Loading…

Flash Player 9 (or above) is needed to view presentations.
We have detected that you do not have it on your computer. To install it, go here.

Like this presentation? Why not share!

1-22-08

on

  • 259 views

 

Statistics

Views

Total Views
259
Views on SlideShare
259
Embed Views
0

Actions

Likes
0
Downloads
0
Comments
0

0 Embeds 0

No embeds

Accessibility

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment
  • 24_06.jpg
  • 24_07.jpg
  • 24_p1057.jpg
  • 24_08.jpg
  • 24_09.jpg

1-22-08 1-22-08 Presentation Transcript

  • Chemistry 115 Lecture 5 Outline Chapter 24 Nuclear Transmutation Radiation, Dosages Nuclear Medicine HW3: Due Friday, Jan 25 (Quiz 2) Recitation: Ch 24: Radioactive Decay. Nuclear Stability Radiation Dosage, Nuclear Medicine Binding Energy, Nuclear Power
  • Nuclear Transmutation Nuclear transmutation – transform 1 element into another - like Alchemy Example: 14 7 N + 4 2 He  1 1 H + 17 8 O Rutherford, 1919 This led to the discovery of the neutron – like a gamma ray (neutral charge), but heavy like a proton. This approach is used to make the transuranium elements And studied in accelerators
  • Linear Accelerator
  • Fig. 24.7 Ion Cyclotron
  • Inside a large accelerator
  • Nuclear Transmutations
  • Radiation Radiation when it interacts with matter can cause two effects: Non-ionizing radation – causes atoms to vibrate matter gains heat Ionizing radiation – causes loss of electron(s): Atom  ion + + e - This type of radiation can be dangerous because it causes reactive radical species.
  • Radiation Penetrating Power
  • Units of Radioactivity Activity or disintegrations (transformations) per unit of time is expressed in units of curies (Ci) or in the SI unit of becquerels (Bq) One becquerel = 1 disintegration per second (s -1 ). One curie = 3.7 x 10 10 disintegrations per second = 3.7 x 10 10 becquerels
  • Units of Dose Not all types of radiation are absorbed to the same extent. Different types of radiation deposit different amounts of energy when absorbed by the body. A Gray is the SI unit of absorbed dose. gy = 1 joule / kg of body tissue = 100 rads
  • Radiation Equivalents Particle Relative energy deposited Relative Biological Effectiveness  1 e - 1 1 1 p 5 1 0 n 1 - 100 4 2 He 20 rem = RBE x rads
  •  
  • Radiation Damage 1 gy = 1 J/kg 4 gy/ 1 g H 2 O raises the temperature by 4 o C Radiation damage is not due to heating, it results from breaking chemical bonds in a body producing free radicals. Free radical, unpaired e -
  • Radiation Damage The body can handle and repair a certain amount of free radical damage whether it is caused by radiation, drinking alcohol, heavy labor, heavy exercise, eating slightly rancid food, or from wounds. Radiation sickness is a free radical disease just as a hang-over is.
  • Radiation Damage The body can handle a certain amount of free radicals before the free radicals overwhelm the body's free radical scavenging system. When overwhelmed, part of the free radical damage consists of damage to the body's free radical scavenging system creating a vicious cycle. Radiation kills by breaking cells DNA. As a consequence, cells can no longer reproduce. LD 50 is approximately 2.5 - 4 Gy (250 – 400 rem) depending on length of exposure and treatment.
  • Nuclear Medicine
    • Nuclear medicine:
    • uses radioactive substances (radiopharmaceuticals)
    • radioactive substances are administered and the radiation emitted is measured
    • usually involves the formation of an image
    • radionuclides are also administered to treat disease or provide pain relief.
      • iodine-131 is often used for the treatment of thyrotoxicosis and thyroid cancer.
  • 99 Mo  99m Tc + e - 99 Mo: t 1/2 = 66 h 99m Tc  99 Tc +  99m Tc: t 1/2 = 6 h γ -rays behave like x-rays, they pass through tissue. Cardiolite distributes in the heart proportionally to the blood flow in the heart’s muscle
  • Thyroid Images 131 I 99 Tc
  • Nuclear Reactions Positron Emission,  + -decay Positron Emission: decay by loss of an a positron, a particle with the same mass as an electron but with a positive charge (a positive electron). 11 6 C  11 5 B + 0 1 e The positron interacts with an electron, and the two annihilate each other.  All of their mass is converted into energy––two 0.511 MeV gamma rays are produced. 0 –1 e    +   0 +1 e     2  (0.511 MeV each)
  • PET Positron Emission Tomography  + +  -  2  (0.511 MeV each, in opposite directions)
  • Nuclear Chemistry: PET Imaging
  • PET 18 O + 1 p  18 F + 1 n 18 F  18 O + e + Brain with blunt force trauma
  • DNA mapping 32 15 P: Image DNA fragments Photographic image formed from decay of 32 P