1,390 research outputs found

    On deformed double current algebras for simple Lie algebras

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    On deformed double current algebras for simple Lie algebras

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    We prove the equivalence of two presentations of deformed double current algebras associated to a complex simple Lie algebra, the first one obtained via a degeneration of affine Yangians while the other one naturally appeared in the construction of the elliptic Casimir connection. We also construct a specific central element of these algebras and, in type A, show that they contain a very large center for certain values of their parameters.Comment: 40 page

    Na+/Ca(2+ )Exchanger a Druggable Target to Promote beta -Cell Proliferation and Function

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    An important feature of type 2 diabetes is a decrease in <i>β</i> -cell mass. Therefore, it is essential to find new approaches to stimulate <i>β</i> -cell proliferation. We have previously shown that heterozygous inactivation of the Na <sup>+</sup> /Ca <sup>2+</sup> exchanger (isoform 1; NCX1), a protein responsible for Ca <sup>2+</sup> extrusion from cells, increases <i>β</i> -cell proliferation, mass, and function in mice. Here, we show that <i>Ncx</i> 1 inactivation also increases <i>β</i> -cell proliferation in 2-year-old mice and that NCX1 inhibition in adult mice by four small molecules of the benzoxyphenyl family stimulates <i>β</i> -cell proliferation both <i>in vitro</i> and <i>in vivo</i> . NCX1 inhibition by small interfering RNA or small molecules activates the calcineurin/nuclear factor of activated T cells (NFAT) pathway and inhibits apoptosis induced by the immunosuppressors cyclosporine A (CsA) and tacrolimus in insulin-producing cell. Moreover, NCX1 inhibition increases the expression of <i>β</i> -cell-specific genes, such as <i>Ins1, Ins2,</i> and <i>Pdx</i> 1, and inactivates/downregulates the tumor suppressors retinoblastoma protein (pRb) and miR-193a and the cell cycle inhibitor p53. Our data show that Na <sup>+</sup> /Ca <sup>2+</sup> exchange is a druggable target to stimulate <i>β</i> -cell function and proliferation. Specific <i>β</i> -cell inhibition of Na <sup>+</sup> /Ca <sup>2+</sup> exchange by phenoxybenzamyl derivatives may represent an innovative approach to promote <i>β</i> -cell regeneration in diabetes and improve the efficiency of pancreatic islet transplantation for the treatment of the disease

    Response of Net Ecosystem Productivity of Three Boreal Forest Stands to Drought

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    In 2000-03, continuous eddy covariance measurements of carbon dioxide (CO2) flux were made above mature boreal aspen, black spruce, and jack pine forests in Saskatchewan, Canada, prior to and during a 3-year drought. During the 1st drought year, ecosystem respiration (R) was reduced at the aspen site due to the drying of surface soil layers. Gross ecosystem photosynthesis (GEP) increased as a result of a warm spring and a slow decrease of deep soil moisture. These conditions resulted in the highest annual net ecosystem productivity (NEP) in the 9 years of flux measurements at this site. During 2002 and 2003, a reduction of 6% and 34% in NEP, respectively, compared to 2000 was observed as the result of reductions in both R and GEP, indicating a conservative response to the drought. Although the drought affected most of western Canada, there was considerable spatial variability in summer rainfall over the 100-km extent of the study area; summer rainfalls in 2001 and 2002 at the two conifer sites minimized the impact of the drought. In 2003, however, precipitation was similarly low at all three sites. Due to low topographic position and consequent poor drainage at the black spruce site and the coarse soil with low water-holding capacity at the jack pine site almost no reduction in R, GEP, and NEP was observed at these two sites. This study shows that the impact of drought on carbon sequestration by boreal forest ecosystems strongly depends on rainfall distribution, soil characteristics, topography, and the presence of vegetation that is well adapted to these condition

    Factors associated with attendee adherence to COVID-19 guidance during the 2021 DCMS Events Research Programme Phase 1

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    As part of the DCMS Events Research Programme 2021, we surveyed and interviewed attendees of the FA Cup Semi-Final (18th April), Carabao Cup Final (25th April), the FA Cup Final (15th May), the Snooker World Championship (17th April – 3rd May) and Sefton Park music event (2nd May) to examine attendee experiences of the events, perceptions of the COVID-19 guidance, and factors most associated with self-reported adherence

    Representations of twisted Yangians of types B, C, D: I

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    We initiate a theory of highest weight representations for twisted Yangians of types B, C, D and we classify the finite-dimensional irreducible representations of twisted Yangians associated to symmetric pairs of types CI, DIII and BCD0

    Visuo-spatial ability in colonoscopy simulator training

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    Visuo-spatial ability is associated with a quality of performance in a variety of surgical and medical skills. However, visuo-spatial ability is typically assessed using Visualization tests only, which led to an incomplete understanding of the involvement of visuo-spatial ability in these skills. To remedy this situation, the current study investigated the role of a broad range of visuo-spatial factors in colonoscopy simulator training. Fifteen medical trainees (no clinical experience in colonoscopy) participated in two psycho-metric test sessions to assess four visuo-spatial ability factors. Next, participants trained flexible endoscope manipulation, and navigation to the cecum on the GI Mentor II simulator, for four sessions within 1 week. Visualization, and to a lesser degree Spatial relations were the only visuo-spatial ability factors to correlate with colonoscopy simulator performance. Visualization additionally covaried with learning rate for time on task on both simulator tasks. High Visualization ability indicated faster exercise completion. Similar to other endoscopic procedures, performance in colonoscopy is positively associated with Visualization, a visuo-spatial ability factor characterized by the ability to mentally manipulate complex visuo-spatial stimuli. The complexity of the visuo-spatial mental transformations required to successfully perform colonoscopy is likely responsible for the challenging nature of this technique, and should inform training- and assessment design. Long term training studies, as well as studies investigating the nature of visuo-spatial complexity in this domain are needed to better understand the role of visuo-spatial ability in colonoscopy, and other endoscopic techniques
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