Modulation of pure spin currents with a ferromagnetic insulator

We propose and demonstrate spin manipulation by magnetically controlled modulation of pure spin currents in cobalt/copper lateral spin valves, fabricated on top of the magnetic insulator Y$_3$Fe$_5$O$_{12}$ (YIG). The direction of the YIG magnetization can be controlled by a small magnetic field. We observe a clear modulation of the non-local resistance as a function of the orientation of the YIG magnetization with respect to the polarization of the spin current. Such a modulation can only be explained by assuming a finite spin-mixing conductance at the Cu/YIG interface, as it follows from the solution of the spin-diffusion equation. These results open a new path towards the development of spin logics.Comment: 5 pages and 4 figures + supplemental material (10 pages, 7 figures

Grid Integration of Offshore Wind Farms Using Modular Marx Multilevel Converters

This paper proposes the use of a Modular Marx Multilevel Converter, as a solution for energy integration between an offshore Wind Farm and the power grid network. The Marx modular multilevel converter is based on the Marx generator, and solves two typical problems in this type of multilevel topologies: modularity and dc capacitor voltage balancing. This paper details the strategy for dc capacitor voltage equalization. The dynamic models of the converter and power grid are presented in order to design the converter ac output voltages and the dc capacitor voltage controller. The average current control is presented and used for power flow control, harmonics and reactive power compensation. Simulation results are presented in order to show the effectiveness of the proposed (MC)-C-3 topology

Solid-State Bipolar Marx Generator with Voltage Droop Compensation

This paper addresses the voltage droop compensation associated with long pulses generated by solid-stated based high-voltage Marx topologies. In particular a novel design scheme for voltage droop compensation in solid-state based bipolar Marx generators, using low-cost circuitry design and control, is described. The compensation consists of adding one auxiliary PWM stage to the existing Marx stages, without changing the modularity and topology of the circuit, which controls the output voltage and a LC filter that smoothes the voltage droop in both the positive and negative output pulses. Simulation results are presented for 5 stages Marx circuit using 1 kV per stage, with 1 kHz repetition rate and 10% duty cycle

A New Modular Marx Derived Multilevel Converter

A new Modular Marx Multilevel Converter, M(3)C, is presented. The M(3)C topology was developed based on the Marx Generator concept and can contribute to technological innovation for sustainability by enabling wind energy off-shore modular multilevel power switching converters with an arbitrary number of levels. This paper solves both the DC capacitor voltage balancing problem and modularity problems of multilevel converters, using a modified cell of a solid-state Marx modulator, previously developed by authors for high voltage pulsed power applications. The paper details the structure and operation of the M(3)C modules, and their assembling to obtain multilevel converters. Sliding mode control is applied to a M(3)C leg and the vector leading to automatic capacitor voltage equalization is chosen. Simulation results are presented to show the effectiveness of the proposed M(3)C topology

Nanomineralogy of evaporative precipitation of efflorescent compounds from coal mine drainage

Efflorescent nanophases (NPs) are found as a transitory accumulation of potentially hazardous elements (PHEs), particularly in tropical climates. The central objective of this study was to investigate the distribution of PHEs with NPs through the evaporative formation structures (EFS) of enormously PHEs-rich coal-mine drainages (CMD). The EFS were studied in natural coal mine drainage for five months in order to determine their geochemical and ecological structures and to assess their position in the reduction of PHEs in nature. The largest coal-fired power plant in South America, located in south Brazil, is used as an example of such a problem. In this work, a novel methodology for the analysis of PHEs in CMD precipitates is proposed for this affected coal area. The analytical method, combining X-Ray Diffraction (XRD) and advanced electron microscopies, shows the importance of nanomineralogy in understanding different circumstances of coal contamination. Several ultrafine-nanoparticles (UNPs) were identified in the sampled soils and river sediments together with the PHEs. A decrease in PHEs was identified in association with UNPs. However, further investigations are required with regard to the mobility of PHEs in water, atmosphere, soils, and sediments. The EPS was thoroughly studied, acquiring suitable understanding with investigational facts for Ca and Fe-sulphates, pickeringite, and several amorphous phases

