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An Introduction to Biophysics

An Introduction to Biophysics. Prof. Dr. Moustafa . M. Mohamed Vice Dean Faculty of Allied Medical Science Pharos University Alexandria Dr . Yasser khedr Basic Science Department Faculty of Physical therapy Pharos University in Alexandria. Topics. ch4. ch3. ch2. ch1.

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An Introduction to Biophysics

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  1. An Introduction to Biophysics • Prof. Dr. Moustafa. M. Mohamed • Vice Dean • Faculty of Allied Medical Science • Pharos University • Alexandria • Dr. Yasser khedr • Basic Science Department • Faculty of Physical therapy • Pharos University in Alexandria

  2. Topics ch4 ch3 ch2 ch1 Ultrasound In Medicine And Biology Electricity Within The Body Cardio Vascular Instrumentation Heat In Medicine

  3. Topics ch6 ch5 ch5 Laser In Medicine And Biology Human vision Nuclear Medicine

  4. Calendar

  5. Calendar

  6. What Is Biophysics?

  7. Biophysics • Link Between

  8. Biophysics • Biophysics is a bridge between biology and physics. • biophysics is the study of biological systems and biological processes using physics-based methods or based on physical principles.

  9. How Essential Is Biophysics To Progress In Biology? • Biophysics discovers how atoms are arranged to work in DNA and proteins. • Biophysicists are discovering how proteins work, they use these protein structures for discovering how biological machines work, in health and also in diseases.

  10. How Essential Is Biophysics To Progress In Biology? 3. Variations in proteins make people respond to drugs differently. Understanding these differences opens new possibilities in drug design, diagnosis, , disease control and decrease of side effects.

  11. What Are The Applications Of Biophysics? 1. The applications of biophysics depend on society’s needs. 2. In the 20th century, great progress was made in treating disease. Biophysics helped create powerful vaccines against infectious diseases. 3. It described and controlled diseases of metabolism, such as diabetes. 4. Biophysics provided both the tools and the understanding for treating the diseases of growth known as cancers.

  12. What Are The Applications Of Biophysics? 5. Biophysical methods are increasingly used to serve everyday needs, from forensic science to bioremediation 6. Biophysics gives us medical imaging technologies including MRI, CAT scans and sonograms for diagnosing diseases. 7. It provides the life-saving treatment methods of kidney dialysis, radiation therapy, cardiac defibrillators, and pacemakers.

  13. Why Is Biophysics Important Right Now? 1. Biophysics discovers how to modify microorganisms for biofuel (replacing gasoline and diesel fuel) and bioelectricity (replacing petroleum products and coal for producing electricity). 2. Biophysics discovers the biological cycles of heat, light, water, carbon, nitrogen, oxygen, heat, and organisms throughout our planet. 3. Biophysics harnesses microorganisms to clean our water and to produce lifesaving drugs.

  14. Instrumentation AND Biophysical Methods . Measuring systems are used to provide quantitative information about parameters of biological importance. Such parameters may include bio potentials from muscles, neurons, eye, heart or brain, blood pressure or muscle forces . The signal may take different forms, such as being mechanical or electrical. . Electrical signals are the most popular and they have to be well treated so as to eliminate unwanted signals and amplified to be displayed

  15. Examples of Electric Signals • Electrical potentials of nerves. • Electrical signals from muscles the electro- myogram. • Electrical signal from the heart the electro- cardiogram. • Electrical signal from the brain the electro-encephalogram. • Electrical signal from the eye the electro-retinogram and the electro oculogram.

  16. Cardiovascular Instrumentation • Bio potentials of the heart. • Electrodes. • Amplifiers. • Patient monitoring. • Defibrillators. • Pacemakers.

  17. Applications Of Electricity And Magnetism In Medicine • Electrical shock . • High frequency electricity in medicine. • Low frequency electricity and magnetism in medicine. • Current research involving electricity applied in the body.

  18. Sound In Medicine • General properties of the sound. • The body as a drum (percussion in medicine). • Ultrasound pictures of the body. • Ultrasound measure motion. • Physiological effects of ultrasound in therapy. • The production of speech (phonation).

  19. Physics Of Ear And Hearing • The outer ear. • The middle ear. • The inner ear. • Sensitivity of the ears. • Testing your hearing. • Deafness and hearing aids.

  20. Light In Medicine • Measurement of light and its units. • Applications of visible light in medicine. • Applications of ultraviolet and infrared light in medicine. • Laser in medicine. • Application of microscopes in medicine.

  21. Physics Of Eyes And Vision • Focusing elements of eye. • Diffraction effects on the eye. • Defective vision and its correction. • Color vision and chromatic aberration. • Instruments used in ophthalmology.

  22. Physics Of Diagnostic X-ray • Production of X-ray beam. • How X-ray are absorbed. • Making an X-ray image. • Radiation to patient from X-rays. • X-ray slices of the body.

  23. Physics Of Radiation Therapy: • The dose units used in radiotherapy are the rad and gray. • Principles of radiation therapy. • A short course in radiotherapy treatment planning. • Megavoltage therapy.

  24. Heat And Cold In Medicine • Physical basis of heat and temperature. • Thermometry and temperature scales. • Thermography mapping the body’s temperature. • Heat therapy. • Use of cold in medicine. • Cryosurgery.

