2,264 research outputs found

    Coupled-channels Faddeev AGS calculation of K−ppnK^{-}ppn and K−pppK^{-}ppp quasi-bound states

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    Using separable KˉN−πΣ\bar{K}N-\pi\Sigma potentials in the Faddeev equations, we calculated the binding energies and widths of the K−ppK^{-}pp, K−ppnK^{-}ppn and K−pppK^{-}ppp quasi-bound states on the basis of three- and four-body Alt-Grassberger-Sandhas equations in the momentum representation. One- and two-pole version of KˉN−πΣ\bar{K}N-\pi\Sigma interaction are considered and the dependence of the resulting few-body energy on the two-body KˉN−πΣ\bar{K}N-\pi\Sigma potential was investigated. The ss-wave [3+1] and [2+2] sub-amplitudes are obtained by using the Hilbert-Schmidt expansion procedure for the integral kernels. As a result, we found a four-body resonance of the K−ppnK^{-}ppn and K−pppK^{-}ppp quasi-bound states with a binding energy in the range BK−ppn∼55−70B_{K^{-}ppn}\sim{55-70} and BK−ppp∼90−100B_{K^{-}ppp}\sim{90-100} MeV, respectively. The calculations yielded full width of ΓK−ppn∼16−20\Gamma_{K^{-}ppn}\sim{16-20} and ΓK−ppp∼7−20\Gamma_{K^{-}ppp}\sim{7-20} MeV.Comment: 16 pages, 4 figure

    Carrier multiplication between interacting nanocrystals for fostering silicon-based photovoltaics

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    Being a source of clean and renewable energy, the possibility to convert solar radiation in electric current with high efficiency is one of the most important topics of modern scientific research. Currently the exploitation of interaction between nanocrystals seems to be a promising route to foster the establishment of third generation photovoltaics. Here we adopt a fully ab-initio scheme to estimate the role of nanoparticle interplay on the carrier multiplication dynamics of interacting silicon nanocrystals. Energy and charge transfer-based carrier multiplication events are studied as a function of nanocrystal separation showing benefits induced by the wavefunction sharing regime. We prove the relevance of these recombinative mechanisms for photovoltaic applications in the case of silicon nanocrystals arranged in dense arrays, quantifying at an atomistic scale which conditions maximize the outcome.Comment: Supplementary materials are freely available onlin

    Determinants of increased real prices of livestock in Balochistan

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    The real prices of livestock in Balochistan have been increasing dramatically over the last decade and still there is no sign for them to recede. There is no study that accounts for determinants of this rise in the real prices of livestock in Balochistan. The purpose of this research was to find out the determinants for the increasing real prices of livestock. The research was mainly conducted in Balochistan including rural and urban areas of Quetta, Mastung and Kuchlaq. Twenty-nine farmers, livestock experts, government agencies and vets were selected as the respondents to gather data using questioning technique. In addition, some of the data was also obtained from the report of SMEDA. Judgemental sampling was used as the method for data collection from the respondents. The data thus collected was descriptively analysed. The study found that the determinants for the rise in the real prices of livestock included shortage of production/supply, high risk of raising animals, smuggling of livestock across the boarders, lack of government support and low level of technological use

    The emergence and fate of horizontally acquired genes in Escherichia coli

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    Bacterial species, and even strains within species, can vary greatly in their gene contents and metabolic capabilities. We examine the evolution of this diversity by assessing the distribution and ancestry of each gene in 13 sequenced isolates of Escherichia coli and Shigella. We focus on the emergence and demise of two specific classes of genes, ORFans (genes with no homologs in present databases) and HOPs (genes with distant homologs), since these genes, in contrast to most conserved ancestral sequences, are known to be a major source of the novel features in each strain. We find that the rates of gain and loss of these genes vary greatly among strains as well as through time, and that ORFans and HOPs show very different behavior with respect to their emergence and demise. Although HOPs, which mostly represent gene acquisitions from other bacteria, originate more frequently, ORFans are much more likely to persist. This difference suggests that many adaptive traits are conferred by completely novel genes that do not originate in other bacterial genomes. With respect to the demise of these acquired genes, we find that strains of Shigella lose genes, both by disruption events and by complete removal, at accelerated rates
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