SEMMELWEIS UNIVERSITY, MEDICAL BIOPHYSICS - FINAL EXAM

How do you determine concentration by absorption photometry?

Beer lamberts law: valid for dilute solutions log(Jo/J)=ext.coeff*c*xExt.coeff. depends on the type of material and the wavelength.

Bernoulli's law, ​plasma skimming.

Bernoulli's law: in a steady flow, the sum of all the energy in a fluid along a streamline is the same everywhere on the streamline. plasma skimming: The natural separation of red blood cells from plasma at bifurcations in the vascular tree, dividing the blood into relatively concentrated and relatively dilute streams.

Brownian motion. ​Random walk.

Brownian motion is a phenomenon where particles have "random walk" (which itself exists in many other fields as well). Brownian motion: the random motion of particles due to collisions with the surrounding molecules.

Power and efficiency of the x-ray tube.

Efficiency i​s very low, 1%. Most of the energy from the accelerating electrons will be dissipated as heat. The anode must be cooled down and a material of high melting point should be used (tungsten). Can be calculated as the ratio between the power in (P=U I) and the power out. Power i​s proportional to the voltage, the current and the atomic number of the anode (tungsten). Px=cxU^2IZ

Einthoven-triangle, integral vector.

Einthoven-triangle: an imaginary equilateral triangle connecting the shoulders and the hip, practically is composed of the electrodrods of the hands and the left foot. the side walls of the trigon are the leads (I,II,III). Integral vector: spatial dipole vector representing the electric field of the heart, practically we refer to its frontal plane which is made by using the Einthoven's trigone.

Wave nature of the electron.​ Davisson Germer experiment

Electrons behave like waves in certain situations like being diffracted. We can calculate the wavelength of electron the formula for de Broglie: wavelength=h/p, when p(momentum)= mass*velocity

Bohr's atomic model.

Electrons in an atom can only occupy certain distinct orbits around the nucleus. The electrons in their orbits won't radiate unless they will be excited and jump to an higher orbit. We can calculate the frequency of a radiated electron by calculating the difference of energy btw the 2 orbitals using this formula: hf=Em-Ei

Applications of the Boltzmann-distribution I. : Nernst equation.

Epot=q*U(charge*voltage) The distribution of charge particle at point A and B can be calculated by this formula: nA/nB=e^(-qU/kT)

What is hyperopia and how do you correct it?

Farsightedness, rays from close objects form the image behind the retina, corrected using converging lenses.

Thermoluminescent dosimetry.

Ionizing radiation excites an electron from the valence band to the impurity level of the dopant → this electron stays "trapped" in the dysprosium's activated energy level → heat applied to the crystal causes further excitation of the electrons into the conduction band from which they will relax → light is emitted. Number of photons is proportional to the dose. Application- personal dosimeter.

How does the bandwidth of an amplifier change with negative feedback.

It broadens (see figure above)

How does the resonance frequency change if the oscillating mass is doubled?

Decreases (by approx 30%)

How does the minimum wavelength of the x-ray spectrum change with increasing anode voltage?

Decreases (higher voltage ​​higher kinetic energy ​​higher frequency spectrum) - Duane-hunt law

How does optical rotation angle change if the sample tube length decreases?

Decreases due to the proportionality (biot law)

Activity.

Defined as the rate of decaying atoms per unit sime (s) unit: Becquerel (Bq). 1Bq = 1 decay/sec

The dose rate.

Defined as the ratio of the dose and the time of irradiation

Light scattering (Rayleigh and ​Mie).

Light scattering occurs when EM waves encounter particles in the air. The light waves will cause a dipole moment, making electrons in the atoms vibrate (forced oscillation), which will cause them to emit light. Rayleigh scattering​ depends on wavelength. (blue light is scattered more) When particles are spaced far enough apart (spacing is larger than the wavelength), there is no interference, thus the intensity of incident light = intensity of scattered light. We know that the dipole moment produced by the light is proportional to the angular frequency. ω = 2πf (angular frequency) Thus the higher the frequency the higher the scattering (blue light scatters much more → sky is blue) Mie scattering,​ on the other hand, is not wavelength dependent, thus all wavelengths scatter equally (producing white light) when the size of the particle is on the order of the wavelength, this type of scattering occurs closer to the earth's surface. (H2O in clouds)

Fermat's Principle

Light will choose the path which takes the least amount of time (i.e spend the least amount of time in the slower medium). Is the basis for the phenomenon of refraction and reflection.

Compare the linear attenuation and mass attenuation coefficients for water and steam.

Linear attenuation coeff depends on density ​= water will have a higher value. Mass attenuation coeff: independent of density ​​ same values for both water and steam.

How do you determine the transfer band of an amplifier?

Max. gain level- 3dB determine the cutoff freq. Transfer-band is located within the cutoff freq.

Does a greater phon value always correspond to a louder sound?

Yes, Lphon = 10log (J/J0)1000Hz that is Lphon = Jdb 1000 Hz

Thermal radiation.

Transfer of heat by using EM radiation → possible even in vacuum. Every matter above 0K radiates thermal radiation.

Isotopes.

Two or more atoms which have the same atomic number but different atomic mass (same no. of proton and electrons and diff. no. of neutrons)

Oscillations.

Phenomenon in which quantity varies as a function of time around an equilibrium value

What is optical dispersion?

Phenomenon in which white light is decomposed into component colors due to the dependence of refractive index on frequency

Structure of biopolymers.

Protein - AA - covalent Nucleic acid - nucleotide - covalent Polysaccharide - sugar - covalent Protein polymer - protein - secondary

Which sample transmits more light: OD=1 or OD=3? By how much?

Shift log ^-1=1/10 (*100%)Sift log ^-3=1/1000 (*100%)OD=1 transmits one hundred-fold more light

Kasha's rule.

The excited molecule first reaches the lowest vibrational level of S1 and photon emission occurs always from this state to any vibrational level of the ground (S0) state.

Phase diagram of water.

Pressure over temperature; same chemical, different phases.one of the special properties that makes it different = "anomaly" of water is that it has a negative melting curve. When temperature is constant and pressure is increased, ice will melt.

How would you measure the position and diameter of the blind spot?

Using the x and dot test, measuring when the dot disappears and appears would give the size of the blind spot. d = d′ where d is x 17the known distance between the dots on the paper, x is the distance of the paper from the eye (the distance from the nodal point to the retina in the reduced eye is 17mm).

Sound as a wave.

Sound is a mechanical wave - a "pressure wave" which are sinusoidal oscillations.​ It is a longitudinal wave in liquid and in gases, ​which means that the oscillation is parallel to the direction of propagation. In solids the waves can be either longitudinal or transverse.

Types of waves.

Sound waves (longitudinal or transverse) - require a medium Electromagnetic waves (transverse waves) - do not require a medium Matter wave (matter can act as a wave; electrons can have wavelike interference)

Basics of diffusion: Concepts, thermal motion.

The random motion of particles as a result of thermal motion, which is a result of the particle's thermal energy (which depends on its temperature). Particles will interact with each other due to their own thermal motion, this interaction will cause the particles to change direction.

Kirchhoff's law.

States that a body which radiates more thermal energy is also absorbed thermal energy to a higher extent. The ratio between radiant emittance and absorption coefficient is constant within a narrow range of wavelength Mbody1/alphabody2 = Mbody2/alphabody2 = const

Shannon-Nyquist theorem.

States that for successful reconstruction of the signal, the frequency of the sampling should be at least t​wice​higher than the highest frequency signal component (overtone)

Teletherapy, geometric viewpoints.

Teletherapy: high gamma radiation induced (relative depth dose), from many different directions in order to create high dose on the cancer but split the dose between the healthy tissues (reduce damage) (isotope cs).

Physical foundations of the periodic table.

a. Numbered according to the numbers of protons b. Size: increases from right to left in the period and from up to down in the group c. In every group the number of valence electrons is the same d. Ionization energy: increases in the group from bottom to the top and in the period from left to right (oppositely to the atom size orientation) e. Electron configuration: s,p,d,f blocks (d=-1 f=-2)

Types of radiation

according to energy transfer: Electromagnetic (light), mechanical (sound), particle (alpha) according to interaction with matter: ionizing (alpha), nonionizing (sound)

The cardiac cycle.

atrial contraction isovolumetric contraction→ ventricular contraction (P increase V constant) rapid ejection→ ventricular contraction reduced ejection isovolumeric relaxation (P decrease V constant) ventricular filling

Pressure relations in the arterial system.

due to continuity law: aorta has the smallest cross-sectional area thus highest pressure while capillaries have the opposite properties

Fluorescence.

is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It's a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. If the luminescence stops as the excitation stops (the relaxation step takes 10−8 seconds). (Application: fluorescent lamps lasers, page 133)

Dual nature of light.

light can behave in some cases as a wave (e.g. interference) and in other cases as a matter (e.g. photoelectric effect)its energy packed in quanta that depends on the frequency.

Changes in pressure in the circulatory system.

pressure drops due to resistance to flow, the energy is dissipated into heat. Pressure drop, is the intensive variable maintaining the flow rate. Highest in the arteries, declines greatly in the arterioles and becomes very small towards the veins.

Light sources based on thermal radiation.

sun, light bulb, heated metal (at first will glow in red and after further heating will change to yellow and blue = wien's law. Mblack(T)=sigmaT^4

Structure and properties of water.

structe: H2O tetrahedral shaped.in its liquid form its is rearrange as pentamer (H2O)5 or as octamer properties: a. permanent dipole moment→ good solvent anomalous density-temp. function→ the highest density is at 4 degrees celsius large surface tension anomalous phase diagram→ by exerting enough pressure ice can be converted into water !

refractive power

the degree to which lenses are able to converge or diverge light. formula: D=1/f (f=focal point)

Reaction steps of light sensation.

light travels from the cornea→ to the anterior chamber→ to the lens→ to the vitreous humor→ to the optic nerve→ to the photoreceptor cells. light photon is being absorbed, rhodopsin → conformational change occur→ enzymes are being activated→ big number of Na+ channel is inhibited→ hyperpolarization→ the release of inhibitor transmitter is reduced.

Equilibrium conditions of different thermodynamic systems.

mechanical equilibrium: pressure throughout the system and in the surrounding is the same chemical equilibrium: the rates of the forward and the backward reactions are the same thermal equilibrium: two matter in contact with each other and there is no heat exchange

Properties of laser light.

monochromatic coherent (due to induced emission→ constant phase difference) small divergence (the laser beam is nearly parallel) high intensity ​(because. 1. emitted from narrow beam and 2. can be further improved by focusing the beam) often polarized

Physical, chemical and biological phases of radiation effects.

physical: ionization chemical: free radicals biological: damage to DNA

The x-ray summation image.

when the elementary densities along the direction of the x-ray beam are summed. Produces the projection image.

How do you separate the red-blood-cell versus white-blood-cell signals in a Coulter-counter?

when you want to measure RBC, it's not necessary to separate them from the RBC b.c. the number of WBC is negligible (less than error of the measurement) By hemolyze RBC and measured them separately photochemically and subtracted the result from the coulter-counting measurement

What is the gain level if the voltage gain equals 1?

0 (dB)

Interaction of beta positive radiation with matter.

*Radioactive particle in positive beta radiation is positron* When a positron interacts with matter it will collide with an electron by annihilation process which causes emittance of 2 gamma rays which emitted in 180 degrees to each other.

Emission spectrum of the absolute black body.​

*The emission is in all wavelength spectrum. According to Wien's law, the maximum radiation is in wavelength that is inversely proportional to the temperature. wavelengthMax*T=constant. At low temp. black body appears black- most of the energy it radiates is infra-red. when it getting how it will start to glow at first in red color and than in yellow and finally white-blue - according to planck: radiation energy of a black body is emitted in discrete integer multiples. Quantum E = h*f - according to stephan boltzmann: Mblack(T) = sigmaT^4 describes the emittance of the black body as a proportion to temp. (fourth power proportionality)

Which one is louder: 30 Hz, 90 dB vs. 1 kHz, 70 phon (formula collection, isophone curves)

1kHz at 70 phon

Kinetic gas theory.

5 main assumption which explain the behaviour of gas (ideal): 1) Particles are very small compared to the total volume 2) Constant random motion 3) Colliding of the particle one another is elastic 4) Particles exert pressure on walls when they are under higher psi/temp

What are the x-ray spectral lines characteristic of?

Anode material

Parts and functions of the Coulter-counter

- Two spaces with a small aperture in between, capillary (contains the electrolyte solution with the cells) - Measuring electrode, one in each of the spaces (closing the circuit and measuring voltage between the two spaces) - Pump (draws the solution into the smaller space, and out again, through the capillary) - Auxiliary electrode (signals when certain volume is reached, to initiate pumping out of the solution) - Integral Discriminator (filter out noise) - Differential Discriminator (mapped of the size distribution of the particles)

What is the duration of a 2-mm-wide QRS complex if the horizontal scale is 25 mm/s?

0.08s

What fraction of intensity is transmitted through an absorber with a thickness three times its half-value layer thickness (x=3D).

0.125

What fraction of intensity is transmitted through an absorber with a thickness twice its half-value layer thickness (x=2D).

0.25

What is the x-ray density of a voxel that absorbs 90% of the incident x-ray.

1 (log(100/10)

Factors influencing the visual acuity.

1. Irregular shape of the lens and the eyeball 2. Diffraction (causing airy disks) 3. Anatomical density of photoreceptors (rods and cons)

Effects of ultrasound, therapeutic applications.

1. the energy(?) that propagates in ultrasound is dissipated (dampes) in the medium in form of heat. 2. intensity of US proportional to pressure difference (high intensity can separates cells from each other in a tissue and form cavities. 3. we know that the higher the energy the higher the absorbance in the tissue (higher damping) *We can use this knowledge and by focusing our ultrasound beam into the tumor for example we can create micro cavities in the tumor tissue and heat it and by that destroy it.

Properties of the action potential.

1. unaltered ion concentration: only the permeability is changing (GHK equation is valid) 2. refractory period (dead time) 2 types: - absolute: voltage gated of Na are inactive - relative: action potential can occur but it requires much higher threshold stimuli to (prevent the backpropagation) 3. special AP: cardiac AP the duration is much longer (200-400 ms) thanks to additional channels, CA(2+) channels. 4. (''All or none''- stimuli have to exceed a threshold level to trigger action potential. 5. controlled by the opening and closing of voltage driven channels 6. action potential is very fast 1.5ms)

What is the voltage amplitude of a 12-mm-high R(I) signal if vertical sensitivity is 1 mV/cm?

