MODELLING OF HIGH-PRESSURE PHASE EQUILIBRIUM IN SYSTEMS OF INTEREST IN THE FOOD ENGINEERING FIELD USING THE PENG-ROBINSON EQUATION OF STATE WITH TWO DIFFERENT MIXING RULES

In this work, thermodynamic models for fitting the phase equilibrium of binary systems were applied, aiming to predict the high pressure phase equilibrium of multicomponent systems of interest in the food engineering field, comparing the results generated by the models with new experimental data and with those from the literature. Two mixing rules were used with the Peng-Robinson equation of state, one with the mixing rule of van der Waals and the other with the composition-dependent mixing rule of Mathias et al. The systems chosen are of fundamental importance in food industries, such as the binary systems CO(2)-limonene, CO(2)-citral and CO(2)-linalool, and the ternary systems CO(2)-Limonene-Citral and CO(2)-Limonene-Linalool, where high pressure phase equilibrium knowledge is important to extract and fractionate citrus fruit essential oils. For the CO(2)-limonene system, some experimental data were also measured in this work. The results showed the high capability of the model using the composition-dependent mixing rule to model the phase equilibrium behavior of these systems.

Epidemiologia do Padrão Face Longa em escolares do Ensino Fundamental do município de Bauru - SP

OBJETIVO: o objetivo deste trabalho foi classificar e determinar a prevalência dos indivíduos portadores de comprometimento vertical nas relações faciais, conforme a severidade da discrepância e, especialmente, dos portadores de Padrão Face Longa. MÉTODOS: a amostra constou de 5.020 sujeitos de nacionalidade brasileira, de ambos os sexos, com idades entre 10 anos e 16 anos e 11 meses, matriculados no Ensino Fundamental do município de Bauru-SP. O exame da morfologia facial constou da observação direta da face, em normas frontal e lateral, sempre com os lábios em repouso, buscando identificar aqueles indivíduos que apresentassem comprometimento vertical nas relações faciais. Esses, uma vez identificados, foram classificados, considerando-se a severidade, em três subtipos: moderado, médio e grave. Para fins de determinação da prevalência dos portadores de Padrão Face Longa, apenas os classificados como dos subtipos médio e grave foram considerados. RESULTADOS: observou-se uma prevalência de 34,94% de comprometimento vertical nas relações faciais e 14,06% de Padrão Face Longa. CONCLUSÃO: os resultados obtidos no presente estudo permitiram concluir que a prevalência do comprometimento vertical nas relações faciais e do Padrão Face Longa foi maior do que a presumida com base na literatura.

Shelf-life of a 2.5% sodium hypochlorite solution as determined by arrhenius equation

Accelerated stability tests are indicated to assess, within a short time, the degree of chemical degradation that may affect an active substance, either alone or in a formula, under normal storage conditions. This method is based on increased stress conditions to accelerate the rate of chemical degradation. Based on the equation of the straight line obtained as a function of the reaction order (at 50 and 70 ºC) and using Arrhenius equation, the speed of the reaction was calculated for the temperature of 20 ºC (normal storage conditions). This model of accelerated stability test makes it possible to predict the chemical stability of any active substance at any given moment, as long as the method to quantify the chemical substance is available. As an example of the applicability of Arrhenius equation in accelerated stability tests, a 2.5% sodium hypochlorite solution was analyzed due to its chemical instability. Iodometric titration was used to quantify free residual chlorine in the solutions. Based on data obtained keeping this solution at 50 and 70 ºC, using Arrhenius equation and considering 2.0% of free residual chlorine as the minimum acceptable threshold, the shelf-life was equal to 166 days at 20 ºC. This model, however, makes it possible to calculate shelf-life at any other given temperature.

