Magnetic, structural, and transport properties at very high temperature in manganites

AbstractMagnetic, structural, and electric transport measurements at high temperatures were carried out on La1−xCaxMnO3; x=0.20, 0.25, 0.30, 0.34, 0.40, and 0.45. All samples show a first-order structural phase transition from orthorhombic Pnma to rhombohedral R3¯c space group at TR–O. Magnetic susceptibility measurements show that the Curie–Weiss law is strictly obeyed in the rhombohedral phase as opposed to the orthorhombic phase where the effective magnetic moment has a temperature dependence. The electrical resistivity is well described by the small polaron hopping mechanism in the samples up to x=0.34. As the charge carriers are introduced into the system (x=0.40 and 0.45), this mechanism of hopping ceases to be valid. The value of Grüneisen parameter obtained through analysis of high-resolution X-ray powder diffraction as a function of temperature increases abruptly for the sample with x=0.40. This is consistent with an increase in bending and stretchinglike frequency modes observed by Raman spectroscopy

Avaliação do Sentinel-2, NDVI e MLME para Mapeamento do Uso e Cobertura da Terra

A floresta amazônica é considerada um dos maiores reservatórios de carbono da Terra. No entanto, mudanças antrópicas indiscriminadas no uso e cobertura da terra, como a conversão da floresta em áreas agrícolas e pastagens, provocam grandes impactos ambientais na floresta. A utilização de técnicas que auxiliam o mapeamento do uso e cobertura da terra se torna cada vez mais necessária. Índices como o NDVI (Índice de Vegetação por Diferença Normalizada) e MLME (Modelo Linear de Mistura Espectral) são amplamente utilizados para estudos da vegetação, por permitirem analisar e realçar parâmetros e feições em imagens de sensoriamento remoto. Desse modo, o objetivo deste trabalho foi avaliar o desempenho do mapeamento do uso e cobertura da terra (LULC), utilizando dados do satélite Sentinel-2B, adicionado com o índice de vegetação NDVI e com o MLME, utilizando o classificador Random Forest (RF). Para a realização deste estudo, foram utilizadas imagens do sensor MSI do Sentinel-2B e calculados os índices NDVI e MLME, derivados da imagem Sentinel-2B. A partir da segmentação da imagem, foi realizada a extração de atributos para cada segmento. A classificação foi realizada pelo método RF e a validação foi realizada através da simulação de Monte Carlo observando-se os valores de índice Kappa e Acurácia Global (AG). Para avaliar a diferença obtida com a adição das variáveis NDVI e MLME, quatro cenários de classificação foram realizados. Notou-se que os cenários apresentaram resultados semelhantes de índice Kappa e AG, não apresentando diferença significativa entre eles. A utilização das faixas espectrais do Sentinel-2B/MSI se mostrou uma boa alternativa para realizar o mapeamento do uso e cobertura da terra, facilitando as etapas de processamento. No entanto, a inclusão do MLME para a separação da classe Floresta Degradada (FD), se mostrou significativa. Além disso, observou-se que a utilização do classificador RF apresenta bons resultados para o mapeamento do uso e cobertura da terra

Rescuing the Brazilian Agave breeding program: morphophysiological and molecular characterization of a new germplasm

Agaves have been a valuable resource in dryland areas for centuries, providing fibers (sisal), food, and beverages. However, the advent of synthetic fibers has led to a decrease in research on Agave, resulting in the cessation of breeding programs in Brazil. With the rise of climate change, there is renewed interest in Agave for its potential as a biofuel feedstock in semiarid regions. Since 2016, we have been collecting Agave accessions throughout the country and retrieving what is left of Brazil’s original breeding program to establish a new germplasm bank. Here, we evaluated 21 of those accessions growing in the field. We used molecular markers and morphophysiological traits to characterize the plants. Based on the Mayahuelin molecular marker, we were able to reconstruct a phylogeny for the Brazilian accessions. The morphophysiological traits explained 34.6% of the phenotypic variation in the dataset, with physiological traits such as leaf water content, effective quantum efficiency of photosystem II (ΦPSII), and specific leaf mass (SLM) as the most significant traits. Specifically, we evaluated nine Agave species and found that the physiological traits, rather than the morphological ones, were the most significant. Leaf water content was negatively correlated with specific leaf mass, which could be used as a marker for selecting cultivars with higher biomass accumulation. Interestingly, ΦPSII and chlorophyll content were negatively correlated, suggesting photochemical adaptations throughout the rosette. Molecular and phenotypic data suggest that A. amaniensis, which is frequently considered a synonym of A. sisalana, is effectively another species. Overall, this study provides valuable information on the physiological traits of Brazilian Agave accessions and is a starting point for selecting more productive and climate-resilient cultivars for biorenewables production

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

The complete genome sequence of Chromobacterium violaceum reveals remarkable and exploitable bacterial adaptability

Chromobacterium violaceum is one of millions of species of free-living microorganisms that populate the soil and water in the extant areas of tropical biodiversity around the world. Its complete genome sequence reveals (i) extensive alternative pathways for energy generation, (ii) ≈500 ORFs for transport-related proteins, (iii) complex and extensive systems for stress adaptation and motility, and (iv) wide-spread utilization of quorum sensing for control of inducible systems, all of which underpin the versatility and adaptability of the organism. The genome also contains extensive but incomplete arrays of ORFs coding for proteins associated with mammalian pathogenicity, possibly involved in the occasional but often fatal cases of human C. violaceum infection. There is, in addition, a series of previously unknown but important enzymes and secondary metabolites including paraquat-inducible proteins, drug and heavy-metal-resistance proteins, multiple chitinases, and proteins for the detoxification of xenobiotics that may have biotechnological applications

