| equivalent temperature | The temperature of a thermally uniform enclosure in which, under still air conditions, a "sizable" black body loses heat at the same rate as in the nonuniform environment. (05 Mar 2000) |
|---|---|
| equivalent weight | The weight in grams of an element that combines with or replaces 1 gram of hydrogen, the atomic or molecular weight in grams of an atom or group of atoms involved in a chemical reaction divided by the number of electrons donated, taken up, or shared by the atom or group of atoms in the course of that reaction, the weight of a substance contained in 1 liter of 1 normal solution; a variant of. Synonym: combining weight, equivalent weight. (05 Mar 2000) |
| Joule's equivalent | The dynamic equivalent of heat; the amount of work converted to heat that will raise the temperature of 1 pound of water 1캟 is 778 foot-pounds; in metric units, 1 calorie, which raises 1 gram of water 1캜, equals 4.184 × 107 dyne-centimeters, which equals 4.184 joules. (05 Mar 2000) |
| lethal equivalent | A combination of selective effects that on average have the same impact on the composition of the gene pool as one death; e.g., two carriers at 50% risk of dying would be the lethal equivalent of one carrier at 100% risk, in the population genetics of recessive traits lethal equivalent is expressed as twice the sum of the expected number of deaths ascribable to the genetic load. Expression used of the genetic load of recessive genes in heterozygous state that if in homozygous state would cause death or carry a risk of death. The expected number of deaths from all such genes is expressed in lethal equivalent. (05 Mar 2000) |
| blood urea nitrogen | Blood urea nitrogen (BUN) is a metabolic by product (in the liver) from the breakdown of blood, muscle and protein. Blood urea nitrogen can be measured from a simple venipuncture specimen. Abnormal elevation in the blood urea nitrogen can indicate renal disease, dehydration, congestive heart failure, gastrointestinal bleeding, starvation, shock or urinary tract obstruction (by tumour or prostate gland). Low BUN level can indicate liver disease, malnutrition or a low protein diet. Normal BUN levels should be between 7 and 20 mg/dl (milligrams per decilitre). (27 Sep 1997) |
| carbon-nitrogen ligases | <enzyme> Enzymes that catalyze the joining of two molecules by the formation of a carbon-nitrogen bond. Registry number: EC 6.3 (12 Dec 1998) |
| carbon-nitrogen ligases with glutamine as amide-n-donor | <enzyme> Enzymes that catalyze the joining of glutamine-derived ammonia and another molecule. The linkage is in the form of a carbon-nitrogen bond. Registry number: EC 6.3.5 (12 Dec 1998) |
| carbon-nitrogen lyases | <enzyme> Enzymes that catalyze the cleavage of a carbon-nitrogen bond by means other than hydrolysis or oxidation. Subclasses are the ammonia-lyases, the amidine-lyases, the amine-lyases, and other carbon-nitrogen lyases. Registry number: EC 4.3 (12 Dec 1998) |
| genes, nitrogen fixation | Regulatory and structural genes present in certain bacteria, algae and fungi that control the conversion of atmospheric nitrogen into biologically usable compounds; include nif structural genes (e.g., nifd, nifh) for nitrogenase and nitrate reductase as well as regulator genes nifa, nifb, ntra, ntrb, ntrc. Some are responsible for regulating transcription of genes involved in the assimilation of poor nitrogen sources in enteric bacteria. (12 Dec 1998) |
| rest nitrogen | The nitrogen content of other than protein bodies; e.g., about one-half the nonprotein nitrogen in the blood is contained in urea. Synonym: rest nitrogen. (05 Mar 2000) |
| heavy nitrogen | The less common stable nitrogen isotope, making up 0.37% of natural nitrogen. Synonym: heavy nitrogen. (05 Mar 2000) |
| nitrogen | <chemistry> A colourless nonmetallic element, tasteless and odorless, comprising four fifths of the atmosphere by volume. It is chemically very inert in the free state, and as such is incapable of supporting life (hence the name azote still used by French chemists); but it forms many important compounds, as ammonia, nitric acid, the cyanides, etc, and is a constituent of all organised living tissues, animal or vegetable. Symbol N. Atomic weight 14. It was formerly regarded as a permanent noncondensible gas, but was liquefied in 1877 by Cailletet of Paris, and Pictet of Geneva. Origin: L. Nitrum natron + -gen: cf. F. Nitrogene. See Niter. Source: Websters Dictionary (01 Mar 1998) |
| nitrogen-13 | A cyclotron-produced, positron-emitting radioisotope of nitrogen with a half-life of 9.97 minutes; used in protein metabolism studies and in positron-emission tomography. (05 Mar 2000) |
| nitrogen-14 | The common nitrogen isotope, making up 99.63% of natural nitrogen. (05 Mar 2000) |
| nitrogen-15 | The less common stable nitrogen isotope, making up 0.37% of natural nitrogen. Synonym: heavy nitrogen. (05 Mar 2000) |