Comparison of some theoretical models for fittings of the temperature dependence of the fundamental energy gap in GaAs

In this work we report on a comparison of some theoretical models usually used to fit the dependence on temperature of the fundamental energy gap of semiconductor materials. We used in our investigations the theoretical models of Viña, Pässler-p and Pässler-ρ to fit several sets of experimental data, available in the literature for the energy gap of GaAs in the temperature range from 12 to 974 K. Performing several fittings for different values of the upper limit of the analyzed temperature range (Tmax), we were able to follow in a systematic way the evolution of the fitting parameters up to the limit of high temperatures and make a comparison between the zero-point values obtained from the different models by extrapolating the linear dependence of the gaps at high T to T = 0 K and that determined by the dependence of the gap on isotope mass. Using experimental data measured by absorption spectroscopy, we observed the non-linear behavior of Eg(T) of GaAs for T > ΘD.

Modos de resolução de labirintos por alunos da escola fundamental

Saber planejar expressa uma forma de antecipação com pré-correção de erros e uso de inferências. Esta questão foi aqui analisada em 60 matrizes de labirintos (20 A, 20 B e 20 C), resolvidas por 20 alunos da Escola Fundamental, entre 7 e 11 anos. Deste total, 31 matrizes foram resolvidas com um único traçado. As 29 restantes foram analisadas, considerando-se, dentre outros, procedimentos indicadores de planejamento: (1) começar do final, (2) aproveitar o traçado anterior e (3) interromper o traçado. O procedimento (1) foi utilizado pelos sujeitos em 7 matrizes; o procedimento (2) em 9; e o procedimento (3) em 5. Na discussão, apoiada em estudos comparáveis realizados por Piaget, destacaram-se três níveis de resolução das matrizes utilizadas. E, nas considerações finais, foram descritas algumas formas de intervenção, visando favorecer, em um contexto educacional, o desenvolvimento da habilidade de antecipação em crianças.

Análise de atitudes de professoras do ensino fundamental no que se refere à educação inclusiva

Este artigo, que tem como referência a teoria crítica, relata o resultado de uma pesquisa sobre atitudes em relação à educação inclusiva, realizada com doze professoras do 5º ano do ensino fundamental; dentre elas, seis tinham experiência de ter em sala de aula alunos com deficiência, e seis não tinham. A análise qualitativa dos dados decorrentes do levantamento realizado em seis escolas da rede municipal de Campo Grande (MS) demonstrou que, de modo geral, as professoras foram favoráveis à educação inclusiva. Contudo, ficou evidente a expressão de atitudes preconceituosas veladas ou explícitas no âmbito escolar. A formação para experiência com quem é "diferente" ainda encontra barreiras por conta do preconceito e da discriminação presentes nesta sociedade que tem como lógica uma "inclusão marginal". Em suas manifestações, apontaram dificuldades de trabalhar com alunos com deficiência intelectual severa; assinalaram que a responsabilidade de trabalhar sob a predominância da educação centrada no desempenho, com foco na inserção das pessoas no mercado de trabalho, gerava um "sentimento de impotência". Diante das contradições existentes, a educação inclusiva não deixa de evidenciar a presença das injustiças que ainda se apresentam no processo educativo. Apesar disso, foram indicados vários elementos favoráveis a essa forma de educação, que não é dissociada de movimentos sociais mais amplos.

Programa de Controle da Doença de Chagas no Estado de São Paulo: aspectos sorológicos e entomológicos de inquéritos entre escolares de ensino fundamental

