antenna shorter than its resonant length is capacitive. A semiconductor crystal detector that demodulates the radio signal to extract the audio signal (modulation). The crystal detector functions as a square law detector,[38] demodulating the radio frequency alternating current to its audio frequency modulation. The detector's audio frequency output is converted to sound by the earphone. Early sets used a "cat whisker detector"[39][40][41] consisting of a small piece of crystalline mineral such as galena with a fine wire touching its surface. The crystal detector was the component that gave crystal radios their name. Modern sets use modern semiconductor diodes, although some hobbyists still experiment with crystal or other detectors. An earphone to convert the audio signal to sound waves so they can be heard. The low power produced by a crystal receiver is insufficient to power a loudspeaker, hence earphones are used. As a crystal radio has no power supply, the sound power produced by the earphone comes solely from the transmitter of the radio station being received, via the radio waves captured by the antenna.[3] The power available to a receiving antenna decreases with the square of its distance from the radio transmitter.[42] Even for a powerful commercial broadcasting station, if it is more than a few miles from the receiver the power received by the antenna is very small, typically measured in microwatts or nanowatts.[3] In modern crystal sets, signals as weak as 50 picowatts at the antenna can be heard. Crystal radios can receive such weak signals without using amplification only due to the great sensitivity of human hearing,[3][44] which can detect sounds with an intensity of only 10−16 W/cm2.[45] Therefore, crystal receivers have to be designed to convert the energy from the radio waves into sound waves as efficiently as possible. Even so, they are usually only able to receive stations within distances of about 25 miles for AM broadcast stations,[46][47] although the radiotelegraphy signals used during the wireless telegraphy era could be received at hundreds of miles,[47] and crystal receivers were even used for transoceanic communication during that period.[48]

Antimatter rocket

An antimatter rocket is a proposed class of rockets that use antimatter as their power source. There are several designs that attempt to accomplish this goal. The advantage to this class of rocket is that a large fraction of the rest mass of a matter/antimatter mixture may be converted to energy, allowing antimatter rockets to have a far higher energy density and specific impulse than any other proposed class of rocket. Antimatter rockets can be divided into three types of application: those that directly use the products of antimatter annihilation for propulsion, those that heat a working fluid or an intermediate material which is then used for propulsion, and those that heat a working fluid or an intermediate material to generate electricity for some form of electric spacecraft propulsion system. The propulsion concepts that employ these mechanisms generally fall into four categories: solid core, gaseous core, plasma core, and beamed core configurations. The alternatives to direct antimatter annihilation propulsion offer the possibility of feasible vehicles with, in some cases, vastly smaller amounts of antimatter but require a lot more matter propellant.[2] Then there are hybrid solutions using antimatter to catalyze fission/fusion reactions for propulsion.

Aril

An aril, also called an arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode or false aril is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ovary, an arillode forms from a different point on the seed coat.

Atomic battery

An atomic battery, nuclear battery, tritium battery or radioisotope generator is a device which uses energy from the decay of a radioactive isotope to generate electricity. Like nuclear reactors, they generate electricity from nuclear energy, but differ in that they do not use a chain reaction. Compared to other batteries, they are very costly, but have an extremely long life and high energy density, and so they are mainly used as power sources for equipment that must operate unattended for long periods of time, such as spacecraft, pacemakers, underwater systems and automated scientific stations in remote parts of the world. Batteries using the energy of radioisotope decay to provide long-lived power (10-20 years) are being developed internationally. Conversion techniques can be grouped into two types: thermal and non-thermal. The thermal converters (whose output power is a function of a temperature differential) include thermoelectric and thermionic generators. The non-thermal converters (whose output power is not a function of a temperature difference) extract a fraction of the incident energy as it is being degraded into heat rather than using thermal energy to run electrons in a cycle. Atomic batteries usually have an efficiency of 0.1-5%. High-efficiency betavoltaics have 6-8%. A thermionic converter consists of a hot electrode, which thermionically emits electrons over a space-charge barrier to a cooler electrode, producing a useful power output. Caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface ionization) to neutralize the electron space charge. Thermophotovoltaic cells work by the same principles as a photovoltaic cell, except that they convert infrared light (rather than visible light) emitted by a hot surface, into electricity. Thermophotovoltaic cells have an efficiency slightly higher than thermoelectric couples and can be overlaid on thermoelectric couples, potentially doubling efficiency. The University of Houston TPV Radioisotope Power Conversion Technology development effort is aiming at combining thermophotovoltaic cells concurrently with thermocouples to provide a 3- to 4-fold improvement in system efficiency over current thermoelectric radioisotope generators.

fuel cell

An electrical-chemical device that converts fuel, such as hydrogen, into an electrical current. A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from metals and their ions or oxides that are commonly already present in the battery, except in flow batteries. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. There are many types of fuel cells, but they all consist of an anode, a cathode, and an electrolyte that allows ions, often positively charged hydrogen ions (protons), to move between the two sides of the fuel cell. At the anode a catalyst causes the fuel to undergo oxidation reactions that generate ions (often positively charged hydrogen ions) and electrons. The ions move from the anode to the cathode through the electrolyte. At the same time, electrons flow from the anode to the cathode through an external circuit, producing direct current electricity. At the cathode, another catalyst causes ions, electrons, and oxygen to react, forming water and possibly other products. Fuel cells are classified by the type of electrolyte they use and by the difference in startup time ranging from 1 second for proton exchange membrane fuel cells (PEM fuel cells, or PEMFC) to 10 minutes for solid oxide fuel cells (SOFC). A related technology is flow batteries, in which the fuel can be regenerated by recharging. Individual fuel cells produce relatively small electrical potentials, about 0.7 volts, so cells are "stacked", or placed in series, to create sufficient voltage to meet an application's requirements.[4] In addition to electricity, fuel cells produce water, heat and, depending on the fuel source, very small amounts of nitrogen dioxide and other emissions. The energy efficiency of a fuel cell is generally between 40-60%; however, if waste heat is captured in a cogeneration scheme, efficiencies of up to 85% can be obtained.[citation needed]

Angiotensin converting enzyme 2 (ACE2)

An enzyme attached to the outer surface (cell membranes) of cells in the lungs, arteries, heart, kidney, and intestines. ACE2 lowers blood pressure by catalysing the cleavage of angiotensin II (a vasoconstrictor peptide) into angiotensin 1-7 (a vasodilator). ACE2 also serves as the entry point into cells for some coronaviruses. ACE2 counters the activity of the related angiotensin-converting enzyme (ACE) by reducing the amount of angiotensin-II and increasing Ang(1-7)[11] making it a promising drug target for treating cardiovascular diseases. ACE2 is a single-pass type I membrane protein, with its enzymatically active domain exposed on the surface of cells in lungs and other tissues.[14] The extracellular domain of ACE2 is cleaved from the transmembrane domain by another enzyme known as sheddase, and the resulting soluble protein is released into the blood stream and ultimately excreted into urine. Furthermore, according to studies conducted on mice, the interaction of the spike protein of the coronavirus with ACE2 induces a drop in the levels of ACE2 in cells through internalization and degradation of the protein and hence may contribute to lung damage.

What is an oscilloscope and how does it work?

An oscilloscope is a device that produces a graphical representation of voltage vs. time. It is used to visualize signals in electronic systems, to aid in design and troubleshooting. It is one of the basic test instruments used in the electronics field. An analog scope will display signals on a cathode ray tube (CRT), by taking the measured signal and an internally generated time reference (called the sweep or timebase), amplifying them, and applying them to the appropriate deflection plates of the CRT to deflect the electron beam and produce a trace on the screen. A modern digital scope takes the incoming signal and feeds an analog to digital converter (ADC). The ADC converts the signal into a series of binary values (at speeds of up to billions of samples per second). These values are stored in memory, and used to construct a graphical image on an LCD screen by a fast CPU and graphics generator subsystem. Digital scopes also offer the ability to perform mathematical functions on the measured signals, to determine amplitudes, frequencies, rise and fall times, etc. automatically, rather than requiring the user to make physical measurements of the image on the screen and do the math themselves.

Uninterruptible power supply

An uninterruptible power supply or uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries, supercapacitors, or flywheels. The on-battery run-time of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment. It is a type of continual power system. A UPS is typically used to protect hardware such as computers, data centers, telecommunication equipment or other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss. UPS units range in size from units designed to protect a single computer without a video monitor (around 200 volt-ampere rating) to large units powering entire data centers or buildings. The world's largest UPS, the 46-megawatt Battery Electric Storage System (BESS), in Fairbanks, Alaska, powers the entire city and nearby rural communities during outages.[1]

Anthocyanin

Anthocyanins are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue or black. Food plants rich in anthocyanins include the blueberry, raspberry, black rice, and black soybean, among many others that are red, blue, purple, or black. Food plants rich in anthocyanins include the blueberry, raspberry, black rice, and black soybean, among many others that are red, blue, purple, or black. Some of the colors of autumn leaves are derived from anthocyanins. Anthocyanins belong to a parent class of molecules called flavonoids synthesized via the phenylpropanoid pathway. They occur in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits. Anthocyanins are derived from anthocyanidins by adding sugars.[3] They are odorless and moderately astringent.

Asbestos

Asbestos is a naturally occurring fibrous mineral that was extensively mined during the early 20th century. ... There are currently no functioning asbestos mines in the United States, but Canada and many other countries continue asbestos mining in order to sell the substance to manufacturers throughout the world. Asbestos is made of naturally occurring fibrous minerals found in rocks and soil Asbestos (pronounced: /æsˈbɛstəs/ or /æsˈbɛstɒs/) is a term used to refer to six naturally occurring silicate minerals. All are composed of long and thin fibrous crystals, each fiber being composed of many microscopic 'fibrils' that can be released into the atmosphere by abrasion and other processes. Asbestos is an excellent electrical insulator and is highly heat-resistant, so for many years it was used as a building material.[1] However, it is now a well-known health and safety hazard and the use of asbestos as a building material is illegal in many countries. Inhalation of asbestos fibres can lead to various serious lung conditions, including asbestosis and cancer.[2] Archaeological studies have found evidence of asbestos being used as far back as the Stone Age to strengthen ceramic pots,[3] but large-scale mining began at the end of the 19th century when manufacturers and builders began using asbestos for its desirable physical properties. Asbestos was widely used during the 20th century until the 1970s, when public recognition of the health hazards of asbestos dust led to its prohibition in mainstream construction and fireproofing in most countries.[4] Despite this, and in part because the consequences of exposure can take decades to arise, at least 100,000 people per year are thought to die from diseases related to asbestos exposure.[5]

battery

Batteries convert chemical energy directly to electrical energy. In many cases, the electrical energy released is the difference in the cohesive[13] or bond energies of the metals, oxides, or molecules undergoing the electrochemical reaction.[3] For instance, energy can be stored in Zn or Li, which are high-energy metals because they are not stabilized by d-electron bonding, unlike transition metals. Batteries are designed such that the energetically favorable redox reaction can occur only if electrons move through the external part of the circuit. A battery consists of some number of voltaic cells. Each cell consists of two half-cells connected in series by a conductive electrolyte containing metal cations. One half-cell includes electrolyte and the negative electrode, the electrode to which anions (negatively charged ions) migrate; the other half-cell includes electrolyte and the positive electrode, to which cations (positively charged ions) migrate. Cations are reduced (electrons are added) at the cathode, while metal atoms are oxidized (electrons are removed) at the anode.[14] Some cells use different electrolytes for each half-cell; then a separator is used to prevent mixing of the electrolytes while allowing ions to flow between half-cells to complete the electrical circuit.

how perseus killed medusa?

Because the gaze of Medusa turned all who looked at her to stone, Perseus guided himself by her reflection in a shield given him by Athena and beheaded Medusa as she slept. He then returned to Seriphus and rescued his mother by turning Polydectes and his supporters to stone at the sight of Medusa's head.

Commodore 64

Best selling computer of all time brought gaming into homes The Commodore 64, also known as the C64 or the CBM 64, is an 8-bit home computer introduced in January 1982 by Commodore International.

Betavoltaic device

Betavoltaic devices, also known as betavoltaic cells, are generators of electric current, in effect a form of battery, which use energy from a radioactive source emitting beta particles (electrons). A common source used is the hydrogen isotope tritium. Unlike most nuclear power sources, which use nuclear radiation to generate heat, which then is used to generate electricity (thermoelectric and thermionic sources), betavoltaics use a non-thermal conversion process; converting the electron-hole pairs produced by the ionization trail of beta particles traversing a semiconductor. The primary use for betavoltaics is for remote and long-term use, such as spacecraft requiring electrical power for a decade or two. Recent progress has prompted some to suggest using betavoltaics to trickle-charge conventional batteries in consumer devices, such as cell phones and laptop computers.[8] As early as 1973, betavoltaics were suggested for use in long-term medical devices such as pacemakers. Although betavoltaics use a radioactive material as a power source, the beta particles used are low energy and easily stopped by a few millimetres of shielding. With proper device construction (that is, proper shielding and containment), a betavoltaic device would not emit dangerous radiation. Leakage of the enclosed material would engender health risks, just as leakage of the materials in other types of batteries (such as lithium, cadmium and lead) leads to significant health and environmental concerns.[9]

Bloody Bosons

Bosons and fermions behave quite differently. It is impossible for two fermions to ever be in the same sate: that's why electrons in atom must have different orbits and not stay all in the lower-energy one which, in turn, is why we have Chemistry. However, bosons have no problem occupying the same state: you can fit as many as you like in a crowded room. In the comic above, the guy with the little laces in his head is a photon, which is a type of boson. The guy with the crazy hair is a strange quark, which is a type of fermion. At normal temperatures, bosons and fermions behave very similarly. However, at lower temperatures most particles want to be in the lowest energy state. Fermions don't have a choice: only one of them can be fortunate enough to chill in low-energy paradise. But bosons don't have to compromise: each and every one of them can have that lowest energy. This is what allows phenomena such as superconductivity, where all electrons form pairs that behave just like bosons, allowing electric current to flow without resistance. This is the principle behind technological feats like the Maglev train. It is also the physical principle that allows the existence of Bose-Einstein condensates, a state of matter different from solids, gases, liquids or plasmas. In Bose-Einstein condensates, all bosons occupy the lower energy state and therefore behave as if they were only one particle. This allows them to perform seemingly illogical feats, like escaping out of a recipient by climbing its walls.

