Electroreflectance spectroscopy in self-assembled quantum dots: lens symmetry

Modulated electroreflectance spectroscopy $\Delta R/R$ of semiconductor self-assembled quantum dots is investigated. The structure is modeled as dots with lens shape geometry and circular cross section. A microscopic description of the electroreflectance spectrum and optical response in terms of an external electric field (${\bf F}$) and lens geometry have been considered. The field and lens symmetry dependence of all experimental parameters involved in the $\Delta R/R$ spectrum have been considered. Using the effective mass formalism the energies and the electronic states as a function of ${\bf F}$ and dot parameters are calculated. Also, in the framework of the strongly confined regime general expressions for the excitonic binding energies are reported. Optical selection rules are derived in the cases of the light wave vector perpendicular and parallel to $$. Detailed calculation of the Seraphin coefficients and electroreflectance spectrum are performed for the InAs and CdSe nanostructures. Calculations show good agreement with measurements recently performed on CdSe/ZnSe when statistical distribution on size is considered, explaining the main observed characteristic in the electroreflectance spectra

Electronic, vibrational, and thermodynamic properties of ZnS (zincblende and rocksalt structure)

We have measured the specific heat of zincblende ZnS for several isotopic compositions and over a broad temperature range (3 to 1100 K). We have compared these results with calculations based on ab initio electronic band structures, performed using both LDA and GGA exchange- correlation functionals. We have compared the lattice dynamics obtained in this manner with experimental data and have calculated the one-phonon and two-phonon densities of states. We have also calculated mode Grueneisen parameters at a number of high symmetry points of the Brillouin zone. The electronic part of our calculations has been used to investigate the effect of the 3d core electrons of zinc on the spin-orbit splitting of the top valence bands. The effect of these core electrons on the band structure of the rock salt modification of ZnS is also discussed.Comment: 33pages, 16 Figures, submitted to Phys. Rev.

Above-bandgap ordinary optical properties of GaSe single crystal

We report above-bandgap ordinary optical properties of ε-phase GaSe single crystal. Reference-quality pseudodielectric function 〈ε(E)〉 = 〈ε1(E)〉+i〈ε2(E)〉 and pseudorefractive index 〈N(E)〉 = 〈n(E)〉+i〈k(E)〉 spectra were measured by spectroscopic ellipsometry from 0.73 to 6.45 eV at room temperature for the light polarization perpendicular to the optic axis (math⊥math). The 〈ε〉 spectrum exhibited several interband-transition critical-point structures. Analysis of second-energy derivatives calculated numerically from the measured data yielded the critical-point energy [email protected]

Electronic and phononic properties of cinnabar: ab initio calculations and some experimental results

We report ab initio calculations of the electronic band structure, the corresponding optical spectra, and the phonon dispersion relations of trigonal alpha-HgS (cinnabar). The calculated dielectric functions are compared with unpublished optical measurements by Zallen and coworkers. The phonon dispersion relations are used to calculate the temperature and isotopic mass dependence of the specific heat which has been compared with experimental data obtained on samples with the natural isotope abundances of the elements Hg and S (natural minerals and vapor phase grown samples) and on samples prepared from isotope enriched elements by vapor phase transport. Comparison of the calculated vibrational frequencies with Raman and ir data is also presented. Contrary to the case of cubic beta-HgS (metacinnabar), the spin-orbit splitting of the top valence bands at the Gamma-point of the Brillouin zone (Delta_0) is positive, because of a smaller admixture of 5d core electrons of Hg. Calculations of the lattice parameters, and the pressure dependence of Delta_0 and the corresponding direct gap E_0~2eV are also presented. The lowest absorption edge is confirmed to be indirect.Comment: 13 pages, 15 figure

Diseño de una Estación de Trabajo para Personas con Discapacidad en Miembros Superiores Usando una Interfaz Cerebro Computador

