3,185 research outputs found

    Analysis of a three flavor neutrino oscillation fit to recent Super-Kamiokande data

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    We have analyzed the most recent available Super-Kamiokande data in a three flavor neutrino oscillation model. We have here neglected possible matter effects and performed a fit to atmospheric and solar Super-Kamiokande data. We have investigated a large parameter range, where the mixing angles were restricted to 0≤θi≤π/20 \leq \theta_i \leq \pi/2, i=1,2,3 i=1,2,3, and the mass squared differences were taken to be in the intervals 10−11eV2≤Δm2≤10−2eV210^{-11} {\rm eV}^2 \leq \Delta m^2 \leq 10^{-2} {\rm eV}^2 and 10−4eV2≤ΔM2≤10eV210^{-4} {\rm eV}^2 \leq \Delta M^2 \leq 10 {\rm eV}^2. This yielded a best solution characterized by the parameter values θ1≃45∘\theta_1 \simeq 45^\circ, θ2≃10∘\theta_2 \simeq 10^\circ, θ3≃45∘\theta_3 \simeq 45^\circ, Δm2≃4.4×10−10eV2\Delta m^2 \simeq 4.4 \times 10^{-10} {\rm eV}^2, and ΔM2≃1.01×10−3eV2\Delta M^2 \simeq 1.01 \times 10^{-3} {\rm eV}^2, which shows that the analyzed experimental data speak in favor of a bimaximal mixing scenario with one of the mass squared differences in the ``just-so'' domain and the other one in the range capable of providing a solution to the atmospheric neutrino problem.Comment: 13 pages, 5 figures; Eq. (22) and Ref. [1] correcte

    Metformin, Sulfonylureas, or Other Antidiabetes Drugs and the Risk of Lactic Acidosis or Hypoglycemia

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    OBJECTIVE: Lactic acidosis has been associated with use of metformin. Hypoglycemia is a major concern using sulfonylureas. The aim of this study was to compare the risk of lactic acidosis and hypoglycemia among patients with type 2 diabetes using oral antidiabetes drugs. RESEARCH DESIGN AND METHODS: This study is a nested case-control analysis using the U.K.-based General Practice Research Database to identify patients with type 2 diabetes who used oral antidiabetes drugs. Within the study population, all incident cases of lactic acidosis and hypoglycemia were identified, and hypoglycemia case subjects were matched to up to four control patients based on age, sex, practice, and calendar time. RESULTS: Among the study population of 50,048 type 2 diabetic subjects, six cases of lactic acidosis during current use of oral antidiabetes drugs were identified, yielding a crude incidence rate of 3.3 cases per 100,000 person-years among metformin users and 4.8 cases per 100,000 person-years among users of sulfonylureas. Relevant comorbidities known as risk factors for lactic acidosis could be identified in all case subjects. A total of 2,025 case subjects with hypoglycemia and 7,278 matched control subjects were identified. Use of sulfonylureas was associated with a materially elevated risk of hypoglycemia. The adjusted odds ratio for current use of sulfonylureas was 2.79 (95% CI 2.23–3.50) compared with current metformin use. CONCLUSIONS: Lactic acidosis during current use of oral antidiabetes drugs was very rare and was associated with concurrent comorbidity. Hypoglycemic episodes were substantially more common among sulfonylurea users than among users of metformin.Merck SA, Lyon, Franc

    Tunneling induced electron transfer between separated protons

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    We study electron transfer between two separated nuclei using local control theory. By conditioning the algorithm in a symmetric system formed by two protons, one can favored slow transfer processes, where tunneling is the main mechanism, achieving transfer efficiencies close to unity assuming fixed nuclei. The solution can be parametrized using sequences of pump and dump pi pulses, where the pump pulse is used to excite the electron to a highly excited state where the time for tunneling to the target nuclei is on the order of femtoseconds. The time delay must be chosen to allow for full population transfer via tunneling, and the dump pulse is chosen to remove energy from the state to avoid tunneling back to the original proton. Finally, we study the effect of the nuclear kinetic energy on the transfer efficiency. Even in the absence of relative motion between the protons, the spreading of the nuclear wave function is enough to reduce the yield of electronic transfer to less than one half.Comment: 7 pages, 8 figure

