Abstract This study processed and characterized the biphasic ceramics Na2Ti3O7/Na2Ti6O13 that were obtained from semi-crystalline nanoparticles synthesized using sonochemical methods. Structural characterization techniques, such as X-ray diffraction and Raman spectroscopy, were used to identify the crystalline phases present. The Rietveld refinement revealed, among other structural parameters, the presence of two crystalline phases in compositions of 55.90% and 44.10% for sodium hexatitanate and trititanate, respectively. Via Raman spectroscopy, the presence of the main vibrational modes that correspond to the phases present in biphasic ceramics was confirmed. Finally, by using complex impedance spectroscopy, a decrease in the electrical resistance of both the grain (106 Ω-104 Ω) and its boundary (108 Ω -105 Ω) under increasing temperature was identified.

Resumo Nos últimos anos aumentou o interesse em lidar com o crescente problema ambiental proveniente da poluição de águas residuais oriundas das fábricas industriais. Visando minimizar esse impacto ambiental, a técnica de adsorção em meio aquoso tem sido uma alternativa bastante explorada na atualidade. Portanto, este trabalho teve como objetivo investigar a capacidade adsortiva de microcristais de trióxido de molibdênio (h-MoO3) usando o corante alaranjando de metila (AMe) como molécula em meio aquoso. Os microcristais foram obtidos por micro-ondas hidrotermal e estruturalmente caracterizados por diversas técnicas. O estudo cinético na adsorção do AMe resultou no melhor ajuste quando adotado o modelo de pseudossegunda ordem (R2=0,9997). O estudo da variação de temperatura indicou que a adsorção foi um processo favorável e espontâneo. Os valores obtidos tiveram boa concordância com o modelo de isoterma de Temkin, com capacidade máxima de adsorção de 656,9 mg.g-1 a 318 K.

Abstract In recent years, interest in dealing with the growing environmental problem arising from the pollution of wastewater from industrial factories has increased. In order to minimize this environmental impact, the aqueous adsorption technique has been an alternative widely explored today. Therefore, this study aimed to investigate the adsorptive capacity of molybdenum trioxide (h-MoO3) microcrystals using the methyl orange dye (MO) as a molecule in an aqueous medium. The microcrystals were obtained by hydrothermal microwave and structurally characterized by several techniques. The kinetic study on the adsorption of MO resulted in the best fit when adopting the pseudo-second order model (R2=0.9997). The study of temperature variation indicated that adsorption was a favorable and spontaneous process. The values obtained were in good agreement with the Temkin isotherm model, with a maximum adsorption capacity of 656.9 mg.g-1 at 318 K.

Salt sensitivity and insulin resistance are correlated with higher cardiovascular risk. There is no information about changes in salt sensitivity (SS) and insulin sensitivity (IS) after a chronic salt overload in humans. The aim of this study was to evaluate these parameters in the elderly. Seventeen volunteers aged 70.5 ± 5.9 years followed a low-salt diet (LSD) for 1 week and a high-salt diet (HSD) for 13 weeks. We evaluated SS after one week (HSD1) and after 13 weeks (HSD13), and subjects’ IS and lipids on their usual diet (UD) at HSD1, and at HSD13. Blood pressure (BP) was measured at each visit and ambulatory blood pressure monitoring (ABPM) was performed twice. SS was the same at HSD1 and HSD13. Systolic BP was lower on LSD than on UD (P = 0.01), HSD1 (P < 0.01) and HSD13 (P < 0.01). When systolic and diastolic BP were evaluated by ABPM, they were higher at HSD13 during the 24-h period (P = 0.03 and P < 0.01) and during the wakefulness period (P = 0.02 and P < 0.01) compared to the UD. Total cholesterol was higher (P = 0.04) at HSD13 than at HSD1. Glucose and homeostasis model assessment (HOMA) were lower at HSD1 (P = 0.02 and P = 0.01) than at HSD13. Concluding, the extension of HSD did not change the SS in an elderly group. The higher IS found at HSD1 did not persist after a longer HSD. A chronic HSD increased BP as assessed by ABPM.

The long-range bond-percolation problem, on a linear chain (d = 1), in the presence of diluted sites (with an occupancy probability p s for an active site) is studied by means of a Monte Carlo simulation. The occupancy probability for a bond between two active sites i and j, separated by a distance r ij is given by p ij = <img width=32 height=32 id="_x0000_i1026" src="../../img/revistas/bjp/v33n3/a32img01.gif" align=absbottom>, where p represents the usual occupancy probability between nearest-neighbor sites. This model allows one to analyse the competition between long-range bonds (which enhance percolation) and diluted sites (which weaken percolation). By varying the parameter a (a > 0), one may find a crossover between a nonextensive regime and an extensive regime; in particular, the cases a = 0 and a ® ¥ represent, respectively, two well-known limits, namely, the mean-field (infinite-range bonds) and first-neighbor-bond limits. The percolation order parameter, P¥, was investigated numerically for different values of a and p s. Two characteristic values of a were found, which depend on the site-occupancy probability p s, namely, a1(p s) and a2(p s) (a2(p s) > a1(p s) > 0). The parameter P¥ equals unit, "p > 0, for 0 < a < a1(p s) and vanishes, "p < 1, for a > a2(p s). In the interval a1(p s) < a < a2(p s), the parameter P¥ displays a familiar behavior, i.e., 0 for p < p c(a) and finite otherwise. It is shown that both a1(p s) and a2(p s) decrease with the inclusion of diluted sites. For a fixed p s, it is shown that a convenient variable, p* º p*(p, a, N), may be defined in such a way that plots of P¥ versus p* collapse for different sizes and values of a in the nonextensive regime.

A method for obtaining critical properties of physical systems is presented. Based on a recursive relation involving a physical parameter of the system, it drives the system spontaneously to the critical point, providing an efficient way to estimate critical properties. The method is illustrated for several ferromagnetic Ising systems on well-known Bravais lattices. A finite-size scaling approach is performed, by applying the method on lattices of different sizes. The efficiency of the method is confirmed by evaluating critical temperatures, as well as critical exponents, that turn up to be in good agreement with those available in the literature, with a relatively small computational effort.