114 research outputs found

    Towards heavy-mass ab initio nuclear structure: Open-shell Ca, Ni and Sn isotopes from Bogoliubov coupled-cluster theory

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    Recent developments in nuclear many-body theory enabled the description of open-shell medium-mass nuclei from first principles by exploiting the spontaneous breaking of symmetries within correlation expansion methods. Once combined with systematically improvable inter-nucleon interactions consistently derived from chiral effective field theory, modern ab initio nuclear structure calculations provide a powerful framework to deliver first-principle predictions accompanied with theoretical uncertainties. In this Letter, controlled ab initio Bogoliubov coupled cluster calculations are performed for the first time, targeting the ground-state of all calcium, nickel and tin isotopes up to mass A150A\approx150. While showing good agreement with available experimental data, the shell structure evolution in neutron-rich isotopes and the location of the neutron drip-lines are predicted.Comment: 7 pages, 5 figure

    Polarimetric distance-dependent models for large hall scenarios

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    A comprehensive polarimetric distance-dependent model of the power delay profile (PDP) and path gain is proposed. The model includes both specular multipath components (SMCs) and dense multipath components (DMC), the latter being modeled with an exponential and power law. The parameters of the model were estimated from polarimetric measurements of a large hall radio channel under line-of-sight (LOS) conditions at 1.3 GHz with a dedicated procedure. The validity and robustness of the proposed approach are provided by the good agreement between the polarimetric data and models for the investigated transmitter-receiver distance range. Furthermore, the description of the radio channel with path loss models is discussed for cases where the DMC is included, and a two-step method to compute the path loss characteristics directly from the measured data is developed. The results of this contribution highlight the fact that a complete polarimetric description of all propagation mechanisms and related path loss models is desired to design faithful polarimetric radio channel models

    Parallel functional and stoichiometric trait shifts in South American and African forest communities with elevation

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    The Amazon and Congo basins are the two largest continuous blocks of tropical forest with a central role for global biogeochemical cycles and ecology. However, both biomes differ in structure and species richness and composition. Understanding future directions of the response of both biomes to environmental change is paramount. We used one elevational gradient on both continents to investigate functional and stoichiometric trait shifts of tropical forest in South America and Africa. We measured community-weighted functional canopy traits and canopy and topsoil delta N-15 signatures. We found that the functional forest composition response along both transects was parallel, with a shift towards more nitrogen-conservative species at higher elevations. Moreover, canopy and topsoil delta N-15 signals decreased with increasing altitude, suggesting a more conservative N cycle at higher elevations. This cross-continental study provides empirical indications that both South American and African tropical forest show a parallel response with altitude, driven by nitrogen availability along the elevational gradients, which in turn induces a shift in the functional forest composition. More standardized research, and more research on other elevational gradients is needed to confirm our observations

    Polarimetric properties and modeling of the power delay profile in large hall scenarios

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    A full-polarimetric model of the power delay profile (PDP) is proposed in a large hall scenario and validated with polarimetric measurements of a large open hall radio channel under Line-of-Sight conditions at 1.3 GHz. The measured radio channels were processed by the high-resolution parametric estimator RiMAX to estimate both the polarimetric specular multipath components (SMC) and dense multipath components (DMC). The model of the full-polarimetric distance-dependent PDP was derived from which the depolarization mechanisms are presented. In addition, it is demonstrated that the room electromagnetics theory applies to our scenario across all polarization links. The validity of the proposed model is provided by the good agreement between the polarimetric data and models. The results of this contribution highlight the fact that a complete polarimetric description of all propagation mechanisms is desired in polarimetric radio channel models

    Role of Gas6 Receptors in Platelet Signaling during Thrombus Stabilization and Implications for Antithrombotic Therapy

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    Mechanisms regulating thrombus stabilization remain largely unknown. Here, we report that loss of any 1 of the Gas6 receptors (Gas6-Rs), i.e., Tyro3, Axl, or Mer, or delivery of a soluble extracellular domain of Axl that traps Gas6 protects mice against life-threatening thrombosis. Loss of a Gas6-R does not prevent initial platelet aggregation but impairs subsequent stabilization of platelet aggregates, at least in part by reducing “outside-in” signaling and platelet granule secretion. Gas6, through its receptors, activates PI3K and Akt and stimulates tyrosine phosphorylation of the β3 integrin, thereby amplifying outside-in signaling via αIIbβ3. Blocking the Gas6-R–αIIbβ3 integrin cross-talk might be a novel approach to the reduction of thrombosis
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