949 resultados para 949.6103


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This paper develops a sociomaterial perspective on digital coordination. It extends Pickering’s mangle of practice by using a trichordal approach to temporal emergence. We provide new understanding as to how the nonhuman and human agencies involved in coordination are embedded in the past, present, and future. We draw on an in-depth field study conducted between 2006 and 2010 of the development, introduction, and use of a computing grid infrastructure by the CERN particle physics community. Three coordination tensions are identified at different temporal dimensions, namelyobtaining adequate transparency in the present, modeling a future infrastructure, and the historical disciplining of social and material inertias. We propose and develop the concept of digital coordination, and contribute a trichordal temporal approach to understanding the development and use of digital infrastructure as being orientated to the past and future while emerging in the present.

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The present study was carried out to investigate contamination of heavy metals in 19 fish species from the Banan section of Chongqing in the Three Gorges, Yangtze River. The results showed that the mean concentrations of heavy metals were higher in intestine than muscle, except zinc in upper strata. In the fish inhabiting the upper strata, there were significant differences between mean concentrations of As, Cr, Cu and Hg in muscle and intestine (P <0.05). There were also significant differences between mean concentrations of Cr and Cu in muscle and intestine in the fish inhabiting middle strata. However, significant differences between mean concentrations of As, Cd, Hg, Pb and Zn were measured in fish inhabiting bottom strata in both intestine and muscle tissues (P <0.05). For the fish inhabiting different strata, the concentrations of As, Cd, Cr, Cu, Hg and Ph in muscle and intestine of the fish from bottom strata (BS) were higher than those in both upper strata (US) and middle strata (MS); whereas a higher concentration of Zn was measured in muscle and intestine from fish inhabiting upper strata. Mean metal concentrations were found to be higher in age 11 than those in age I in Coreius heterodon (2- and 1-year odl fish respectively). The overall results indicated that fish muscle in the Banan section were slightly contaminated by heavy metals, but did not exceed Chinese food standards.

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We report mode-locking of an optically pumped VECSEL using a graphene-based saturable absorber mirror (GSAM). Self-starting and stable modelocked operation is demonstrated with 473 fs pulses at 1.5 GHz repetition rate and 949 nm center wavelength. Wavelength tuning is achieved over a 46 nm bandwidth. We discuss the mirror design, the fabrication of the GSAMs, and give an outlook on further optimization of the design, including dielectric top coatings to protect the graphene and to increase the flexibility in the design. © 2014 SPIE.

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Water solubility enhancements of six phthalates (five aliphatic phthalates and one phenyl phthalate) by cetyltrimethylammonium bromide (CTAB) and beta-cyclodextrin (beta-CD) were studied at 25 degreesC. The solubilities of these plithalates are remarkably enhanced by CTAB solutions above the critical micelle concentration (cmc). Only marginal enhancement of phthalate solubility was observed in solutions containing CTAB below its cmc and beta-CD at low concentrations (less than 5 mM). The solubility enhancements of the plithalates are proportional to the added amount of CTAB and beta-CD. Partition coefficients of the plithalates between monomeric CTAB surfactant and water (K-MN) and between CTAB micelle and water K-MC) were estimated from the experimental data. The mechanisms of solubility enhancements by CTAB and beta-CD were discussed. A log-linear equation was proposed and evaluated for the solubilization by CTAB below cmc, while the previously proposed linear partitioning model was questioned. The structures of the complexes formed between plithalates and beta-CD were proposed, and the formation constants were estimated. The values of log K-MC, log K-MN, and log Kbeta-CD of the plithalates were found to correlate linearly with the log K-OW of plithalates, with the exception of the solid phenyl phthalate.

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We have studied the electronic structure of vertically assembled quantum discs in a magnetic field with varying orientation using the effective mass approximation. We calculate the four energy levels of single-electron quantum discs and the two lowest energy levels of two-electron quantum discs in a magnetic field with varying orientation. The change of the magnetic field as an effective potential strongly modifies the electronic structure, leading to splittings of the levels and anticrossings between the levels. The calculated results also demonstrate the switching between the ground states with the total spin S = 0 and 1. The switching induces a qubit controlled by varying the orientation of the magnetic field.

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医院信息系统(hospital information system,HIS)作为医院信息化建设的重要组成部分越来越受到社会的重视,已经进入一个高速发展的阶段。但是作为诊疗过程的一个重要组成部分-药物处方治疗,在HIS中却缺少必要的监控与指导。在HIS标准化推进的同时,更应该对其深度和广度进行研究,结合软件工程的设计思想,基于面向对象的开发方法,设计开发了“中药处方配伍”监控系统,提供了临床用药指导功能,使其作为HIS的一个子系统能够实时的对医生处方进行监控,使临床医药人员记得更多、更准、更细,以降低药源性疾病,提高用药质量,加强用药管理,避免医疗纠纷。

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Petri网标识的可达性判定问题是进行Petri网分析的基础,而传统的判定方法并不能确保所得结果的可靠性.在揭示Petri网可达性问题的实质之后,讨论了在标识图的同一连通域内标识可达性的判定问题,进而在分析相关原理的基础上提出了一种有效判定Petri网标识可达性的综合判定法.此判定方法综合多种传统判定方法的优点,结合Gr鯾ner基理论,确保了对Petri网标识可达性进行判定所得结果的可靠性.

