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961.
Mechanisms of changes in the numbers of red deer in the Caucasian State Biosphere Reserve (the northwestern Caucasus) were studied from 1958 to 2004 using simulation models developed on the basis of concepts concerning the combined effect of density-dependent and density-independent factors. The results show that changes in population numbers are accounted for by larger (more numerous) local subunits, with small groups remaining relatively stable. In the periods of depression, such a mechanism provides for the maintenance of the spatial population structure.  相似文献   
962.
Aluminium (Al), when present in high concentrations, has for long been recognised as a toxic agent to aquatic freshwater organisms,i.e. downstream industrial point sources of Al-rich process water. Today the environmental effects of aluminium are mainly a result of acidic precipitation; acidification of catchments leads to increased Al- concentrations in soil solution and freshwaters. Large parts of both the aquatic and terrestrial ecosystems are affected.In the aquatic environment, aluminium acts as a toxic agent on gill-breathing animals such as fish and invertebrates, by causing loss of plasma- and haemolymph ions leading to osmoregulatory failure. In fish, the inorganic (labile) monomeric species of aluminium reduce the activities of gill enzymes important in the active uptake of ions. Aluminium seems also to accumulate in freshwater invertebrates. Dietary organically complexed aluminium, maybe in synergistic effects with other contaminants, may easily be absorbed and interfere with important metabolic processes in mammals and birds.The mycorrhiza and fine root systems of terrestrial plants are adversely affected by high levels of inorganic monomeric aluminium. As in the animals, aluminium seems to have its primary effect on enzyme systems important for the uptake of nutrients. Aluminium can accumulate in plants. Aluminium contaminated invertebrates and plants might thus be a link for aluminium to enter into terrestrial food chains.  相似文献   
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964.
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an important cause of hereditary stroke. Mutations in the Notch3 gene are clearly causally linked to this progressive vascular disorder. Cerebral ischemic attacks, cognitive decline, strokes, and vascular dementia constitute the major manifestations of this disorder. This report details the prenatal detection of a Notch3 mutation in the fetus of a couple where the father had a known mutation in this gene. This is the first report of a prenatal diagnosis of CADASIL, and another example of a serious, highly penetrant, and relentlessly progressive degenerative genetic disorder presenting decades after birth and for which prenatal diagnosis is an option. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
965.
The reduction of SO2, HCl, and NO(x) concentrations using calcium magnesium acetate (CMA) as a novel sorbent in a simulated municipal waste incinerator flue gas was investigated. The reduction of individual SO2, HCl, and NO(x) concentrations was tested at 850 degrees C and it was found that CMA could reduce the SO2 concentration by 74%, HCl concentration by 64%, or NO(x) concentration by 94%. It was observed that individual SO2 or HCl capture increased with increasing initial oxygen concentration in the reacting gas or increasing sorbent input. NO(x) reduction decreased with increasing initial oxygen concentration in the reacting gas. The simultaneous reduction of SO2, HCl, and NO(x) concentrations by CMA was also investigated. It was found that CMA could simultaneously capture 60% SO2 and 61% HCl and reduce NO(x) concentrations by 26%, when the initial oxygen concentration in the reacting gas was 4%. During the simultaneous reduction of SO2, HCl, and NO(x), it was noted that as the initial oxygen concentration in the reacting gas increased, the efficiency of SO2 capture increased too, but the efficiency of HCl capture and the efficiency of NO(x) destruction decreased.  相似文献   
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969.
Populations of Mercenaria mercenaria (L.) from South Carolina, USA, and M. campechiensis (Gmelin) from the Gulf of Mexico, Florida, USA, were sampled in 1987. The two species differed at all of seven enzyme loci tested, as well as in the thickness of shell ridges and nacre color. The difference in lunule shape was not great, although differences in relative shell width, shell weight, and lunule size make morphometric discrimination between the species possible. Shell ridges, nacre color, and multivariate morphometrics in a sample of clams collected from the Indian River Lagoon on the Atlantic coast of Florida in 1985 do not assort independently. Individuals with thick ridges, white nacre, and/or campechiensis-like morphometrics have significantly different allele frequencies at most enzyme loci from individuals with thin ridges, purple nacre, and/or mercenaria-like morphometrics. The deviations are in the direction predicted from the analysis of the allopatric populations of M. mercenaria and M. campechiensis. M. mercenaria outnumber M. campechiensis in the Indian River sample, but the majority of the clams seem to be hybrids.Contribution No. 235 from South Carolina Marine Resources Center  相似文献   
970.
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