Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy.

Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our Privacy Policy and User Agreement for details.

Successfully reported this slideshow.

Like this presentation? Why not share!

- Summary of "A History of the Englis... by Sarah Abdussalam 36430 views
- Download infants and_Download Infan... by sherissemon 75 views
- The origins of the english language by MaFranciscaaa 3461 views
- 5 factors affecting language learni... by Salma Razak 2532 views
- A Cultural History of the English L... by Fortunata Ricci 169 views
- Factors influencing english as-a-se... by Rosa Lee 6377 views

1,545 views

Published on

No Downloads

Total views

1,545

On SlideShare

0

From Embeds

0

Number of Embeds

6

Shares

0

Downloads

60

Comments

0

Likes

3

No embeds

No notes for slide

- 1. Smart Women in Physics Together: Undergraduate Mentoring <ul><ul><li>Ask female graduate students all of your questions about </li></ul></ul><ul><ul><li>majoring in physics </li></ul></ul><ul><ul><li>applying for graduate school </li></ul></ul><ul><ul><li>being a woman in physics! </li></ul></ul><ul><ul><li>Friday, April 10 th at 2:30pm </li></ul></ul><ul><ul><li>Winnings Coffee </li></ul></ul><ul><ul><li>West side of Harvard, South of Central </li></ul></ul><ul><ul><li>Funded by the GPSA Project Committee </li></ul></ul>
- 2. Today: Radiation Dose Definitions, Medical Applications, PET scan 3-D rendering Source: wikipedia
- 3. Small group exercise! <ul><li>I place on the table a small piece of material and say, “this is radioactive.” </li></ul><ul><li>How many different properties of the material can you think of that you would want to characterize, in order to know everything about its radioactivity? </li></ul><ul><li>Form small groups, and brainstorm. Have a leader / spokesperson write down results. </li></ul>?
- 4. <ul><li>What kind of radiation is emitted? Alpha, beta, gamma. </li></ul><ul><li>Mass/weight </li></ul><ul><li>“ half-life” (time for ½ to decay) </li></ul><ul><li>Color…? </li></ul><ul><li>Temperature… </li></ul><ul><li>What is the element? </li></ul>
- 5. Measuring the amount of radioactivity or dose <ul><li>We can think about amount of radiation in two ways. </li></ul><ul><li>Describe the source of radiation </li></ul><ul><ul><li>Physics-based, rigorous </li></ul></ul><ul><li>Describe the absorbed radiation dose </li></ul><ul><ul><li>Complicated biology and other factors </li></ul></ul>
- 6. There are rigorous ways to characterize the source of radiation <ul><li>What type of radiation does the material emit? </li></ul><ul><ul><li>X-rays, gamma rays, beta radiation, alpha particles </li></ul></ul><ul><li>How much radiation per second? </li></ul><ul><ul><li>curies, becquerels, counts per second </li></ul></ul><ul><li>What is the half-life of the material? </li></ul><ul><ul><li>Minutes, days, years, … </li></ul></ul><ul><li>What is the average energy per particle or ray emitted? </li></ul>
- 7. There are rigorous ways to characterize the source of radiation <ul><li>What type of radiation does the material emit? </li></ul><ul><ul><li>X-rays, gamma rays, beta radiation, alpha particles </li></ul></ul><ul><li>How much radiation per second? </li></ul><ul><ul><li>curies, becquerels, counts per second </li></ul></ul><ul><li>What is the half-life of the material? </li></ul><ul><ul><li>Minutes, days, years, … </li></ul></ul><ul><li>What is the average energy per particle or ray emitted? </li></ul>
- 8. There are two main units of radioactivity <ul><li>The becquerel (Bq) is defined as one radioactive decay event per second </li></ul><ul><ul><li>1 Bq = 1 reaction / second </li></ul></ul><ul><li>The curie (Ci) is based on the radioactivity of about 1 gram of radium-226 </li></ul><ul><ul><li>1 Ci = 37 billion Bq = 37 billion reactions / second </li></ul></ul>Marie Curie Nobel prizes in Physics and Chemistry Henri Becquerel Nobel Prize in Physics Example: 1 kilogram of “typical” soil has 400 Bq of Potassium-40 -- or 11 nanocuries
