Sterile neutrinos, dark matter, and resonant effects in ultra high energy regimes

Interest in light dark matter candidates has recently increased in the literature; some of these works consider the role of additional neutrinos, either active or sterile. Furthermore, extragalactic neutrinos have been detected with energies higher than have ever been reported before. This opens a new window of opportunities to the study of neutrino properties that were unreachable up to now. We investigate how an interaction potential between neutrinos and dark matter might induce a resonant enhancement in the oscillation probability, an effect that may be tested with future neutrino data.Comment: 11 pages, 2 figures, to be published in PL

Constraints on neutrino electric millicharge from experiments of elastic neutrino-electron interaction and future experimental proposals involving coherent elastic neutrino-nucleus scattering

In several extensions of the Standard Model of Particle Physics (SMPP), the neutrinos acquire electromagnetic properties such as the electric millicharge. Many theoretical and experimental constraints have been reported in the literature for this parameter. In this work, we first carried out a statistical analysis by using data from reactor neutrino experiments, which include elastic neutrino-electron scattering (ENES) processes, in order to obtain both individual and combined limits on the neutrino electric millicharge (NEM). Then we performed a similar calculation to show a estimate of the sensitivity of future experiments of reactor neutrinos to the NEM, by involving coherent elastic neutrino-nucleus scattering (CENNS). In the first case, the constraint on NEM achieved from a combination of all experiments studied here is $q_{\nu} \lesssim 1.5\times 10^{-12} e$ ($90\%$ C.L.), which corresponds to the same result previously reported by the GEMMA experiment. However, in the second scenario, the combined bound from different CENNS experimental proposals is $q_{\nu} \lesssim 3.5\times 10^{-13} e$ ($90\%$ C.L.), showing that the CENNS experiments could be a suitable alternative to improve the current limits on NEM.Comment: 9 pages, 4 figures (contains subfigures), and 3 tables. The title was modified and some changes were included in the tex

The reactor antineutrino anomaly and low energy threshold neutrino experiments

Short distance reactor antineutrino experiments measure an antineutrino spectrum a few percent lower than expected from theoretical predictions. In this work we study the potential of low energy threshold reactor experiments in the context of a light sterile neutrino signal. We discuss the perspectives of the recently detected coherent elastic neutrino-nucleus scattering in future reactor antineutrino experiments. We find that the expectations to improve the current constraints on the mixing with sterile neutrinos are promising. We also analyse the measurements of antineutrino scattering off electrons from short distance reactor experiments. In this case, the statistics is not competitive with inverse beta decay experiments, although future experiments might play a role when compare it with the Gallium anomaly.Comment: 9 pages, 6 figures, 1 table, matches published versio

Multitemporal and geobotanical approach in the remote detection of Greisenization areas in the Serra da Pedra Branca Granite, Goias State, Brazil

A multiseasonal analysis of LANDSAT multispectral images in CCT format permitted the mapping of lithologic facies in the Pedra Branca Granite, using geobotanical associations, which occur in the form of variations in the density of the cerrado vegetation, as well as the predominance of certain distinct vegetation species. Dry season images did not show very good results in lithological differentiation due to anomalous illumination conditions related to the low solar elevation and the homogeneity in the vegetation cover, specially the grass that becomes dry during this season. Rainy season images, on the other hand, allowed the separation of the lithological types, a fact that can be attributed to a greater differentiation among the geobotanical associations. The muscovite-granite facies with greisenization zones within the Serra da Pedra Branca were mapped. This methodology can be successfully applied to similar known granite bodies elsewhere in the Tin Province of Goias

Underlying factors promoting nestedness of bird assemblages in cays of the Jardines de la Reina archipelago, Cuba

