Topological and dynamical excitations in a classical 2D easy-axis Heisenberg model

The properties of dynamical solitons (magnon droplets) in the classical, two-dimensional anisotropic Heisenberg model with easy-axis exchange anisotropy are studied. The solution of the Landau-Lifshitz equation in the continuum limit for the soliton with topological charge q = 1 is obtained numerically using a shooting method. We analized a wide range of the anisotropy parameter and our results are in good agreement with results obtained from spin dynamics simulations. The dependence of an internal precession frequency of the soliton on both the anisotropy parameter and the radius of the soliton is also investigated. Finally, the limits of applicability of the continuum approach are discussed. Received 22 August 2000     

Finite-size,chemical-potential and magnetic effects on the phase transition in a four-fermion interacting model

We study effects coming from finite size, chemical potential and from a magnetic background on a massive version of a four-fermion interacting model. This is performed in four dimensions as an application of recent developments for dealing with field theories defined on toroidal spaces. We study effects of the magnetic field and chemical potential on the size-dependent phase structure of the model, in particular, how the applied magnetic field affects the size-dependent critical temperature. A connection with some aspects of the hadronic phase transition is established.     

Optimization of electric propulsion system for a hybridized vehicle

The reduction of vehicle fuel consumption is one of the most important targets for the automotive industry. Plug-in electric vehicles (PHEVs) are considered a viable alternative to improve the vehicle performance and efficiency. This study presents a prototype of a hybridization kit to convert a conventional vehicle into a PHEV that results in an expressive reduction of fuel consumption. Due to this, an interactive adaptive-weight genetic algorithm optimization was applied to find out optimum configurations for the hybridization kit in order to minimize the overall cost to perform FTP-75 and US06 driving cycles and to improve performance.     

Investigating Route to Chaos in Nonlinear Plasmonic Dimer

The route to chaos of a plasmonic dimer formed of two identical nanoparticles with Kerr-type nonlinear response and illuminated by an external electric field is reported. It is shown that this system has a complex dynamical behavior with chaotic nature. This complexity is analyzed using Lyapunov exponents, the Kaplan–Yorke dimension, and correlation dimensions. The existence of familiar period-doubling sequences route to chaos is pointed out, and domains corresponding to the onset of period doubling and chaos in the plane of parameters are evidenced.     

The Use of Low Field NMR and Thermal Analysis to the Wood Polymer Composite Study

Summary: The focus of this work was to characterize the molecular dynamic of High Impact Polystyrene (HIPS - 5% PB), wood - A (Vochysia divergens) and B (Erisma uncinatum) - and their composites, using solid state nuclear magnetic resonance (NMR), by measuring the proton spin-lattice relaxation time (T₁H) using a low field NMR, and by thermal analysis as Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). DSC and TGA measurements show that both woods present the same molecular behavior. On the other hand, the spin-lattice relaxation time observed that the water is interfering in the packing and arrangements of cellulose chains due to inter and intra hydrogen molecular interactions, promoting the T₁H values changed to high values. T₁H shows that the sample B presents a higher rigidity than sample A. However, HIPS presents higher T₁H values comparing to wood types. Analyzing the relaxation data for the composites, the values indicate that composites present an interaction between both components.     

Mechanism of the solid state reaction NaCl + KF → NaF + KCl

The mechanism of the solid state displacement reaction NaCl + KF → NaF + KCl was investigated, employing diffusion couples (single crystals), in air at 550°C.The product layer obtained was formed with NaF and (Na, K)Cl solid solution.From cation concentration profiles, photometrically determined, for the NaClz.sfnc;KF and NaCl|KCl systems after annealing at 550°C, and from X-ray diffraction analysis on product layer surfaces for the NaCl|KF system, it was possible to state that the overall process is governed by a cation-counterdiffusion mechanism.A comparison between the diffusion coefficient evaluated through the rate constant and that calculated by means of the Boltzmann-Matano analysis for the system NaClKCl, allows one to deduce that the cations Na⁺ and K⁺ are transported in the (Na, K)Cl solid solution.     

Réaction du diméthylcuprate de lithium avec les dérivés carbonylés α,β-insaturés α-fluorés et α-chlorés

Depending on the nature of the halogen, α-fluoro- and α-chloro-α,β-unsaturated carbonyl compounds (whose reduction potentials are greater than ? 2.4V) react in different ways with lithium dimethylcuprate. With α-fluoro derivatives, both 1,2- and 1,4-addition is observed, their ratios depend on the steric hindrance of the β-position. 1,4-Addition products are obtained from aldehydes and β-monosubstituted α-chloro-α,β-ethylenic ketones and esters. β,β-Disubstituted α-chloro ketones and esters give only reduction of halogen via halogen-metal exchange.     

A note on semigroups, groups and geometric lattices

Let G be a closed, additive semigroup in a Hausdorff topological vector space. Then G is a group if and only if it satisfies natural convexity conditions of algebraic or geometric-topological type. This yields a characterization of the geometric lattices among the discrete, additive semigroups of Euclidean d-space \mathbbE^d{\mathbb{E}^{d}} and, more generally, of direct sums of subspaces and lattices in \mathbbE^d{\mathbb{E}^{d}}.     

Direct introduction of slurry samples in multi-syringe flow injection analysis: determination of potassium in plant samples.

The present work explores the slurry sampling approach for automatic, flow-based plant analysis. For this purpose, pinch valves were introduced into a multi-syringe flow injection analysis manifold to provide the repeatable aspiration of a few microliters of plant suspension before the material was further processed through the flow system. For validation of the proposed approach, the determination of potassium by flame emission spectrometry was implemented. Several parameters were studied: the concentration of plant particles in the sample suspension and the utilization of matrix modifiers. Microwave digestion was also implemented; no significant difference was found when certified reference material was analyzed with or without the in-line digestion step. The system was successfully applied to 13 samples within a concentration range of 2.5 to 100 mg g(-1). A determination frequency of 28 h(-1) was achieved and the precision was better than 4.0% (n = 12).     

The mixed Hodge–Riemann bilinear relations for compact Kähler manifolds

We prove the Hodge–Riemann bilinear relations, the hard Lefschetz theorem and the Lefschetz decomposition for compact K?hler manifolds in the mixed situation. Dedicated to Professor Henri Skoda on the occasion of his 60th birthday Received: February 2005; Revision: March 2005; Accepted: April 2005