Bug zapper

Bug zappers are usually housed in a protective cage of plastic or grounded metal bars to prevent people or larger animals from touching the high voltage grid. A light source is fitted inside, often a fluorescent lamp designed to emit both visible and ultraviolet light, which is visible to insects and attracts them.[4] [5] The light is surrounded by a pair of interleaved bare wire grids or spirals. The distance between adjacent wires is typically about 2 mm (0.079 in). A high-voltage power supply powered by mains electricity, which may be a simple transformerless voltage multiplier circuit made with diodes and capacitors, generates a voltage of 2,000 volts or more, high enough to conduct through the body of an insect which bridges the two grids, but not high enough to spark across the air gap. Enough electric current flows through the small body of the insect to heat it to a high temperature.[6] The impedance of the power supply and the arrangement of the grid is such that it cannot drive a dangerous current through the body of a human. Many bug zappers are fitted with trays that collect the electrocuted insects; other models are designed to allow the debris to fall to the ground below. Some use a fan to help to trap the insect.

Carburizing

Carburizing,[1] carburising (chiefly British English), or carburization is a heat treatment process in which iron or steel absorbs carbon while the metal is heated in the presence of a carbon-bearing material, such as charcoal or carbon monoxide. The intent is to make the metal harder. Depending on the amount of time and temperature, the affected area can vary in carbon content. Longer carburizing times and higher temperatures typically increase the depth of carbon diffusion. When the iron or steel is cooled rapidly by quenching, the higher carbon content on the outer surface becomes hard due to the transformation from austenite to martensite, while the core remains soft and tough as a ferritic and/or pearlite microstructure. Early carburization used a direct application of charcoal packed around the sample to be treated (initially referred to as case hardening), but modern techniques use carbon-bearing gases or plasmas (such as carbon dioxide or methane). The process depends primarily upon ambient gas composition and furnace temperature, which must be carefully controlled, as the heat may also impact the microstructure of the remainder of the material. For applications where great control over gas composition is desired, carburization may take place under very low pressures in a vacuum chamber. The process of carburization works via the diffusion of carbon atoms into the surface layers of a metal. As metals are made up of atoms bound tightly into a metallic crystalline lattice, the carbon atoms diffuse into the crystal structure of the metal and either remain in solution (dissolved within the metal crystalline matrix — this normally occurs at lower temperatures) or react with elements in the host metal to form carbides (normally at higher temperatures, due to the higher mobility of the host metal's atoms). If the carbon remains in solid solution, the steel is then heat treated to harden it. Both of these mechanisms strengthen the surface of the metal, the former by forming pearlite or martensite, and the latter via the formation of carbides. Both of these materials are hard and resist abrasion. In oxy-acetylene welding, a carburizing flame is one with little oxygen, which produces a sooty, lower-temperature flame. It is often used to anneal metal, making it more malleable and flexible during the welding process.

Chlorophyll a

Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light.[3] It also reflects green-yellow light, and as such contributes to the observed green color of most plants. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport chain. Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reaction center where specific chlorophylls P680 and P700 are located.

Chlorophyll b

Chlorophyll b is a form of chlorophyll. Chlorophyll b helps in photosynthesis by absorbing light energy. It is more soluble than chlorophyll a in polar solvents because of its carbonyl group. Its color is green, and it primarily absorbs blue light. In land plants, the light-harvesting antennae around photosystem II contain the majority of chlorophyll b. Hence, in shade-adapted chloroplasts, which have an increased ratio of photosystem II to photosystem I, there is a higher ratio of chlorophyll b to chlorophyll a.[3] This is adaptive, as increasing chlorophyll b increases the range of wavelengths absorbed by the shade chloroplasts.

Concentrator photovoltaics

Concentrator photovoltaics (CPV) (also known as concentration photovoltaics) is a photovoltaic technology that generates electricity from sunlight. Unlike conventional photovoltaic systems, it uses lenses or curved mirrors to focus sunlight onto small, highly efficient, multi-junction (MJ) solar cells. In addition, CPV systems often use solar trackers and sometimes a cooling system to further increase their efficiency.[2]:30 Ongoing research and development is rapidly improving their competitiveness in the utility-scale segment and in areas of high insolation. Systems using high-concentration photovoltaics (HCPV) especially have the potential to become competitive in the near future. They possess the highest efficiency of all existing PV technologies, and a smaller photovoltaic array also reduces the balance of system costs. Currently, CPV is far less common than conventional PV systems and has only recently been made available to the residential market. The first residential installation is a 1.6 kwh system in Chatsworth, California by Radical Sun Systems. [3]:12

developmental prosopagnosia

Developmental prosopagnosia is a lifelong condition that impairs a person's ability to recognize faces, in the absence of sensory visual problems and intellectual impairment. People with this condition have normal intelligence and memory, typical low-level vision, and no history of brain injury.

Diamond battery

Diamond battery is the name of a prototype battery proposed by the University of Bristol Cabot Institute during their annual lecture[1] held on 25 November 2016 at the Wills Memorial Building. This battery is proposed to run on the radioactivity of waste graphite blocks (previously used as neutron moderator material in nuclear reactors) and would last for thousands of years. The battery, developed by the University of Bristol, is a betavoltaic cell using carbon-14 (C-14) in the form of diamond-like carbon (DLC) as the beta radiation source, and additional normal-carbon DLC to make the necessary semiconductor junction and encapsulate the carbon-14.[2] Researchers propose that C-14 gas obtained by heating the radioactive graphite waste will be collected and subjected to low pressure and elevated temperature, to produce a man-made diamond by a process known as chemical vapor deposition. A diamond made of radioactive C-14 will also be radioactive, and its radioactivity may allow it to act as a betavoltaic device, generating small electrical currents. For practical and safe use it would be enclosed inside a non-radioactive man-made diamond (made from C-12). More diamond will make more current, even with the same radioactivity, and the outer diamond will shield the user from the radiation emitted by the inner diamond.[7]

how do our cells proofread DNA after its copied?

During DNA synthesis, most DNA polymerases "check their work," fixing the majority of mispaired bases in a process called proofreading. Immediately after DNA synthesis, any remaining mispaired bases can be detected and replaced in a process called mismatch repair. If DNA gets damaged, it can be repaired by various mechanisms, including chemical reversal, excision repair, and double-stranded break repair.

Electrical resonance

Electrical resonance occurs in an electric circuit at a particular resonant frequency when the impedances or admittances of circuit elements cancel each other. In some circuits, this happens when the impedance between the input and output of the circuit is almost zero and the transfer function is close to one. Resonance of a circuit involving capacitors and inductors occurs because the collapsing magnetic field of the inductor generates an electric current in its windings that charges the capacitor, and then the discharging capacitor provides an electric current that builds the magnetic field in the inductor. This process is repeated continually. An analogy is a mechanical pendulum, and both are a form of simple harmonic oscillator.

Electroplating

Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. The term is also used for electrical oxidation of anions on to a solid substrate, as in the formation of silver chloride on silver wire to make silver/silver-chloride electrodes. Electroplating is primarily used to change the surface properties of an object (such as abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities), but may also be used to build up thickness on undersized parts or to form objects by electroforming. The process used in electroplating is called electrodeposition. It is analogous to a concentration cell acting in reverse. The part to be plated is the cathode of the circuit. In one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called an electrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that it comprises and allowing them to dissolve in the solution. At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they "plate out" onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated and thus the ions in the electrolyte bath are continuously replenished by the anode. Other electroplating processes may use a non-consumable anode such as lead or carbon. In these techniques, ions of the metal to be plated must be periodically replenished in the bath as they are drawn out of the solution.[2] The most common form of electroplating is used for creating coins, such as US pennies, which are made of zinc covered in a layer of copper.[3] The cations associate with the anions in the solution. These cations are reduced at the cathode to deposit in the metallic, zero valence state. For example, for copper plating, in an acid solution, copper is oxidized at the anode to Cu2+ by losing two electrons. The Cu2+ associates with the anion SO2− 4 in the solution to form copper(II) sulphate. At the cathode, the Cu2+ is reduced to metallic copper by gaining two electrons. The result is the effective transfer of copper from the anode source to a plate covering the cathode. The plating is most commonly a single metallic element, not an alloy. However, some alloys can be electrodeposited, notably brass and solder. Plated "alloys" are not true alloys, i.e. solid solutions, but rather discrete tiny crystals of the metals being plated. In the case of plated solder, it is sometimes deemed necessary to have a "true alloy", and the plated solder is melted to allow the Tin and Lead to combine to form a true alloy. The true alloy is more corrosion resistant than the as-plated alloy.

inflationary multiverse

Eternal inflation is a hypothetical inflationary universe model, which is itself an outgrowth or extension of the Big Bang theory. According to eternal inflation, the inflationary phase of the universe's expansion lasts forever throughout most of the universe. Because the regions expand exponentially rapidly, most of the volume of the universe at any given time is inflating. Eternal inflation, therefore, produces a hypothetically infinite multiverse, in which only an insignificant fractal volume ends inflation. It's hard to build models of inflation that don't lead to a multiverse. It's not impossible, so I think there's still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking the idea of a multiverse seriously.[21] According to Linde, "It's possible to invent models of inflation that do not allow a multiverse, but it's difficult. Every experiment that brings better credence to inflationary theory brings us much closer to hints that the multiverse is real."[21]

Electron-positron annihilation

Every particle has its antiparticle, which is an exact copy of itself with opposite charge. Sometimes antiparticles have special names, like the positron, the anti-particle of the electron. Sometimes those names are boring: the muon has the anti-muon, the neutrino has the anti-neutrino and so on. Because particles and antiparticles are equal in all aspects except for charge, they can annihilate: when they meet, they vaporize into a bunch of photons, at least two of them. A classic example of this is electron-positron annihilation, which happens when an electron bumps into a positron. Antiparticles were predicted for the first time by Paul Dirac. Dirac's suggestion was a bit weird: he thought we live in a sea of negative-energy particles and that positrons are "holes" in that sea. Nowadays we have abandoned the idea of a negative-energy sea, but the positron has stayed with us. So what is a positron exactly? One way to look at it is as an electron going back in time. This was a favorite of Richard Feynman, though other physicists may tell you that positrons are just regular, positively-charged particles and that's that. I will stick to the "going back in time" picture because it is way cooler. To understand how this work, we need to know a bit about how quantum particles work, Quantum particles come with a timer on them. You can imagine it as a tiny clock that spins as time passes. How fast this clock spins is related to the energy of the particle: a high-energy particle's clock will spin faster. In quantum mechanics we call this the "phase" of the particle and it is an abstract mathematical property, but you can imagine it as a clock and you won't be far from the truth. What happens when the energy is negative? It turns out the clock spins the opposite way. So negative energy is really related to how this particle moves in time, just like momentum is related to how it moves in space. By convention, positive momentum tells us a particle moves to the right; by convention, positive-energy particles move towards the future, whereas the other ones do so towards the past. So what will a particle travelling back in time do? Exactly the opposite as one that travels forward. If, for example, the electron is attracted to a proton, then the positron will be repelled. Which means that the positron appears, to all intents an purposes, as an exact copy of the electron with positive charge. Antiparticles do not have negative energy. If they did, when they annihilated with an electron there would be nothing left. Instead, we get photons with a combined energy of roughly twice the mass of an electron. However, is it possible that anti-particles have negative mass? The short answer is we don't know. Gravity is really hard to probe at small distances, because any other force is way, way stronger. So there is no way, for now, to measure the gravitational force between, say, an electron and a positron. If anti-particles did have mass, they would attract each other and be repelled by regular particles. The fact that anti-particles have positive energy would point to the fact that they also need to have positive mass, if you believe in Einstein's theory. Like everything in physics, we won't know until we do the experiment.

time is dependent on motion

Example: time dilation and the speed of light Yes, both motion and time are interdependent. ... If we see closely very motion notations here (Speed, Velocity, acceleration) are dependent upon change in time (they are inversely proportional to time). On basic level, this explains the concept of motion- time relation.

superluminal speeds

Faster-than-light communications and travel are the conjectural propagation of information or matter faster than the speed of light. The special theory of relativity implies that only particles with zero rest mass may travel at the speed of light.

fatty liver

Fatty liver, or steatosis, is a term that describes the buildup of fat in the liver. While it's normal to have some fat in your liver, more than 5 to 10 percent of your liver weight is fat in the case of fatty liver.n Fatty liver is a reversible condition that can be resolved with changed behaviors. It often has no symptoms and typically does not cause permanent damage. Fatty liver typically has no associated symptoms. You may experience fatigue or vague abdominal discomfort. Your liver may become slightly enlarged, and your doctor can detect this during a physical exam.