Factores subyacentes que promueven el anidamiento de ensamblajes de aves en cayos del archipiélago de los Jardines de la Reina, Cuba La evaluación de los factores asociados a los modelos de anidamiento se ha convertido en un aspecto esencial de los estudios sobre estructuración de comunidades. Los ensamblajes de aves del archipiélago de los Jardines de la Reina presentan una estructura anidada estable, aunque sus causas permanecen sin evaluar. Se elaboró una matriz de datos de presencia y ausencia a partir de un inventario de aves obtenido en 43 cayos de este archipiélago. Se calculó el anidamiento mediante el índice NODF basado en el relleno superpuesto y decreciente. La significación del anidamiento se evaluó mediante 1.000  iteraciones de cuatro modelos nulos. Las columnas de la matriz se reordenaron para evaluar siete factores que podrían estar relacionados con el anidamiento en las comunidades de aves. Los ensamblajes de aves presentaron un modelo de anidamiento significativo (67,93) y todos los factores contribuyeron (p < 0,01) a los modelos de anidamiento de las comunidades de aves. La diversidad de hábitats y el área y el perímetro de los cayos fueron los factores que más contribuyeron a la estructura anidada. El modelo de anidamiento de los ensamblajes de aves en los Jardines de la Reina podría estar causado por la interacción de la extinción selectiva y, en menor medida, por la colonización diferencial de especies.Factores subyacentes que promueven el anidamiento de ensamblajes de aves en cayos del archipiélago de los Jardines de la Reina, Cuba La evaluación de los factores asociados a los modelos de anidamiento se ha convertido en un aspecto esencial de los estudios sobre estructuración de comunidades. Los ensamblajes de aves del archipiélago de los Jardines de la Reina presentan una estructura anidada estable, aunque sus causas permanecen sin evaluar. Se elaboró una matriz de datos de presencia y ausencia a partir de un inventario de aves obtenido en 43 cayos de este archipiélago. Se calculó el anidamiento mediante el índice NODF basado en el relleno superpuesto y decreciente. La significación del anidamiento se evaluó mediante 1.000  iteraciones de cuatro modelos nulos. Las columnas de la matriz se reordenaron para evaluar siete factores que podrían estar relacionados con el anidamiento en las comunidades de aves. Los ensamblajes de aves presentaron un modelo de anidamiento significativo (67,93) y todos los factores contribuyeron (p < 0,01) a los modelos de anidamiento de las comunidades de aves. La diversidad de hábitats y el área y el perímetro de los cayos fueron los factores que más contribuyeron a la estructura anidada. El modelo de anidamiento de los ensamblajes de aves en los Jardines de la Reina podría estar causado por la interacción de la extinción selectiva y, en menor medida, por la colonización diferencial de especies.Assessing the factors associated with nestedness patterns is a crucial aspect in studies of community structure. Bird assemblages in the Jardines de la Reina archipelago have a stable nested structure but the underlying influences have not been evaluated. We constructed a presence–absence data matrix based on a bird inventory obtained from 43 cays of this archipelago. We calculated nestedness using the NODF metric based on the overlap and decreasing fill and evaluated its significance by running 1,000 iterations of four null models. The matrix columns were rearranged to evaluate seven factors possibly related to the nestedness of bird communities. Bird assemblages exhibited a significant nested pattern (67.93) and all factors contributed (p < 0.01) to the nestedness patterns of bird communities. Habitat diversity and cay area and perimeter were the factors that contributed most to the nested structure. The nestedness pattern in the bird assemblages of the Jardines de la Reina archipelago was potentially caused by the interaction of selective extinction and differential colonization of species, with the former having a more remarkable effect

Irrigated rice area estimation using remote sensing techniques: Project's proposal and preliminary results

The development of a methodology for annual estimates of irrigated rice crop in the State of Rio Grande do Sul, Brazil, using remote sensing techniques is proposed. The project involves interpretation, digital analysis, and sampling techniques of LANDSAT imagery. Results are discussed from a preliminary phase for identifying and evaluating irrigated rice crop areas in four counties of the State, for the crop year 1982/1983. This first phase involved just visual interpretation techniques of MSS/LANDSAT images

Effects of migrations on the nestedness structure of bird assemblages in cays of the Jardines de la Reina archipelago, Cuba

