| HF | Hageman factor; haplotype frequency; hard filled [capsule]; hay fever; head of fetus; head forward; ... |
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| HPLC | high-performance liquid chromatography; high-power liquid chromatography; high-pressure liquid chrom... |
| HT | Hashimoto thyroiditis; hearing test; hearing threshold; heart; heart transplantation, heart transpla... |
| CP | candle power; capillary pressure; cardiac pacing; cardiac performance; cardiopulmonary; caudate puta... |
| HEI | Health Effects Institute; high-energy intermediate; homogenous enzyme immunoassay; human embryonic i... |
| aromatic compound | Any compound in which the constituent atoms, or any part of them, form a ring. Used mainly in organic chemistry where: 1) numerous compound's contain rings of carbon atoms (carbocyclic compound's) or carbon atoms plus one or more atoms of other types (heterocyclic compound's), usually nitrogen, oxygen, or sulfur; 2) where the atoms in the ring are all of the same element (homocyclic or isocyclic compound); 3) where the ring is saturated or contains nonconjugated double bonds (alicyclic compound), the compound is similar in properties to the corresponding acyclic compound (e.g., cyclohexane resembles hexane); 4) where the ring contains conjugated double bonds in a closed loop in which there are 4n + 2 (where n is an integer) delocalised π electrons (Huckel's rule) (aromatic compound; e.g., benzene, pyridine), it is more stable than the corresponding saturated ring and exhibits unusual chemical properties characteristic of itself and not of other types of rings or of acyclic compound's. These aromatic compounds have the ability to sustain an induced ring current. Synonym: closed chain compound, ring compound. (05 Mar 2000) |
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| binary compound | <chemistry> This refers to any compound that is composed of only two elements. (09 Oct 1997) |
| binding energy | <chemistry, radiobiology> The binding energy of a nucleus is the minimum energy required to dissociate it into its component neutrons and protons. Neutron or proton binding energies are those required to remove a neutron or proton, respectively, from a nucleus. Electron binding energy is that required to remove an electron from an atom or a molecule. (16 Dec 1997) |
| bioelectric energy sources | Implantable devices which convert biological energy (chemical energy of the metabolism of continuously regenerating body fluids or mechanical energy of periodic movements) to electrical energy. The sources include biogalvanic cells, biofuel cells, and ionic concentration cells. (12 Dec 1998) |
| biomass energy | See Bioenergy. (05 Dec 1998) |
| bond dissociation energy | This is the energy needed to break the bonds between two linked atoms. (09 Oct 1997) |
| bond energy | The energy needed to break a molecular bond. (09 Oct 1997) |
| calcium compound | Inorganic compounds that contain calcium as an integral part of the molecule. (12 Dec 1998) |
| carbamino compound | Any carbamic acid derivative formed by the combination of carbon dioxide with a free amino group to form an N-carboxy group, -NH-COOH, as in haemoglobin forming carbaminohemoglobin. (05 Mar 2000) |
| carbocyclic compound | See: cyclic compound. (05 Mar 2000) |
| radiant energy | Energy contained in light rays or any other form of radiation. (05 Mar 2000) |
| radiography, dual-energy scanned projection | A method of producing a high-quality scan by digitizing and subtracting the images produced by high- and low-energy X-rays. (12 Dec 1998) |
| Parallel Electron Energy Loss Spectroscopy | <technique> Electron energy loss spectroscopy analyses the inelastically scattered electrons present in the beam after it has been transmitted through the sample. An electron energy loss spectrum typically consists of a monatomic decreasing background on which are superimposed a number of peaks. Each peak is characteristic of the scattering process that has occurred in the sample. The peaks can be used to obtain information about the chemical composition and electronic structure of the sample. Electron energy loss spectra are acquired typically in a magnetic sector spectrometer located under the camera chamber of the transmission electron microscope. Spatial resolution is typically limited by the minimum probe diameter of the microscope. Electron energy loss spectroscopy tends to be complimentary to EDS in that it can be used to analyse very thin samples of low Z materials. Acronym: PEELS (05 Aug 1998) |
| genetic compound | In medical genetics, the presence of two different mutant alleles at the same loci. Synonym: genetic compound. (05 Mar 2000) |
| geothermal energy | Energy derived from the natural heat of the Earth contained in hot rocks, hot water, hot brines or steam. (05 Dec 1998) |