Fast, scalable master equation solution algorithms. III. Direct time propagation accelerated by a diffusion approximation preconditioned iterative solver

In this paper we propose a novel fast and linearly scalable method for solving master equations arising in the context of gas-phase reactive systems, based on an existent stiff ordinary differential equation integrator. The required solution of a linear system involving the Jacobian matrix is achieved using the GMRES iteration preconditioned using the diffusion approximation to the master equation. In this way we avoid the cubic scaling of traditional master equation solution methods and maintain the low temperature robustness of numerical integration. The method is tested using a master equation modelling the formation of propargyl from the reaction of singlet methylene with acetylene, proceeding through long lived isomerizing intermediates. (C) 2003 American Institute of Physics.

Calculation of bound and resonance states of HO2 for nonzero total angular momentum

Bound and resonance states of HO2 have been calculated quantum mechanically by the Lanczos homogeneous filter diagonalization method [Zhang and Smith, Phys. Chem. Chem. Phys. 3, 2282 (2001); J. Chem. Phys. 115, 5751 (2001)] for nonzero total angular momentum J = 1,2,3. For lower bound states, agreement between the results in this paper and previous work is quite satisfactory; while for high lying bound states and resonances these are the first reported results. A helicity quantum number V assignment (within the helicity conserving approximation) is performed and the results indicate that for lower bound states it is possible to assign the V quantum numbers unambiguously, but for resonances it is impossible to assign the V helicity quantum numbers due to strong mixing. In fact, for the high-lying bound states, the mixing has already appeared. These results indicate that the helicity conserving approximation is not good for the resonance state calculations and exact quantum calculations are needed to accurately describe the reaction dynamics for HO2 system. Analysis of the resonance widths shows that most of the resonances are overlapping and the interferences between them lead to large fluctuations from one resonance to another. In accord with the conclusions from earlier J = 0 calculations, this indicates that the dissociation of HO2 is essentially irregular. (C) 2003 American Institute of Physics.

Link invariants associated with gauge equivalent solutions of the Yang-Baxter equation: The one-parameter family of minimal typical representations of Uq[gl(2|1)]

In this paper we investigate the construction of state models for link invariants using representations of the braid group obtained from various gauge choices for a solution of the trigonometric Yang-Baxter equation. Our results show that it is possible to obtain invariants of regular isotopy (as defined by Kauffman) which may not be ambient isotopic. We illustrate our results with explicit computations using solutions of the trigonometric Yang-Baxter equation associated with the one-parameter family of minimal typical representations of the quantum superalgebra U-q,[gl(2/1)]. We have implemented MATHEMATICA code to evaluate the invariants for all prime knots up to 10 crossings.

A review of drainage and spontaneous rupture in free standing thin films with tangentially immobile interfaces