Efecto de las migraciones sobre la estructura de anidamiento de los ensamblajes de aves en los cayos del archipiélago de los Jardines de la Reina, Cuba La hipótesis del subgrupo anidado plantea que, en biotas fragmentadas, las especies de los sitios empobrecidos constituyen subconjuntos no aleatorios de las especies de los sitios con mayor riqueza. El efecto de las migraciónones sobre estos modelos aún no ha sido abordado plenamente. Se compararon los estados fenológico de la comunidad durante las migraciones primaveral y otoñal. Se recogieron datos sobre las presencias y ausencias de las especies de aves en 43 cayos del archipiélago de los Jardines de la Reina. Luego se construyeron dos matrices de incidencia para los periodos otoñal y primaveral. El grado de anidamiento de las matrices se calculó mediante el índice de anidamiento basado en el relleno superpuesto y decreciente, y se evaluó su significación mediante 1.000 réplicas de cuatro modelos nulos. Los ensamblajes de aves presentaron un mayor número de especies en el periodo otoñal (67) que en el primaveral (51). También manifestaron un modelo de anidamiento significativo y estable, que fue ligeramente mayor durante el periodo primaveral. Así, las fluctuaciones estacionales debidas a los movimientos migratorios prácticamente no alteraron la estructura anidada de los ensamblajes de aves.The nested subset hypothesis states that species in fragmented, less species–rich biotas are non–random subsets of those inhabiting richer sites. The effect of migration on these models has not been yet fully addressed. We compared the phenological stages of the community during the spring and fall migrations. Presence–absence data of bird species occurring at 43 cays of the Jardines de la Reina archipelago was compiled and two incidence matrices were built for fall and spring periods. The degree of nestedness was estimated based on the overlap and decreasing fill, and its significance was assessed by means of 1,000 replicates of four null models. Bird assemblages showed a higher number of species during fall (67) than they did in spring (51). They also showed a significant and stable pattern of nestedness, although this was slightly higher in spring. Seasonal fluctuations caused by migratory movements thus barely affected the nested structure of bird assemblages.Efecto de las migraciones sobre la estructura de anidamiento de los ensamblajes de aves en los cayos del archipiélago de los Jardines de la Reina, Cuba La hipótesis del subgrupo anidado plantea que, en biotas fragmentadas, las especies de los sitios empobrecidos constituyen subconjuntos no aleatorios de las especies de los sitios con mayor riqueza. El efecto de las migraciónones sobre estos modelos aún no ha sido abordado plenamente. Se compararon los estados fenológico de la comunidad durante las migraciones primaveral y otoñal. Se recogieron datos sobre las presencias y ausencias de las especies de aves en 43 cayos del archipiélago de los Jardines de la Reina. Luego se construyeron dos matrices de incidencia para los periodos otoñal y primaveral. El grado de anidamiento de las matrices se calculó mediante el índice de anidamiento basado en el relleno superpuesto y decreciente, y se evaluó su significación mediante 1.000 réplicas de cuatro modelos nulos. Los ensamblajes de aves presentaron un mayor número de especies en el periodo otoñal (67) que en el primaveral (51). También manifestaron un modelo de anidamiento significativo y estable, que fue ligeramente mayor durante el periodo primaveral. Así, las fluctuaciones estacionales debidas a los movimientos migratorios prácticamente no alteraron la estructura anidada de los ensamblajes de aves

Set-up of Digital Image Correlation Apparatus

Digital Image Correlation (DIC) is a valuable and customizable experimental technique employed to analyze localized strain regions on materials by tracking the displacement of points on the surface of the studied material under applied stress. To investigate materials behavior, it is vital to correctly set-up the DIC apparatus so work has been done to ready the equipment to start measurements on two distinct projects. On the first project, the fatigue crack behavior of a high-strength aluminum alloy will be studied by cyclic loading, testing necessary for the safe design of aircraft parts utilizing this novel alloy. DIC will be carried out ahead of the fatigue crack and to accomplish this, a MATLAB code was developed to synchronize the loading machine with the DIC equipment and camera, and to automate the capture of images. On the second project, electronic microscopy will be utilized to carry out DIC at high resolutions to study the relationship of the microstructure of structural alloys and the strain fields generated on the material. A gold nanoparticle speckling method was adapted from literature to create a speckle pattern on the specimens with the desired length scale and density for this study. A satisfactory conclusion of the preparatory work of the DIC equipment and protocols will enable the testing to start for the two projects aforementioned