Cathodoluminescence investigations of GaAs thin layers

AbstractIn this work, we report the theoretical results of cathodoluminescence (CL) for GaAs layer. The simulation of the CL excitation and intensity is developed using 2-D model based on the electron beam energy dissipation and taking into account the effects of carrier diffusion, internal absorption and the recombination process in the semiconductors.We have investigated the influence of the electron beam conditions (energy, current and beam diameter) and some physical parameters (absorption coefficient, gap energy) on the CL intensity. Results allow us particularly to predict the intensity evolution and shift of CL peak emitted near the fundamental energy gap as a function of the electron beam current and energy. A comparative study between simulated and experimental CL spectra at low temperature is realized

INTERFACIAL RELAXATION IN SEMI-CRYSTALLINE POLYMER

Abstract The semi-crystalline morphology of a series of poly(ether ether ketone) (PEEK) has been investigated as a function of crystallization condition by dielectric relaxation spectroscopy. An interfacial polarization effect, known as the Maxwell-Wagner-Sillars polarization, is clearly evident taking place at the interface between the crystalline inclusions and the amorphous matrix. The intensity of the relaxation is presented in relation to the morphology of the crystalline part which is known to depend on annealing conditions

Waterpipe (narghile) smoking among medical and non-medical university students in Turkey

Objectives. This investigation was performed in order to determine the prevalence rate of waterpipe smoking in students of Erciyes University and the effects of some socio-demographic factors

Synthesis and in vitro antiproliferative activity of novel (4-chloro- and 4-acyloxy-2-butynyl)thioquinolines

The series of new acetylenic thioquinolines containing propargyl, 4-chloro-2-butynyl, and 4-acyloxy-2-butynyl groups have been prepared and tested for antiproliferative activity in vitro against human [SW707 (colorectal adenocarcinoma), CCRF/CEM (leukemia), T47D (breast cancer)] and murine [P388 (leukemia), B16 (melanoma)] cancer lines. Most of the obtained compounds exhibited antiproliferative activity, especially compounds 8, 12, and 21 showed the ID50 values ranging from 0.4 to 3.8 μg/ml comparable to that of cisplatin used as reference compounds

Symbolic analysis of analog circuits containing voltage mirrors

7 páginas, 7 figuras, 2 tablas, 4 imágenes.-- Open Access: This article is distributed under the terms of the Creative Commons Attribution Noncommercial License.The pathological elements voltage mirror (VM) and current mirror (CM) have shown advantages in analog behavioral modeling and circuit synthesis, where many nullor-mirror equivalences have been explored to design and to transform voltage-mode circuits to current-mode ones and viceversa. However, both the VM and CM have not equivalents to perform automatic symbolic circuit analysis. In this manner, we introduce nullor-equivalents for these pathological elements allowing to include parasitics and to perform only symbolic nodal analysis. The nullor-equivalent of the CM is extended to provide multiple-outpus (MO-CM). Finally, two active filters containing VMs, CMs and MO-CMs are analysed to show the usefulness of the models.This work is supported by: UC-MEXUS and CONACyT under grants CN-09-310 and 48396-Y; by Promep-Mexico under grant UATLX-PTC-088; by Consejeria de Innovacion, Ciencia y Empresa, Junta de Andalucia-Spain TIC-2532; and by the JAE-Doc program of CSIC co-funded by FSE, Spain.Peer reviewe

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

ASPECTS MORPHOLOGIQUES DE LA CROISSANCE CRISTALLINE D'UN CALCUL RÉNAL

Nous proposons de classer les calculs rénaux en trois catégories correspondantes à trois mécanismes possibles de croissance des calculs en se basant sur des études morphologiques faites à l'aide d'un microscope électronique à balayage (MEB).Using morphological studies done on a scanning electron microscope (SEM), We propose to divide kidney Stones in three catégories corresponding to three possible associated growth mechanisms

An experimental approach for dynamic investigation of the trapping properties of glass-ceramic under electron beam irradiation from a scanning electron microscope

A method is described that allows the trapping charge kinetics in insulating materials during their electron irradiation in a scanning electron microscope (SEM) to be studied and the total trapped charge to be evaluated. The method consists in analyzing the leakage and the displacement currents measured simultaneously, during and after irradiation, using an arrangement adapted to the SEM. The dynamic trapping properties of glass-ceramic are investigated and the time constants for charging and discharging processes are evaluated. By correlating the leakage and displacement currents, the total electron yield σ during irradiation is also determined