Fano Resonances In The Excitation Spectra Of Semiconductor Quantum Wells

Fano resonances are observed in the photoluminescence excitation spectra of GaAs-AlAs quantum wells. They originate from the Coulomb interaction that couples a discrete state and a continuum of excitonic states belonging to different pairs of conduction and valence subbands. This interpretation is supported by our calculations and by the behavior of the excitonic line shape in the presence of a magnetic field applied perpendicular to the layers. © 1994 The American Physical Society.4985757576

Global priorities for conservation across multiple dimensions of mammalian diversity

Conservation priorities that are based on species distribution, endemism, and vulnerability may underrepresent biologically unique species as well as their functional roles and evolutionary histories. To ensure that priorities are biologically comprehensive, multiple dimensions of diversity must be considered. Further, understanding how the different dimensions relate to one another spatially is important for conservation prioritization, but the relationship remains poorly understood. Here, we use spatial conservation planning to (i) identify and compare priority regions for global mammal conservation across three key dimensions of biodiversity-taxonomic, phylogenetic, and traits-and (ii) determine the overlap of these regions with the locations of threatened species and existing protected areas. We show that priority areas for mammal conservation exhibit low overlap across the three dimensions, highlighting the need for an integrative approach for biodiversity conservation. Additionally, currently protected areas poorly represent the three dimensions of mammalian biodiversity. We identify areas of high conservation priority among and across the dimensions that should receive special attention for expanding the global protected area network. These high-priority areas, combined with areas of high priority for other taxonomic groups and with social, economic, and political considerations, provide a biological foundation for future conservation planning efforts

Application of Constructivist Grounded Theory in Nursing Research

Grounded Theory is a qualitative research method for collecting and analysing data and results into a substantive theory that is a theoretical interpretation of a delimited problem in a specific area of knowledge. In nursing, it allows to understand the process of social interaction and how the nursing team works in everyday situations. In this study we propose, based on the theoretical framework of Kathy Charmaz, to present the procedures for the application of the constructivist Grounded Theory in nursing research. Among these are the collection and analysis of concurrent data, constant comparison at all levels of analysis, initial, focused and axial coding, conducting memos, among other resources, construction of categories, evaluation and development of the theory

Ca2+ Sparks and Embers of Mammalian Muscle. Properties of the Sources

Ca2+ sparks of membrane-permeabilized rat muscle cells were analyzed to derive properties of their sources. Most events identified in longitudinal confocal line scans looked like sparks, but 23% (1,000 out of 4,300) were followed by long-lasting embers. Some were preceded by embers, and 48 were “lone embers.” Average spatial width was ∼2 μm in the rat and 1.5 μm in frog events in analogous solutions. Amplitudes were 33% smaller and rise times 50% greater in the rat. Differences were highly significant. The greater spatial width was not a consequence of greater open time of the rat source, and was greatest at the shortest rise times, suggesting a wider Ca2+ source. In the rat, but not the frog, spark width was greater in scans transversal to the fiber axis. These features suggested that rat spark sources were elongated transversally. Ca2+ release was calculated in averages of sparks with long embers. Release current during the averaged ember started at 3 or 7 pA (depending on assumptions), whereas in lone embers it was 0.7 or 1.3 pA, which suggests that embers that trail sparks start with five open channels. Analysis of a spark with leading ember yielded a current ratio ranging from 37 to 160 in spark and ember, as if 37–160 channels opened in the spark. In simulations, 25–60 pA of Ca2+ current exiting a point source was required to reproduce frog sparks. 130 pA, exiting a cylindric source of 3 μm, qualitatively reproduced rat sparks. In conclusion, sparks of rat muscle require a greater current than frog sparks, exiting a source elongated transversally to the fiber axis, constituted by 35–260 channels. Not infrequently, a few of those remain open and produce the trailing ember

Determinação de valores de composição química e da energia metabolizável de ingredientes para aves.

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Efeito do tipo de alojamento, da inseminação artificial e do genótipo sobre características produtivas em matrizes de frangos de corte.

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