Como parte de avaliação de medidas de controle de vetores, levadas a efeito no Estado de São Paulo, na década de 60, inquéritos sorológicos entre crianças escolares nascidas após sua aplicação foram realizados nos períodos abrangidos entre os anos 1968 e 1970, em todos os municípios do estado, à exceção dos da Grande São Paulo e, anualmente, de 1973 a 1983, em amostra selecionada a partir daqueles com as maiores soroprevalências para a infecção chagásica. No primeiro caso, a metodologia sorológica previu os exames à base da reação de fixação de complemento, em soros e, no segundo, a reação de imunofluorescência indireta, em eluatos de sangue total absorvido em papel-filtro. Presença de triatomíneos e sua condição de infecção por Trypanosoma cruzi, coligidas nos diversos municípios de acordo com o ano dos nascimentos dos escolares e da realização dos inquéritos, permitiram vislumbrar o quadro da infecção chagásica no Estado de São Paulo, naquelas épocas. A região de Sorocaba destacou-se das demais em termos sorológicos, sustentada pela presença do Triatoma infestans até o início da década de 70. Similarmente, a autoctonia dos casos foi aí observada de maneira preponderante, enquanto que em outras regiões do estado manteve-se um equilíbrio entre casos autóctones e importados. A análise dos dados revela que, ainda em 1974, a transmissão vetorial poderia registrar-se no estado. É importante destacar que, mesmo com falhas de cobertura, até o ano de 1997, não se observou mais sororreatividade para infecção chagásica nas idades inferiores a 15 anos, no Programa de Controle do Estado de São Paulo.

Existence Results for Abstract Partial Neutral Integro-differential Equation with Unbounded Delay

In this paper we study the existence and regularity of mild solutions for a class of abstract partial neutral integro-differential equations with unbounded delay.

The qWR star HD 45166 - II. Fundamental stellar parameters and evidence of a latitude-dependent wind

Context. The enigmatic object HD 45166 is a qWR star in a binary system with an orbital period of 1.596 day, and presents a rich emission-line spectrum in addition to absorption lines from the companion star (B7 V). As the system inclination is very small (i = 0.77 degrees +/- 0.09 degrees), HD 45166 is an ideal laboratory for wind-structure studies. Aims. The goal of the present paper is to determine the fundamental stellar and wind parameters of the qWR star. Methods. A radiative transfer model for the wind and photosphere of the qWR star was calculated using the non-LTE code CMFGEN. The wind asymmetry was also analyzed using a recently-developed version of CMFGEN to compute the emerging spectrum in two-dimensional geometry. The temporal-variance spectrum (TVS) was calculated to study the line-profile variations. Results. Abundances and stellar and wind parameters of the qWR star were obtained. The qWR star has an effective temperature of T(eff) = 50 000 +/- 2000 K, a luminosity of log(L/L(circle dot)) = 3.75 +/- 0.08, and a corresponding photospheric radius of R(phot) = 1.00 R(circle dot). The star is helium-rich (N(H)/N(He) = 2.0), while the CNO abundances are anomalous when compared either to solar values, to planetary nebulae, or to WR stars. The mass-loss rate is. M = 2.2 x 10(-7) M(circle dot) yr(-1), and the wind terminal velocity is v(infinity) = 425 km s(-1). The comparison between the observed line profiles and models computed under different latitude-dependent wind densities strongly suggests the presence of an oblate wind density enhancement, with a density contrast of at least 8: 1 from equator to pole. If a high velocity polar wind is present (similar to 1200 km s(-1)), the minimum density contrast is reduced to 4:1. Conclusions. The wind parameters determined are unusual when compared to O-type stars or to typical WR stars. While for WR stars v(infinity)/v(esc) > 1.5, in the case of HD 45166 it is much smaller (v(infinity)/v(esc) = 0.32). In addition, the efficiency of momentum transfer is eta = 0.74, which is at least 4 times smaller than in a typical WR. We find evidence for the presence of a wind compression zone, since the equatorial wind density is significantly higher than the polar wind. The TVS supports the presence of such a latitude-dependent wind and a variable absorption/scattering gas near the equator.

Equation of state for the magnetic-color-flavor-locked phase and its implications for compact star models

Using the solutions of the gap equations of the magnetic-color-flavor-locked (MCFL) phase of paired quark matter in a magnetic field, and taking into consideration the separation between the longitudinal and transverse pressures due to the field-induced breaking of the spatial rotational symmetry, the equation of state of the MCFL phase is self-consistently determined. This result is then used to investigate the possibility of absolute stability, which turns out to require a field-dependent ""bag constant"" to hold. That is, only if the bag constant varies with the magnetic field, there exists a window in the magnetic field vs bag constant plane for absolute stability of strange matter. Implications for stellar models of magnetized (self-bound) strange stars and hybrid (MCFL core) stars are calculated and discussed.