- 9. There are rigorous ways to characterize the source of radiation <ul><li>What type of radiation does the material emit? </li></ul><ul><ul><li>X-rays, gamma rays, beta radiation, alpha particles </li></ul></ul><ul><li>How much radiation per second? </li></ul><ul><ul><li>curies, becquerels, counts per second </li></ul></ul><ul><li>What is the half-life of the material? </li></ul><ul><ul><li>Minutes, days, years, … </li></ul></ul><ul><li>What is the average energy per particle or ray emitted? </li></ul>
- 10. Radioactive decay is a random process P P P P P P P P P P P P P P P P P P U P P U P P P P U P U U P P P P P P S S S S S U P U U P P P P P U U P U P P U P S S S S S S S U P U U P P P U P U U P U U P U P S S S S S S S S S 10 days 20 days 30 days Example: Phosphorus-32 decay into Sulfur-32
- 11. Half-life is the average amount of time for ½ of the atoms to decay <ul><li>P-32 half life ~14 days </li></ul><ul><li>Decay rate is proportional to the number of radioactive atoms remaining </li></ul><ul><li>So, radioactivity of a sample decreases with the same half-life </li></ul><ul><li>Applets: http://www.colorado.edu/physics/2000/isotopes/radioactive_decay3.html </li></ul><ul><li>http://lectureonline.cl.msu.edu/~mmp/applist/decay/decay.htm </li></ul>
- 12. Radioactivity (becquerels) and Half-life are inversely related <ul><li>Longer half-life = lower radioactivity </li></ul><ul><ul><li>Stable isotope has an infinite half-life </li></ul></ul><ul><li>Shorter half-life = higher radioactivity </li></ul><ul><ul><li>Highly radioactive isotopes will disappear quickly </li></ul></ul>
- 13. Clicker Question—Half life / radioactivity <ul><li>Let’s say you have two samples, each with the same number of atoms in them. </li></ul><ul><li>Sample “A” has half-life of two weeks. </li></ul><ul><li>Sample “B” has half-life of 4 billion years. </li></ul><ul><li>Which will have a higher radioactivity? </li></ul><ul><li>A or B </li></ul>
- 14. Clicker Question—Half life / radioactivity <ul><li>Let’s say you have two samples, each with the same number of atoms in them. </li></ul><ul><li>Sample “A” has half-life of two weeks. </li></ul><ul><li>Sample “B” has half-life of 4 billion years. </li></ul><ul><li>Which will have a higher radioactivity? </li></ul><ul><li>A or B </li></ul>Shorter half-life = higher radioactivity If the half-life is infinite, it is not radioactive
- 15. There are rigorous ways to characterize the source of radiation <ul><li>What type of radiation does the material emit? </li></ul><ul><ul><li>X-rays, gamma rays, beta radiation, alpha particles </li></ul></ul><ul><li>How much radiation per second? </li></ul><ul><ul><li>curies, becquerels, counts per second </li></ul></ul><ul><li>What is the half-life of the material? </li></ul><ul><ul><li>Minutes, days, years, … </li></ul></ul><ul><li>What is the average energy per particle or ray emitted? </li></ul>
- 16. The energy per emitted particle indicates how deeply it can penetrate materials and how much damage it can do <ul><li>Examples: </li></ul><ul><ul><li>P-32 beta 1.7 megaelectronvolts (MeV) </li></ul></ul><ul><ul><li>Ra-226 alpha 4.9 MeV </li></ul></ul><ul><ul><li>Rn-222 alpha 5.6 MeV </li></ul></ul><ul><ul><li>K-40 beta 1.3 MeV </li></ul></ul><ul><li>However, the type of radiation (alpha, beta, gamma, neutron) tends to be more important </li></ul>Mega = 10^6 or 1 million
- 17. Clicker question—classifying radiation <ul><li>If held 1 inch away from your body, which radiation source is more likely to cause cancer? </li></ul><ul><li>Source with radioactivity of 1 million becquerels (Bq) </li></ul><ul><li>Source with radioactivity of 1 billion becquerels (Bq) </li></ul><ul><li>Impossible to determine </li></ul>
