natural purification (자정 작용
| natural language processing | Computer processing of a language with rules that reflect and describe current usage rather than prescribed usage. (12 Dec 1998) |
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| natural mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| natural passive immunity | Immunity conferred by the mother on the foetus or newborn. (14 Nov 1997) |
| natural pigment | A naturally occurring coloured compound; absorbs light in the visible range of the electromagnetic spectrum. Compare: structural colour. Synonym: biochrome. (05 Mar 2000) |
| natural products | Naturally occurring compounds that are end products of secondary metabolism; often, they are unique compounds for particular organisms or classes of organisms. (05 Mar 2000) |
| natural selection | The hypothesis that genotype environment interactions occurring at the phenotypic level lead to differential reproductive success of individuals and hence to modification of the gene pool of a population. (18 Nov 1997) |
| immunity, natural | The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from non-specific mechanisms such as genetic endowment, naturally occurring antiviral and bactericidal substances, phagocytosis, and constitutional factors such as body temperature, oxygen tension, and age. (12 Dec 1998) |
| killer cells, natural | Cells responsible for spontaneous cytotoxicity of a variety of tumour cells without prior immunization. These natural killer cells are found in non-immune humans and experimental animals and are thought by some to be the same as killer cells (killing by antibody-dependent cell cytotoxicity), but they can also kill in the absence of antibody. (12 Dec 1998) |
| agonal infection | An acute infection, commonly pneumonic or septic, occurring toward the end of any disease and often the cause of death. Synonym: agonal infection. (05 Mar 2000) |
| airborne infection | A mechanism of transmission of an infectious agent by particles, dust, or droplet nuclei suspended in the air. (05 Mar 2000) |
| apical infection | Implantation of microorganisms at the apex of a tooth, usually the result of the migration of microorganisms from the pulp canal through the apical foramen. (05 Mar 2000) |
| arbovirus infection | <virology> A type of viral infection that is transmitted by mosquitoes in late spring to early autumn. One manifestation is encephalitis (central nervous system infection). (27 Sep 1997) |
| ascariasis infection | <microbiology> Infection by the nematode Ascaris lumbricoides and is characterised by an early pulmonary phase related to larval migration and a later, prolonged intestinal phase. Adult worms are 15-40 cm in length and maintain themselves in the lumen of the small intestine. Infection occurs after ingesting eggs contained in contaminated food or more commonly, by transmission to the mouth by the hands after contact with contaminated soil. Treatment is with mebendazole or pyrantel pamoate. (27 Sep 1997) |
| atypical mycobacterial infection | <microbiology> Infection with organisms from the Mycobacterium genus other than tuberculosis. Risk factors include immunocompromised patients and those with AIDS. Mycobacterium avium intracellulare is an example which frequently infects AIDS patients. Atypical mycobacterial infections can cause abscesses, septic arthritis and osteomyelitis. Treatment can be difficult due to the emergence of resistance to standard antitubercular antibiotics. (27 Sep 1997) |
| bacterial infection | <microbiology> Bacteria are group of micro-organisms that are a single cell approximately 1 micron in transverse diameter. Some bacteria cause disease in man, requiring treatment with an antibiotic. (27 Sep 1997) |