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  • 2015  (14)
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  • 2015  (14)
  • 1
    In: Journal of Next Generation Sequencing & Applications, 2015, Vol.02(02)
    ISSN: Journal of Next Generation Sequencing & Applications
    E-ISSN: 24699853
    Source: CrossRef
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  • 2
    In: PLoS ONE, 2015, Vol.10(3)
    Description: Arsenic (As) mobilization in alluvial aquifers is caused by a complex interplay of hydro-geo-microbiological activities. Nevertheless, diversity and biogeochemical significance of indigenous bacteria in Bengal Delta Plain are not well documented. We have deciphered bacterial community compositions and metabolic properties in As contaminated groundwater of West Bengal to define their role in As mobilization. Groundwater samples showed characteristic high As, low organic carbon and reducing property. Culture-independent and -dependent analyses revealed presence of diverse, yet near consistent community composition mostly represented by genera Pseudomonas , Flavobacterium , Brevundimonas , Polaromonas , Rhodococcus , Methyloversatilis and Methylotenera . Along with As-resistance and -reductase activities, abilities to metabolize a wide range carbon substrates including long chain and polyaromatic hydrocarbons and HCO 3 , As 3+ as electron donor and As 5+ /Fe 3+ as terminal electron acceptor during anaerobic growth were frequently observed within the cultivable bacteria. Genes encoding cytosolic As 5+ reductase ( ars C) and As 3+ efflux/transporter [ ars B and acr 3(2)] were found to be more abundant than the dissimilatory As 5+ reductase gene arr A. The observed metabolic characteristics showed a good agreement with the same derived from phylogenetic lineages of constituent populations. Selected bacterial strains incubated anaerobically over 300 days using natural orange sand of Pleistocene aquifer showed release of soluble As mostly as As 3+ along with several other elements (Al, Fe, Mn, K, etc .). Together with the production of oxalic acid within the biotic microcosms, change in sediment composition and mineralogy indicated dissolution of orange sand coupled with As/Fe reduction. Presence of ars C gene, As 5+ reductase activity and oxalic acid production by the bacteria were found to be closely related to their ability to mobilize sediment bound As. Overall observations suggest that indigenous bacteria in oligotrophic groundwater possess adequate catabolic ability to mobilize As by a cascade of reactions, mostly linked to bacterial necessity for essential nutrients and detoxification.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 3
    In: The ISME Journal, 2015
    Description: Vector-borne microbes are subject to the ecological constraints of two distinct microenvironments: that in the arthropod vector and that in the blood of its vertebrate host. Because the structure of bacterial communities in these two microenvironments may substantially affect the abundance of vector-borne microbes, it is important to understand the relationship between bacterial communities in both microenvironments and the determinants that shape them. We used pyrosequencing analyses to compare the structure of bacterial communities in Synosternus cleopatrae fleas and in the blood of their Gerbillus andersoni hosts. We also monitored the interindividual and seasonal variability in these bacterial communities by sampling the same individual wild rodents during the spring and again during the summer. We show that the bacterial communities in each sample type (blood, female flea or male flea) had a similar phylotype composition among host individuals, but exhibited seasonal variability that was not directly associated with host characteristics. The structure of bacterial communities in male fleas and in the blood of their rodent hosts was remarkably similar and was dominated by flea-borne Bartonella and Mycoplasma phylotypes. A lower abundance of flea-borne bacteria and the presence of Wolbachia phylotypes distinguished bacterial communities in female fleas from those in male fleas and in rodent blood. These results suggest that the overall abundance of a certain vector-borne microbe is more likely to be determined by the abundance of endosymbiotic bacteria in the vector, abundance of other vector-borne microbes co-occurring in the vector and in the host blood and by seasonal changes, than by host characteristics.
    Keywords: Biology;
    ISSN: 1751-7362
    E-ISSN: 17517370
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  • 4
    Language: English
    In: Chinese Science Bulletin (Chinese Version), 2015, Vol.60(23), p.2188
    ISSN: 0023-074X
    Source: CrossRef
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  • 5
    Language: English
    In: Genome announcements, 20 August 2015, Vol.3(4)
    Description: We report here the draft genome sequence of a Bacillus bacterium isolated from the microflora of Nostoc colonies grown at the Andean wetlands in northern Chile. We consider this genome sequence to be a molecular tool for exploring microbial relationships and adaptation strategies to the prevailing extreme conditions at the Atacama Desert.