- 18. Clicker question—classifying radiation <ul><li>If held 1 inch away from your body, which radiation source is more likely to cause cancer? </li></ul><ul><li>Source with radioactivity of 1 million becquerels (Bq) </li></ul><ul><li>Source with radioactivity of 1 billion becquerels (Bq) </li></ul><ul><li>Impossible to determine </li></ul>There are many other things you would need to know: What type of radiation do each emit? Is there any shielding in between?
- 19. Results of homework assignment
- 20. A few homework responses Adrian: If I became a luddite and lived in a hut in the woods at sea level I might save myself 80 mrem or so. Laura: Only 2.010 mrem or 0.6 % of my annual radiation exposure can be attributed to man made sources David: Unavoidable background radiation is from food and water, there is absolutely nothing I can do to change that.
- 21. Measuring the amount of radioactivity or dose <ul><li>We can think about amount of radiation in two ways. </li></ul><ul><li>Describe the source of radiation </li></ul><ul><ul><li>Physics-based, rigorous </li></ul></ul><ul><li>Describe the absorbed radiation dose </li></ul><ul><ul><li>Complicated biology and other factors </li></ul></ul>
- 22. Classifying the radiation dose is very complicated <ul><li>Biological effects depend on acute versus chronic dose </li></ul><ul><li>Interaction of radiation with cells has a number of possible outcomes…depends on numerous factors </li></ul><ul><ul><ul><li>Characteristics of the radiation </li></ul></ul></ul><ul><ul><ul><li>Characteristics of the biological system (e.g. general level of health) </li></ul></ul></ul><ul><li>Nevertheless, attempts are made to define dose </li></ul>
- 23. Radiation doses <ul><li>In terms of energy, absorbed dose is measured in grays (Gy) </li></ul><ul><ul><li>1 Gy = 1 joule per kilogram of material </li></ul></ul><ul><li>Biological dose is measured in sieverts (Sv) or rem </li></ul><ul><ul><li>1 Sv = effect of 1 joule per kilogram </li></ul></ul><ul><ul><li>1 Sv = 100 rem </li></ul></ul><ul><ul><li>1 sievert = Q * gray “Q” is some fudge factor </li></ul></ul><ul><li>For photons (x-ray, gamma) Q = 1 </li></ul><ul><li>Beta rays, Q = 1 </li></ul><ul><li>Low energy neutrons, Q = 5; medium energy Q = 20; high energy Q=5 </li></ul><ul><li>Alpha, Q = 20 </li></ul>
- 25. Some relevant radiation dose values <ul><li>Acute radiation dose </li></ul><ul><ul><li>About 3 Sv (whole body) will cause radiation poisoning and 50% chance of death. </li></ul></ul><ul><ul><li>Medical imaging procedures typically in the milli-sievert range </li></ul></ul><ul><li>Chronic radiation dose </li></ul><ul><ul><li>Natural background about 2.4 milli-Sv per year </li></ul></ul><ul><ul><li>What dose will cause cancer? Difficult to determine and also random . </li></ul></ul>
- 26. Medical applications of radiation Destruction: Radiation Therapy Imaging: X-rays Imaging: Positron emission tomography Imaging: Gastrointestinal imaging
- 27. Positron emission tomography (PET scanning)
- 28. Radiation Therapy <ul><li>Extremely high but localized dose, meant to destroy tumor cells. </li></ul><ul><li>20 or more localized grays </li></ul><ul><li>Also a “whole body” dose for killing immune system prior to bone-marrow transplant. </li></ul><ul><li>~ 10 grays (3 usually lethal) </li></ul>
- 29. Some slides about cancer radiation therapy http://youtube.com/watch?v=ZtENJI1K1hA&feature=related
- 30. Clicker Question—Acute Radiation Dose <ul><li>I said earlier that a dose of about 3 sieverts (Sv) will kill someone about 50% of the time. Let’s say someone is exposed to 100 sieverts of radiation. Can you say almost certainly they will die? </li></ul><ul><li>YES! </li></ul><ul><li>No! </li></ul>
