Essential functional role of the polysaccharide intercellular adhesin of Staphylococcus epidermidis in hemagglutination

Hemagglutination of erythrocytes is a common property of Staphylococcus epidermidis strains, which is related to adherence and biofilm formation and may be essential for the pathogenesis of biomaterial-associated infections caused by S. epidermidis. In three independent biofilm-producing, hemagglutination-positive S. epidermidis isolates, interruption of the icaADBC operon essential for polysaccharide intercellular adhesin (PIA) synthesis by Tn917 insertions led to a hemagglutination-negative phenotype. An immunoglobulin G fraction of antiserum to PIA greatly reduced hemagglutination. Purified PIA led to a 64-fold decrease of hemagglutination titers of these strains; however, it did not mediate hemagglutination by itself. These observations define PIA as the hemagglutinin of S. epidermidis or at least as its major functional component.     

贵州窄巷口水电站水库渗漏处理中瞬变电磁仪物探勘测研究

贵州猫跳河四级窄巷口水电站水库,岩溶严重渗漏,达30多年.虽然经过多次和多洞口的封堵处理,效果不佳,其渗漏流量仍有15 m3/s左右.针对此情况,提出了分阶段实施封堵的方案.一期工程针对窄巷口河段的3个主要岩溶漏斗,进行局部永久性封堵.为此,进行了补充勘测:采用瞬变电磁仪,在窄巷口库段,以及进水塔前溶洞附近进行了物探勘测,并取得了成果.     

Sperm storage in females of the smooth newt (Triturus v. vulgaris L.): I. Ultrastructure of the spermathecae during the breeding season

Sperm storage in cloacal spermathecae was studied in females of Triturus v. vulgaris collected early in the breeding season in southern England. Females collected in terrestrial situations, presumably unmated, were mated in the laboratory, and the ultrastructure of the transferred sperm and the spermathecae was observed at various intervals after mating. Sperm from a spermatophore cap lodged in a female's cloacal orifice can migrate into spermathecae within 1 hr after mating. Spherical structures on the axial fibers of some sperm in the cap could indicate immaturity. Disorderly clusters of sperm from the cap are still present in the cloacal chamber 12 hr after mating but are absent 24 hr after mating. During storage, sperm often are in tangled masses in the spermathecal tubules. The sperm are coated with spermathecal secretions, and some sperm nuclei were observed embedded in the spermathecal epithelium. Little evidence for spermiophagy early in the breeding season was found. During oviposition, mazes of sperm occur external to the spermathecal orifices, and sperm may be released in this condition onto eggs as they pass through the cloaca. The tangled clusters in which sperm are found from pick-up to oviposition are hypothesized as an adaptation to reduce the effectiveness of sperm competition from the ejaculates of rival males. Additional studies, using the same protocol and covering the entire cycle of sperm storage, are necessary to enable interspecific comparisons leading to phylogenetic hypotheses.     

C-Map: A High-level Language for Engineering Analysis and Design

C-MAP is a high level language for engineering computations. In addition to the conventional programming features, C-MAP has over 100 functions covering a broad spectrum of numerical methods for engineering computations ranging from elementary calculus to non-linear constrained optimization problems. These basic functions can be nested in innumerable ways that give C-MAP great flexibility and power. C-MAP comprises four integrated components: (i) a fullscreen text editor with multiple stacked windows for simultaneous editing of programs and output files; (ii) a simplified C-like programming language with control structures, recursive functions, math library, and built-in functions for advanced engineering computations including the processing of general matrix and complex expressions; (iii) an interactive expression processor; and (iv) a simple authoring system with automatic cross-referencing of keywords. The program's versatility helps to meet the different needs of users at different stages of learning. A beginner may use only the built-in functions for math and matrix operations to get immediate, useful results; the advanced users may write their own functions for more complex problems. This paper discusses the features of C-MAP and its applications in teaching structural engineering     

关于环保建筑材料的使用和可持续发展的探讨

随着环保型消费逐步占据主流,住宅建筑的生产商和消费者都对建材提出了安全、健康、环保的要求。采用清洁卫生技术生产,减少对天然资源和能源的使用,大量使用无公害、无污染、无放射性环保型建筑材料,有利于环境保护和人体健康,是住宅建筑发展的必然趋势。     

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