Basis of Biophysics1
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This document discusses x-rays and their production and properties. It describes how x-rays are generated using a Coolidge tube by accelerating electrons into a metal target. This produces both a spectrum of x-ray wavelengths via bremsstrahlung and characteristic x-ray lines. Units used to measure x-ray properties like intensity and absorption are defined. The document also discusses how x-ray absorption depends on the electron density and thickness of absorbers, allowing their use in medical diagnosis.
![M.V.L. and it is a measure of the degree of penetration of the X-rays or gamma rays
(a) Calibration of the X-ray beam energy emitted from the X-ray tube.
(b) Design of a filter from certain elements of known(u) to reduce the dose intensity and
energy of the X-rays.
(c) Design of protection walls and screens for the personnel operating the X-ray machine.
[less absorbed x-rays]
Absorption of X-rays by atoms of different absorbers. (basis of diagnosis).](https://image.slidesharecdn.com/basisofbiophysics1-200316114502/85/Basis-of-Biophysics1-41-320.jpg)
Basis of Biophysics1
- 1. By Dr GALAL ZEDAN FARAG TANTA UNIVERSITY FACULTY OF SCIENCE PHYSICS DEPARTEMENT
- 6. Fig(1) . First, second and third class levers.
- 9. Fig (3 ), (a) cell in hypertonic solution (b) cell in hypotonic solution.
- 13. Figure 7: A graphical representation of the concentrations of particles as a func¬tion of x for different times when the initial concentration (at t=0) is that all the particles are at the origin,
- 14. Figure. (8) : Schematic representation of one model of a pore in a plasma membrane. The membrane is depicted here in cross section.
- 15. Fig. (1) Plasma membrane Figure (2): Nerve cell Figure 9: A. schema tie representing of an axon in the resting state. The dipole sheath across the plasma membrane, positive outside and negative inside, produces a difference in potential of about 90 mV across the plasma membrane.
- 17. Fig.(4): Action potential propagation in a mylinated nerve.
- 18. Fig. (5): Action potential of a nerve.
- 20. External and middle ear, opened from the front; right side.
- 21. View of the inner wall of the tympanum (enlarged) The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above
- 29. Light and Vision
- 32. The accommodation process Because lens is a liquid crystal much like jelly: , its shape can be changed by the tension excreted by the ciliary muscles. This tension is in turn controlled by a nervous signal fed back from the retina, the cells of which estimate the sharpness of the image. PHOTOSENSITIVE CELLS: rod cone scotopic vision more sensitive to light, and distinguish for us light from dark view the intensity is very low (twilight vision) less sensitive can resolve large amounts of light into its components, and therefore detect details of the image, such as shape and color photonic vision 126,000 cells/mm2 the fovea red (6200 to 7800°A), green (5000 to 5800°A) blue (4200 to 5000°A); mix color
- 33. Figure 27 The scheme above indicates that: • the greater the intensity of the incoming light, the more will the rhodopsin be reached. • In twilight most of the pigment exists as rhodopsin, and the sensitivity is greatest. • In daylight, most of it will be bleached, and the sensitivity least. • "Dark-adaptation" is very familiar to us all; it is slow because the speed of regeneration of rhodopsin is slow.
- 34. CHAPTER VII X-RAYS (i)- Types of waves: A wave is the form by which energy is transferee from one point to the other. There are only 2 types of waves which are : A- Mechanical waves
- 35. B-Electromagnetic waves (e.m.w): (ii)- The electromagnetic spectrum : One Angstrom = 1A=10-10 mm=10-8m = 10-4u(micron)=10 nm (nanometer). (iii) Unite a-The Rontgen: is the amount of X- rays or gamma radiations which produces ions carrying a charge equals 3×10-10 coulombs in 1 cm3 of air. This unit is used as a measure of exposure to the radiation in air.
- 36. b-The Rad (Radiation absorbed dose): is the amount of absorbed energy which equals 100 ergs (10 joules) per gram of any absorbing material. The rad equals 103 milli-rad. Recently, a new unit called the Gray is used, where 1 Gy = l joules/k gm. (1 rad = 0.01 Gy = 0.01 J/k gm.). C-The Curie: is the amount of radioactive material (isotope) which gives 3.7×l010 disintegration/sec. Recently, a new unit called the Bequrel is used where 1 ci = 37 G Bq. (G = 109 ) e- Intensity: It equals the energy E per unit area of An absorber per second , I = 𝑬 𝑨 𝒏.𝒕 where t is the time in seconds, and An is the unit area for n material. d- The electron volt (eV): is the unit of energy. It equals to the amount of energy which; is gained by an electron moving between two points having potential difference of 1 volt. The energy of the electron= the charge of the electron (1.6×10-19 coulomb) × the potential difference (1 volt) = 1.6×10-19 coulomb × volt = 1.6×10-19 joule 1 eV = 1.6×10-19 joule.
- 37. 2- X-Ray Production Tube (Coolidge X-ray tube) X-rays were discovered by William Rontgen in 1895 a) Calculation of the energy of X-ray line spectrum (𝐾 𝛼, 𝐾 𝐵. .): 𝐵𝐸 𝑛 = − 𝑚𝑒4 𝑧2 8𝑒 𝑜 2ℎ2 . 1 𝑛2 (1) = constant 1 𝑛2 (2) K X-rays are emitted when the electron from L shell (n=2) fills the vacancy in the K shell (n=l). The energy of these X-rays (EK ) = the difference between the electron energy in the L shell (En=2) and that of the K shell (En=1). Equation 2 gives E2= -constant 𝟏 𝟐 𝟐 =constant( 𝟏 𝟒 ) . E2-E1= - constant ( 𝟏 𝟒 − 𝟏 𝟏 ) = -constant (− 𝟑 𝟒 ) = -constant × 𝟑 𝟒
- 38. Another possibility for these accelerated electrons is that they do not meet and collide with any electron in the target atom, but moves near the positive nucleus at distances (X1, X2, X3, X4, …Xn). I X3 X2 X1 E X-ray continuous spectra (Bremsstrahlung(
- 39. Bremsstrahlung I E Actual X-ray spectrum (Line & Continuous spectra) K K 4- USE Of X-RAYS IN DIAGNOSIS depends on 1-The electron density of the metal i.e. its absorption coefficient (u) 2-The thickness of the absorbing metal (d) 3-The intensity of the X-ray incident on the material (Io) half value layer (h.v.l) 𝒂𝒃𝒔𝒐𝒓𝒃𝒆𝒓 (𝒅 𝟏 𝟐 ) (𝐼𝑜/2).
- 41. M.V.L. and it is a measure of the degree of penetration of the X-rays or gamma rays (a) Calibration of the X-ray beam energy emitted from the X-ray tube. (b) Design of a filter from certain elements of known(u) to reduce the dose intensity and energy of the X-rays. (c) Design of protection walls and screens for the personnel operating the X-ray machine. [less absorbed x-rays] Absorption of X-rays by atoms of different absorbers. (basis of diagnosis).
- 42. االستماع لحسن شكرا..... والتوفيــــــــــق ولى هللا