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521.
Renaud Lambiotte Vincent D. Blondel Etienne Huens Zbigniew Smoreda 《Physica A》2008,387(21):5317-5325
In this paper, we analyze statistical properties of a communication network constructed from the records of a mobile phone company. The network consists of 2.5 million customers that have placed 810 million communications (phone calls and text messages) over a period of 6 months and for whom we have geographical home localization information. It is shown that the degree distribution in this network has a power-law degree distribution k−5 and that the probability that two customers are connected by a link follows a gravity model, i.e. decreases as d−2, where d is the distance between the customers. We also consider the geographical extension of communication triangles and we show that communication triangles are not only composed of geographically adjacent nodes but that they may extend over large distances. This last property is not captured by the existing models of geographical networks and in a last section we propose a new model that reproduces the observed property. Our model, which is based on the migration and on the local adaptation of agents, is then studied analytically and the resulting predictions are confirmed by computer simulations. 相似文献
522.
Moonen NN Pomerantz WC Gist R Boudon C Gisselbrecht JP Kawai T Kishioka A Gross M Irie M Diederich F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(11):3325-3341
An extensive series of silyl-protected cyanoethynylethenes (CEEs) and N,N-dimethylanilino donor-substituted CEEs have been synthesized. More extended chromophores were constructed by selective silyl deprotection and subsequent oxidative acetylenic coupling. The strong electron-accepting nature of the CEEs was revealed by a combination of 13C NMR spectroscopic and electrochemistry measurements. Donor-substituted CEEs display strong intramolecular charge-transfer (CT) character, resulting in intense, bathochromically shifted CT bands in the UV/Vis spectrum. Their structural diversity establishes them as suitable models for the study of pi-conjugation and band gap tuning in strong charge-transfer chromophores. The extent of pi-conjugation in the donor-substituted CEEs was investigated by a combination of ground-state techniques, such as X-ray crystallography, electrochemistry, B3 LYP calculations, and NMR spectroscopy. The comparison of these ground-state results with the features observed in the UV/Vis spectra reveals that-contrary to expectations-more extensive pi-conjugation can lead to larger band gaps in molecules with strong donor and acceptor moieties. 相似文献
523.
Noël R Vanucci-Bacqué C Fargeau-Bellassoued MC Lhommet G 《The Journal of organic chemistry》2005,70(22):9044-9047
[reaction: see text] The preparation of new chiral 6-carbonyl 2,3,8,8a-tetrahydro-7H-oxazolo[3,2-a]pyridines by an efficient two-step procedure is described. 相似文献
524.
The photodetachment microscopy technique, which was originally used with atomic negative ions, is now applied to a molecular anion. The interferograms of several rotational thresholds corresponding to transitions from OH- X (1)Sigma(+) v=0 states to OH X (2)Pi(3/2,1/2) v=0 states have been recorded. No effect due to the 1/r(2) dipolar potential of the neutral molecule appears. Using a double-pass scheme of the laser on the negative ion beam, we measure the energy of the first few detachment thresholds with improved accuracy. The new recommended value of the electron affinity of 16OH is 14,740.996(13) cm(-1), or 1.827 650 3(17) eV. 相似文献
525.
526.
Fabrice Onofri Damien Blondel Grard Grhan Grard Gouesbet 《Particle & Particle Systems Characterization》1996,13(2):104-111
After having recalled basic theoretical results concerning the extension of generalized Lorenz-Mie theory to the case of multilayered spheres, results connected with phase-Doppler anemometry are considered, showing the influence of Gaussian beam intensity profiles on the light scattering properties of these particles. Particular emphasis is placed on the case of water-coated carbon core particles, for which the possibility of obtaining simultaneous size measurements of the core and outer diameters is discussed. The sensitivity of the technique to particles with a refractive index profile is also considered, showing that this technique is more sensitive to changes in the average refractive index of the particles than to refractive index profiles, such as produced by high pressure and temperature stresses, at least for the studied geometry. 相似文献
527.
The coupled effect of a homemade nickel di-dodecyl sulfate precursor and a complexing base leads to beta-Ni(OH)(2) "stack of pancakes" morphology. The mean diameter and thickness of the stacks are around 300 and 200 nm, respectively. Moreover, the amount of ammonia not only monitors crystalline structure but also the size and the shape of particles. 相似文献
528.
[reaction: see text] Co(2)(CO)(6)-complexed alkynyl pinacolborane derivatives are readily transformed with functional group tolerance into fused arylboronates via the [2 + 2 + 2]cycloaddition to alpha,omega-diynes. 相似文献
529.
530.
David O Calvet S Chau F Vanucci-Bacqué C Fargeau-Bellassoued MC Lhommet G 《The Journal of organic chemistry》2004,69(8):2888-2891
We report the results of a study aimed at the diastereoselective synthesis of chiral 2-alkoxy-5-/6-methoxycarbonylmethylidenepyrrolidines/-piperidines by condensation of chiral amines onto omega-oxo alkynoates and omega-oxo beta-keto esters. 相似文献