| models, chemical | Theoretical representations that simulate the behaviour or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment. (12 Dec 1998) |
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| water pollutants, chemical | Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water. (12 Dec 1998) |
| commodity chemical | <chemistry> Chemicals such as ethanol that have low monetary value and are thus sold primarily in bulk. (09 Oct 1997) |
| multiple chemical sensitivity | An acquired disorder characterised by recurrent symptoms, referable to multiple organ systems, occurring in response to demonstrable exposure to many chemically unrelated compounds at doses far below those established in the general population to cause harmful effects. No single widely accepted test of physiologic function can be shown to correlate with symptoms. (cullen mr. The worker with multiple chemical sensitivities: an overview. Occup med 1987;2(4):655-61) (12 Dec 1998) |
| hypophysectomy, chemical | Total or subtotal destruction of the pituitary gland by chemical injection. It is usually achieved by injection of ethyl alcohol via trans-sphenoidal cannulation under stereotaxic control. It is usually performed for the treatment of intractable pain. (12 Dec 1998) |
| defoliants, chemical | Herbicides that remove leaves from trees and growing plants. They may be either organic or inorganic. Several of the more persistent types have been used in military operations and many are toxic. (12 Dec 1998) |
| sympathectomy, chemical | Sympathectomy using chemicals (e.g., 6-hydroxydopamine or guanethidine) which selectively and reversibly destroy adrenergic nerve endings while leaving cholinergic nerve endings intact. (12 Dec 1998) |
| evolution, chemical | Chemical and physical transformation of the biogenic elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial biochemistry. It includes the mechanism of incorporation of biogenic elements into complex molecules and molecular systems, leading up to the origin of life. (12 Dec 1998) |