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101.
JINDŘIŠKA BOJKOVÁ KLÁRA KOMPRDOVÁ TOMÁŠ SOLDÁN SVĚTLANA ZAHRÁDKOVÁ 《Freshwater Biology》2012,57(12):2550-2567
1. Rapid expansion and intensification of anthropogenic activities in the 20th century has caused profound changes in freshwater assemblages. Unfortunately, knowledge of the extent and causes of species loss (SL) is limited due to the lack of reliable historical data. An unusual data set allows us to compare changes in the most sensitive of aquatic insect orders, the Plecoptera, at some 170 locations in the Czech Republic between two time periods, 1955–1960 and 2006–2010. Historical data (1890–1911) on assemblages of six lowland rivers allow us to infer even earlier changes. 2. Regional stonefly diversity decreased in the first half of the 20th century. Streams at lower altitudes lost a substantial number of species, which were never recovered. In the second half of the century, large‐scale anthropogenic pressure caused SL in all habitats, leading to a dissimilarity of contemporary and previous assemblages. The greatest changes were found at sites affected by organic pollution and a mixture of organic pollution and channelisation or impoundment. Colonisation of new habitats was observed in only three of the 80 species evaluated. 3. Species of moderate habitat specialisation and tolerance to organic pollution were most likely to be lost. Those with narrow specialisations in protected habitats were present in both historical and contemporary collections. 4. Contemporary assemblages are the consequence of more than a 100 years of anthropogenic impacts. In particular, streams at lower altitude and draining intensively exploited landscapes host a mere fragment of the original species complement. Most stonefly species are less frequently present than before, although their assemblages remain almost intact in near‐natural mountain streams. Our analyses demonstrate dramatic restriction of species ranges and, in some cases, apparent changes in altitudinal preference throughout the area. 相似文献
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Choice certainty is a probabilistic estimate of past performance and expected outcome. In perceptual decisions the degree of confidence correlates closely with choice accuracy and reaction times, suggesting an intimate relationship to objective performance. Here we show that spatial and feature-based attention increase human subjects' certainty more than accuracy in visual motion discrimination tasks. Our findings demonstrate for the first time a dissociation of choice accuracy and certainty with a significantly stronger influence of voluntary top-down attention on subjective performance measures than on objective performance. These results reveal a so far unknown mechanism of the selection process implemented by attention and suggest a unique biological valence of choice certainty beyond a faithful reflection of the decision process. 相似文献
104.
目的:研究铼.188标记生物分子在肿瘤治疗中的应用。方法:选取小白鼠作为实验的研究对象,将荷瘤鼠的肉瘤切成小块接种到小白鼠身上,达到试验条件时使用,即将没有明显差异的小白鼠16只随机分为4组,每组4只,注射含有铼一188的药物后分别在不同的时间将其处死,之后取出重要器官进行测量分析,进而得出铼一188的应用效果。结果:瘤内注射的要去在不同时间放射性在瘤内的保持率分别为(90.5±7.7)D%(1h),(92.2±8.6)D%(24h),(88.3±10.9)D%(48h)和(91.5±7.6)D%(72h),在荷瘤鼠内注入生理盐水、非放硫化铼和188Re.硫化铼混悬液,肿瘤质量分别为2885.3±1241.3、2839.9±1965.2和98.4±45.5mg。188Re-硫化铼混悬液在生理盐水、磷酸盐缓冲液和小牛血清中均可稳定72h,而且188W-188Re发生器的应用还可以降低188Re-硫化铼混悬液的价格。随着处死时间的延迟,小鼠肿瘤质量和体积逐渐减小,相临两组比较,后组测定值均明显小于前组,数据经统计学比较具有显著差异(P〈0.05)。结论:188Re-硫化铼混悬液是一种适宜的肿瘤治疗剂。 相似文献
105.
Parts L Hedman ÅK Keildson S Knights AJ Abreu-Goodger C van de Bunt M Guerra-Assunção JA Bartonicek N van Dongen S Mägi R Nisbet J Barrett A Rantalainen M Nica AC Quail MA Small KS Glass D Enright AJ Winn J;MuTHER Consortium Deloukas P Dermitzakis ET McCarthy MI Spector TD Durbin R Lindgren CM 《PLoS genetics》2012,8(5):e1002704
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107.
Background
In August 2006 a major epidemic of bluetongue virus serotype 8 (BTV8) started off in North-West Europe. In the course of 2007 it became evident that BTV8 had survived the winter in North-West Europe, re-emerged and spread exponentially. Recently, the European Union decided to start vaccination against BTV8. In order to improve the understanding of the epidemiological situation, it was necessary to execute a cross-sectional serological study at the end of the BT vector season. Cattle were the target species for cross-sectional serological studies in Europe at the end of 2006 and 2007. However, there was no information on the BTV8-seroprevalence in sheep and goats. 相似文献108.
Dependence on wild seed sources is often impractical for large‐scale habitat restoration programs. Reliance on commercial seed supplies of unknown provenance and fitness is thereby warranted. Little consideration has been given, however, to how the large volumes of seed required should be sourced. We evaluated commercial and locally collected seed sources for potential use in a New York State‐based, landscape‐scale program for restoring blue lupine Lupinus perennis. Through analysis of microsatellite markers we determined that “native” lupine designations by some commercial suppliers were in fact interspecific hybrids and therefore unreliable; at least two commercial sources, however, were genetically as close to native New York populations as native New York populations were to one other. Common garden experiments revealed that seed source influenced first‐year overwintering survival and subsequent height growth of surviving plants; seed sources more closely related genetically to native New York populations survived better and produced more stems per individual in the field in the area targeted for restoration. We conclude that (1) commercial suppliers often but not always offer reliably characterized seed sources of sufficient genetic similarity to native populations to warrant their use in restoration projects and (2) genetic affinity of potential seed stock to native populations is positively related to its fitness in the environment targeted for restoration. 相似文献
109.
S L Lilleberg S D Killilea D A Vaske R A Leopold R B Sparks 《Biochemical and biophysical research communications》1991,174(2):497-503
During embryonic development of Musca domestica inactive ornithine decarboxylase protein appears in the embryos at 6 h postoviposition, increases in concentration and reaches a maximum level at 9 h postoviposition. The inactive enzyme is associated with the plasma membrane and appears to be the precursor for active ornithine decarboxylase, which is associated with the cytosolic fraction just prior to hatching. Both ornithine decarboxylase protein and enzymatic activity disappear during the early larval stage of this insect. 相似文献
110.