997 resultados para variable-range hopping
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Bat species of the genus Centronycteris are some of the rarest Neotropical Emballonuridae and fewer than 50 specimens have been deposited in scientific collections. The aim of this study is to extend the distribution of Centronycteris maximiliani. Three C. maximiliani specimens were recorded in the Brazilian Amazonia, providing the first record of the species for the state of Rondônia, the southernmost record of the species for the Amazon biome in Brazil, and an additional record for the state of Pará. Although these new records of C. maximiliani reinforce the idea that this species is widely distributed throughout the Amazon biome, its low capture rate reflects the rarity of this species, since only three specimens were collected during three to four year field effort.
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The properties of surface plasmon-polaritons (SPPs) in graphene are discussed and several possible ways of coupling electromagnetic radiation in the terahertz (THz) spectral range to this type of surface waves are described: (i) the attenuated total reflection (ATR) method employing a prism, (ii) graphene-based gratings or graphene monolayers with modulated conductivity, (iii) a metal stripe on top of the graphene layer, and (iv) a nanoparticle located above it. Potentially interesting for applications SPP effects, such as switching, modulation and polarization of THz radiation, as well as its enhanced absorption in graphene, are considered. The discussion also concerns the impact of the nonlinear properties of graphene, such as optical bistability.
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Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e de Computadores
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Dissertação de mestrado integrado em Engenharia de Materiais
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The aim of this paper is to predict time series of SO2 concentrations emitted by coal-fired power stations in order to estimate in advance emission episodes and analyze the influence of some meteorological variables in the prediction. An emission episode is said to occur when the series of bi-hourly means of SO2 is greater than a specific level. For coal-fired power stations it is essential to predict emission epi- sodes sufficiently in advance so appropriate preventive measures can be taken. We proposed a meth- odology to predict SO2 emission episodes based on using an additive model and an algorithm for variable selection. The methodology was applied to the estimation of SO2 emissions registered in sampling lo- cations near a coal-fired power station located in Northern Spain. The results obtained indicate a good performance of the model considering only two terms of the time series and that the inclusion of the meteorological variables in the model is not significant.
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Dissertação de mestrado em Genética Molecular
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Existe una clara necesidad de obtener información científica y comprensible sobre la distribución actual, abundancia y el estado de conservación del cóndor andino (Vultur gryphus) en Córdoba. Las justificaciones de ello incluyen: 1) la información disponible es muy limitada y fragmentada, y es insuficiente para las decisiones de manejo, 2) el aparente aislamiento de la población de cóndor andino de Córdoba respecto a la principal distribución de la especie a lo largo de los Andes sudamericanos, hecho que merece especial consideración, 3) indicaciones de que la especie muestra signos de declinación a lo largo de su rango de distribución, y 4) el valor de la especie como ave carismática y componente clave de atracción turística en la provincia de Córdoba. Esta propuesta pretende llenar el vacío de información existente mediante los siguientes objetivos específicos: 1) relevar la distribución del cóndor andino en Córdoba, 2) evaluar el tamaño poblacional de la especie a través de relevamientos en sus colonias no reproductivas, y 3) obtener la información disponible de la literatura publicada, material arqueológico y de informantes calificados. Los métodos incluyen: a) relevamientos sistemáticos a campo, b) conteos poblacionales en aquellos sitios identificados como colonias no reproductivas de la especie, c) revisión bibliográfica, y d) entrevistas a informantes selectos como ornitólogos, guías turísticos, pobladores rurales locales clave, etc. La información obtenida proveerá una línea de base de la situación actual del cóndor andino en Córdoba, como así también los criterios necesarios y la metodología para un monitoreo continuado de la especie en el territorio provincial.
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This project explored the possibility of harvesting marketable foliage stems in addition to producing timber from plantations of Larix leptolepis, Cupressus macrocarpa ‘Goldcrest’ and Tsuga heterophylla. Data recorded from trial sites included both growth parameters, in the form of height and diameter increments, and production parameters in the form of foliage stem yields. Results varied with species and site type. In many cases, results achieved appear to have been influenced more by the biology of the trees than by the treatments alone. Trials were also established to investigate methods of managing old or over grown Abies procera Christmas tree plantations for forest foliage production. Shelf life testing and market research into the domestic trade of forest foliage were also conducted over the course of the project. Recommendations for managing forest plantations for foliage production as well as a general discussion on the industry are presented in this report.
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Dieselmotor, Brennverfahren, Ventilsteuerung, Ladungswechsel
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v.20:no.27(1937)
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Annual patterns of calling and breeding activity of 38 anuran species were studied at Serra do Caraça, an 11,233 ha reserve located in a contact zone between Cerrado and Atlantic forest at the southern Espinhaço range, southeastern Brazil. Five patterns were evident: (1) species that call year-round or nearly year-round with larger aggregations generally observed in the rainy months, (2) species with opportunistic calling activity associated with rainfall during the wettest months of the year, (3) winter species, (4) explosive breeders with intense calling activity triggered by heavy rains during the rainy season or only in the beginning of the rainy season, and (5) summer species with variable breeding seasons. Both the monthly number of species with calling males and the monthly number of species that showed the maximum class of calling males were positively correlated with both mean monthly temperature and monthly precipitation.