Giant optical anisotropy in a single InAs quantum dot in a very dilute quantum-dot ensemble

We present the experimental evidence of giant optical anisotropy in single InAs quantum dots. Polarization-resolved photoluminescence spectroscopy reveals a linear polarization ratio with huge fluctuations, from one quantum dot to another, in sign and in magnitude with absolute values up to 82%. Systematic measurements on hundreds of quantum dots coming from two different laboratories demonstrate that the giant optical anisotropy is an intrinsic feature of dilute quantum-dot arrays.Comment: submitted to Applied Physics Letter

Supercapacitors based on AC/MnO2 deposited onto dip-coated carbon nanofiber cotton fabric electrodes

This work introduces the preparation of flexible carbon composite electrodes based on the top-down approach starting from the dip-coating of carbon nanofibers (CNFs) onto a cotton fabric. On these so-obtained conductive cotton fabrics, further layers of activated carbon and manganese oxide (MnO2) materials were subsequently added to enhance the electrochemical performances of negative and positive electrodes. At the end, two different types of asymmetric supercapacitors (SCs) were assembled with those textile electrodes by using porous paper and Nafion-Na ion-exchange membranes as separators. The different SCs were electrochemically characterized by means of cyclic voltammetry (CV), galvanostatic charge/discharge (G–CD) and electrochemical impedance spectroscopy (EIS). These hybrid carbon-based textile SCs exhibited capacitance performance of 138 and 134 F g–1 with the porous paper and Nafion membrane, respectively, and low self-discharge rates. Furthermore, in this study is considered the combination of two methods (cycling and floating) for studying the long-term durability tests of SCs. In particular, the floating methodology utilizes much more harsh conditions than the common cycling based on G-CD tests at high currents usually discussed in literature. The solid-state (Nafion membrane) hybrid device demonstrated very long durability with 10 K cycles and additional 270 h at a constant voltage of 1.6 V. In summary, the hybrid SCs fabricated with low cost materials and simple methodologies reported in this study showed very promising results for flexible energy storage applications.This work was partly financed by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology (project POCI-01-0145-FEDER-007136). A.J. Paleo acknowledges the European COST Action CA15107- Multi-Functional Nano-Carbon Composite Materials Network (MultiComp) for its support with a Short Term Scientific Mission (STSM) grant at CNR-ITAE of Messina

Células de linhagem McCoy como um possível modelo contendo receptores CD4+ para estudos da replicação do HIV

Several studies have recently shown the use of recombinant rabies virus as potential vector-viral vaccine for HIV-1. The sequence homology between gp 120 and rabies virus glycoprotein has been reported. The McCoy cell line has therefore been used to show CD4+ or CD4+ like receptors. Samples of HIV-1 were isolated, when plasma of HIV-1 positive patients was inoculated in the McCoy cell line. The virus infection was then studied during successive virus passages. The proteins released in the extra cellular medium were checked for protein activity, by exposure to SDS Electrophoresis and blotting to nitro-cellulose filter, then reacting with sera of HIV positive and negative patients. Successive passages were performed, and showed viral replication, membrane permeabilization, the syncytium formation, and the cellular lysis (cytopathic effect). Flow cytometry analysis shows clear evidence that CD4+ receptors are present in this cell line, which enhances the likelihood of easy isolation and replication of HIV. The results observed allow the use of this cell line as a possible model for isolating HIV, as well as for carrying out studies of the dynamics of viral infection in several situations, including exposure to drugs in pharmacological studies, and possibly studies and analyses of the immune response in vaccine therapies.Recentes estudos demonstraram o uso do vírus raiva como modelo vetor para produzir vacinas expressando as glicoproteínas do vírus HIV-1. A homologia na seqüência entre gp120 do vírus HIV-1 e a glicoproteína G do vírus rábico já foi previamente relatada. Devido a estes fatos a linhagem de célula McCoy utilizada com sucesso para a replicação do vírus rábico foi utilizada para demonstrar a replicação do HIV-1. Amostra de HIV-1 foi isolada de plasma de um paciente soro positivo e inoculada em células de linhagem McCoy e então a infecção viral foi estudada em passagens sucessivas do vírus nesta célula. As proteínas liberadas no meio extra celular foram analisadas quanto a atividade biológica pela técnica de eletroforese em gel de poliacrilamida e imunotransferência em membrana de nitro-celulose reagindo com soros positivos para HIV-1 e soros de pacientes negativos. As passagens sucessivas do HIV-1 em células demonstraram a replicação viral, o aumento da permeabilidade da membrana citoplasmática, a formação de sinsício e lise celular. Análises com citometria de fluxo mostraram com clara evidência a presença de receptores CD4+ o que possivelmente deve ser a causa que possibilita a facilidade do isolamento e replicação do vírus HIV-1 nesta célula. Concluindo os resultados observados permitem utilizar esta linhagem celular como um possível modelo para isolamentos de HIV, bem como realizar estudos da dinâmica de infecção viral em diversas situações inclusive de exposição a drogas em estudos farmacológicos, e talvez estudos e análises da resposta imune em terapias vacinais

