Biochemical characterization of the rat liver receptor for 2,3,7,8-TCDD - a comparison to the rat liver glucocorticoid receptor

An assessment of the physicochemical characteristics of the rat hepatic receptors for 2,3,7,8-TCDD and for corticosteroid hormones reveals striking analogies between both receptor systems.     

矿区生态重建中生物多样性与可持续发展

复合生态系统受自然、经济、社会三方面的影响，是在生态工程控制下的生态系统，其生物多样性也受生态工程的控制。本文以安太堡露天煤矿为例，讨论了复合生态系统生物多样性与可持续发展的关系。说明复合生态系统的生物多样性要求经济，生态，社会综合效益最佳，其建设必须以生境建设为基础，并以生态工程手段保持和调节植被结构，以使矿区得到真正可持续发展。     

BP人工神经网络模型在拉萨道路交通噪声预测中的应用

针对拉萨市道路交通噪声污染问题，运用人工神经网络理论和方法对拉萨市道路交通噪声的等效连续声级进行预测。经检验，计算值与实测值接近，从而为道路交通噪声的预测提供了一种新的途径。     

小拖压条热轧制工艺

介绍 550 - 17小拖压条制造由铸造工艺改为热轧制工艺的方法 ,阐述轧辊型槽设计的原则 ,分型面与排布角度的选择及导道安装。     

The adaptive significance of reoriented migration of chaffinches Fringilla coelebs and bramblings F. montifringilla during autumn in southern Sweden

Summary Reoriented autumn migration of chaffinches and bramblings occurs regularly in southernmost Sweden. The reoriented birds fly in a northeasterrly direction from the coast and inland, i.e. approximately opposite to the normal autumn migration direction. The daily peak of reoriented finch migration, as observed at inland sites 20–40 km from the coast, occurs on average 3.5 h later than the early morning departure in the normal migratory direction, and 1 h later than the peak of migration at the coast. According to trapping data the average weight of reoriented migrants and birds interrupting their migration at the coastline is significantly lower than the weight of migrants proceeding in the normal direction, and the proportion of yearlings seems to be larger in the former category. Censuses of flocks of resting finches showed that they mainly forage at stubble fields of summer rape Brassica napus, preferably fields surrounded by wooded vegetation offering shelter from predator attacks. Preferred food and habitats are mostly located inland, 20 km or more from the coast. These findings are consistent with the interpretation that reorientation constitutes an adaptive response by migrants with small fat reserves. When confronted with an ecological barrier, they return to suitable resting sites for restoring the fat reserves before crossing the barrier.     

Robustness in life history of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) across large scales: effects of spatially and temporally induced variability on population growth

Understanding the demography and function of biotope-forming seaweed species is of great importance for the conservation of the target species itself, as well as its associated organisms. The brown seaweed Ascophyllum nodosum is fundamental for the functioning of coastal marine ecosystems in the North Atlantic. In this study, we use a data-based size-classified matrix model to investigate the temporal and spatial variability in demography, and the environment-specific stochastic sensitivity and elasticity, of two A. nodosum populations, one in western Sweden and one on the Isle of Man in the Irish Sea. A significant difference between the two populations was that the Swedish population had comparably low and more variable stochastic population growth rate (λ _s). This pattern was partly explained by the relatively high and varying mortality rates during extreme ice-years in Sweden, and by the lower survival of small individuals during all years. There were also fewer large individuals in Sweden due to lower transitions to the larger size-classes and higher probability of shrinkage. Sensitivities were analogous in the two populations, and showed a high selection pressure for increased individual growth. Elasticities were also similar, with the exception that survival of the smallest individuals (i.e., transition a _1,1), had a higher elasticity on the Isle of Man. Overall, the stochastic growth rate (λ _s) was most sensitive to proportional changes in loop- (i.e., survival within size-class) and, to some extent, growth-transitions in both study areas. These results show that structurally and demographically diverging A. nodosum populations may be similarly sensitive to changes in vital rates. This, in turn, indicates a plastic life history of A. nodosum that may cope with large environmental variability. The results further suggest that environmental change affecting the survival or growth of the larger, reproductive A. nodosum individuals could have severe and regional effects on the abundance and biomass of this species, with potential negative effects on the biodiversity of the associated communities.     

Determinants of reproductive potential and population size in open populations of Patella vulgata

The importance of external and internal population processes in determining variation in reproductive output and variation in population size were quantified with model simulations for open populations of the sequentially hermaphroditic limpet Patella vulgata using field data from the Isle of Man and South West Ireland. Cross-correlation analyses of model outputs and elasticity analyses show that population dynamics are dominated by the effects of large females, and that recruitment adds little to reproductive output. However, populations experiencing low but highly variable recruitment appear male limited and recruitment pulses carrying young males into the population are correlated to reproductive output with a 2–5-year lag. We conclude that pulses in recruitment can be a major structuring force in these limpet populations, but site-specific post-recruitment processes will determine the relative importance of recruitment to population dynamics and the lag between recruitment and reproductive output.     

Autumn migratory fuelling: a response to simulated magnetic displacements in juvenile wheatears, Oenanthe oenanthe

Recent experiments exposing migratory birds to altered magnetic fields simulating geographical displacements have shown that the geomagnetic field acts as an external cue affecting migratory fuelling behaviour. This is the first study investigating fuel deposition in relation to geomagnetic cues in long-distance migrants using the western passage of the Mediterranean region. Juvenile wheatears (Oenanthe oenanthe) were exposed to a magnetically simulated autumn migration from southern Sweden to West Africa. Birds displaced parallel to the west of their natural migration route, simulating an unnatural flight over the Atlantic Ocean, increased their fuel deposition compared to birds experiencing a simulated migration along the natural route. These birds, on the other hand, showed relatively low fuel loads in agreement with earlier data on wheatears trapped during stopover. The experimental displacement to the west, corresponding to novel sites in the Atlantic Ocean, led to a simulated longer distance to the wintering area, probably explaining the observed larger fuel loads. Our data verify previous results suggesting that migratory birds use geomagnetic cues for fuelling decisions and, for the first time, show that birds, on their first migration, can use geomagnetic cues to compensate for a displacement outside their normal migratory route, by adjusting fuel deposition.