Quantum Brownian Motion. II

This paper generalizes some previous resultspresented in Gaioli et al. [Int. J. Theor. Phys. 36,2167 (1997)]. We evaluate the autocorrelation functionof the stochastic acceleration and study the asymptotic evolution of the mean occupation number of aharmonic oscillator playing the role of a Brownianparticle. We also analyze some deviations from the Bosepopulation at low temperatures and compare it with the deviations from the exponential decay lawof an unstable quantum system.     

Riemannian Superspaces,Exact Solutions and the Geometrical Meaning of the Field Localization

The geometrical origin of a special type of non-degenerate supermetric is elucidated and the connection with processes of topological origin in high energy physics is explained. The new mechanism of the localization of the fields in a particular sector of the supermanifold is explained and the similarity and differences with a 5-dimensional warped model are shown. The relation with gauge theories of supergravity based in the super SL(2,C) group is explicitly given and the possible original action is presented. From the point of view of the vacuum solutions, the simplest Riemannian superspaces are described.     

Trehalose-6-Phosphate as a Potential Lead Candidate for the Development of Tps1 Inhibitors: Insights from the Trehalose Biosynthesis Pathway in Diverse Yeast Species

In some pathogens, trehalose biosynthesis is induced in response to stress as a protection mechanism. This pathway is an attractive target for antimicrobials as neither the enzymes, Tps1, and Tps2, nor is trehalose present in humans. Accumulation of T6P in Candida albicans, achieved by deletion of TPS2, resulted in strong reduction of fungal virulence. In this work, the effect of T6P on Tps1 activity was evaluated. Saccharomyces cerevisiae, C. albicans, and Candida tropicalis were used as experimental models. As expected, a heat stress induced both trehalose accumulation and increased Tps1 activity. However, the addition of 125 μM T6P to extracts obtained from stressed cells totally abolished or reduced in 50 and 60 % the induction of Tps1 activity in S. cerevisiae, C. tropicalis, and C. albicans, respectively. According to our results, T6P is an uncompetitive inhibitor of S. cerevisiae Tps1. This kind of inhibitor is able to decrease the rate of reaction to zero at increased concentrations. Based on the similarities found in sequence and function between Tps1 of S. cerevisiae and some pathogens and on the inhibitory effect of T6P on Tps1 activity observed in vitro, novel drugs can be developed for the treatment of infectious diseases caused by organisms whose infectivity and survival on the host depend on trehalose.     

Optimal Production of a <Emphasis Type="Italic">Rhodococcus erythropolis</Emphasis> ATCC 4277 Biocatalyst for Biodesulfurization and Biodenitrogenation Applications

Rhodococcus sp. has a broad catabolic diversity and unique enzymatic capabilities, and it is able to adapt under extreme conditions. Thereby, the production of this remarkable bacterium has a great biotechnological and industrial importance. In this sense, we sought to improve the R. erythropolis ATCC 4277 growth through a central composite design, by varying the components of nutrient medium (glucose, malt extract, yeast extract, CaCO₃), temperature, and agitation. It was found that the concentrations of glucose and malt extract are not statistically significant, being reduced of 4.0 and 10.0 g L^-1 to 2.0 and 5.0 g L^?1, respectively. The CaCO₃ concentration and temperature were also diminished of 2.0 to 1.16 g L^?1and 28 to 23.7 °C, respectively. Optimal growth conditions provided a 240% increase in final biomass concentration, an increment in specific growth rate, and a growth yield coefficient about five times greater. Application of the optimal conditions in biodesulfurization and biodenitrogenation processes showed that desulfurization capability is not associated with optimal growth conditions; however, it was achieved a 47% of nitrogen removal in the assay containing 10% (w/w) of heavy gas oil.

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Photo-induced pyridine substitution in cis-[Ru(bpy)(2)(py)(2)]Cl(2): a snapshot by time-resolved X-ray solution scattering

Determination of transient structures in light-induced processes is a challenging goal for time-resolved techniques. Such techniques are becoming successful in detecting ultrafast structural changes in molecules and do not require the presence of probe-like groups. Here, we demonstrate that TR-WAXS (Time-Resolved Wide Angle X-ray Scattering) can be successfully employed to study the photochemistry of cis-[Ru(bpy)(2)(py)(2)]Cl(2), a mononuclear ruthenium complex of interest in the field of photoactivatable anticancer agents. TR-WAXS is able to detect the release of a pyridine ligand and the coordination of a solvent molecule on a faster timescale than 800 ns of laser excitation. The direct measurement of the photodissociation of pyridine is a major advance in the field of time-resolved techniques allowing detection, for the first time, of the release of a multiatomic ligand formed by low Z atoms. These data demonstrate that TR-WAXS is a powerful technique for studying rapid ligand substitution processes involving photoactive metal complexes of biological interest.     

Unified Field Theoretical Models from Generalized Affine Geometries III

In this work the underlying structure of new type of Unified Field Theoretical model introduced in by the authors is elucidated and analyzed from the geometrical and group theoretical point of view. Our goal is to take advantage of the geometrical and topological properties of this theory in order to determine the minimal group structure of the resultant spacetime manifold able to support a fermionic structure. From this fact, the relation between antisymmetric torsion and Dirac structure of the spacetime is determined and important physical consequences enumerated. In the case of spacetime with torsion the real meaning of the spin-frame alignment is find and the question of the minimal coupling is discussed based in the important cases of tratorial, totally antisymmetric and general torsion fields.     

Evidence for fast thermalization in the plane-wave matrix model

We report on a numerical simulation of the classical evolution of the plane-wave matrix model with semiclassical initial conditions. Some of these initial conditions thermalize and are dual to a black hole forming from the collision of D-branes in the plane-wave geometry. In particular, we consider a large fuzzy sphere (a D2-brane) plus a single eigenvalue (a D0 particle) going exactly through the center of the fuzzy sphere and aimed to intersect it. Including quantum fluctuations of the off-diagonal modes in the initial conditions, with sufficient kinetic energy the configuration collapses to a small size. We also find evidence for fast thermalization: rapidly decaying autocorrelation functions at late times with respect to the natural time scale of the system.     

Bilinear Sobolev–Poincaré Inequalities and Leibniz-Type Rules

The dual purpose of this article is to establish bilinear Poincaré-type estimates associated with an approximation of the identity and to explore the connections between bilinear pseudo-differential operators and bilinear potential-type operators. The common underlying theme in both topics is their applications to Leibniz-type rules in Sobolev and Campanato–Morrey spaces under Sobolev scaling.     

Fourth order evolution equations which describe pseudospherical surfaces

Differential equations that describe pseudospherical surfaces are considered. These equations are equivalent to the structure equations of a metric with Gaussian curvature K=−1$K=-1$. They can also be described as the compatibility condition of an associated linear problem also referred to as a zero curvature representation. A complete and explicit classification of a class of fourth order evolution equations is given. The classification provides four huge classes (referred to as Types I–IV) of fourth order evolution equations that describe pseudospherical surfaces, together with the associated one (or more) parameter linear problems. The differential equations of each type are determined by choosing certain arbitrary differentiable functions. Fourth-order member of the Burgers hierarchy and a modified Kuramoto–Sivashinsky equation are examples of equations described by Types I and IV, respectively. Many other explicit examples are presented.