1.2mV

What is the refractive index of distilled water?

1.33

What is the refractive power of the unaccomodated human eye?

64 dioptres

Describe the steps of the eyepiece scale calibration process.

1.eyepiece scale is placed in the intermediate image plane (unknown units)2.place a stage micrometer (with known units) as a ''specimen'' 3.focus the eyepiece scale and the micrometer on one another 4.calculate the calibration factor by dividing the known length of the stage micrometer by the number of rules of the eyepiece scale.

Types of doped semiconductors.

1.p​ type (boron) (acceptor level) (holes) and n type (phosphorous) (​donor level) (electrons)

Calculate the refractive power of a lens with a focal distance of 17 mm.

1/0.017=5.88 dpt

Calculate the refractive power of a lens with a focal distance of 20 cm.

1/0.20=5 dpt

Calculate the refractive power of a lens with a focal distance of 25 cm.

1/0.25=4 dpt

How much light is transmitted by a sample with an absorbance of 1?

10%

What is the total magnification of a light microscope if the objective magnification is 100x and the ocular magnification is 20x?

100*20= 2000

X-rays: Typical diagnostic wavelength and photon energy range.

100ev-​200 keV min. wavelength 6pm-​12nm

What is the power gain if the gain level is 3 dB?

2 (formula: n= 10* log Ap)

How many electrons arrive at the PMT anode for every photoelectron if the number of the dinodes is 8 and the multiplication factor is 2. (Why?)

2^8 because at every diode number of the electrons is doubled.

The 2nd law of thermodynamics, direction of spontaneous processes.

2nd law: heat will flow from higher temp area to lower temp area. direction of spontaneous processes shifted to the process with which the highest entropy state is achieved. the process is reversible as long as the combined entropy of the system and the surrounding remains constant (thermal or chemical equilibrium). If the process is irreversible the combined entropy of the system and the surrounding is increased. (e.g. hot object is put in contact with cold object). Entropy increases steadily in the universe (isolated system) and can not be decreased

Heat transport, Fourier's law.

3 main mechanisms: conduction: net energy flow (by contact) btw particles from high temp area with higher kinetic energy, and from cooler area particles by colliding and transfer part of their kinetic energy (w/o exchange of matter) know fourier's law (conduction rate equation): where lambda= heat conductivity we also have two other mechanisms: convection: heat transfer by movement of fluid (e.g. hot ground→ the air next to it get hot lifted up, cold air sink down get hot by the ground floor and goes up) thermal radiation: every matter radiate thermal radiation (does not require medium)

Structural hierarchy of proteins.

3 main structural hierarchy:primary→​define the sequence of a.a→ peptide bone secondary→​alpha-helix, B-sheet→ H-bonds, secondary bonds, tertiary→​define the 3D str. of the polypeptidehierarchy of the bonds:weak bonds: H-bonds,van der waals, hydrophobic-hydrophobic interaction, dipole dipole, dipole-dipole bondscovalent bonds: disulfide bridge→ b/w to cystin aa side chains connects diff part of the polypeptide

Matter transport through the cell membrane.

3 types of membrane transport: a. passive d​iffusion:​fick's first law (​+ extension):​​ where the driving force is the chemical potential gradient as well as the electric potential gradient. Ficks first law is used with an extension to include this electrochemical gradient. b. facilitated: require mediator molecules (channels or carrier): faster than simple diffusion, is selective (receptor protein must fit to the molecule), can be inhibited (as used in antibiotics). c. active: against electrochemical gradient- (e.g atp-driven, l​ight gated or coupled transporter)​

What is the maximum x-ray photon energy at 50 kV anode voltage?

50 keV

Spectrum of Bremsstrahlung.

A continuous spectrum illustrating the "breaking" radiation released by accelerating electrons. Increasing the voltage will result in electrons with higher kinetic energy, x-ray photons of higher frequencies will be emitted. Changing the heating of the cathode, will result in more electrons, thus a higher current. The area under the curve represents the total emitted power.

The fluorescence spectrometer.

A device which shines a light through a sample, measuring the excitation spectrum and the resulting emission spectrum.

Interaction of gamma radiation with matter II: Compton-scatter.

A gamma photon removes an electron from the ​outer shell: a "​Compton electron", and a photon (of lower energy) is emitted. The initial energy of the gamma photon is thus divided between the work function (to remove the electron) and the energy of the photon.

Definition and interpretation of the audiogram.

A graph which provide us the difference bw the values of normal hearing and the hearing values of the patient at various frequencies. The hearing loss is shown on the graph as the difference between the two thresholds. J measured - J normal = loss

Electronegativity

A measure of the strength with which an atom will hold on to its electrons and can ionize other atoms. $ Atoms of small size with a high atomic number are more electronegative (larger nucleus = more positive charges, yet small in size means electrons are closer to nucleus and that they don't produce much shielding for valence electrons, from the nucleus) Most electronegative atom is Fluorine. In a bond, atoms of higher electronegativity will pull electrons towards them, causing polarity in a molecule.

CAT-scan: Principles, generations.

A method based on xray which scans part of the body from different angles and provides a cross-sectional image of the body. x-ray alone can't give us information on the depth of the body, by summation of a lot of x-ray images that were taken from different angles we can divide the area which we are investigating into voxels which are similar to pixels in an image.

Multimodal imaging: PET/CT and SPECT/MRI.

A method which superimposes a functional imaging method (pet or spect) with structural imaging method (CT or MRI). The product is a high resolution image with identifiable anatomical structure and information about the function status.

Bragg-diffraction of X-rays.

A method which uses crystals as a diffraction grating for X-rays. The lattice spacing between crystals is on the order of nm, which allows for interference patterns to be formed, they are studied to obtain information about the crystals atomic structure. Information can be obtained because we know that constructive interference results in bright spots on the diffraction pattern "interference maxima", and that the condition for this is that the incident angle = refracted angle and that the difference in path length be an integer multiple of the wavelength.

Sensory adaptation.

A process by which a stimulus causes a decreasing frequency of action potentials (receptors get used to the stimulus) Slow adaptation, tonic receptors: pain and cold receptors: Rapid adapting, phasic receptors: pressure, smell, heat.

Beta negative decay.

A process in which unstable nuclei convert a neutron into a proton (stay in the nucleus) electron and antineutrino (emitted). An unstable nucleus emits an electron and an antineutrino. A n​eutron in the nucleus ​becomes a ​proton​t​hat remains in the product nucleus. Thus, negative beta decay results in a daughter nucleus, ​with a higher atomic number and the same mass number.

Laser: population inversion.

A process in which, by exerting energy on the system, the electrons are ''pumped'' from their ground state. Thus, most of the molecules are in their excited state and are s​taying in intermediate metastable state (until induced emission is formed) *require at least 3 energy levels.

Polarization of light.

A process which unpolarised light (light whose electric field vectors propagate in more than 1 plane, which contains the direction of propagation) become polarized light (light whose electric field vectors propagate only in 1 plane, which contains the direction of propagation) by an optical filter (polarizer)

Stokes-shift

A shift difference btw. the peak absorption (excitation) and the peak of emission wavelength, due to loss of energy in form of heat (vibration and rotation of the molecule)

Describe the reduced eye model.

A simplified representation of the eye, with only one refractive surface, index of refraction and curvature of spherical surface and a center of curvature (17mm).

Describe a pulse signal.

A single jump of signal to higher amplitude and then back to the normal baseline.

Diffraction on an optical grating.

A structure with periodic optical properties. Its characteristic feature is the grating period (d) with a size on the order of the wavelength.

The sone scale.

A subjective perception of loudness level. Based on the observation that every 10 phon increase in loudness level is perceived as a doubling of the sound sensation. 1 son = 40 phon, 2 son= 50 phon, etc.

Polarization microscope.

A technique that makes birefringent details of a specimen visible. Examples of birefringent materials include: cell membranes, striated muscle and myelin sheath of neurons. The microscope is equipped with a polarizer which illuminates the specimen with linearly polarized light. On the other side of the specimen, another polarizer is used: "an analyzer", at 90 degrees from the polarizer. At this angle the view is dark. Light which was rotated by birefringent parts of the specimen passes, so that only these details are visible.

Determination of molecular structure by x-ray crystallography.

A tool used for determining the molecular structure of a crystalized substance by diffraction and interference of x-rays. 2dsin theta = n * wavelength if n = integer = constructive if n = fraction = destructive

Laser: the optical resonator.

A tube with two mirrors on both sides. The mirrors reflect the light emitted by the laser material, and thus amplify it. One mirror will allow 1% of the light through, this is the beam which can be utilized. A condition for the resonator is that a wave that is reflected from its starting position, will return to that position in the same wavelength. L=length, m=integer. The double distance between the mirror must be an integer multiple of the wavelength.​

Boltzmann distribution.

A universal organizing principle, in which energy levels in a thermally equilibrated system are populated by an exponential function. At higher temperatures, higher energy levels are more populated. P(h)/P(0)=e^(-mgh/kT)

Structure and function of the x-ray tube.

A vacuum tube with an anode and a cathode. The cathode is heated and electrons are emitted, they are accelerated by a voltage difference in the tube. When the "brake" against the material of the anode, they release their high kinetic energy in the form of an x-ray. *x-ray tubes are of very low efficiency, most of the radiation is dissipated as heat.

Definition of absorption spectrum.

Absorbance as a function of wavelength. Unique to every element.

Properties of the absorption spectrum.

Absorbance or transmittance as a function of wavelength. Varies depending on the atom or molecule, as it depends on their electronic structure, thus can be used to identify an element. Since absorption requires the excitation of an electron into the next energy level, it requires a photon of specific wavelength to make that transition: as a result some wavelengths will be absorbed completely, while others will be transmitted.

Hounsfield unit, windowing in CAT scan.

Absorption coefficient and density values for CT imaging are measured in Hounsfield units. N CT = 1000* (mu-mu W)/(mu W) Windowing in CT​is contrast manipulating technique in which a range of CT number values (which are density values) can be selected for the grayscale display of the image while others can be ignored. For example; soft tissue window, lung window or brain window.

Compare the x-ray absorption of bone and muscle tissue.

Absorption in bone is higher due to higher density and atomic number.

Compare the x-ray absorption of lung and muscle tissue.

Absorption in muscle tissue is higher due to higher density and atomic number (lungs are filled with air)

Energy levels of intrinsic semiconductors.

According to band theory, there is a valence band and a conduction band. In a semiconductor, the gap between them is large enough that electrons do not pass freely. However, the gap is not too large (Δε = 1eV ), therefore upon excitation, electrons can cross into the conduction band and electricity will be conducted.

Fourier-theorem for periodic and aperiodic signals.

According to this theorem, any signal can be decomposed as a sum of sinusoidal signals, and any signal can be constructed from sinusoidal components. This is useful in signal processing because if the frequency range of the measured signal is known, the signal processing system only has to transfer sinusoidal signals of this frequency range, and thus it can reconstruct the signal without distortion.

Acoustic impedance, reflection, of sound, reflectivity.

Acoustic impedance:​quantity that shows to what extent the medium resists when particles are brought into motion, practical equation: Z = rho * c (product of the density and the speed of sound in the specific medium) (Z also can be measured by the ratio of the square root of density and compressibility) reflection:​ At the boundary of 2 media part of the intensity of the sound reflect into the opposite direction and not penetrate the body the extent of this phenomenon is measured by the reflectivity equation. *ultrasound diagnostic methods are based on that phenomenon. reflectivity: measured by the ratio of the reflected intensity according to this formula: R = JR/J0 = (Z1-Z2/Z1+Z2)^2 when R=1 → max reflection, when R=0 → no reflection

Special functions of a pacemaker.

Acts as a pulse generator, in case of malfunction of the hearts conducting system (SA and AV nodes), delivers a pulse which causes the subsequent contraction of the myocardium and restoration of normal heart rate.

Advantages and disadvantages of using negative feedback in an amplifier.

Advantage:​ less distortions, broader transfer band, more stable, less noise (e.g. less sensitive to temp change) (​note: negative feedback doesn't deal with input noise) Disadvantage:​ less gain

What is presbyopia and how do you correct it?

Age induced farsightedness, when the lens is inelastic and the eye can't accommodate rays from close objects form an image behind the retina. Corrected with converging lenses.

DSA. (​digital subtraction angiography)

Aim: creating an image which focus on the blood vessels steps of procedure: a. x-ray image is take w/o contrast image (native) b. contrast agent is injected→ additional image is taken (contrast) c. by subtracting the native image from the contrast image we produce new images that concentrate on the vessels

electromagnetic spectrum

All of the frequencies or wavelengths of electromagnetic radiation

Continuity equation.

Along a tube (rigid tube) the volumetric flow rate is uniform along the entire length, which means that the same volume of fluid must pass through each cross section at a given moment. If the cross section becomes smaller → fluid velocity increases. For real fluids, which are not stationary, the average velocity is used in the formula.

Energy spectra of alpha, beta and gamma radiations.

Alpha spectrum: discrete (line) due to the fact that all the excess of energy goes to the alpha particle which releases from the unstable nucleus. Beta spectrum: continues, due to the fact that the emitted particles are the electron (or positron) and antineutrino (or neutrino) so the energy splits btw. them randomly. Gamma spectrum: discrete, due to the fact that gamma radiation is packed in quanta (different spectrum to different radionuclides)

Information coding by the receptor potential.

Amplitude coding, where the intensity of the stimulus corresponds to the receptor potential.​When the stimulus exceeds a given threshold, an action potential will be generated.

Resonance curve.

Amplitude vs frequency curve of the driven oscillator

Time of flight principle in mass spectrometry.

An analyzing method in which by converting potential energy into kinetic energy we can calculate the time it takes for an i​on t​o cross a certain distance → the heavier the molecule the longer time it will take. ion detector will be: scintillation counter or electron multiplying

What is a chiral molecule? Provide an example.

An asymentrical molecule (non-superimposable images ) ex: D-glucose

Describe the linearly polarized light.

An electromagnetic wave, in which the electric field line vector propagates in one plane only.

Scintigraphy.

An examination for which a low quantity of radiopharmaceutical insert to the body, its aggregation in the target organ can provide us information about the investigated organ. The gamma energy is detected by a gamma camera and thanks to the collimator only the rays which are parallel to the detector are detected, and precise signal mapping can be formed.

Absolute black body.

