Eine verlustleistungsoptimierte Dezimator-Architektur für kaskadierte Sigma-Delta Analog-Digital Umsetzer

Dieser Beitrag stellt einen neuartigen Ansatz einer leistungsfähigen Dezimator-Architektur f¨ur kaskadierte Sigma-Delta Modulatoren vor. Die Besonderheit der dargestellten Struktur ist die Integration der Rekombinationslogik kaskadierter Modulatoren und der Korrektur des Verstärkungsfehlers zeitkontinuierlicher (continuous time, CT) Modulatoren in die erste Stufe des Dezimators. Der Entwurf einer passenden Filtertopologie wird abgeleitet, analysiert und durch Simulationen verifiziert. Die vorgeschlagene Struktur wird mit einer herk¨ommlichen Implementierung verglichen. Das Ergebnis dieses Vergleiches ist eine Verbesserung der Effizienz um Dekaden

Persistent photovoltage in methylammonium lead iodide perovskite solar cells

Open circuit voltage decay measurements are performed on methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells to investigate the charge carrier recombination dynamics. The measurements are compared to the two reference polymer-fullerene bulk heterojunction solar cells based on P3HT:PC60BM and PTB7:PC70BM blends. In the perovskite devices, two very different time domains of the voltage decay are found, with a first drop on a short time scale that is similar to the organic solar cells. However, two major differences are also observed. 65-70% of the maximum photovoltage persists on much longer timescales, and the recombination dynamics are dependent on the illumination intensity.Comment: 5 pages, 3 figure

Decoding Charge Recombination through Charge Generation in Organic Solar Cells

The in‐depth understanding of charge carrier photogeneration and recombination mechanisms in organic solar cells is still an ongoing effort. In donor:acceptor (bulk) heterojunction organic solar cells, charge photogeneration and recombination are inter‐related via the kinetics of charge transfer states—being singlet or triplet states. Although high‐charge‐photogeneration quantum yields are achieved in many donor:acceptor systems, only very few systems show significantly reduced bimolecular recombination relative to the rate of free carrier encounters, in low‐mobility systems. This is a serious limitation for the industrialization of organic solar cells, in particular when aiming at thick active layers. Herein, a meta‐analysis of the device performance of numerous bulk heterojunction organic solar cells is presented for which field‐dependent photogeneration, charge carrier mobility, and fill factor are determined. Herein, a “spin‐related factor” that is dependent on the ratio of back electron transfer of the triplet charge transfer (CT) states to the decay rate of the singlet CT states is introduced. It is shown that this factor links the recombination reduction factor to charge‐generation efficiency. As a consequence, it is only in the systems with very efficient charge generation and very fast CT dissociation that free carrier recombination is strongly suppressed, regardless of the spin‐related factor

A theoretical study of the structural phases of Group 5B - 6B metals and their transport properties

In order to predict the stable and metastable phases of the bcc metals in the block of the Periodic Table defined by groups 5B to 6B and periods 4 to 6, as well as the structure dependence of their transport properties, we have performed full potential computations of the total energies per unit cell as a function of the c/a ratio at constant experimental volume. In all cases, a metastable body centered tetragonal (bct) phase was predicted from the calculations. The total energy differences between the calculated stable and metastable phases ranged from 0.09 eV/cell (vanadium) to 0.39 eV/cell (tungsten). The trends in resistivity as a function of structure and atomic number are discussed in terms of a model of electron transport in metals. Theoretical calculations of the electrical resistivity and other transport properties show that bct phases derived from group 5B elements are more conductive than the corresponding bcc phases, while bct phases formed from group 6B elements are less conductive than the corresponding bcc phases. Special attention is paid to the phases of tantalum where we show that the frequently observed beta phase is not a simple tetragonal distortion of bcc tantalum

SISTEMAS DE PROPAGAÇÃO E CULTIVO DA CORTIÇA LISA NO ALTO VALE DO ITAJAÍ

A cortiça-lisa (Rollinia rugulosa) da família Annonaceae é uma das árvores nativas do Brasilque tem grande importância ecológica e potencial de exploração comercial. Atualmente,grande parte da população não tem o conhecimento sobre a existência dessa planta. Sãonecessárias pesquisas que contemplem a propagação eficiente dessa espécie devido ao fatodela estar sendo extinta do nosso ecossistema, apesar de seu potencial de produção econsumo. Além disso, constamos a pouca literatura existente com assuntos relacionados acultura. Com este trabalho pretendemos conhecer métodos mais adequados de produção demudas e verificar a qualidade dos frutos obtidos em acessos da região, identificando plantaspara propagação.O experimento foi conduzido no Instituto Federal Catarinense-Campus Riodo Sul, sendo a produção de mudas no setor de fruticultura e silvicultura e análise dequalidade de frutos no Laboratório de Pós-colheita do IFC, com a espécie de cortiça-lisaRollinia rugulosa. Forão coletadas frutos de acessos de plantas do IFC e região do Alto Vale,a partir de informações e dados coletados de proprietários da região. As sementes foramretiradas dos frutos, lavadas e postas a secar a sombra por um dia. Após este processo, foramavaliados periodicamente a germinação das sementes e o crescimento das plantas.Foramavaliadas quantidade (a campo) e qualidade de frutos quanto a massa, rendimento de polpa,SST (ºbrix), acidez titulável (%), firmeza da polpa e acidez. As sementes obtidas de frutoscoletados foram semeadas e estão sendo avaliados a germinação e crescimento inicial dasmudas, cujos dados completos ainda não estão a disposição.Houve grande variabilidade dedados obtidos nas diferentes localidades (Tabela 1), indicando materiais promissores parautilização comercial, com elevado Brix em torno de 16 0 B e baixa acidez(6 %) em Taió eItuporanga principalmente. Além destes há outros fatores ainda a serem considerados,principalmente após a realização de análise estatística