A review of spontaneous rupture in thin films with tangentially immobile interfaces is presented that emphasizes the theoretical developments of film drainage and corrugation growth through the linearization of lubrication theory in a cylindrical geometry. Spontaneous rupture occurs when corrugations from adjacent interfaces become unstable and grow to a critical thickness. A corrugated interface is composed of a number of waveforms and each waveform becomes unstable at a unique transition thickness. The onset of instability occurs at the maximum transition thickness, and it is shown that only upper and lower bounds of this thickness can be predicted from linear stability analysis. The upper bound is equivalent to the Freakel criterion and is obtained from the zeroth order approximation of the H-3 term in the evolution equation. This criterion is determined solely by the film radius, interfacial tension and Hamaker constant. The lower bound is obtained from the first order approximation of the H-3 term in the evolution equation and is dependent on the film thinning velocity A semi-empirical equation, referred to as the MTR equation, is obtained by combining the drainage theory of Manev et al. [J. Dispersion Sci. Technol., 18 (1997) 769] and the experimental measurements of Radoev et al. [J. Colloid Interface Sci. 95 (1983) 254] and is shown to provide accurate predictions of film thinning velocity near the critical thickness of rupture. The MTR equation permits the prediction of the lower bound of the maximum transition thickness based entirely on film radius, Plateau border radius, interfacial tension, temperature and Hamaker constant. The MTR equation extrapolates to Reynolds equation under conditions when the Plateau border pressure is small, which provides a lower bound for the maximum transition thickness that is equivalent to the criterion of Gumerman and Homsy [Chem. Eng. Commun. 2 (1975) 27]. The relative accuracy of either bound is thought to be dependent on the amplitude of the hydrodynamic corrugations, and a semiempirical correlation is also obtained that permits the amplitude to be calculated as a function of the upper and lower bound of the maximum transition thickness. The relationship between the evolving theoretical developments is demonstrated by three film thickness master curves, which reduce to simple analytical expressions under limiting conditions when the drainage pressure drop is controlled by either the Plateau border capillary pressure or the van der Waals disjoining pressure. The master curves simplify solution of the various theoretical predictions enormously over the entire range of the linear approximation. Finally, it is shown that when the Frenkel criterion is used to assess film stability, recent studies reach conclusions that are contrary to the relevance of spontaneous rupture as a cell-opening mechanism in foams. (C) 2003 Elsevier Science B.V. All rights reserved.

Phase equilibria and surface tension of pure fluids using a molecular layer structure theory (MLST) model

This paper presents a new model based on thermodynamic and molecular interaction between molecules to describe the vapour-liquid phase equilibria and surface tension of pure component. The model assumes that the bulk fluid can be characterised as set of parallel layers. Because of this molecular structure, we coin the model as the molecular layer structure theory (MLST). Each layer has two energetic components. One is the interaction energy of one molecule of that layer with all surrounding layers. The other component is the intra-layer Helmholtz free energy, which accounts for the internal energy and the entropy of that layer. The equilibrium between two separating phases is derived from the minimum of the grand potential, and the surface tension is calculated as the excess of the Helmholtz energy of the system. We test this model with a number of components, argon, krypton, ethane, n-butane, iso-butane, ethylene and sulphur hexafluoride, and the results are very satisfactory. (C) 2002 Elsevier Science B.V. All rights reserved.

Solubility of selected esters in supercritical carbon dioxide

The solubility of ethyl propionate, ethyl butyrate, and ethyl isovalerate in supercritical carbon dioxide was measured at temperature ranging from 308.15 to 333.15 K and pressure ranging from 85 to 195 bar. At the same temperature, the solubility of these compounds increases with pressure. The crossover pressure region was also observed in this study. The experimental data were correlated by the semi-empirical Chrastil equation and Peng-Robinson equation of state (EOS) using several mixing rules. The Peng-Robinson EOS gives better solubility prediction than the empirical Chrastil equation. (C) 2002 Elsevier Science B.V. All rights reserved.

Nossa V??rzea: cidadania e sustentabilidade na Amaz??nia brasileira

Em um novo modelo de gest??o compartilhada da Secretaria do Patrim??nio da Uni??o, a iniciativa faz parte do projeto Nossa V??rzea ??? regulariza????o fundi??ria em ??reas de v??rzeas ??? e est?? sendo desenvolvida pela SPU, por meio da Ger??ncia da Secretaria do Patrim??nio da Uni??o do Estado do Par?? (GRPU/PA). Tem como objetivo promover a regulariza????o fundi??ria de ocupa????es em terras p??blicas utilizando o Termo de Autoriza????o de Uso ??? instrumento legal inovador, que constitui o fundamento expressivo da a????o. Ao entregar o Termo ??s fam??lias de comunidades ribeirinhas, a Uni??o reconhece o direito ?? ocupa????o e possibilita a explora????o sustent??vel das ??reas de v??rzeas. Al??m disso, o instrumento representa para a fam??lia beneficiada um comprovante oficial de resid??ncia e uma garantia de acesso a aposentadoria, a recursos do Programa Nacional de Fortalecimento da Agricultura Familiar (Pronaf) e a outros programas sociais do Governo Federal. Desde a implanta????o do Programa, j?? foram beneficiadas cerca de 6.000 fam??lias ribeirinhas, principalmente as que residem no arquip??lago do Maraj??

