1,440 research outputs found

    Range-separated density-functional theory with random phase approximation: detailed formalism and illustrative applications

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    Using Green-function many-body theory, we present the details of a formally exact adiabatic-connection fluctuation-dissipation density-functional theory based on range separation, which was sketched in Toulouse, Gerber, Jansen, Savin and Angyan, Phys. Rev. Lett. 102, 096404 (2009). Range-separated density-functional theory approaches combining short-range density functional approximations with long-range random phase approximations (RPA) are then obtained as well-identified approximations on the long-range Green-function self-energy. Range-separated RPA-type schemes with or without long-range Hartree-Fock exchange response kernel are assessed on rare-gas and alkaline-earth dimers, and compared to range-separated second-order perturbation theory and range-separated coupled-cluster theory.Comment: 15 pages, 3 figures, 2 table

    Modelling the evolution of distributions : an application to major league baseball

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    We develop Bayesian techniques for modelling the evolution of entire distributions over time and apply them to the distribution of team performance in Major League baseball for the period 1901-2000. Such models offer insight into many key issues (e.g. competitive balance) in a way that regression-based models cannot. The models involve discretizing the distribution and then modelling the evolution of the bins over time through transition probability matrices. We allow for these matrices to vary over time and across teams. We find that, with one exception, the transition probability matrices (and, hence, competitive balance) have been remarkably constant across time and over teams. The one exception is the Yankees, who have outperformed all other teams

    T cell-mediated oral tolerance is intact in germ-free mice

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    Commensal enteric bacteria stimulate innate immune cells and increase numbers of lamina propria and mesenteric lymph node (MLN) T and B lymphocytes. However, the influence of luminal bacteria on acquired immune function is not understood fully. We investigated the effects of intestinal bacterial colonization on T cell tolerogenic responses to oral antigen compared to systemic immunization. Lymphocytes specific for ovalbumin–T cell receptor (OVA–TCR Tg+) were transplanted into germ-free (GF) or specific pathogen-free (SPF) BALB/c mice. Recipient mice were fed OVA or immunized subcutaneously with OVA peptide (323–339) in complete Freund's adjuvant (CFA). Although the efficiency of transfer was less in GF recipients, similar proportions of cells from draining peripheral lymph node (LN) or MLN were proliferating 3–4 days later in vivo in GF and SPF mice. In separate experiments, mice were fed tolerogenic doses of OVA and then challenged with an immunogenic dose of OVA 4 days later. Ten days after immunization, lymphocytes were restimulated with OVA in vitro to assess antigen-specific proliferative responses. At both high and low doses of OVA, cells from both SPF and GF mice fed OVA prior to immunization had decreased proliferation compared to cells from control SPF or GF mice. In addition, secretion of interferon (IFN)-γ and interleukin (IL)-10 by OVA–TCR Tg+ lymphocytes was reduced in both SPF and GF mice fed OVA compared to control SPF or GF mice. Unlike previous reports indicating defective humoral responses to oral antigen in GF mice, our results indicate that commensal enteric bacteria do not enhance the induction of acquired, antigen-specific T cell tolerance to oral OVA

    Efficient deformable motion correction for 3-D abdominal MRI using manifold regression

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    We present a novel framework for efficient retrospective respiratory motion correction of 3-D abdominal MRI using manifold regression. K-space data are continuously acquired under free breathing using the stack-of-stars radial gold-en-angle trajectory. The stack-of-profiles (SoP) from all temporal positions are embedded into a common manifold, in which SoPs that were acquired at similar respiratory states are close together. Next, the SoPs in the manifold are clustered into groups using the k-means algorithm. One 3-D volume is reconstructed at the central SoP position of each cluster (a.k.a. key-volumes). Motion fields are estimated using deformable image registration between each of these key-volumes and a reference end-exhale volume. Subsequently, the motion field at any other SoP position in the manifold is derived using manifold regression. The regressed motion fields for each of the SoPs are used to deter-mine a final motion-corrected MRI volume. The method was evaluated on realistic synthetic datasets which were generated from real MRI data and also tested on an in vivo dataset. The framework enables more accurate motion correction compared to the conventional binning-based approach, with high computational efficiency

    Gene expression patterns in experimental colitis in IL-10-deficient mice:

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    While others have described gene expression patterns in humans with inflammatory bowel diseases and animals with chemically-induced colitis, a genome-wide comparison of gene expression in genetically susceptible animals that develop spontaneous colitis has not been reported. We used microarray technology to compare gene expression profiles in cecal specimens from specific pathogen-free IL10-deficient (IL10−/−) mice with colitis and normal wild-type (WT) mice. RNA isolated from ceca of IL10−/− and WT mice was subjected to microarray analysis. Results were confirmed by real-time PCR and immunofluorescence microscopy of selected molecules. Expression of the selected genes in DSS-treated mice with colitis and epithelial cell lines activated with pathophysiologic stimuli was measured by real-time PCR. Histological inflammation of the colon and IL-12/23p40 secretion from intestinal explants were greater in IL10−/− and DSS-treated mice vs. WT and untreated mice. Microarray analysis demonstrated >10-fold induction of the following molecules in the ceca of IL10−/− mice: Mitochondrial ribosomal protein-L33, aquaporin-4, indoleamine-pyrrole-2,3- dioxygenase, and MHC class II with 63, 25, 20, and 12-fold increases, respectively. Cytochrome-P450, pancreatic lipase-related protein-2, and transthyretin were down-regulated in IL10−/− mice. MHC II was increased throughout the colon, and aquaporin-4 was increased in the basolateral aspect of cecal epithelial cells. MHC II mRNA was increased in epithelial cells treated with IFNγ, but not TNF or Toll-like receptor ligands. Although most upregulated genes in experimental colitis are immune-related, aquaporin-4 and mitochondrial ribosomal protein, which have not been previously associated with inflammation, were most highly upregulated

    Voices of girls with disabilities in rural Iran

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    This paper investigates the interaction of gender, disability and education in rural Iran, which is a relatively unexplored field of research. The responses of 10 female students with disabilities from Isfahan indicated that the obstacles they faced included marginalization, difficulties in getting from home to school, difficulties within the school building itself, and discrimination by teachers, classmates and school authorities. The data collected for the study contain a wide range of conservative gendered discourses, and show how traditional gender beliefs interact with disability to aggravate the problems faced in education by young women with disabilities. It is hoped that the findings will raise awareness among policy-makers of the many formidable obstacles that make it difficult for young women with disabilities to achieve their full potential in education

    High-resolution self-gated dynamic abdominal MRI using manifold alignment

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    We present a novel retrospective self-gating method based on manifold alignment (MA), which enables reconstruction of free-breathing, high spatial and temporal resolution abdominal MRI sequences. Based on a radial golden-angle (RGA) acquisition trajectory, our method enables a multi-dimensional self-gating signal to be extracted from the k-space data for more accurate motion representation. The k-space radial profiles are evenly divided into a number of overlapping groups based on their radial angles. MA is then used to simultaneously learn and align the low dimensional manifolds of all groups, and embed them into a common manifold. In the manifold, k-space profiles that represent similar respiratory positions are close to each other. Image reconstruction is performed by combining radial profiles with evenly distributed angles that are close in the manifold. Our method was evaluated on both 2D and 3D synthetic and in vivo datasets. On the synthetic datasets, our method achieved high correlation with the ground truth in terms of image intensity and virtual navigator values. Using the in vivo data, compared to a state-of-the-art approach based on centre of k-space gating, our method was able to make use of much richer profile data for self-gating, resulting in statistically significantly better quantitative measurements in terms of organ sharpness and image gradient entropy

    Localized gut-associated lymphoid tissue hemorrhage induced by intravenous peptidoglycan-polysaccharide polymers.

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    A hemorrhage into gut-associated lymphoid tissue developed as early as 3 min after the intravenous injection of group A streptococcal peptidoglycan-polysaccharide polymers into rats. Extravasated erythrocytes were specifically located in the lamina propria and organized lymphoid follicles of the intestines and mesenteric lymph nodes and did not occur in the lungs, kidneys, liver, spleen, adrenal glands, or submandibular and popliteal lymph nodes, as determined by gross and histologic observations and measurement of radiolabeled erythrocytes. Petechial hemorrhage was preferentially located within the intestine to the distal ileum, Peyer's patches, and lymphoid aggregates of the colon. The hemorrhage was transient and occurred in a dose-dependent fashion. It was maximal 5 min after injection and resolved completely by 3 days. A unique feature of this altered vascular permeability was the absence of polymorphonuclear leukocytic infiltration, edema, vasculitis, and tissue necrosis
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