Time evolution of decay of two identical quantum particles

An analytical solution for the time evolution of decay of two identical non interacting quantum particles seated initially within a potential of finite range is derived using the formalism of resonant states. It is shown that the wave function, and hence also the survival and nonescape probabilities, for factorized symmetric and entangled symmetric/antisymmetric initial states evolve in a distinctive form along the exponentially decaying and nonexponential regimes. Our findings show the influence of the Pauli exclusion principle on decay. We exemplify our results by solving exactly the s-wave delta shell potential model.Comment: 14 pages, 3 figures, added references and discussio

Influence of diffractive interactions on cosmic ray air showers

A comparative study of commonly used hadronic collision simulation packages is presented. The characteristics of the products of hadron-nucleus collisions are analyzed from a general perspective, but focusing on their correlation with diffractive processes. One of the purposes of our work is to give quantitative estimations of the impact that different characteristics of the hadronic models have on air shower observables. Several sets of shower simulations using different settings for the parameters controlling the diffractive processes are used to analyze the correlations between diffractivity and shower observables. We find that the relative probability of diffractive processes during the shower development have a non negligible influence over the longitudinal profile as well as the distribution of muons at ground level. The implications on experimental data analysis are discussed.Facultad de Ciencias ExactasInstituto de Física La Plat

New heavenly double copies

The double copy relates scattering amplitudes and classical solutions in Yang-Mills theory, gravity, and related field theories. Previous work has shown that this has an explicit realisation in self-dual YM theory, where the equation of motion can be written in a form that maps directly to Pleba\'nski's heavenly equation for self-dual gravity. The self-dual YM equation involves an area-preserving diffeomorphism algebra, two copies of which appear in the heavenly equation. In this paper, we show that this construction is a special case of a wider family of heavenly-type examples, by (i) performing Moyal deformations, and (ii) replacing the area-preserving diffeomorphisms with a less restricted algebra. As a result, we obtain a double-copy interpretation for hyper-Hermitian manifolds, extending the previously known hyper-K\"ahler case. We also introduce a double-Moyal deformation of the heavenly equation. The examples where the construction of Lax pairs is possible are manifestly consistent with Ward's conjecture, and suggest that the classical integrability of the gravity-type theory may be guaranteed in general by the integrability of at least one of two gauge-theory-type single copies.Comment: 34 pages, 1 figur

Obtención por vía SHS-AE de compuesto cerámico αSiC-αAl2O3-CaAl4O7

El presente trabajo muestra los resultados experimentales de la obtención del compuesto cerámico SiC-Al2O3-CaAl 4O7 mediante el proceso SHS-AE (síntesis auto-sostenida de alta temperatura combinada con arco eléctrico) a partir del sistema vidrio sódico-cálcico-Al-C. Se utilizó horno de arco eléctrico con atmósfera de argón para la reducción del contenido de sílice presente en el vidrio con aluminio.La combinación de la energía de la reacción de formación del Al2O3 con la del arco eléctrico provee suficiente energía térmica para superar las barreras cinéticas asociadas con la reacción de formación de los componentes cerámicos.A partir de las relaciones estequiométricas de las materias primas, (polvos que se compactan en forma de pastilla) se efectúa la síntesis alcanzando una temperatura superior a los 2500 K formándose el compuesto SiC-Al2O3-CaAl 4O7. Las muestras obtenidas se caracterizaron por DRX y MEB-EDX confirmando la obtención simultánea de αSiC-αAl2O3-CaAl4O7

Enzymatic hydrolysis of esters from 2-carboxy-6- methoxy-2,3-dihydrobenzofuran acid

In this work we describe the results of the enzymatic hydrolysis of esters from 2-carboxy-6-methoxy-2,3-dihydrobenzofuran acid using Candida antarctica lipase supported on acrylic resin, with enantiomeric excesses ranging between 80 to 99%

On the radioecological issues of natural radionuclides in water and sediment of a highly contaminated lagoon from Mexico

Se han determinado las concentraciones de actividad de radionucleidos naturales en el agua y los sedimentos de la laguna El Pedernalillo, Zacatecas, México

