Solid‐phase preconcentration and determination of mercury(II) using activated carbon in drinking water by X‐ray fluorescence spectrometry

A novel and simple method was developed for the preconcentration and determination of mercury(II) from hydrochloric acid solutions through their adsorption on Aliquat 336 (tri‐octylmethylammonium chloride)‐activated carbon. The determinations were made directly on the solid by X‐ray fluorescence spectrometry, which had the advantage of eliminating the step of elution of the mercury retained. This preconcentration system enabled the determination of Hg(II) in drinking water samples at µg l^?1 levels. A 1700‐fold enrichment factor was obtained. The described methodology showed excellent reproducibility, accuracy, and detection limits improvement by eliminating the step of elution of the analyte, replacing those methods based on cold vapor generation, reducing reagent consumption, and handling of samples. Copyright © 2013 John Wiley & Sons, Ltd.     

A Solution to Einstein's Equations for the Mixmaster Universe in Complex General Relativity

Starting from Einstein's equations of the Classical General Relativity, new kinds of solutions for the Mixmaster model are explored. By dispensing with the extension to the complex variable field, which is usual in problems such as the Laplace equation or the harmonic oscillator, in a similar manner to that of Quantum Mechanics, the equations appear to have solutions that belong to the complex General Relativity. A first integral is performed by establishing a separation of the first derivatives. Then a second integral is obtained once the respective equations with separate variables are found and whose integrals provide a family of complex solutions. However, reality conditions do not seem to be easily imposed at this stage. Above all, it is significant that the classical Einstein's equations for the debatably integrable Mixmaster model present complex solutions.     

The cohomology of the cotangent bundle of Heisenberg groups

Given a parabolic subalgebra g₁×n of a semisimple Lie algebra, Kostant (Ann. Math. 1963) and Griffiths (Acta Math. 1963) independently computed the g₁ invariants in the cohomology group of n with exterior adjoint coefficients. By a theorem of Bott (Ann. Math. 1957), this is the cohomology of the associated compact homogeneous space with coefficients in the sheaf of local holomorphic forms. In this paper we determine explicitly the full module structure, over the symplectic group, of the cohomology group of the Heisenberg Lie algebra with exterior adjoint coefficients. This is the cohomology of the cotangent bundle of the Heisenberg group.     

Study of germ tube formation by Candida albicans after photodynamic antimicrobial chemotherapy (PACT)

Due to the augmented number of immunocompromised patients, the infections associated to the pathogen of the genus Candida have increased dramatically in the recent years. In order to proliferate, Candida albicans can produce a germ tube formation extending from the cells. The germ tube formation is a transition state from budding to hyphal cells, and represents an essential stage for virulence. In this work we studied the effect of the photodynamic antimicrobial chemotherapy (PACT), a potential antimicrobial treatment on the germ tube formation by C. albicans. Germ tube formation was induced by goat serum after different treatments with Methylene blue (MB) and Laser (683nm). Our results demonstrated that photodynamic therapy using MB, as a photosensitizing drug; inhibits both the growth and the germ tube formation by C. albicans. Thus, our results suggest the possibility that Methylene blue, combined with light in a specific wavelength, can be used as a promising novel antifungal agent.     

Textured macro- and mesoporous alumina samples designed in the presence of different surfactant types

This work presents a method that enables the synthesis of porous alumina in the presence of different types of surfactant. The method is based on a sol–gel transition, using surfactants and droplets of a nonpolar phase as templates. The main purpose was to establish a relationship between the templates and the resulting pore structure. The results show that depending on the type of surfactant used (ionic or nonionic), materials presenting variations in the pore family distribution, X-ray powder diffraction patterns and sample morphology were formed. During the synthesis of these alumina samples, the drying step caused loss of the porous structures, so the shrinkage due to different types of surfactants was evaluated.     

Critical metrics of the total scalar curvature functional on 4‐manifolds

The purpose of this paper is to investigate the critical points of the total scalar curvature functional restricted to space of metrics with constant scalar curvature of unitary volume, for simplicity CPE metrics. It was conjectured in the 1980's that every CPE metric must be Einstein. We prove that a 4‐dimensional CPE metric with harmonic tensor must be isometric to a round sphere