What would happen if you wore anything metallic during an MRI?

Ferromagnetic metals? - Bad times ahead. Ferromagnetic metals include your irons, steels, cobalt and nickel. Even stainless steels designed to be non-magnetic can become magnetic if manipulated inappropriately, or exposed to a high enough magnetic field. There are sad case reports of patients being injured or killed by magnetic objects brought into the room with them - often oxygen cylinders. Within a person, ferrous clips for aneurysm repair, metal shards in the eyes from welding, shrapnel from combat injuries... all can cause damage when accelerated towards the magnet. I should also mention that the fields will wipe bank cards and potentially destroy or cause damage to expensive electronics. As for pacemakers, the older devices which contain ferromagnetic materials... see above. If you wear a gold necklace during an MRI scan, you will burn your neck.

Formaldehyde

Formaldehyde (systematic name methanal) is a naturally occurring organic compound with the formula CH2O (H−CHO). It is the simplest of the aldehydes (R−CHO). The common name of this substance comes from its similarity and relation to formic acid. Formaldehyde is an important precursor to many other materials and chemical compounds. In 1996, the installed capacity for the production of formaldehyde was estimated at 8.7 million tons per year.[13] It is mainly used in the production of industrial resins, e.g., for particle board and coatings.

Cones in human eye

Humans normally have three types of cones. The first responds the most to light of longer wavelengths, peaking at about 560 nm; this type is sometimes designated L for long. The second type responds the most to light of medium-wavelength, peaking at 530 nm, and is abbreviated M for medium. The third type responds the most to short-wavelength light, peaking at 420 nm, and is designated S for short. The difference in the signals received from the three cone types allows the brain to perceive a continuous range of colors, through the opponent process of color vision. (Rod cells have a peak sensitivity at 498 nm, roughly halfway between the peak sensitivities of the S and M cones.) All of the receptors contain the protein photopsin, with variations in its conformation causing differences in the optimum wavelengths absorbed. The color yellow, for example, is perceived when the L cones are stimulated slightly more than the M cones, and the color red is perceived when the L cones are stimulated significantly more than the M cones. Similarly, blue and violet hues are perceived when the S receptor is stimulated more. Cones are most sensitive to light at wavelengths around 420 nm. However, the lens and cornea of the human eye are increasingly absorptive to shorter wavelengths, and this sets the short wavelength limit of human-visible light to approximately 380 nm, which is therefore called 'ultraviolet' light.

Tendril

In botany, a tendril is a specialized stem, leaves or petiole with a threadlike shape that is used by climbing plants for support, attachment and cellular invasion by parasitic plants, generally by twining around suitable hosts found by touch. They do not have a lamina or blade, but they can photosynthesize. a slender threadlike appendage of a climbing plant, often growing in a spiral form, that stretches out and twines around any suitable support.

Baryon acoustic oscillations

In cosmology, baryon acoustic oscillations (BAO) are fluctuations in the density of the visible baryonic matter (normal matter) of the universe, caused by acoustic density waves in the primordial plasma of the early universe. In the same way that supernovae provide a "standard candle" for astronomical observations,[1] BAO matter clustering provides a "standard ruler" for length scale in cosmology. The length of this standard ruler is given by the maximum distance the acoustic waves could travel in the primordial plasma before the plasma cooled to the point where it became neutral atoms (the epoch of recombination), which stopped the expansion of the plasma density waves, "freezing" them into place. The length of this standard ruler (≈490 million light years in today's universe[3]) can be measured by looking at the large scale structure of matter using astronomical surveys.[3] BAO measurements help cosmologists understand more about the nature of dark energy (which causes the accelerating expansion of the universe) by constraining cosmological parameters. The early universe consisted of a hot, dense plasma of electrons and baryons (protons and neutrons). Photons (light particles) traveling in this universe were essentially trapped, unable to travel for any considerable distance before interacting with the plasma via Thomson scattering.[4] As the universe expanded, the plasma cooled to below 3000 K—a low enough energy such that the electrons and protons in the plasma could combine to form neutral hydrogen atoms. This recombination happened when the universe was around 379,000 years old, or at a redshift of z = 1089.[4] Photons interact to a much lesser degree with neutral matter, and therefore at recombination the universe became transparent to photons, allowing them to decouple from the matter and free-stream through the universe.[4] Technically speaking, the mean free path of the photons became of order the size of the universe. The cosmic microwave background (CMB) radiation is light that was emitted after recombination that is only now reaching our telescopes. Therefore, looking at, for example, Wilkinson Microwave Anisotropy Probe (WMAP) data, one is basically looking back in time to see an image of the universe when it was only 379,000 years old.

universe event horizon

In cosmology, the event horizon of the observable universe is the largest comoving distance from which light emitted now can ever reach the observer in the future. ... The boundary past which events cannot ever be observed is an event horizon, and it represents the maximum extent of the particle horizon. A paradox in which you would try to reach the edge of the observable universe at the speed of light while chasing something that is out of your observable view and is also moving at the speed of light. Dark energy accelerates stuff outside of the observable universe so we are unable to see how vast it really is.

Daisy chain (electrical engineering)

In electrical and electronic engineering, a daisy chain is a wiring scheme in which multiple devices are wired together in sequence or in a ring,[1] similar to a garland of daisy flowers. Other than a full, single loop, systems which contain internal loops cannot be called daisy chains.

Flip-flop (electronics)

In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information - a bistable multivibrator. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic. Flip-flops and latches are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems. Flip-flops and latches are used as data storage elements. A flip-flop is a device which stores a single bit (binary digit) of data; one of its two states represents a "one" and the other represents a "zero". Such data storage can be used for storage of state, and such a circuit is described as sequential logic in electronics. When used in a finite-state machine, the output and next state depend not only on its current input, but also on its current state (and hence, previous inputs). It can also be used for counting of pulses, and for synchronizing variably-timed input signals to some reference timing signal.

Analog-to-digital converter

In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide an isolated measurement such as an electronic device that converts an input analog voltage or current to a digital number representing the magnitude of the voltage or current. Typically the digital output is a two's complement binary number that is proportional to the input, but there are other possibilities. An ADC converts a continuous-time and continuous-amplitude analog signal to a discrete-time and discrete-amplitude digital signal. The conversion involves quantization of the input, so it necessarily introduces a small amount of error or noise. Furthermore, instead of continuously performing the conversion, an ADC does the conversion periodically, sampling the input, limiting the allowable bandwidth of the input signal.

Antiparallel (electronics)

In electronics, two anti-parallel or inverse-parallel devices are connected in parallel but with their polarities reversed. One example is the TRIAC, which is comparable to two thyristors connected back-to-back (in other words, reverse parallel), but on a single piece of silicon. Two LEDs can be paired this way, so that each protects the other from reverse voltage. A series string of such pairs can be connected to AC or DC power, with an appropriate resistor. Some two-color LEDs are constructed this way, with the 2 dies connected anti-parallel in one chip package. With AC, the LEDs in each pair take turns emitting light, on alternate half-cycles of supply power, greatly reducing the strobing effect to below the normal flicker fusion threshold of the human eye, and making the lights brighter. On DC, polarity can be switched back and forth so as to change the color of the lights, such as in Christmas lights that can be either white or colored.

Gauge boson

In particle physics, a gauge boson is a force carrier, a bosonic particle that carries any of the fundamental interactions of nature, commonly called forces. Elementary particles, whose interactions are described by a gauge theory, interact with each other by the exchange of gauge bosons—usually as virtual particles. All known gauge bosons have a spin of 1. Therefore, all known gauge bosons are vector bosons. Gauge bosons are different from the other kinds of bosons: first, fundamental scalar bosons (the Higgs boson); second, mesons, which are composite bosons, made of quarks; third, larger composite, non-force-carrying bosons, such as certain atoms. The Standard Model of particle physics recognizes four kinds of gauge bosons: photons, which carry the electromagnetic interaction; W and Z bosons, which carry the weak interaction; and gluons, which carry the strong interaction. Isolated gluons do not occur because they are color-charged and subject to color confinement.

Vector boson

In particle physics, a vector boson is a boson with the spin equal to 1. The vector bosons regarded as elementary particles in the Standard Model are the gauge bosons, the force carriers of fundamental interactions: the photon of electromagnetism, the W and Z bosons of the weak interaction, and the gluons of the strong interaction. Some composite particles are vector bosons, for instance any vector meson (quark and antiquark). The name vector boson arises from quantum field theory. The component of such a particle's spin along any axis has the three eigenvalues −ħ, 0, and +ħ (where ħ is the reduced Planck constant), meaning that any measurement of its spin can only yield one of these values. (This is, at least, true for massive vector bosons; the situation is a bit different for massless particles such as the photon, for reasons beyond the scope of this article. See Wigner's classification.[2]) The space of spin states therefore is a discrete degree of freedom consisting of three states, the same as the number of components of a vector in three-dimensional space. Quantum superpositions of these states can be taken such that they transform under rotations just like the spatial components of a rotating vector[citation needed] (the so named 3 representation of SU(2)). If the vector boson is taken to be the quantum of a field, the field is a vector field, hence the name.

Supersymmetry

In particle physics, supersymmetry (SUSY) is a conjectured relationship between two basic classes of elementary particles: bosons, which have an integer-valued spin, and fermions, which have a half-integer spin. A type of spacetime symmetry, supersymmetry is a possible candidate for undiscovered particle physics, and seen by some physicists as an elegant solution to many current problems in particle physics if confirmed correct, which could resolve various areas where current theories are believed to be incomplete. A supersymmetrical extension to the Standard Model could resolve major hierarchy problems within gauge theory, by guaranteeing that quadratic divergences of all orders will cancel out in perturbation theory. In supersymmetry, each particle from one group would have an associated particle in the other, which is known as its superpartner, the spin of which differs by a half-integer. These superpartners would be new and undiscovered particles. For example, there would be a particle called a "selectron" (superpartner electron), a bosonic partner of the electron. In the simplest supersymmetry theories, with perfectly "unbroken" supersymmetry, each pair of superpartners would share the same mass and internal quantum numbers besides spin. Since we expect to find these "superpartners" using present-day equipment, if supersymmetry exists then it consists of a spontaneously broken symmetry allowing superpartners to differ in mass. Spontaneously broken supersymmetry could solve many mysterious problems in particle physics including the hierarchy problem. Direct confirmation would entail production of superpartners in collider experiments, such as the Large Hadron Collider (LHC). The first runs of the LHC found no previously-unknown particles other than the Higgs boson which was already suspected to exist as part of the Standard Model, and therefore no evidence for supersymmetry. Indirect methods include the search for a permanent electric dipole moment (EDM) in the known Standard Model particles, which can arise when the Standard Model particle interacts with the supersymmetric particles. The current best constraint on the electron electric dipole moment put it to be smaller than 10−28 e·cm, equivalent to a sensitivity to new physics at the TeV scale and matching that of the current best particle colliders.[8] A permanent EDM in any fundamental particle points towards time-reversal violating physics, and therefore also CP-symmetry violation via the CPT theorem. Such EDM experiments are also much more scalable than conventional particle accelerators and offer a practical alternative to detecting physics beyond the standard model as accelerator experiments become increasingly costly and complicated to maintain.

Emergence

In philosophy, systems theory, science, and art, emergence occurs when an entity is observed to have properties its parts do not have on their own. These properties or behaviors emerge only when the parts interact in a wider whole Examples of emergent properties include cities, the brain, ant colonies and complex chemical systems.??

Resonance

In physics, resonance describes the phenomena of amplification[citation needed] that occurs when the frequency of a periodically applied force is in harmonic proportion[citation needed] to a natural frequency of the system on which it acts. When an oscillating force is applied at a resonant frequency of a dynamical system, the system will oscillate at a higher amplitude than when the same force is applied at other, non-resonant frequencies. Frequencies at which the response amplitude is a relative maximum are also known as resonant frequencies or resonance frequencies of the system.[3] Small periodic forces that are near a resonant frequency of the system have the ability to produce large amplitude oscillations in the system due to the storage of vibrational energy. Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance (NMR), electron spin resonance (ESR) and resonance of quantum wave functions. Resonant systems can be used to generate vibrations of a specific frequency (e.g., musical instruments), or pick out specific frequencies from a complex vibration containing many frequencies (e.g., filters). Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a simple pendulum). However, there are some losses from cycle to cycle, called damping. When damping is small, the resonant frequency is approximately equal to the natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies.

Magnetic flux

In physics, specifically electromagnetism, the magnetic flux (often denoted Φ or ΦB) through a surface is the surface integral of the normal component of the magnetic field flux density B passing through that surface. The SI unit of magnetic flux is the weber (Wb; in derived units, volt-seconds), and the CGS unit is the maxwell. Magnetic flux is usually measured with a fluxmeter, which contains measuring coils and electronics, that evaluates the change of voltage in the measuring coils to calculate the measurement of magnetic flux. The magnetic interaction is described in terms of a vector field, where each point in space is associated with a vector that determines what force a moving charge would experience at that point (see Lorentz force).[1] Since a vector field is quite difficult to visualize at first, in elementary physics one may instead visualize this field with field lines. The magnetic flux through some surface, in this simplified picture, is proportional to the number of field lines passing through that surface (in some contexts, the flux may be defined to be precisely the number of field lines passing through that surface; although technically misleading, this distinction is not important). The magnetic flux is the net number of field lines passing through that surface; that is, the number passing through in one direction minus the number passing through in the other direction (see below for deciding in which direction the field lines carry a positive sign and in which they carry a negative sign).[2] In more advanced physics, the field line analogy is dropped and the magnetic flux is properly defined as the surface integral of the normal component of the magnetic field passing through a surface. If the magnetic field is constant, the magnetic flux passing through a surface of vector area S is

Transmon

In quantum computing, and more specifically in superconducting quantum computing, a transmon is a type of superconducting charge qubit that was designed to have reduced sensitivity to charge noise. The transmon was developed by Robert J. Schoelkopf, Michel Devoret, Steven M. Girvin and their colleagues at Yale University in 2007.[1][2] Its name is an abbreviation of the term transmission line shunted plasma oscillation qubit; one which consists of a Cooper-pair box "where the two superconductors are also capacitatively shunted in order to decrease the sensitivity to charge noise, while maintaining a sufficient anharmonicity for selective qubit control".

Compactification (physics)

In string theory, compactification is a generalization of Kaluza-Klein theory.[1] It tries to reconcile the gap between the conception of our universe based on its four observable dimensions with the ten, eleven, or twenty-six dimensions which theoretical equations lead us to suppose the universe is made with. For this purpose it is assumed the extra dimensions are "wrapped" up on themselves, or "curled" up on Calabi-Yau spaces, or on orbifolds. Models in which the compact directions support fluxes are known as flux compactifications. The coupling constant of string theory, which determines the probability of strings splitting and reconnecting, can be described by a field called a dilaton. This in turn can be described as the size of an extra (eleventh) dimension which is compact. In this way, the ten-dimensional type IIA string theory can be described as the compactification of M-theory in eleven dimensions. Furthermore, different versions of string theory are related by different compactifications in a procedure known as T-duality.

Proton-exchange membrane fuel cells (PEMFCs)

In the archetypical hydrogen-oxide proton-exchange membrane fuel cell design, a proton-conducting polymer membrane (typically nafion) contains the electrolyte solution that separates the anode and cathode sides.[25][26] This was called a solid polymer electrolyte fuel cell (SPEFC) in the early 1970s, before the proton exchange mechanism was well understood. (Notice that the synonyms polymer electrolyte membrane and 'proton exchange mechanism result in the same acronym.) On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what are commonly referred to as multi-facilitated proton membranes. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water. In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol (see: direct-methanol fuel cells and indirect methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water. When hydrogen is used, the CO2 is released when methane from natural gas is combined with steam, in a process called steam methane reforming, to produce the hydrogen. This can take place in a different location to the fuel cell, potentially allowing the hydrogen fuel cell to be used indoors—for example, in fork lifts.

Kugelblitz (astrophysics)

In theoretical physics, a kugelblitz (German: "ball lightning") is a concentration of heat, light or radiation so intense that its energy forms an event horizon and becomes self-trapped: according to general relativity and the equivalence of mass and energy, if enough radiation is aimed into a region, the concentration of energy can warp spacetime enough for the region to become a black hole, although this would be a black hole whose original mass-energy had been in the form of radiant energy rather than matter.[1] In simpler terms, a kugelblitz is a black hole formed from radiation as opposed to matter. Such a black hole would nonetheless have properties identical to one of equivalent mass and angular momentum formed in a more conventional way, in accordance with the no-hair theorem. The best-known reference to the kugelblitz idea in English is probably John Archibald Wheeler's 1955 paper "Geons",[2] which explored the idea of creating particles (or toy models of particles) from spacetime curvature, called geons. Wheeler's paper on geons also introduced the idea that lines of electric charge trapped in a wormhole throat might be used to model the properties of a charged particle-pair. Kugelblitz drives have been considered as possible future black hole starship engines.

Thermal quantum field theory

In theoretical physics, thermal quantum field theory (thermal field theory for short) or finite temperature field theory is a set of methods to calculate expectation values of physical observables of a quantum field theory at finite temperature.

how many people have stepped on the moon?

In total 12 astronauts have walked on the moon, including Armstrong and Aldrin. The other 10 who made it to the moon took part in five further Nasa launches, between 1969 and 1972. These missions were undertaken by Apollo 12, Apollo 14, Apollo 15, Apollo 16 and Apollo 17

Why do most aircraft use 400 Hz AC instead of 60hz AC?

Induction motors turn at a speed proportional to frequency, so a high frequency power supply allows more power to be obtained for the same motor volume and mass. Transformers and motors for 400 Hz are much smaller and lighter than at 50 or 60 Hz, which is an advantage in aircraft (and ships). Transformers can be made smaller because the magnetic core can be much smaller for the same power level. Thus, a United States military standard MIL-STD-704 exists for aircraft use of 400 Hz power. So why not use 400 Hz everywhere? Such high frequencies cannot be economically transmitted long distances, since the increased frequency greatly increases series impedance due to the inductance of transmission lines, making power transmission difficult. Consequently, 400 Hz power systems are usually confined to a building or vehicle.

Quark Color

Just like electrons have charge, quarks have color. Of course, they are not actual colors: those are simply wavelengths of electromagnetic radiation. We call them colors because there are three of them, so it seemed a good way to label them. So "quark color" is a funny way of talking about quark charge. There are two types of electrical charge: plus and minus. This seems natural, but only because you're used to it. Why aren't there three types? Or forty? This is the case for the strong interaction: there are three types of "charge" that we call "blue", "red" and "green". In fact, there's also the "anti" version of each, so we have six types: blue and anti-blue, red and anti-red, green and anti-green. The difference between the strong interaction and the electric force is that the strong interaction is much stronger (hence the name). Imagine for a moment that the electric force was really, really strong: would you ever see a charged object? Probably not: if the force was so large, it would be almost impossible to separate negative and positive charges, so you would only see neutral objects. Anything that got a charge would instantly be attracted to something with the opposite charge and get neutralized. This is what happens with the strong interaction: it is so strong that we never see a combination of quarks that is not "neutral." In this case, "neutral" means that the color combination has to add up to white. In fact, it is impossible to see a quark on its own: this phenomenon is called confinement. three different quarks with a different color each: red, blue and green make white, just like with actual, real-life colors. The other way is to take two quarks with opposite colors: blue and anti-blue, red and anti-red, etc. Just like opposite charges cancel out, so do opposite colors. All particles made of quarks are called "hadrons." The proton is an example of a white particle with three quarks. We call these particles "baryons." A proton has two "up" quarks and a "down" quark. Each quark has a different colour, like in the picture to the right. The neutron is made of two "down" quarks and an "up" quark and is also "white" like the proton. In fact, as far as the strong force is concerned, the proton and neutron are pretty much the same particle. The other type of white particle is called a "meson". Mesons are made of a quark and an anti-quark, so that the anti-quark has an anti-color. For example, the π+ is made of an up and an anti-down quark. If the up is blue, then the anti-down will be anti-bue and so on. There are many different mesons which typically do not last much.

Here is an amino acid. The name comes from the fact that this molecule has an amino group (in red) and an acid group (in blue). Anything that has both is an amino acid. In between the "amino" and the "acid" groups are some number of carbon atoms (C) bearing hydrogen atoms (H). The "R" in the structure means that there can also be attached some other random groups, but no matter what that R is, you've still got an amino acid. An interesting aspect of most amino acids is that they exist in left and right handed forms, and this is called chirality. Life on Earth is made of left handed amino acids, and this may be a result of how these molecules formed in space.

Key molecules of life—especially the common 20 amino acids comprising the structure of all proteins—are almost exclusively of the left-handed variety, since light moving through them rotates left. By contrast, the nucleotide bases and sugars that comprise RNA and DNA tend to be right-handed. There are two varieties of amino acids, known as left- or right-handed (referred to as S and R). They are mirror images of each other and both exist in nature, as shown for other substances by Louis Pasteur. Biochemical processes in living organisms use left- and right-handed or 'chiral' receptors that template differently with these two forms. The olfactory receptors in our noses, for example, easily distinguish the distinct smells of the otherwise identical molecules (called carvones) of spearmint (R-carvone) and caraway (S-carvone). An important and outstanding mystery is why nature chooses only exclusively left-handed amino acids in forming proteins.

Cherenkov radiation

Light emitted by fast-moving charged particles traversing a dense transparent medium faster than the speed of light in that medium. Cherenkov radiation is electromagnetic radiation emitted when a charged particle passes through a dielectric medium at a speed greater than the phase velocity of light in that medium. The characteristic blue glow of an underwater nuclear reactor is a completely normal phenomenon due to Cherenkov radiation. image is of a nuclear reactor

Magnetic ink character recognition

Magnetic ink character recognition code, known in short as MICR code, is a character recognition technology used mainly by the banking industry to streamline the processing and clearance of cheques and other documents. MICR encoding, called the MICR line, is at the bottom of cheques and other vouchers and typically includes the document-type indicator, bank code, bank account number, cheque number, cheque amount (usually added after a cheque is presented for payment), and a control indicator. The format for the bank code and bank account number is country-specific. The technology allows MICR readers to scan and read the information directly into a data-collection device. Unlike barcode and similar technologies, MICR characters can be read easily by humans. MICR encoded documents can be processed much faster and more accurately than conventional OCR encoded documents.

Mantis shrimp

Mantis shrimp live in burrows where they spend the majority of their time.[9] The two different categories of mantis shrimp - spearing and smashing - favor different locations for burrowing.[9] The spearing species build their habitat in soft sediments and the smashing species make burrows in hard substrata or coral cavities.[9] These two habitats are crucial for their ecology since they use burrows as sites for retreat and as locations for consuming their prey.[9] Burrows and coral cavities are also used as sites for mating and for keeping their eggs safe.[9]Stomatopod body size undergoes periodic growth which necessitates finding a new cavity or burrow that will fit the animal's new diameter.[9] Some spearing species can modify their pre-established habitat if the burrow is made of silt or mud, which can be expanded.[9] The mantis shrimp's second pair of thoracic appendages has been adapted for powerful close-range combat with high modifications. The appendage differences divide mantis shrimp into two main types: those that hunt by impaling their prey with spear-like structures and those that smash prey with a powerful blow from a heavily mineralised club-like appendage. A considerable amount of damage can be inflicted after impact with these robust, hammer-like claws. This club is further divided into three subregions: the impact region, the periodic region, and the striated region. Mantis shrimp are commonly separated into two distinct groups determined by the type of claws they possess: Smashers possess a much more developed club and a more rudimentary spear (which is nevertheless quite sharp and still used in fights between their own kind); the club is used to bludgeon and smash their meals apart. The inner aspect of the terminal portion of the appendage can also possess a sharp edge, used to cut prey while the mantis shrimp swims. Spearers are armed with spiny appendages topped with barbed tips, used to stab and snag prey. Both types strike by rapidly unfolding and swinging their raptorial claws at the prey, and can inflict serious damage on victims significantly greater in size than themselves. In smashers, these two weapons are employed with blinding quickness, with an acceleration of 10,400 g (102,000 m/s2 or 335,000 ft/s2) and speeds of 23 m/s (83 km/h; 51 mph) from a standing start.[10] Because they strike so rapidly, they generate vapor-filled bubbles in the water between the appendage and the striking surface—known as cavitation bubbles.[10] The collapse of these cavitation bubbles produces measurable forces on their prey in addition to the instantaneous forces of 1,500 newtons that are caused by the impact of the appendage against the striking surface, which means that the prey is hit twice by a single strike; first by the claw and then by the collapsing cavitation bubbles that immediately follow.[11] Even if the initial strike misses the prey, the resulting shock wave can be enough to stun or kill. The impact can also produce sonoluminescence from the collapsing bubble. This will produce a very small amount of light within the collapsing bubble, although the light is too weak and short-lived to be detected without advanced scientific equipment. The light emission probably has no biological significance, but is rather a side effect of the rapid snapping motion. Pistol shrimp produce this effect in a very similar manner. Mantis shrimp can perceive wavelengths of light ranging from deep ultraviolet (UVB) to far-red (300 to 720 nm) and polarized light. Each compound eye is made up of up tens of thousands of ommatidia, clusters of photoreceptor cells. Some species have at least 16 photoreceptor types, which are divided into four classes (their spectral sensitivity is further tuned by colour filters in the retinas), 12 for colour analysis in the different wavelengths (including six which are sensitive to ultraviolet light[21][25]) and four for analysing polarised light.

Mismatch repair

Many errors are corrected by proofreading, but a few slip through. Mismatch repair happens right after new DNA has been made, and its job is to remove and replace mis-paired bases (ones that were not fixed during proofreading). Mismatch repair can also detect and correct small insertions and deletions that happen when the polymerases "slips," losing its footing on the template. How does mismatch repair work? First, a protein complex (group of proteins) recognizes and binds to the mispaired base. A second complex cuts the DNA near the mismatch, and more enzymes chop out the incorrect nucleotide and a surrounding patch of DNA. A DNA polymerase then replaces the missing section with correct nucleotides, and an enzyme called a DNA ligase seals the gap. One thing you may wonder is how the proteins involved in DNA repair can tell "who's right" during mismatch repair. That is, when two bases are mispaired (like the G and T in the drawing above), which of the two should be removed and replaced? In bacteria, original and newly made strands of DNA can be told apart by a feature called methylation state. An old DNA strand will have methyl (-CH3) groups attached to some of its bases, while a newly made DNA strand will not yet have gotten its methyl group. In eukaryotes, the processes that allow the original strand to be identified in mismatch repair involve recognition of nicks (single-stranded breaks) that are found only in the newly synthesized DNA.

