685 research outputs found

    Equation of state of charged colloidal suspensions and its dependence on the thermodynamic route

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    The thermodynamic properties of highly charged colloidal suspensions in contact with a salt reservoir are investigated in the framework of the Renormalized Jellium Model (RJM). It is found that the equation of state is very sensitive to the particular thermodynamic route used to obtain it. Specifically, the osmotic pressure calculated within the RJM using the contact value theorem can be very different from the pressure calculated using the Kirkwood-Buff fluctuation relations. On the other hand, Monte Carlo (MC) simulations show that both the effective pair potentials and the correlation functions are accurately predicted by the RJM. It is suggested that the lack of self-consistency in the thermodynamics of the RJM is a result of neglected electrostatic correlations between the counterions and coions

    Ionic size effects on the Poisson-Boltzmann theory

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    In this paper, we develop a simple theory to study the effects of ionic size on ionic distributions around a charged spherical particle. We include a correction to the regular Poisson-Boltzmann equation in order to take into account the size of ions in a mean-field regime. The results are compared with Monte Carlo simulations and a density functional theory based on the fundamental measure approach and a second-order bulk expansion which accounts for electrostatic correlations. The agreement is very good even for multivalent ions. Our results show that the theory can be applied with very good accuracy in the description of ions with highly effective ionic radii and low concentration, interacting with a colloid or a nanoparticle in an electrolyte solution

    Severe Obesity Shifts Metabolic Thresholds but Does Not Attenuate Aerobic Training Adaptations in Zucker Rats

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    Severe obesity affects metabolism with potential to influence the lactate and glycemic response to different exercise intensities in untrained and trained rats. Here we evaluated metabolic thresholds and maximal aerobic capacity in rats with severe obesity and lean counterparts at pre- and post-training. Zucker rats (obese: n = 10, lean: n = 10) were submitted to constant treadmill bouts, to determine the maximal lactate steady state, and an incremental treadmill test, to determine the lactate threshold, glycemic threshold and maximal velocity at pre and post 8 weeks of treadmill training. Velocities of the lactate threshold and glycemic threshold agreed with the maximal lactate steady state velocity on most comparisons. The maximal lactate steady state velocity occurred at higher percentage of the maximal velocity in Zucker rats at pre-training than the percentage commonly reported and used for training prescription for other rat strains (i.e., 60%) (obese = 78 +/- 9% and lean = 68 +/- 5%, P 0.05), whereas increase in maximal velocity was greater in the obese group (P < 0.05 vs. lean). In conclusion, lactate threshold, glycemic threshold and maximal lactate steady state occurred at similar exercise intensity in Zucker rats at pre- and post-training. Severe obesity shifted metabolic thresholds to higher exercise intensity at pre-training, but did not attenuate submaximal and maximal aerobic training adaptations.Coordination for the Improvement of Higher Education Personnel (CAPES)Univ Fed Sao Paulo, Grad Program Translat Med, Sao Paulo, BrazilUniv Catolica Brasilia, Grad Program Phys Educ & Hlth, Brasilia, DF, BrazilUniv Sao Paulo, Sch Publ Hlth, Dept Nutr, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Nephrol, Sao Paulo, BrazilSao Paulo State Univ, Dept Phys Educ, Human Performance Lab, Rio Claro, BrazilUniv Fed Sao Paulo, Dept Physiol, Sao Paulo, BrazilUniv Fed Sao Paulo, Grad Program Translat Med, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Nephrol, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Physiol, Sao Paulo, BrazilWeb of Scienc

    Theory and modeling of molecular modes in the NMR relaxation of fluids

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    Traditional theories of the NMR autocorrelation function for intramolecular dipole pairs assume single-exponential decay, yet the calculated autocorrelation of realistic systems display a rich, multi-exponential behavior resulting in anomalous NMR relaxation dispersion (i.e., frequency dependence). We develop an approach to model and interpret the multi-exponential autocorrelation using simple, physical models within a rigorous statistical mechanical development that encompasses both rotational and translational diffusion in the same framework. We recast the problem of evaluating the autocorrelation in terms of averaging over a diffusion propagator whose evolution is described by a Fokker-Planck equation. The time-independent part admits an eigenfunction expansion, allowing us to write the propagator as a sum over modes. Each mode has a spatial part that depends on the specified eigenfunction, and a temporal part that depends on the corresponding eigenvalue (i.e., correlation time) with a simple, exponential decay. The spatial part is a probability distribution of the dipole-pair, analogous to the stationary states of a quantum harmonic oscillator. Drawing inspiration from the idea of inherent structures in liquids, we interpret each of the spatial contributions as a specific molecular mode. These modes can be used to model and predict NMR dipole-dipole relaxation dispersion of fluids by incorporating phenomena on the molecular level. We validate our statistical mechanical description of the distribution in molecular modes with molecular dynamics simulations interpreted without any relaxation models or adjustable parameters: the most important poles in the Pad{\'e}-Laplace transform of the simulated autocorrelation agree with the eigenvalues predicted by the theory

