Mesoamerican Long Count calendar 18. Thus 0.0.1.0.0 does not represent 400 days, but rather only 360 days and 0.0.0.17.19 represents 359 days. The name "b'ak'tun" was invented by modern scholars. The numbered Long Count was no longer in use by the time the Spanish arrived in the Yucatán Peninsula, although unnumbered k'atuns and tuns were still in use. Instead the Maya were using an abbreviated Short Count. Long Count dates are written with Mesoamerican numerals, as shown on this table. A dot represents "1" while a bar equals "5". The shell glyph was used to represent the zero concept. The Long Count calendar required
Nitrogen fixation Nitrogen fixation Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia (NH) or related nitrogenous compounds. Atmospheric nitrogen, which is molecular dinitrogen (N), is relatively nonreactive and is metabolically useless to all but a few microorganisms. The fixation process converts N into ammonia, which is metabolized by most organisms. Nitrogen fixation is essential to life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing compounds. Therefore, as part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the