Microfluidics

Microfluidics refers to the behaviour, precise control, and manipulation of fluids that are geometrically constrained to a small scale (typically sub-millimeter) at which capillary penetration governs mass transport. It is a multidisciplinary field that involves engineering, physics, chemistry, biochemistry, nanotechnology, and biotechnology. It has practical applications in the design of systems that process low volumes of fluids to achieve multiplexing, automation, and high-throughput screening. Microfluidics emerged in the beginning of the 1980s and is used in the development of inkjet printheads, DNA chips, lab-on-a-chip technology, micro-propulsion, and micro-thermal technologies. The behaviour of fluids at the microscale can differ from "macrofluidic" behaviour in that factors such as surface tension, energy dissipation, and fluidic resistance start to dominate the system. Microfluidics studies how these behaviours change, and how they can be worked around, or exploited for new uses. At small scales (channel size of around 100 nanometers to 500 micrometers) some interesting and sometimes unintuitive properties appear. In particular, the Reynolds number (which compares the effect of the momentum of a fluid to the effect of viscosity) can become very low. A key consequence is co-flowing fluids do not necessarily mix in the traditional sense, as flow becomes laminar rather than turbulent; molecular transport between them must often be through diffusion.[6] Microfluidic structures include micropneumatic systems, i.e. microsystems for the handling of off-chip fluids (liquid pumps, gas valves, etc.), and microfluidic structures for the on-chip handling of nanoliter (nl) and picoliter (pl) volumes.[9] To date, the most successful commercial application of microfluidics is the inkjet printhead.[10] Additionally, microfluidic manufacturing advances mean that makers can produce the devices in low-cost plastics[11] and automatically verify part quality. Advances in microfluidics technology are revolutionizing molecular biology procedures for enzymatic analysis (e.g., glucose and lactate assays), DNA analysis (e.g., polymerase chain reaction and high-throughput sequencing), proteomics, and in chemical synthesis.[13][14] The basic idea of microfluidic biochips is to integrate assay operations such as detection, as well as sample pre-treatment and sample preparation on one chip.[15][16]

Mold

Molds are a large and taxonomically diverse number of fungal species in which the growth of hyphae results in discoloration and a fuzzy appearance, especially on food.[3] The network of these tubular branching hyphae, called a mycelium, is considered a single organism. The hyphae are generally transparent, so the mycelium appears like very fine, fluffy white threads over the surface. Cross-walls (septa) may delimit connected compartments along the hyphae, each containing one or multiple, genetically identical nuclei. The dusty texture of many molds is caused by profuse production of asexual spores (conidia) formed by differentiation at the ends of hyphae. The mode of formation and shape of these spores is traditionally used to classify molds.[4] Many of these spores are colored, making the fungus much more obvious to the human eye at this stage in its life-cycle. Molds are considered to be microbes and do not form a specific taxonomic or phylogenetic grouping, but can be found in the divisions Zygomycota and Ascomycota. In the past, most molds were classified within the Deuteromycota. Molds cause biodegradation of natural materials, which can be unwanted when it becomes food spoilage or damage to property. They also play important roles in biotechnology and food science in the production of various foods, beverages, antibiotics, pharmaceuticals and enzymes. Some diseases of animals and humans can be caused by certain molds: disease may result from allergic sensitivity to mold spores, from growth of pathogenic molds within the body, or from the effects of ingested or inhaled toxic compounds (mycotoxins) produced by molds. There are thousands of known species of molds, which have diverse life-styles including saprotrophs, mesophiles, psychrophiles and thermophiles and a very few opportunistic pathogens of humans.[6] They all require moisture for growth and some live in aquatic environments. Like all fungi, molds derive energy not through photosynthesis but from the organic matter on which they live, utilising heterotrophy. Typically, molds secrete hydrolytic enzymes, mainly from the hyphal tips. These enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can be absorbed by the hyphae. In this way, molds play a major role in causing decomposition of organic material, enabling the recycling of nutrients throughout ecosystems. Many molds also synthesise mycotoxins and siderophores which, together with lytic enzymes, inhibit the growth of competing microorganisms. Molds can also grow on stored food for animals and humans, making the food unpalatable or toxic and are thus a major source of food losses and illness.[7] Many strategies for food preservation (salting, pickling, jams, bottling, freezing, drying) are to prevent or slow mold growth as well as growth of other microbes. Molds reproduce by producing large numbers of small spores,[6] which may contain a single nucleus or be multinucleate. Mold spores can be asexual (the products of mitosis) or sexual (the products of meiosis); many species can produce both types. Some molds produce small, hydrophobic spores that are adapted for wind dispersal and may remain airborne for long periods; in some the cell walls are darkly pigmented, providing resistance to damage by ultraviolet radiation. Other mold spores have slimy sheaths and are more suited to water dispersal. Mold spores are often spherical or ovoid single cells, but can be multicellular and variously shaped. Spores may cling to clothing or fur; some are able to survive extremes of temperature and pressure.

Advantage of using AC generators in cars instead of DC generators

Most cars use an AC generator then convert its voltage to DC via a bridge diode rectifier to charge the 12v battery. Why wouldn't a DC dynamo be used instead? No, it's not for efficiency reasons. DC generators typically have commutators, i.e. contacts with brushes that reverse the polarity of the voltage at the generator clamps every half rotation. In essence, DC generators are just AC generators that have a "mechanical" rectifier. You can build generators without any electrical contacts between moving parts, but you cannot build commutators without those. Since such contacts are very likely to fail under constant use, in dirty and vibrating environments, it's very desirable not to use them in cars. I'd also go as far as to say that unless you build a very expensive one, the contact resistance might be higher than what you lose over a bridge rectifier.

After given several talks on NN's, I always have a skeptic that wants a real measure of how well the model is. How do you know the model is truly accurate?

Neural networks are essentially a black box, especially big ones. You could know even how it is designed and how it is training, but you really do not know how it is working in the end. In my work lots of people want to understand the model instead of using "black box" models. This is the reason why companies choose to use linear regressions and polynomial models instead of using stronger machine learning algorithms, like LightGBM and Neural Networks. I never found a true answer to this question. Some engineers are taught that you cannot use models that you cannot understand. Therefore every model that is a "black box" is not usable for them. This means that most of machine learning models are magic and heresy for them. Though take this with a grain of salt, this is my subjective experience. Sometimes as the time passes these people are more willing to use data science methods because it becomes mainstream. They start to trust the methods, because others use them. The situation is different on the higher level. For high-tier managers it matters less how to interpret the model, but more what results it could give you. They are more willing to try, especially if there is a hype of something, like "artificial intelligence", "data science". As a result, I could only give you an advice to find some good support higher in the hierarchy of the company. Someone who believes in data science more and who has more power in the company. In data science community the performance of the model on the test dataset is one of the most important things people look at. Just look at the competitions on kaggle.com. They are extremely focused on test dataset and the performance of these models is really good. The only problem with performance on the test dataset is that it depends on the data in the test dataset. If in real life you will have completely different data that will be outside of the bounds of the test dataset, then the test dataset will not be able to give a good approximation of the performance of the model in real life.

300 Trillion Neutrinos Walk into a Bar

Neutrinos are a type of fermion which has no charge and is extremely light, so much so that most physicists believed it had no mass until quite recently. The thing about neutrinos is that they barely interact with anything: billions go through you every minute without you even noticing. The story of how we found out about neutrinos is great for showing how discoveries are made in science. It all started by looking at a particular type of radioactive decay called beta decay, in which a nucleus gives off an electron. Scientists were expecting to see electrons that were always shot with the same energy, as they had seen in many other decay processes. However, they found that the electrons had a range of energies. Some energy was missing. From there, somebody guessed that the energy had to be carried by another particle, since it couldn't have just vanished. The particle couldn't have any charge, because otherwise the total charge would not add up. And it had to be very light because, if it weren't, it would have to carry a huge chunk of the energy, but there were times when the electron had almost all of it. So we have a small, neutral particle: the neutrino. This chain of reasoning may seem like a bunch of patches on top of patches. Our theory does not predict the right outcome? Add a particle! Wait, but then how does the electron take most of the energy sometimes? It must be light! And why haven't we seen it yet? It has no charge! However, this is how science works: we look for a plausible explanation, which we refine using the data at our disposal. We make new predictions and see if they fit. If not, we throw the new idea away. In some cases, our idea survives and we have a new theory or a new particle, in this case the neutrino. To be precise, the neutrinos from the beta decay are actually antineutrinos: particles which, when set in contact with a neutrino, will annihilate into photons. However, since the neutrinos have no charge, it is almost identical to its anti-particle.

Why Did the Electron Cross the Road?

One of the most surprising properties of elementary particles is that they can be in several places at the same time, at least until they are observed. This happens because particles behave also as waves and, just like those, they can spread, diffract and interfere. A typical case of this is an electron going through a double slit, like in the picture below. However, the electrons are clearly particles: each electron crashes at a particular location, not everywhere on the screen. Even so, the pattern that they create as a whole is the same as that of two waves interfering. It is almost as if what behaved as a wave was the probability of finding the electron there. This is, in fact, what happens. Before being observed, electrons behave as something called a "probability wave": it is like a regular wave, but cannot be observed. When you observe the electron, it stops behaving like a wave and starts behaving like a particle, taking up a definite position just like a regular particle. However, until you observe it, the electron or, at least, its associated probability wave, can be in several places at once. It is possible to take this experiment even further. For example, we could place an electron detector at the slits to find out through which one it really went. This should clear out the confusion and get rid of all that nonsense about the electron going through both slits. If you do this, you will find that the electron does choose one slit instead of going through both: however, the interference pattern will also disappear! Since you observed the electron, it stopped behaving as a wave and started doing what you would expect a bullet to do. So are electrons particles? Are they waves? I find the question doesn't really make sense. We humans are used to seeing rocks and water waves, but that's not what the universe is made of. This is not the "real" stuff. The real stuff is electrons, which are both waves and particles. They are wavicles. It may seem bizarre to use because we have nothing familiar to compare it with. But nature couldn't care less about what we find familiar. Nature does whatever it wants and it is up to us to get rid of our prejudices about reality and listen to what she has to say.

the bee orchid (Ophrys apifera)

Ophrys apifera, known in Europe as the bee orchid, is a perennial herbaceous plant of the family Orchidaceae. It is remarkable as an example of sexually-deceptive pollination and floral mimicry as well as of a highly-selective and highly evolved plant-pollinator relationship. The Bee orchid is a sneaky mimic - the flower's velvety lip looks like a female bee. Males fly in to try to mate with it and end up pollinating the flower. Sadly, the right bee species doesn't live here, so this orchid is self-pollinated in the UK.

ormosia arborea

Ormosia is a genus of legumes (family Fabaceae). The more than 100 living species, mostly trees or large shrubs, are distributed throughout the tropical regions of the world, some extending into temperate zones, especially in East Asia. A few species are threatened by habitat destruction, while the Hainan Ormosia (Ormosia howii) is probably extinct already.

helicity

Physicists call the property of the spin pointing in the same way as the movement "helicity." The problem with helicity is that it depends on who's looking at the particle, so it's not great for distinguishing between left- and right-handed electrons. The property that allows us to distinguish between those is called "chirality." The beauty of chirality is that it does not depend on who's looking; the disadvantage is that there's no easy way to show it in a picture. However, imagining the left- and right-handed particles as mirror images of one another is a good enough analogy. So why is it important to distinguish between left- and right-handed particles? It turns out there are many good reasons. For starters, some forces will only interact with right-handed particles, a bit like teachers in the 1950s. This creates a noticeable difference between the mirror universe and ours and is why the W+ boson in the comic is ignoring the poor left-handed electron. So are actual electrons right- or left-handed? It turns out they are neither. In fact, electrons are a combination of two particles: a right-handed and a left-handed electron. Right- and left-handed electrons are massless: they weigh nothing. Because of this, they travel at the speed of light, just like photons. But real electrons do have mass and do not travel at the speed of light, so what's going on? Right- and left-handed electrons are massless and travel at the speed of light. In fact, they travel at the speed of light because they are massless. But we can turn this reasoning around: they are massless because they travel at the speed of light, they are massless. Only massless things travel at the speed of light. So the reasoning doesn't go like this: Massless → Speed of light Or this: Speed of light → Massless But rather this: Speed of light ↔ Massless In a similar way, we can deduce that, if a particle does not travel at the speed of light, it has mass: Less than the speed of light ↔ Mass This is how the electron acquires mass. A right-handed electron travels at the speed of light and then bumps into a Higgs boson, which turns it into a left-handed electron travelling at an angle, at the speed of light. Then the left-handed electron bumps into another Higgs boson and turns into a right-handed electron, and so on. The result is a random zig-zag motion that, looked at from large enough distances, appears to be a negatively-charged particle travelling at less than the speed of light and therefore with mass. It also implies that the particle is not right- or left-handed but a combination of both. Summarizing: handed electrons have no mass, but "real" electrons do because they are a combination of left- and right-handed electrons. This combination can only happen because of the Higgs boson. That's why we say the Higgs boson gives particles mass.

