General soliton matrices in the Riemann-Hilbert problem for integrable nonlinear equations

We derive the soliton matrices corresponding to an arbitrary number of higher-order normal zeros for the matrix Riemann-Hilbert problem of arbitrary matrix dimension, thus giving the complete solution to the problem of higher-order solitons. Our soliton matrices explicitly give all higher-order multisoliton solutions to the nonlinear partial differential equations integrable through the matrix Riemann-Hilbert problem. We have applied these general results to the three-wave interaction system, and derived new classes of higher-order soliton and two-soliton solutions, in complement to those from our previous publication [Stud. Appl. Math. 110, 297 (2003)], where only the elementary higher-order zeros were considered. The higher-order solitons corresponding to nonelementary zeros generically describe the simultaneous breakup of a pumping wave (u(3)) into the other two components (u(1) and u(2)) and merger of u(1) and u(2) waves into the pumping u(3) wave. The two-soliton solutions corresponding to two simple zeros generically describe the breakup of the pumping u(3) wave into the u(1) and u(2) components, and the reverse process. In the nongeneric cases, these two-soliton solutions could describe the elastic interaction of the u(1) and u(2) waves, thus reproducing previous results obtained by Zakharov and Manakov [Zh. Eksp. Teor. Fiz. 69, 1654 (1975)] and Kaup [Stud. Appl. Math. 55, 9 (1976)]. (C) 2003 American Institute of Physics.

Simultaneous activity of male and female gonads in intersex hermit crabs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Simultaneous mode A and mode B echobiometry of senile cataractous eyes in dogs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of sequence of insemination after simultaneous thawing of multiple semen straws on conception rate to timed AI in suckled multiparous Nelore cows

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Prediction equations to estimate the demand of energy and crude protein for maintenance, gain and egg production for laying Japanese quails

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stability of multistep second derivative methods for integro-differential equations

The stability of multistep second derivative methods for integro-differential equations is examined through a test equation which allows for the construction of the associated characteristic polynomial and its region of stability (roots in the unit circle) at a proper parameter space. (c) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous analysis of the enantiomers of verapamil and norverapamil in rat plasma by liquid chromatography tandem mass spectrometry

An enantioselective micromethod for the simultaneous analysis of verapamil (VER) and norverapamil (NOR) in plasma was developed, validated and applied to the study of the kinetic disposition of VER and NOR after the administration of a single oral dose of racemic-VER to rats. VER, NOR and the internal standard (paroxetine) were extracted from only 100-mu L plasma samples using n-hexane and the enantiomers were resolved on a Chiralpak AD column using n-hexane:isopropanol: ethanol: diethyl ami ne (88:6:6:0.1) as the mobile phase. The analyses were performed in the selected reaction monitoring mode. Transitions 456 > 166 for VER enantiomers, 441 > 166 for NOR enantiomers and 330 > 193 for the internal standard were monitored and the method had a total chromatographic run time of 12 min. The method allows the determination of VER and NOR enantiomers at plasma levels as low as 1.0 ng/mL. Racemic VER hydrochloride (10 mg/kg) was given to male Wistar rats by gavage and blood samples were collected from 0 to 6.0 h(n = 6 at each time point). The concentration of (-)-(S)-VER was three folds higher than (+)-(R)-VER, with an AUC ratio (-)/(+) of 2.66. Oral clearance values were 12.17 and 28.77 L/h/kg for (-)-(S)-VER and (+)-(R)-VER, respectively. The pharmacokinetic parameters of NOR were not shown to be enantioselective. (c) 2007 Elsevier B.V. All rights reserved.

Effects of simultaneous exposure to stress and nicotine on nicotine-induced locomotor activation in adolescent and adult rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of strontium and calcium simultaneous substitution on electrical and structural properties of Pb1-x-y Ca (x) Sr (y) TiO3 thin films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stability of neutral functional differential equations in terms of measures

In this paper we investigate the relationships between different concepts of stability in measure for the solutions of an autonomous or periodic neutral functional differential equation.

On retarded differential equations with impulses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Direct and simultaneous spectrophotometric determination of Ni (II) and Co (II) using diethanoldithiocarbamate as complexing agent

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Position-dependent effective mass Dirac equations with PT-symmetric and non-PT-symmetric potentials

We present a new procedure to construct the one-dimensional non-Hermitian imaginary potential with a real energy spectrum in the context of the position-dependent effective mass Dirac equation with the vector-coupling scheme in 1 + 1 dimensions. In the first example, we consider a case for which the mass distribution combines linear and inversely linear forms, the Dirac problem with a PT-symmetric potential is mapped into the exactly solvable Schrodinger-like equation problem with the isotonic oscillator by using the local scaling of the wavefunction. In the second example, we take a mass distribution with smooth step shape, the Dirac problem with a non-PT-symmetric imaginary potential is mapped into the exactly solvable Schrodinger-like equation problem with the Rosen-Morse potential. The real relativistic energy levels and corresponding wavefunctions for the bound states are obtained in terms of the supersymmetric quantum mechanics approach and the function analysis method.

A study of a numerical solution of the steady two dimensions Navier-Stokes equations in a constricted channel problem by a compact fourth order method

We present a numerical solution for the steady 2D Navier-Stokes equations using a fourth order compact-type method. The geometry of the problem is a constricted symmetric channel, where the boundary can be varied, via a parameter, from a smooth constriction to one possessing a very sharp but smooth corner allowing us to analyse the behaviour of the errors when the solution is smooth or near singular. The set of non-linear equations is solved by the Newton method. Results have been obtained for Reynolds number up to 500. Estimates of the errors incurred have shown that the results are accurate and better than those of the corresponding second order method. (C) 2002 Elsevier B.V. All rights reserved.