An ideal, theoretical ​body which absorbs all the radiation incident on it and rememits it. A model can be created from a closed metal cavity with a hole drilled into it, so radiation energy cannot easily escape, thus it is absorbed completely. (Absorption coefficient of Stefan-Boltzman law​describes that the emittance of a black body is proportional to the fourth power of the temperature: Mblack(T)=sigmaT^4

Electric model of the membrane.

Analog of capacitor (two conductive layer and the membrane use as insulator material) the permeability of each substance can be modelled as conductivity (1/R)

Digitization of analog signals.

Analog signals need to be converted to digital signals so that they can be read and interpreted. ADC is the device which can make this conversion. It's done by performing many readings of voltage at different times, assigning values to them (i.e sample readings). The more sample readings, the more precisely it converts the original signal. The sample reading should take place at the same frequency as the signal, so that it doesn't miss anything.

Law of reflection.

Angle of incidence = angle of reflection Incident beam, reflected beam and optical axis are in the same plane.

Work of the heart.

Approx 1JCan be calculated by multiplying pressure and the change in volume = volumetric work. The work is expressed as the area under the pressure volume curve.

Pressure of ideal gases.

Assuming no interactions between particles, and negligible particle volume: pV=NkT or pV=nRT. k= boltzmann constant n=moles N=number of particles R= gas constant

Macroscopic magnetization in MRI: spin-spin relaxation.

At the end of the 90 degree excitation pulse, all vectors will point in the horizontal direction, and will rotate in the same phase, but now that the energy input has stopped, they will try to regain their random distribution and lose the phase coherence. When speaking only about the loss of phase:​the characteristic time for this process is called the s​pin-spin relaxation time (T2). During this relaxation process the macroscopic magnetization is 0 and they have random orientation. During the return to a lower energy state there will be a release of energy, which is detected As different tissues have different ​T2, this allows for contrast generation between two tissue types (​for example: larger mobility is associated with a longer relaxation time).

Resolving power of the atomic force microscope.​

Atomic scale (sensitive to the van der waal's attraction) Resolution is in the order of fractions of a nanometer, which allows the study of strength and length of chemical bonds and the detail of molecular structure.

Potential energy of interatomic interactions.

Atoms within a molecule are organized in more or less fixed positions in which the molecule stores the least potential energy, thus is in its most stable. Sccording to this formula : E pot.=Eattraction+Erepulsion and this graph: (figure I.19 in textbook)

Luminescence spectra.

Atoms:​ line spectrum: due to Ephoton = E2 − E1 = h * f Molecules: ​because discrete energy levels are split into vibrational levels, electrons will lose some of the excitation energy while they relax to ground state. This means there will be a spectrum of wavelengths that can be emitted.

Half-life and average lifetime of an isotope.

Average life time: the time required for the number of undecayed nuclei to decrease to 1/e of the initial amount. 1/lamda= lifetime The amount of time it would take for a number of undecayed nuclei to decrease to 1⁄2 of their original amount. T=ln2/lamda

Pressure-volume relation of the heart.

A→ end diastolic pressure and volumeB→ diastolic pressure (opens in aortic valave)C'→ systolic pressure→ increases in pressure decreases in volume C→ end systolic pressureD→ left arterial pressure

The Geiger-Müller counter.

Based on a gas ionization chamber. The difference is that the voltage is much higher that the one in the ionization chamber, thus every radiation will form avalanche of secondaries electrons which form maximum current (so it's insensitive to the energy of the radiation), but it is sensitive even to low energy radiation (due to high voltage) and counts the number of particles that interact with the device. Takes time for the system to reset itself (recombination of the iones) = dead time = 300 microsec.​video *disadvantages: a. long dead time b. not sensitive to the energy of the radiation

Electric signals measured on the body surface, for diagnostic purposes.

Based on dipole moment : d=Q*l EKG: a. a graph of the voltage vs. time of the electrical activity of the heart b. measured using electrodes placed on the skin EEG: records the electrical activity of the brain EMG: records the electrical activity of skeletal muscles by placing electrodes on diff. places on the skin

Why do we need to cool the x-ray-tube anode?

Because it heats up due to low efficiency in the conversion of high kinetic energy to x-ray.​

Why is dilution of blood is necessary in Coulter-counting?

Because the cells themselves do not conduct well, and so we dilute them with an electrolyte solution so changes in resistivity are noticed. Also, for practical reasons (e.g. we don't want the solution to dry up.)

Typical frequency and amplitude ranges of biological:

Biological signals include ECG, EEG, EMG, etc. ECG (ranges between 0.1 and 500 Hz, amplitude between 70 microV to 5mV) Intracellular voltage (0-10kHz, amplitude at 100mV)

How do you determine concentration by polarimetry?

Biots law: knowing the angle of rotation and the thickness of the tube with the solution

Biomechanical characteristics of bone and enamel.

Bones made of:a. organic substance: mainly collagen b. inorganic:hydroxyapatite Enamel composed of : o​nly inorganic​ molecules: mainly hydroxyapatite *​The inorganic composition​improves the strength of the bone/enamel. *enamel is the hardest substance in the body

How do you separate the red-blood-cell versus platelet signals in a Coulter-counter?

By integral discrimination (the size of the platelets is much smaller)

Planck's radiation law:

By studying the emission spectrum of black bodies, Planck introduced the concept that the energy emitted resulted from the vibration of atoms within the material. The vibrational energies have ​discrete values​(quanta=1,2,3), never a value in between. If the oscillator changes from E1→ E2, the difference between those energy states will be emitted. E2 − E1 = h * f . h​​= p​lanck's constant

How did we measure the visual acuity?

By using Landolt broken ring test we measure actual visual acuity by dividing the space in the c shape structure with the distance of the patient from the board.

How do you reduce external noise in scintillation counting?

By using a lead castle

What is the advantage of using x-ray density (D) in computer tomography?

Can be summed and a summation image can be constructed.

The Doppler-effect, Doppler-shift.

Change in frequency and in wavelength of the wave as a result of relative motion of the source and the observer. In US imaging, the source can be considered to be the reflecting surface of the examined organ. The change in frequency can be attributed to the velocity of the moving source. Therefore by studying the change in frequency, the velocity of the surface can be measured as a function of time.

Radiometric Quantities

Characterising the source: Radiant power (W=J/s) P = ΔE/Δt Radiant emittance and irradiance (W/ m2 ) M=ΔP/ΔA Einc=ΔP/ΔA inc Characterising the radiation: Radiant flux (W=J/s) IE= ΔE Δt Intensity JE = ΔIE/ΔA

Define the eigenfrequency.

Characterizes a freely oscillating system, independent of displacement

Definition of radiopharmaceutical.

Chemical agent or drug having radioactivity (labeled with radioisotope for diagnostic and therapeutic purposes).

Describe the process of focal accomodation of the human eye.

Ciliary muscles contract ​=​ suspensory ligament relaxes = lens becomes more budged ​= Radius decreases ​=​ Power increases

Define the attenuation coefficient.

Coefficient that depends on the intensity of radiation, type of material a​nd​density of the material.

Define the mass attenuation coefficient.

Coefficients that depends on the type of material and the radiation energy, but ​not​on the density of the material. μ/ρ=μm (unit cm^2/g).

Role of collimators in radiation therapy, gamma-knife.

Collimator is essentially a led plate with holes, allowing passage to gamma photons which travel along the axis of the hole. The size of the hole is a compromise between spatial resolution and sensitivity (the smaller the hole, the better the resolution however less photons can be detected) ● Scintigraphy; collimator with only one hole ● Gamma camera and SPECT: collimator with thousands of holes Gamma-knife-radiation treatment can attack brain tumor. Method: machine which emits high intensity of focused gamma beam precisely

Parts and function of the gamma-camera.

Collimator: only allows gamma photons of a particular direction to enter (thus allowing special resolution) → Scintillation crystal → PMT → Amplifier → Computer and electronics. Gamma photons are detected as they exit the patients body, their spatial location and intensity provide information on the organ of interest.

Basis ​of color sensing.

Colours are not a physical property b.c not all the colours can be defined by wavelength (e.g. brown). The human eye has 3 different color sensitive receptors (each is sensitive in a range of wavelengths (blue region,red-yellow region and green region). By mixing them in various weighting factors it is possible for us to sense any color.

a Wave interference.

Combination of at least 2 EM waves which encounter and result in: a. constructive interference: same phase (crest meet crest) or b. destructive interference: opposite phase (crest meet trough)

Biomechanics of respiration. (compliance, obstructive and restrictive pathologies)

Compliance is the distensibility of the lung tissue. It can be increased by reducing the amount of pressure needed to keep the alveoli open, this is done by surfactant which reduces the surface tension. Surface tension is the attraction force between water molecules (usually acts to reduce surface area on a surface of water). Surface tension is minimized by "surfactant" which is a liquid rich in lipoproteins. Restrictive diseases​are those in which the compliance of the tissue decreases. This can occur in premature newborns as the body has not yet produced surfactant to prepare for the first breath. The airflow in the lungs abide to the law of fluid flow: hagen-poiseulle's law Obstructive diseases: t​hose in which the radius decreases, which has a drastic effect on the flow rate and thus the oxygen supply.

The astable multivibrator and its applications.

Composed of two mono-stable multivibrators which stimulate each other. Produces a sequence of identical pulses. Application: Pacemaker.

Describe the circularly polarized light.

Composed of two perpendicular linearly polarized light waves with matching wavelength and amplitude, with a 90 degree angle (1/4 or 1⁄2 π ) phase shift.

What information can you obtain from an absorption spectrum?

Concentration of solutions (based on intensity change) and the electronic structure of the atom.

Energy levels of electrical conductors.

Conduction band and valence band with no forbidden band in between. (note, heating of a conductor results in lower conductivity)

Photoreceptors of the retina.

Cones 6.5 Million Daylight vision Colour sensitive located at center/fovea of retina Small convergence = high spatial resolution Lower frequency sensitivity Rods: 120 million twilight vision Not colour sensitive Located at retinal periphery Many rods per ganglion - higher convergence-lower resolution Higher frequency sensitivity

Spatial distribution of photoreceptors on the retina.

Cones are most densely packed in the fovea centralis (no rods) ​ visual acuity is highest there. Rods are located in periphery of the eye, where the visual acuity is lowest.

Interaction of beta negative radiation with matter.

Considered directly ionizing atoms by coulomb's force. Due to their minute mass, they are scattered on electrons, resulting in a zigzag path. Also: can cause breaking radiation (x-ray). Effective range: in air, a few meters in water: few cm (more penetration compared to an alpha particle due to its negligible mass and lower charge) Linear ion density: is lower than alpha particle (assume they have the same energy, beta particle will have to go through more distance to ionize the same no. of atoms)

The transport model and the Goldman-Hodgkin-Katz-equation.

Considers the continued diffusion of ions across the cell membrane while taking individual ion permeabilities into account P k . In a way it is a modified Nernst equation that gives the resting membrane potential more accurately.

The real gas.

Contrary to theoretical "ideal gas": Particles are not point-like, their volume is not negligible, consequently there is less volume available for motion. Interactions between particles arise and pressure becomes reduced. Additionally, behavior of real gases explains the possibility of condensation (transition from gas to solid)

Which refractive surface contributes the most to the refractive power of the human eye?

Cornea (43 dioptres), relative refractive index is highest

Refractive media of the eye. Image formation of the eye.

Cornea, aqueous humour, lens and vitreous body. Light rays converge on the retina.

The absorbed dose.

D = ΔE/Δm J/kg, gry. The amount of energy absorbed per mass. It is very difficult/impossible to measure due to the fact that even a lethal dose of 6gry corresponds to an unnoticeable temperature change.

Anomalous behavior of water.

Density-temp function → highest density at 4 celcius phase state → at some temp, at high pressure ice becomes water high surface tension , on hydrophilic surface water molecules ''climbing''. (floating water bridge)

Types of lasers.

Depending on wavelength; C02 (surgery), Krypton (ophthalmology), Ruby (dermatology).

Rules of image formation.

Depending on where the object is placed with respect to the focal point and double focal point, will determine the type of image that will be formed. ● Object is beyond 2F: image is real, inverted and diminished. ● Object is at the double focal point: image is real, inverted and the same size. ● object is between 2F and F: image is real, inverted and magnified. ● Object is at F: image is (virtual, upright and magnified at infinity) - Magnifying glass ● Object is closer than F: image is virtual, upright and magnified.

Stability of the atomic nucleus.

Depends on the ratio between protons and neutrons. Isotopes of an element have the same atomic number but differ in the amount of neutrons, so the mass number will be different. Isotopes can be stable or not stable. Unstable atoms will undergo radioactive decay, they will decay until they become stable.

Compare the depolarization and repolarization processes of skeletal and cardiac muscles.

Depolarization:Skeletal Muscle: Shorter action potential (1-2ms) and uniform duration. Cardiac Muscle: Longer action potential (250-400ms) and decreasing duration from the endocardium towards the epicardium. Repolarization:Skeletal muscle: negative repolarization of the same direction Cardiac muscle: positive repolarization front (cells which were depolarized later, get repolorized first)

The Stefan-Boltzmann law.

Describes that the emittance of a black body is proportional to the fourth power of the temperature:

Stokes drag law.

Describes the force drag acting on a particle being proportional to the radius of the particle.

Frequency response curve of the amplifier.

Describes the frequency dependence of the gain level. Every amplifier has cut off frequencies between which there is an optimal gain level.

The stochastic radiation effect.

Describes the radiation damage that can occur due to adsorbed dose. This method is valid for damage that can occur at low levels of absorption (there is no threshold), the probability of damage increases with the increasing dose.

Weber-Fechner law.

Describes the relationship between the intensity of the stimulus and the perceived sensation. Relative change of the stimulus is proportional to the change in sensation intensity. This law is only valid for sensations between 100-1000 Hz but fails at lower or higher frequencies.

Fick's II. law

Describes the spatial and temporal changes of the concentration gradient. Relevant when it is needed to consider the time dependence of diffusion (when studying metabolic processes, anesthesia, drug effects etc).

Biopolymer elasticity.

Determined by two parameters: Contour length (L):​the length of the biopolymer when it is stretched to its maximum. Depends on the number of monomers that compose it and it's length. Persistence length:​a measure of the stiffness of a biopolymer. If L>>>I: the chain will be flexible (DNA) If L<<<I: the cian will be stiff (Microtubule) If L=I: the chain will be semiflexible (actin filament)

What type of discriminator is used for acquiring the pulse amplitude spectrum?