Piezoelectricity

Piezoelectricity is the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, DNA and various proteins)[1] in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure and latent heat. The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry.[5] The piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical force) also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an applied electrical field. For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their static structure is deformed by about 0.1% of the original dimension. Conversely, those same crystals will change about 0.1% of their static dimension when an external electric field is applied to the material. The inverse piezoelectric effect is used in the production of ultrasonic sound waves. The nature of the piezoelectric effect is closely related to the occurrence of electric dipole moments in solids. The latter may either be induced for ions on crystal lattice sites with asymmetric charge surroundings (as in BaTiO3 and PZTs) or may directly be carried by molecular groups (as in cane sugar). The dipole density or polarization (dimensionality [C·m/m3] ) may easily be calculated for crystals by summing up the dipole moments per volume of the crystallographic unit cell. As every dipole is a vector, the dipole density P is a vector field. Dipoles near each other tend to be aligned in regions called Weiss domains. The domains are usually randomly oriented, but can be aligned using the process of poling (not the same as magnetic poling), a process by which a strong electric field is applied across the material, usually at elevated temperatures. Not all piezoelectric materials can be poled. Of decisive importance for the piezoelectric effect is the change of polarization P when applying a mechanical stress. This might either be caused by a reconfiguration of the dipole-inducing surrounding or by re-orientation of molecular dipole moments under the influence of the external stress. Piezoelectricity may then manifest in a variation of the polarization strength, its direction or both, with the details depending on: 1. the orientation of P within the crystal; 2. crystal symmetry; and 3. the applied mechanical stress. The change in P appears as a variation of surface charge density upon the crystal faces, i.e. as a variation of the electric field extending between the faces caused by a change in dipole density in the bulk. For example, a 1 cm3 cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 V.[17] Piezoelectric materials also show the opposite effect, called the converse piezoelectric effect, where the application of an electrical field creates mechanical deformation in the crystal. Piezoelectricity is exploited in a number of useful applications, such as the production and detection of sound, piezoelectric inkjet printing, generation of high voltages, electronic frequency generation, microbalances, to drive an ultrasonic nozzle, and ultrafine focusing of optical assemblies. It forms the basis for a number of scientific instrumental techniques with atomic resolution, the scanning probe microscopies, such as STM, AFM, MTA, and SNOM. It also finds everyday uses such as acting as the ignition source for cigarette lighters, push-start propane barbecues, used as the time reference source in quartz watches, as well as in amplification pickups for some guitars and triggers in most modern electronic drums.

Pseudocopulation

Pseudocopulation describes behaviors similar to copulation that serve a reproductive function for one or both participants but do not involve actual sexual union between the individuals. It is most generally applied to a pollinator attempting to copulate with a flower.

Pulse-width modulation

Pulse width modulation (PWM), or pulse-duration modulation (PDM), is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts. The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer the switch is on compared to the off periods, the higher the total power supplied to the load. Along with MPPT maximum power point tracking, it is one of the primary methods of reducing the output of solar panels to that which can be utilized by a battery.[1] PWM is particularly suited for running inertial loads such as motors, which are not as easily affected by this discrete switching, because they have inertia to react slow. The PWM switching frequency has to be high enough not to affect the load, which is to say that the resultant waveform perceived by the load must be as smooth as possible. The rate (or frequency) at which the power supply must switch can vary greatly depending on load and application. For example, switching has to be done several times a minute in an electric stove; 120 Hz in a lamp dimmer; between a few kilohertz (kHz) and tens of kHz for a motor drive; and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies. The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on and power is being transferred to the load, there is almost no voltage drop across the switch. Power loss, being the product of voltage and current, is thus in both cases close to zero. PWM also works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle. PWM has also been used in certain communication systems where its duty cycle has been used to convey information over a communications channel. The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on. When a digital signal is on half of the time and off the other half of the time, the digital signal has a duty cycle of 50% and resembles a "square" wave. When a digital signal spends more time in the on state than the off state, it has a duty cycle of >50%. When a digital signal spends more time in the off state than the on state, it has a duty cycle of <50%. Here is a pictorial that illustrates these three scenarios:

Quadrupole magnet

Quadrupole magnets, abbreviated as Q-magnets, consist of groups of four magnets laid out so that in the planar multipole expansion of the field, the dipole terms cancel and where the lowest significant terms in the field equations are quadrupole. Quadrupole magnets are useful as they create a magnetic field whose magnitude grows rapidly with the radial distance from its longitudinal axis. This is used in particle beam focusing. The simplest magnetic quadrupole is two identical bar magnets parallel to each other such that the north pole of one is next to the south of the other and vice versa. Such a configuration will have no dipole moment, and its field will decrease at large distances faster than that of a dipole. A stronger version with very little external field involves using a k=3 Halbach cylinder. In some designs of quadrupoles using electromagnets, there are four steel pole tips: two opposing magnetic north poles and two opposing magnetic south poles. The steel is magnetized by a large electric current in the coils of tubing wrapped around the poles. Another design is a Helmholtz coil layout but with the current in one of the coils reversed.

Quantum tunnelling

Quantum tunnelling or tunneling is the quantum mechanical phenomenon where a subatomic particle passes through a potential barrier. Quantum tunnelling is not predicted by the laws of classical mechanics where surmounting a potential barrier requires enough potential energy. good ole' superposition in action bell curves be boolin' doe

Rule 34

Rule 34 is an Internet meme and slang that states that, as a rule, Internet pornography exists concerning every conceivable topic. The concept is commonly depicted as fan art of normally non-erotic subjects engaging in sexual behavior.

Saffron

Saffron is a spice derived from the flower of Crocus sativus, commonly known as the "saffron crocus". The vivid crimson stigma and styles, called threads, are collected and dried for use mainly as a seasoning and colouring agent in food. Saffron has long been the world's most costly spice by weight.

Electromechanical timers

Short-period bimetallic electromechanical timers use a thermal mechanism, with a metal finger made of strips of two metals with different rates of thermal expansion sandwiched together; steel and bronze are common. An electric current flowing through this finger causes heating of the metals, one side expands less than the other, and an electrical contact on the end of the finger moves away from or towards an electrical switch contact. The most common use of this type is in the "flasher" units that flash turn signals in automobiles, and sometimes in Christmas lights. This is a non-electronic type of multivibrator. An electromechanical cam timer uses a small synchronous AC motor turning a cam against a comb of switch contacts. The AC motor is turned at an accurate rate by the alternating current, which power companies carefully regulate. Gears drive a shaft at the desired rate, and turn the cam. The most common application of this timer now is in washers, driers and dishwashers. This type of timer often has a friction clutch between the gear train and the cam, so that the cam can be turned to reset the time. Electromechanical timers survive in these applications because mechanical switch contacts may still be less expensive than the semiconductor devices needed to control powerful lights, motors and heaters. In the past, these electromechanical timers were often combined with electrical relays to create electro-mechanical controllers. Electromechanical timers reached a high state of development in the 1950s and 1960s because of their extensive use in aerospace and weapons systems. Programmable electromechanical timers controlled launch sequence events in early rockets and ballistic missiles. As digital electronics has progressed and dropped in price, electronic timers have become more advantageous.

why can't you drink glacier water?

So the bottom line is that just because a water source was previously frozen does not mean it is inherently safe to drink. In fact, Loso has found snow and ice are capable of preserving poop and fecal bacteria "indefinitely," which means that you need to consider the provenance of your melt water carefully.

solvent finance

Solvency, in finance or business, is the degree to which the current assets of an individual or entity exceed the current liabilities of that individual or entity. Solvency can also be described as the ability of a corporation to meet its long-term fixed expenses and to accomplish long-term expansion and growth.

science behind fluorescent dyes

Some of the molecules in these fluorescent dyes are excited by UV energy, and afterwards, as the energy level within these molecules decreases, they release part of that extra energy as visible light. So fluorescent dyes turn invisible energy into visible light How does fluorescence work? Electromagnetic energy from a laser set at the correct wavelength will provide the right amount of energy to an electron in the fluorescent dye molecule. ... Finally, this energy is released in the form of a photon (fluorescence) and the electron moves back down to the lower energy level.

Sucrose

Sucrose is common sugar. It is a disaccharide, a molecule composed of two monosaccharides: glucose and fructose. Sucrose is produced naturally in plants, from which table sugar is refined. It has the molecular formula C12H22O11. For human consumption, sucrose is extracted and refined from either sugarcane or sugar beet. Sugar mills - typically located in tropical regions near where sugarcane is grown - crush the cane and produce raw sugar which is shipped to other factories for refining into pure sucrose. Sugar beet factories are located in temperate climates where the beet is grown, and process the beets directly into refined sugar. The sugar refining process involves washing the raw sugar crystals before dissolving them into a sugar syrup which is filtered and then passed over carbon to remove any residual colour. The sugar syrup is then concentrated by boiling under a vacuum and crystallized as the final purification process to produce crystals of pure sucrose that are clear, odorless, and sweet. Sugar is often an added ingredient in food production and food recipes. About 185 million tonnes of sugar were produced worldwide in 2017.[5]

Superstring theory

Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modeling them as vibrations of tiny supersymmetric strings. 'Superstring theory' is a shorthand for supersymmetric string theory because unlike bosonic string theory, it is the version of string theory that accounts for both fermions and bosons and incorporates supersymmetry to model gravity. Since the second superstring revolution, the five superstring theories are regarded as different limits of a single theory tentatively called M-theory. The deepest problem in theoretical physics is harmonizing the theory of general relativity, which describes gravitation and applies to large-scale structures (stars, galaxies, super clusters), with quantum mechanics, which describes the other three fundamental forces acting on the atomic scale. The development of a quantum field theory of a force invariably results in infinite possibilities. Physicists developed the technique of renormalization to eliminate these infinities; this technique works for three of the four fundamental forces—electromagnetic, strong nuclear and weak nuclear forces—but not for gravity. Development of quantum theory of gravity therefore requires different means than those used for the other forces.[1] According to the theory, the fundamental constituents of reality are strings of the Planck length (about 10^−33 cm) that vibrate at resonant frequencies. Every string, in theory, has a unique resonance, or harmonic. Different harmonics determine different fundamental particles. The tension in a string is on the order of the Planck force (10^44 newtons). The graviton (the proposed messenger particle of the gravitational force), for example, is predicted by the theory to be a string with wave amplitude zero.

Synchronverter

Synchronverters or virtual synchronous generators[1][2] are inverters which mimic synchronous generators[3] to provide "synthetic inertia" for ancillary services in electric power systems.[4] Inertia is a property of standard synchronous generators associated with the rotating physical mass of the system spinning at a frequency proportional to the electricity being generated. Inertia has implications towards grid stability as work is required to alter the kinetic energy the spinning physical mass and therefore opposes changes in grid frequency. Inverter based generation inherently lacks this property as the waveform is being created artificially via power electronics.

dark matter bullet cluster

The Bullet Cluster (1E 0657-56) consists of two colliding clusters of galaxies. Gravitational lensing studies of the Bullet Cluster are claimed to provide the best evidence to date for the existence of dark matter. The major components of the cluster pair—stars, gas and the putative dark matter—behave differently during collision, allowing them to be studied separately. The stars of the galaxies, observable in visible light, were not greatly affected by the collision, and most passed right through, gravitationally slowed but not otherwise altered. The hot gas of the two colliding components, seen in X-rays, represents most of the baryonic, i.e. ordinary, matter in the cluster pair. The gases interact electromagnetically, causing the gases of both clusters to slow much more than the stars. The third component, the dark matter, was detected indirectly by the gravitational lensing of background objects. In theories without dark matter, such as Modified Newtonian dynamics (MOND), the lensing would be expected to follow the baryonic matter; i.e. the X-ray gas. However, the lensing is strongest in two separated regions near (possibly coincident with) the visible galaxies. This provides support for the idea that most of the mass in the cluster pair is in the form of two regions of dark matter, which bypassed the gas regions during the collision. This accords with predictions of dark matter as only weakly interacting, other than via the gravitational force.

how we domesticated the carrot

The Carrot has a somewhat complex and unclear history, surrounded by doubt and enigma and it is difficult to pin down when domestication took place. The wide distribution of Wild Carrot (Daucus carota, carota), the absence of carrot remains in archaeological excavations and lack of documentary evidence do not enable us to determine precisely where and when carrot domestication was initiated. Over thousands of years it moved from a small, tough, bitter and spindly root to a fleshy, sweet, pigmented unbranched edible root. It transformed from its seeds being used as a medicine or aphrodisiac to the root being eaten in many different dishes. Even before the introduction of domesticated carrots, wild plants were grown in gardens as medicinal plants. Unravelling its progress through the ages is complex and inconclusive, but nevertheless a fascinating journey through time and the history of mankind. It is considered that Carrots were originally purple with a thin root, then a mutant occurred which removed the purple pigmentation resulting in a new race of yellow carrots. Modern genetic evidence proves that orange carrots are derived from yellow varieties. The carotenoids that give carrots their vibrant hue are also what make them healthy for humans: Those chemicals are sources of vitamin A. Recently, Simon and 20 other scientists scraped together the vegetable's genome: a string of DNA more than 32,000 genes long. Their results, published in the journal Nature Genetics, help explain how carrots evolved from their wild white form to the one we know today. From that long string of DNA, Simon was able to tease out a gene thought to be responsible for making carrots orange. It's still just a candidate, he cautioned. The gene in question — DCAR_032551, or the "Y gene" for short — is found in other plants. It causes red, orange and yellow pigments to accumulate in leaves, where they help with photosynthesis. But sometime about 1,100 years ago, farmers in what is now Afghanistan took advantage of a mutation in the Y gene that put it to work down in their carrots' roots. In the process of domesticating the white, wild carrot, they turned it yellow. Six hundred years later in Europe, cultivation took another turn, and carrots deepened in hue from yellow to dark orange. "There's no good biological reason for carrots to be orange except one," he said. "And it's that people have been diddling around with carrots for 1,000 years." Carrots are orange because they absorb certain wavelengths of light more efficiently than others. Beta-carotene is the main pigment and is mainly absorbs in the 400-500nm region of the visible spectrum with a peak absorption at about 450nm. Carotenoids are one of the most important groups of natural pigments. They cause the yellow/orange colours of many fruit and vegetables. Though beta-carotene is most abundant in carrots it is also found in pumpkins, apricots and nectarines. Dark green vegetables such as spinach and broccoli are another good source. http://www.carrotmuseum.co.uk/history5.html

Grievance Officer

The Grievance Officer is the link between individual members and the Association Grievance Committee. In matters arising from the Collective Agreement, he/she is also the link between the individual and the university adm inistrators.