- 31. Clicker Question—Acute Radiation Dose <ul><li>I said earlier that a dose of about 3 sieverts (Sv) will kill someone about 50% of the time. Let’s say someone is exposed to 100 sieverts of radiation. Can you say almost certainly they will die? </li></ul><ul><li>YES! </li></ul><ul><li>No! </li></ul>The information is not specific enough. If it happens over the whole body in a short time, then probably YES… However, if it happens over 100 years, then probably not. Also if localized, also will not die There is no easy way to put a concrete number on radiation dose
- 32. Ionizing radiation almost NEVER makes something turn radioactive! <ul><li>In order for an object to become radioactive, the nuclei in the atoms must change…”nuclear reactions” required. </li></ul><ul><li>Typically: </li></ul><ul><li>Neutrons are the most effective at causing nuclear transmutation… </li></ul><ul><li>Radiactive decay very rarely releases neutrons </li></ul>The person does NOT become radioactive … his nuclei are unchanged Nuclear reaction Releases ionizing radiation Causes Chemical reactions
- 33. Clicker question--transmutation <ul><li>Food irradiation or “cold pasteurization” often uses gamma rays to kill any microorganisms in the food. There are no neutrons involved. </li></ul><ul><li>Does the food then become radioactive (only mildly, though)? </li></ul><ul><li>Yes </li></ul><ul><li>No </li></ul>
- 34. Clicker question--transmutation <ul><li>Food irradiation or “cold pasteurization” often uses gamma rays to kill any microorganisms in the food. There are no neutrons involved. </li></ul><ul><li>Does the food then become radioactive (only mildly, though)? </li></ul><ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>There are safety concerns, but NOT because of radioactive food! We can understand the physics </li></ul><ul><li>The risks need to be balanced against the benefits…In US: </li></ul><ul><ul><li>325,000 hospitalized per year from food poisoning! </li></ul></ul><ul><ul><li>5,000 deaths / year! </li></ul></ul>
- 35. Protons and neutrons are made of quarks Quark model of a proton www2.cnrs.fr/presse/communique/709.htm “ Up” quarks charge = + 2/3 each “ Down” quark -1/3 charge Arpad Horvath Quark model of neutron
- 36. Quarks and Leptons are the constituent parts of matter. Murray Gell-Mann Nobel Prize 1969 There are six quarks Up Charmed Top Down Strange Bottom Charge = +2/3 Charge = -1/3 Similarly, there are six leptons Increasing mass Electron Muon Tau Electron neutrino Muon neutrino Tau neutrino Antimatter consists of the 6 anti-particle quarks and 6 anti-particle leptons
- 37. Under normal conditions, quarks do not exist in free space. Fermilab particle accelerator Billion-dollar physics experiments were required to detect quarks for fleeting instants in time
- 38. Beta-decay can transform a neutron into a proton Quarks (Electron) It is a decay of a “down quark” into an “up quark”
- 39. Clicker question--Quarks <ul><li>An up quark has an electric charge of +2/3. </li></ul><ul><li>A down quark has an electric charge of -1/3. </li></ul><ul><li>Which of the following combinations would a proton consist of? </li></ul><ul><li>Up, up, up </li></ul><ul><li>Down, down, down </li></ul><ul><li>Up, down, down </li></ul><ul><li>Up, up, down </li></ul><ul><li>Up, up, down, down </li></ul>
- 40. Clicker question--Quarks <ul><li>An up quark has an electric charge of +2/3. </li></ul><ul><li>A down quark has an electric charge of -1/3. </li></ul><ul><li>Which of the following combinations would a proton consist of? </li></ul><ul><li>Up, up, up </li></ul><ul><li>Down, down, down </li></ul><ul><li>Up, down, down </li></ul><ul><li>Up, up, down </li></ul><ul><li>Up, up, down, down </li></ul>+2/3 +2/3 -1/3 Take home message about quarks: Nucleons are composed of three quarks. Particle Physicists can predict a lot about matter from the quark / lepton models, Including some radioactive decay properties

No public clipboards found for this slide

Be the first to comment