1,279 research outputs found

    Semi-classical Green kernel asymptotics for the Dirac operator

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    We consider a semi-classical Dirac operator in arbitrary spatial dimensions with a smooth potential whose partial derivatives of any order are bounded by suitable constants. We prove that the distribution kernel of the inverse operator evaluated at two distinct points fulfilling a certain hypothesis can be represented as the product of an exponentially decaying factor involving an associated Agmon distance and some amplitude admitting a complete asymptotic expansion in powers of the semi-classical parameter. Moreover, we find an explicit formula for the leading term in that expansion.Comment: 46 page

    Evaluation of salt tolerance of in vitro-grown grapevine rootstock varieties

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    The response of 11 grapevine rootstock varieties to increasing salt concentrations (0, 50, 85, 120, 155 mM NaCl) was studied under in vitro and growth chamber conditions. The effect of salinity on the mortality of explants was compared with that of plantlets grown under growth chamber conditions and with data in literature on rootstock resistance under field conditions. In addition, in vitro stem elongation bud number, and rooting ability were related to salinity. The rootstock varieties can be divided into sensitive (41 B, R.Lot, 110 R, 140 R and 161-49), moderately tolerant (13.5 and Ramsey) and tolerant (196-17, CH-1, CH-2 and Superior). Measurements of the water and nutrient contents of plantlets indicate that increasing salt concentrations decreased the hydration of aerial parts and roots of all plants; however, the decrease of hydration was smaller in salt tolerant varieties. Increasing salt concentrations significantly reduced the K content and, to a smaller extent, the P and Ca contents. With and without salt treatments the levels of K and P were lower in sensitive plants. Na and Cl accumulated to a higher extent in tolerant plants. The tolerance to NaCl of in vitro-grown rootstocks seems to be due to their capacity to accumulate salt, to increase K concentration in the tissue and to maintain a high water content. Our results indicate that salt tolerance of grapevine varieties may be tested under growth chamber conditions and using in vitro explants

    The Lazarus Project. II. Spacelike extraction with the quasi-Kinnersley tetrad

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    The Lazarus project was designed to make the most of limited 3D binary black-hole simulations, through the identification of perturbations at late times, and subsequent evolution of the Weyl scalar Ψ4\Psi_4 via the Teukolsky formulation. Here we report on new developments, employing the concept of the ``quasi-Kinnersley'' (transverse) frame, valid in the full nonlinear regime, to analyze late-time numerical spacetimes that should differ only slightly from Kerr. This allows us to extract the essential information about the background Kerr solution, and through this, to identify the radiation present. We explicitly test this procedure with full numerical evolutions of Bowen-York data for single spinning black holes, head-on and orbiting black holes near the ISCO regime. These techniques can be compared with previous Lazarus results, providing a measure of the numerical-tetrad errors intrinsic to the method, and give as a by-product a more robust wave extraction method for numerical relativity.Comment: 17 pages, 10 figures. Journal version with text changes, revised figures. [Note updated version of original Lazarus paper (gr-qc/0104063)

    Exponential localization of hydrogen-like atoms in relativistic quantum electrodynamics

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    We consider two different models of a hydrogenic atom in a quantized electromagnetic field that treat the electron relativistically. The first one is a no-pair model in the free picture, the second one is given by the semi-relativistic Pauli-Fierz Hamiltonian. We prove that the no-pair operator is semi-bounded below and that its spectral subspaces corresponding to energies below the ionization threshold are exponentially localized. Both results hold true, for arbitrary values of the fine-structure constant, e2e^2, and the ultra-violet cut-off, Λ\Lambda, and for all nuclear charges less than the critical charge without radiation field, Zc=e22/(2/π+π/2)Z_c=e^{-2}2/(2/\pi+\pi/2). We obtain similar results for the semi-relativistic Pauli-Fierz operator, again for all values of e2e^2 and Λ\Lambda and for nuclear charges less than e22/πe^{-2}2/\pi.Comment: 37 page

    Erratum to: Spatial spin-up of fine scales in a regional climate model simulation driven by low-resolution boundary condition

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    The capture of the public servant in a criminal investigation is subject to special rules and different to those for the capture of individuals, since the imprisonment of an official can affect continuity, speed and efficiency of the civil service, an equally important constitutional value. Therefore, as a rule capturing the public servant must be preceded by a request for suspensión by the prosecution, and to proceed without suspension, the prosecutor in his providence should motivate the reasons and arguments why not affects the normal functioning of public administration. The lack of motivation for this essential aspect, affords a fact that becomes appropriate procedural habeas corpus as an effective mechanism guarantees of personal freedom. Similarly appropriate habeas corpus when catching public server ordered by a prosecutor without functional competence to advance research, by setting a path made by organic defect.La captura del servidor público investigado en un proceso penal está sujeta a reglas especiales y diversas a las previstas para la captura de los particulares, por cuanto la privación de la libertad de un funcionario puede afectar la continuidad, celeridad y eficacia de la función pública, como un valor constitucional igualmente relevante. Por tal motivo, como regla general,la captura del servidor público debe estar precedida de la solicitud de suspensión por parte de la Fiscalía General de la Nación y para que proceda sin suspensión previa, el fiscal debe consignar en su providencia las razones y argumentos por los cuales no se afecta el normal funcionamiento de la administración pública. La ausencia de motivación de este aspecto esencial constituye una vía de hecho procedimental que torna procedente la acción de habeas corpus, como mecanismo efectivo de garantía de la libertad personal. De igual manera, procede el habeas corpus cuando la captura del servidor público la ordena un fiscal sin competencia funcional para adelantar la investigación, por configuración de una vía de hecho por defecto orgánico

