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排序方式: 共有78条查询结果,搜索用时 15 毫秒
41.
T. Lesinski T. Duguet K. Bennaceur J. Meyer 《The European Physical Journal A - Hadrons and Nuclei》2009,40(2):121-126
We perform systematic calculations of pairing gaps in semi-magic nuclei across the nuclear chart using the Energy Density
Functional method and a non-empirical pairing functional derived, without further approximation, at lowest order in the two-nucleon vacuum interaction, including
the Coulomb force. The correlated single-particle motion is accounted for by the SLy4 semi-empirical functional. Rather unexpectedly,
both neutron and proton pairing gaps thus generated are systematically close to experimental data. Such a result further suggests
that missing effects, i.e. higher partial waves of the NN interaction, the NNN interaction and the coupling to collective fluctuations, provide an overall
contribution that is sub-leading as for generating pairing gaps in nuclei. We find that including the Coulomb interaction
is essential as it reduces proton pairing gaps by up to 40%. 相似文献
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43.
S. Charfi-Kaddour R. Louati A. Ben Ali R. Bennaceur M. Héritier 《Hyperfine Interactions》2001,133(1-4):245-251
The -(BEDT-TTF)2X organic superconductors are described by a two parameter 2D Fermi surface model, in which bandwidth and departure from perfect nesting can be varied. We have studied the spin fluctuations effect on the normal state properties in a Fermi liquid approach using the RPA approximation. The calculated NMR relaxation rate exhibits a peak in 1/(T
1
T), which strongly decreases when the departure from perfect nesting of the Fermi surface and the bandwidth increase. These results are in good agreement with NMR experiments done in -(ET)2X at least qualitatively. In conclusion, we have shown that, in the normal state and with a Fermi liquid approach, the spin fluctuations, which are present in the system due to an imperfect nesting property of the Fermi surface, can induce anomalies of the magnetic properties. Besides, we can restore the usual behaviour like the Korringa law by increasing the bandwidth or by considering a more imperfect nesting. Our calculation reproduces qualitatively the applied pressure relaxation rate experiment done in -(ET)2X salt. 相似文献
44.
A. Hachemi S. Mouhtamid D. Weichert 《Archive of Applied Mechanics (Ingenieur Archiv)》2005,74(11-12):762-772
This paper reports on recent developments in the field of direct methods, in particular shakedown analysis (SA) from theoretical and numerical points of view. Emphasis is placed on problems connected with the failure of fibre-reinforced periodic composites under variable loads where special attention is paid to the problem of interface debonding between fibre and matrix materials. The approach is based on a local SA in a representative volume element of the composite and the use of averaging techniques to study the influence of each component (matrix, fibre and interface) on the macroscopic response of such composite. For numerical applications, the interior-point difference-of-convex-functions algorithm (IPDCA) is proposed as an efficient method for solving large-scale problems. 相似文献
45.
46.
A. Saoudi A. Hachemi A. Ferhat-Hamida Y. Medkour M. Reffas H. Hachemi M. Maamache 《Solid State Communications》2012,152(19):1800-1806
We present an ab initio study of the structural, elastic, electronic and optical properties of CaSrTt (Tt=Si, Ge, Sn and Pb) compounds. To more-accurately describe the properties of these materials, the calculations were based on the DFT theory with the generalized gradient approximation (GGA). In particular, the calculated lattice constants are in good agreement with the experimental results, with a deviation less than 0.67%, 2.74% and 1.7% for a, b and c, respectively. For the equilibrium volume, the deviation does not exceed 4.7%. Single-crystal elastic stiffness (Cij) values were calculated and the polycrystalline elastic moduli (B and G) were estimated utilizing Voigt, Reuss and Hill’s approximations. The electronic band-structure calculations indicate that these compounds are semiconductors, in agreement with the literature data on their Ae2Tt analogues. The dielectric function, refractive index, extinction coefficient, reflectivity spectrum and electron energy loss are calculated over a spectral range from 0 to 45 eV.Unfortunately, there is no available previous study for comparison. 相似文献
47.
The volatile compounds obtained by hydrodistillation of the aerial parts of Rosmarinus tournefortii De Noé. growing wild in the occidental region of Algeria were analyzed by GC/MS. Thirty-six compounds were characterized representing 95.6% of the essential oil, with camphor (37.6%), 1,8-cineole (10.0%), p-cymene-7-ol (7.8%), and borneol (5.4%) as the major components. The antimicrobial activity was evaluated against three pathogenic bacteria: Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus). The minimum inhibitory concentration (MIC; mg/mL) was determined by sub-culture on Muller Hinton agar plates. The essential oil exhibited strong antibacterial activity against E. coli and P. aeruginosa, and was also active against Staphylococcus aureus. 相似文献
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49.
Absolute Asymmetric Synthesis in Enantioselective Autocatalytic Reaction Networks: Theoretical Games,Speculations on Chemical Evolution and Perhaps a Synthetic Option 下载免费PDF全文
Prof. Josep M. Ribó Dr. Celia Blanco Dr. Joaquim Crusats Dr. Zoubir El‐Hachemi Dr. David Hochberg Prof. Albert Moyano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17250-17271
The Soai reaction and the Viedma deracemization of racemic conglomerate crystal mixtures are experimental pieces of evidence of the ability of enantioselective autocatalytic coupled networks to yield absolute asymmetric synthesis. Thermodynamically open systems or systems with non‐uniform energy distributions may lead to chiral final states and, in systems able to come into thermodynamic equilibrium with their surroundings, to kinetically controlled absolute asymmetric synthesis. The understanding of network parameters and of the thermodynamic scenarios that may lead to spontaneous mirror symmetry breaking (SMSB) could assist in the development of new methods for asymmetric synthesis and enantioselective polymerizations (e.g., replicators), and to frame reasonable speculations on the origin of biological homochirality. 相似文献
50.