Differential discriminator (allows us to differentiate the pulse rate values): which allows us to find the photo-peak

Wave nature of light.

Diffraction, interference, polarization are phenomena which prove the wave nature of light.

Thermodiffusion.

Diffusion that occurs due to a temperature gradient. Simple diffusion and thermodiffusion can compensate for one another in some situations (difference in temperature causes thermodiffusion which induces a concentration gradient which causes normal diffusion) LT = matter diffused across a unit area at a unit temperature gradient

Biomechanics of elastic arteries, distensibility.

Distensibility is defined as the change in vessel volume under pressure. When considering relative expansion over transmural pressure, the slope of the graph is the distensibility. At the beginning of the expansion, the elastic properties of the artery play a role. After a certain point, the collagenic properties take over and prevent overstretch.

How does the minimum wavelength of the x-ray spectrum change with increasing anode current?

Does not change

The electron microscope.​

Due to the small wavelength of the electron comparing to a photon the resolving power of electron based microscope allow us much higher resolution (abbe's formula and the de broglie relation )2 main types of electronic microscope : Transmitted electrons ( electron going through the sample and create the image on a screen) and Scanning EM (the scattered electrons create the image)the basic principles are: electron gun (tungsten filament which wired to an electric circuit, heats up and electrons shoot out due to their thermal thei thermal E), high voltage for the acceleration of the electrons(30kV-300kV), condenser electromagnetic lenses.

Applications of the Boltzmann-distribution IV. electric conductivity of semiconductors.

Electric conductivity of semiconductors (a type of crystal) depends on the number of electrons which are able to transition from the valence band through the "gap" to the conduction band. This number increases with T (it is the opposite in conductors). Using the Boltzmann distribution, we are able to calculate the fractions of electrons that are able to cross the "gap"/"forbidden band" = Δε : (n/n0)=e^-(Δε/kT)

Electro- and thermo optical phenomena in liquid crystals.

Electro: nematic liquid crystal (characterized only by orientation order) When they have electric dipole moment, the orientation of the molecule can be controlled by electric field. The change in the orientation manipulates the optical transmission of the layer, which we can utilize to manufacture displays from that material. Thermo:​ choleric liquid crystal (twisted nematic) changes its orientation as dependence of temperature (change the inclination​o​f its helix shape), thus the colour of the layer will change with different temperature (by destructive interference of one wavelength the crystal will transmit its complementary color). One of those applications is the ''contact thermography'', which provides information about e.g. regional inflammation by the increased temp. in that region which means that the crystal will transmit different colors.

Ionization methods in mass spectrometry: electrospray, MALDI.

Electrospray method: ​the sample is injected into the vacuum chamber by small droplets. The solvent evaporates, leaving smaller drops with higher ion density, the ions will repel into even smaller pieces "spray". Produces a steady supply of ions. MALDI:​ uses a short pulse laser to evaporate the solvent, leaving only the ions. Supplies ions in bunches.

Which is a better x-ray absorber: Al or Ag?

Element with the higher atomic number: Ag

FRET. (Fluorescence Resonance Energy transfer)

Energy transfers from donor molecules, without emission, to acceptor molecules when they form dipole dipole interactions. 3 main requirements: 1. they have to be in the right orientation 2. they have to be really close (efficiency of the FRET is proportional to the r​eciprocal ​of the distance btw. the donor and the acceptor ​by the sixth power!​) 3. spectral overlap btw. donor and acceptor. application: protein-protein interactions investigation

Entropy and its connections with order, thermal and configurational entropy.

Entropy can be defined as a state of "disorder" in a molecular system. Entropy increases as the temperature of a system rises (it is the extensive variable of heat flux). Configurational entropy is characterised as a flat part of the curve, where the temperature stays constant and molecular order changes. (which mean transition in state e.g ice-water)

The 1st law of thermodynamics and its applications for biological systems.

Essentially a law of conservation of energy, which states that energy cannot be destroyed, rather converted from one form to another. Biological processes rely on the conversion of energy, for example; in cellular respiration where food is converted to energy in the form of ATP.​ delta E = Q E + W Q E = mc delta T

Biophysics of physical examination IV.: Auscultation.

Examining the patient by listening using a stethoscope. Listening for loudness, pitch, tone, duration, temporal variation (rhythm). Related to sound generation, fluid flow and turbulence.

Biophysics of physical examination II.: palpation.

Examining the patient by touching.What do we palpate? Size, shape, location, rmness (elasticity, viscosity)biomechanics: distensibility ,the ability to stretch and expand under pressure, given mainly by collagen and elastin

Converting exposure in air to absorbed dose in tissue.

Every 1 C/kg exposure corresponds to 34 Gry absorbed dose in air. D= f* X (f34 J/C). If the mass attenuation coefficients are known: Dtissue/Dair=mu m tissue/mu m air

Huygens-Fresnel principle.

Every wave propagates so that each point of its primary wavefront serve as a source of secondary wavelets (of small amplitudes) that advance with the same speed and frequency as the primary wave.

Biophysics of physical examination III.: Percussion

Examination by tapping the patient in certain areas so differences from normal sounds can be observed. Sounds could be evidence of material content, shape and boundaries. Related to sound propagation and detection.

How do you determine the spring constant of a cantilever?

Experimentally by measuring the external force and the displacement andusinghook'slaw:F=-k*x

Extensive and intensive quantities and their relations.

Extensive and intensive are quantities that serve characterization of thermodynamic systems. Extensive: volume, mass, energy, charge, entropy, etc (quantities that can be change by splitting the system into 2 subsystems) intensive: density, temperature, pressure (independent of the size of the system) the product of the intensive and extensive quantities give us the change in energy: Wi = yi * delta xi

What is radius of curvature in case of a lens?

Flattener lens= larger radius of curvature. More rounded lens=lesser radius of curvature.

FRAP .

Fl​uorescence ​Re​covery after ​P​hotobleaching, is used to study the diffusion of molecules on the lipid membrane. The number of excitation and emission cycles is limited for fluorescent molecules, therefore they can be bleached. When the previously bleached area of the membrane "recovers", this is proof of the lateral diffusion.

Biophysics of physical examination I.: Inspection.

For the purposes of studying shape, morphology, structure and color. Exam with normal vision or using spectroscopic tools.

Interpretation of momentum of light: optical tweezers.

Formula for photon momentum: ρ=h/λ Optical tweezers ​utilize the momentum of the laser beam to control little refractive microshpere structures which can be bound to a biological molecule and be controlled by moving the laser.

Feedback amplifiers.

Fraction of the Uout (output) is added to the Uin (input) If the signal has the same phase like the input→ positive feedback: higher amplification (advantage) lower transfer band (disadvantage) ex: ultrasound generator If the signal inverted and than added to the input→ negative feedback: less gain (disadvantage) higher transfer band (advantage) ex: all amplifiers

Information coding by the action potential.

Frequency coding, where the increase in the voltage of the receptor potential will lead to higher frequency of the AP of nerve. gives information about:​•​modality (type) (depends of which nerve does the AP) • intensity (strength) frequency coding • duration • localization

Structure of the atomic nucleus.

Function as the center of the atom and is composed of protons and neutrons. Protons have a positive charge and they both have approximately the same mass (1amu). The mass number of an atom is defined as the sum of the protons and the neutrons in the nucleus, while the atomic number is defined by the number of the protons only! *the volume of the nucleus is extremely small comparing to the volume of the whole atom

Parts and function of filter circuits

Function: remove unwanted frequencies from the signal. Parts: resistor and capacitor (dependent on frequency)

Gain and gain level of the amplifier.

Gain: Ratio of the output and input amplitudes. Can be measured by power or voltage.Gain Level: the logarithmic scale of the gain - expressed in decibel unit.

Principles of selecting the isotope for diagnostics according to radiation type and energy.

Gamma radioactive isotopes ​are used most frequently for diagnostics due to their long effective range, low absorbance in body tissue, and their high energy, which makes them easily detectable. The energy of the gamma radiation​ should be high enough that it is able to penetrate the body and ​be detected,​ however not too high​, as it will be less effectively absorbed by the detector. In addition, low energy photos are more readily absorbed by the body, which is more damaging to the patient. That said, ​it should be absorbed to some extent​ (for contrast image). Activity needs to be high enough​ that sufficient photons can be detected.

Generation and detection of ultrasound.

Generation: based on inverse piezoelectric effect in which voltage pulse is applied on the crystal which become deforme​d​(and ''push'' the air particles next to it and by that generate ultrasound)detection: based on the piezoelectric effect: when the reflected signals from that examined body part compress and deform the transducer crystal, as a consequence voltage is formed (and being amplified by an amplifier)

Thermodynamic potentials.

Gibbs free energy: gives the energy available in isothermal, isobaric,​non isolated systems G = H − T S ● Himholtz free energy: gives the energy available in isothermal, isochoric,​non isolated systems F = E − T S ● Enthalpy: total heat absorbed by a system at constant pressure H = E + pV ● Internal energy: ΔE = Q + W

The Duane-Hunt-law.

Gives the minimum wavelength of x-radiation produced by braking radiation (Bremsstrahlung) as a function of voltage by this formula: minimum wavelength = k/U, k is a constant

Formation of Snell circle.

Grazing rays from lower index of refraction medium, refract at the boundary and make critical angles at the medium with the higher index of refraction, the critical angles form the borders of a cone of bright light.

Hagen-Poiseuille-law, flow resistance.

Hagen-Poiseuille-law- equation that describes stationary laminar flow of newtonian fluids in rigids tubes: (volumetric flow rate is dependent on the radius of the tube by the fourth power) flow resistance: directly proportional to the length of the tube (l), viscosity of the fluid and i​nversely proportional to the square of cross section area!

Differential amplifier of ECG.

Has two sensitive inputs and amplifies the difference of the two amplified signals.

Define hearing loss and ​overhearing.

Hearing loss is a higher threshold of hearing ​measured - J normal = loss

Determinants of blood viscosity.

Hematocrit (htc): the ratio between volume of cells and the total volume of the blood. Normal range: 0.4-0.5. Plasma viscosity depends on the plasma proteins. Plasticity of RBC; their ability to change shape. Aggregation of RBC Blood vessel diameter: with an increase above a certain point the blood's non newtonian behaviour it becomes more pronounced.

What elements are suitable as x-ray-tube anode material?

High melting point and high atomic number materials molybdenum (more common in medical diagnosis) and tungsten.

How to find the optimal ID setting of the scintillation counter?

Highest signal to noise ratio

What prisms are present in the Abbe-refractometer?

Illuminating prism (rough surface), measuring prism (flint glass with high index of refraction) and Amici prisms (restores dispersed light to white light or vise versa)

The Beer-Lambert law.

In a dilute solution, if the solvent does not absorb in the applied wavelength- absorption coefficient is proportional to concentration of solute thus: (measuring concentration of solute by measuring the absorbance of light in a given wavelength)

How do you determine concentration by refractometry?

In case of dilute solutions n1=n0+k*c

Applications of the Boltzmann-distribution II.: equilibrium and rate of chemical reactions. (The Arrhenius plot).

In chemical reactions, atoms must transition from one energy state A in which its energy is εa to B state in which its energy is εb. In an equilibrium, the distribution between those states is calculated: nA/nB =e^-(εA-εB/kT). The ratio na /nb = K (equilibrium constant) The Arrhenius plot illustrates a logarithmic relationship between the K and the 1/T. The slope of the graph gives the energy distribution between the two states.

Weighting factors in dosimetry.

In dosimetry, we have two types of weighting factors: radiation (type of radiation)- different radiation cause biological damage in different severities. Tissue: (which tissue are exposed) different tissues have different sensitivity to radiation optional info : Depends on the priorities of the measurement as each measurement technique has pros and cons. Pocket chamber dosimeter:​the same principle as the ionization chamber where the charge and voltage drop is proportional to the dose. Advantage is immediate readout. (not sure if they have energy level resolution..) Ionization chamber: ​Sensitive to the energy of the particle, and to the dose rate. However in Geiger-müller counter:​ simple and easily available, however it has a dead time so cannot be used for high counting rates. In addition, it can't distinguish between energies of nuclear particles. DLS: s​mall and reusable (good for personal dosimeters). However, no particle energy resolution. Semiconductors detect: ​much higher sensitivity than the ionization chamber because the ionization energy required is 3-5 eV.

Principal light rays

In geometric optics, image formation is made by emerging of 3 principal light rays (parallel,focal and center). In case of converging lens it looks like this:

Cost-benefit principle in isotope diagnostics.

In terms of radiation exposure, if the risk of not having the examination is higher than that caused by the radiation exposure, the procedure can be done. In terms of the isotope, criteria such as energy and activity should be with the patient in mind. However, certain criteria (high energy ionizing radiation of a certain dose) need to be met in order to achieve a reliable image/result.

The cross-bridge cycle of skeletal muscle myosin.

In the process of muscle contraction, ATP is hydrolyzed by the myosin heads, causing them to attach to binding sites on the actin filament. This is the "myosin cross bridge attachment". → power stroke occurs as the myosin head "pulls" the actin along its length, towards the m line, thus shortening the sarcomere.

Applications of the Boltzmann-distributionIII.: barometric formula.

In thermal equilibrium, we can measure the decrease in atmospheric density vs altitude by this formula: (density of gas is concentration per volume, so we practically measured the distribution of concentration) rho(h)/rho(0) = e^-mgh/kT

Law of Refraction (Snell's Law)

Incident and refracted ray together with the normal line (=optical axis) are all located on the same plane. Snell's law: (sin alpha/sin beta) = c1/c2 = n21

Effect of activity on the pulse amplitude spectrum of a gamma- radiating isotope.

Increase the value of the pulse rate (y axis)

How does the resonance frequency change if the spring constant is doubled?

Increases (by approx 40%) f0=1/2pi root (k/m)

How does optical rotation angle change if the sample concentration increases?

Increases due to the proportionality (biot law)

Principles of brachytherapy.

Insertion of a sealed source of radiation into the patient's body near or in the site of a tumor. Radiation will harm the tumor cells with low damage to surrounding tissue. Used for the treatment of cervical, prostate, breast and skin cancers.

Processing of pulse signals.

Integral discrimination:​ selecting signals higher than a certain amplitude. Used when filtering out noise for example in scintillation counter. Differential discrimination:​ selecting signals within a defined range. For example, used when counting according to size distribution (coulter counter)

Differential and integral forms of the decay law.