    Keywords: Prokaryotes;
    ISSN: 2169-8287
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  • 6
    Language: English
    In: mBio, 15 September 2015, Vol.6(5), pp.e01315-15
    Description: The influence of the skin microbiota on host susceptibility to infectious agents is largely unexplored. The skin harbors diverse bacterial species that may promote or antagonize the growth of an invading pathogen. We developed a human infection model for Haemophilus ducreyi in which human volunteers are inoculated on the upper arm. After inoculation, papules form and either spontaneously resolve or progress to pustules. To examine the role of the skin microbiota in the outcome of H. ducreyi infection, we analyzed the microbiomes of four dose-matched pairs of "resolvers" and "pustule formers" whose inoculation sites were swabbed at multiple time points. Bacteria present on the skin were identified by amplification and pyrosequencing of 16S rRNA genes. Nonmetric multidimensional scaling (NMDS) using Bray-Curtis dissimilarity between the preinfection microbiomes of infected sites showed that sites from the same volunteer clustered together and that pustule formers segregated from resolvers (P = 0.001, permutational multivariate analysis of variance [PERMANOVA]), suggesting that the preinfection microbiomes were associated with outcome. NMDS using Bray-Curtis dissimilarity of the endpoint samples showed that the pustule sites clustered together and were significantly different than the resolved sites (P = 0.001, PERMANOVA), suggesting that the microbiomes at the endpoint differed between the two groups. In addition to H. ducreyi, pustule-forming sites had a greater abundance of Proteobacteria, Bacteroidetes, Micrococcus, Corynebacterium, Paracoccus, and Staphylococcus species, whereas resolved sites had higher levels of Actinobacteria and Propionibacterium species. These results suggest that at baseline, resolvers and pustule formers have distinct skin bacterial communities which change in response to infection and the resultant immune response. Human skin is home to a diverse community of microorganisms, collectively known as the skin microbiome. Some resident bacteria are thought to protect the skin from infection by outcompeting pathogens for resources or by priming the immune system's response to invaders. However, the influence of the skin microbiome on the susceptibility to or protection from infection has not been prospectively evaluated in humans. We characterized the skin microbiome before, during, and after experimental inoculation of the arm with Haemophilus ducreyi in matched volunteers who subsequently resolved the infection or formed abscesses. Our results suggest that the preinfection microbiomes of pustule formers and resolvers have distinct community structures which change in response to the progression of H. ducreyi infection to abscess formation.
    Keywords: Microbiota ; Haemophilus Ducreyi -- Growth & Development ; Skin -- Microbiology ; Skin Diseases, Bacterial -- Microbiology
    E-ISSN: 2150-7511
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  • 7
    In: Genome Announcements, DC: American Society for Microbiology
    Description: This article reports the draft genome sequence of a Bacillus bacterium isolated from the microflora of Nostoc colonies grown at the Andean wetlands in northern Chile.
    Keywords: Genome ; Bacillus Bacterium ; Nostoc Colonies
    Source: University of North Texas
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  • 8
    Language: English
    In: 2015 IEEE Conference on Computer Communications (INFOCOM), April 2015, pp.1903-1911
    Description: Optical data center networks (DCNs) are becoming increasingly attractive due to their technological strengths compared to traditional electrical networks. However, prior optical DCNs are either hard to scale, vulnerable to single point of failure, or provide limited network bisection bandwidth for many practical DCN workloads. To this end, we present WaveCube, a scalable, fault-tolerant, high-performance optical DCN architecture. To scale, WaveCube removes MEMS〈sup〉1〈/sup〉, a potential bottleneck, from its design. Wave-Cube is fault-tolerant since it does not have single point of failure and there are multiple node-disjoint parallel paths between any pair of Top-of-Rack (ToR) switches. WaveCube delivers high performance by exploiting multi-pathing and dynamic link bandwidth along the path. Our extensive evaluation results show that WaveCube outperforms previous optical DCNs by up to 400% and delivers network bisection bandwidth that is 70%-85% of an ideal non-blocking network under both realistic and synthetic traffic patterns. WaveCube's performance degrades gracefully under failures - it drops 20% even with 20% links cut. WaveCube also holds promise in practice - its wiring complexity is orders of magnitude lower than Fattree, BCube and c-Through at large scale, and its power consumption is 35% of them.
    Keywords: Bandwidth ; Optical Switches ; Micromechanical Devices ; Ports (Computers) ; Topology ; Optical Fiber Networks ; Fault Tolerance ; Engineering
    ISSN: 0743-166X
    E-ISSN: 2641-9874
    Source: IEEE Conference Publications
    Source: IEEE Xplore
    Source: IEEE Journals & Magazines 
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  • 9
    In: 科学通报 - Chinese Science Bulletin, 2015, Issue 23, pp.2188-2195
    Description: 基于激光脉冲粗糙面散射特征,利用积分变换,误差函数和随机变量的统计矩,研究激光脉冲非相干散射和散射场量的强度起伏协方差函数特征.在入射激光波长?=1.06?m条件下,数值计算了不同粗糙面高度起伏均方和相关长度,不同入射角等影响因素下,散射场相干和非相干分量,以及强度起伏协方差函数随散射角和相干带宽频差的变化情况.计算结果表明,在激光脉冲入射下,随机粗糙面的高度均方越小,相关长度越大,即表面越光滑,散射场的相干和非相干分量在入射角镜反射方向出现最大峰值,非相干分量峰值在非入射角镜反射方向上会迅速减小,且非相干分量在量级比相干散射分量上小很多,散射场强度起伏协方差函数的分布趋势随着相干带宽频差的增大逐步减小,镜反射方向和相干带宽频差为零时出现最大峰值.本文所给出的研究结果,深化了粗糙面脉冲散射场量的四阶统计特征,为开展目标激光脉冲散射场量高阶统计特征和激光散斑探测研究奠定基础.
