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Interactions between humans, diseases, and the environment take place across a range of temporal and spatial scales, making accurate, contemporary data on human population distributions critical for a variety of disciplines. Methods for disaggregating census data to finer-scale, gridded population density estimates continue to be refined as computational power increases and more detailed census, input, and validation datasets become available. However, the availability of spatially detailed census data still varies widely by country. In this study, we develop quantitative guidelines for choosing regionally-parameterized census count disaggregation models over country-specific models. We examine underlying methodological considerations for improving gridded population datasets for countries with coarser scale census data by investigating regional versus country-specific models used to estimate density surfaces for redistributing census counts. Consideration is given to the spatial resolution of input census data using examples from East Africa and Southeast Asia. Results suggest that for many countries more accurate population maps can be produced by using regionally-parameterized models where more spatially refined data exists than that which is available for the focal country. This study highlights the advancement of statistical toolsets and considerations for underlying data used in generating widely used gridded population data. [ABSTRACT FROM PUBLISHER]

The investigations reported here describe the synthesis of carbon nanowalls (CNWs) by microwave electron-cyclotron resonance (ECR) plasma-assisted chemical vapour deposition (PACVD) process without an application of external bias to the substrate during growth. CNWs were grown on silicon (Si) substrates using hydrogen (H2)/methane (CH4) plasma at 650°C substrate temperature. Nickel (Ni) was used as a catalyst for the synthesis of CNWs. To the best of our knowledge, this is the first report that describes the bias-independent growth of CNWs using the ECR PACVD process. Formation of CNWs is confirmed by scanning electron microscopy and Raman spectroscopy. The discussion part also includes a possible growth mechanism for CNWs in terms of the role of surface plasmons. [ABSTRACT FROM PUBLISHER]

Abstract: Electronic band structures and elastic properties of III–V quaternary In x Ga1− x As y Sb1− y alloys are presented following the empirical pseudopotential method. The alloying effects are modelled through the modified virtual crystal approximation. Calculations are also performed to report the density of states, refractive index, and ionicity factors. Among elastic properties the elastic constants and bulk modulus are reported. The electronic structure, optical and elastic properties are reported for the In0.25Ga0.75As0.25Sb0.75, In0.25Ga0.75As0.75Sb0.25, In0.75Ga0.25As0.25Sb0.75 and In0.75Ga0.25As0.75Sb0.25 compositions. Dependence of the band gap, refractive index and the ionicity with the cationic and anionic compositions are discussed. The results are compared with the available theoretical and experimental data of lattice matched compounds. [ABSTRACT FROM AUTHOR]