Integral: ΔN/Δt =− λN Differential: N(t) = N0e−λt N: number of undecayed nuclei, λ = decay constant 1/s

Sources of noise in the scintillation counter.

Internal: PMT dynode material emits electrons as a result of the voltage ​while there is no signal, at higher voltages = more noise.​ External: radiation from outside sources (walls, furniture, cosmic rays)

Dependance of irradiance on distance from the source

Irradiance is the incident radiation on a target. The dependence on distance from the source varies with the type of source. Assuming there is no attenuation: ● Point like source:​ irradiance is inversely proportional to the s​quared distance​from the source. ● Cylindrical source: irradiance is inversely proportional to the distance from the source. ● Planar source: irradiance does not change with increasing distance from the source (as long as the distance is increased perpendicular to the plane and is not greater than the linear size of the source) If the distance from the source is not perpendicular: Ei=Einc,maxCosalpha

Quantum yield of luminescence.

Is a measure of the efficiency of photon emission through fluorescence, which is the loss of energy by a substance that has absorbed light via emission of a photon. Defined as the ratio of the number of photons emitted to the number of photons absorbed.

Measurement of the absorption spectrum.

Is a measurement of absorbance (log(J0/J)) vs wavelength of incident light. The absorption maxima (can be more than 1) related to the electron excitation energy (E2-E1) which is characteristic for the molecular structure. Electrons of the atom are quantized. Thus, to change their energy state, the incident light is required to be in a certain frequency (energy): E2-E1 = ε = hf = h(c/lamda) *we can use absorbance to find conc. of diluted solution (beer lambert law)

Dynamic light scattering.

Is a method for analyzing solutions from which the hydrostatic diameter of a particle can be measured. Light is directed through a sample → scattering of the light occurs (relative to the position of the particles in the solution) → the intensity of the light is detected on the other side → intensity changes when the particles in the solution diffuse (brownian motion) → the change will occur faster or slower if the molecules are smaller, or larger respectively. → Information about the intensity is used to calculate the diffusion coefficient. Next, Einstein-Stoke formula will allow us to calculate the r (size of the particle)

Alpha decay.

Is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two.

Isobaric, isothermal, isothermal-isobaric systems.

Isobaric; at constant pressure, I​sochoric; at constant volume, Isothermic; at constant temperature. At constant pressure work done does not equal 0. Because W = pΔV so W= change in volume, thus all the energy is converted to change in volume and change in temperature. In Isochoric processes, ΔV = 0, so W = 0. Therefore ΔE = ΔQ and all energy is converted to heat. In isothermal processes all the energy will be invested in the work done.

The function of the semiconductor diode.

It acts as a one way valve for electricity. It is composed of n-type and p-type semiconductors. These are made by doping a semiconductor to achieve either free electrons (n-type) or holes (p-type). ​ ​The chemistry behind ​the diode requires for p-type doping to be a chemical with lower number of valence electrons than in the semiconductor. This will leave a vacancy which can be occupied by an electron (Al doping of Si). For n-type, an element with more valence electrons than the semiconductor is used (P doping of Si).

How does the absorption spectrum change if the sample concentration is doubled?

It doubles (due to linear relationship in Beer Lambert's law)

How does the matter flow density (flux) change if the concentration gradient is doubled?

It doubles, due to flicks first law: Jv=-Dxdeltac/deltax

How does the absorption spectrum change if the sample concentration is halved?

It halves (due to linear relationship in Beer Lambert's law)

How does the refractive power of human eye change during accomodation?

It increases due to the radius of the lens decreases

Definition of x-ray density and its significance in CAT-scan.

It is the absorbance in a voxel of the examined body part.In CAT scan, we scan from different angles and use summation, in order to measure densities of the voxels. Voxel densities are coded with grayscale or color and an image with depth information is produced.

Changes in the membrane potential as the function of time.

It's analog to charge or discharge of an RC circuit thus we can use those formulas for charging and discharge (look up said equations)

Principles of selecting the isotope for diagnostics according to half- life.

Its half-life should match the biological half-life (the time takes to the body to eliminate half of a concentration of a substance from the body) and also match the duration of measurement with the aim that all of them will be short as possible related formula: 1/Teff=1/Tphys+1/Tbiol

How does the voltage pulse amplitude depend on particle size in the Coulter-counter?

Its proportional, bigger particle will form higher resistance​,​ higher voltage pulse.

Volumetric flow rate, stationary flow.

Iv= ΔV/Δt the change in volume per second (unit: m3 /s ) Stationary flow: a flow that is steady in time.

Attenuation law

J=J0xe^-müx

What diffuses faster: a potassium ion or a virus particle?

K+ ion due to smaller diffusion coefficient (smaller size)

Interpretation of a typical isotope accumulation curve.

Lag time:​ time from introduction of isotope to uptake (characterises transport capacity) Ascending curve/slope:​ uptake of the isotope. T max: max activity, characterises the uptake and elimination ability of the organ (can be used to compare paired organs) Effective half-life/descending part of the curve: p​hysician + biological decay. From known physical decay value, biological decay can be calculated. Area under the curve:​ mean isotope content of the organ

Larmor-precession and nuclear magnetic resonance.

Larmor-precession: rate of precession of the magnetic moment of H+ around the external magnetic field. nuclear magnetic resonance: by emitting EM radiation in the same freq. of larmor freq. we can excite the nucleus in way that the net magnetization of it is 0 on the z axis (vertical) (seme numbers of elementary magnet spinning in +&-0.5 state) and is maximum on the x,y axis (transverse) (the elementary magnet are spinned in the same phase). *by measuring the relaxation of diff. nuclei give us information about it nature and it interaction with the surrounding

Types of ECG leads I.: bipolar leads.

Lead 1: Between left and right arm. Bipolar leads records the difference in potential between two active electrodes.

Types of ECG leads II.: unipolar chest leads.

Lead 2: Between left foot and right arm. It is a bipolar lead which records the difference in potential between two active electrodes.. Unipolar chest leads:​measures the potential difference between an active electrode and inactive electrodes. Six active chest electrodes are measured with respect to CT.

Types of ECG leads III.: unipolar limb leads.

Lead 3: is a bipolar lead b/w left foot and left arm. Unipolar limb leads refers to a goldberg augmented lead which is measured by subtracting a truncated CT voltage from one active limb lead. The CT is truncated by removing the lead we want to measure. Example:

Lens combinations

Lenses are combined in a compound microscope to form a system of two lenses: objective and eye-piece lenses. Image magnification can be manipulated by adjusting the distances between the lens and specimen as well as the distance between the two lenses.

Image formation on a curved surface

Lenses are curved surfaces on which light rays refract. If light rays meet, an image will form. The angle of refraction depends on the index of refraction of the medium. A diagram of this should begin with drawing a normal ray which passes through the center of curvature, and travels perpendicular to the surface- no refraction! The incident angle of other incoming rays needs to be measured with respect to the normal.

Thermotropic liquid crystals.

Liquid crystal: s​ubstance which possesses properties of both liquid and crystalline solid. 2 types of order can be defined liquid crystal: a. Transitional order- the center mass point of the molecule form plane b. orientational order- the axes of the molecule alin almost parallel with one another thermotropic- the order of the structure depends of temperature Application: contact tomography: the changing colors of choloresteric film on the patient's body can indicate inflammation area (higher temp. than normal=different color than normal)

Biophysics of hearing I.: the outer ear.

Made of the auricula, external auditory canal and eardrum The auricula steers the sound waves towards the external auditory canal, which then transmits the sound towards the eardrum. The eardrum is brought into resonance by the sound wave and will transmit the vibrations towards the middle ear.

What is the role of differential discriminator in Coulter-counting?

Mapping the size distribution of the particle

Define the surface density.

Mass that is behind 1cm^2 surface area of the absorbent (unit g/cm^2)

Macroscopic magnetization in MRI: spin-lattice relaxation.

Measure of the rate in which the magnetization vector returns from a horizontal position to a longitudinal position. During relaxation the excess energy is released into the lattice. Different tissues have different relaxation rates.

The gas ionization chamber.

Measures radiation dose by measuring the charges produced in a mass of air b/w the charged plates of the capacitor. The charges move toward oppositely charged electrodes → potential difference is detected and represents a current pulse. The size of the current is proportional to the energy of the incident radiation. e.g. gas ionization chamber: GM-tube (but it does not provide information about the energy level of the particle due to the avalanche effect)

The effective dose.

Measures the absorbance dose but it is taking into account the sum of the types of radiation (and their weighting factors, because different radiations have different biological damage severity) and the type of the organ which is exposed to the radiation (and its weighting factor which describe the probability of stochastic damage, due to the fact that different organs have different sensitivity to radiation) *The sum of all the tissue weighting factors is 1. *If radiation affects more than one organ, the effective doses of the organs should be summed. unit: sievert Sv=1 J/Kg

The exposure.

Measures the positive charge produced in the air with a certain mass by ionization, its unit C/Kg.​(​can be measured by ionization chamber) ​ Formula: X=Δq/Δm

Biophysics of hearing III.: Békésy's hearing model.

Mechanism in the inner ear, by which there is a spatial frequency coding. The basal membrane stretches from the oval window to the cochlea. The incoming sound vibrations will cause "surface waves" on the membrane. Depending on the relative location of the wave, different inner hair cells are stimulated, and this contributes to the frequency resolution.

Production of high-energy x-rays.

Medical linear accelerators accelerate electrons using a tuned-cavity waveguide, in which the RF power creates a standing wave. Some linacs have short, vertically mounted waveguides, while higher energy machines tend to have a horizontal, longer waveguide and a bending magnet to turn the beam vertically towards the patient. Medical linacs use monoenergetic electron beams between 4 and 25 MeV, giving an X-ray output with a spectrum of energies up to and including the electron energy when the electrons are directed at a high-density (such as tungsten) target. The electrons or X-rays can be used to treat both benign and malignant disease. The LINAC produces a reliable, flexible and accurate radiation beam.

Macrostate and microstate in thermodynamics.

Microstate:​ examination of the molecular state of the system and instant state (location of particles, velocity of particles, momentum) Macrostate: e​xamine the system as a whole (temp. pressure) in thermal equilibrium the macrostates stay constant while the microstate always changes!

Models of the atom (Dalton, Thomson).

Models of the atom:​ Democritus: "Atomos" (​uncuttable) atoms are the smallest article, and they have different shapes. Dalton:​ showed that matter was made of indivisible particles (atoms) which can not be broken down further. Thomson:​ discovered that atoms had electrons which were stuck throughout the positively charged substance (plum pudding) Rutherford:​ showed that all the positive charge was in the middle (nuclear model: atom has a nucleus) Bohr: ​the concept that electrons orbit around the nucleus (simplified concept used in chemistry for simplicity) Schrödinger:​ electrons don't move in concentric circles, rather orbitals can have different shapes which are not necessarily circular (quantum mechanical atoms). Rutherford and Chadwick: ​discovered protons and neutrons. (further quantum mechanical atoms)

What light source is used for polarimetry and why?

Monochromatic light is used because the specific angle constant is unique to a certain type of wavelength

What is myopia and how do you correct it?

Nearsightedness, rays from far objects form image in front of the retina, corrected using diverging lenses.

Resting transmembrane potential.

Negatively charged intracellular space and a more positively charged extracellular space. Higher concentration of K+ inside and a larger concentration of Na+ and Cl- outside.

Neutron radiation, proton radiation, the Bragg-peak

Neutron radiation occurs when an excited nucleus expels a neutron. Since neutrons do not carry charge, they do not ionize matter directly. Indirect ionization happens through collision and energy exchange between the neutron and the atom. Elastic scatter: ​neutron collides with another nucleus and transfers part of its kinetic energy to a proton, which is liberated and can ionize particles. Inelastic collision: ​as a result of the collision, the atomic nucleus will release excess energy in the form of a gamma photon or any particle. Neutron capture: nucleus absorbed the nucleus and an isotope is created (which then emits excess energy as a, b or gamma). Proton radiation a​cts very similarly to alpha particles. Large mass corresponds to shorter effective range. Bragg's peak:​ shows the relationship between penetration depth and amount of radiation deposited. For proton radiation, this peak occurs right before the proton stops.

What are the parts of a gamma-radiation pulse amplitude spectrum.

Noise, Compton region and photo-peak.

Energy levels of electrical insulators.

Non-metals. In band theory, insulators are said to have a valence band and a conduction band, however the gap between them, the "forbidden band" where electrons cannot exist, is "too wide", Δε > 3 eV, meaning that electrons are not able to cross it to get to the conduction band. Therefore, it does not conduct electricity.

Physical quantities used for describing the transport of matter.

Particle flow rate: number of particles per unit time I = ΔN/Δt unit 1/s Matter flow rate: moles per unit time I = Δv/Δt unit mole/s Particle flow density/flux J = ΔI N/ΔA unit 1/m3s Matter flow density/flux; J v = ΔI/ΔA unit mole/ m3 s

Phosphorescence.

Occurs during transition from a triplet state to a ground state, a slower luminescence than fluorescesce. Phosphorescence occurs by excitation of electrons from ground state → vibration and rotation to the lowest excitation state) --> intersystemic crossing into a triple excited state→ returning to ground state by luminescence.

Production of characteristic x-rays

Occurs when an electron with sufficient energy ejects an inner shell electron from the atoms of the anode. This state is unstable so an electron from an outer shell fills the vacancy and the excess energy is released in the form of x-ray radiation. Due to the fact that it's caused by quantum transition (b/w defines energy states) its spectrum is linear and characterizes the matter of the anode.

Total internal reflection and its applications.

Occurs when light is propagated from a higher refractive index thoward a medium with lower refr.index and with a larger angle than the critical angle. The critical angle is calculated by this formula: (1/sinBetac)= (n2/n1). Application: endoscopy

On what length scale is diffusion an effective transport process?

On a small scale

Heisenberg's uncertainty principle.

One cannot know all the parameters describing a particle at a given time. For instance, when momentum is calculated, there is more uncertainty about its location and vice versa. This is due to the wave nature of particles. ​For example:​ when waves are compressed enough into one space, to gain information on it's exact location, it will not be possible to know the exact momentum of that wave. In the case of sound, the more we know about its location in space, the less accurately its frequency is determined.

Imaging modes in sonography .