This paper shows the design of work-station for work-related inclusion people upper-limb disability. The system involves the use of novel brain computer interface used to bridge the user-computer interaction. Our hope objective is elucidating functional, technological, ergonomic and procedural aspects to runaway operation station; with propose to scratch barrier to impossibility access to TIC’s tools and work done for individual disability person. We found access facility ergonomics, adaptability and portable issue of workstation are most important design criteria. Prototype implementations in workplace environment have TIR estimate of 43% for retrieve. Finally we list a typology of services that could be the most appropriate for the process of labor including: telemarketing, telesales, telephone surveys, order taking, social assistance in disasters, general information and inquiries, reservations at tourist sites, technical support, emergency, online support and after-sales services.  El presente trabajo presenta el diseño de una estación de trabajo para la inclusión laboral de personas en estado de discapacidad en miembros superiores. El sistema involucra el uso de una novedosa interfaz cerebro computador que sirve como puente entre el usuario y el ordenador. Nuestro objetivo es dilucidar los aspectos funcionales, tecnológicos, ergonómicos y procedimentales de la puesta en marcha de la estación de trabajo; con el fin de romper con las barreas que imposibilitan el acceso a las herramientas TIC’s y el trabajo por parte de las personas en estado de discapacidad en miembros superiores. Se encontró que la facilidad de acceso, la ergonomía, la adaptabilidad y la portabilidad de la estación de trabajo son los criterios de diseño más importantes. La implementación de este prototipo en una ambiente laboral tiene una TIR estimada de 43% para retribución. Finalmente se describe una tipología de servicios que podrían ser los más indicados para el proceso de inclusión laboral: telemarketing, televentas, encuestas telefónicas, toma de pedidos, ayuda social en catástrofes, información general y consultas, reservaciones en sitios turísticos, soporte técnico, emergencias, asistencia en línea y servicios posventa

Control De Un Motor Utilizando Lógica Difusa Con Reglas Sintonizadas Por Algoritmos Genéticos

En este documento se describe la implementación de un controlador PI difuso incremental con una base de reglas para un motor de corriente continua controlado por campo. La matriz de reglas es sintonizada a través de algoritmos genéticos. El controlador está diseñado para llevar el motor desde una condición inicial de 0 a 100rpm (revoluciones por minuto). Las simulaciones y los resultados obtenidos muestran un comportamiento óptimo del sistema

Control De Un Motor Utilizando Lógica Difusa Con Reglas Sintonizadas Por Algoritmos Genéticos

En este documento se describe la implementación de un controlador PI difuso incremental con una base de reglas para un motor de corriente continua controlado por campo. La matriz de reglas es sintonizada a través de algoritmos genéticos. El controlador está diseñado para llevar el motor desde una condición inicial de 0 a 100rpm (revoluciones por minuto). Las simulaciones y los resultados obtenidos muestran un comportamiento óptimo del sistema

Control De Un Motor Utilizando Lógica Difusa Con Reglas Sintonizadas Por Algoritmos Genéticos

En este documento se describe la implementación de un controlador PI difuso incremental con una base de reglas para un motor de corriente continua controlado por campo. La matriz de reglas es sintonizada a través de algoritmos genéticos. El controlador está diseñado para llevar el motor desde una condición inicial de 0 a 100rpm (revoluciones por minuto). Las simulaciones y los resultados obtenidos muestran un comportamiento óptimo del sistema

Análise cienciométrica das tendências de pesquisa sobre o risco de suicídio na infância e adolescência

