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931.
Structural, electronic, and optical properties of alloys Be_xMg_(1-x)X(X = S, Se, Te) in the assortment 0 x 1 were theoretically reported for the first time in zinc-blende(ZB) phase. The calculations were carried out by using full-potential linearized augmented plane wave plus local orbitals(FP-LAPW+lo) formalism contained by the framework of density functional theory(DFT). Wu-Cohen(WC) generalized gradient approximation(GGA), based on optimization energy,has been applied to calculate these theoretical results. In addition, we used Becke and Johnson(m BJ-GGA) potential,modified form of GGA functional, to calculate electronic structural properties up to a high precision degree. The alloys were composed with the concentrations x = 0.25, 0.5, and 0.75 in pursuance of ‘special quasi-random structures'(SQS)approach of Zunger for the restoration of disorder around the observed site of alloys in the first few shells. The structural parameters have been predicted by minimizing the total energy in correspondence of unit cell volume. Our alloys established direct band gap at different concentrations that make their importance in optically active materials. Furthermore, density of states was discussed in terms of the contribution of Be and Mg s and chalcogen(S, Se, and Te) s and p states and observed charge density helped us to investigate the bonding nature. By taking into consideration of immense importance in optoelectronics of these materials, the complex dielectric function was calculated for incident photon energy in the range 0-15 eV. 相似文献
932.
The random walk simulation of a Levy flight shows a linear relation between the mean square displacement 〈r2〉 and time. We have analyzed different aspects of this linearity. It is shown that the restriction of jump length to a maximum value (lm) affects the diffusion coefficient, even though it remains constant for lm greater than 1464. So, this factor has no effect on the linearity. In addition, it is shown that the number of samples does not affect the results. We have demonstrated that the relation between the mean square displacement and time remains linear in a continuous space, while continuous variables just reduce the diffusion coefficient. The results also imply that the movement of a Levy flight particle is similar to the case in which the particle moves in each time step with an average jump length 〈l〉. Finally, it is shown that the non-linear relation of the Levy flight will be satisfied if we use a time average instead of an ensemble average. The difference between the time average and ensemble average results shows that the Levy distribution may be a non-ergodic distribution. 相似文献
933.
Malek Taher Maghsoodlou Sayyed Mostafa Habibi Khorassani Nourollah Hazeri Mohsen Rostamizadeh Seyed Sajad Sajadikhah Zahra Shahkarami Nariman Maleki 《Heteroatom Chemistry》2009,20(5):316-318
α‐Amino phosphonates were obtained in a one‐pot, simple, and efficient method from the reaction between aldehyde, aniline, trialkyl phosphite, and silica sulfuric acid as a catalyst in acetonitrile at room temperature. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:316–318, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20543 相似文献
934.
We report results of first-principles total-energy calculations for structural properties of the group I-VII silver iodide (AgI) semiconductor compound under pressure for B1 (rocksalt), B2 (cesium chloride), B3 (zinc-blende) and B4 (wurtzite) structures. Calculations have been performed using all-electron full-potential linearized augmented plane wave plus local orbitals FP-LAPW + lo method based on density-functional theory (DFT) and using generalised gradient approximation (GGA) for the purpose of exchange correlation energy functional. In agreement with experimental and earlier ab initio calculations, we find that the B3 phase is slightly lower in energy than the B4 phase, and it transforms to B1 structure at 4.19 GPa. Moreover, we found AgI has direct gap in B3 structure with a band gap of 1.378 eV and indirect band gap in B1 phase with a bandgap around 0.710 eV. We also present results of the effective masses for the electrons in the conduction band (CB) and the holes in the valence band (VB). To complete the fundamental characteristics of this compound we have analyzed their linear optical properties such as the dynamic dielectric function and energy loss function for a wide range of 0-25 eV. 相似文献
935.
