Propiedades ópticas lineales y no lineales en pozos cuánticos dobles con alturas de barreras asimétricas en sistemas AlGaN/GaN zincblenda

In this doctoral research thesis we perform the calculation of the absorption coefficient and the relative refractive index change for the linear and its non-linear correction, due to the intense laser effect, for a double quantum well with asymmetry in the barriers. The asymmetric double quantum well is formed by cubic-phase Gallium Nitride (c-GaN) in the wells regions and by Gallium Aluminum Nitride, also in its cubic-phase, in the barriers with an aluminum concentration c-AlxGa1−xN. This heterostructure, due to the difference in its lattice constants, is strained, so in this work we present a comparative study of the optical properties of interest in order to determine the importance of the strain in the system, this was done when implementing the Van der Walle’s Model-Solid Theory. The electronic structure, once considered the effect of the strain on the height of the barriers, is done by means of the diagonalization method, using the solution for a rectangular well of infinite barriers of width L as the base of the expansion, all the computation was performed under the approximation of effective mass and parabolic band. The optical properties are calculated with well-established expressions in the literature in the frame of the formalism of the compact density-matrix.En esta investigación doctoral realizamos el cálculo del coeficiente de absorción y del cambio relativo del índice de refracción lineal y su corrección no lineal, debida al efecto de láser intenso, para un pozo cuántico doble con asimetría en las barreras. El pozo cuántico doble asimétrico está formado por Nitruro de Galio en fase cúbica (c-GaN) en la región de los pozos y por Nitruro de Galio Aluminio, también en su fase cubica, en las barreras con una concentración de aluminio c-AlxGa1−xN. Esta heteroestructura, por la diferencia en sus constantes de red, se encuentra tensionada, así que en este trabajo presentamos un estudio comparativo de las propiedades ópticas de interés con el fin de determinar la importancia de la tensión en el sistema, lo cual se hizo al implementar la Teoría del Sólido Modelo de Van der Walle. La estructura electrónica, una vez considerado el efecto de la tensión en la altura de las barreras, se hace mediante el método de diagonalización usando como base de la expansión la solución al pozo rectangular de barreras infinitas de ancho L, bajo la aproximación de masa efectiva y banda parabólica. Las propiedades ópticas se calculan con expresiones bien establecidas en la literatura que se obtienen mediante el formalismo de la matriz densidad compacta

Antimicrobial Resistance in E. coli Isolated from the Biological Samples in Zacatecas patients

The problem of antimicrobial resistance has led Health Services take to stop population from self-medicating. The use of antibiotics to trigger a possible mutation of the most common bacteria of which the human being has contact, so it is important to evaluate the consequences. The present study was to evaluate the antibacterial sensitivity necessary to determine the antibiotic to be prescribed; were analyzed cultures of 48 patients who already referred symptoms were used between hospital inpatients and outpatients of different sex and age ranges groups. The biological samples were vaginal exudates and urine cultures. The results reports indicate that resistance predominates over sensitivity a fact that must draw attention to taking decisive measures in this regard

Strain effects in the absorption coefficient and relative refractive index change in double asymmetric AlxGa1−xN/GaN quantum wells

We theoretically investigate the optical absorption and the relative change in the index of refraction in asymmetric double zinc-blende AlxGa1−xN/GaN quantum wells. Particular emphasis is put in revealing the influence of lattice strain on these properties. For that purpose, the electronic energy structure is determined in the framework of the effective mass and parabolic band approximations whilst the strain effects are incorporated with the use of the model solid theory. The corresponding optical coefficients are then computed through the expressions obtained within the compact matrix density formulation. Linear and nonlinear contributions are reported as functions of the widths of both the separating central potential barrier and the left-hand quantum well

Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2