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91.
For the antiferromagnetic, highly anisotropic XZ and XXZ quantum spin chains, we impose periodic boundary conditions on chains
with an odd number of sites to force an interface (or kink) into the chain. We prove that the energy of the interface depends
on the momentum of the state. This shows that at zero temperature the interface in such chains is not stable. This is in contrast
to the ferromagnetic XXZ chain for which the existence of localized interface ground states has been proven for any amount
of anisotropy in the Ising-like regime.
Received: 15 August 2002 / Accepted: 8 January 2003
Published online: 14 April 2003
RID="⋆"
ID="⋆" ? Copyright rests with the authors. Reproduction of the entire article for non-commercial purposes is permitted.
Communicated by M. Aizenman 相似文献
92.
In an R-parity nonconserving supersymmetric theory, the lighter stop can dominantly decay into b&mgr; and btau if R-parity breaking has to explain the neutrino mass and mixing pattern suggested by the data on atmospheric muon neutrinos. This should give rise to dilepton + dijet and single - lepton + jets, signals identical with those of the top quark at the Fermilab Tevatron. One can thus constrain the stop parameter space using the current top search data and can similarly look for the first signals of supersymmetry at the upgraded runs of the Tevatron. 相似文献
93.
A. Saha A. Ray S. Mukhopadhyay P.K. Datta P.K. Dutta S.M. Saltiel 《Applied physics. B, Lasers and optics》2007,87(3):431-436
An all-solid-state, side diode array pulse pumped Nd:YAG laser tunable for six wavelengths ranging from 1318.8 nm to 1356.0 nm
is developed. The tunability is obtained by using a grating in Littrow mode that also serves as an output coupler. The configuration
ensures a line width as low as 0.04 nm. Thermal effects limit the maximum average power to 250 mW for an average absorbed
pump power of 8.0 W in the free-running condition. An acousto-optic Q-switching of the laser provides pulses of width 251 ns
with peak power of 733 W for an average pump power of 11.5 W. The laser may find application in microsurgery and dermatology.
PACS 42.55.Xi; 42.60.-v; 42.60.Fc; 42.60.Gd; 42.62.Be 相似文献
94.
95.
In this paper a new approach to evaluate the drag force in a simple way on a restricted axially symmetric body placed in a
uniform stream (i) parallel to its axis, (ii) transverse to its axis, is advanced when the flow is governed by the Stokes
equations. The method exploits the well-known integral for evaluating the drag on a sphere. The method not only provides the
value of the drag on prolate and oblate spheroids and a deformed sphere in axial flow which already exists in literature but
also new results for a cycloidal body, an egg shaped body and a deformed sphere in transverse flow. The salient results are
exhibited graphically. The limitations imposed on the analysis because of the lack of fore and aft symmetry in the case of
an eggshaped body is also indicated. It is also seen that the analysis can be extended to calculate the couple on a body rotating
about its axis of symmetry. 相似文献
96.
Atom transfer radical polymerization (ATRP) of ethyl acrylate was carried out in bulk using ethyl 2-bromoisobutyrate as initiator, CuBr as well as CuCl as catalyst in combination with different ligands e.g., 2,2′ bipyridine (bpy)andN,N, N′,N″,N″-pentamethyldiethylenetriamine (PMDETA). In most of the cases very high conversion (72–98%) was achieved. The polymerization was well controlled with a linear increase of molecular weight (MnSEC) with conversion and relatively narrow molecular weight distributions (polydispersity index 1.2–1.3). Use of PMDETA as the ligand resulted in faster polymerization rate (98% conversion in 1 h) than those using bipyridine (72% conversion in 5 h). The MALDI-TOF-MS analysis of poly (ethyl acrylate) (PEA) prepared by using bpy as ligand showed the presence of halogen as the end group. On the contrary, when PMDETA was used as the ligand, the mass analysis showed no trace of this end group. 相似文献
97.
98.
NiFe2O4 (NFO) thin films are grown on four different substrates, i.e., Lead Zinc Niobate–Lead Titanate (PZN–PT), Lead Magnesium Niobate–Lead Titanate (PMN–PT), MgAl2O4 (MAO) and SrTiO3 (STO), by a direct liquid injection chemical vapor deposition technique (DLI-CVD) under optimum growth conditions where relatively high growth rate (~20 nm/min), smooth surface morphology and high saturation magnetization values in the range of 260–290 emu/ cm3 are obtained. The NFO films with correct stoichiometry (Ni:Fe=1:2) grow epitaxially on all four substrates, as confirmed by energy dispersive X-ray spectroscopy, transmission electron microscopy and x-ray diffraction. While the films on PMN–PT and PZN–PT substrates are partially strained, essentially complete strain relaxation occurs for films grown on MAO and STO. The formations of threading dislocations along with dark diffused contrast areas related to antiphase domains having a different cation ordering are observed on all four substrates. These crystal defects are correlated with lattice mismatch between the film and substrate and result in changes in magnetic properties of the films. Atomic resolution HAADF imaging and EDX line profiles show formation of a sharp interface between the film and the substrate with no inter-diffusion of Pb or other elements across the interface. Antiphase domains are observed to originate at the film–substrate interface. 相似文献
99.
Samit Mandal T. Madhusoodhanan Subinit Roy S. Ray H. Majumdar S. Datta S. S. Ghugre S. Ghosh A. Mandal D. K. Avasthi S. K. Datta 《Nuclear Physics A》2003,720(3-4):222-244
Angular distributions of elastic scattering and inelastic scattering from 2+1 state are measured for 16O+142,144,146Nd systems at several energies in the vicinity of the Coulomb barrier. The angular distributions are systematically analyzed in coupled channel framework. Renormalized double folded real optical and coupling potentials with DDM3Y interaction have been used in the calculation. Relevant nuclear densities needed to generate the potentials are derived from shell model wavefunctions. A truncated shell model calculation has been performed and the calculated energy levels are compared with the experimental ones. To simulate the absorption, a ‘hybrid’ approach is adopted. The contribution to the imaginary potential of couplings to the inelastic channels, other than the 2+1 target excitation channel, is calculated in the Feshbach formalism. This calculated imaginary potential along with a short ranged volume Woods–Saxon potential to simulate the absorption in fusion channel reproduces the angular distributions for 16O+146Nd quite well. But for 16O+142,144Nd systems additional surface absorption is found to be necessary to fit the angular distribution data. The variations of this additional absorption term with incident energy and the mass of the target are explored. 相似文献
100.
D. Madhavi LathaV.G.K.M. Pisipati C. Rama Chandra PrabhuP.V. Datta Prasad 《Journal of Molecular Liquids》2011,164(3):187-190
The thermodynamic parameters like Moelwyn-Hughes parameter (C1), reduced molar volume (V~), isochoric temperature coefficient of internal pressure (X), Huggin's parameter (F), Gruneisen parameter (Γp), isothermal microscopic Gruneisen parameter, Sharma parameter (So), fraction free volume (f) and (A?) a dimensionless thermal parameter, etc and the Beyer's nonlinearity parameter (B/A) were deduced employing the thermal expansion coefficient derived from density data for the homologues series of compounds terephthalyidene-bis-p-n-alkyl anilines, TBnA with n = 5 to 10,12,14,16 and 18. Further, it is found that the variation of molecular radius, Mr increases with the increase of alkyl chain number, with a core radius of 4.78 Å and the increment for methylene unit is 0.086 Å . The results were discussed with the body of the data available. 相似文献