The Role of Short-Range Disorder in BaWO4 Crystals in the Intense Green Photoluminescence

An intense and broad visible photoluminescence (PL) band was observed at room temperature in short-range disordered BaWO4 crystals. The scheelite crystalline BaWO4 powders prepared by the polymeric precursor method and annealed at different temperatures were structurally characterized by means of X-ray diffraction and Fourier transform (FT) Raman spectroscopy measurements. Quantum-mechanical calculations indicated that the disorder at short range only of Ba atoms in the BaWO4 lattice has a very important role in the charge transfer involved in the intense green PL emission. This indication was detected and confirmed by means of FT Raman spectroscopy measurements. The experimental and theoretical results are in good agreement, both showing the specific type of structural disorder that is the most favorable condition for generating the most intense green PL emission in the scheelite BaWO4 lattice.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação Amazônia Paraense de Amparo à Pesquisa (FAPESPA

Effect of the order and disorder of BaMoO4 powders in photoluminescent properties

The study of the photoluminescent properties affected by order and disorder of the BaMoO4 powders is the principal objective in this work. BaMoO4 compounds were prepared using soft chemical process called Complex Polymerization Method. In this work, different deagglomeration types and different heating rates were used to promote different disorder degrees. Scheelite type phase (BaMoO4) was determined by X-ray Diffraction (XRD), Fourier Transformed Infra-Red (FTIR) and Raman spectroscopy after heat treating the sample at 400 degrees C. The room temperature luminescence spectra revealed an intense single-emission band in the visible region. Based on XRD and Raman data it was observed that the transition between the completely disordered structure to completely ordered structure is a good condition for photoluminescence (PL) emission. The best PL emission is obtained when the material possesses short range disorder, i.e., is periodically ordered (XRD), but some disorder as measured by Raman spectroscopy. The excellent optical properties observed for disordered BaMoO4 suggested that this material is a highly promising candidate for optical applications

Estudio exploratorio para el desarrollo de un dispositivo de asistencia cardíaca

Proyecto de Investigación. Instituto Tecnológico de Costa Rica. Vicerrectoría de Investigación y Extensión (VIE). Escuela de Ingeniería Electrónica, Escuela de Física; Hospital Rafael Ángel Calderón Guardia; Clínica El Roble, 2012Las enfermedades cardiovasculares son la causa principal de muerte en Costa Rica. Los dispositivos de asistencia circulatoria pueden ser utilizados en operaciones del corazón o como asistencia en casos de insuficiencia cardíaca severa, dependiendo del diseño y configuración del mismo. Este documento plantea el estudio exploratorio realizado con miras a proponer un proyecto a largo plazo para desarrollar un dispositivo de asistencia ventricular autóctono, que presente mejoras sustanciales a dispositivos aplicables en el tratamiento de personas con insuficiencia cardíaca, particularmente de aquellas en fases terminales de su enfermedad. La disponibilidad a estos sistemas de asistencia circulatoria en el país es limitada, debido a su escaso número y su precio. Los resultados tratados en este documento se pueden agrupar en cuatro temas: estadísticas de enfermedades cardíacas en el país, modelos del sistema cardiovascular, modelos de sangre en los vasos sanguíneos y funcionamiento de dispositivos de asistencia ventricular actuales. Por otra parte, este proyecto ha permitido determinar que la implementación de un sistema de apoyo circulatorio con capacidad de asistir las funciones cardíacas comprende aspectos técnicos como la especificación, desarrollo y escogencia de probables fuentes de energía, posibles materiales, sistema de control adecuado y posibilidad de aplicabilidad y maniobrabilidad según la condición clínica de cada posible receptor. Por está razón se presenta un diagrama de ruta con las etapas que, hasta la entrega de este informe, se ha determinado son necesarias para el desarrollo de un sistema de asistencia ventricular en el TEC.Cardiovascular diseases are the major cause of death in Costa Rica. Circulatory assist devices can be used in heart surgeries or as assistance in severe heart failure cases, this function depends on its design and configuration. This document presents the results of an exploratory study conducted in order to propose a project with the aim to develop and improve devices used in heart failure treatments, especially for those patients with an advanced stage of this disease.. Costa Rica has limited access to this kind of systems due to the low number of available devices and their price. The results discussed in this report can be grouped into four themes: heart disease statistics in the country, cardiovascular system models, models of blood in blood vessels and performance and characteristics of existing ventricular assist devices. Furthermore, this project has allowed to identified several requierements to implement a circulatory support system able to assist heart function, such as technical aspects like specification, development and selection of energy sources, possible materials, proper control system, applicability and maneuverability depending on the clinical condition of each patient. For this reason, we present a route map with the steps we have determined are necessary for the development of a ventricular assist system in the TEC

Experimental and theoretical approach of nanocrystalline TiO2 with antifungal activity

Using a solvothermal method for this research we synthesized nanocrystalline titanium dioxide (nc-TiO2) anatase particles with a mean diameter of 5.4 nm and evaluated their potential antifungal effect against planktonic cells of Candida albicans without UV radiation. To complement experimental data, we analyzed structural and electronic properties of both the bulk and the (101) surface of anatase by first-principles calculations. Based on experimental and theoretical results, a reactive O2H* and OH* species formation mechanism was proposed to explain the key factor which facilitates the antifungal activity.CAPESCNPqFAPESPGeneralitat Valenciana (Prometeo 2009/053

CaTiO3:Eu3+ obtained by microwave assisted hydrothermal method: A photoluminescent approach

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq