450 research outputs found

    Constraints on s→dγs\to d \gamma from Radiative Hyperon and Kaon Decays

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    The quark-level process b→sγb \to s \gamma has been used extensively to place constraints on new interactions. These same interactions can be further constrained from the enhancement they induce in the quark-level s→dγs \to d \gamma transition, to the extent that the short distance contributions can be separated from the long distance contributions. We parameterize what is known about the long distance amplitudes and subtract it from the data in radiative hyperon and kaon decays to constrain new interactions.Comment: Latex 11 page

    Late Quaternary sedimentary processes in the central Arctic Ocean inferred from geophysical mapping

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    Cryospheric events in the Arctic Ocean have been largely studied through the imprints of ice sheets, ice shelves and icebergs in the seafloor morphology and sediment stratigraphy. Subglacial morphologies have been identified in the shallowest regions of the Arctic Ocean, up to 1200 m water depth, revealing the extent and dynamics of Arctic ice sheets during the last glacial periods. However, less attention has been given to sedimentary features imaged in the vicinity of the ice-grounded areas. Detailed interpretation of the sparse available swath bathymetry and sub-bottom profiles from the Lomonosov Ridge and the Amundsen Basin shows the occurrence of mass transport deposits (MTDs) and sediment waves in the central Arctic Ocean. The waxing and waning ice sheets and shelves in the Arctic Ocean have influenced the distribution of MTDs in the vicinity of grounding-ice areas, i.e. along the crest of Lomonosov Ridge. Due to the potential of Arctic sediments to hold gas hydrates, their destabilization should not be ruled out as trigger for sediment instability. Sediment waves formed by the interaction of internal waves that propagate along water mass interfaces with the bathymetric barrier of Lomonosov Ridge. This work describes the distribution and formation mechanisms of MTDs and sediment waves in the central Arctic Ocean in relation to grounding ice and internal waves between water masses respectively. The distribution of these features provides new insight into past cryospheric and oceanographic conditions of the central Arctic Ocean

    The standard model at low energies

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    The hadronic sector of the standard model at low energies is described by a non--decoupling effective field theory, chiral perturbation theory. An introduction is given to the construction of effective chiral Lagrangians, both in the purely mesonic sector and with inclusion of baryons. The connection between the relativistic formulation and the heavy baryon approach to chiral perturbation theory with baryons is reviewed.Comment: Lectures given at the 6th Indian-Summer School on Intermediate Energy Physics, Prague, Aug. 1993, Latex, 26 pages (with a4.sty), UWThPh-1993-3

    Structural insights into crista junction formation by the Mic60-Mic19 complex

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    Mitochondrial cristae membranes are the oxidative phosphorylation sites in cells. Crista junctions (CJs) form the highly curved neck regions of cristae and are thought to function as selective entry gates into the cristae space. Little is known about how CJs are generated and maintained. We show that the central coiled-coil (CC) domain of the mitochondrial contact site and cristae organizing system subunit Mic60 forms an elongated, bow tie–shaped tetrameric assembly. Mic19 promotes Mic60 tetramerization via a conserved interface between the Mic60 mitofilin and Mic19 CHCH (CC-helix-CC-helix) domains. Dimerization of mitofilin domains exposes a crescent-shaped membrane-binding site with convex curvature tailored to interact with the curved CJ neck. Our study suggests that the Mic60-Mic19 subcomplex traverses CJs as a molecular strut, thereby controlling CJ architecture and function

    Electrocardiographic changes in a rare case of flecainide poisoning: a case report

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    Flecainide is a class Ic anti - arrhythmic drug with sodium channel blocking activities. We report a case of a 57 year - old woman who attempted a suicide by ingesting approximately 1,8 gr of flecainide. On the surface electrocardiogram this results in a large QRS complex and in prolongation of the QTc interval. Overdose with a class Ic drug is very uncommon, its management is difficult and the mortality high

    Search for the K(L) --> PI0 PI0 E+ E- Decay in the KTeV Experiment

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    The recent discovery of a large CP violating asymmetry in K(L) --> PI+ PI- E+ E- mode has prompted us to seach for the associated K(L) --> PI0 PI0 E+ E- decay mode in the KTeV-E799 experiment at Fermilab. In 2.7E+11 K(L) decays, one candidate event has been observed with an expected background of 0.3 event, resulting in an upper limit for the K(L) --> PI0 PI0 E+ E- branching ratio of 6.6E-09 at the 90% confidence level.Comment: To be published in Phys. Rev. Let

    Maternal education and cognitive development in 15 European very-preterm birth cohorts from the RECAP Preterm platform

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    Background: Studies are sparse and inconclusive about the association between maternal education and cognitive development among children born very preterm (VPT). Although this association is well established in the general population, questions remain about its magnitude among children born VPT whose risks of medical and developmental complications are high. We investigated the association of maternal education with cognitive outcomes in European VPT birth cohorts. Methods: We used harmonized aggregated data from 15 population-based cohorts of children born at = 37 weeks of GA) were available in eight cohorts. Maternal education was classified as: low (primary/lower secondary); medium (upper secondary/short tertiary); high (bachelor's/higher). Pooled standardized mean differences (SMDs) in cognitive scores were estimated (reference: high educational level) for children assessed at ages 2-3, 4-7 and 8-15 years. Results: The study included 10 145 VPT children from 12 cohorts at 2-3 years, 8829 from 12 cohorts at 4-7 years and 1865 children from 6 cohorts at 8-15 years. Children whose mothers had low, compared with high, educational attainment scored lower on cognitive measures [pooled unadjusted SMDs: 2-3 years = -0.32 (95% confidence intervals: -0.43 to -0.21); 4-7 years = -0.57 (-0.67; -0.47); 8-15 years = -0.54 (-0.72; -0.37)]. Analyses by GA subgroups (= 27 weeks) in children without severe neonatal morbidity and term controls yielded similar results. Conclusions: Across diverse settings and regardless of the degree of prematurity, low maternal education was associated with lower cognition.Peer reviewe
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