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1.
Identifying sets of key players in a social network 总被引:3,自引:0,他引:3
A procedure is described for finding sets of key players in a social network. A key assumption is that the optimal selection
of key players depends on what they are needed for. Accordingly, two generic goals are articulated, called KPP-POS and KPP-NEG.
KPP-POS is defined as the identification of key players for the purpose of optimally diffusing something through the network
by using the key players as seeds. KPP-NEG is defined as the identification of key players for the purpose of disrupting or
fragmenting the network by removing the key nodes. It is found that off-the-shelf centrality measures are not optimal for
solving either generic problem, and therefore new measures are presented.
Stephen P. Borgatti is Professor of Organization Studies at the Carroll School of Management, Boston College. His research is focused on social
networks, social cognition and knowledge management. He is also interested in the application of social network analysis to
the solution of managerial problems. 相似文献
2.
M. Pedio N. Mahne F. Borgatti S.K.M. Henze F.S. Tautz R. Hudej B. Nickel 《Applied Surface Science》2007,254(1):103-107
Thin films of pentacene (C22H14) have become widely used in the field of organic electronics. Here films of C22H14 of thickness ranging from submonolayer to multilayer were thermally deposited on Ag(1 1 1) surface. The determination of molecular geometry in pentacene films on Ag(1 1 1) studied by X-ray absorption at different stages of growth up to one monolayer is presented.XAS spectra at the C K-edge were collected as a function of the direction of the electric field at the surface. The different features of the spectra were assigned to resonances related to the various molecular unoccupied states by the comparison with the absorption coefficient of the pentacene gas phase. The transitions involving antibonding π states show a pronounced angular dependence for all the measured coverages, from submonolayer to multilayer. The spectra analysis indicates a nearly planar chemisorption of the first pentacene layer with a tilt angle of 10°. 相似文献
3.
We present a spectroscopic study of the structure of two peptides deposited on Au and TiO2:
- - PeptA, (EAK16-RGD) bringing the adhesive RGD sequence linked to EAK16;
- - PeptB, having RGD linked to a “scrambled” sequence of the EAK16 peptide.
4.
Monica Borgatti Irene Mancini Nicoletta Bianchi Alessandra Guerrini Ilaria Lampronti Damiano Rossi Gianni Sacchetti Roberto Gambari 《BMC biochemistry》2011,12(1):15
Background
Cystic fibrosis (CF) airway pathology is a fatal, autosomal, recessive genetic disease characterized by extensive lung inflammation. After induction by TNF-α, elevated concentrations of several pro-inflammatory cytokines (i.e. IL-6, IL-1β) and chemokines (i.e. IL-8) are released from airway epithelial cells. In order to reduce the excessive inflammatory response in the airways of CF patients, new therapies have been developed and in this respect, medicinal plant extracts have been studied. In this article we have investigated the possible use of bergamot extracts (Citrus bergamia Risso) and their identified components to alter the expression of IL-8 associated with the cystic fibrosis airway pathology. 相似文献5.
Martin G. Everett John P. Boyd Stephen P. Borgatti 《The Journal of mathematical sociology》2013,37(3-4):163-172
Structural equivalence (Lorrain and White, 1971) and automorphic equivalence (Everett, 1985) are generalized to define neighborhood‐ and ego‐centered equivalences. It is shown that local versions of these equivalences can then be formulated quite naturally. In addition to these natural localizations, a generalized procedure capable of localizing any model of role equivalence is presented. From a theoretical point of view, local roles are recommended by the notion that network influences on ego diminish with distance. From a practical point of view, local roles help find structure in graphs where global equivalences find no two actors equivalent. 相似文献
6.
