排序方式: 共有195条查询结果,搜索用时 15 毫秒
141.
The female genital morphology of the spiders in the araneoid genus Agriognatha (Tetragnathidae) is described and illustrated. The female genitalia of Agriognatha is characterized by a strong reduction of the sperm storage organs (spermathecae) and by the presence of a specialized distal compartment of the median membranous chamber that functions as a sperm storage organ (the posterior sac). The genital morphology of Agriognatha species is unique among Tetragnathidae and it provides robust synapomorphic evidence for the monophyly of genus. We discuss the phylogenetic implications of these new findings for the placement and monophyly of Agriognatha and for the monophyly of Tetragnathinae. 相似文献
142.
Mavrova ATs Denkova P Tsenov YA Anichina KK Vutchev DI 《Bioorganic & medicinal chemistry》2007,15(18):6291-6297
Novel bis(benzimidazol-2-yl)amines were synthesized using two methods and studied for antitrichinellosis activity. DFT calculations were performed in order to determine the geometry of molecules. All derivatives of 2-aminobenzimidazole exhibited higher activity in vitro against Trichinella spiralis larvae in regard to the activity of albendazole, moreover compounds 4f-i manifested antitrichinellosis effect, which surpassed five times the activity of albendazole. The in vivo screening of intestinal phase of the T. spiralis revealed 100% effectiveness of compounds 4g-i at oral dosages of 50 and 100mg/kgmw, while albendazole possesses 100% efficacy only at a dose of 100mg/kgmw. 相似文献
143.
144.
A new genus and species of ground-hornbill are described from the Late Tertiary (Late Miocene) fluviative deposits in Hadzhidimovo (Hadzhidimovo-1, or Hadzhidimovo-Girizite locality), in southwestern Bulgaria. The cranial half of a scapula and the distal third of a femur have been recovered. The morphology distinguishes the specimen from the recent species of Bucorvus, the closest genus. Most interesting is the morphology of the scapula (the holotype), which differs considerably from the ground-hornbills in some structures (e.g. the clavicular joint) while being surprisingly similar in other structures (e.g. the humeral articular joint). The last peculiarity may indicate that the fossil species was a more primitive form having relatively poorer flying capacity in comparison to other ground-hornbills. This first record of Bucerotidae in Europe proves the occurrence of the family in the Tertiary of the western parts of the Eurasian continent. It came from the richest Bulgarian locality of the Hipparion fauna, from which ca. 36 species of large mammals and birds are now known. 相似文献
145.
Lian Liu Xiaoting Xu Lei Zhang Yaoqi Li Nawal Shrestha Danilo M. Neves Qinggang Wang Hong Chang Xiangyan Su Yunpeng Liu Jianyong Wu Dimitar Dimitrov Zhiheng Wang Jianquan Liu 《Journal of Plant Ecology》2022,15(2):237
北半球高山和极地虎耳草属物种丰富度的地理格局:温度和生境异质性的作用
现代气候、生境异质性和长期气候变化对森林生态系统中分布的木本植物的物种丰富度格局的影响在以往研究中受到广泛关注,但对高寒-极地生态系统中的草本植物物种丰富度格局及其影响因素的研究仍较少。本研究旨在检验以往研究中基于物种丰富度和环境因子关系提出的假说是否能够解释高寒-极地地区典型草本植物-虎耳草属(Saxifraga)的物种丰富度格局。本研究利用全球437种虎耳草属物种分布数据,探讨了全部物种、广域和狭域物种丰富度格局的影响因素。采用广义线性模型和空间自回归模型,评估了现代气候、生境异质性和历史气候对虎耳草属物种丰富度格局的影响。采用偏回归分析了不同变量对物种丰富度的独立解释率和共同解释率,并检验了4种广泛使用的物种丰富度与环境关系模型对物种丰富度格局的解释能力。研究结果表明,温度与虎耳草属所有物种和广域物种的物种丰富度格局呈显著负相关关系,是影响物种丰富度格局最重要的环境因子,这可能反映了虎耳草属对其祖先温带生态位的保守性。生境异质性和末次冰期以来的气候变化是虎耳草属狭域物种丰富度空间变异的最佳预测因子。总体而言,包含5个预测变量的组合模型可以解释大约40%–50%的虎耳草属物种丰富度的空间变异。此外,进化和生物地理过程在虎耳草属物种丰富度格局形成方面可能发挥了重要作用,这有待进一步研究。 相似文献
146.
Jens Czolk Andreas Puetz Dimitar Kutsarov Manuel Reinhard Uli Lemmer Alexander Colsmann 《Liver Transplantation》2013,3(3):386-390
Window‐ or building‐integrated semi‐transparent solar cells are particularly interesting applications for organic photovoltaic devices. In this work, we present an easy‐to‐process inverted device architecture comprising fully solution processable poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) bilayer top‐electrodes for efficient semi‐transparent organic solar cells. By incorporating dyes with a complementary absorption to the light harvesting polymer poly[[9‐(1‐octylnonyl)‐9H‐carbazole‐2,7‐diyl]‐2,5‐thiophenediyl‐2,1,3‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl] (PCDTBT) into the PEDOT:PSS electrode, we achieve fully color neutral transparency perception and a color rendering index approaching 100. This makes the devices suitable for applications such as window shadowing or the integration into overhead glazing. 相似文献
147.
