Ionizing Radiation and Life

• ANGLE OF DIFFRACTION 

  • Angle at which a wave is bent or spread out when it encounters an obstacle or aperture
• RAYLEIGH LIMIT

  • Minimum distance at which two closely spaced objects can be distinguished in an optical system
  • Helps determine the optimal conditions for imaging and analyzing biological samples under ionizing radiation
• • Geiger-Muller counter
  • A passing ionizing particle causes an avalanche of electrons due to a strong inward radial electric field on the interior gas
• • Photomultiplier tubes
  • Utilizes an electron focusing grid which allows for photons to be amplified by a dynode until a current flows through the system due to the acceleration
• • Scintillation detectors
  • Can distinguish between different types of radiation based on the characteristics of the emitted light
• • Dosimeters
  • Devices worn by individuals to monitor and measure their exposure to ionizing radiation over time
• RADIOACTIVITY

  • Defined as the number of radioactive disintegrations per minute
  • One curie (1 Ci) = activity of 1 g of radium, or 3.7 x 10^10 dps
  • A becquerel = 1 dps
• 1. Beta rays

  • Penetrate deeper into materials than alpha
  • Can be stopped by aluminum foil or plastic
• 1. Alpha rays

  • Least penetrating type of radiation, easily stopped by a piece of paper or human skin
• 1. Gamma rays

  • EM emitted from nucleus of atom during radioactive decay
  • Highly penetrating and require dense materials like lead
• 1. X-rays

  • Similar to gamma but typically produced outside the nucleus
• 1. Neutron rays

  • Highly penetrating and can induce nuclear reactions in materials
  • Can be stopped by concrete or water
• HOW UV LIGHT IS PRODUCED

  • From atomic transitions in atoms such as mercury (Hg)
  • By heating gases to temperatures of above 4000°C
  • UV can also be produced by black light sources by producing UV in the UVA range
• • UV light induces thymine dimers
  • Covalent bonds between adjacent thymine bases in DNA, disrupting DNA replication and repair mechanisms
• UVC as Germicidal UV

  • Sterilization purposes, particularly in healthcare settings and water treatment facilities
  • Killing viruses, bacteria, and other microorganisms by damaging their DNA and preventing replication
• 240-280 nm Disinfection
• X-RAYS

  • Discovered by Wilhelm Roentgen in 1895 when he developed a photographic light that had never been exposed to light but exposed near a high voltage vacuum tube
  • Used in medicine and other applications
  • Produced by electron transition elements
  • Can be produced via Bremsstrahlung
• •  Bremsstrahlung
  • High kinetic energy of electrons from the cathode to the anode during the collisions with tungsten make some electrons bent around the tungsten nucleus by Coulomb attraction.
  • The high acceleration of electrons produces radiation, called ‘Bremsstrahlung’ or ‘breaking radiation’
• Synchrotrons

  • Particle accelerators that produce highly intense beams of EM radiation
  • Highly collimated, coherent, and tunable radiation, making it ideal for various scientific experiments and applications
• GAMMA RAYS

  • Made naturally by radioactive materials and by cosmic rays hitting the atoms in the upper atmosphere.
  • Made by humans in particle accelerators by:
  • synchrotron radiation
  • scattering of high energy nuclear particles
  • nuclear reactors
  • particle-antiparticle annihilation
• Pet Scans

  • Positron Emission Tomography (PET) scans are used to discover information on the body functions, such as specific metabolic processes.
  • PET scans work due to the generation of positrons (anti-electrons) from nuclear decay in isotopes. 
  • These positrons are annihilated by local electrons, which produces 2 gamma ways with an energy of 0.511 MeV in directions opposite to each other
• • Target Theory
  • Certain molecules are essential to cells survival, while others are not
  • Radiation “hits” to an essential molecule may result in cell death
  • DNA as target molecule
• > Direct Effect

  • Ionizing directly causes chemical alteration to the molecule
•  Chromosomal Damage

  • Main Chain Scissions
  • Break in rail of DNA ladder
  • Single-strand or double-strand break
• RADIATION THERAPY

  • The use of radiation to kill cancer cells through the use of a linear accelerator
  • Uses x-rays or proton radiation
• Brachytherapy

  • Radiation therapy inside the body
• ANGLE OF DIFFRACTION

  • Determines the direction and intensity of scattered radiation, influencing its potential impact on biological systems
•  Chromosomal Damage

  • Rung Damage
  • Loss of base molecule
• > Indirect Effect

  • Radiolysis of a water molecule causing damage to other molecules
• 250-300 nm Forensic analysis, drug detection
• 270-300 nm Protein analysis, DNA sequencing
• 280-400 nm Cell imaging (Rayleigh limit UV < visible)
• 300 -365 nm Polymer curing (in dentistry)
• 300-320 nm Light therapy in medicine
• 350 - 370 nm Bug zappers (flies are attracted to light about 365 nm)
• • 340-660 nm Fish eye vision
• • 360-700 nm Reptile eye vision
• • 300-650 nm Insect eye vision
• • 300-700 nm Bird eye vision
• • 400-700 nm Human eye vision