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41.
This study uses social capital theory and social network analysis to explore how relations in an online academic communication network impact the overall structure of that network. Social network analysis is a particularly advantageous methodological tool for linking changes in microlevel choices to macrolevel structural alterations. Results indicate the online communication network’s structure exists independent of changes in communication ties. Specifically degree centrality, betweenness centrality, and clique formation indicated communication ties are initiated and discontinued over a 7-month timeframe. However, the dynamic nature of the microlevel communication choices does not mirror the quasi-stable structure of the online network. Results provide avenues for future research. 相似文献
42.
Delay- and Disruption-Tolerant Networking 总被引:3,自引:0,他引:3
Delay- and disruption-tolerant networking (DTN) grew out of attempts to develop an Interplanetary Internet but has evolved into an active area of networking research, with applications in space networking, military tactical networking, and networking for various challenged communities. The DTN Research Group provides an open forum in which DTN researchers and developers can collaborate to further develop this experimental technology. 相似文献
43.
N. P. Bansal D. Boyne D. E. Farrell 《Journal of Superconductivity and Novel Magnetism》1988,1(4):417-425
We have investigated the effect of three dopants directed at the oxygen sites in Y1Ba2Cu3O7?δ : sulfur, fluorine, and chlorine. Single-phase material has been obtained up to a (nominal) replacement of ~1% of the oxygen. Although the lattice parameters are unchanged, all dopants raiseT c (very slightly), sharpen the resistive transition, reduce the normal state resistivity, and very substantially increase the (magnetically determined) fraction of the material that is superconducting. All of these results differ qualitatively from those obtained with dopants directed at other locations in the 123 structure, and it is suggested that small additions of sulfur, fluorine, or chlorine may help to stabilize the ideal 123 stoichiometry. 相似文献
44.
We formulate a class of difference schemes for stiff initial-value problems, with a small parameter ε multiplying the first derivative. We derive necessary conditions for uniform convergence with respect to the small parameter ε, that is the solution of the difference scheme uih satisfies |uih−u(xi)| Ch, where C is independent of h and ε. We also derive sufficient conditions for uniform convergence and show that a subclass of schemes is also optimal in the sense that |uih−u(xi)| C min (h, ε). Finally, we show that this class contains higher-order schemes. 相似文献
45.
N Noviski JP Brewer WA Skornik SJ Galli JM Drazen TR Martin 《Canadian Metallurgical Quarterly》1999,86(1):202-210
Exposure to ambient ozone (O3) is associated with increased exacerbations of asthma. We sought to determine whether mast cell degranulation is induced by in vivo exposure to O3 in mice and whether mast cells play an essential role in the development of pulmonary pathophysiological alterations induced by O3. For this we exposed mast cell-deficient WBB6F1-kitW/kitW-v (kitW/kitW-v) mice and the congenic normal WBB6F1 (+/+) mice to air or to 1 or 3 parts/million O3 for 4 h and studied them at different intervals from 4 to 72 h later. We found evidence of O3-induced cutaneous, as well as bronchial, mast cell degranulation. Polymorphonuclear cell influx into the pulmonary parenchyma was observed after exposure to 1 part/milllion O3 only in mice that possessed mast cells. Airway hyperresponsiveness to intravenous methacholine measured in vivo under pentobarbital anesthesia was observed in both kitW/kitW-v and +/+ mice after exposure to O3. Thus, although mast cells are activated in vivo by O3 and participate in O3-induced polymorphonuclear cell infiltration into the pulmonary parenchyma, they do not participate detectably in the development of O3-induced airway hyperresponsiveness in mice. 相似文献
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48.
Rosemary Farrell 《电子与电脑》2008,(8)
据iSuppli公司报告,2008年第一季度多数厂商在季中降低或者缩窄了营业收入预期,与当时相比,第二财季的情况比较正面.在第二财季季中展望中,多数厂商重申了季度营业收入预期或者只是略微收紧了预估区间. 相似文献
49.
Surveyed 227 practicing psychologists to explore the impact of computers on the everyday practice of psychology and practitioners' attitudes toward specific uses of computers. Whereas more than half of the respondents reported using computers in their practices, most restricted their use to clerical applications. Few practitioners used their computer for more clinical applications. Reasons most frequently reported for not using computers related to lacking the necessary skills and experience and to financial considerations. Overall, practitioners had positive attitudes toward a variety of specific applications of computers. Implications of these findings for facilitating the appropriate use of computers by practitioners are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Yunqiang Ti Feng Qiu Yinghui Cao Linghua Jia Weiping Qin Jie Zheng Gerald Farrell 《Journal of Materials Science》2008,43(22):7073-7078
Copper–alkali ion exchange technology was used to prepare BK7 glass planar waveguides. The photoluminescence spectra of the
waveguides were studied with fluorescence spectrophotometer. It was observed that there were strong emission peaks at around
520 nm, which were strongly influenced by the ion-exchange times. Besides the time, the ion-exchange temperature was important
factor as well, the higher ion-exchange temperature was found to bring a blue shift of emission spectra. The blue–green emission
band originates from different transition mechanism of energy level. The spectroscopy features of copper within the glass
host were also affected by the excitation wavelength, which resulted in a shift of the emission band peaks. 相似文献