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Assignment 3 (2nd PDF from the portal)
Part A:
1. Food selection from USDA
Selected food: Chocolate chip, Branded (393124).
2. Mention amount of potassium in mg per 100g from USDA site
There is nearly about 309mg of K in 100g of the food taken (FoodData Central). 309mg = 309 x 10-3 grams K.
3. Calculation of k-isotopes in 52 grams of the food
52 grams of Chocolate Chips x 309 x 10-3 grams K/ 100 grams of Chocolate Chip = 160.68 x 10-3 grams K = 160.68 mg K.
4. Calculation of 40K from fact 1(given in the PDF)
160.68 x 10-3 grams K x 1.2 x 10-4 g 40K/ 1 gram K = 193 x 10-7 grams 40K = 19.3 x 10-6 g
Therefore, there is about 19.3 mg of 40K in 52 grams of Chocolate chip.
5. Calculation of radioactivity from fact 2
19.3 x 10-6 g 40K x 7.1. x 10-6 Ci / 1 gram 40K = 137.03 x 10-12 Ci
Hence, 52 grams of chocolate chip has only 137.03 x 10-12 curies or 137 pCi of radioactive decay.
6. Translation of picocuries in beta disintegration/minute
137 pCi x (2.2 disintegrations /min)/pCi = 301.4 disintegrations / minute (at least 4 chocolate chips are needed for this)
Part B:
1. Choose an animal, write down its weight in pounds and kilograms
Selected animal: one Big American Bison. Weight: 1544 pounds or 700kgs (Kock and Joel 627).
2. Calculation of total potassium in the animal in grams
Consider, there are 2 grams of potassium for every kilogram of body mass.
700-kilogram x 2 grams K/kilogram = 1400 grams K (all different isotopes) for an adult male American Bison.
3. Disintegration per second
1400 grams of potassium x 31 Bq / gram of K = ~ 43 x 103 Bq occur in an American Bison.
4. Total energy in keV
(43 x 103 d/ sec) x 560 keV/d = ~ 24 x 106 keV/sec
5. Conversion of keV in picojules
(24 x 106 keV/sec) x (1.6 x 10-4 pJ/keV) = 38.4 x 102 pJ/sec = 3916.8 pJ/sec
6. Calculation of picowatts into beta disintegration per minute
3916.8 pJ/sec = ~ 3917 picowatts, in an American Bison
References
Kock, Michael D., and Joel Berger. "CHEMICAL IMMOBILIZATION OF FREE-RANGINGNORTH AMERICAN BISON (BISON BISON) IN BADLANDS NATIONAL PARK, SOUTH DAKOTA." Journal of Wildlife Diseases 23.4 (1987): 625-633. < https://www.jwildlifedis.org/doi/pdf/10.7589/0090-3558-23.4.625 >
usda.gov, 2019. GoodData Central/Nutrients, Retrieved on 23rd November 2019 from: https://fdc.nal.usda.gov/fdc-app.html#/food-details/393124/nutrients