Coat genetic markers of the domestic cat Felis catus (Felidae) from southwestern Colombia

Objectives. Establish the genetic profiles of cats from 12 neighboring municipalities in southwestern Colombia, in a town course from Pereira-Popayán. Estimate the degree of diversity, genetic structure, and quantify gene flow. Materials and methods. Were inventoried the phenotypic markers present in the pigmentation and structure of the coat of 1482 cats of the municipalities surveyed. Based on these phenotypic frequencies, allele frequencies, heterozygosity, Hardy-Weinberg equilibrium, F statistics and Nei genetic distances were calculated. A comparison was also made between genetic and geographic distance matrices to determine if there was a significant association between the two. Results. With the genetic profiles of the populations we estimated the degree of diversity. We found the populations in equilibrium for the S autosomal locus and for the O sex-linked locus. We found a low level genetic structure, and it was determined that there was no significant correlation between the genetic and geographic distance matrices among populations. Conclusions: These findings can be explained on the basis of the processes of human displacement for this region, due to the fact that the establishment of feline populations in these municipalities originated during the same historical period. Identical genetic profiles are shared as a result of colonization events, and due to possible continued migration among these populations. Objetivos. Determinar los perfiles genéticos de los gatos de 12 municipios contiguos del suroccidente colombiano en un trayecto Pereira-Popayán; estimar el grado de diversidad, estructura genética y cuantificar el flujo de genes. Materiales y métodos. Se inventariaron los marcadores fenotípicos presentes en la pigmentación y estructura del pelaje de 1482 gatos de los municipios estudiados, con base en estas frecuencias fenotípicas se calcularon frecuencias alélicas, heterocigosidad, equilibrio Hardy-Weinberg, el estadístico FST y distancias genéticas de Nei. También se realizó una comparación entre matrices de distancia genética y geográfica para determinar si existía asociación significativa entre las dos. Resultados. Con los perfiles genéticos de las poblaciones se estimó el grado de diversidad, se halló en equilibrio Hardy-Weinberg a las poblaciones para el locus autosómico S y el locus ligado al sexo O. Se encontró bajo nivel de estructura genética y se determinó que no existe correlación significativa entre las matrices de distancia genética y geográfica entre poblaciones. Conclusiones. Estos hallazgos se pueden explicar con base en los procesos de desplazamiento humano para esta región, debido a que el establecimiento de poblaciones felinas en estos municipios se originó en el mismo período histórico. Se comparten perfiles genéticos idénticos como resultado, posiblemente, de eventos de colonización y migración continua entre estas poblaciones

cAMP-Signalling Regulates Gametocyte-Infected Erythrocyte Deformability Required for Malaria Parasite Transmission.

Blocking Plasmodium falciparum transmission to mosquitoes has been designated a strategic objective in the global agenda of malaria elimination. Transmission is ensured by gametocyte-infected erythrocytes (GIE) that sequester in the bone marrow and at maturation are released into peripheral blood from where they are taken up during a mosquito blood meal. Release into the blood circulation is accompanied by an increase in GIE deformability that allows them to pass through the spleen. Here, we used a microsphere matrix to mimic splenic filtration and investigated the role of cAMP-signalling in regulating GIE deformability. We demonstrated that mature GIE deformability is dependent on reduced cAMP-signalling and on increased phosphodiesterase expression in stage V gametocytes, and that parasite cAMP-dependent kinase activity contributes to the stiffness of immature gametocytes. Importantly, pharmacological agents that raise cAMP levels in transmissible stage V gametocytes render them less deformable and hence less likely to circulate through the spleen. Therefore, phosphodiesterase inhibitors that raise cAMP levels in P. falciparum infected erythrocytes, such as sildenafil, represent new candidate drugs to block transmission of malaria parasites

The impact of SARS on hospital performance

© 2008 Chu et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Coastal and transitional waters North East Atlantic geographic intercalibration group: Seagrasses ecological assessment methods

The European Water Framework Directive (WFD) requires the national classifications of good ecological status to be harmonised through an intercalibration exercise. In this exercise, significant differences in status classification among Member States are harmonized by comparing and, if necessary, adjusting the good status boundaries of the national assessment methods. Intercalibration is performed for rivers, lakes, coastal and transitional waters, focusing on selected types of water bodies (intercalibration types), anthropogenic pressures and Biological Quality Elements. Intercalibration exercises are carried out in Geographical Intercalibration Groups - larger geographical units including Member States with similar water body types - and followed the procedure described in the WFD Common Implementation Strategy Guidance document on the intercalibration process (European Commission, 2011). The Technical report on the Water Framework Directive intercalibration describes in detail how the intercalibration exercise has been carried out for the water categories and biological quality elements. The Technical report is organized in volumes according to the water category (rivers, lakes, coastal and transitional waters), Biological Quality Element and Geographical Intercalibration group. This volume addresses the intercalibration of the Coastal and Transitional Waters-North East Atlantic GIG seagrasses ecological assessment methods.JRC.D.2-Water and Marine Resource