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One-dimensional Systems (one-dimensional + system)
Selected AbstractsA Crystalline Phase Transition and Optical Properties in a CoIICuII Oxamato-Bridged Ferrimagnetic ChainEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Cynthia L. M. Pereira Abstract The compound [CoCu(opba)(DMSO)3] (1) [opba = ortho -phenylenebis(oxamato)] has been synthesized and characterized. Its crystal structure has been analyzed by X-ray diffraction techniques at 100 and 298 K. A structural phase-transition has been detected at around 150 K. An orthorhombic crystalline system is found at both temperatures, with very similar unit-cell dimensions. At room temperature 1 crystallizes in the Pnam space group (, -1 phase), with a = 7.6712(2), b = 14.8003(3), c = 21.0028(5) Å, and Z = 4, whereas at low temperature it crystallizes in the Pna21 space group (, -1 phase), with a = 7.3530(2), b = 14.5928(4), c = 21.0510(7) Å, and Z = 4. Both crystalline phases consist of linearly ordered bimetallic chains with the [Cu(opba)]2, units tied by CoII ions to form a one-dimensional system. The DMSO molecules in , -1, which are coordinated to either CuII or CoII, are disordered. At low temperature, a small reorganization of the CuII and CoII environments is observed. The origin of this phase transition, which is completely reversible, is the modification of the crystalline packing with the temperature. Linear birefringence measurements were done on single crystals in the 100,300 K temperature range. Around 150 K, the linear birefringence curve shows an inflexion that is interpreted as being related to the conversion of ,-1 into , -1. Both dc and ac magnetic measurements were performed on the polycrystalline sample. The results reveal a one-dimensional ferrimagnetic behavior. Single crystal optical characterization at room temperature shows that 1 presents a very strong dichroism superposed on the linear birefringence. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] On the evolution of thin viscous jets: filament formationMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 10 2004Marco A. Fontelos Abstract In this paper, we have studied the evolution of thin fluid jets, paying special attention on the limit of very large viscosity. Local well-posedness of the one-dimensional system describing this evolution as well as the existence of break-up (at least as t , ,) under quite general conditions is proved. In addition, we have proved the well-known experimental fact that in the limits of very large viscosities the solutions develop very long and thin filaments previous to break-up and a complete detailed description of their structure is given. Copyright © 2004 John Wiley & Sons, Ltd. [source] Disordered lattice networks: general theory and simulationsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 6 2005Stefano GiordanoArticle first published online: 16 NOV 200 Abstract In this work we develop a theory for describing random networks of resistors of the most general topology. This approach generalizes and unifies several statistical theories available in literature. We consider an n-dimensional anisotropic random lattice where each node of the network is connected to a reference node through a given random resistor. This topology includes many structures of great interest both for theoretical and practical applications. For example, the one-dimensional systems correspond to random ladder networks, two-dimensional structures model films deposited on substrates and three-dimensional lattices describe random heterogeneous materials. Moreover, the theory is able to take into account the anisotropic percolation problem for two- and three-dimensional structures. The analytical results allow us to obtain the average behaviour of such networks, i.e. the electrical characterization of the corresponding physical systems. This effective medium theory is developed starting from the properties of the lattice Green's function of the network and from an ad hoc mean field procedure. An accurate analytical study of the related lattice Green's functions has been conducted obtaining many closed form results expressed in terms of elliptic integrals. All the theoretical results have been verified by means of numerical Monte-Carlo simulations obtaining a remarkably good agreement between numerical and theoretical values. Copyright © 2005 John Wiley & Sons, Ltd. [source] Coupled-perturbed Hartree,Fock theory for quasi,one-dimensional periodic systems: Calculation of static and dynamic nonlinear optical properties of model systemsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2003A. Martinez Abstract An alternative method to solve the coupled-perturbed Hartree,Fock (CPHF) equations for infinite quasi,one-dimensional systems is presented. The new procedure follows a proposal made by Langhoff, Epstein, and Karplus to obtain perturbed wavefunctions free from arbitrary phase factors in each order of perturbation. It is based on the intermediate orthonormalization of the perturbed wavefunctions (which is different from the usual one) and a corresponding selection of the Lagrangian multipliers. In this way it is possible to incorporate the orthonormalization conditions into the set of CPHF equations. Moreover, a new, advantageous procedure to determine the derivatives of the wavefunction with respect to the quasimomentum k is presented. We report calculations of the dipole moment, the polarizability ,, and the first hyperpolarizability , for different polymers (poly-HF, poly-H2O, trans-polyacetylene, polyyne, and polycarbonitrile) for different frequencies. These results are extensively compared with oligomer calculations. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 251,268, 2003 [source] Delta and singular delta locus for one-dimensional systems of conservation lawsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 8 2004Marko Nedeljkov Abstract This work gives a condition for existence of singular and delta shock wave solutions to Riemann problem for 2×2 systems of conservation laws. For a fixed left-hand side value of Riemann data, the condition obtained in the paper describes a set of possible right-hand side values. The procedure is similar to the standard one of finding the Hugoniot locus. Fluxes of the considered systems are globally Lipschitz with respect to one of the dependent variables. The association in a Colombeau-type algebra is used as a solution concept. Copyright © 2004 John Wiley &Sons, Ltd. [source] Lack of universal conductance features in disordered graphene nanoribbonsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Antonino La Magna Abstract Recent experimental characterisation of graphene flakes has demonstrated the existence of local structural alterations of the ideal honeycomb lattice whose influence on the conductance mechanism of this material has not yet been fully evaluated. In this study a numerical statistical analysis of the conductance distribution function in disordered graphene nanoribbons is presented. Calculations are performed in statistically equivalent replica large systems within the Non Equilibrium Green's Function formalism. Different kinds of local scattering centers have been considered. A characteristic general behavior of the conductance variance in these quasi one-dimensional systems is the linear scaling with the average of logarithm of the conductance, in the localization regime. However, in a broad class of realization of the local disorder, the slope is not a constant as the disorder degree varies in any region of the energy spectrum, i.e. the single parameters scaling hypothesis is not verified (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Local level statistics for optical and transport properties of disordered systems at finite temperaturePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006A. Malyshev Abstract It is argued that the (traditional) global level statistics which determines localization and coherent transport properties of disordered systems (e.g. the Anderson model) at zero temperature becomes inappropriate when it comes to incoherent transport. We define local level statistics which proves to be relevant for finite temperature incoherent transport and optics of one-dimensional systems (e.g. molecular aggregates, conjugated polymers, etc.). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] On Hamiltonian perturbations of hyperbolic systems of conservation laws I: Quasi-Triviality of bi-Hamiltonian perturbationsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 4 2006Boris Dubrovin We study the general structure of formal perturbative solutions to the Hamiltonian perturbations of spatially one-dimensional systems of hyperbolic PDEs vt + [,(v)]x = 0. Under certain genericity assumptions it is proved that any bi-Hamiltonian perturbation can be eliminated in all orders of the perturbative expansion by a change of coordinates on the infinite jet space depending rationally on the derivatives. The main tool is in constructing the so-called quasi-Miura transformation of jet coordinates, eliminating an arbitrary deformation of a semisimple bi-Hamiltonian structure of hydrodynamic type (the quasi-triviality theorem). We also describe, following [35], the invariants of such bi-Hamiltonian structures with respect to the group of Miura-type transformations depending polynomially on the derivatives. © 2005 Wiley Periodicals, Inc. [source] | |||||||||||||