Quantum decay of metastable states in small magnetic particles

We present an imaginary-time path-integral study of the problem of quantum decay of a metastable state of a uniaxial magnetic particle placed in the magnetic field at an arbitrary angle. Our findings agree with earlier results of Zaslavskii obtained by mapping the spin Hamiltonian onto a particle Hamiltonian. In the limit of low barrier, weak dependence of the decay rate on the angle is found, except for the field which is almost normal to the anisotropy axis, where the rate is sharply peaked, and for the field approaching the parallel orientation, where the rate rapidly goes to zero. This distinct angular dependence, together with the dependence of the rate on the field strength, provides an independent test for macroscopic spin tunneling.

Nonmesonic weak decay of the hypertriton

The nonmesonic decay of the hypertriton is calculated based on a hypertriton wave function and 3N scattering states, which are rigorous solutions of three-body Faddeev equations using realistic NN and hyperon-nucleon interactions. The pion exchange together with heavier meson exchanges for the ¿N¿NN transition is considered. The total nonmesonic decay rate is found to be 0.5% of the free ¿ decay rate. Integrated as well as differential decay rates are given. The p- and n-induced decays are discussed thoroughly and it is shown that the corresponding total rates cannot be measured individually.

Double-autoionization decay of resonantly excited single-electron states

Perturbation theory in the lowest non-vanishing order in interelectron interaction has been applied to the theoretical investigation of double-ionization decays of resonantly excited single-electron states. The formulae for the transition probabilities were derived in the LS coupling scheme, and the orbital angular momentum and spin selection rules were obtained. In addition to the formulae, which are exact in this order, three approximate expressions, which correspond to illustrative model mechanisms of the transition, were derived as limiting cases of the exact ones. Numerical results were obtained for the decay of the resonantly excited Kr 1 3d^{-1}5p[^1P] state which demonstrated quite clearly the important role of the interelectron interaction in double-ionization processes. On the other hand, the results obtained show that low-energy electrons can appear in the photoelectron spectrum below the ionization threshold of the 3d shell. As a function of the photon frequency, the yield of these low-energy electrons is strongly amplified by the resonant transition of the 3d electron to 5p (or to other discrete levels), acting as an intermediate state, when the photon frequency approaches that of the transition.

Two-photon decay of the 1s2s ^1S_0 state in _36Kr^34+ produced by resonant transfer and excitation

The doubly excited 2s2p ^1P_1 level of Kr^{34+} populated via resonant transfer and excitation (RTE) feeds selectively the metastable ls2s ^1 S_0 state which can only decay via simultaneous emission of two photons to the ground state 1s^2 ^1 S_0. X-ray/X-ray coincidence measurements in heavy ionatom collisions enable the direct measurement of the spectral distribution of the two-photon decay in He-like ions. In addition, we observe strong photon cascades indueed by radiative electron capture.

Análisis de polimorfismos genéticos del receptor beta-2 adrenérgico en pacientes pediátricos asmáticos y controles sanos en una muestra de la ciudad de Bogotá

El asma bronquial es una enfermedad inflamatoria crónica, se asocia a hiperrespuesta de la vía aérea, la cual lleva a episodios recurrentes de sibilancias, tos y disnea. La entidad se ha correlacionado con una gran variedad de genes involucrados en su fisiopatología, dentro de los cuales se encuentran genes localizados en el cromosoma 5 (5q23-31), como el del Receptor ß2 Adrenérgico (RB2A). En el presente trabajo se realizó una estimación de las frecuencias de los polimorfismos Arg16Gly, Gln27Glu y Thr164Ile de este receptor, y se estudió la relación existente entre los diferentes polimorfismos y asma, así como su relación con respecto a la severidad de la enfermedad, finalmente se estimó la relación de los haplotipos conformados por estos tres polimorfismos y su asociación con la enfermedad y severidad del fenotipo asmático.

Análisis de polimorfismos del receptor Beta 2 adrenérgico en pacientes colombianos afectados por fibrosis quística

El gen ADRB2 y sus polimorfismos se han asociado al cuadro clínico de los pacientes con Fibrosis Quística. En nuestra población existe asociación de los haplotipos G16E27I164 y R16Q27I164 y la enfermedad, así como la presencia de Pólipos y genotipo E27E y el haplotipo R16E27T164.

Questionmark Perception v5 Beta Program

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Metodologías alfa-mertonianas y beta-childianas en sociología del conocimiento y de la ciencia : un apunte para el siglo XXI.

Resumen del autor

Extension Mathematics Beta.

Este libro cumple las expectativas de los alumnos de matemáticas en relación a los exámenes de secundaria (KS3). Beta está dirigido a estudiantes en los años 8 y 9. Los temas del libro son: los triángulos Isósceles, simplificando fracciones, calculando ángulos, ecuaciones, tipos de triángulos, suma y resta de fracciones, números primos, área y problemas de perímetro con rectángulos, líneas paralelas, multiplicación: integrales y decimales, fracciones y decimales, calculando con medidas, área de triángulos y paralelogramos, simplificando fracciones, números negativos, división: fracciones y decimales.