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131.
Recently developed concepts and techniques of analyzing complex systems provide new insight into the structure of social networks. Uncovering recurrent preferences and organizational principles in such networks is a key issue to characterize them. We investigate school friendship networks from the Add Health database. Applying threshold analysis, we find that the friendship networks do not form a single connected component through mutual strong nominations within a school, while under weaker conditions such interconnectedness is present. We extract the networks of overlapping communities at the schools (c-networks) and find that they are scale free and disassortative in contrast to the direct friendship networks, which have an exponential degree distribution and are assortative. Based on the network analysis we study the ethnic preferences in friendship selection. The clique percolation method we use reveals that when in minority, the students tend to build more densely interconnected groups of friends. We also find an asymmetry in the behavior of black minorities in a white majority as compared to that of white minorities in a black majority. 相似文献
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L. de Arcangelis H. J. Herrmann M. Kolb René Thomas C. Amitrano L. Peliti M. Saber G. Weisbuch Sara A. Solla F. Bagnoli A. Francescato R. Livi S. Ruffo Pablo Tamayo Michel Droz Peter Jörg Plath S. Romano Yves Pomeau Stéphane Zaleski D. Stauffer Luciano R. da Silva Alex Hansen Stéphane Roux Antonio Coniglio B. Derrida Henrik Flyvbjerg Naeem Jan Dietrich Stauffer Peter Grassberger A. Zippelius K. E. Kurten Werner Krauth Jean -Pierre Nadal Marc Mézard Per Bak Chao Tang Itzhak Webman M. L. Martins H. F. V. Resende C. Tsallis A. C. N. Magalhaes 《Journal of statistical physics》1989,55(5-6):1333-1359
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P. Schläpfer Herrmann G. Lunge und H. Köhler 《Fresenius' Journal of Analytical Chemistry》1934,97(7-8):298-301
Ohne Zusammenfassung 相似文献
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U. Hochkirch W. Herrmann R. Stößer K.-P. Moll J. Gallego Llerena M. Linscheid H.-H. Borchert 《Applied magnetic resonance》2008,35(1):173-184
The spectral–spatial electron spin resonance (ESR) imaging experiment provides information about the spatial and spectral
properties of the examined sample, as well as the intensity distribution. Obtaining quantitative statements of the respective
sample requires the usage of reference standards such as diphenylpicrylhydrazyl (DPPH) or charcoal. By means of ultraviolet-visible
spectroscopy a DPPH sample has been quantified to become the reference DPPH standard for the following experiments. Moreover,
charcoal together with DPPH serves as a standard to determine the spatial dimension. An ESR tomographic device has been modified
concerning the sample shaping and arranging in a TE102 resonator to allow the spatially resolved quantitative determination of spin concentrations of spin probes (S = 1/2) with an acceptable error. Only standard ESR equipment has been used except the additional gradient coils and their
computer-aided controls for recording the tomogram. The presented results, i.e., the spatially resolved determination of spin
concentrations, seem to be useful to describe, e.g., transport processes in biological objects. As a first application of
the developed method, the spatial resolution of the effect of ultraviolet irradiation on the concentration of a spin probe
in human skin could be determined. Altogether, the newly introduced method widens the field of applications of ESR spectroscopy
and tomography.
Authors' address: Werner Herrmann, Institute of Pharmacy, Free University Berlin, Kelchstrasse 31, 12169 Berlin, Germany 相似文献
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