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991.
Marshall E 《Science (New York, N.Y.)》1982,218(4576):976-977
992.
Methylation of tin by estuarine microorganisms 总被引:1,自引:0,他引:1
Mixed inoculums of microorganisms from Chesapeake Bay sediments transformed inorganic tin (SnCl(4) . 5H(2)O) to organotin compounds. Dimethyltin and trimethyltin species were identified as products by gas chromatography-mass spectrometry. Methylated tin species were not observed in sterile controls or in poisoned controls. Thus, estuarine microorganisms have the potential for transforming tin to toxic organotins and for mobilizing tin in the ecosystem. 相似文献
993.
Marshall E 《Science (New York, N.Y.)》1982,215(4540):1596-1597
994.
995.
996.
Bombardier beetles of the carabid subfamily Paussinae have a pair of flanges, diagnostic for the group, that project outward from the sides of the body. Behind each flange is a gland opening, from which the beetles discharge a hot, quinone-containing secretion when disturbed. The flanges are curved and grooved and serve as launching guides for anteriorly aimed ejections of secretion. Jets of fluid, on emergence from the gland openings, follow the curvature of the flanges and are thereby bent sharply in their trajectory and directed forward. The phenomenon is illustrative of the Coanda effect, widely applicable in engineering and responsible for the familiar tendency of liquids to curve around spouts and down the front of containers when being poured. 相似文献
997.
A laboratory strain of Drosophila mercatorum has existed for 20 years without males and therefore without natural selection operating to maintain the genetic basis of female mating behavior. The females of this strain have recently experienced a genetic impairment of mating capacity. This observation exemplifies the mode of evolution of vestigial characters and supports Muller's theory that random mutation will tend to destroy the genetic basis of a character from which selection has been removed. 相似文献
998.
Maugh TH 《Science (New York, N.Y.)》1982,217(4561):720-721
999.
The acceleration and extraction of uranium-238 nuclei by the Bevalac have been confirmed by their visual detection in nuclear research emulsion. A preliminary result for the collision mean free path for stopping uranium-238 (energy = 115 million electron volts per nucleon) is 3.1 +/- 0.6 centimeters. Qualitative characteristics of the observed uranium-nucleus collisions are also described. 相似文献
1000.
Bakker RT 《Science (New York, N.Y.)》1982,217(4554):53-55
Among extant large reptiles, juveniles often occupy different habitats from those of adults or subadults and thus avoid competition with and predation from the older animals; small juveniles often choose cryptic habitats because they are vulnerable to a wide variety of predators. Evidence from fossil humeri and femora of Early Permian reptiles collected from sediments of several distinct habitats indicate that similar shifts in habitat occurred. Juvenile Dimetrodon seem to have favored cryptic habitats around swamp and swampy lake margins; adults favored open habitats on the floodplains. Similar patterns of habitat shift seem to be present in the reptile Ophiacodon and the amphibian Eryops and may have been common in fossil tetrapods of the Permian-Triassic. 相似文献