A hist??ria de dois contratos: como minimizar o risco de se estabelecer um contrato com v??nculo empregat??cio no processo de adquirir bens, contratar servi??os ou implementar um projeto de constru????o

O caso trata da contrata????o de George, pesquisador que prestava servi??os a um ??rg??o p??blico canadense e que, ap??s sofrer um acidente de trabalho, foi informado de que n??o tinha direito ?? cobertura do plano de sa??de dispon??vel aos servidores. Devido ?? precariedade do contrato no qual eram estabelecidas as condi????es da rela????o de trabalho, e de ter sido comprovado que o pesquisador era tratado tal como funcion??rio do minist??rio, George teve direito aos benef??cios a que fazia jus e o ??rg??o foi multado por n??o ter recolhido os valores referentes ?? rela????o trabalhista. Essa situa????o ilustra um breve debate sobre como estabelecer bons contratos com prestadores de servi??o, em especial no que tange a contrata????es de servi??os t??cnicos especializados

Cheques indevidos: corrigindo um erro de v??rios milh??es de d??lares

O caso trata das dificuldades de tomada de decis??o por parte de uma autoridade federal ao serem constatados erros no repasse de subs??dios para agricultores em um programa governamental. O texto relata o conflito entre as posi????es da auditoria e da ??rea t??cnica a respeito das a????es a serem desenvolvidas; a primeira, considerando a quest??o sob o ponto de vista legal e do interesse p??blico, e a segunda, priorizando o interesse dos agricultores e os impactos pol??ticos de uma decis??o contr??ria ?? categoria. O caso tem sido usado em cursos para subsidiar discuss??es sobre ??tica, accountability, conflito de interesses e gest??o de erros n??o previstos

Caf?? com debate: como os dados abertos v??o transformar as pr??ticas do governo e gerar oportunidades para a sociedade

A Escola Nacional de Administra????o P??blica realizou o segundo Caf?? com Debate de 2012 no dia 4 de maio. O tema dessa edi????o foi "Como os dados abertos v??o transformar as pr??ticas do governo e gerar oportunidades para a sociedade". Transmitido em tempo real, o evento foi acompanhado por mais de 800 internautas, entre as 08h30 e as 10h30, e reuniu por volta de 300 pessoas - representando aproximadamente 80 institui????es do governo e da sociedade civil - no audit??rio da ENAP

V??deo institucional ENAP: 1997

V??deo institucional sobre objetivos e atua????o da ENAP

Idades e crescimento da cioba, Ocyururs chrysurus, da Costa Central do Brasil

A idade e o crescimento da cioba da costa central do Brasil foram estudados a partir de leituras de otólitos obtidos em amostragens mensais de desembarques comerciais, realizados nas cidades de Vitória e Vila Velha, entre os anos de 1998 e 1999. Através da análise do incremento marginal, foi verificada a formação anual de uma zona translúcida a partir do final do outono e durante o inverno. Foram observadas ciobas de 2 a 19 anos. Os comprimentos furcais (CF) médios retrocalculados variaram de 108 mm para idade 1 a 524 mm para idade 19. A equação de Von Bertalanffy ajustada aos CF médios retrocalculados foi CFt = 567,1 (1 - e -0.130 (t + 0.773)). A relação comprimento peso foi P = 2,68x10-5CF2.914, onde P = peso total em gramas. O crescimento é lento, com os incrementos anuais em peso aumentando gradativamente até atingir o máximo de 164 g entre as idades 7 e 8 anos. Os resultados deste trabalho indicam que a cioba tem longa expectativa de vida e baixas taxas de crescimento somático, características das espécies mais sensíveis à exploração pesqueira.