Testing lorentz and CPT invariance with ultracold neutrons

In this paper we investigate, within the standard model extension framework, the influence of Lorentz- and CPT-violating terms on gravitational quantum states of ultracold neutrons. Using a semiclassical wave packet, we derive the effective nonrelativistic Hamiltonian which describes the neutrons vertical motion by averaging the contributions from the perpendicular coordinates to the free falling axis. We compute the physical implications of the Lorentz- and CPT-violating terms on the spectra. The comparison of our results with those obtained in the GRANIT experiment leads to an upper bound for the symmetries-violation c(mu nu)(n) coefficients. We find that ultracold neutrons are sensitive to the a(i)(n) and e(i)(n) coefficients, which thus far are unbounded by experiments in the neutron sector. We propose two additional problems involving ultracold neutrons which could be relevant for improving our current bounds; namely, gravity-resonance spectroscopy and neutron whispering gallery wave.CONACyT [234745, 234774

On the reduction of 4-oxo-4h-benzopyran-3-carbaldehydes : global and local electrophilicity patterns

The theoretical global and local electrophilicity patterns of substituted and chelated 4-oxo-4H-benzopyran-3-carbaldehydes (formylchromones) have been evaluated using the electrophilicity index proposed by Parr et al [J. Am. Chem. Soc. 1999, 121, 1922]. The complexation of formylchromones with aluminum predicts a strong electrophilic character of these compounds against nucleophiles. Local response at the active sites may also be assessed in terms of a global contribution described by the global electrophilicity, and a local contribution described by the variations in electrophilic Fukui function at those sites. The highest local electrophilicity is found at the formyl group of the chelated formylchromones, in spite of that, the highest positive charge is located on the pyrone carbonyl group. This result is consistent with the experimental observed reactivity displayed by 4-oxo-4H-benzopyran-3-carbaldehydes in the presence of 2-propanol and alumina

SYNTESIS AND CRYSTALLINE STRUCTURE OF THE EXO-3,6-DIMETHYL-3,6-EPOXI-1,2,3,6-TETRAHYDROPHTLALIMIDE AND ITS N-BROMODECYL ANALOG: TWO THERMALLY LABILE DIELS-ALDER ADDUCTS

Indexación: Web of Science; Scielo.The molecular structure of the exo-3,6-dimethyl-3,6-epoxi-1,2,3,6-tetrahydrophthalimide (1), determined by X-ray diffraction analysis, as well as, its complete spectroscopic characterization and the synthesis and complete spectroscopic characterization of its N-(10-bromodecyl) analog (2) are presented.http://ref.scielo.org/kh5xv

SENSING IMMOBILIZED MOLECULES OF STREPTAVIDIN ON A SILICON SURFACE BY MALDI-TOF MASS SPECTROMETRY AND FLUORESCENCE MICROSCOPY

Indexación: Web of Science; Scielo.A hydrogen-terminated Si (111) surface was modified to form an aminoterminated monolayer for immobilization of streptavidin. Cleavage of an N-(ω-undecylenyl)-phthalimide covered surface using hidrazine yields an amino group-modified surface, which serves as a substrate for the attachment of biotin and subsequently streptavidin. We used surface analytical techniques to characterize the surface and to control the course of functionalization before the immobilization of streptavidin. To confirm the presence of the streptavidin Texas red on the surface two powerful techniques available in a standard biochemical laboratory are used, Fluorescence Microscopy and MALDI-TOF that allow us to detect and determine the immobilized streptavidin. This work provides an avenue for the development of devices in which the exquisite binding specificity of biomolecular recognition is directly coupled to a biosensor. In addition, we have demonstrated that MALDI-TOF and fluorescence microscopy are useful techniques for the characterization of silicon functionalized surfaces.http://ref.scielo.org/gm87c

Streaky 3D Structures in the Boundary Layer

It has been recently shown [Choi, Nature, April 06 - Cossu, PRL, February 06] that 3D streaky structures in the boundary layer can remain laminar longer than the 2D Blasius °ow. The aim of this investigation is to study the possibility of promoting these 3D streaky structures via surface roughness, computing them and evaluat- ing the resulting stabilization using the Reduced Navier Stokes equations (RNS). The RNS are derived from Navier-Stokes making use of the fact that two very di®erent scales are present: one slow (streamwise direc- tion) and two short (spanwise and wall-normal direction). The RNS allows us to perform these 3D computations in a standard PC, without using CPU costly DNS simulations

Computation of nonlinear streaky structures in boundary layer flow

In this work, the Reduced Navier Stokes (RNS) are numerically integrated, and used to calculate nonlinear finite amplitude streaks. These structures are interesting since they can have a stabilizing effect and delay the transition to the turbulent regime. RNS formulation is also used to compute the family of nonlinear intrinsic streaks that emerge from the leading edge in absence of any external perturbation. Finally, this formulation is generalized to include the possibility of having a curved bottom wal

Organic Agriculture Research: shared vision from Latin-Americans farmers

Content Our History, Our Present Our Needs, Our Future Contribution

Solución bidimensional sin malla de la ecuación no lineal de convección-difusión-reacción mediante el método de Interpolación Local Hermítica

A meshless numerical scheme is developed for solving a generic version of the non-linear convection-diffusion-reaction equation in two-dimensional domains. The Local Hermitian Interpolation (LHI) method is employed for the spatial discretization and several strategies are implemented for the solution of the resulting non-linear equation system, among them the Picard iteration, the Newton Raphson method and a truncated version of the Homotopy Analysis Method (HAM). The LHI method is a local collocation strategy in which Radial Basis Functions (RBFs) are employed to build the interpolation function. Unlike the original Kansa’s Method, the LHI is applied locally and the boundary and governing equation differential operators are used to obtain the interpolation function, giving a symmetric and non-singular collocation matrix. Analytical and Numerical Jacobian matrices are tested for the Newton-Raphson method and the derivatives of the governing equation with respect to the homotopy parameter are obtained analytically. The numerical scheme is verified by comparing the obtained results to the one-dimensional Burgers’ and two-dimensional Richards’ analytical solutions. The same results are obtained for all the non-linear solvers tested, but better convergence rates are attained with the Newton Raphson method in a double iteration scheme.Se desarrolla un esquema numérico sin malla para resolver una versión genérica de la ecuación no lineal de convección-difusión-reacción en dominios bidimensionales. El método de Interpolación Hermitiana Local (LHI) se emplea para la discretización espacial y se implementan varias estrategias para la solución del sistema de ecuaciones no lineal resultante, entre ellas la iteración Picard, el método Newton Raphson y una versión truncada del Método de Análisis de Homotopía. (JAMÓN). El método LHI es una estrategia de colocación local en la que se utilizan funciones de base radial (RBF) para construir la función de interpolación. A diferencia del método original de Kansa, el LHI se aplica localmente y los operadores diferenciales de ecuación límite y gobernante se utilizan para obtener la función de interpolación, dando una matriz de colocación simétrica y no singular. Las matrices analíticas y numéricas jacobianas se prueban para el método de Newton-Raphson y las derivadas de la ecuación de gobierno con respecto al parámetro de homotopía se obtienen analíticamente. El esquema numérico se verifica comparando los resultados obtenidos con las soluciones analíticas unidimensionales de Burgers y Richards bidimensionales. Se obtienen los mismos resultados para todos los solucionadores no lineales probados, pero se obtienen mejores tasas de convergencia con el método Newton Raphson en un esquema de doble iteración