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本文通过建立座标分裂的概念,成功地解决了二维非定常流中交界面的问题,该方法同时具有简单、精度高和计算速度快等优点。本文给出了气波增压器转子内部流场的计算结果、并和现有的其它计算结果作了比较。

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青藏高原是世界上最大、最年轻的高原。大气氧分压低、太阳辐射强烈和 气候寒冷等自然特点使得生活在青藏高原上的动物在形态、生态、行为以及生 理机能上都受到深刻的影响,并在进化过程中对高原环境产生了特殊的适应性。 生活在高原上的动物分为世居动物和移居动物,它们处于高原适应过程中的不 同阶段,并且有着不同的高原适应性的特点。为了研究高原哺乳动物所拥有的 特殊高原适应性的遗传基础和进化历史,以及探讨处于不同高原适应阶段的哺 乳动物对高原的适应性在遗传基础上的异同,本研究首次测定和分析了高原世 居动物中的藏羚羊(Pantholops hodgsonii)和高原鼠兔(Ochotona curzoniae) 以及高原移居动物中的藏马(Equns caballus)这三种具有代表性的高原动物的 线粒体全基因组。 1. 藏羚羊线粒体DNA 中的变异及其进化史 在对线粒体上13 个基因进行了进化分析后,我们发现细胞色素氧化酶1 (COX1)基因在藏羚羊和牦牛中都有高的非同义突变的现象。COX1 基因编码 的蛋白是线粒体氧化呼吸链上复合物Ⅳ的一部分,它将电子传递给氧,进行有 氧呼吸并产生能量。考虑到藏羚羊与牦牛都是生活在相同的气候环境中,我们 猜想线粒体基因组编码的COX1 基因的进化可能对青藏高原世居动物适应高原 环境起到作用。藏羚羊的线粒体DNA 数据表明,藏羚羊与绵羊、山羊的亲缘 关系较近,而与羚羊属家族的动物则相对较远,同时我们估算了藏羚羊与绵羊 山羊的分化时间大约为220 万年左右。这一时间与一些学者所估计的青藏高原 隆起时间大致吻合。 2. 高原鼠兔线粒体DNA 中的变异及其进化史 对高原鼠兔线粒体基因组上的基因进行进化分析后发现,对于高原鼠兔这一 分枝上,COX1 基因也有高的非同义突变速率。这表明COX1 基因在高原鼠兔 适应青藏高原高寒缺氧的环境过程中也可能受到选择压力的作用,结合我们在 藏羚羊和牦牛中的分析结果,我们推测高原世居动物在COX1 基因的进化过程 中很多都表现出类似的受选择现象。3. 藏马线粒体DNA 中的变异及其进化史 我们测定了西藏那曲(4500m)、云南中甸(3300m)、云南德钦(3300m)地区共 三匹藏马线粒体全基因组序列。通过对线粒体蛋白编码区的分析发现,与藏羚 羊、高原鼠兔等高原世居动物表现出的COX1 基因受选择不同,在三匹藏马中 NADH6 基因均表现高的非同义突变现象。NDAH6 基因编码的蛋白是线粒体氧 化呼吸链上复合物Ⅰ的一部分,它催化电子从NADH 传递给辅酶Q。不同地区 藏马中NADH6 基因类似的进化方式表明NADH6 基因的进化可能与藏马对高 原极端环境的适应有关。藏马在线粒体基因进化上所表现出的与其它高原世居 动物的不同究竟是由于动物在适应高原的不同阶段其遗传基础和策略的不同所 造成的,还是由于物种间的差异所造成的我们尚不能确定。还需要进一步对高 原动物线粒体基因进行研究。此外,我们对藏马进化史的研究表明藏马可能为 多地区起源

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在讨论半导体激光线宽压窄理论的基础上,利用闪耀光栅作为外部反馈元件,介绍了由中心波长为949.6nm、原始线宽为1.2THz的单管半导体激光器构成的反馈外腔,它能够很好的改善半导体激光器的性能.实验得到了中心波长稳定的、单纵模的高质量激光输出,边模抑制比大于30dB,线宽优于1.2MHz (Δλ<3.6×10~(-6)nm).实验证实了强反馈能够很好地改善外腔半导体激光器的动态特性.

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于2010-11-23批量导入

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