Electrochromism in thin film composites

Neste trabalho calculamos inicialmente as propriedades ópticas de filmes compósitos de Me-NiO e Me-CoO, sendo os metais Me = Au, Ag, Cu, Ni, Pd e Pt, a partir da teoria de meio efetivo de Maxwell Garnett. Este estudo teórico possibilitou avaliar a viabilidade de se obter experimentalmente um material colorido na região do espectro visível, com absorção seletiva numa estreita faixa de comprimentos de onda. Os resultados mostraram que o candidato ideal para tal fim é o compósito a base de Au. A partir deste resultado iniciou-se o crescimento de filmes finos compósitos de Au-NiO e Au-CoO, utilizando diferentes estratégias experimentais: (i) deposição por DC magnetron sputtering reativo, (ii) deposição do filme de NiO, por DC magnetron sputtering reativo e Au pelos métodos de sol-gel e dip coating e (iii) deposição de ambos os filmes, NiOxHy e Au, por sol-gel e dip coating. Os resultados mostraram uma seletividade pequena (-5-10%) nos filmes crescidos pelo método de sputtering, devido ao caráter atomístico desse tipo de técnica, que conduz à formação de pequenos aglomerados de Au (menores que -3 nm), ao invés de agregados com tamanhos da ordem de algumas dezenas de nanômetros, obtidos facilmente pelo método sol-gel. O crescimento na forma de multicamadas proporciona uma melhor seletividade, em torno de 1 5%. Pós-tratamentos térmicos em filmes compósito s obtidos unicamente por sputtering induzem a aglomeração do Au, mas destroem as propriedades eletrocrôrnicas. No caso de filmes de Au crescidos por sol-gel, a seletividade espectral, decorrente da presença do Au aumenta, indo de 15% a 20% em filmes depositados sobre a matriz óxida crescida por sputtering e por sol-gel, respectivamente. Mediante processos eletroquímicos, os filmes de NiOxHy crescidos por sol-gel e dip coating apresentaram os melhores resultados de variação de transmitância (70%), devido à maior porosidade desses filmes.In this work we initially calculated the optical properties of cermet films of Me-NiO and Me-CoO, being the metals Me = Au, Ag, Cu, Ni, Pd and Pt, by means of the Maxwell Garnett effective medium theory. This theoretical study allowed evaluating the viability to obtain, experimentally, a colored material in the visible spectrum region, with selective absorption in a narrow range of wavelengths. The results showed that the ideal candidate for such goal is the Au cermet. Looking at this result, the growth of Au-NiO and Au-CoO thin films was initiated using different experimental strategies: (i) deposition by reactive DC magnetron sputtering, (ii) deposition of the NiO, film by reactive DC magnetron sputtering and Au by the sol-gel and dip coating methods and (iii) deposition of both films, NiOxHy and Au, by sol-gel and dip coating. The films grown by sputtering showed a small selectivity (-5-10%), due to the atomistic character of this type of technique. It leads to the formation of small clusters of Au (smaller than -3 nrn), instead of aggregates with sizes of the order of some tenths of nanometers, easily obtained by the sol-gel method. Better selectivity, around 15%, is obtained in films deposited as multilayers. Post thermal annealing of the cermet films grown by sputtering induces the agglomeration of Au, but destroys the electrochromic properties. In the case of Au films grown by sol-gel, the spectral selectivity increases, due to the presence of Au, going from 15% to 20% in films deposited on the oxide matrix, deposited by sputtering and sol-gel, respectively. Under electrochemical processes, the NiOxHy films grown by sol-gel and dip coating presented the highest transmission variation (70%), due to larger porosity of these films

Evaluation of polarimetry and interferometry of sentinel-1A SAR data for land use and land cover of the Brazilian Amazon Region

Synthetic aperture radar (SAR) data has been an alternative for monitoring ground targets, especially in areas with cloud cover. This study evaluates the potential of Sentinel-1A attributes for mapping land use and land cover (LULC) in a region of the Brazilian Amazon, using two different machine learning classifiers: Random Forest (RF) and Support Vector Machine (SVM). Different scenarios were used that combined backscattering, polarimetry, and interferometry to the classification process, which was divided into two phases to improve the results. The RF shows superiority over the SVM for almost all scenarios for the two phases of the mapping. The scenario with all data, presented the best results with both classifiers. The final maps with RF and SVM, obtained a global accuracy of 82.7% and 74.5%, respectively. This study demonstrated the potential of Sentinel-1 to map LULC classes in the Amazon region using a classification in two phases

Electrochemical capacitance spectroscopy and capacitive relaxation of the changeover process in iron hexacyanoferrate molecular compound

In this work it was proposed the use electrochemical capacitance spectroscopy (ECS) to evaluate the storage process during changeover in FeHCF compound. The approach is equivalent to electrochemical impedance spectroscopy (EIS) albeit from such analysis it was possible to focus attention on the capacitive and dielectric relaxation instead of the dispersive relaxation related to charge transfer. From such approach it was possible to obtain complementary information on the role played by [Fe(2+)(CN)(6)](4-) vacancies during the changeover process. It was observed that Fe(3+)(NC)(5)OH(-) clusters located in these vacancies mediate an electronic and ionic coupled trapping/detrapping process giving rise to what was considered an electrochemical dipolar relaxation whose K(+) ionic specie with Fe(3+)(NC)(5)OH(-) clusters are the key entities in controlling the general process. The capacitive response reaches its maximum value at the changeover due to saturation of the electronic occupation at Fe(3+)(NC)(5)OH(-) clusters. The nature and the dynamics of the capacitive relaxation process were either discussed. (C) 2009 Elsevier Ltd. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP