Photon-number-resolving segmented avalanche-photodiode detectors

We investigate the feasibility and performance of photon-number-resolved photodetection employing avalanche photodiodes (APDs) with low dark counts. The main idea is to split n photons over m modes such that every mode has no more than one photon, which is detected alongside propagation by an APD. We characterize performance by evaluating the purities of positive-operator-valued measurements (POVMs), in terms of APD number and photon loss.Comment: 5 pages, 7 figures, submitted for publicatio

Accretion of nonminimally coupled scalar fields into black holes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)By using a quasistationary approach, we consider the mass evolution of Schwarzschild black holes in the presence of a nonminimally coupled cosmological scalar field. The mass evolution equation is analytically solved for generic coupling, revealing a qualitatively distinct behavior from the minimal coupling case. In particular, for black hole masses smaller than a certain critical value, the accretion of the scalar field can lead to mass decreasing even if no phantom energy is involved. The physical validity of the adopted quasistationary approach and some implications of our result for the evolution of primordial and astrophysical black holes are discussed. More precisely, we argue that black hole observational data could be used to place constraints on the nonminimally coupled energy content of the Universe.8010Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Rural to urban migration is associated with increased prevalence of childhood wheeze in a Latin-American city.

INTRODUCTION: The urbanisation process has been associated with increases in asthma prevalence in urban and rural areas of low-income and middle-income countries (LMICs). However, although rural to urban migration and migration between cities are considered important determinants of this process, few studies have evaluated the effects of internal migration on asthma in urban populations of LMICs. The present study evaluated the effects of internal migration on the prevalence of wheeze in an urban area of Latin America. METHODS: We did a cross-sectional analysis of 2510 schoolchildren living in the city of Esmeraldas, Ecuador. Logistic regression was used to analyse associations between childhood wheeze and different aspects of migration among schoolchildren. RESULTS: 31% of schoolchildren were migrants. Rural to urban migrants had a higher prevalence of wheeze, (adj.OR=2.01,95% CI1.30 to 3.01, p=0.001) compared with non-migrants. Age of migration and time since migration were associated with wheeze only for rural to urban migrants but not for urban to urban migrants. Children who had migrated after 3 years of age had a greater risk of wheeze (OR 2.51, 95% CI 1.56 to 3.97, p=0.001) than non-migrants while migrants with less than 5 years living in the new residence had a higher prevalence of wheeze than non-migrants (<3 years: OR=2.34, 95% CI 1.26 to 4.33, p<0.007 and 3-5 years: OR=3.03, 95% CI 1.49 to 6.15, p<0.002). CONCLUSIONS: Our study provides evidence that rural to urban migration is associated with an increase in the prevalence of wheeze among schoolchildren living in a Latin-American city. Age of migration and time since migration were important determinants of wheeze only among migrants from rural areas. A better understanding of the social and environmental effects of internal migration could improve our understanding of the causes of the increase in asthma and differences in prevalence between urban and rural populations

Association of Trypanosoma vivax in extracellular sites with central nervous system lesions and changes in cerebrospinal fluid in experimentally infected goats

Changes in cerebrospinal fluid (CSF) and anatomical and histopathological central nervous system (CNS) lesions were evaluated, and the presence of Trypanosoma vivax in CNS tissues was investigated through PCR. Twelve adult male goats were divided into three groups (G): G1, infected with T. vivax and evaluated during the acute phase; G2, infected goats evaluated during the chronic phase; and G3, consisting of non-infected goats. Each goat from G1 and G2 was infected with 1.25 × 105 trypomastigotes. Cerebrospinal fluid (CSF) analysis and investigation of T. vivax was performed at the 15th day post-infection (dpi) in G1 goats and on the fifth day after the manifestation of nervous system infection signs in G2 goats. All goats were necropsied, and CNS fragments from G1 and G2 goats were evaluated by PCR for the determination of T. vivax. Hyperthermia, anemia and parasitemia were observed from the fifth dpi for G1 and G2, with the highest parasitemia peak between the seventh and 21st dpi. Nervous system infection signs were observed in three G2 goats between the 30th and 35th dpi. CSF analysis revealed the presence of T. vivax for G2. Meningitis and meningoencephalitis were diagnosed in G2. PCR were positive for T. vivax in all the samples tested. In conclusion, T. vivax may reach the nervous tissue resulting in immune response from the host, which is the cause of progressive clinical and pathological manifestations of the CNS in experimentally infected goats

An RF Approach to Modelling Gallium Nitride Power Devices Using Parasitic Extraction

This paper begins with a comprehensive review into the existing GaN device models. Secondly, it identifies the need for a more accurate GaN switching model. A simple practical process based on radio frequency techniques using Vector Network Analyser is introduced in this paper as an original contribution. It was applied to extract the impedances of the GaN device to develop an efficient behavioural model. The switching behaviour of the model was validated using both simulation and real time double pulse test experiments at 500 V, 15 A conditions. The proposed model is much easier for power designers to handle, without the need for knowledge about the physics or geometry of the device. The proposed model for Transphorm GaN HEMT was found to be 95.2% more accurate when compared to the existing LT-Spice manufacturer model. This work additionally highlights the need to adopt established RF techniques into power electronics to reduce the learning curve while dealing with these novel high-speed switching devices.</jats:p

Implementation of Non-Isolated Zeta-KY Triple Port Converter for Renewable Energy Applications

This paper proposes a three-port Zeta-KY dc-dc converter which is fed with hybrid sources like photovoltaic (PV) cells and batteries. The converter proposed here is a multi-input single-output (MISO) structure which harnesses the benefits of Zeta and KY converters. The combination of these converters is highly advantageous since the Zeta converter provides lesser output voltage ripples with high gain and the KY converter topology suits well for withstanding load transients. The KY converter used in this research work is subjected to a topological change to facilitate bidirectional power flow. The bidirectional flow is essential to save the excess power in PV source in batteries during low load conditions. This novel multiport topology with bidirectional facility is first of its kind and has not been discussed earlier in the research arena. In the proposed work, two control algorithms are developed and deployed: the first one ensures the maximum power extraction from the PV and the second one maintains constant dc bus voltage and manages bidirectional power flow. MATLAB Simulink and hardware prototype of the proposed system has been realized for a 72 V dc bus and a 500 W electric vehicular drive. The simulation and experimental results reveal that the proposed system is viable for medium power electric shuttle applications. The proposed system is subjected to various test cases and it is observed that the source and load intermittencies are catered very well by the proposed three port Zeta-KY converter. The developed multiport converter is feasible for renewable energy applications