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21.
We solve the double exchange model in the presence of arbitrary substitutional disorder by using a self-consistently generated effective Hamiltonian for the spin degrees of freedom. The magnetic properties are studied through classical Monte Carlo while the effective exchange, D(ij), is calculated by solving the disordered fermion problem, and renormalized self-consistently with increasing temperature. We present results on the conductivity, magnetoresistance, optical response, and "real space" structure of the inhomogeneous ferromagnetic state, and compare our results with charge dynamics in disordered La1-xSrxMnO3. The large sizes, O(10(3)), accessible within our method allows a complete, controlled calculation on the disordered strongly interacting problem. 相似文献
22.
Himadri R. Soni Venu Mankad Sanjay D. Gupta Sanjeev K. Gupta Prafulla K. Jha 《Journal of Thermal Analysis and Calorimetry》2012,107(1):39-44
In the present paper, we report an ab initio calculation of the ground state, electronic and thermodynamical properties like
constant volume lattice specific heat, vibrational energy, internal energy, and entropy for GaP and Ga2P is presented. These properties are obtained after calculating the phonon spectrum over the entire Brillouin zone. The calculations
were performed using the ABINIT program package, which is based on density functional theory (DFT) method and the use of pseudopotentials
and plane wave expansion. Difference in the ground state properties such as electronic structure and thermodynamical properties
are discussed. The thermodynamical properties follow the expected trend. There is a good agreement between present theoretical
and limited available experimental data in the case of ground state such as lattice constant and bulk modulus and electronic
properties. With the increase of Ga atoms in the unit cell the semiconducting nature of Ga2P turns to metallic. There is a noticeable difference in the thermodynamical properties in the case of both gallium compounds. 相似文献
23.
Kuldeep Sharma Gopal V. Pawar Sanjeev Giri Sriram Rajagopal Ramesh Mullangi 《Biomedical chromatography : BMC》2012,26(12):1589-1595
A highly sensitive, rapid assay method has been developed and validated for the estimation of bicalutamide in mouse plasma using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the negative‐ion mode. The assay procedure involves extraction of bicalutamide and tolbutamide (internal standard, IS) from mouse plasma with a simple protein precipitation method. Chromatographic separation was achieved using an isocratic mobile phase (0.2% formic acid:acetonitrile, 35:65, v/v) at a flow rate of 0.5 mL/min on an Atlantis dC18 column (maintained at 40 ± 1°C) with a total run time of 3.0 min. The MS/MS ion transitions monitored were m/z 428.9 → 254.7 for bicalutamide and m/z 269.0 → 169.6 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 1.04 ng/mL and the linearity range extended from 1.04 to 1877 ng/mL. The intra‐ and inter‐day precisions were in the ranges of 0.49–4.68 and 2.62–4.15, respectively. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
24.
The rectangular dielectric waveguide is the most commonly used structure in integrated optics, especially in semi-conductor
diode lasers. Demands for new applications such as high-speed data backplanes in integrated electronics, waveguide filters,
optical multiplexers and optical switches are driving technology toward better materials and processing techniques for planar
waveguide structures. The infinite slab and circular waveguides that we know are not practical for use on a substrate because
the slab waveguide has no lateral confinement and the circular fiber is not compatible with the planar processing technology
being used to make planar structures. The rectangular waveguide is the natural structure. In this review, we have discussed
several analytical methods for analyzing the mode structure of rectangular structures, beginning with a wave analysis based
on the pioneering work of Marcatili. We study three basic techniques with examples to compare their performance levels. These
are the analytical approach developed by Marcatili, the perturbation techniques, which improve on the analytical solutions
and the effective index method with examples.
T Srinivas received the B.Sc. (Hon.) degree from Nehru Science College, Hydrabad and M.E. (Int.) and Ph.D. dgrees from the Indian Institute
of Science, Bangalore, India. He was a Postdoctoral Research Fellow at Toyohashi University of Technology, Japan from 1992
to 1996. He is currently an Associate Professor with the Department of Electrical Communication Engineering, Indian Institute
of Science. His areas of interests are optical communication networks, integrated optics, micro-opto-electrical-mechanical
systems (MOEMS) and fiberoptic sensors 相似文献
25.
It is shown that SU(2)×U(1) can be broken at the tree level, without the occurrence of global potential minima that break
U(1)e.m., in supergravity models that are more general than those proposed by Nilles, Srednicki and Wyler. The study comprises an
analysis of models with a general soft supersymmetry-breaking structure as well as those of the Hall-Lykken-Weinberg type. 相似文献
26.