    O PERFIL DO IDOSO NO ENTORNO DO INSTITUTO FEDERAL DE EDUCAÇÃO, CIÊNCIA E TECNOLOGIA DO RIO DE JANEIRO

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    Trata-se de uma pesquisa de campo, dos acadêmicos de Terapia ocupacional e fisioterapia , visando conhecer o perfil do idoso da Região oeste. Utilizamos um questionário com 34 questões abertas e fechadas. Utilizamos o epi info para analise dos dados estatísticos. Identificamos que a maioria dos idosos desta região são mulheres, católicas,com renda familiar entre 1 a 3 salários mínimos, aposentadas, não realizam atividade física e possuem ensino básico. Concluímos que ainda se faz necessário orientação sobre os  direitos da pessoa idosa e do sistema único de saúd

    Structural and functional evidence for membrane docking and disruption sites on phospholipase A2-like proteins revealed by complexation with the inhibitor suramin

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    Local myonecrosis resulting from snakebite envenomation is not efficiently neutralized by regular antivenom administration. This limitation is considered to be a significant health problem by the World Health Organization. Phospholipase A2-like (PLA2-like) proteins are among the most important proteins related to the muscle damage resulting from several snake venoms. However, despite their conserved tertiary structure compared with PLA2s, their biological mechanism remains incompletely understood. Different oligomeric conformations and binding sites have been identified or proposed, leading to contradictory data in the literature. In the last few years, a comprehensive hypothesis has been proposed based on fatty-acid binding, allosteric changes and the presence of two different interaction sites. In the present study, a combination of techniques were used to fully understand the structural-functional characteristics of the interaction between suramin and MjTX-II (a PLA2-like toxin). In vitro neuromuscular studies were performed to characterize the biological effects of the protein-ligand interaction and demonstrated that suramin neutralizes the myotoxic activity of MjTX-II. The high-resolution structure of the complex identified the toxin-ligand interaction sites. Calorimetric assays showed two different binding events between the protein and the inhibitor. It is demonstrated for the first time that the inhibitor binds to the surface of the toxin, obstructing the sites involved in membrane docking and disruption according to the proposed myotoxic mechanism. Furthermore, higher-order oligomeric formation by interaction with interfacial suramins was observed, which may also aid the inhibitory process. These results further substantiate the current myotoxic mechanism and shed light on the search for efficient inhibitors of the local myonecrosis phenomenon.Peer Reviewe

    O PERFIL DO IDOSO NO ENTORNO DO INSTITUTO FEDERAL DE EDUCAÇÃO, CIÊNCIA E TECNOLOGIA DO RIO DE JANEIRO

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    Trata-se de uma pesquisa de campo, dos acadêmicos de Terapia ocupacional e fisioterapia , visando conhecer o perfil do idoso da Região oeste. Utilizamos um questionário com 34 questões abertas e fechadas. Utilizamos o epi info para analise dos dados estatísticos. Identificamos que a maioria dos idosos desta região são mulheres, católicas,com renda familiar entre 1 a 3 salários mínimos, aposentadas, não realizam atividade física e possuem ensino básico. Concluímos que ainda se faz necessário orientação sobre os  direitos da pessoa idosa e do sistema único de saúd

    A avaliação econômica do suprimento de gás de folhelho para a ute Uruguaiana / The economic evaluation of the shale gas supply to the Uruguaiana thermoelectric power plant

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    O presente trabalho tem como objetivo avaliar a viabilidade econômica, do uso de recursos não convencionais nacionais, tais como gás de folhelho advindos da Bacia do Paraná pela usina termelétrica de Uruguaiana localizada no Rio Grande do Sul. Esta usina foi a primeira térmica operada a gás natural no Brasil, iniciando suas atividades em 2000, mas está paralisada desde abril de 2009. Este trabalho expõe o potencial real de hidrocarbonetos da Bacia do Paraná. Os resultados indicam que o valor presente da demanda de gás natural (em função da utilização da UTE) pode chegar a um valor de USD 16,21 MMBTU para garantir um retorno hipotético de 5% do investimento. A partir dos resultados obtidos, chega-se à conclusão de que a alternativa não convencional para o projeto não é economicamente mais viável na data do estudo do que a importação de GNL, porém é preciso levar em consideração que todos os projetos e investimentos feitos na área do petróleo e gás estão sujeitos a riscos, e à mercê das flutuabilidades desta commodity, que foi evidenciada pela pandemia do COVID19
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