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911.
Two women not only lost relatively large amounts of amniotic fluid immediately following genetic amniocentesis, but continued to lose fluid for the remainder of their pregnancies. Periodic ultrasonographic assessment confirmed normal fetal growth and presence of some amniotic fluid. Both women were delivered at term of normal offspring who showed no evidence of fetal deformations. Although amnionitis is a risk, cautious surveillance may permit continuation of pregnancies complicated by copious or persistent amniotic fluid leakage following genetic amniocentesis.  相似文献   
912.
The diunsaturated C12 alcohol (Z,Z)-dodeca-3,6-dien-1-ol (dodecadienol) has been characterized by GC-MS and FTIR as a novel releaser pheromone in termites. This alcohol identified in Ancistrotermes pakistanicus (Termitidae, Macrotermitinae) possesses a double pheromonal function which again illustrates the chemical parsimony of termites compared with other social insects. In workers, dodecadienol elicits trail-following at a very low concentration (activity threshold at 0.1 pg/cm of trail); in male alates it induces trail-following at a low concentration (1–10 pg/cm) and sexual attraction at a higher concentration (about 1 ng). Traces of the monounsaturated C12 alcohol (Z)-dodec-3-en-1-ol (dodecenol), known as a trail pheromone of several Macrotermitinae, were also found in the sternal gland extracts of A. pakistanicus, although only dodecadienol was present at the surface of the sternal gland. Workers of A. pakistanicus are not sensitive to dodecenol, but they are as sensitive to dodecatrienol as to dodecadienol. However, in the study area (Vietnam), A. pakistanicus is living in sympatry only with those Macrotermitinae using dodecenol as a trail pheromone, the foraging populations therefore being well isolated through their respective trail pheromones. The presence of three types of unsaturated C12 alcohols as releaser pheromones in the only Macrotermitinae subfamily is discussed, and a possible biosynthetic pathway from linoleic acid is proposed for dodecadienol.  相似文献   
913.
应对不确定性:呼吁建立新的科学政策论坛   总被引:4,自引:1,他引:4  
科学界和政策界具有不同的目标,这就自然导致了对构成某种变化或现象的"检验"标准的差异,以及用不同的方法去描述不确定性和风险的持性及传达不确定性和风险.这些差异可能损害科学家、决策者和公众之间的有效沟通,同时也限制了科学家所愿意研究的社会紧迫问题的类型.本文主要回顾了一系列处理不确定性问题的方法,阐述了当科学和政策不能很好协调时所可能引起的一些错误.并在此基础上,特别针对解决不确定性问题提出了一些具体建议,包括重构科学规范,建立由科学、政策两方面领导广泛参加的科学政策论坛.  相似文献   
914.
Complex, highly integrated societies have evolved from simpler societies repeatedly, and the social insects provide an excellent model system for understanding increasing complexity and integration. In the paper wasps, large societies, known as swarm-founding, have evolved repeatedly from smaller societies, known as independent-founding. Swarm-founding colonies have many more queens than independent-founding colonies, which should dramatically reduce relatedness, posing a challenge to cooperation. However, in each instance, swarm-founding species have also evolved a cyclical pattern of queen reduction which elevates relatedness despite high queen numbers. The genus Ropalidia provides an excellent system in which to study the transition to swarm-founding because it has both independent and swarm-founding species. We studied the Australian independent-founding wasp Ropalidia revolutionalis to better understand the evolution of multiple queens and their periodic reductions in swarm-founding wasps. Using microsatellite genetic markers we genotyped queens, workers and brood from 37 colonies and found that while most colonies had a single queen, three of the colonies had multiple queens at or immediately prior to the time of collection. An additional seven colonies had had multiple co-occurring queens earlier in the season. We also found that colonies experienced many queen losses, and that founding queens were gradually lost until they were replaced by a new cohort of daughter queens in many colonies. This pattern is similar to the periodic reductions and replacements in swarm-founding wasps and suggests that multiple queens and queen cycling evolved relatively early in the shift to swarm-founding in Ropalidia.Communicated by R. Page  相似文献   
915.
We investigated whether female association preferences for males are influenced by black spot disease (BSD), a parasite induced change of the host phenotype. We compared three different species of fish: a gynogenetic hybrid species, Poecilia formosa (amazon molly) and two sexual species (Poecilia latipinna and Poecilia mexicana), which were involved in the natural hybridisation leading to the amazon molly. Contrary to their sexual relatives, asexual amazon mollies significantly avoided images of males infected with black spot disease. We propose that amazon molly females have direct fitness benefits from choosing healthy males. The adaptive significance of the preference for BSD-uninfected males in the asexual amazon molly is yet unclear but may involve avoidance of predation or parasite infection as well as increased sperm availability.  相似文献   
916.

Aim and Scope

This study was aimed at evaluating environmental effects of tar-oil impregnated (tanalized) tree stakes using simple and efficient biotests to obtain results of its ecological impacts during the tar-oil breakdown in the stake.