1-Decanethiol has been found to be an excellent reagent for the deprotection of aryl methyl ethers. This newly developed protocol afforded the corresponding phenols in good to excellent yields. A clear advantage of 1-decanethiol over the more commonly used thiols is the easy extraction of both the deprotecting reagent and the reaction byproduct into the aqueous phase, which allows an essentially odorless work-up. 相似文献
27.
The interplay between spectator and participant matter in heavy-ion collisions is investigated within the isospin-dependent
quantum molecular dynamics (IQMD) model in terms of the rapidity distribution of light charged particles. The effect of different
types and sizes of rapidity distributions is studied in elliptical flow. The elliptical-flow patterns show the important role
of nearby spectator matter on the participant zone. This role is further explained on the basis of the passing time of the
spectator and the expansion time of the participant zone. The transition from in-plane to out-of-plane emission is observed
only when the mid-rapidity region is included into the rapidity bin. Otherwise no transition occurs. The transition energy
is found to be highly sensitive to the size of the rapidity bin, while it is only weakly dependent on the type of the rapidity
distribution. These theoretical findings are found to be in agreement with experimental results. 相似文献
28.
The reported work has been focused on the improvement of electrical parameters of Schottky diode using vacuum annealing at mild temperature in Ar gas ambient. Nickel Schottky barrier diodes were fabricated on 50 μm epitaxial layer of n-type 4H-SiC (0 0 0 1) substrate. The values of leakage current, Schottky barrier height (?B), ideality factor (η) and density of interface states (NSS) were obtained from experimentally measured current–voltage (I–V) and capacitance–voltage (C–V) characteristics before and after vacuum annealing treatment. The data revealed that ?B, η and reverse leakage current for the as-processed diodes are 1.25 eV, 1.6 and 1.2 nA (at ?100 V), respectively, while for vacuum annealed diodes these parameters are 1.36 eV, 1.3 and 900 pA (at same reverse voltage). Improved characteristics have been resulted under the influence of vacuum annealing because of lesser number of minority carrier generation due to incessant reduction of number of available discrete energy levels in the bandgap of 4H-SiC substrate and lesser number of interface states density at Ni/4H-SiC (0 0 0 1) interface. 相似文献
29.
Venu MankadHimadri R. Soni Sanjeev K. GuptaPrafulla K. Jha 《Physica B: Condensed Matter》2011,406(19):3599-3604
We present results of first principles total energy calculations of the structure, electronic and lattice dynamics for beryllium semiboride and its three ternary alloys using generalized gradient and local density approximations under the framework of density functional theory. The generalized gradient approximation is used for all compounds except MgBeB using the Perdew-Burke-Ernzehorf exchange correlation functional while local density approximations use the Perdew-Zunger ultrasoft exchange correlation functional. The calculated ground state structural parameters are in good agreement with those of experimental and previous theoretical studies. The electronic band structure calculations show that Be2B may transform to a semiconductor after Al substitution. A linear response approach to density functional theory is used to calculate phonon dispersion curves and vibrational density of states. The phonon dispersion curves of Be2B and AlBeB are positive indicating a dynamical stablility of the structure for these compounds. The phonon dispersion curves of NaBeB and MgBeB show the imaginary phonons throughout the Brillouin zone, which confirms dynamical instability as indicated in band structures for these alloys. We also present the partial phonon density of states for different species of Be2B and AlBeB to bring out the details of the participation of different atoms in the total phonon density of state, particularly the role played by Al atom. The first time calculated phonon properties are clearly able to bring out the significant effect of isoelectronic substitution in Be2B. 相似文献
30.
Let (K,v) be a discrete rank one valued field with valuation ring Rv. Let L/K be a finite extension such that the integral closure S of Rv in L is a finitely generated Rv-module. Under a certain condition of v -regularity, we obtain some results regarding the explicit computation of Rv-bases of S, thereby generalizing similar results that had been obtained for algebraic number fields in El Fadil et al. (2012) [7]. The classical Theorem of Index of Ore is also extended to arbitrary discrete valued fields. We give a simple counter example to point out an error in the main result of Montes and Nart (1992) [12] related to the Theorem of Index and give an additional necessary and sufficient condition for this result to be valid. 相似文献