Lipomas profundos

Se han revisado retrospectivamente 10 lipomas profundos localizados en los miembros. Todos los pacientes fueron intervenidos quirúrgicamente y el diagnóstico de certeza fue histopatológico. Siete de los casos eran lipomas intra o intermusculares y los restantes angiolipoma, hibernoma y fibrolipoma intraneural, respectivamente. El seguimiento medio postoperatorio fue de 48 meses (mínimo: 14, y máximo: 84). No ha habido recidiva en ningún caso.This article is a retrospective review of 10 deep lipomata localized in the limbs. In all the cases the treatment required surgery, and the diagnosis was made by histopathological analysis. Seven cases were intra or intermuscular lipomata, and the other three were angiolipoma, hibernoma and endoneural fibrolipoma. The average postoperative follow-up time was 48 months (14 min-84 max). None showed recurrence at review

Modelos de gestión en nutrición clínica. Puntos débiles y puntos fuertes

En el VIº Foro de Debate Abbott-SENPE se establece una discusión multidisciplinar y multiprofesional para buscar el o los modelos de gestión clínica que consideramos más adecuados para la Unidades de Nutrición Clínica y Dietética (UNCyD) en España. Se valoran los puntos débiles y fuertes así como las oportunidades de los actuales sistemas y se concluye en la observación de una cierta disparidad vinculada no solo a las comunidades autónomas sino también a los diferentes tipos de hospital. Se propone, desde SENPE, la creación de un grupo de trabajo que ayude a la normalización de los modelos y a potenciar la cultura del Cuadro de Mandos Integral y de Gestión del Cambio.At the 6th Abbott-SENPE Debate Forum a multidisciplinary and multiprofessional discussion was established in order to seek for the model or the models of clinical management most appropriate for Clinical Nutrition and Dietetics Units (CNAD) in Spain. The weaknesses and strengths as well as opportunities for the current systems were assessed concluding that a certain degree of disparity was observed not only due to regional differences but also to different hospital types. It was proposed, from SENPE, the creation of a working group helping to standardize the models and promote the culture of Integral Control and Change Management

Surface morphologies of Ti and Ti-Al-V bombarded by 1.0-MeV Au+ Ions

Ion implantation is known to enhance the mechanical properties of biomaterials such as, e.g., the wear resistance of orthopedic joints. Increasing the surface area of implants may likewise improve their integration with, e.g., bone tissue, which requires surface features with sizes in the micron range. Ion implantation of biocompatible metals has recently been demonstrated to induce surface ripples with wavelengths of a few microns. However, the physical mechanisms controlling the formation and characteristics of these patterns are yet to be understood. We bombard Ti and Ti-6Al-4V surfaces with 1.0-MeV Au+ ions. Analysis by scanning electron and atomic force microscopies shows the formation of surface ripples with typical dimensions in the micron range, with potential indeed for biomedical applications. Under the present specific experimental conditions, the ripple properties are seen to strongly depend on the fluence of the implanted ions while being weakly dependent on the target material. Moreover, by examining experiments performed for incidence angle values theta = 8 degrees, 23 degrees, 49 degrees, and 67 degrees, we confirm the existence of a threshold incidence angle for (ripple) pattern formation. Surface indentation is also used to study surface features under additional values of., agreeing with our single-angle experiments.This work was financially supported by Dirección General de Asuntos del Personal Académico-UNAM under Contracts No. Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica IN110116 and No. IN111717, and by CONACYT under Contract No. 222485. L. R. d. l. V. is supported by the Programa de Estancias Sabáticas Nacionales del Consejo Nacional de Ciencia y Tecnología (CONACyT). R. C. acknowledges the kind hospitality and support of the Instituto de Física at UNAM while part of this work was being carried out, as well as partial support from Ministerio de Economía y Competitividad/Fondo Europeo de Desarrollo Regional (Spain/European Union) through Grants No. FIS2012- 38866-C05-01 and No. FIS2015-66020-C2-1-P