Solid-State Bipolar Marx Converter with Output Transformer and Energy Recovery

The purpose of this paper is to present and discuss a general HV topology of the solid-state Marx modulator, for unipolar or bipolar generation connected with a step-up transformer to increase the output voltage applied to a resistive load. Due to the use of an output transformer, discussion about the reset of the transformer is made to guarantee zero average voltage applied to the primary. It is also discussed the transformer magnetizing energy recovering back to the energy storage capacitors. Simulation results for a circuit that generates 100 kV pulses using 1000 V semiconductors are presented and discussed regarding the voltage and current stress on the semiconductors and result obtained

Prevalence of asthma and allergies in 13–14-year-old adolescents from Luanda, Angola

SETTING: The few epidemiological studies on asthma and allergic diseases performed in Africa have shown that the prevalence of these diseases is high or increasing. No such studies have been performed in Angola. OBJECTIVE : To determine the prevalence of asthma and other allergic diseases in Angolan adolescents. DESIGN: This was a descriptive, observational, crosssectional study in the province of Luanda, Angola, using the International Study of Asthma and Allergies in Childhood study methodology in adolescents aged 13 and 14 years. Twenty-three (12%) public schools were randomly selected. Data were analysed using the Statistical Package for the Social Sciences version 22.0 software. RESULTS : A total of 3128 adolescents were included. The prevalence of asthma (wheezing in the previous 12 months) was 13.4%. The prevalence of rhinitis (sneezing, runny or blocked nose in the previous 12 months) was 27% and that of eczema (itchy skin lesions in the previous 12 months) was 20%; both were more prevalent in girls. Rhinitis was associated with a greater number of episodes of night cough in adolescents with asthma. Rhinitis and eczema, a split-type air conditioning system, and frequent intake (more than once per month) of paracetamol were associated with a higher risk of having asthma. CONCLUSION: Asthma and related allergic diseases are a public health problem in adolescents from Luanda. Preventive and control measures should be implemented.info:eu-repo/semantics/publishedVersio

Prevalence of asthma, allergic rhinitis and eczema in 6–7-year-old schoolchildren from Luanda, Angola

Background: Epidemiological data have shown that the prevalence of asthma, rhinoconjunctivitis and eczema in children is still increasing, namely in Africa. However, there are no epidemiological studies on asthma or allergic diseases in Angolan children. Objective: To study the prevalence of asthma and other allergic diseases in Angolan children. Methods: Descriptive, observational, cross-sectional study, using the ISAAC study methodology, in the province of Luanda, Angola in 6-7-yearold children. Forty-six (8.3%) public schools were randomly selected. Data were analysed using the SPSS Statistics version 24.0 software. Results: A total of 3080 children were studied. Results showed that the prevalence of asthma (wheezing in the previous 12 months) was 15.8%, that of rhinitis (sneezing, runny or blocked nose in the previous 12 months) was 19% and that of eczema (itchy skin lesions in the previous 12 months) was 22%, without differences between sexes. Rhinitis was associated with a higher number of episodes of wheezing episodes, disturbed sleep and night cough, in children with asthma. Rhinitis, eczema, Split-type air conditioning system, antibiotic intake in the child's first year of life, frequent intake (more than once per month) of paracetamol and active maternal smoking were associated with a higher risk of having asthma, whereas electrical cooking was associated with a protective effect. Conclusion: Asthma and allergic diseases are highly prevalent in children from Luanda. A strategy for preventive and control measures should be implemented.info:eu-repo/semantics/publishedVersio

Deteção molecular de Mycobacterium avium subsp. paratuberculosis em raposas-vermelhas (Vulpes vulpes)

Deteção molecular de Mycobacterium avium subsp. paratuberculosis em raposas-vermelhas (Vulpes vulpes)

Simulación y análisis de desempeño de protocolos unicast para Redes VANET

Los cambios constantes de la topología en las redes VANET (vehicular Ad-Hoc Networks) la velocidad de movimiento de los nodos, entre otros problemas,  generan  desafíos  tecnológicos  en  el enrutamiento de estas redes, lo que ha llevado a la implementación de diferentes protocolos. El estudio y análisis de las características y desempeño  de los protocolos comúnmente empleados por las VANETs, permite la formulación de posibles solu-ciones a esos desafíos. Para hacer esto se precisa del uso de herramientas, como los simuladores de las redes. En este trabajo se presenta una definición de las VANETs, así como de sus características, una clasificación y descripción de algunos protolos comúnmente usados por estas y se realiza una investigación mediante la simulación del comportatamiento de una red, para finalmente, presentar el análisis de resultados y conclusiones del comportamiento de los protocolos AODV, DSR y DSDV, se escogen estos por ser los más usados por su rendimiento