Análisis comparativo de diferentes técnicas de modulación PWM en convertidores de potencia

Buena parte del desarrollo y aplicación industrial de los convertidores de potencia se debe al avance experimentado en la generación de cualquier forma de onda de tensión deseada. La aparición de las técnicas de modulación, unido a la posibilidad de implementarlas en modernos microprocesadores o dispositivos electrónicos configurables (FPGA), ha favorecido el uso de los convertidores de potencia y el desarrollo industrial y comercial de propulsores eléctricos en vehículos, generadores eólicos, ascensores ecológicos, etc., por citar algunos ejemplos. Diferentes métodos de modulación, centrados en la generación de portadora o en la resolución analítica de un problema n-dimensional (modulación conocida como Space Vector Pulse Width Modulation o SVPWM), permiten que un convertidor de potencia imponga cualquier forma de onda de tensión que se desee a la carga a la que se encuentra conectado. Las diferentes estrategias de modulación se han ido complicando para lograr la mayor fiabilidad en la generación de la tensión deseada (menor ruido eléctrico). En este trabajo se analizan y comparan diferentes técnicas de modulación basadas en portadora o Space Vector, empleando herramientas de simulación basadas en Matlab y Simulink. El objetivo es plantear un análisis comparativo, que permita al alumno entender el interés y funcionamiento de cada técnica de modulación, observando las ventajas e inconvenientes asociadas

Protein kinase B (AKT) upregulation and Thy-1-α_vβ₃ integrin-induced phosphorylation of Connexin43 by activated AKT in astrogliosis.

In response to brain injury or inflammation, astrocytes undergo hypertrophy, proliferate, and migrate to the damaged zone. These changes, collectively known as "astrogliosis", initially protect the brain; however, astrogliosis can also cause neuronal dysfunction. Additionally, these astrocytes undergo intracellular changes involving alterations in the expression and localization of many proteins, including α <sub>v</sub> β <sub>3</sub> integrin. Our previous reports indicate that Thy-1, a neuronal glycoprotein, binds to this integrin inducing Connexin43 (Cx43) hemichannel (HC) opening, ATP release, and astrocyte migration. Despite such insight, important links and molecular events leading to astrogliosis remain to be defined. Using bioinformatics approaches, we analyzed different Gene Expression Omnibus datasets to identify changes occurring in reactive astrocytes as compared to astrocytes from the normal mouse brain. In silico analysis was validated by both qRT-PCR and immunoblotting using reactive astrocyte cultures from the normal rat brain treated with TNF and from the brain of a hSOD1 <sup>G93A</sup> transgenic mouse model. We evaluated the phosphorylation of Cx43 serine residue 373 (S373) by AKT and ATP release as a functional assay for HC opening. In vivo experiments were also performed with an AKT inhibitor (AKTi). The bioinformatics analysis revealed that genes of the PI3K/AKT signaling pathway were among the most significantly altered in reactive astrocytes. mRNA and protein levels of PI3K, AKT, as well as Cx43, were elevated in reactive astrocytes from normal rats and from hSOD1 <sup>G93A</sup> transgenic mice, as compared to controls. In vitro, reactive astrocytes stimulated with Thy-1 responded by activating AKT, which phosphorylated S373Cx43. Increased pS373Cx43 augmented the release of ATP to the extracellular medium and AKTi inhibited these Thy-1-induced responses. Furthermore, in an in vivo model of inflammation (brain damage), AKTi decreased the levels of astrocyte reactivity markers and S373Cx43 phosphorylation. Here, we identify changes in the PI3K/AKT molecular signaling network and show how they participate in astrogliosis by regulating the HC protein Cx43. Moreover, because HC opening and ATP release are important in astrocyte reactivity, the phosphorylation of Cx43 by AKT and the associated increase in ATP release identify a potential therapeutic window of opportunity to limit the adverse effects of astrogliosis

Experiencia práctica de tipo interdisciplinar para manejo de dispositivos de potencia, instrumentación electrónica, sistemas microprocesadores e identificación paramétrica de sistemas dinámicos

El cambio en el entorno y en las dimensiones internas de las instituciones de educación superior provoca la necesidad de revisar el modelo educativo. Actualmente asistimos a la transformación de la Universidad provocada en gran medida por la revolución del conocimiento y las nuevas tecnologías de la información, que generan cambios tanto en el entorno como en los recursos internos disponibles en las universidades. El reto imperativo durante la próxima década es el cambio que debe producirse tanto en los productos que la Universidad ofrece (titulaciones, programas de postgrado, investigación, difusión, etc.) como en la forma en la que ofrece estos produ ctos, resultando necesario revisar los procesos docentes y haciéndose imperativa la introducción de la formación multidisciplinar. En este trabajo se presenta una experiencia práctica de tipo multidisciplinar, que aúna conceptos relacionados c on el manejo de herramientas de simulación basadas en Matlab y Simulink para el estudio de sistemas electrónicos digitales, analógicos y de potencia, así como el procesamiento de la señal y la identificación paramétrica de sistemas dinámicos. Se describirá el sistema con el que se trabajará (una máquina de inducción de 5 fases gobernada por un convertidor de potencia de 2 nivel es), para posteriormente definir su modelado empleando Matlab y Simulink y plantear los objetivos del trabajo de si mulación a realizar por los alumnos

Atacamite Cu2Cl(OH)3: A model compound for the S = 1/2 sawtooth chain?

We present a combined experimental and theoretical study of the mineral atacamite Cu2Cl(OH)3.Based on ab initio band structure calculations, we derive a magnetic coupling scheme of essentially a S = 1/2 sawtooth chain. Experimentally, we fully characterize the long-range antiferromagnetically ordered state and field-induced behavior, here for H k b axis. Magnetic order is suppressed by magnetic fields of ∼ 20 T, while beginning at 31.5 T we observe a wide magnetization plateau at half of the saturation magnetization, Msat/2. Numerical calculations for the magnetization M(H) of the quantum sawtooth chain reveal a plateau at Msat/2, raising the issue of the understandingof its microscopic nature.Fil: Heinze, L.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Jeschke, H.. Okayama University; Japón. Goethe Universitat Frankfurt; AlemaniaFil: Metavitsiadis, A.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Reehuis, M.. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH; AlemaniaFil: Feyerherm, R.. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH; AlemaniaFil: Hoffmann, J. U.. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH; AlemaniaFil: Wolter, A. U. B.. Leibniz Institute For Solid State And Materials Researc; AlemaniaFil: Ding, X.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Zapf, V.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Corvalán Moya, Carolina del Huerto. Comisión Nacional de Energía Atómica; Argentina. Los Alamos National High Magnetic Field Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Weickert, F.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Jaime, M.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Rule, K. C.. Australian Nuclear Science And Technology Organisation; AustraliaFil: Menzel, D.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Valenti, R.. Goethe Universitat Frankfurt; AlemaniaFil: Brenig, W.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; AlemaniaFil: Süllow, S.. Technische Universitat Carolo Wilhelmina Zu Braunschweig.; Alemani

The impact of the environment on health by country: a meta-synthesis

<p>Abstract</p> <p>Background</p> <p>Health gains that environmental interventions could achieve are main questions when choosing environmental health action to prevent disease. The World Health Organization has recently released profiles of environmental burden of disease for 192 countries.</p> <p>Methods</p> <p>These country profiles provide an estimate of the health impacts from the three major risk factors 'unsafe water, sanitation & hygiene', 'indoor air pollution from solid fuel use' and 'outdoor air pollution'. The profiles also provide an estimate of preventable health impacts by the environment as a whole. While the estimates for the three risk factors are based on country exposures, the estimates of health gains for total environmental improvements are based on a review of the literature supplemented by expert opinion and combined with country health statistics.</p> <p>Results</p> <p>Between 13% and 37% of the countries' disease burden could be prevented by environmental improvements, resulting globally in about 13 million deaths per year. It is estimated that about four million of these could be prevented by improving water, sanitation and hygiene, and indoor and outdoor air alone. The number of environmental DALYs per 1000 capita per year ranges between 14 and 316 according to the country. An analysis by disease group points to main preventions opportunities for each country.</p> <p>Conclusion</p> <p>Notwithstanding the uncertainties in their calculation, these estimates provide an overview of opportunities for prevention through healthier environments. The estimates show that for similar national incomes, the environmental burden of disease can typically vary by a factor five. This analysis also shows that safer water, sanitation and hygiene, and safer fuels for cooking could significantly reduce child mortality, namely by more than 25% in 20 of the lowest income countries.</p