One dimensional A image (​amplitude modulation): single transducer, time/distance corresponding to amplitude changes. One dimensional B image (​brightness modulation): single transducer where the amplitude is represented a brightness pixels on grayscale. Two-dimensional B-image (​2-D brightness modulations): an array of transducers, manipulated so that the wave direction can be controlled (allows back and forth scanning without needing to move the transducer). M-image (motion):​2D image where a specific direction is selected and is plotted as a function of time, to obtain positional information. Reconstructed 3D image:​tomography Reconstructed 4D image:​ultrasound movie (reconstructed 3D images as a function of time)

Does a greater dB value always correspond to a louder sound?

Only if the frequency is the same

Signal amplification by hair cells

Outer hair cells have a positive feedback mechanism by which they contract, as a result of sound. When they contract (due to a motor protein "prestin") they move the tectorial membrane. This occurs at a narrow frequency range and causes a large amplification within that region.

Driven oscillation, resonance.

Oscillatory system that contains an external driving force which compensates for the dissipated energy. After some time, the frequency of the oscillatory system will equal that of the driving force, ​while the amplitude remains constant. Resonance occurs when the frequency of the driving force is close to the eigenfrequency of the system and results in extremely​large amplitude.

Osmosis, osmotic pressure, osmolarity.

Osmosis:​the phenomenon where solvent particles diffuse as a result of a concentration gradient. They will diffuse from an area of lower concentration to an area of higher concentration through a semipermeable membrane. Osmotic pressure:​example; a bag with sugar and water is placed inside of a vat of water. The bag is permeable only to water. The water is at a higher concentration outside the bag, therefore more water molecules from the outside will hit the bag barrier and enter it. This is diffusion. An increase in the water molecules inside the bag will cause an increase in pressure, t​his pressure difference between water on the inside and outside of the bag, is the osmotic pressure. Osmolarity or "osmotic concentration" r​efers to the amount of solute particles per liter solvent (taking into consideration the number of dissociated ions if applicable. # dissolved ions x molarity = osmolarity). Blood is about 300mOsm/L/ Medical applications: isotonic solutions are necessary to keep RBCs alive.

Explain the ECG curve.

P: Depolarization of the atria PQ: Delay due to the fibrous septa and the lower conduction of the AV node Q: Depolarization of the septa (from left to right) R: Depolorization of the ventricles S: Depolorization of the ventricles spreading upwards (towards negative electrode) T: Depolarization of the ventricles

Compare voltage and power gain

P=U^2/R Ap=(U^2out/Rout)/(U^2in/Rin)=A^2U*(Rin/Rout)

Scintillation counter II.: the photomultiplier tube.

PMT is a tube with a photocathode (which converts scintillations from the crystal to electrons (photo effect). These electrons are multiplied on the dynodes before reaching the anode. The electrons are accelerated by a V through the tube, every collision with a dynode produces secondary electrons. The multiplication factor corresponds to the number of secondary electrons, usually 3-4, so for 10 dynodes = 3^10

Respiratory biophysics I.: partial pressure, Henry's law.

Partial pressure referees to the individual pressure belonging to substituent gas particles within a mixture, the total pressure is a sum of the partial pressures. Henry's law: a​t a constant temperature, the amount of gas dissolved in a given volume is proportional to the partial pressure.

Parts and working principle of PET.

Parts: positron radiating isotope ring detector (scintillator crystal, photomultiplier) PET is a functional imaging method, by providing information about the distribution of the ​positron​radiative isotope. Emitted positrons interact with electrons and form annihilation, which will produce 2 gamma rays with an opposite direction, which will be detected by the ring detector.

Parameters of a pacemaker pulse: period, amplitude, duty ratio, energy.

Period: approx. 1 secAmplitude: 0.8-5 VDuty Ratio: Active time/total period Energy: V^2/R(tissue)

Classification and comparison of signals.

Periodic (e.g. sinusoidal wave) // non periodic (e.g. a pulse) stochastic signal Electric (voice which amplified through megaphone ) // non electric (voice) Analog (e.g. audio) // digital (e.x signal which stored in code in electronic device) A quantity that is used to compare the magnitude of 2 signals in decibels: n=10*log(P2/P1) provides the energy difference. Practically we measure the voltage difference n=20*log(U2/U1)

How does x-ray absorbance depend on the atomic number of absorber?

Photo Effect is the dominant attenuation process: photoeffect = micro m - Z^3

Which attenuation mechanism dominates in x-ray diagnostics?

Photoeffect

Photon energy, the eV scale.

Photon energy is calculated as the product of planck's constant and the frequency. E = h * f or E = h * c/λ The energy is the formula is given in joules, but is often described using electron volt.Electron volt: the amount of kinetic energy in an electron that is accelerated in an electric field of one volt. 1eV = 1.6 * 10^−19 Joule

Beta positive decay.

Positron and an antineutrino are emitted. A proton in the nucleus becomes a neutron, which stays in the mother nucleus. Thus, the daughter nucleus will have an atomic number one less than the parent nucleus but the same mass number.

Parts and function of Tc-generator.

Practical machine which produces gamma radiation isotope from a ''parent'' isotope which has relatively long half-life. Parts: lead container, saline container, generator colomb, Tc(m)-elute container​.

Primary and secondary bonds.

Primary bonds:​ include covalent (non metal-non metal), ionic (metal-non-metal) and metallic (metal-metal) bonds in which electrons are shared between atoms, in order to form a more stable electron configuration. ​Secondary bonds:​ are weaker because there is no electron sharing, rather bonding occurs due to instantaneous dipoles between two atoms. Van-der waals and hydrogen bonds are secondary bonds

Structure and elasticity of DNA.

Primary structure: - esters of nucleotides forms with phosphoric acid - each nucleotide contains heterocyclic base (contain N) and pentose (deoxyribose) - bases= pyrimidine/purine derivatives - pyrimidine base: thymine, cytosine - purine: guanine, adenine *in the polynucleotide chain, deoxyribose connects with phosphodiester bonds. --> sugars backbone of the chains *sugar= most flexible component in the nucleic acid. 2. 2 independent DNA chains form a double helix with antiparallel orientation by H-bonds b/w the bases of each dna strand. There are 3 different conformations (A-DNA, ​B-DNA​is the familiar one, Z-DNA) tertiary structure: nucleosome (dna-histone protein)

The bound electron, quantum numbers.

Principal quantum no (n): 1, 2, 3, 4.. Angular momentum quantum no (l): n-1 Magnetic quantum no (m1): -l...+l Spin quantum no (ms): +1/2, -1/2

Scanning probe microscopy.

Principle: a method which can form an image of an atomic size object by detecting various interactions depending on the design probe. e.g.: AFM which measures the van der waal's force btw. the probe and the sample (the probe attracts to the sample until a certain distance, and after a certain value the force of repulsion takes place. The deflection of the cantilever is held constant by lifting or lowering the cantilever.) Composed of: a probe which is connected to cantilever and a laser beam that point on the probe and reflect into detector (measures the change in the position of the probe) 2 modes: contact, oscillating

Laser: induced emission.

Process by which the emission is stimulated by incoming photon → the incoming photon is amplified. Laserer materials are those for which there are 3 energy levels; and one of them should be of "long lifetime", meaning that the electrons will stay in that state for longer. Electrons are "pumped into this level" (population inversion), emission from this level spontaneously is unlikely, thus it is achieved by ​induced emission.

Interaction of gamma radiation with matter I: photoeffect.

Process in which gamma-photon removes an electron from the inner shell of an atom ​while being absorbed, the Ekin of the electron = incident of the photon energy (approximately). All the initial energy of the gamma photon is completely transferred to the electron.

Interaction of gamma radiation with matter III: pair production.

Process in which sufficiently high energy gamma photon (1.02Mev) is absorbed near the nucleus and an electron and a positron are created by that energy. [a short while after, they will collide by a process called annihilation and 2 gamma photons (of 0.511Mev) will be released at an angle of 180 from each other ]

Processivity, ​typical force range and working distance of motor proteins.

Processive motor ​proteins are characterised by duty cycles which are larger than 1. Meaning that they remain attached most of the time. Ex: Kinesin, DNA and RNA polymerase.force range: ​piconewton scaledistance:​nanometer scale

Mass spectrometry in medicine: proteomics, diagnostics, oncoknife.

Proteomics: ​determining the nature of the protein by studying the peptides on a mass over charge chart and comparing it with other databases,Diagnostics:​studying samples of blood or urine for chemicals that would indicate poisoning or pathological conditions. Oncoknife:​a surgical knife which is connected to a mass spectrometer and is able to provide information on molecular composition of tissue in real time. Very useful because it could indicate tumorous tissue that should be removed.

The bistable multivibrator and its applications.

Pulse generator with two stable states, which requires a trigger to switch from either of the states. Application: on/off switches and memory units.

Relative depth dose

Ratio of an absorbed dose in certain depth within the body to an absorbed dose at a reference point of the body central ray. The higher the ratio, the better (= More dose to a cancerous tissue in the depth vs lower dose to an healthy tissue.)

What is visual acuity and how do you measure it?

Ratio of the normal limiting angle = 1 min (smallest angular view of separated points than can be distinguished) to the actual limiting angle.

Define the signal-to-noise ratio.

Ratio of useful signal and useless noise, higher value = more accurate reading

Real fluids: Newton's law of friction.

Real fluids are those in which friction exists between its layers. Fluids which adhere to this law are "Newtonian fluids". The law states that the force needed to move one layer (of fluid) over the other, is proportional to the viscosity, the area and the velocity gradient.

Characterize the image of an object placed outside the double focal distance of a converging lens.

Real, diminished and inverted

Characterize the image of an object placed between the single and the double focal distance of a converging lens.

Real, magnified and inverted

Damped free oscillation.

Realistic oscillation where there is a loss of energy due to friction and the amplitude decreases.

lens equation

Reciprocal of the image distance plus the reciprocal of the object distance, gives the reciprocal of the focal point, which equals the refractive power.

The Ideal gas.

Refers to non-realistic gas composed of molecules which follows the kinetic gas theory. The parameters characterising the state of the gas are connected by this formula : PV=NkT (temp. in kelvin)

The Donnan-equilibrium.

Refers to the​equilibrium state i​n which there is an​uneven distribution​of ions across a membrane, and the particles are not able to diffuse because of impermeability of the membrane. In cells this equilibrium is realized by the sodium potassium pump, which actively controls this uneven distribution.

How does refractive power of a lens change if its index of refraction increases?

Refractive power will increase

Changes in the flow velocity in the blood vessel system.

Related to pressure decrease and/or total area increase due to the continuity equation

What is the gain level if the voltage gain equals 1000?

Resistance of the capacitor in an AC circuit, is inversely proportional to frequency (unit: Ohm)

Reynolds-number, critical velocity.

Reynolds number (Re=1160 in a rough walled tube), is a constant used to calculate the critical velocity at which flow becomes turbulent.

Boltzmann's definition of entropy.

S = k * lnΩ where S = the entropy (the extensive quantity of heat) and where the number of microstates which belong to a particular macrostate are.

What solution is used for blood dilution in Coulter-counting?

Saline solution, for optimal osmotic pressure (keep the RBCs in their natural size) and for good conduction (NaCl)

How do we resolve 3D structure in CT scanning?

Scanner and detector are rotated around the examined area and thousands of summation data is collected. Elementary densities are displayed on a grayscale.

Parts of the scintillation counter.

Scintillation crystal, photomultiplier tube, electronics with amplifier.

Protein-stabilizing interactions.

Secondary: ● Hydrogen bonds ● Electrostatic interactions ● Van Der Waals interactions ● Hydrophobic/Hydrophilic interactions Covalent ● Disulfide Bridges (Between Cysteine side chains). Hydrogen bonds can orient in two ways:Parallel coupling:​which requires a very high amount of force to breakSerial coupling:​which in comparison requires much less force to break.

Define the integral discriminator.

Signal selecting device which ignores pulses below a certain amplitude, filtering out noise ​​improving the signal to noise ratio.

SPECT.

Single photon computed emission tomography: gamma radiopharmaceutical is injected into the body --> the detector gamma camera is rotated around the body axis → gamma photons are detected → multiple 2D images from multiple angles are acquired → Images are computed using tomography algorithm → 3D image is yielded.

Name the parameters influencing the value of diffusion coefficient.

Size and shape of the particle as well as the temperature and viscosity of the medium. Can be calculated for spherical particles: D=kT/6 pi n r

The crystalline state (unit cell, crystal defects).

Solid which is arranged in a long range of periodic order and is composed of structural units which call the ''unit cell'', the latter making a bigger symmetrical structure called ''crystal lattice''. As in gases, we have a classification of ideal and real crystals. While ideal crystals have infinite periodic spatial sequences of identical structural elements, real crystals or microcrystalline keep their identical spatial sequence only in their microscopic scale and instead of being made of the same crystalline structure (same elements, same type of lattice) they appear in various sizes and orientations of building blocks. Crystal defects: a. point defects = occur on a single lattice point (types: empty space, doping, an extra atom btw. the lattice point) b. line defects = rows of atoms are arranged inconsistently c. surface defects = boundaries which separate the crystal into regions with different orientations. defects can cause fracture in the crystal.

Production of isotopes.

Some isotopes are unstable, therefore they emit radiation. Thus radiation can be harvested for medical usage. Isotopes are produced in nuclear reactors, by​bombardment of a stable nucleus with high energy particles.​ However​, Tc generators​ are also used, specifically, when a gamma radiation isotope of a short half life is required.

What sample can be measured with the Abbe-refractometer?

Solutions with an index of refraction lower than that of the measuring prism (because we want snell's window)

Factors influencing the value of index of refraction.

Solvent concentration in dilute solution, the frequency, temperature (makes fluids less viscous so light travels faster)

Zeeman-effect​_

Splitting of the energy levels of an atom when placed in a static magnetic field.The level of splitting depends upon the magnitude of the external applied magnetic field. By applying electromagnetic radiation of a certain frequency, transitions between energy levels of a proton will be induced. This is also called "resonance condition".

How does the average distance travelled by a diffusing particle depend on time?

Square root function (Distance average ^2 =6 * D * t)

Ion currents during action potential.

Steps: 1. stimulus above threshold 2. voltage-gated channels of Na(+) open = Na+influx 3. voltage-gated channels of k(+) open = k+ outflux 4. voltage-gated channels of Na(+) inactive (partial) 5. voltage-gated channels of Na(+) close 6. voltage-gated channels of k(+) close t is approx. 1-5 ms (muscle and neuron) U is approx. 100 mv

Steps of sensory signal transduction.

