ABSTRACT
Self-assembled InN nanocolumns were grown at low temperatures by plasma-assisted molecular beam epitaxy with a high crystalline quality. The self-assembling procedure was carried out on AlN/Al layers on Si(111) substrates avoiding the masking process. The Al interlayer on the Si(111) substrate prevented the formation of amorphous SiN. We found that the growth mechanism at 400 ∘ C of InN nanocolumns started by a layer-layer (2D) nucleation, followed by the growth of 3D islands. This growth mechanism promoted the nanocolumn formation without strain. The nanocolumnar growth proceeded with cylindrical and conical shapes with heights between 250 and 380 nm. Detailed high-resolution transmission electron microscopy analysis showed that the InN nanocolumns have a hexagonal crystalline structure, free of dislocation and other defects. The analysis of the phonon modes also allowed us to identify the hexagonal structure of the nanocolumns. In addition, the photoluminescence spectrum showed an energy transition of 0.72 eV at 20 K for the InN nanocolumns, confirmed by photoreflectance spectroscopy.
ABSTRACT
Introducción: el profesional de enfermería seexpone diariamente con situaciones que pueden sergeneradoras de estrés como lo es la confrontacióncon la muerte, el sufrimiento de las personas, la cargade trabajo y los posibles conflictos con el personalinterdisciplinario. La presente investigación se realizóen el Instituto Nacional de Neurología y NeurocirugíaManuel Velasco Suárez ubicado al sur de la Ciudadde México el cual brinda atención de tercer nivel.Objetivo: identificar el nivel de estrés y los estresoreslaborales a los que están expuestos los enfermeros.Metodología: se realizó un estudio transversal ydescriptivo, la muestra fueron 50 enfermeros adscritosa los servicios de hospitalización los cuales contestaronun instrumento autoaplicacble conformado por 32preguntas cerradas en escala de Lickert.Resultados: el 52% de los enfermeros tiene un nivelde estrés moderado, el 46% tiene un nivel de estrésbajo frente al 2% que tiene un nivel de estrés alto. Lostres agentes estresores con medias más altas fueron enprimer lugar realizar procedimientos dolorosos para elpaciente (X = 1.88), en segundo lugar mirar sufrir a unpaciente y terminar adolorido después de una jornadade trabajo (X = 1.82), el tercer lugar lo ocupa la falta depersonal adecuado para cubrir la unidad (X = 1.7).Conclusiones: en este estudio se logró identificarlos agentes estresores laborales más comunes asícomo el nivel de estrés al que está expuesto el personalde enfermería de las áreas de hospitalización, el cuales producto de las situaciones que viven a diario pararealizar sus intervenciones a favor del paciente esto loexpone a tener un nivel de estrés moderado, lo cualpodría perjudicar su salud, pudiendo provocar unadisminución en el desempeño sobre la calidad de lastareas que se realizan.
Subject(s)
Humans , Stress, PhysiologicalABSTRACT
In the present work, we study the growth by molecular beam epitaxy of InAs self-assembling quantum dots (SAQDs) on GaAs(100) substrates subjected to an in situ annealing treatment. The annealing process consists of the exposition of the GaAs buffer layer surface to high temperatures for a few seconds with the shutter of an arsenic Knudsen cell closed. The purpose of the annealing is to obtain a better uniformity of the SAQD sizes. In our study we prepared different samples using the Stranski-Krastanov growth method to obtain InAs/GaAs(100) quantum dot samples with different annealing times and temperatures. Their structural and optical properties were studied by reflection high-energy electron diffraction (RHEED), high-resolution scanning electron microscopy (HRSEM), atomic force microscopy (AFM), and photoreflectance spectroscopy (PR). According to the results of AFM and HRSEM, by the thermal treatment we obtained a better distribution of quantum dot sizes in comparison with a reference sample with no treatment. The PR spectra from 0.9 to 1.35 eV presented two transitions associated with SAQDs. The energy transitions were obtained by fitting the PR spectra using the third derivative model.
ABSTRACT
Dynamic cardiomyoplasty was performed in twenty patients with dilated cardiomyopathy. The electrical stimulation was produced by a double chambered pacemaker. Patients were studied by nuclear ventriculography one week before surgery, in the immediate postoperative phase and 8 or 12 months later. Five patients died (four of them were operative deaths). In this group the left ventricular ejection fraction (LVEF) was lower than in survivors (22 +/- 8% vs 28 +/- 4%; p less than 0.001). The end-diastolic volume and the mitral regurgitation index were greater (200 +/- 76 ml/m2 vs 153 +/- 34 ml/m2; p less than 0.001 and 2.12 +/- 0.75 vs 1.68 +/- 0.54; p less than 0.001, respectively). The immediate effect of cardiomyoplasty was the significative reduction in the contractility. However, at 8 or 12 months of follow-up, the LVEF increased in the 72% of the survivors. The end-diastolic volume and the regurgitation index decreased significantly. The clinical status improved in the 81% of the survivors. The best results were obtained in those patients in which a pulse train stimulation was employed in the training phase. Nevertheless, the changes in LVEF are not consistent with the improvement in the clinical status. The improve in the cardiac performance should be also due to the reduction in the left ventricular diameters and in the mitral functional regurgitation.