Climate Change and Developing-Country Cities: Implications For Environmental Health and Equity

Climate change is an emerging threat to global public health. It is also highly inequitable, as the greatest risks are to the poorest populations, who have contributed least to greenhouse gas (GHG) emissions. The rapid economic development and the concurrent urbanization of poorer countries mean that developing-country cities will be both vulnerable to health hazards from climate change and, simultaneously, an increasing contributor to the problem. We review the specific health vulnerabilities of urban populations in developing countries and highlight the range of large direct health effects of energy policies that are concentrated in urban areas. Common vulnerability factors include coastal location, exposure to the urban heat-island effect, high levels of outdoor and indoor air pollution, high population density, and poor sanitation. There are clear opportunities for simultaneously improving health and cutting GHG emissions most obviously through policies related to transport systems, urban planning, building regulations and household energy supply. These influence some of the largest current global health burdens, including approximately 800,000 annual deaths from ambient urban air pollution, 1.2 million from road-traffic accidents, 1.9 million from physical inactivity, and 1.5 million per year from indoor air pollution. GHG emissions and health protection in developing-country cities are likely to become increasingly prominent in policy development. There is a need for a more active input from the health sector to ensure that development and health policies contribute to a preventive approach to local and global environmental sustainability, urban population health, and health equity

Human papillomavirus and Epstein-Barr virus infections in breast cancer from chile

<p>Abstract</p> <p>Background</p> <p>Human papillomavirus (HPV) and Epstein Barr virus (EBV) have been found in breast carcinomas (BCs) around the world. In this study, fifty-five BCs from Chile were analyzed for HPV and EBV presence. In addition, HPV-16 viral load/physical status and E6/E7 expressions were determined.</p> <p>Results</p> <p>The amplification of a housekeeping gene showed that 46/55 samples (84%) had amplifiable DNA. HPV-16 was detected in 4/46 BCs (8.7%) and EBV was detected in 3/46 (6.5%) BCs. The analysis of HPV-16 physical status showed that this virus was integrated in all of the tumors with a relatively low viral load (range: 0.14 to 33.8 copies/cell). E6 and E7 transcripts, however, were not detected in any HPV-16 positive specimens. Using a Cox-regression model, we found a statistically significant association between EBV presence and poor survival (p = 0.013).</p> <p>Conclusions</p> <p>The findings in this study suggest that it is unlikely that HPV and/or EBV play a direct role in the etiology of BC.</p

Saúde ambiental e desenvolvimento na Amazônia legal: indicadores socioeconômicos, ambientais e sanitários, desafios e perspectivas

Resumo Este artigo tem por objetivo discutir os processos de determinação socioambiental nos estados que compõem a Amazônia Legal, com base na análise de indicadores socioeconômicos, ambientais e sani tários. Nesse sentido, os resultados demonstraram uma região dinâmica e muito heterogênea, com uma população crescente e concentrada principal mente em áreas urbanas, combinando crescimento econômico e degradação ambiental a um rápido e precário processo de urbanização e aos projetos de desenvolvimento voltados para a exploração de recursos naturais. O resultado é um quadro com plexo de problemas de saúde, com expressividade das doenças infecciosas e parasitárias relaciona das às intensas mudanças ambientais e às difíceis condições de vida, decorrentes principalmente da persistência de imensas desigualdades nos indica dores sociais e econômicos. Tais vulnerabilidades produzem efeitos negativos no quadro ambiental e sanitário da região