    Constructing the Settler Sovereign & the Mechanics of Power Distribution: Hydroelectricity and Biopolitics in James Bay and Northern Québec, 1970s-1990s

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    This thesis discusses the relationship between hydroelectric development in Northern Québec and the institutionalization of health in Cree and Inuit communities of Eeyou Istchee (James Bay) from the 1970s to the 1990s. It explores the deployment of nutritional science by the Québec Ministry of Health as a response to health issues exacerbated by the flooding of large areas of ancestral hunting and fishing territories and the resulting relocation of Indigenous communities. With particular attention to the roles of distinctly Franco-Québécois notions of sovereignty, gender, race, and anthropocentrism, this research seeks to assess political discourses about energy and health over the course of the second wave of hydroelectric nationalisation in the province. I begin by examining two court cases leading to the adoption of the James Bay and Northern Québec Agreement in 1975 – namely the Malouf decision and its appeal – to uncover the ideological underpinnings of the territorial negotiations between the Cree and Inuit and the Québec government. I then turn to the ways in which the Québec Ministry of Health targeted Indigenous mothers in the region through mechanisms of biopolitics in responding to health issues exacerbated by the destruction of Cree and Inuit foodways. In sum, this thesis problematizes the idea of hydroelectricity as a “green” energy in the Québec context by examining the impact of environmental destruction resulting from the building of dams in James Bay on the livelihood of directly affected Indigenous communities. It further highlights the persistence and creativity of the Eeyou Cree and Inuit in resisting encroachment on their lands and waters

    Spatial spin-up of fine scales in a regional climate model simulation driven by low-resolution boundary conditions

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    In regional climate modelling, it is well known that domains should be neither too large to avoid a large departure from the driving data, nor too small to provide a sufficient distance from the lateral inflow boundary to allow the full development of the small-scale (SS) features permitted by the finer resolution. Although most practitioners of dynamical downscaling are well aware that the jump of resolution between the lateral boundary condition (LBC) driving data and the nested regional climate model affects the simulated climate, this issue has not been fully investigated. In principle, as the jump of resolution becomes larger, the region of interest in the limited-area domain should be located further away from the lateral inflow boundary to allow the full development of the SS features. A careless choice of domain might result in a suboptimal use of the full finer resolution potential to develop fine-scale features. To address this issue, regional climate model (RCM) simulations using various resolution driving data are compared following the perfect-prognostic Big-Brother protocol. Several experiments were carried out to evaluate the width of the spin-up region (i.e. the distance between the lateral inflow boundary and the domain of interest required for the full development of SS transient eddies) as a function of the RCM and LBC resolutions, as well as the resolution jump. The spin-up distance turns out to be a function of the LBC resolution only, independent of the RCM resolution. When varying the RCM resolution for a given resolution jump, it is found that the spin-up distance corresponds to a fixed number of RCM grid points that is a function of resolution jump only. These findings can serve a useful purpose to guide the choice of domain and RCM configuration for an optimal development of the small scales allowed by the increased resolution of the nested model

    Education and support needs during recovery in acute respiratory distress syndrome survivors

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    Abstract Introduction There is a limited understanding of the long-term needs of survivors of the acute respiratory distress syndrome (ARDS) as they recover from their episode of critical illness. The Timing it Right (TIR) framework, which emphasizes ARDS survivors' journey from the ICU through to community re-integration, may provide a valuable construct to explore the support needs of ARDS survivors during their recovery. Methods Twenty-five ARDS survivors participated in qualitative interviews examining their needs for educational, emotional and tangible support for each phase of the TIR framework. Transcripts were analyzed using framework methodology. Results ARDS survivors' support needs varied across the illness trajectory. During the ICU stay, survivors were generally too ill to require information. The transfer to the general ward was characterized by anxiety surrounding decreased surveillance and concern for future health and treatment. Information needs focused on the events surrounding the acute illness, while physical and emotional needs revolved around physical therapy and psychological support for depression and anxiety. As patients were preparing for hospital discharge, they expressed a desire for specific information about the recovery and rehabilitation process following an episode of ARDS (e.g., outpatient physiotherapy, long-term sequela of the illness). Once in the community, survivors wanted guidance on home care, secondary prevention, and ARDS support groups. Conclusions Our findings support the need for future educational and support interventions to meet the changing needs of ARDS survivors during their recovery
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