Himmelbach A Zierold U Hensel G Riechen J Douchkov D Schweizer P Kumlehn J 《Plant physiology》2007,145(4):1192-1200
Genetic transformation of crop plants offers the possibility of testing hypotheses about the function of individual genes as well as the exploitation of transgenes for targeted trait improvement. However, in most cereals, this option has long been compromised by tedious and low-efficiency transformation protocols, as well as by the lack of versatile vector systems. After having adopted and further improved the protocols for Agrobacterium-mediated stable transformation of barley (Hordeum vulgare) and wheat (Triticum aestivum), we now present a versatile set of binary vectors for transgene overexpression, as well as for gene silencing by double-stranded RNA interference. The vector set is offered with a series of functionally validated promoters and allows for rapid integration of the desired genes or gene fragments by GATEWAY-based recombination. Additional in-built flexibility lies in the choice of plant selectable markers, cassette orientation, and simple integration of further promoters to drive specific expression of genes of interest. Functionality of the cereal vector set has been demonstrated by transient as well as stable transformation experiments for transgene overexpression, as well as for targeted gene silencing in barley. 相似文献
148.
It's a long way to the top: Plant species diversity in the transition from managed to old‐growth forests 下载免费PDF全文
Sabina Burrascano Francesco Ripullone Liliana Bernardo Marco Borghetti Emanuela Carli Michele Colangelo Carmen Gangale Domenico Gargano Tiziana Gentilesca Giuseppe Luzzi Nicodemo Passalacqua Luca Pelle Anna Rita Rivelli Francesco Maria Sabatini Aldo Schettino Antonino Siclari Dimitar Uzunov Carlo Blasi 《植被学杂志》2018,29(1):98-109
Questions
Do vascular plant species richness and beta‐diversity differ between managed and structurally complex unmanaged stands? To what extent do species richness and beta‐diversity relate to forest structural attributes and heterogeneity?Location
Five national parks in central and southern Italy.Methods
We sampled vascular plant species composition and forest structural attributes in eight unmanaged temperate mesic forest stands dominated or co‐dominated by beech, and in eight comparison stands managed as high forests with similar environmental features. We compared plant species richness, composition and beta‐diversity across pairs of stands (unmanaged vs managed) using GLMM s. Beta‐diversity was quantified both at the scale of each pair of stands using plot‐to‐plot dissimilarity matrices (species turnover), and across the whole data set, considering the distance in the multivariate species space of individual plots from their centroid within the same stand (compositional heterogeneity). We modelled the relationship between species diversity (richness and beta‐diversity) and forest structural heterogeneity and individual structural variables using GLMM s and multiple regression on distance matrices.Results
Species composition differed significantly between managed and unmanaged stands, but not richness and beta‐diversity. We found weak evidence that plant species richness increased with increasing levels of structural heterogeneity and canopy diversification. At the scale of individual stands, species turnover was explained by different variables in distinct stands, with variables related to deadwood quantity and quality being selected most often. We did not find support for the hypothesis that compositional heterogeneity varies as a function of forest structural characteristics at the scale of the whole data set.Conclusions
Structurally complex unmanaged stands have a distinct herb layer species composition from that of mature stands in similar environmental conditions. Nevertheless, we did not find significantly higher levels of vascular plant species richness and beta‐diversity in unmanaged stands. Beta‐diversity was related to patterns of deadwood accumulation, while for species richness the evidence that it increases with increasing levels of canopy diversification was weak. These results suggest that emulating natural disturbance, and favouring deadwood accumulation and canopy diversification may benefit some, but not all, facets of plant species diversity in Apennine beech forests.149.
Probabilistic maturation reaction norms assessed from mark–recaptures of wild fish in their natural habitat 下载免费PDF全文
Reaction norms are a valuable tool in evolutionary biology. Lately, the probabilistic maturation reaction norm approach, describing probabilities of maturing at combinations of age and body size, has been much applied for testing whether phenotypic changes in exploited populations of fish are mainly plastic or involving an evolutionary component. However, due to typical field data limitations, with imperfect knowledge about individual life histories, this demographic method still needs to be assessed. Using 13 years of direct mark–recapture observations on individual growth and maturation in an intensively sampled population of brown trout (Salmo trutta), we show that the probabilistic maturation reaction norm approach may perform well even if the assumption of equal survival of juvenile and maturing fish does not hold. Earlier studies have pointed out that growth effects may confound the interpretation of shifts in maturation reaction norms, because this method in its basic form deals with body size rather than growth. In our case, however, we found that juvenile body size, rather than annual growth, was more strongly associated with maturation. Viewed against earlier studies, our results also underscore the challenges of generalizing life‐history patterns among species and populations. 相似文献
150.
Serenella Sala Dimitar Marinov David Pennington 《The International Journal of Life Cycle Assessment》2011,16(8):748-760