    Description: According to the field characteristics of laser pulse scattering from a random rough surface, laser pulse incoherence scattering characteristics and a covariance function of the scattered intensity fluctuation are investigated numerically using the integral transform, an error function and the statistical moments of random variables. For an incident laser pulse, numerical methods are used to calculate the coherent and incoherent scattering characteristics and the covariance function of the fluctuation in scattering intensity with the coherence bandwidth frequency and scattering angle, considering multiple factors such as the mean of fluctuating heights, the coherence length of a random rough surface, and the incidence angle. Results show that for the incident laser pulse, a smaller mean of the fluctuating height and a longer correlation length correspond to a smoother surface and larger maximum peak values of coherent and incoherent scattering components in the specular direction. The incoherent scattering peak value decreases more rapidly in the non-specular direction, and incoherent scattering components are an order of magnitude smaller than coherent scattering components. The distribution of the covariance function of the scattering field intensity fluctuation gradually reduces with an increase in the coherence bandwidth frequency difference, having a maximum peak value in the specular direction as the coherence bandwidth difference tends to zero. This paper presents innovative results that emphasize the incoherent scattering characteristics and the covariance function of the scattered intensity fluctuation for the further study of the fourth-order moment statistical characteristic of laser pulse scattering from a rough surface. Future works investigate other high-order statistical moments of laser pulse scattering from a rough surface and laser speckle in laser detection applications.
    Keywords: 粗糙面散射 ; 脉冲散射 ; 四阶矩统计特征 ; 非相干散射特征 ; 强度起伏 ; 协方差函数 ; Scattering From Rough Surface, Laser Pulse Scattering, the Fourth Order Moment Statistical Characteristics, the Incoherencescattering Characteristics, the Scattered Intensity Fluctuation, Covariance Function
    ISSN: 0023-074X
    Source: 维普数据 (Chongqing VIP Information Co.)
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  • 10
    In: 真空科学与技术学报 - JOurnal of Vacuum Science and Technology, 2015, Issue 08, pp.955-962
    Description: 采用非平衡磁控溅射技术在Si3N4球及高速钢基体上制备了类金刚石(DLC)膜。采用UMT-II型球盘式摩擦磨损试验机分别考察了Si3N4球、镀DLC膜Si3N4球及GCr15球的摩擦学性能,并分析了不同滑动速度和载荷下Si3N4球表面DLC膜的摩擦学性能。研究结果表明:Si3N4球的摩擦系数及磨损率约为GCr15球的一半,但因Si3N4球脆性较大,在摩擦过程中摩擦接触表面容易剥落;Si3N4球表面镀DLC膜能有效地改善Si3N4球脆性大的弱点,并具有良好的减摩作用;Si3N4球表面DLC膜所组成摩擦副的平均摩擦系数随着载荷的增加而增大;随着速度的增加摩擦副的摩擦系数先增大而后减小,滑动速度对摩擦副摩擦系数的影响比载荷明显。实验结果表明Si3N4球表面镀DLC膜适合于高速轻载的工况。
    Description: We addressed the tribological properties of thediamond-like carbon( DLC) coatings,deposited on substrates of Si3N4 balls and high-speed steel by unbalanced magnetron sputtering. The impact of the sliding-velocity and load in dry friction tests on the friction coefficient,wear-rate,and morphology of wear-tracks,was investigated with ball-on-disc tribo-meter. The results show that depending on the sliding velocity and load,the DLC coatings significantly reduced the friction-coefficient,wear-rate and brittleness of the Si3N4 balls. To be specific,peeling-off of the DLC coatings easily occurred due to the weak interfacial adhesion. The friction coefficient and wear-rate of the DLC coated Si3N4 balls is 50% lower than those of the GCr15 balls. The friction-coefficient and wear-rate increased with an increase of the load; and as the sliding velocity increased,the average friction-coefficient changed in a decrease-increase mode,accompanied by an increase of the wear-rate possibly because of increasing graphitization of DLC coatings. We suggest that the DLC coated Si3N4 balls may work best under high speed and light load conditions.
    Keywords: 氮化硅球 ; 类金刚石膜 ; 摩擦学性能 ; 工况参数 ; Silicon Nitride Balls; Diamond-Like Carbon Films; Tribological Properties; Friction Conditions
    ISSN: 1672-7126
    Source: 维普数据 (Chongqing VIP Information Co.)
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