129 research outputs found

    Land Use Influence on the Characteristics of Groundwater Inputs to the Great Bay Estuary, New Hampshire

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    This research examines the sources and factors affecting nutrient-laden groundwater discharge to the Great Bay Estuary. To further understand this relationship, examination of groundwater residence time, a review of historic land uses, and nitrate source tracking strategies were used. Seven submarine groundwater discharge (SGD) sites were selected, and groundwater monitoring networks were installed to examine the relationship between land use and groundwater quality at the discharge zones. Field activities were performed in the summer and fall of 2003 and 2004. Estuarine water intrusion in groundwater discharge samples confounded the analyses for major ion chemistry and boron isotopes. CFC-derived and modeled groundwater ages in the study area averaged 23.2 years (±15.0 years). CFC analysis enabled correlation of nitrate concentrations at the SGD sites with the historic land use coverage for the years 1974 (for most of the sites) or 1962 (SGD 58.4). Two types of correlation were made: 1) between the agricultural and residential land use for all observed nitrate concentrations in the recharge areas, and 2) correlation with the nitrate concentrations between developed and undeveloped land uses. Both statistical correlations (Kendall’s Tau and Spearman’s Rho) indicated a connection between the increase of residential land use of the last three decades with the high nitrate-bearing groundwater discharging to the Great Bay (NH). The geochemical composition of the SGD water was also investigated by using simple mixing models that attempted to explain the water chemistry characteristics of the targeted SGD sites. Based on these models it was concluded that overburden groundwater comprises 75% to 95% of the groundwater discharging at the SGD sites. A significant correlation (Tau’s, p=0.021) between nitrate-bearing groundwater and CFCderived groundwater ages was detected supporting the hypothesis that high nitrate bearing groundwater will be discharged to the Great Bay in the near future accounting for the increase of residential land use of 1990’s. Continuous monitoring of SGD sites was suggested to be included as part of the periodic environmental quality monitoring activities of the Great Bay. Long-term step-wise sampling for groundwater dating is required to develop a stronger chronological evolution of groundwater nitrate inputs. Further research should concentrate on detailing the overburden water chemistry, flow paths, and nitrogen loading characteristics

    Comprehensive theory of the Lamb shift in light muonic atoms

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    We present a comprehensive theory of the Lamb shift in light muonic atoms, such as Ό\muH, Ό\muD, Ό3\mu^3He+^+, and Ό4\mu^4He+^+, with all quantum electrodynamic corrections included at the precision level constrained by the uncertainty of nuclear structure effects. This analysis can be used in the global adjustment of fundamental constants and in the determination of nuclear charge radii. Further improvements in the understanding of electromagnetic interactions of light nuclei will allow for a promising test of fundamental interactions by comparison with "normal" atomic spectroscopy, in particular, with H-D and 3^3He-4^4He isotope shifts.Comment: 21 pages, 4 figures, expanded introductio

    First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He

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    The first direct mass-measurement of 6^{6}He has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of 8^{8}He was determined with improved precision over our previous measurement. The obtained masses are mm(6^{6}He) = 6.018 885 883(57) u and mm(8^{8}He) = 8.033 934 44(11) u. The 6^{6}He value shows a deviation from the literature of 4σ\sigma. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and 1.959(16) fm for 6^{6}He and 8^{8}He respectively. We present a detailed comparison to nuclear theory for 6^6He, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.Comment: 4 pages, 2 figure

    Electric dipole polarizability of 40^{40}Ca

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    The electric dipole strength distribution in 40^{40}Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at very forward angles. Combined with total photoabsorption data at higher excitation energy, this enables an extraction of the electric dipole polarizability αD\alpha_\mathrm{D}(40^{40}Ca) = 1.92(17) fm3^3. Together with the measured αD\alpha_{\rm D} in 48^{48}Ca, it provides a stringent test of modern theoretical approaches, including coupled cluster calculations with chiral effective field theory interactions and state-of-the art energy density functionals. The emerging picture is that for this medium-mass region dipole polarizabilities are well described theoretically, with important constraints for the neutron skin in 48^{48}Ca and related equation of state quantities.Comment: 6 pages, 3 figure

    Machine learning in predicting respiratory failure in patients with COVID-19 pneumonia - challenges, strengths, and opportunities in a global health emergency.

