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排序方式: 共有594条查询结果,搜索用时 15 毫秒
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Mauro?Bologna Gerardo?AquinoEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(1):15
We derive the probability density of a diffusion process generated by nonergodic velocity fluctuations in presence of a weak potential, using the Liouville equation approach. The velocity of the diffusing particle undergoes dichotomic fluctuations with a given distribution ψ(τ) of residence times in each velocity state. We obtain analytical solutions for the diffusion process in a generic external potential and for a generic statistics of residence times, including the non-ergodic regime in which the mean residence time diverges. We show that these analytical solutions are in agreement with numerical simulations. 相似文献
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95.
Castelaín M Martínez G Merino P Martín-Gago JÁ Segura JL Ellis G Salavagione HJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):4965-4973
Graphene flakes covalently modified with a conjugated polymer, poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis-(6-azidohexyl)fluorene)] (PFA), were efficiently synthesised by a Cu-catalysed Huisgen 1,3-dipolar cycloaddition between alkyne-modified graphene and an azide-functionalised polymer. Two approaches for the modification of graphene with alkyne groups were investigated (coupling with a diazonium salt generated in situ or an amidation reaction) and the optimum conditions determined. The success of the click-coupling approach was confirmed by FTIR, (1)H?NMR, Raman, and X-ray photoelectron spectroscopy (XPS). The absorption and emission spectra of the click product show a strong solvent dependency. 相似文献
96.
We present a time-reversal invariant s-wave superconductor supporting Majorana edge modes. The multiband character of the model together with spin-orbit coupling are key to realizing such a topological superconductor. We characterize the topological phase diagram by using a partial Chern number sum, and show that the latter is physically related to the parity of the fermion number of the time-reversal invariant modes. By taking the self-consistency constraint on the s-wave pairing gap into account, we also establish the possibility of a direct topological superconductor-to-topological insulator quantum phase transition. 相似文献
97.
Ketamine is an analgesic/anesthetic drug, which, in combination with other drugs, has been used as anesthetic for over 40 years. Ketamine induces its analgesic activities by blocking the N-methyl-D-aspartate (NMDA) receptor in the central nervous system (CNS). We have reported that low doses of ketamine administrated to patients before incision significantly reduced post-operative inflammation as reflected by reduced interleukin-6 (IL-6) sera-levels. Our data demonstrated in a rat model of Gram-negative bacterial-sepsis that if we inject a low dose of ketamine following bacterial inoculation we reduce mortality from approximately 75% to 25%. Similar to what we have observed in operated patients, the levels of TNF-α and IL-6 in ketamine-treated rats were significantly lower than in septic animals not treated with ketamine. On the base of these results, we have designed and synthesized series of new analogues of ketamine applying a thermal rearrangement of alicyclic α-hydroxyimines to a-aminoketones in parallel arrays. One of the analogues (compound 6e) displayed high activity in down-regulating the levels of IL-6 and TNF-α in vivo as compared to ketamine. 相似文献
98.
We report the synthesis of HKUST‐1 (Cu3(btc)2; btc=benzene‐1,3,5‐tricarboxylate) and its growth kinetics by dynamic light scattering completely at room temperature without prior nucleation‐induction steps. Upon an increase in concentration of the starting solutions, the generation of a pure phase requires adjustment of the H2O/EtOH ratio. The presence of DMF is important to avoid competitive side phases. Replacement of DMF by a minimal amount of diethylamine resulted in the instantaneous formation of pure HKUST‐1 upon mixing at room temperature. Additionally, the synthesis parameters strongly influence the final crystallite size and porous properties. 相似文献
99.
A full-dimensional quantum dynamics study is carried out for the highly fluxional H(5)(+) cation on a recent reference potential energy surface by using the multi configuration time-dependent Hartree method. With five equivalent light atoms and shallow barriers between various low-lying stationary points on the surface, the spectroscopic characterization of H(5)(+) represents a huge challenge for accurate quantum dynamics simulations. The present calculation is the first such a study on this cation, which together with its isotope analogies are of primary importance in the interstellar chemistry. The vibrational ground state properties and several vibrationally excited states corresponding to low vibrational frequency motions, not yet directly observable by the experiment, are presented and analyzed. 相似文献
100.
Ferdinando Mancini Evgeny Plekhanov Gerardo Sica 《Central European Journal of Physics》2012,10(3):609-614
In this paper we study a generalization of the Hubbard model by considering spin-spin interactions described by the exchange constant J. An external magnetic field his also taken into account. In the narrowband limit and for the 1D case, we present the exact solution obtained in the framework of the Green’s function formalism, using the Composite Operator Method. We report the T = 0 phase diagram for both ferro (J > 0) and anti-ferro (J < 0) couplings. The competition of the different energy scales (U, J, and h; being U the local charge interaction) generates a variety of phases and different charge and spin orderings. 相似文献