  25. Tutorial Biophysicsintroduction of electricity Dr : Yasser Ibrahim Khedr Lecturer Assistant : Bohaysa Salem Basic Science Department Faculty of Physical therapy Pharos University in Alexandria

  26. Basic Electric Circuit Concepts What is electricity? Electricity is the set of physical phenomena associated with the presence and flow of electric charge. cell switch wires lamp

  27. Electric charge There are two types of electric charges – positive and negative. Ion is an atom that has lost one or more electrons, giving it a net positive charge (Cation) Example : Sodium, Calcium, Potassium, and Magnesium or that has gained one or more electrons, giving it a net negative charge (Anion). Example : Chloride, Sulfate, Phosphate, Bicarbonate

  28. Basic Electric Circuit Concepts Current Movement or flow of electrically charged particles, typically measured in amperes. The unit of current is the ampere (A). 1 ampere = 1 coulomb/second 3

  29. Basic Electric Circuit Concepts Voltage a force that pushes the current through the circuit. Suppose one coulomb of charge is located at point b and one joule of energy is required to move the charge to point a. Then we say that Vab = 1 volt = 1 joule/coulomb = 1 Newton.meter/coulomb. 5

  30. Basic Electric Circuit Concepts Resistance: Friction that impedes flow of current through the circuit (rocks in the river) Ohm’s Law I = Current (Amperes) (amps) V = Voltage (Volts) R = Resistance (ohms)

  31. Another way to find resistance • The resistance varies directly with length and inversely with width (or cross-sectional area) • Short, thick wire  small resistance • Long, skinny wire  large resistance • = Resistivity • σ= Conductivity

  32. Measuring Resistance • We can find the resistance of a component by measuring • voltage across the component using a voltmeter • current through the component using an ammeter

  33. Measuring Resistance • or we can measure it directly using an ohmmeter Ω

  34. Calculate the resistance of auniform wire of a diameter 0.32mm and length 5.0m , the resistivity of awire 5x10-7 Ωm Example 1: Solution A=Pi r2 r=0.00016 R=5.0 x10-7 x 5/(Pi x 0.000162) R=31Ω

  35. Solutionr = 0.14mm = 0.00014mL = 1.50 m, R = 45, A = 6.15x10-8ρ = 45x(6.15x10-8 /a.5)=0.0000018=1.8x10-6 Ω .mL=1x(6.15x10-8 /1.8x10-6 )=0.034 m Example 2: A wire of uniform diameter 0.28 mm and length a.50m has a resistance of 45 Calculate 1- its resistivity 2- the length of wire that has a resistance of 1.0

  36. Simple Circuits • Series circuit • All in a row • 1 path for electricity • 1 light goes out and the circuit is broken • Parallel circuit • Many paths for electricity • 1 light goes out and the others stay on

  37. Series and Parallel Circuits What type of circuit is this? What is the relationship between the three currents? The current is the same at each point.

  38. What is the relationship between the four voltages? They add to equal the supply voltage. How do you find total resistance in series? Add each resistance together.

  39. What type of circuit is this? What is the relationship between the four currents? The four currents add to give the total current. What is the relationship between the four voltages? Each voltage is equal to the supply voltage.

  40. The resistance in parallel?

  41. Find the total resistance of R1=2Ω, R2=5Ω and R3=7Ω if connected in series then in parallel • Solution • In series =2+5+7 =14 Ω In parallel =1/2 +1/5 +1/7 =1.2 Ω

  42. Capacitors • A basic capacitor has two parallel plates separated by an insulating material • A capacitor stores an electrical charge between the two plates • The unit of capacitance is Farads (F) • Capacitance values are normally smaller, such as µF, nF or pF

  43. Capacitors • Basic capacitor construction Dielectric material Plate 2 Plate 1 The dielectric material is an insulator therefore no current flows through the capacitor

  44. Capacitors Storing a charge between the plates • Electrons on the left plate are attracted toward the positive terminal of the voltage source • This leaves an excess of positively charged holes • The electrons are pushed toward the right plate • Excess electrons leave a negative charge

  45. Q = C Vwhere C = ɛoA / dfor a parallel plate capacitor, where ɛois the permittivity of the insulating material (dielectric) between plates. The unit of capacitance is called the Farad (F). A charged parallelplate capacitor.

  46. 1 1 1 / CT= 1 / C1 + 1 / C2 Two capacitors in series and the equivalent capacitor.V = V1 + V2 and Q = C V

  47. CT= C1 + C2 Two capacitors in parallel and the equivalent capacitor.Q = Q1 + Q2 and Q = C V

  48. Solution C1=5 µF =5x10-6 F C2= 12.0 µF =12x10-6 F In parallel Ceq=C1+C2 = 5x10-6 + 12x10-6 =17x10-6 F Two capacitors, C1= 5.00 µF and C2= 12.0 µF, are connected in parallel What is the equivalentcapacitance of the combination?

  49. Reference • Text books • First – Title: Physics in Biology and Medicine, – Author: Paul Davidovits • Second – Title: Medical Physics – Author: Martin Hollins • Third – Title: Medical Physics – Author: John R. Cameron and James G. Shofronck • Fourth – Title: General Physics – Morton M. Sternheim and Joseph W. Kane

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