1,225 research outputs found

    Site Selection Report of Farmer-led Participatory Maize Breeding Programme for the Middle Hills of Nepal

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    Maize is the second most important crop after rice in Nepal. Maize is grown largely on bari land during summer. The productivity of maize is quite low. A number of factors appear to be in play for the low productivity in the middle hills of Nepal

    Structural origins of electronic conduction in amorphous copper-doped alumina

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    We perform an {\it ab initio} modeling of amorphous copper-doped alumina (a-Al2_2O3_3:Cu), a prospective memory material based on resistance switching, and study the structural origin of electronic conduction in this material. We generate molecular dynamics based models of a-Al2_2O3_3:Cu at various Cu-concentrations and study the structural, electronic and vibrational properties as a function of Cu-concentration. Cu atoms show a strong tendency to cluster in the alumina host, and metallize the system by filling the band gap uniformly for higher Cu-concentrations. We also study thermal fluctuations of the HOMO-LUMO energy splitting and observe the time evolution of the size of the band gap, which can be expected to have an important impact on the conductivity. We perform a numerical computation of conduction pathways, and show its explicit dependence on Cu connectivity in the host. We present an analysis of ion dynamics and structural aspects of localization of classical normal modes in our models

    Density functional study of FeS, FeSe and FeTe: Electronic structure, magnetism, phonons and superconductivity

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    We report density functional calculations of the electronic structure, Fermi surface, phonon spectrum, magnetism and electron-phonon coupling for the superconducting phase FeSe, as well as the related compounds FeS and FeTe. We find that the Fermi surface structure of these compounds is very similar to that of the Fe-As based superconductors, with cylindrical electron sections at the zone corner, cylindrical hole surface sections, and depending on the compound, other small hole sections at the zone center. As in the Fe-As based materials, these surfaces are separated by a 2D nesting vector at (Ï€\pi,Ï€\pi). The density of states, nesting and Fermi surface size increase going from FeSe to FeTe. Both FeSe and FeTe show spin density wave ground states, while FeS is close to an instability. In a scenario where superconductivity is mediated by spin fluctuations at the SDW nesting vector, the strongest superconductor in this series would be doped FeTe.Comment: Added note regarding recent experimental observations of superconductivity under pressure. Some additional discussio

    New record of earthworm Eukerria kuekenthali (Oligochaeta: Ocnerodrilidae) from Sikkim, India

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    The earthworm genus Eukerria kuekenthali (Michaelsen 1908) is recorded for the first time from the Sikkimese soil. Inter/ intra specific variations have not been observed. Altitude plays a vital role in the distribution pattern of this species. The photographic descriptions with illustrations are provided

    Electronic Structure, Magnetism and Superconductivity of Layered Iron Compounds

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    The layered iron superconductors are discussed using electronic structure calculations. The four families of compounds discovered so far, including Fe(Se,Te) have closely related electronic structures. The Fermi surface consists of disconnected hole and electron cylinders and additional hole sections that depend on the specific material. This places the materials in proximity to itinerant magnetism, both due to the high density of states and due to nesting. Comparison of density functional results and experiment provides strong evidence for itinerant spin fluctuations, which are discussed in relation to superconductivity. It is proposed that the intermediate phase between the structural transition and the SDW transition in the oxy-pnictides is a nematic phase.Comment: Proceedings ISS200
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