potassium 40

po·tas·si·um 40 (40K),

A naturally occurring (0.0117%) radioactive potassium isotope; beta emitter with half-life of 1.26 billion years; chief source of natural radioactivity of living tissue.
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Urine studies were significant for urine pH of 5, urine anion gap of -1 (urine sodium 80 mmol/L, urine potassium 40 mmol/L, and urine chloride 121 mmol/L), and transtubular potassium gradient of 18 (serum osmolality 275 mosm/dL/L, urine osmolality 380 mosm/dL, urine potassium 40 mmol/L, and serum potassium 1.6 mmol/l), and both urine protein and glucose were negative.
An average, Human has about 30 milligrams of potassium 40 that has a half life of 5730 years [2].
According to doctoral student, Daniel Madigan, who studies the migration patterns of tuna at Stanford University, they didn't bring much, the levels were far lower than, for instance, levels of naturally occurring potassium 40 that have existed in the ocean for centuries, but the radioactivity was enough to survive the fishes' migration east to North America from the Western Pacific, which they undertake when they're around a year old.
Radiometrics: This technique breaks the natural gamma ray spectrum into individual components: potassium 40 (K), uranium 214 (U), thorium 208 (T) and total gamma (T).
The "K" in KI pills is potassium, a small percentage of which is radioactive Potassium 40. In an attempt to avoid barely detectable amounts of Iodine 131, they are ingesting easily measurable amounts of bone-seeking Potassium 40.
As examples, the half-life of radioactive carbon, carbon 14, is 5730 years; and of radioactive potassium, potassium 40, is 1.25 billion years.
Some independent scientists think that 64uSv from tritium is more dangerous than 64uSv from potassium 40. This is because tritium gives very many low-energy radioactive emissions which have high probability of affecting the DNA and cell replication.
Potassium 40 and radon were also detected, but at levels similar to those occurring in nature, they said.
By comparatively measuring how much potassium 40 had decayed into argon 40, paleontologists date rock samples as old as 50 million years with just a 5 percent error.
La radioactivite moyenne du potassium 40 (n = 65) dans les tissus musculaires etait de 83,0 Bq/kg, et elle variait largement, de 76,0 a 104,4 Bq/kg selon les emplacements.
Potassium, in general, is a combination of three isotopes among which only the isotope Potassium 40 is radioactive and its half -life is 1/28 x [10.sup.9].
Thus all the heat from radioactive decay comes from the crust and mantle - about eight terawatts from uranium 238 (238U), another eight terawatts from thorium 232 (232Th), and four terawatts from potassium 40 (40K).