Dollar silver. The US Mint continues to make silver $1-denomination coins, but these are not intended for general circulation. The quantity of silver chosen in 1792 to correspond to one dollar, namely, 371.25 grains of pure silver, is very close to the geometric mean of one troy pound and one pennyweight. In what follows, "dollar" will be used as a unit of mass. A troy pound being 5760 grains and a pennyweight being 240 times smaller, or 24 grains, the geometric mean is, to the nearest hundredth, 371.81 grains. This means that the ratio of a pound to a dollar (15.52)
Presolar grains range of micrometers. Presolar grains consisting of the following minerals have so far been identified: The study of presolar grains provides information about nucleosynthesis and stellar evolution. Grains bearing the isotopic signature of "r-process" (rapid neutron capture) and alpha process (alpha capture) types of nucleosynthesis are useful in testing models of supernovae explosions. For example, some presolar grains (supernova grains) have very large excesses of calcium-44, a stable isotope of calcium which normally composes only 2% of the calcium abundance. The calcium in some presolar grains is composed primarily of Ca-44, which is presumably the remains of the extinct radionuclide