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    Aims- The aim of this study was to estimate a 48 hour prediction of moderate to severe respiratory failure, requiring mechanical ventilation, in hospitalized patients with COVID-19 pneumonia. Methods- This was an observational study that comprised consecutive patients with COVID-19 pneumonia admitted to hospital from 21 February to 6 April 2020. The patients\u2019 medical history, demographic, epidemiologic and clinical data were collected in an electronic patient chart. The dataset was used to train predictive models using an established machine learning framework leveraging a hybrid approach where clinical expertise is applied alongside a data-driven analysis. The study outcome was the onset of moderate to severe respiratory failure defined as PaO 2 /FiO 2 ratio <150 mmHg in at least one of two consecutive arterial blood gas analyses in the following 48 hours. Shapley Additive exPlanations values were used to quantify the positive or negative impact of each variable included in each model on the predicted outcome. Results- A total of 198 patients contributed to generate 1068 usable observations which allowed to build 3 predictive models based respectively on 31-variables signs and symptoms, 39-variables laboratory biomarkers and 91-variables as a composition of the two. A fourth \u201cboosted mixed model\u201d included 20 variables was selected from the model 3, achieved the best predictive performance (AUC=0.84) without worsening the FN rate. Its clinical performance was applied in a narrative case report as an example. Conclusion- This study developed a machine model with 84% prediction accuracy, which is able to assist clinicians in decision making process and contribute to develop new analytics to improve care at high technology readiness levels

    Neutrino-driven wind simulations and nucleosynthesis of heavy elements

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    Neutrino-driven winds, which follow core-collapse supernova explosions, present a fascinating nuclear astrophysics problem that requires understanding advanced astrophysics simulations, the properties of matter and neutrino interactions under extreme conditions, the structure and reactions of exotic nuclei, and comparisons against forefront astronomical observations. The neutrino-driven wind has attracted vast attention over the last 20 years as it was suggested to be a candidate for the astrophysics site where half of the heavy elements are produced via the r-process. In this review, we summarize our present understanding of neutrino-driven winds from the dynamical and nucleosynthesis perspectives. Rapid progress has been made during recent years in understanding the wind with improved simulations and better micro physics. The current status of the fields is that hydrodynamical simulations do not reach the extreme conditions necessary for the r-process and the proton or neutron richness of the wind remains to be investigated in more detail. However, nucleosynthesis studies and observations point already to neutrino-driven winds to explain the origin of lighter heavy elements, such as Sr, Y, Zr.Comment: Submitted to: J. Phys. G: Nucl. Phy

    Uncertainty in land-use adaptation persists despite crop model projections showing lower impacts under high warming

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    Climate change is expected to impact crop yields and alter resource availability. However, the understanding of the potential of agricultural land-use adaptation and its costs under climate warming is limited. Here, we use a global land system model to assess land-use-based adaptation and its cost under a set of crop model projections, including CO2 fertilization, based on climate model outputs. In our simulations of a low-emissions scenario, the land system responds through slight changes in cropland area in 2100, with costs close to zero. For a high emissions scenario and impacts uncertainty, the response tends toward cropland area changes and investments in technology, with average adaptation costs between −1.5 and +19 US$05 per ton of dry matter per year. Land-use adaptation can reduce adverse climate effects and use favorable changes, like local gains in crop yields. However, variance among high-emissions impact projections creates challenges for effective adaptation planning

    Controle massal da broca‑do‑cafĂ© com armadilhas de garrafa Pet vermelha em cafeeiro

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    The objective of this work was to evaluate the efficacy of red PET‑bottle traps, containing attractive alcoholic volatile compounds, in the mass control of coffee berry borer (Hypothenemus hampei). The evaluations were carried out in four coffee crops, during two years. Nine hundred PET‑bottle traps, painted red, were distributed in three of the four coffee crops; one crop without traps was used as a control. Holes drilled into berries (%) were determined in these crops. There was a reduction in drilled berries in crops with traps, from the 2007/2008 harvest to the 2008/2009 harvest. The highest coffee berry borer densities in traps was observed in the flowering and small‑green berries stages. The red PET‑bottle trap is efficient in the mass control of the coffee berry borer population, since it reduces the percentage of drilled berries in 57%; however, this reduction is not enough to keep borer densities below the control level.O objetivo deste trabalho foi avaliar a eficĂĄcia de armadilha de garrafa Pet vermelha contendo compostos volĂĄteis alcoĂłlicos atrativos, no controle massal da broca‑do‑cafĂ© (Hypothenemus hampei). As avaliaçÔes foram realizadas em quatro lavouras de cafĂ©, durante dois anos. Foram distribuĂ­das 900 armadilhas de garrafa Pet, pintadas de vermelho, em trĂȘs das quatro lavouras; uma lavoura sem armadilhas foi usada como controle. O broqueamento dos frutos (%) foi determinado nessas lavouras. Houve redução do broqueamento de frutos nas lavouras com armadilhas, da safra 2007/2008 para a safra 2008/2009. As maiores densidades da broca‑do‑cafĂ© nas armadilhas foram observadas nos estĂĄdios de floração e de frutos chumbinho. A armadilha de garrafa Pet vermelha Ă© eficaz no controle massal da população da broca‑do‑cafĂ©, por reduzir a percentagem de frutos broqueados em 57%; entretanto, essa redução nĂŁo Ă© suficiente para manter as densidades da broca abaixo do nĂ­vel de controle
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