Two-dimensional supersonic nonlinear Schrodinger flow past an extended obstacle

Supersonic flow of a superfluid past a slender impenetrable macroscopic obstacle is studied in the framework of the two-dimensional (2D) defocusing nonlinear Schroumldinger (NLS) equation. This problem is of fundamental importance as a dispersive analog of the corresponding classical gas-dynamics problem. Assuming the oncoming flow speed is sufficiently high, we asymptotically reduce the original boundary-value problem for a steady flow past a slender body to the one-dimensional dispersive piston problem described by the nonstationary NLS equation, in which the role of time is played by the stretched x coordinate and the piston motion curve is defined by the spatial body profile. Two steady oblique spatial dispersive shock waves (DSWs) spreading from the pointed ends of the body are generated in both half planes. These are described analytically by constructing appropriate exact solutions of the Whitham modulation equations for the front DSW and by using a generalized Bohr-Sommerfeld quantization rule for the oblique dark soliton fan in the rear DSW. We propose an extension of the traditional modulation description of DSWs to include the linear ""ship-wave"" pattern forming outside the nonlinear modulation region of the front DSW. Our analytic results are supported by direct 2D unsteady numerical simulations and are relevant to recent experiments on Bose-Einstein condensates freely expanding past obstacles.

Entropy production in irreversible systems described by a Fokker-Planck equation

We analyze the irreversibility and the entropy production in nonequilibrium interacting particle systems described by a Fokker-Planck equation by the use of a suitable master equation representation. The irreversible character is provided either by nonconservative forces or by the contact with heat baths at distinct temperatures. The expression for the entropy production is deduced from a general definition, which is related to the probability of a trajectory in phase space and its time reversal, that makes no reference a priori to the dissipated power. Our formalism is applied to calculate the heat conductance in a simple system consisting of two Brownian particles each one in contact to a heat reservoir. We show also the connection between the definition of entropy production rate and the Jarzynski equality.

Looking at the Gregory-Laflamme instability through quasinormal modes

We study evolution of gravitational perturbations of black strings. It is well known that for all wave numbers less than some threshold value, the black string is unstable against the scalar type of gravitational perturbations, which is named the Gregory-Laflamme instability. Using numerical methods, we find the quasinormal modes and time-domain profiles of the black string perturbations in the stable sector and also show the appearance of the Gregory-Laflamme instability in the time domain. The dependence of the black string quasinormal spectrum and late-time tails on such parameters as the wave vector and the number of extra dimensions is discussed. There is numerical evidence that at the threshold point of instability, the static solution of the wave equation is dominant. For wave numbers slightly larger than the threshold value, in the region of stability, we see tiny oscillations with very small damping rate. While, for wave numbers slightly smaller than the threshold value, in the region of the Gregory-Laflamme instability, we observe tiny oscillations with very small growth rate. We also find the level crossing of imaginary part of quasinormal modes between the fundamental mode and the first overtone mode, which accounts for the peculiar time domain profiles.

Equivalence between Redfield- and master-equation approaches for a time-dependent quantum system and coherence control

We present a derivation of the Redfield formalism for treating the dissipative dynamics of a time-dependent quantum system coupled to a classical environment. We compare such a formalism with the master equation approach where the environments are treated quantum mechanically. Focusing on a time-dependent spin-1/2 system we demonstrate the equivalence between both approaches by showing that they lead to the same Bloch equations and, as a consequence, to the same characteristic times T(1) and T(2) (associated with the longitudinal and transverse relaxations, respectively). These characteristic times are shown to be related to the operator-sum representation and the equivalent phenomenological-operator approach. Finally, we present a protocol to circumvent the decoherence processes due to the loss of energy (and thus, associated with T(1)). To this end, we simply associate the time dependence of the quantum system to an easily achieved modulated frequency. A possible implementation of the protocol is also proposed in the context of nuclear magnetic resonance.