Laser Interferometer Space Antenna (LISA)

The Laser Interferometer Space Antenna (LISA) is a mission led by the European Space Agency to detect and accurately measure gravitational waves[2]—tiny ripples in the fabric of space-time—from astronomical sources.[3] LISA would be the first dedicated space-based gravitational wave detector. It aims to measure gravitational waves directly by using laser interferometry. The LISA concept has a constellation of three spacecraft arranged in an equilateral triangle with sides 2.5 million km long, flying along an Earth-like heliocentric orbit. The distance between the satellites is precisely monitored to detect a passing gravitational wave. LIGO in space

Sloan Digital Sky Survey

The Sloan Digital Sky Survey has created the most detailed three-dimensional maps of the Universe ever made, with deep multi-color images of one third of the sky, and spectra for more than three million astronomical objects. Learn and explore all phases and surveys—past, present, and future—of the SDSS. The Sloan Digital Sky Survey (SDSS) is one of the most extensive and ambitious astronomical surveys undertaken by modern astronomers. In its first two stages, lasting from 2000 to 2008, SDSS mapped almost 30 percent of the northern sky using a dedicated 2.5 meter telescope at the Apache Point Observatory in New Mexico. The survey used a 120-megapixel camera to image over 350 million objects, and collected the spectra of hundreds of thousands of galaxies, quasars, and stars. Notable SDSS discoveries include some of the oldest known quasars and stars moving fast enough to escape from our galaxy. SDSS data has also been used to map the distribution of dark matter around galaxies through observations of weak gravitational lensing and to study the evolution of structure in the universe through observations of how both galaxies and quasars are distributed at different redshifts. The third phase of the survey is scheduled to end in 2014, and is expected to yield many exciting scientific discoveries.

Taser

The Taser fires two small dart-like electrodes, which stay connected to the main unit by conductive wire as they are propelled by small compressed nitrogen charges.[16][17] The cartridge contains a pair of electrodes and propellant for a single shot (or three shots in the X3 model) and is replaced after each use. Stun guns generate a high-voltage, low-amperage electrical charge. In simple terms, this means that the charge has a lot of pressure behind it, but not that much intensity. When you press the stun gun against someone and hold the trigger, the charge passes into that person's body. Conventional stun guns have a fairly simple design. They are about the size of a flashlight, and they work on ordinary 9-volt batteries. ... The circuitry includes multiple transformers, components that boost the voltage in the circuit, typically to between 20,000 and 150,000 volts, and reduce the amperage.

Electric dipole moment

The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The SI units for electric dipole moment are coulomb-meter (C⋅m); however, a commonly used unit in atomic physics and chemistry is the debye (D). Theoretically, an electric dipole is defined by the first-order term of the multipole expansion; it consists of two equal and opposite charges that are infinitesimally close together. This is unrealistic, as real dipoles have separated charge.[1] However, when making a measurement at a distance that is much larger than the charge separation, the error introduced by treating real dipoles like they are theoretically perfect becomes negligible. By definition, the dipole's direction points from the negative charge towards the positive charge.

The Geneva Conventions of 1949 and their Additional Protocols

The first Geneva Convention protects wounded and sick soldiers on land during war. The second Geneva Convention protects wounded, sick and shipwrecked military personnel at sea during war. The third Geneva Convention applies to prisoners of war. The fourth Geneva Convention affords protection to civilians, including in occupied territory.

amazon water lily bloom scarab beetles

The giant water lily is a native to the shallow waters of the Amazon River basin. It has huge floating, tray-like green leaves and large, strongly fragrant white flowers that change to pink after the 2nd night of blooming. The flowers emit a pineapple-like fragrance. A chemical reaction inside the flower heats the bloom to as much as 20°F above the ambient temperature which helps to disperse the perfume and attract the scarab beetle that pollinates the lily. As daylight approaches, the flower shuts, trapping the beetle. During the day as the beetle struggles to escape it becomes coated in pollen. The flower then re-opens the following evening as a dark pink hue. The beetles are not fond of pink flowers and eagerly leave on their search for another white lily. Usually, only one flower blooms at any one time. The lily is well defended with sharp spines on the flower buds, leaf stalks and the underside of the leaves. In contrast, the leaf surface feels smooth to the touch and slightly rubbery. The lily pads have incredible buoyancy from the web-like structure of veins and as indicated prior, can support the weight of a well-balanced adult.

Thalidomide Tragedy

The importance of chirality -- or 'handedness' -- in drug development was brought to light in a devastating way almost half a century ago with the development of the Thalidomide drug. Prescribed widely to pregnant women for the treatment of morning sickness, it was later discovered that Thalidomide is a chiral molecule and while the left-handed molecule was effective, the right-handed one was highly toxic. As a result, thousands of children around the world were born with severe birth defects.

Enough sunlight reaches the earth's surface each minute to satisfy the world's energy demands for an entire year.

The total solar energy per second on a surface perpendicular to the Sun is about 1350 Joules per square meter or about 0.275 watt-hours. Taking into account incidence angle and the surface area, the effective energy arriving at the Earth is about 1.75E17 Joules per second. A lot of that is reflected away from clouds.

why pepper move away from soap in water?

This is because the pepper flakes are so light that the surface tension of the water keeps them floating on top. However, when you add a little dish soap, the surface tension of the water is disturbed. The water molecules move away from the soap taking the pepper with them

Two-phase electric power

Two-phase electrical power was an early 20th-century polyphase alternating current electric power distribution system. Two circuits were used, with voltage phases differing by one-quarter of a cycle, 90°. Usually circuits used four wires, two for each phase. Less frequently, three wires were used, with a common wire with a larger-diameter conductor. Some early two-phase generators had two complete rotor and field assemblies, with windings physically offset to provide two-phase power. The generators at Niagara Falls installed in 1895 were the largest generators in the world at that time and were two-phase machines. Three-phase systems eventually replaced the original two-phase power systems for power transmission and utilization. There remain few two-phase distribution systems, with examples in Philadelphia, Pennsylvania; many buildings in Center City are permanently wired for two-phase[2] and Hartford, Connecticut. The advantage of two-phase electrical power over single-phase was that it allowed for simple, self-starting electric motors. In the early days of electrical engineering, it was easier to analyze and design two-phase systems where the phases were completely separated.[4] It was not until the invention of the method of symmetrical components in 1918 that polyphase power systems had a convenient mathematical tool for describing unbalanced load cases. The revolving magnetic field produced with a two-phase system allowed electric motors to provide torque from zero motor speed, which was not possible with a single-phase induction motor (without an additional starting means). Induction motors designed for two-phase operation use a similar winding configuration as capacitor start single-phase motors. However, in a two-phase induction motor, the impedances of the two windings are identical.

the universe was orange

Ultimately, the CMB dominated the early universe, and because of its properties (like its temperature and the wavelengths of light it absorbed), the universe appeared orange for a few million years.

How do viral mutations occur?

Viral mutations occur when the RNA or DNA is copied incorrectly.

The explanation of why the Earth pin is larger and Longer than the Phase and Neutral pins is that

We all know that the earth pin is used to protect the user in the event of a short circuit resulting in the leakage of current through any of the metal regions of an appliance. (i)If a conductor has a large cross sectional area the resistance offered by it is very less hence larger size (ii) Imagine the following scenario, An user is holding a plug in one hand and has the other hand in contact with an appliance that has a current leak through the metal body and is trying to connect it to a live socket(ref above diagram:the switch is already in ON position even before connecting the plug): If the earth pin is of normal size the user may get electrocuted due to short circuit and the surge current that may flow through the metal body due to the live socket. but if it is longer,the earth pin goes and sits in the socket first so whatever current that may flow through the user to ground will flow through the earth pin to ground,thus the user is protected.

What happens when you increase the mass of a neutron star?

When the mass is increased, the star radius decreases causing the star to shrink and the internal event horizon to expand. The mass at which the radius of the neutron star and the event horizon overlap, 3 solar masses, causes the event horizon to come into being. In other words, once a neutron star reaches 3 solar masses, a black hole is created. A black hole is created when the event horizon overtakes the neutron star radius, leading to the neutron star radius to submerge beneath the event horizon.

If the sun is constantly converting the mass into energy, then will its gravitational field continue decreasing?

Yes.

do neutrinos have spin?

Yes. 1/2 for both A neutrino is a fermion (an elementary particle with spin of 1/2) that interacts only via the weak subatomic force and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. For each neutrino, there also exists a corresponding antiparticle, called an antineutrino, which also has spin of 1/2 and no electric charge. Antineutrinos are distinguished from the neutrinos by having opposite signs of lepton number and right-handed instead of left-handed chirality. To conserve total lepton number (in nuclear beta decay), electron neutrinos only appear together with positrons (anti-electrons) or electron-antineutrinos, whereas electron antineutrinos only appear with electrons or electron neutrinos.

The Pauli Exclusion Principle

You may have heard that matter is 99.999% empty space. If that is the case, why doesn't matter go through other matter? There are two pieces to the answer: the first one is the electrical repulsion between electrons; the second is something called the Pauli exclusion principle. Fermions have quite a remarkable property: no two of them can be in the same quantum state. What does that mean? Every particle in the universe is described by a set of numbers that specify its state. Some of these numbers are its energy, its momentum or its position. There are also other things like spin, which tells us the way the particle is spinning. What the Pauli exclusion principle tells us is that no two particles can have exactly the same numbers. For example, in atoms electrons move in "orbits" around the nucleus. I say "orbits", but electrons are really spread around a certain location we call an "orbital" and only have a definite position when we measure it. Let's stick to orbits for now. It turns out that only some orbits are allowed: let's call them 1, 2, 3, etc, going from less to more energy. Now just like people, electrons want to be in the state of least possible energy, so they will tend to want to be in the first orbital. Let's say we have three electrons. Our first electron chooses first and goes to the first orbital, because it has the least energy. The second one also wants to be there: can it? According to Pauli's exclusion principle, it can if at least one of the numbers that describes it is different. If it stays in the same orbit, the energy will be the same: however, the electron can still have a different spin, so we can fit it in the first orbital. Now, the third electron has a problem, because if it were in the first orbital it would have an identical state to one of the two electrons. Therefore, it cannot stay there and has to go to the second orbital. This is what causes atoms to have different sizes: otherwise all electrons would just be in the least-energy orbital! This is what happens to our charm quark up there: being a fermion, it cannot be in the same state as its friend. So, even though it would love the steak, it has to settle for salad. Sucks being a quark. Now, once all electrons are happy in their orbits, the atom has some decent size. If I put it next to another atom, the electrons in the outer orbitals will repel each other and the atoms will not be able to touch. This is what prevents matter from going through other matter. First, the Pauli exclusion principle gives atoms sufficient size; then, the electric repulsion does the rest. Does This Work for Bosons? No, it does not. As explained here, bosons have no problem occupying the same state, which makes them capable of going right through each other. In fact, you can have as many bosons as you want in the lowest energy state. This is the basis for Bose-Einstein condensates. Why does this happen? Honestly? We don't have a clue. The usual, technical answer is something akin to "the wave-function of a group of fermions has to be anti-symmetrical" or "the creation-annihilation operators must follow certain anticommutation relations." Now, this probably sounds like Chinese to you as it refers to the mathematical structure of a quantum theory. However, even though either of the two conditions above are equivalent to the Pauli exclusion principle, both have to be introduced without justification: that is, we add them because they work. A theory with these properties gives the right experimental results. That's it. Why does nature behave this way? Nobody has a clue. If this seems unsatisfactory to you, bear in mind that we have exactly the same problem with the speed of light. You know that the speed of light has to be the same for every observer; but why? Again, we don't know. The constancy of the speed of light was introduced by Einstein as one of the two postulates of his theory. A postulate is a statement that you give without proof: its ultimate justification is that it agrees with experiment. We know that the speed of light is constant because we've measured it many, many times and always got the same answer. Could the universe be different? Most certainly. But it isn't. Maybe in the future we will find a deeper theory that explains both of these things. But this theory, by definition, will also have unjustified assumptions. This is the nature of science: we look for the theory with the minimum number of assumptions, but we cannot have one without any.

do bosons interact with the higgs field?