Results

  1. Soil respiration was measured in-situ as an indication of soil microbial activity in two field trials. Soil respiration was measured in a 20 year-old apple orchard at various distances from the tar-oil impregnated tree stakes and also on soil mixed with chippings from pine stakes with tar-oil impregnation of different ages.
  2. Cress germination tests were employed to evaluate tar-oil phytotoxicity in a field and laboratory trial. Cress was seeded close to tree stakes in the same 20 year-old apple orchard and germination rates related to tar oil-impregnation. Cress was also seeded in trays in sand mixed with pine chippings from stakes with tar-oil impregnation of different ages.
  3. The portion of the carcinogenic benzoapyrene (BaP) ranged between 0.0015% in freshly tar-oil impregnated to 0.4% in tar-oil impregnated 20-year old trees stakes, i.e. irrespective of the overall PAK concentration and its degradation.
  4. Kinetic analysis using DIXON plots showed a 50% breakdown of overall PAHs after ca. 2.7 years, i.e. km or Ki values of less than 3 years.

Conclusion

Germination tests of cress and endogenous seeds as well as soil respiration proved sensible indicators of the phytotoxicity and ecotoxicity of tar-oil impregnated tree stakes in fruit orchards. Soil respiration proved particularly sensitive to tar-oil ageing. Its combination with kinetic inhibition models resulted in parameters suitable for the interpretation of results.  相似文献   
917.
Nucleotide variation in cytochrome c oxidase subunit I (COI) was used to examine population structure in three invasive bryozoans: Bugula neritina (Linnaeus, 1758), Watersipora subtorquata (d’Orbigny, 1852), and W. arcuata (Banta, 1969). These species are found on ship hulls and have a short (≤2 days) larval phase. Samples were collected from 1998–2001 at multiple sites in Australia, and in Hong Kong, New Zealand, Hawaii, California, Curaçao, and England. B. neritina is known to include three cryptic species, including species Type S (Davidson and Haygood in Biol Bull 196:273–280, 1999) which occurs on the east and west coasts of the USA. One haplotype recorded previously in the USA, S1, was found to be widespread, occurring throughout Australia and in Hong Kong, Curaçao, Hawaii, and England. W. subtorquata, a Caribbean–Atlantic species which has invaded southern Australia, New Zealand, and California, had low nucleotide diversity in these areas (π=0.0016±0.0014), consisting of three haplotypes connected by one or two nucleotide mutations. W. arcuata, an Eastern-Pacific native, had comparatively high diversity (π=0.0221±0.0115) in introduced populations from Australia and Hawaii. In each species, identical haplotypes were identified on separate coastlines providing evidence of widespread, rather than genetically independent, introductions. The major contrast in nucleotide diversity suggests that different propagule-source models explain introductions.  相似文献   
918.
Bottlenose dolphins (Tursiops truncatus) face a variety of threats, including risk of exposure to brevetoxins produced by blooms of the harmful alga Karenia brevis. This study investigated brevetoxin exposure in a population of dolphins inhabiting Sarasota Bay, Florida, USA (27°N, 82°W), utilizing tissues from dolphins recovered between 1994 and 2003. Brevetoxin levels detected by ELISA in tissues, gastric samples and excreta from dolphin carcasses (n = 19) associated with K. brevis blooms were compared with with levels in carcasses (n = 16) associated with background K. brevis conditions. In the K. brevis-exposed set, 84% of dolphin carcasses recovered during K. brevis blooms had detectable brevetoxin levels, with values ranging between 7 and 2,896 ng PbTx-3 eq g−1. Over 50% of dolphin carcasses recovered during non-bloom conditions also tested positive by ELISA for brevetoxins, with concentrations ranging from 6 to 44 ng PbTx-3 eq g−1. Control samples from the east coast of Florida were negative by the ELISA. Results from this study establish baseline brevetoxin body burdens in a dolphin population frequently exposed to K. brevis blooms, and data indicate that dolphin carcasses not associated with large-scale mortality events can contain levels of brevetoxins comparable to carcasses stranding during such events.  相似文献   
919.
920.
Relatively low concentrations of fluorine in drinking water ( 1 mg F/l) have been shown to significantly reduce the degree of dental caries in children and fluorine would also appear to have a beneficial effect on bone formation in both humans and farm animals. However, it is apparent that elevated levels of fluorine in the diet have sometimes resulted in problems of increased dental caries and of the development of bone deformities. Much of the fluorine in rocks and soils occurs in apatite and hydroxysilicate minerals, fluorite being the only relatively common rock forming mineral containing fluorine as an essential constituent.Little systematic data are available on fluorine concentrations in soils, plants and natural waters in the UK. General background soil concentrations lie in the range 200 – 400 mg F/kg. For waters the average fluorine content is low, <0.1 mg F/l.In the British Isles there are several areas where there are enhanced levels of fluorine. In the northern Pennines, Derbyshire, northeast Wales and Cornwall, fluorite occurs as a significant component of mineralisation and much fluorine has been added to the environment from mining waste dumps. Soils in northeast Wales contain up to 3,650 mg F/kg and in the northern Pennines up to 20,000 mg F/kg. Waters contain up to 2.3 mg F/l. In southwest England, the granites are generally fluorine-rich with the fluorite granites of the St Austell pluton containing as much as 1 percent fluorine. These rocks are frequently kaolinised and intensively worked as a source of china clay. Soils in the vicinity of the waste tips contain up to 3,300 mg F/kg and grasses up to 2,950 mg F/kg. Surface waters in the St Austell area contain up to 1.25 mg F/l.Atmospheric fluorine pollution around brickworks in the Peterborough and Bedford areas has resulted in fluorosis in farm animals. Other sources of atmospheric fluorine pollution are aluminium smelters, steelworks and fossil fuel burning.  相似文献   
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