4,488 research outputs found

    Quantum confinement in perovskite oxide heterostructures: tight binding instead of nearly free electron picture

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    Most recently, orbital-selective quantum well states of dd electrons have been experimentally observed in SrVO3_3 ultrathin films [K. Yoshimatsu et. al., Science 333, 319 (2011)] and SrTiO3_3 surfaces [A. F. Santander-Syro et. al., Nature 469, 189 (2011)]. Hitherto, one tries to explain these experiments by a nearly free electron (NFE) model, an approach widely used for delocalized electrons in semiconductor heterostructures and simple metal films. We show that a tight binding (TB) model is more suitable for describing heterostructures with more localized dd electrons. In this paper, we construct from first principles simple TB models for perovskite oxide heterostructures and surfaces. We show that the TB model provides a simple intuitive physical picture and yields, already with only two parameters, quantitatively much more reliable results, consistent with experiment

    The Expanding Landscape of Alternative Splicing Variation in Human Populations.

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    Alternative splicing is a tightly regulated biological process by which the number of gene products for any given gene can be greatly expanded. Genomic variants in splicing regulatory sequences can disrupt splicing and cause disease. Recent developments in sequencing technologies and computational biology have allowed researchers to investigate alternative splicing at an unprecedented scale and resolution. Population-scale transcriptome studies have revealed many naturally occurring genetic variants that modulate alternative splicing and consequently influence phenotypic variability and disease susceptibility in human populations. Innovations in experimental and computational tools such as massively parallel reporter assays and deep learning have enabled the rapid screening of genomic variants for their causal impacts on splicing. In this review, we describe technological advances that have greatly increased the speed and scale at which discoveries are made about the genetic variation of alternative splicing. We summarize major findings from population transcriptomic studies of alternative splicing and discuss the implications of these findings for human genetics and medicine

    M\"ossbauer spectroscopy study of magnetic fluctuations in superconducting RbGd2_2Fe4_4As4_4O2_2

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    57^{57}Fe M\"ossbauer spectra were measured at different temperatures between 5.9 K and 300 K on the recently discovered self-doped superconducting RbGd2_2Fe4_4As4_4O2_2 with Tc_c as high as 35 K. Singlet pattern was observed down to the lowest temperature measured in this work, indicating the absence of static magnetic order on the Fe site. The intermediate isomer shift in comparison with that of the samples RbFe2_2As2_2 and GdFeAsO confirms the self doping induced local electronic structure change. Surprisingly, we observe two magnetic fluctuation induced spectral broadenings below \sim15 K and \sim100 K which are believed to be originated from the transferred magnetic fluctuations of the Gd3+^{3+} moments and that of the magnetic fluctuations of the Fe atoms, respectively.Comment: 6 pages, 6 figures, 1 tabl
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