You need to distinguish between the Higgs boson and the Higgs field. The Higgs field is the stuff that gives all other particles a mass. Every particle in our universe "swims" through this Higgs field. Through this interaction every particle gets its mass. Different particles interact with the Higgs field with different strengths, hence some particles are heavier (have a larger mass) than others. (Some particles have no mass. They don't interact with the Higgs field; they don't feel the field.) It is the opposite of people swimming in water. As people float in water they "become" lighter. Depending on size, shape, etc, some people float better than others. The Higgs field is not considered a force. It cannot accelerate particles, it doesn't transfer energy. However, it interacts universally with all particles (except the massless ones), providing their masses. The Higgs boson is a particle. It gets its mass like all other particles: by interacting with ("swimming in") the Higgs field. But as you can imagine, the Higgs particle differs from all the other particles we know. It can be thought of a dense spot in the Higgs field, which can travel like any other particle. Like a drop of water in water vapor. The Higgs boson has many more ways of interacting with all other kinds of particles than the Higgs field (which just causes a "drag" = mass). In this sense one might call the Higgs particle the mediating particle of the proposed Higgs field, like you wrote. The Higgs field is the silent field that gives the mass. We cannot directly probe for it. But discovering the Higgs boson, the "mediator", would prove the existence of the Higgs field. The Higgs particle, like many other elementary particles, is not a stable particle. Since it interacts with all kinds of other massive particles it can be created in collisions. (The Higgs particle does not interact with massless particles, such as a photon or a gluon. Since these particles don't interact with the Higgs field, the Higgs boson also doesn't interact with them.) Once the Higgs particle has been created, it will eventually decay. Though the Higgs particle interacts with all massive particles it prefers to interact with the heaviest elementary particles we know, especially the top quark, which was discovered at Fermilab in 1995. Because of this property of the Higgs boson physicists at Fermilab might have a chance to find evidence for the Higgs boson itself within the next five to six years. If they are not successful then an accelerator currently build at the CERN laboratory in Geneva, Switzerland, will have enough energy to produce the Higgs boson. Fermilab's accelerator currently is the world's most powerful accelerator, but physicists don't know whether it has enough power to create Higgs bosons. The new accelerator at CERN will have more power, but construction won't be finished until 2005. The Higgs particle is considered to be a carrier of a force. It is a boson, like the other force-transferring particles: photons, gluons, electroweak bosons. One may call the force mediated by the Higgs boson to be universal as the Higgs boson interacts with all kinds of massive particles, no matter whether they are quarks, leptons, or even massive bosons (the electroweak bosons). Only photons and gluons do not interact with the Higgs boson. Neutrinos, the lightest particles with almost zero mass, barely interact with a Higgs boson. Top quarks, which have about the mass of a Gold atom, have the strongest interaction with a Higgs boson.

The Strong Force

Yup, OK. Terrible joke. Pretty accurate, though: quarks are indeed "sticky." So sticky, indeed, that they can't separate themselves from each other. It is physically impossible to observe a single quark: they come in pairs or in threes (less often, in groups of four or even five) but, unlike the forever alone meme, they will never know loneliness. Quarks are sticky because of the strong force. This is just a force, just like gravity or the electromagnetic force. The messenger particle for the electromagnetic force is the photon; the messenger for the strong force is the gluon. However, the strong force is different from all the other forces in that it doesn't decrease with distance. Gravity, for example, gets weaker as you get further from its source. This is the reason why we don't all rush towards the Sun and instead just stick to good old Earth. But the strong force is always equally strong. If you try to pull two quarks apart, you will have to continue to push with exactly the same amount of force for all eternity. So what? You may think. Just pull enough. Eventually, they will be separated enough that we can see them. But things aren't so simple, thanks to Einstein's E = mc2. As we pull the two quarks away, we are giving them energy, in the same way that pulling on a rubber band gives it energy. But energy can be turned into mass, which means it can be used to create new particles! So, as we pull and pull, we give the system more energy and the energy is used to create more quarks, which again will be as close as they can possibly be. So then we can start pulling on the new quarks, but this will only have the effect of creating yet more quarks in a never-ending cycle. Long story short, we will never, ever, get two quarks far enough. There you have it: quarks are sticky and cannot be unstuck. They are forever doomed to spend their lives surrounded by their fellow quarks. Whether that's a good thing, you should probably ask them. Oh and, in case anyone wants to know, this pesky phenomenon is called confinement.

Inverter compressor

a compressor on a VFD? An inverter compressor is a gas compressor that is operated with an inverter. In the hermetic type, it can either be a scroll or reciprocating compressor. This type of compressor uses a drive to control the compressor motor speed to modulate cooling capacity. Capacity modulation is a way to match cooling capacity to cooling demand to application requirements.

sonogram

a graph representing a sound, showing the distribution of energy at different frequencies. Sonography is a noninvasive, painless procedure. It uses high-frequency sound waves — called ultrasound waves —to produce images of organs, soft tissues, blood vessels, and blood flow, from inside the body. These images are used for medical analysis.

fundamentalist

a person who believes in the strict, literal interpretation of scripture in a religion.

Laureate

a person who is honored with an award for outstanding creative or intellectual achievement.

Flavonoid

a pigment found in plants Flavonoids are widely distributed in plants, fulfilling many functions. Flavonoids are the most important plant pigments for flower coloration, producing yellow or red/blue pigmentation in petals designed to attract pollinator animals. In higher plants, flavonoids are involved in UV filtration, symbiotic nitrogen fixation and floral pigmentation. They may also act as chemical messengers, physiological regulators, and cell cycle inhibitors. Flavonoids secreted by the root of their host plant help Rhizobia in the infection stage of their symbiotic relationship with legumes like peas, beans, clover, and soy. Rhizobia living in soil are able to sense the flavonoids and this triggers the secretion of Nod factors, which in turn are recognized by the host plant and can lead to root hair deformation and several cellular responses such as ion fluxes and the formation of a root nodule. In addition, some flavonoids have inhibitory activity against organisms that cause plant diseases, e.g. Fusarium oxysporum.[3]

discotheque

a public dance hall for dancing to recorded popular music

lychee

a small rounded fruit with sweet white scented flesh, a large central stone, and a thin rough skin. Lychee is the sole member of the genus Litchi in the soapberry family, Sapindaceae. It is a tropical tree native to the Guangdong and Fujian provinces of southeastern China, where cultivation is documented from the 11th century.

nectar

a sugary fluid secreted by plants, especially within flowers to encourage pollination by insects and other animals. It is collected by bees to make into honey.

endoscope

an instrument used for visual examination of internal structures a long tube camera. can get as an extension for phone

Carotene

an orange or red plant pigment found in carrots and many other plant structures. It is a terpenoid hydrocarbon with several isomers, including beta-carotene. The human body converts beta carotene into vitamin A (retinol) - beta carotene is a precursor of vitamin A. We need vitamin A for healthy skin and mucus membranes, our immune system, and good eye health and vision.

crocus

any of numerous low-growing plants of the genus Crocus having slender grasslike leaves and white or yellow or purple flowers

faint of heart

coward Faint of heart describes a person who is lacking courage, squeamish, unable to rise to the occasion. An alternative phrase for faint of heart is faint at heart. Related terms are the adjective faint-hearted, the adverb faint-heartedly and the noun faint-heartedness.

tracheostomy

creation of an artificial opening into the trachea A tracheostomy is a medical procedure — either temporary or permanent — that involves creating an opening in the neck in order to place a tube into a person's windpipe. The tube is inserted through a cut in the neck below the vocal cords. This allows air to enter the lungs

Heteronormativity

denoting or relating to a world view that promotes heterosexuality as the normal or preferred sexual orientation.

co-opt

divert to or use in a role different from the usual or original one. "social scientists were co-opted to work with the development agencies"

error correction

immediate corrective feedback during reading instruction Error correction is the process of detecting errors in transmitted messages and reconstructing the original error-free data.

hepatitis

inflammation of the liver Hepatitis B and hepatitis C are both viral infections that attack the liver, and they have similar symptoms. The most significant difference between hepatitis B and hepatitis C is that people may get hepatitis B from contact with the bodily fluids of a person who has the infection. Hepatitis C usually only spreads through blood-to-blood contact. Neither hepatitis B nor C spreads through coughing, breast milk, sharing food with, or hugging a person who has the infection. Many people who have hepatitis do not become aware of it until the infection has advanced.

*nose tap*

it means "keep it secret" or "keep it hush-hush" lets tap our noses and move on

mangosteen

looks like garlic inside of a plum Mangosteen (Garcinia mangostana) is an exotic, tropical fruit with a slightly sweet and sour flavor. It's originally from Southeast Asia but can be found in various tropical regions around the world. The fruit is sometimes referred to as purple mangosteen because of the deep purple color its rind develops when ripe.

Dogs bark at cars' wheels because the engine produces high-pitch noises that humans can't hear, but dogs identify as a frightened dog inside.

maybe? get me an ultrasonic detector

LAGEOS

measures plate movement by bouncing laser beams between Earth stations and an orbiting satellite LAGEOS, Laser Geodynamics Satellite or Laser Geometric Environmental Observation Survey, are a series of two scientific research satellites designed to provide an orbiting laser ranging benchmark for geodynamical studies of the Earth. Each satellite is a high-density passive laser reflector in a very stable medium Earth orbit (MEO). The spacecraft are aluminum-covered brass spheres with diameters of 60 centimetres (24 in) and masses of 400 and 411 kilograms (882 and 906 pounds), covered with 426 cube-corner retroreflectors, giving them the appearance of giant golf balls. Of these retroreflectors, 422 are made from fused silica glass while the remaining 4 are made from germanium to obtain measurements in the infrared for experimental studies of reflectivity and satellite orientation.[6] They have no on-board sensors or electronics, and are not attitude-controlled. They orbit at an altitude of 5,900 kilometres (3,700 mi),[7] well above low earth orbit and well below geostationary orbit, at orbital inclinations of 109.8 and 52.6 degrees.

What is R0?

net reproductive rate In epidemiology, the basic reproduction number (sometimes called basic reproductive ratio, or incorrectly basic reproductive rate, and denoted R0, pronounced R nought or R zero[16]) of an infection can be thought of as the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection. e.g. measles R0 = 12-18 meaning one infected person can infect 12-18

Harmonic

one of many natural frequencies of an oscillator A harmonic is any member of the harmonic series. The term is employed in various disciplines, including music, physics, acoustics, electronic power transmission, radio technology, and other fields. It is typically applied to repeating signals, such as sinusoidal waves. A harmonic of such a wave is a wave with a frequency that is a positive integer multiple of the frequency of the original wave, known as the fundamental frequency. The original wave is also called the 1st harmonic, the following harmonics are known as higher harmonics. As all harmonics are periodic at the fundamental frequency, the sum of harmonics is also periodic at that frequency. For example, if the fundamental frequency is 50 Hz, a common AC power supply frequency, the frequencies of the first three higher harmonics are 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), 200 Hz (4th harmonic) and any addition of waves with these frequencies is periodic at 50 Hz.

Nectar guide

pigment pattern on a flower that guides an insect to the nectaries Nectar guides are markings or patterns seen in flowers of some angiosperm species, that guide pollinators to their rewards. Rewards commonly take the form of nectar, pollen, or both, but various plants produce oil, resins, scents, or waxes.

Maillard reaction

reaction between proteins and carbohydrates that causes food to brown when cooked In the cooking process, Maillard reactions can produce hundreds of different flavor compounds depending on the chemical constituents in the food, the temperature, the cooking time, and the presence of air. These compounds, in turn, often break down to form yet more new flavor compounds. Flavor scientists have used the Maillard reaction over the years to make artificial flavors.

Administrations come and go, but the underlying structures don't change.

relating to politics or systems that just don;t work.

Witch-hunt

searching for something that doesn't exist and making up rules on the fly

dopamine traps

social media, feedback loops, etc.

sacred

something that has taken on so much moral importance that it can no longer be questioned

Lorentz transformation

the transformation, valid for all relative velocities, which describes how to relate coordinates and observations in one inertial frame to those in another such frame. In physics, the Lorentz transformations are a one-parameter family of linear transformations from a coordinate frame in spacetime to another frame that moves at a constant velocity relative to the former. The respective inverse transformation is then parametrized by the negative of this velocity.

Quantum entanglement

the unusual behavior of elementary particles where they become linked so that when something happens to one, something happens to the other; no matter how far apart they are. particles is generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the pair or group cannot be described independently of the state of the others, even when the particles are separated by a large distance. The topic of quantum entanglement is at the heart of the disparity between classical and quantum physics. Measurements of physical properties such as position, momentum, spin, and polarization performed on entangled particles are found to be perfectly correlated. For example, if a pair of entangled particles is generated such that their total spin is known to be zero, and one particle is found to have clockwise spin on a first axis, then the spin of the other particle, measured on the same axis, will be found to be counterclockwise. However, this behavior gives rise to seemingly paradoxical effects: any measurement of a property of a particle results in an irreversible wave function collapse of that particle and will change the original quantum state. In the case of entangled particles, such a measurement will affect the entangled system as a whole.

obliviate

to forget, to wipe from existence; destroy completely

hydronic cooling

using a chiller or geothermal Hydronic cooling is simply the removal of heat from the space utilizing chilled water as the heat exchange medium. As opposed to evaporative cooling which introduces humidity into the space, hydronic cooling is completely closed loop meaning no water is added to the space for the purpose of cooling

de broglie wavelength

λ = h/mv the wavelength associated with a moving particle According to wave-particle duality, the De Broglie wavelength is a wavelength manifested in all the objects in quantum mechanics which determines the probability density of finding the object at a given point of the configuration space. The de Broglie wavelength of a particle is inversely proportional to its momentum. Matter waves are a central part of the theory of quantum mechanics, being an example of wave-particle duality. All matter exhibits wave-like behavior. For example, a beam of electrons can be diffracted just like a beam of light or a water wave.