Medical Laboratory Basic Physics Summer Course

Medical Laboratory Program 1st Level Summer Course - Basic Physics

• Course Instructor: Prof. Dr. Soltan Soltan
• Department: Physics Department, Faculty of Science, Helwan University
• Topic: Basic Physics for Medical Laboratory Devices

Introduction

• Medical Laboratory Devices and Physics Importance: Physics is crucial to understanding device applications in medical labs.
• Basic Physics: Covers various physics principles relevant to medical lab devices.

Topics Covered

• Heat: Effects of temperature on structure/phase state.
• Electricity: Electron motion, conductivity, resistivity, energy gap.
• Magnetism: Spin, moment, Electron spin resonance (ESR).
• Optics: Reflectivity, transmission, emission, lenses.
• Applications and Devices: X-ray, magnetic imaging, radiation.

Medical Laboratory Devices and Output Images

• XRD: X-Ray Diffraction
• NMR: Nuclear Magnetic Resonance
• MRI: Magnetic Resonance Imaging

Dimensionless Numbers (Table 1)

• Various units for parts per hundred (%), million (ppm), billion (ppb), trillion (ppt), quadrillion (ppq), etc. are listed with examples and potential replacements.

Course Content

• Chapter I: Heat Phenomena and Thermal Physics
• Chapter II: Heat and Matter
• Chapter III: Calorimetry
• Chapter IV: Thermometry
• Chapter V: Heat Transfer
• Chapter VI: Thermal Analysis

Heat and Matter

• Heat energy effects on a body lead to reversible effects like changes in temperature, state (solid to liquid, liquid to vapour), phase, size/structure, physical properties (electric, magnetic) and color.

Heating and Cooling Curves

• Heat energy changes state.
• Heat energy increases temperature.
• Reverse changes happen on cooling.
• Heating/cooling curves show these changes.

Phase Diagrams

• Most materials undergo phase transformations.
• Phase diagrams show equilibrium phases for given chemical compositions.
• Types of phase diagrams include unary, binary, ternary, constitutional diagrams.

One Component Systems

• Three areas represent solid, liquid, gas states where only one phase exists.
• Three lines show transition between one phase to another or existence of two phases if isolated.
• Melting point, sublimation point, boiling point/condensation point are equilibrium conditions.
• Triple point shows where solid, liquid, and gas coexist.

Pressure-Temperature Equilibrium Phase Diagrams

• Equilibrium phase diagrams are divided into two classes of substances.
• First class substances expand upon solidification (e.g.; water, bismuth).
• Second class substances contract upon solidification (e.g.; carbon dioxide, oxygen).

Phase Equilibria and Phase Rule

• Phase (P): a homogenous physically distinct portion of a system.
• Number of Components (C): the smallest number of constituents for expressing composition in chemical formula form.
• Degrees of freedom (F): number of variables that can be varied.

Effect of Pressure on Phase Transformations

• Vapor pressure relates to the pressure of its vapour in equilibrium with liquid or solid.
• Vapor pressure graphs are curves of vapor pressure versus temperature.
• Vapor pressure is only a function of temperature not volume,and not dependent on the relative amount of vapor, solid, or liquid. -Boiling point: Temperature at which vapor pressure equals external pressure. -Sublimation temperature: Temperature at which vapor pressure equals external pressure.
  • Melting point: Temperature at which vapor pressure equals external pressure.

Change in Size/Fundamentals

• Some volume change is associated with phase transformations.
• Change in size during heating/cooling can be considered in temperature ranges where no phase change is occurring.
• Thermal energy is often in the form of atomic vibrations of varying amplitude.

Vibrational Modes

• Atoms vibrate longitudinally or transversely.
• Longitudinal vibrations: atoms vibrate along the bond direction.
• Transverse vibrations: atoms vibrate perpendicular to the bond direction.

Rigid Unit Modes

• Stiff tetrahedra or octahedra (strong M-O bonds, short O-O distances) exhibit certain bending potentials.

Animations showing the potential structural flexibility of ZrW2O8

• Visual representations of structural change in ZrW2O8.

Change in Volume of Water

• Exceptions to general rule in water volume changes:
• Water contracts when melting from solid to liquid, and decreases in volume from 0 to 4°C, then after 4°C it expands.
• Water has minimum volume and maximum density at 4°C.

Consequences of Anomalous Behaviour of Water

• Ice expands upon freezing → ice floats.
• Water at surface becomes cooler, denser, and sinks to bottom.

Structure of H₂O

• Hydrogen bonds cause unusual properties in water, including large heat of vaporization and expansion upon freezing.
• Ice has an open solid structure and therefore is less dense than liquid water.

Dry Ice

• Solid carbon dioxide.
• Sublimes at -78°C (solid directly changes to gas).
• Rapid expansion of CO2 gas.

Applications of Thermal Expansion

• The Rivet: Heating hammered rivet contracts tightly fixing plates.
• Positive Thermal Expansion: Explained through Thermostat example (bimetallic strip)

Negative Thermal Expansion

• In some materials, thermal expansion can be negative, in other words, the material contracts when heated.
• Thermal expansion issues in engineering applications, leading to zero expansion composite materials.

Thermal Stresses

• Mechanical stress due to constraint during thermal expansion/contraction.
• Not free expansion causing thermal stress in structures because of geometry or external constraints.
• Temperature gradients also contribute.

Smart Materials:

• Smart Resistors (PTC): Unusual resistivity behavior with temperature for self-protection circuits.
• Thermochromic Materials: Change color reversibly with temperature. Explained through example of paint/printing/inks, thermochromic pigments for temperature-changes.