Diabetes is a major public health problem. Development of new therapies that are able to improve glycemia management, cure diabetes, and can even protect from it, are of great interest. This study investigated the protective effect of sodium tungstate against STZ-induced beta-cell damages by means of stereological methods. Sixty rats were divided into six groups: control (C), tungstate-treated control (TC), STZ-induced diabetic (D), STZ-induced diabetic rats were treated by sodium tungstate from 1 week before STZ injection (TDB), food-restricted diabetic (FRD), and diabetic rats treated with sodium tungstate 1 week after STZ administration (TDA). Stereological estimation of pancreas volume, islets volume density, volume-weighted mean islets volume and mass of beta cells, islets, and pancreas and total number of islets were done. Islets volume density, volume-weighted mean islets volume, and mass of beta cells, islets, and pancreas of TDB group was significantly higher than D, FRD and TDA groups (P < 0.001) and was comparable to controls (C and TC groups). Total number of islets, pancreas wet weight and volume did not show any significant changes between these groups (P > 0.05).Results suggested that sodium tungstate preserves pancreatic beta cells from STZ-induced damages and diabetes induction in rats. 相似文献
936.
Bassam A. Abu Thaher Jalal A. Zahra Mustafa M. El‐Abadelah 《Journal of heterocyclic chemistry》2002,39(5):901-904
2‐Aminobenzoic acid reacts readily, in the presence of triethylamine, with hydrazonoyl chlorides ( 5a‐c ) (precursors of the reactive nitrile imine 1,3‐dipolar species) to afford high yields of the corresponding acyclic amidrazone adducts ( 6a‐c ). The latter adducts undergo, in THF in presence of 1,1‐carbonyldiimida‐zole, smooth intramolecular cyclization involving the activated carboxyl and the NH‐ termini to deliver unequivocally the respective dihydro‐1,3,4‐benzotriazepin‐5‐ones ( 7a‐c ). 相似文献
937.
Khalid Rashid 《Zeitschrift für Physik A Hadrons and Nuclei》1970,235(2):181-190
It is shown that even nonlocal generalizations of the usual expressions for
- the particle probability density of mass zero, spin zero (one) bosons;
- the energy density of mass zero spin one half fermions;
938.
Intramolecular Diels-Alder cyclization of readily available polyenes leads to regio- and stereoselective synthesis of dehydroindanes derivatives. 相似文献
939.
Mubasher Jamil Asghar Qadir Muneer Ahmad Rashid 《The European Physical Journal C - Particles and Fields》2008,58(2):325-329
In the classical relativistic regime, the accretion of phantom-like dark energy onto a stationary black hole reduces the mass
of the black hole. We have investigated the accretion of phantom energy onto a stationary charged black hole and have determined
the condition under which this accretion is possible. This condition restricts the mass-to-charge ratio in a narrow range.
This condition also challenges the validity of the cosmic-censorship conjecture since a naked singularity is eventually produced
due to accretion of phantom energy onto black hole. 相似文献
940.
Rashid Ahmed Fazal-e-Aleem S. Javad Hashemifar Hadi Akbarzadeh 《Physica B: Condensed Matter》2007,400(1-2):297-306
A theoretical study of structural and electronic properties of the four phases of BN (zincblende, wurtzite, hexagonal and rhombohedral) is presented. The calculations are done by full potential (linear) augmented plane wave plus local orbitals (APW+lo) method based on the density functional theory (DFT) as employed in WIEN2k code. Using the local density approximation (LDA) and generalized gradient approximation (GGA-PBE) for the exchange correlation energy functional, we have calculated lattice parameters, bulk modulus, its pressure derivative and cohesive energy. In order to calculate electronic band structure, another form of the generalized gradient approximation proposed by Engel and Vosko (GGA-EV) has been employed along with LDA and GGA-PBE. It is found that all the three approximations exhibit similar band structure qualitatively. However, GGA-EV gives energy band gap values closer to the measured data. Our results for structural and electronic properties are compared with the experimental and other theoretical results wherever these are available. 相似文献