| 单词 |
photopositive |
| 释义 |
photopositive, a.|fəʊtəʊˈpɒzɪtɪv|
Also with hyphen.
[f. photo- 1 + positive a. and n.]
1. Zool. Of an animal: tending to move towards light.
1914[see photonegative a. 1]. 1923Jrnl. Exper. Zool. XXVIII. 194 The photopositive reactions of insects under normal conditions usually result in their escape from places of danger. 1964Oceanogr. & Marine Biol. II. 482 The larvae [of Spirorbis] may settle or may resume their pelagic existence, again becoming photopositive for a short time. 1975[see photonegative a. 1].
2. Physics. Pertaining to or exhibiting an increase in electrical conductivity when illuminated.
1915[see photonegative a. 2]. 1932Hughes & DuBridge Photoelectric Phenomena viii. 328 The effect of light [on photoconducting substances] is usually to increase the conductivity (the photopositive effect..), but occasionally it is found that light apparently diminishes the conductivity (the photonegative effect..). The photonegative effect occurs above a critical voltage whose value depends on the temperature.
Hence photoˈpositively adv.; ˌphotoposiˈtivity.
1946Nature 13 July 58/2 When behaving photopositively Hydra orientates itself klinokinetically. 1962Jrnl. Insect Physiol. VIII. 251 Photopositivity declines continuously within each instar, but shows an increase after each moult. |
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