Stefan Kowarik Alexander Gerlach Alexander Hinderhofer Silvia Milita Francesco Borgatti Federico Zontone Toshiyasu Suzuki Fabio Biscarini Frank Schreiber 《固体物理学:研究快报》2008,2(3):120-122
We report high structural order in thin films of the organic semiconductor perfluoro‐pentacene (PFP), which is a candidate material for n‐type applications, deposited by vacuum sublimation on oxidized silicon wafers. Bragg reflections up to high order in both specular and grazing incidence geometries and a mosaicity of less than 0.01° demonstrate the well defined structure. The thin film entirely consists of crystallites with a structure close to the bulk phase without any contamination with a second phase. Real‐time X‐ray measurements show that PFP grows in a Stranski–Krastanov growth mode with the first monolayer wetting the substrate before 3d‐growth sets in during growth of the second monolayer. Implications for its use are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
We report the results of a Surface X-Ray Diffraction (SXRD) study of Fe nanostructured films deposited on c(2 × 2)-N/Cu(100) at room temperature (RT), with Fe coverage ΘFe = 0.5 ML and ΘFe = 1 ML. The c(2 × 2)-N/Cu(100) surface is an example of self-organised system, that can be used for growth of arrays of metal nano-islands and organic molecules assemblies. We chose two different values of N coverage, ΘN = 0.3 ML and ΘN = 0.5 ML, the second value corresponding to N saturation. We monitored the presence of surface diffraction peaks in hk scans and we performed Crystal Truncation Rods (CTR) analysis with ROD fitting programme. In the case of ΘN = 0.5 ML, i.e. at saturation coverage, the CTR could be fitted with one surface domain with p4gm(2 × 2) symmetry. In the surface cell adopted, N atoms occupy four-fold hollow sites, with Fe (intermixed with Cu) giving rise to a “clock” reconstruction previously observed on iron nitride films obtained by co-deposition and annealing. This result is an indirect confirmation of N surface segregation on top of the Fe films, occurring during the growth at RT. When subsaturation N coverage (ΘN = 0.3 ML) is used as a substrate for Fe deposition, the best results could be obtained with a model where two surface domains are present: the first one corresponds to a surface cell with Fe sitting in four-fold hollow sites on bare Cu areas, with possible interdiffusion in the second lattice. The second domain is assigned to growth of Fe on the N-covered square islands occurring once the bare Cu areas are fully covered. The SXRD analysis on N-covered surface domains shows that the mechanism of reconstruction and of N segregation on top layer is already active at RT for all N-coverage values. 相似文献
8.
Viola G Vedaldi D Dall'Acqua F Lampronti I Bianchi N Zuccato C Borgatti M Gambari R 《Journal of photochemistry and photobiology. B, Biology》2008,92(1):24-28
Psoralens, also known as furocoumarins, are a well-known class of photosensitizers largely used in the therapy of various skin disease. In this study we have evaluated the effects of crude pre-irradiated solutions of furocoumarins derivatives on (a) erythroid differentiation and apoptosis of human leukemic K562 cells and (b) hemoglobin synthesis in cultures of human erythroid progenitors derived from the peripheral blood. To prove the activity of a mixture of photoproducts generated by UVA irradiation of the three psoralen derivatives 5-methoxypsoralen (5-MOP) 8-methoxypsoralen (8-MOP), and angelicin (ANG), we employed the human leukemic K562 cell line and the two-phase liquid culture procedure for growing erythroid progenitors. The results obtained demonstrate that pre-irradiated solutions of psoralen derivatives significantly induce erythroid differentiation of K562 cells irrespective of the type of derivative used, suggesting that the active photoproduct(s) share a common structure. Interestingly, solutions of psoralens irradiated in anaerobic conditions do not exhibits erythroid inducing ability, indicating that the effect is mostly due to photooxidized psoralen products. In erythroid precursor cells, psoralens photolysis products stimulates at low concentrations an increase of hemoglobin A and hemoglobin F. Altogether, these data suggest that photoproducts of psoralen warrant further evaluation as potential therapeutic drugs in beta-thalassaemia and sickle cell anaemia. 相似文献
9.
L. Braicovich F. Borgatti A. Tagliaferri G. Ghiringhelli N.B. Brookes P. Ferriani C.M. Bertoni 《Applied Physics A: Materials Science & Processing》2001,73(6):679-686
We discuss the application of resonant inelastic X-ray scattering to the study of magnetic systems in the soft X-ray range.
To this end we distinguish two broad areas. In the first the layout of the experiment is such that the absorption magnetic
circular dichroism (MCD) is not zero. In the second the magnetisation is perpendicular to the incident helical beam so that
the absorption MCD is zero. In the first area we summarise published results on Fe-Co alloys and we present new data on Mn
impurities in Ni together with calculations. In the second area we summarise published results on Ni in Ni-ferrite with final
3s shell excitation and we present new results on Co-metal and Co in Co-ferrite measured with a new approach. This is based
on the incident energy dependence of the integral of the Raman spectrum in inner shell excitation (integrated resonant Raman
scattering). The potentialities and the limitations of the above methods are critically presented.
Received: 23 May 2001 / Accepted: 4 July 2001 / Published online: 5 October 2001 相似文献