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951.
Using the example of bats inhabiting the Volga region, the cases in which the anthropogenic factor creates favorable conditions for these animals or significantly reduces their diversity of their fauna are considered. In this context, an opinion concerning the approaches to the conservation of bats is formulated.  相似文献   
952.
A mathematical model was constructed to simulate the processes of 137Cs migration in peat soils and its uptake by vegetation. Model parameters were assessed and the pattern of 137Cs distribution over soil profile was predicted in case of peat soils, which are typical of the Russian regions contaminated after the Chernobyl accident. The ecological half-life of 137Cs in the plant-root soil zone was calculated, and a long-term prognosis of the radionuclide uptake by plants was made.  相似文献   
953.
Preimplantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis for couples at risk of transmitting genetic disorders to their offspring. We present a fluorescence in situ hybridization (FISH) analysis of embryos obtained after seven PGD cycles in six couples with Robertsonian translocations and male factor infertility: 4 der(13;14), 1 der(14;21) and 1 der(15;21). Of 74 metaphase II (MII) injected oocytes, 61 (82.4%) fertilized normally and cleaved. Of these, 37/61 (60.7%) embryos were of high morphological quality with ≥6 blastomeres. After biopsy of 44 embryos at day 3 of development, seven degenerated, seven arrested in development and 30/44 (68.2%) evolved, of which 25/30 (83.3%) reached the morula/blastocyst stage. Analysis of biopsied blastomeres showed 23/44 (52.3%) of normal/balanced embryos, of which 15 (11 at the morula/blastocyst stage) were transferred in six cycles. One term pregnancy was achieved, which ended by cesarean section at 37 weeks of gestation, giving birth to two healthy newborn. Analysis of 49 embryos (excluding 12 inconclusive cases) showed a predominance of alternate segregation (38/49, 77.6%) over adjacent segregation (7/49, 14.3%), with one (2%) being a polyploid mosaic and three (6.1%) chaotic. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
954.
Microorganisms capable of degrading monocyclic and polycyclic aromatic hydrocarbons and several chlorinated aromatic compounds were isolated from soils polluted with industrial waste from chemical plants. They were identified as representatives of the genera Pseudomonas, Flavobacterium, Alcaligenes, Rhodococcus, Microbacterium, Cellulomonas, Arthrobacter, and Brevibacterium. Among them, bacteria capable of utilizing xenobiotics in a wide range of ambient temperatures and pH and in the presence of high sodium chloride concentrations were revealed.  相似文献   
955.
In order to estimate risk to human populations from environmental pollutants, it is necessary to have sound data on the concentrations of chemicals of concern in the affected media and knowledge of exposures of critical population subgroups to these chemicals. The Southeast Ohio Study is developing systematic and scientifically defensible methods for obtaining data on environmental concentrations in various media in the vicinity of critical receptors. This paper describes the study, discusses the technical approaches and gives some preliminary results.  相似文献   
956.
ABSTRACT A weir system with a proportional sampler for use on miniature watershed ecosystems is described. Eight weir collection systems were evaluated for their ability to measure and sample inputs and outputs of soil-island ecosystems which occur on granite outcrops. The proportion of water actually collected by the weir systems was generally less than the proportion the systems were designed to sample, but adequate for supplying data needed for estimating elemental budgets. The weir systems were not able to account for 25 to 50 percent of the variation in total water passing over the cutoff wall. Several ways of improving overall performance of the weir systems are discussed.  相似文献   
957.
958.
A symbiotic relationship between a damselfish (Stegastes fasciolatus) and 2 surgeonfishes (Acanthurus lineatus and A. leucosternon) is described. The damselfish, which is about 1/10 the size of the surgeonfishes, is concentrated in, and appears to prefer to be in, the feeding areas of the surgeonfishes. There is an average of one adult damselfish per adult surgeonfish feeding area. All 3 species defend their feeding areas against conspecifics and various other fishes that have similar diets, but there are few aggressive interactions between the cohabitants. Most of the interspecific defense of cohabited areas is provided by the surgeonfishes. The cohabitant species eat the same types of benthic microalgae, but only the damselfish eats microcrustaceans. It appears that the net cost to a surgeonfish of having a damselfish in its feeding area is very low because (1) biomass density of the damselfish is low, (2) it uses some food that the surgeonfishes do not use, and (3) it makes a small contribution to the defense of shared feeding areas. Even if there is a cost to the surgeonfish, the small size of the damselfish would allow it to take shelter from the surgeonfish, thus making it too costly for the surgeonfish to exclude it. Such cohabitation relationships, which may be quite common among reef fishes, represent a means by which the coexistence of species that use the same limiting resources is achieved.  相似文献   
959.
A small 2, 271-1 (600-gallon) prototype recirculating marine water system was designed and evaluated (26 months). The system employed a quaternary (mechanical, algal, bacterial and chemical) series of processing units with the aim of achieving long-term seawater quality and constancy without water replacement. Total ammonia (0.05±0.005 ppm), un-ionized ammonia (0.0036±0.0003 ppm), nitrite (0.10±0.014 ppm), nitrate (24.6±2.0 ppm), phosphate (14.0±2.1 ppm), dissolved oxygen (6.5–7.2 mg/l) and pH (7.80 to 8.25) were maintained at acceptable levels for the entire period. The biomass load (1.82 kg/397 l) consisted of 4 nurse sharks which were fed ad-lib twice a week. Further, low levels of total bacteria (1.5×102 bacteria/ml) and coliforms [most probable number (MPN) index 17/dl] were present in the seawater. The system design is suggested for use in laboratory and mariculture installations.  相似文献   
960.
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