Stimulus → Receptor potential (on sensory receptor) → Action potential (on nerve cell) → CNC

Viscoelasticity II.: stress-relaxation, energy dissipation.

Stress-relaxation is a property of visco-elastic materials (such as muscles), where if the strain is held constant, there will be a decrease in stress as a function of time. (example: when stretching a muscle, the stress will decrease when the strain is held constant). This decrease in stress can be expressed by this equation: phi = phi0*e^-t/Rho, rho = time constant. Stress dissipation/hysteresis: occurs when the path to recovery after deformation is different than the path to deformation. The energy difference between those two paths, is the energy loss or dissipation.

Biomechanics I.: Stress-strain diagram and its ranges.

Stress: ​amount of force per area: F/A (N/m^2), Pascal. Strain:​measure of length deformation from original length: m/m (dimensionless). Stress is proportional to strain Proportional region:​ where the stress is proportional to the strain, and there is no hysteresis (part of the elastic region). Elastic region:​reversing the stress will result in recovery of the length, no permanent deformation occurs. Hysteresis is possible. Plastic region: a​fter this critical threshold, irreversible deformation occurs.

The equivalent dose.

Takes into account that different types of radiation influence the biological tissue in different severity associated with a particular dose. Unit: Sievert=1 J/kg, Wr= radiation weighting factor (defines how many times greater the biological effect with a certain type of radiation comparing to a gamma radiation)

Define transmittance.

T=J/Jo (*100%)

The direct and indirect effects of ionizing radiations.

Tadiation ionizes a molecule such as DNA causing mutations. Indirect effect: radiation ionizes water molecules in the body, causing free radicals, which then damage molecules such as DNA.

Scintillation counter I.: the scintillation crystal.

Thallium activated (doped) NaI crystal or NaI (Tl) are widely used as scintillator crystals. They are made by insulators which have intermediate energy states thanks to Tl doping. The material of the crystal absorbed the energy of the radiation (e.g. absorbed the kinetic energy of the primary electrons) in the form of excitation energy of the scintillation. The electrons return to their ground state by emission of fluorescence photons (blue in our case). *note: to be able to detect the scintillation, the scintillator has to be transparent to the emission wavelength .​

Define optical activity based on the refractive index.

The ability of chiral molecules to rotate plane polarized light due to refractive index being different for the right or left handed circularly polarized light (higher refractive index ​= slower propagation = change in phase of one of the components)

Coulter principle.

The ability to count and measure the size of particles using an electric circuit. Particles are moved through a small aperture, their presence causes a narrowing of the aperture, which leads to an increase in resistance.By using constant I, According to Ohms law (U= I * R), when R increases, U increases and pulse is generated.

Explain the energy dependence of mass attenuation coefficient in case of lead (graph in formula collection).

The absorbance mechanism depends on the energy (for ex at lower energies photo effect is more likely)

Absorption of ultrasound.

The absorption of US is important because some of the energy is dissipated in the form of heat. General attenuation law is valid: Where μ = absorption coef f icient ~ F requency Absorption ability of tissues is characterised by the "damping" unit dB/(cm MHz)

Define Biot-law.

The angle of rotation can be calculated using the specific angle of rotation (constant depending on wavelength and temperature), the concentration and the thickness of the solution.

Fundamentals of thermodynamics II.: change of internal energy.

The change in internal energy is the sum of the supplied heat and the work done on the system. delta E = Q E + W Q E = mc delta T

Determination of the biological half-life of an organ.

The biological transport rate and its elimination from the target organ. Provides important information about the function of the organ. 1/Teff=1/Tphys+1/Tbiol

Wien's displacement law.

The black body radiation curve for different temp. peaks at a wavelength that is inversely proportional to the temp. ( high temp.=low wavelength) black body radiation v.s. wavelength curve:

Matter waves.

The concept that matter can exhibit wavelike properties. Hypothesis by De-Broglie, who introducedthe wavelength for matter: wavelength = h/p = h/mv Where it equals the ratio of planck's constant and the momentum of the particle.Example: Davisson-Germer experiment which proved that electrons, which were scattered, formed diffraction patterns.

Energy levels of atoms and molecules: the Jablonski diagram

The diagram depicts the ground state which electrons strive to be on, and the excited states to which electrons can jump to if given the correct energy quanta. Excited electrons will undergo "internal conversion" in which they rotate and vibrate until they reach a semi-stable state S1 (following Kasha's rule), only from that state will they relax to the ground state. If they emit light during this relaxation it is called fluorescence. Intersystem crossing occurs when the electron jumps to the triple state. From the triple state to the ground state radiative relaxation is termed phosphorescence (slower process).

How do you calculate the accomodation power of human eye?

The difference between the largest and smallest powers of the eye

Interpretation of the color of light.

The different colours are the perception of our eyes for different frequency (different of EM radiations in the visible range) *complementary colour: object absorbs color and transmits other colour which the sum of them is the white light

The diffusion coefficient. Einstein-Stokes-equation.

The diffusion coefficient gives the amount of material diffused​ across a unit area in a unit time driven by a concentration drop. unit m^2/s. it depends on the size and the shape of the particle, on the interaction with the solvent and on the viscosity of the solvent. Einstein-Stokes-equation: valid for​spherical particles​in a viscous medium and used to calculate the diffusion coefficient.

Define the tenth-value layer thickness.

The distance at which the radiation is attenuated to 1/10

The pulse-echo principle.

The distance b/w reflected boundary and the transducer can be calculated from the time elapsed b/w emission of the ultrasound pulse and its echo, if we know the velocity of sound in the given medium by that formula:​ d= c* delta t /2

Define the half-value layer thickness.

The distance within the material at which the radiation is attenuated to its one half.

Typical dose values and dose limits.

The dose limits: The lethal dose is 4-6Gy. ● Max limit for the body: 20mSv/year (10 micro sievert per hour) for the body. (for the skin and limbs the limit is 500mSv/year). Characteristic dose values: ● 2.4mSv/year from background radiation. ● X-ray image: 0.2-1 mSv. ● CT scan: 2-8 mSv.

Luminescence: excitation and relaxation.

The emission of excess energy, from excited electrons, in the form of light (cold emission, as opposed to thermal emission/incandescent emission). Many types of excitation: thermo, bio, photo electron. Process: Absorption of external energy → Excitation → Emission of energy in the form of light. Types of relaxation: Fluorescence:​ if the luminescence stops as the excitation stops (the relaxation step takes 10−8 seconds Phosphorescence: ​if the luminescence continues for much longer (minutes). Requires intersystem crossing into the triple state (from which there is a lower probability that the electron will relax).

Respiratory work.

The energy invested to inhale and exhale a breathing gas possible to calculate by:W=P*V(change)

The 3rd law of thermodynamics.

The entropy of a pure crystal at 0K is 0. This law can be explained from the definition of entropy; which is the number of microstates which characterize a given macrostate. Atoms in a crystal at temperatures higher than 0K would differ in their vibrational energies, thus at any given time there could be different positions (microstates) of atoms, which means the entropy is greater than 0. However at 0K (hypothetical temperature), thermal motion and thus vibration of atoms would not exist, therefore there would only be one microstate for the macrostate of the crystal. Using Boltzmann's equation; S = k * ln(Ω) where Ω =1 ln(1)=0, thus S=0.

Structure and types of motor proteins.

The globular head at the N-terminus is the motor domain(ATPase) and provides a specific binding-site for the respective cytoskeletal filament. The C-terminus binds to the surface that is being moved classification based on the substrate they bind to: 1. actin cased: myosin 2. microtubule based: kinesin, dyneins,dymatize 3. DNA & RNA polymerase 4. rotatory motors: found in the mitochondria,flagellar motor 5. mechano-enzyme: ribosome

Electrical description of heart function.

The heart is regulated by an electrical system of the specialised cardiac cells. The electric pulse is generated by the SA node → travels down the right atrium; atria contract → Reaches the AV node; slows down → Travels through the bundle of his→ Right and left bundle branches to stimulate the ventricle.

Fundamentals of thermodynamics III.: types of energies, internal energy and its components.

The internal energy is the sum of the individual energies of the particles that compose it. Electric, vibrational, rotational and interatomic interaction. *the internal energy does not include the kinetic or potential energy of the system as a whole.

Luminescence lifetime.

The inverse of the rates of all transitions (radiative + non-radiative). The lifetime: τUsed in distribution formula:

Interaction of alpha radiation with matter.

The linear ion density, which is the amount of ions produced over a certain length a , decreases after the particle has lost its energy. (The energy required for ionization is 34eV). The effective range is the distance covered by a particle until it's energy is lost. This value is longer in air (2-9 cm) than in liquid or soft tissue. (1-10mm). Things to consider: ● Mass (influences its velocity) ● Charge (influences its interaction with other particles, and its linear ion density). **In the case of beta particles, both mass and charge are much smaller, therefore it will have a higher effective range, but a much lower linear ion density (that said, a and b particles will produce the same number of ions, because b particles can travel further).

How can you determine the gamma energy of a radioactive isotope with a scintillation counter?

The location of the photo-peak on the x-axis indicates the energy of the gamma photon. The voltage of the photo-peak is proportional to the energy of the gamma radiation. Because during the photo-effect all the energy of the photon is converted to the primary electron.

Which part of the x-ray spectrum is attenuated by filtering?

The long wavelengths (to avoid unnecessary radiation absorption, these photons and may hurt resolution due to scattering)

Circulatory biophysics: function of the blood vessel system.

The maintenance of the homeostasis in the body, by maintaining pH levels and Glucose level.Also acts to transport metabolites, gases, hormones and heat. Must work in steady slow state to allow diffusion processes across the membrane. Gas exchange occurs at the interface between capillaries and venules.

What is the absorption maximum characteristic of?

The molecular structure of the material (electron excitation energies of that material). We use it to measure concentration of a material in a solution.

How does refractive power of a lens change if its radius of curvature increases?

The power decreases

How does refractive power of a lens change if its radius of curvature decreases?

The power increases

ALARA-principle​ As​​Lo​w ​As​​Re​asonably ​Ac​hievable

The principle state that we should aim to reduce the exposure to the minimal by: a. spending minimum time near the source b. the distance from the source should be maximalc. a person who is dealing with radioactive material should be c. wear a protective shield. d. the source must not cause any deterministic effect e. justification: cost/dose, radiation damage/radiation protection in inverse proportionality

The deterministic radiation effect.

The probability ​of radiation damage occurs above a certain threshold dose. Beyond the threshold, the probability dramatically increases. The severity of the damage a​bove the threshold is proportional to the dose (e.g Cataracts- loss of transparency of the lens)

Gamma decay.

The product of an excited nucleus as it tried to achieve a stable state. The unstable nuclei that undergo gamma decay are the products either of other types of radioactivity (alpha and beta decay) or of some other nuclear process.

Magnification in the light microscope.

The product of the magnifications of the objective lense and the eyepiece lense: M=I/Ox(I'/O')=MoxMe

Propagation of the action potential, refractory period and its role.

The propagation has a special exponential decay because of its RC circuit nature. Refractory period is a time in which the cell is not able to respond to the stimulus by generating an action potential. It is characterised by an absolute refractory period and a relative refractory period (where a stimulus of much higher magnitude would be required to generate an action potential).

Protein folding.​

The protein funnel hypothesis assumes that protein's native state corresponds to its free energy minimum under the solution in physiological condition.

Effect of anode voltage on the pulse amplitude spectrum of a gamma-radiating isotope.

The pulse-amplitude spectrum shifts to the right to higher values (x axis)

Franck-Hertz experiment.

The purpose of the experiment was to prove Bohr's atomic model, which states that electrons exist in quantized states within the atom. In the experiment, using a tube filled with Hg, an electron emitting cathode, a grid and an anode, it was proved that in order to interact with the Hg atoms, a specific discrete amount of energy had to be given to the electrons, by means of voltage. By measuring the current at the end of the tube, it was possible to measure how much of this energy was imparted on the atoms, and how much was left over, and thus the quanta of that particular atom.

Chemical shift.

The shift in the spectral line as a function of chemical surroundings of any given nucleus. This is caused because the e clouds surrounding atoms will have an effect on how that atom experiences the external magnetic field, which will change its resonance frequency accordingly.

Limit of resolution of the light microscope.

The smallest noticeable distance btw 2 points. Abbe's formula: omega = 0,61x(wavelength/nxsinomega) color which the sum of them is the white light

Changes in the membrane potential as the function of space.

The space constant describes the propagation of action potential, in terms of the distance it travels before it is attenuated to 37% of its original value. Formula for the space constant: Rm = transmembrane resistance. Ri = intracellular resistance Larger space constant provides a larger distance of propagation, can be improved by increasing Rm as seen in the myelin sheath of axons

Biomechanics III.: Laplace-Frank-equation.

The tangential stress is proportional to the intramural pressure and the ratio between the inner radius and the wall thickness. Relevant when considering hypertension, as the increased intramural pressure will cause an increase in the tangential stress, which will cause an increase in the inner radius and a decrease in the wall thickness, thus Aneurysm is formed. This dangerous cycle continues and may cause rupturing of the wall.

Changes in the total cross section of vessels in the circulatory system.

The total cross sectional area increases in the circulatory system, from 2.5cm^2 in the aorta to 2500cm^2 combined area of the capillaries. According to the continuity equation, this leads to a drop in the flow rate. As the cross sectional area of the veins increases slightly, the flow rate does the same.

Propagation of ultrasound in air and in the body.

The velocity of sound depends on the media in which it propagates, specifically on the density and compressibility of the medium. Compressibility:​ K = -deltaV/V/deltap Speed:​ c = 1/root rho K How far it propagates depends on the attenuation along the depth it travels. μ = absorption coefficient ~ Frequency

Lyotropic liquid crystals.

Their order is affected by the concentration of their components (they change order depending on how many of them there are). Their components are amphiphilic molecules which form ordered structures in the presence of a solvent. Phospholipids, with their polar and nonpolar ends, form a membrane or micelles depending on their concentration.

Electrochemical potential.

There are two components; charge difference/ potential across the membrane and chemical difference/ potential.

Medical applications of thermal radiation.

Thermography i​s a test that uses an infrared camera to detect heat patterns and blood flow in body tissues. Digital infrared thermal imaging (DITI) is the type of thermography that's used to diagnose breast cancer. (note. thermotropic liquid crystals are used here)

Optical properties of crystalline materials.

