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Infobox references. Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) molecular ion with the chemical formula NH+ 4 or [NH4]+. It is formed by the addition of a proton (a hydrogen nucleus) to ammonia (NH3).
Dissimilatory nitrate reduction to ammonium is a two step process, reducing NO 3 − to NO 2 − then NO 2 − to NH 4 +, though the reaction may begin with NO 2 − directly. [1] Each step is mediated by a different enzyme, the first step of dissimilatory nitrate reduction to ammonium is usually mediated by a periplasmic nitrate reductase.
Glossary of nautical terms (M–Z) () This glossary of nautical terms is an alphabetical listing of terms and expressions connected with ships, shipping, seamanship and navigation on water (mostly though not necessarily on the sea). Some remain current, while many date from the 17th to 19th centuries. The word nautical derives from the Latin ...
Ammonia was first detected in interstellar space in 1968, based on microwave emissions from the direction of the galactic core. [172] This was the first polyatomic molecule to be so detected. The sensitivity of the molecule to a broad range of excitations and the ease with which it can be observed in a number of regions has made ammonia one of ...
AAW An acronym for anti-aircraft warfare. aback (of a sail) Filled by the wind on the opposite side to the one normally used to move the vessel forward.On a square-rigged ship, any of the square sails can be braced round to be aback, the purpose of which may be to reduce speed (such as when a ship-of-the-line is keeping station with others), to heave to, or to assist moving the ship's head ...
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation ...
This glossary of physics is a list of definitions of terms and concepts relevant to physics, its sub-disciplines, and related fields, including mechanics, materials science, nuclear physics, particle physics, and thermodynamics. For more inclusive glossaries concerning related fields of science and technology, see Glossary of chemistry terms ...
Energy flow is the flow of energy through living things within an ecosystem. [1] All living organisms can be organized into producers and consumers, and those producers and consumers can further be organized into a food chain. [2][3] Each of the levels within the food chain is a trophic level. [1] In order to more efficiently show the quantity ...