5 resultados para Activity coefficient

em Biblioteca Digital da Produção Intelectual da Universidade de São Paulo


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This research reports liquid liquid equilibrium data for the system lard (swine fat), cis-9-octadecenoic acid (oleic acid), ethanol, and water at 318.2 K, as well as their correlation with the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) thermodynamic equations, which have provided global deviations of 0.41 % and 0.53 %, respectively. Additional equilibrium experiments were also performed to obtain cholesterol partition (or distribution) coefficients to verify the availability of the use of ethanol plus water to reduce the cholesterol content in lard. The partition experiments were performed with concentrations of free fatty acids (commercial oleic acid) that varied from (0 to 20) mass % and of water in the solvent that varied from (0 to 18) mass %. The percentage of free fatty acids initially present in lard had a slight effect on the distribution of cholesterol between the phases. Furthermore, the distribution coefficients decreased by adding water in the ethanol; specifically, it resulted in a diminution of the capability of the solvent to remove the cholesterol.

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Submesoscale activity over the Argentinian shelf is investigated by means of high resolution primitive equation numerical solutions. These reveal energetic turbulent activity (visually similar to the one occasionally seen in satellite images) at scales O(5 km) in fall and winter that is linked to mixed layer baroclinic instability. The air-sea heat flux responsible for (i) deepening the upper ocean boundary layer (at these seasons) and (ii) maintaining a cross-shelf background density gradient is the key environmental parameter controlling submesoscale activity. Implications of submesoscale turbulence are investigated. Its mixing efficiency estimated by computing a diffusivity coefficient is above 30 m(2) s(-1) away from the shallowest regions. Aggregation of surface buoyant material by submesoscale currents occurs within hours and is presumably important to the ecosystem.

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Correlations between GABA(A) receptor (GABA(A)-R) activity and molecular organization of synaptosomal membranes (SM) were studied along the protocol for cholesterol (Cho) extraction with beta-cyclodextrin (beta-CD). The mere pre-incubation (PI) at 37A degrees C accompanying the beta-CD treatment was an underlying source of perturbations increasing [H-3]-FNZ maximal binding (70%) and K (d) (38%), plus a stiffening of SMs' hydrocarbon core region. The latter was inferred from an increased compressibility modulus (K) of SM-derived Langmuir films, a blue-shifted DPH fluorescence emission spectrum and the hysteresis in DPH fluorescence anisotropy (A (DPH)) in SMs submitted to a heating-cooling cycle (4-37-4A degrees C) with A (DPH,heating) < A (DPH,cooling). Compared with PI samples, the beta-CD treatment reduced B (max) by 5% which correlated with a 45%-decrement in the relative Cho content of SM, a decrease in K and in the order parameter in the EPR spectrum of a lipid spin probe labeled at C5 (5-SASL), and significantly increased A (TMA-DPH). PI, but not beta-CD treatment, could affect the binding affinity. EPR spectra of 5-SASL complexes with beta-CD-, SM-partitioned, and free in solution showed that, contrary to what is usually assumed, beta-CD is not completely eliminated from the system through centrifugation washings. It was concluded that beta-CD treatment involves effects of at least three different types of events affecting membrane organization: (a) effect of PI on membrane annealing, (b) effect of residual beta-CD on SM organization, and (c) Cho depletion. Consequently, molecular stiffness increases within the membrane core and decreases near the polar head groups, leading to a net increase in GABA(A)-R density, relative to untreated samples.

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Background: Specific research tools and designs can assist in identifying the efficiency of physical activity in elderly women. Objectives: To identify the effects of physical activity on the physical condition of older women. Method: A one-year-long physical activity program (123 sessions) was implemented for women aged 60 years or older. Four physical assessments were conducted, in which weight, height, BMI, blood pressure, heart rate, absences, grip strength, flexibility, VO2max, and static and dynamic balance were assessed. The statistical analyses included a repeated measures analysis, both inferential (analysis of variance - ANOVA) and effect size (Cohen's d coefficient), as well as identification of the participants' efficiency (Data Envelopment Analysis - DEA). Results: Despite the observation of differences that depended on the analysis used, the results were successful in the sense that they showed that physical activity adapted to older women can effectively change the decline in physical ability associated with aging, depending on the purpose of the study. The 60-65 yrs group was the most capable of converting physical activity into health benefits in both the short and long term. The >65 yrs group took less advantage of physical activity. Conclusions: Adherence to the program and actual time spent on each type of exercise are the factors that determine which population can benefit from physical activity programs. The DEA allows the assessment of the results related to time spent on physical activity in terms of health concerns. Article registered in Clinicaltrials.gov under number NCT01558401.

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The mechanisms responsible for containing activity in systems represented by networks are crucial in various phenomena, for example, in diseases such as epilepsy that affect the neuronal networks and for information dissemination in social networks. The first models to account for contained activity included triggering and inhibition processes, but they cannot be applied to social networks where inhibition is clearly absent. A recent model showed that contained activity can be achieved with no need of inhibition processes provided that the network is subdivided into modules (communities). In this paper, we introduce a new concept inspired in the Hebbian theory, through which containment of activity is achieved by incorporating a dynamics based on a decaying activity in a random walk mechanism preferential to the node activity. Upon selecting the decay coefficient within a proper range, we observed sustained activity in all the networks tested, namely, random, Barabasi-Albert and geographical networks. The generality of this finding was confirmed by showing that modularity is no longer needed if the dynamics based on the integrate-and-fire dynamics incorporated the decay factor. Taken together, these results provide a proof of principle that persistent, restrained network activation might occur in the absence of any particular topological structure. This may be the reason why neuronal activity does not spread out to the entire neuronal network, even when no special topological organization exists.