They are anisotropic, which means that their physical properties are dependent on the direction of the measurement related to the orientation of the atoms in the crystal. Due to this, light will propagate with different velocities in different directions.

Which one is louder: 50 Hz, 120 dB vs. 1 kHz, 110 dB (formula collection, isophone curves)

They have the same loudness value

Define the human hearing range (thereshold of hearing, threshold of pain, frequency limits).

Threshold of hearing is the minimum intensity at various frequencies that a human can hear. The threshold for pain is the highest intensity that a human can hear for a short time without damage to the ear (10 W/m^2). The frequency range is between 20Hz-20kHz.

Respiratory volumes and capacities.

Tidal volume: normal volume when exhaling and inhaling Inspiratory Reserve: max volume during forced inspiration Expiratory Reserve: max volume during forced expiration Vital:​includes tidal and the reserves.Total:​includes the vital plus the residual volume.

X-ray contrast media.

To produce an image, the intensity of the radiation leaving the body is measured. Therefore, contrast in imaging depends on the difference in absorbance of the x-radiation, thus on the attenuation coefficient of the media (which is a product of the mass attenuation coefficient and the density). The two main absorption processes are photo effect and Compton scattering. Photo Effect has a high dependency on atomic number.

What is the function of the monochromator?

To provide lights of specific wavelengths for measurement of concentration within the max absorbance.

What is the role of Amici prism?

To restore dispersed light into white light (or vice versa)

Turbidimetry and nephelometry.

Turbidimetry: Turbidimetry is involved with measuring the amount of transmitted light (and calculating the absorbed light) by particles in suspension to determine the concentration of the substance in question. Amount of absorbed light, and therefore, concentration is dependent on; a) number of particles, and 2) size of particles. Nephelometry: at low intensity of scattered light, measures the intensity of scattered light. (linearly proportional to concentration) Since the amount of scattered light is far greater than the transmitted light in a turbid suspension, nephelometry offers higher sensitivity than turbidimetry. • The amount of scattered light depends on the size and number of particles in suspension *how do we differentiate btw. light scattering and absorbance ?*

phase contrast microscope

Turns phase differences (to which the eye is not sensitive) and converts them into amplitude differences which translate to intensity differences I = A2 (which the eye is sensitive to). Useful for studying living cells, with no staining

How much louder is a 80 dB versus a 70 dB sound at 1000 Hz?

Twice as loud

Muscle biophysics I.: twitch, summation, tetanus.

Twitch:​ elementary mechanical response of a muscle to a stimulus contain contraction phase and relaxation phase. Summation: ​more frequently stimuli increase the conrasile force→ muscle is already partially contracted when the next stimulus arrives and contractions are summed. Tetanus:​ A sustained contraction that lacks even partial relaxation

Muscle biophysics II.: isometric and isotonic contraction.

Types of muscle contractions Isometric:​ when the muscle isn't able to shorten, but the tension on the muscle increases. Isotonic:​ tension remains unchanged (constant) while the muscles length changes.

Calculate the value of R(III) if R(I)= 0.2 mV and R(II)= 1 mV in the standard ECG leads.

Un = UI + Um, U3 = 0.8

Maxwell-Boltzmann velocity distribution.

Upon increasing the temperature, the average of the absolute value of molecular speed increases. The width of the distribution increases due to an increase in the interactions between the molecules. (+ graph)

Voltage divider circuit.

Used for controlling the voltage from the power supply and in the mechanism of the negative feedback Deff: Circuit of 2 resistors in series it divides the input voltage according to the ratio of the individual resistance and by which we can control the Vout according to the following formula: Uout=Uin*(R2/R1+R2)

Semiconductor detectors in dosimetry.

Uses a diode connected in reverse bias which means there will be no current flowing through the circuit. An ionizing particle will cause an electron-hole pair in the depletion region, and thus current to flow. Current is evidence of the presence of radiation.

Fluorescence microscopy

Uses a fluorescent dye that emits fluorescence when illuminated with ultraviolet radiation.

How do you reduce internal noise in scintillation counting?

Using the minimum required voltage

State equation of real gases.

Using van der Waal's equation which adds to the formula of ideal gas, some factors occurred in real life e.g.: particles have volume, there is interaction btw. the molecules, and thus there are less molecules and energy which collide on the walls of the container and form pressure. (constant a = correction for the intermolecular force, constant b = correction for the volume of particles).

What is the visual acuity of a patient with a limiting angle of vision of 2'

V isual acuity (visus) = 1(′)/alpha(2') * 100% = 50%

Notable transitions of luminescence: vibrational relaxation, intersystem crossing.

Vibrational relaxation: as kasha's rule states, an excited molecule will first reach the lowest vibrational level of s1, by vibration and rotation, losing energy in the form of heat (Ekin). Intersystem crossing: occurs in phosphorescence, a process in which electron transition occurs btw. the singlet and the triplet state (singlet and triplet state have different spin multiplicity [formula:2S+1]) *note: triplet has lower energy state than singlet

What kind of image is formed by a compound light microscope?

Virtual, magnified and inverted

Characterize the image of an object placed within the focal distance of a converging lens.

Virtual, magnified and upright

Factors influencing specific optical rotation

Wavelength, temperature and the chemical composition

The photoelectric effect.

When a photon of energy E = h * f delivers enough energy to an electron, causing it to leave the atom. Experiments by Einstein proved this because not all types of light will result in the ejection of an electron, only lights of sufficient energy (UV for example). This proved the quantized nature of light =photon and thus the particle nature of light (and got him the nobel prize)

wave diffraction

When light passes through a slit which is near the size of the wavelength, it will spread around the slit. Ties us back to the Huygens-Fresnel principle, which explains diffraction. It results in a diffraction pattern.

Fundamentals of geometric optics

When light propagates through slits which are much larger than its wavelength, we can consider the wavefront as a line. This simplification allows us to calculate optical imaging with relative ease.

Does a greater sone value always correspond to a louder sound?

Yes

Biomechanics II.: Hooke's law, Young-modulus.

Young modulus v.s. hooke's law (look at formulas) hooke's law:​spring constant depends on the dimension of the body (cross-section and length) ​and​on the material (E young modulus constant). Can be calculated by the external force acting on the body and the deformation. young's modulus-​measure the stiffness of the materials (stress/strain) and the constant depends ​only ​on the type of the material.

Types of radioactive decay.

alpha, beta+, beta-, gamma, (electron capture)

Auxiliary factors of circulation: the windkessel effect.

arterial elasticity: function as capacitor→ propel the fluid upon relaxation venous valves→ keep the bloods moving unilaterally (in 1 direction) muscle action→ assist in blood flow negative intrathoracic pressure the windkessel effect- due to the elasticity of the aorta ther is constant flow of blood (during systole the aortic axpant and form '' pouches'' that store part of the blood and in diastole they compensate on the close aortic valves by maintaining continuous flow) *help in dumping the fluctuation in blood pressure over the cardiac cycle.

X-ray image amplifier.

can be used in real time surgery bc the image is being screened to a monitor. advantage: reduces the dosage needed for an x-ray image and produce digitizable optical image without using an x-ray absorption film disadvantage: the amplified image is miniaturized with respect to the original x-ray image (spatial resolution decreases). composed of a device containing 2 luminescence screens, electrode and photo cathode. steps of the process: a. body x-ray image appear on the first luminescence screen (the attenuated radiation from the body is proportional to the number of the optical photons) b. luminescence light emitted to the photocathode produces photo-electrons which are proportional to the intensity of the radiation.Those electron being accelerated and focused by high voltage c. the electron reaches the second luminescence screen and through the electron lens thus we get a real image, reversed, miniaturized and very luminous

Box model of the human respiratory system.

closed box (chest wall) and tube inserted (trachea)intrapulmonary pressure: approx 1 atmintrapleural pressure: negative pressure (in the pleural space b/w the layers of the pleura, virtual space in healthy person)transpulmonary pressure: pressure difference b/w chest wall (atm pressure and the pleural pressure) (P= alveolar pressure- intrapleural pressure)

Conductive and gas-exchange parts of the human respiratory system.

conductive parts are the: bronchioles, bronchus, trachea, pharynx, larynx gas exchange parts are the alveoli and capillaries

Biophysics of hearing II.: the middle ear.

contain the auditory ossicles: malleus,incus, stapes and eustachian tube.role of middle ear: pressure amplification due to cross sectional area different b/w eardrum and the oval window and auditory ossicles→converting the pressure from air medium into liquid medium (without it, it would be complete reflection and no signal will occur) eustachian tube: pathway of atmospheric pressure equilibrium

Diffusion of ions across the membrane, permeability.

depends on the e​lectrochemical gradient​and the number of the channels and carriers to a specific substance (due to the fact that that the cell membrane functions as an insulator). we can use the modulated onsager equation to calculate passive diffusion, ​which includes the diffusion coefficient D.

Stern-Gerlach-experiment.

experiment which confirmed the quantization of e spin into 2 orientations (+0.5 and -0.5)a beam of ag atoms was directd into a region of non-uniform magnetic field→ they expected to detect a continuous mark on the photographic plate which mean that the e have multiple orientation of the dipole→ the result was a distinct two lines on the photographic which mean that there is just 2 possible orientation of the magnetic moment of the e-

Laminar and turbulent flow.

laminar: fluid layers do not mix, position of the flowing particles relative to each other is constant turbulent: (above critical flow velocity). fluid layers mix, slower flow (compared to laminar flow)

Concepts of magnification and angular magnification.

magnification is the ratio b/w image and object sizeangular magnification define as the ration b/w tan beta(angle of the image)e and tan alpha (the angle of the object)a.in case that the image is form on the near point [M(angle)=(nearpoin /focal length)+1] (near point=0.25meter) b. in case the image form at the infinity: M(angle)=nearpoint/focal length

Differences between NMR and ESR spectroscopies.

nuclear magnetic resonance (NMR)- used to determine: content and purity of sample as well as its molecular structure,bymeasuring the local magnetic eld around atomic nuclei. We measure the resonance frequencies of the nuclei positioned in the magnetic eld (constant magnetic field), the surrounding of the nuclei change its larmor frequency, thus it's possible to analyze the structure of the sample by measuring the various wavelength absorbed EM frequency.NMR spectrum: intensity of absorbed electromagnetic radiation as a function of frequency. ESR (electron paramagnetic resonance)-Spectroscopic method for investigating materials containing unpaired electrons.EPR spectrum: intensity of electromagnetic radiation as a function of magnetic field. (the frequency is constant) can analyzed the level of mobility and the proximity by the addition of spin labeling (-SH).

MRI contrast methods: proton density, T1 and T2 weighting.

proton density: nuclear magnetic resonance of H+ forms the major basis of MRI, the signal can be weighted to reflect the actual density of the proton ( image that distinct well b/w fluid, and hyaline cartilage and fibrocartilage) prime method in orthopedics field. T1 weighting: contrast the different b/w soft tissue (e.g. healthy and cancerous) by examining the spin-lattice relaxation time. (short RP time= better contrast) T2 weighting: contrast depends on spin-spin relaxation time. longer echo time enhance the contrast (longer TE= higher contrast)

The monostable multivibrator and its applications.

pulse generator producing a single output pulse of defined length, for every input pulse above a threshold. Application: Defibrillator.

The sliding filament model of muscle contraction.

reference to the arrangements of thick myosin and thin actin filaments in the relax and contracting state. in the presence of atp and Ca(+2) ion, the myosin pulling the actin filament toward the center of the sarcomere.

The phon scale.

represent the loudness level according to weber-fechner lawwhich describe the sensation as a log function of the relative stimuli, expressed in decibel. (not accurate as sone scale)

Stevens' Law.

sensation is a power function of the relative stimulus, where the exponent n is characteristic for the modality of sensation. Sensation = constant * (x/x0)^n

Gas exchange between blood and alveoli.

the amount of O2 and CO2 that diffuses across the membrane of an alveolus depends on: - difference in partial pressure - surface area of the membrane - inversely proportional to the thickness of the membrane by given diffusion coefficient for each of them, we can calculated the volumetric flow rate by using fick's first law

Biophysics of hearing IV.: signal transduction in hair cells.

the basal membrane distorted due to the ''surf wave'' '(depends on frequency of the sound waves) which cause the hair cells to tilted→cation gates are open (k+ & Ca+2) → depolarization occur → neurotransmitters released into afferent nerve cells→ depolarization occurs→ frequency of AP increase. *outer hair cells also amplifying narrow range of frequency of the sound by an active work (by contraction tilted the stereocilia and transduce AP) → positive feedback

Fick's I. law.

the flow of a particle per unit time across unit area is proportional to the concentration drop.

Mechanisms and energy dependence of x-ray absorption.

two types of mechanism: photo-effect and compton-scattering. The photo-effect is the dominant process and it depends on the atomic number on the thirds power. formula : rho m = C*wavelength^3*Z^3 thus, it is possible to differentiate btw. different materials in the body and produce structural image (by the different absorption level)*for soft tissue imaging (have relatively low atomic number) we use soft radiation with bigger wavelength to compensate for their low atomic number.

Fundamentals of thermodynamics I.: types of systems, the human body as a thermodynamic system.

types of system: a. open- exchange of matter and energy with the surrounding b. closed- exchange of energy only with the surroundingc. isolated- no exchange with the surrounding the human body system function as an open system:exchange matter with the surrounding (e.g. gas exchange, water) exchange energy: energy is used to create mechanical work

Viscoelasticity I.: mechanical model

viscous matter: resist shear flow and strain linearly with time when stress is applied elastic matter strain when stretched and immediately return to their original state once the stress is removed visco-elastic body→ characteristic of biopolymers:​viscous and elastic behavior appears simultaneously Model: parallel connection of spring and dashboard

Harmonic oscillation (definition, equation, graph.)

x=Asin(phi0+omega*t)

Define optical density (absorbance).

​=log(Jo/J)

Information obtained by isotope diagnostics.

● Function of an organ: metabolism (how quickly it absorbs and expels the tracker) ● Circulation in that organ (if the tracker is placed in the blood) ● Air circulation in that organ (if the tracker is inhaled)

The liquid state.

● Lacks the spatial order of a solid (short-range order). ● Isotropic; have no directional dependance (unlike crystals) ● Take the shape of the container ● Not compressible (generally)

Applications of lasers.

● Surgery (C02) ● photodynamic diagnosis and therapy, where fluorophores are inserted into the body, causing the tumor cells to florence, laser beams directed at that area will cause free radicals → killing tumor cells.