Isotopes of helium a thousand times lower than helium-4 (2.17 K). This difference is explained by quantum statistics, since helium-3 atoms are fermions, while helium-4 atoms are bosons, which condense to a superfluid more easily. The most common isotope, , is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized nuclei. is an unusually stable nucleus because its nucleons are arranged into complete shells. It was also formed in enormous quantities during Big Bang nucleosynthesis. Terrestrial helium consists almost exclusively (99.99986%) of this isotope. Its boiling point of 4.2 K is the lowest of
The Elements of Programming Style The Elements of Programming Style The Elements of Programming Style, by Brian W. Kernighan and P. J. Plauger, is a study of programming style, advocating the notion that computer programs should be written not only to satisfy the compiler or personal programming "style", but also for "readability" by humans, specifically software maintenance engineers, programmers and technical writers. It was originally published in 1974. The book pays explicit homage, in title and tone, to "The Elements of Style", by Strunk & White and is considered a practical template promoting Edsger Dijkstra's structured programming discussions. It has been influential and has spawned