Spontaneous symmetry breaking in amnestically induced persistence

We investigate a recently proposed non-Markovian random walk model characterized by loss of memories of the recent past and amnestically induced persistence. We report numerical and analytical results showing the complete phase diagram, consisting of 4 phases, for this system: (i) classical nonpersistence, (ii) classical persistence (iii) log-periodic nonpersistence and (iv) log-periodic persistence driven by negative feedback. The first two phases possess continuous scale invariance symmetry, however log-periodicity breaks this symmetry. Instead, log-periodic motion satisfies discrete scale invariance symmetry, with complex rather than real fractal dimensions. We find for log-periodic persistence evidence not only of statistical but also of geometric self-similarity.Comment: 4 pages, 2 color fig

Evaluation of peak inspiratory pressure, tidal volume and respiratory rate during ventilation of premature lambs using a self-inflating bag

OBJECTIVE: To evaluate the peak inspiratory pressure, tidal volume and respiratory rate achieved during manual ventilation of premature lambs, using a self-inflating bag. METHODS: In this descriptive, experimental study, five pairs of physicians, selected at random among 35 neonatologists working at a neonatal intensive care unit and with experience in the resuscitation of newborn infants, ventilated five intubated premature lambs using a self-inflating bag. Pressure and flow monitor signals were passed through a transducer and digitized for recording and analysis. Tidal volume and pressure curves were obtained from the integral of flow rate, at peak, during the last 50 seconds of every fifth minute, and analyzed. RESULTS: Median pressure was 39.8 (IQ25-75% 30.2-47.2) cmH2O; being below 20 in 1.1% of cases and above 40 in 49.1%. Seven out of 10 physicians produced more than six pressure peaks of over 40 cmH2O. Median tidal volume/kg was 17.8 (IQ25-75% 14.1-22.4) mL, being below 5 mL in 0.1% of cases and greater than or equal to 20 mL in 37.7%. All of the physicians propelled five or more ventilation cycles with tidal volume/kg of 20 mL or more. Respiratory rate was between 30 and 60 cycles/minute in 65.9% of cases, being below 30 in 6.8% of cases and over 60 in 27.3% of cases. CONCLUSIONS: There was major variation in peak inspiratory pressure and tidal volume/kg values, which were in many cases elevated, attaining levels that habitually cause biotrauma, while respiratory rates were adequate in the majority of cases.OBJETIVO: Avaliar o pico de pressão inspiratória, o volume corrente e a freqüência respiratória obtidos durante ventilação manual de carneiros prematuros, utilizando balão auto-inflável. MÉTODOS: Estudo experimental descritivo em que cinco duplas de médicos selecionados aleatoriamente entre 35 neonatologistas que trabalham em unidade de terapia intensiva neonatal e experientes em reanimação de recém-nascidos ventilaram cinco carneiros prematuros intubados, utilizando balão auto-inflável. Os sinais de pressão e fluxo eram captados, convertidos por meio de transdutores e digitalizados para armazenamento e análise. Foram avaliadas curvas de pressão e de volume corrente, este a partir da integral do fluxo, em suas medidas de pico, nos 50 segundos finais de cada 5 minutos. RESULTADOS: A mediana da pressão foi de 39,8 (IQ25-75% 30,2-47,2) cmH2O; foi menor que 20 em 1,1% das vezes e maior que 40 em 49,1%. Sete em 10 médicos propiciaram mais de seis picos de pressão maiores que 40 cmH2O. A mediana do volume corrente/kg foi de 17,8 (IQ25-75% 14,1-22,4) mL, sendo menor que 5 mL em 0,1% das vezes e igual ou maior que 20 mL em 37,7%. Todos os médicos impuseram cinco ou mais ciclos ventilatórios com volume corrente/kg de 20 mL ou mais. A freqüência situou-se entre 30 e 60 ciclos/minuto em 65,9% das vezes, sendo menor que 30 em 6,8% e maior que 60 em 27,3% das vezes. CONCLUSÃO: Ocorreu grande variabilidade nos valores do pico de pressão inspiratória e do volume corrente/kg, sendo muitas vezes elevados e alcançando níveis indutores de biotrauma; para a freqüência respiratória, os valores foram adequados na maioria das vezes.Universidade de BrasíliaUnBUniversidade Federal de São Paulo (UNIFESP)UnB Hospital Universitário da UnBUniversidade de São Paulo Faculdade de Medicina Instituto da Criança do Hospital das ClínicasUNIFESPSciEL

Measurement of the 70Ge(n,γ) cross section up to 300 keV at the CERN n_TOF facility

Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weak component of the slow neutron capture processes, which occurs in massive stars. The (n,γ) cross section on 70Ge, which is mainly produced in the s process, was measured at the neutron time-of-flight facility n_TOF at CERN. Resonance capture kernels were determined up to 40 keV neutron energy and average cross sections up to 300 keV. Stellar cross sections were calculated from kT =5 keV tokT =100 keV and are in very good agreement with a previous measurement by Walter and Beer (1985) and recent evaluations. Average cross sectionsareinagreementwithWalterandBeer(1985)overmostoftheneutronenergyrangecovered,whilethey aresystematicallysmallerforneutronenergiesabove150keV.Wehavecalculatedisotopicabundancesproduced in s-process environments in a 25 solar mass star for two initial metallicities (below solar and close to solar). While the low metallicity model reproduces best the solar system germanium isotopic abundances, the close to solar model shows a good global match to solar system abundances in the range of mass numbers A=60–80.Austrian Science Fund J3503Adolf Messer Foundation ST/M006085/1European Research Council ERC2015-StGCroatian Science Foundation IP-2018-01-857

Splitting the voter criticality

Recently some two-dimensional models with double symmetric absorbing states were shown to share the same critical behaviour that was called the voter universality class. We show, that for an absorbing-states Potts model with finite but further than nearest neighbour range of interactions the critical point is splitted into two critical points: one of the Ising type, and the other of the directed percolation universality class. Similar splitting takes place in the three-dimensional nearest-neighbour model.Comment: 4 pages, eps figures include

AVALIAÇÃO DA VULNERABILIDADE NATURAL DO SOLO EM ÁREAS AGRÍCOLAS: SUBSÍDIO À AVALIAÇÃO DO RISCO DE CONTAMINAÇÃO DO LENÇOL FREÁTICO POR AGROQUÍMICOS

Procurou-se mostrar que a vulnerabilidade natural do solo é um parâmetro fundamental nos estudos de avaliação de riscos ambientais, sobretudo em áreas de grande fragilidade, como as áreas de recarga dos aqüíferos sedimentares. Para esse estudo foi adotada uma área típica de recarga direta do Aqüífero Guarani, caracterizada pela microbacia do Córrego do Espraiado, localizada na região de Ribeirão Preto/SP (Brasil). Os procedimentos consistiram na integração dos parâmetros condutividade hidráulica, declividade e profundidade do lençol freático dos principais solos da área objeto de estudo . A condutividade hidráulica foi determinada com a adoção do método da coluna saturada, com valores considerados a partir de estimativa classificada em baixa, média e alta. Nessa estimativa, levou-se em conta a integração dos dados de textura, estrutura, estabilidade de agregados e profundidade do solo, que foram submetidos a tratamento estatístico para validação do método proposto. As correlações foram diretas entre condutividade hidráulica medida e condutividade hidráulica estimada. A declividade da área foi obtida a partir de mapas planialtimétricos, em escala 1:10.000, que permitiram o agrupamento em três classes: baixa, suave e acentuada. Seqüencialmente, foi estabelecida relação matricial entre as classes de condutividade hidráulica e as de declividade, resultando na classificação relativa dos potenciais de infiltração e de escoamento superficial da água para toda a microbacia. Concluiu-se que essas informações combinadas com aquelas relativas à condutividade hidráulica, declividade do terreno e profundidade do solo permitiram, de forma satisfatória, estimar em três classes ( baixa, média e alta) a vulnerabilidade natural dos solos representativos das áreas de recarga do Aqüífero Guarani na região estudada. NATURAL VULNERABILITY OF SOIL IN AGRICULTURAL AREAS: SUBVENTION OF CONTAMINATION RISK ASSESSMENT OF GROUNDWATER BY AGROCHEMICALS Abstract The natural vulnerability of soil is a fundamental parameter in the studies of ambiental risk assessment, mainly in areas of great fragility as recharge areas of sedimentary aquifers. For this study it was adopted one typical area of direct recharge from Guarani aquifer, characterized by Espraiado watershed, localized in Ribeirão Preto region in São Paulo state, Brazil. The procedures consisted in the integration of the parameters hydraulic conductivity, declivity and depth of groundwater from soils of the area in study. The hydraulic conductivity was determined by the method of saturated column, with values considered from a estimation classified in low, medium and high. In this estimation, the integration of texture, structure, aggregate stability and soil depth data, which were submitted to statistical treatment for validation of the proposed method. The area declivity was obtained from planialtimetric maps with scale 1:10000, which allowed grouping in three classes: low, smooth and pronounced. Sequentially, it was established a matricial relation between the classes of hydraulic conductivity and declivity, resulting in the relative classification of infiltration potentials and superficial water flow for all watershed. It was concluded that this information combined to those relative to hydraulic conductivity, soil declivity and depth allowed, in a satisfactory way, to estimate in three classes (low, medium and high), the natural vulnerability of soils representatives of recharge areas of Guarani aquifer in the region studied