The aim of this bibliometric paper was to analyze the scientific production on biopsychosocial risk factors leading to suicide in childhood and adolescence using graph theory. The Scopus (Elsevier) and Web of Science databases were consulted and the analysis was performed using bibliometrix, Sci2 tool and Gephi. A total of 2,058 records were found. The analysis of the records revealed a citation network of 2,905 records and four main clusters. The results showed a network structure of knowledge production behavior in four research trends: (1) psychiatric predictors of suicidal behavior in children and adolescents; (2) association between non-suicidal self-injurious behavior and suicidal behavior in adolescents; (3) relationship between child abuse and suicidal behavior; (4) use of antidepressants in childhood and adolescence and suicidal behavior. Finally, considerations for suicide prevention in the study population are raised.El objetivo del presente estudio bibliométrico consistió en analizar la producción científica acumulada sobre los factores de riesgo biopsicosocial conducentes al suicidio en la infancia y la adolescencia mediante la implementación de la teoría de grafos. Se consultaron las bases de datos Scopus (Elsevier) y Web of Science, y el análisis se efectuó en bibliometrix, Sci2 tool y Gephi. Se encontraron 2,058 registros. El análisis mostró una red de citaciones de 2,905 registros y cuatro clústeres principales. Los resultados arrojaron una estructura de red de la producción de conocimiento en cuatro tendencias de investigación: (1) factores de predicción de tipo psiquiátrico del comportamiento suicida en niños y adolescentes; (2) asociación entre conducta autolesiva no suicida y comportamiento suicida en adolescentes; (3) relación entre maltrato infantil y suicidio; (4) uso de antidepresivos en la niñez y adolescencia y comportamiento suicida. Finalmente, se plantean consideraciones para la prevención del suicidio en la población objeto de estudio.O objetivo deste estudo bibliométrico foi analisar a produção científica sobre os fatores de risco biopsicossociais que levam ao suicídio na infância e adolescência utilizando a teoria dos grafos. Foram consultadas as bases de dados Scopus (Elsevier) e Web of Science e a análise foi realizada no bibliometrix, Sci2 e Gephi. Foram encontrados 2058 registos. A análise revelou uma rede de citações com 2905 registos e quatro clusters principais. Os resultados geraram uma estrutura de rede de produção de conhecimento em quatro tendências de pesquisa: (1) preditores de tipo psiquiátrico de comportamento suicida em crianças e adolescentes; (2) associação entre comportamento autolesivo não suicida e comportamento suicida adolescente; (3) relação entre maltrato infantil e suicídio; (4) uso de antidepressivos na infância e adolescência e comportamento suicida. Por fim, são propostas considerações para a prevenção do suicídio na população em estudo

Explorando el potencial de las tecnologías ómicas en la investigación de plantas medicinales: una revisión en Colombia

This review presents advances in the implementation of high-throughput sequencing and its application to the knowledge of medicinal plants. We conducted a bibliographic search of papers published in PubMed, Science Direct, Google Scholar, Scopus, and Web of Science databases and analyzed the obtained data using VOSviewer (version 1.6.19). Given that medicinal plants are a source of specialized metabolites with immense therapeutic values and important pharmacological properties, plant researchers around the world have turned their attention toward them and have begun to examine them widely. Recent advances in sequencing technologies have reduced cost and time demands and accelerated medicinal plant research. Such research leverages full genome sequencing, as well as RNA (ribonucleic acid) sequencing and the analysis of the transcriptome, to identify molecular markers of species and functional genes that control key biological traits, as well as to understand the biosynthetic pathways of bioactive metabolites and regulatory mechanisms of environmental responses. As such, the omics (e.g., transcriptomics, metabolomics, proteomics, and genomics, among others) have been widely applied within the study of medicinal plants, although their usage in Colombia is still few and, in some areas, scarce. (185)El extracto de cloroformo (CE) y las fracciones obtenidas de las raíces de Aldama arenaria se evaluaron para determinar su actividad antiproliferativa in vitro contra 10 líneas celulares tumorales humanas [leucemia (K-562), mama (MCF-7), ovario que expresa un fenotipo resistente a múltiples fármacos (NCI/ADR-RES), melanoma (UACC-62), pulmón (NCI-H460), próstata (PC-3), colon (HT29), ovario (OVCAR-3), glioma (U251) y riñón (786-0)]. CE presentó actividad antiproliferativa débil a moderada (log GI50 medio 1.07), mientras que las fracciones 3 y 4, enriquecidas con diterpenos de tipo pimarane [ent-pimara-8 (14), ácido 15-dien-19-oico y ent-8(14),15-pimaradien-3β-ol], presentaron actividad moderada a potente para la mayoría de las líneas celulares, con un log GI50 medio de 0.62 y 0.59, respectivamente. Los resultados mostraron una acción antiproliferativa in vitro prometedora de las muestras obtenidas de A. arenaria, con los mejores resultados para NCI/ADR-RES, HT29 y OVCAR-3, y valores de TGI que van desde 5.95 a 28.71 µg.mL-1, demostrando que los compuestos de esta clase pueden ser prototipos potenciales para el descubrimiento de nuevos agentes terapéuticos