    Use of depot medroxyprogesterone acetate and fracture risk

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    Depot medroxyprogesterone acetate (DMPA), which has a high rate of use among teenagers in Europe and the United States, has been associated with impaired bone mineral acquisition during adolescence and accelerated bone loss in later life. Studies on the association between DMPA use and fracture risk are limited.; We aimed at evaluating the relationship between use of hormonal contraceptives, specifically DMPA, and fracture risk.; We conducted a case-control analysis using the United Kingdom-based General Practice Research Database.; Participants were females aged 20-44 yr with an incident fracture diagnosis between 1995 and 2008.; Odds ratios (OR) with 95% confidence intervals (CI) of incident fracture in relation to exposure to DMPA or combined oral contraceptives were assessed. Adjustments were made for smoking, body mass index, and additional potential confounders.; We identified 17,527 incident fracture cases and 70,130 control patients (DMPA exposure: 11 and 8%, respectively). Compared with nonuse, current use of one to two, three to nine, or 10 or more DMPA prescriptions yielded adjusted OR for fractures of 1.18 (95% CI = 0.93-1.49), 1.36 (95% CI = 1.15-1.60), and 1.54 (95% CI = 1.33-1.78), respectively. Fracture risk was highest after longer treatment duration (<2-3 yr), and there was no difference in patients below and above the age of 30 yr. For users of combined estrogen-containing oral contraceptives, the OR were around 1.; This population-based study suggests that use of DMPA is associated with a slightly increased risk of fractures

    Antibiotics in the Prevention and Treatment of Coronary Heart Disease

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    Seroepidemiology, pathology, and animal studies provide evidence for a possible association between Chlamydia pneumoniae infections and atherosclerosis, coronary heart disease, and myocardial infarction. If this association exists, then exposure to certain antibiotics may positively affect the clinical course after an acute ischemic cardiac event (secondary prevention) and affect the risk of developing a first-time myocardial infarction (primary prevention). Preliminary evidence from clinical trials suggests that treatment with new macrolide antibiotics may improve outcome after ischemic events, and evidence from a large case-control analysis indicates that exposure to tetracyclines or quinolones may reduce the risk of developing a first-time myocardial infarction. However, antibiotics for the treatment or prevention of ischemic heart disease must not be recommended yet. This review of published studies briefly summarizes the currently available literature on the effects of antibiotics on the risk of developing coronary heart disease and myocardial infarctio

    The consequences of spatial environmental variability on dispersal and on the spatial distribution of species

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    A central goal in ecology is to identify and understand causal factors that lead to the expansion or contraction of species ranges. Spatio - temporal population dynamics depend on biotic and abiotic environmental conditions, local demography, dispersal behaviour, and phenotypic variation. In particular understanding dispersal behaviour turns out to be a tough problem, because complex feedback loops between dispersal, local demography, and individual variations can arise. Furthermore, previous attempts to understand dispersal by reducing the complexity either in space or time have often resulted in a disregard of these feedbacks. The aim of this thesis was to investigate the influence of dispersal on spatio-temporal population dynamics with models and experiments that explicitly consider the multi causality of dispersal. The thesis is composed of three different studies: Firstly, for an active dispersing species, a plausible factor affecting dispersal behaviour could be personal information. Birds, for example, might gather information on future nest sites and, as a result, individuals differ in the amount and quality of information they possess for use in reaching a dispersal decision. We manipulated the information available to flycatchers (Ficedula hypoleuca) in a field experiment and we found that individuals which were longer exposed to the information altered dispersal behaviour to a greater extent, but only at a local spatial extent. Secondly, models of sex-biased dispersal rarely take space into account. With a computer simulation model, we showed that acknowledging the spatial distribution of the sexes has consequences for the evolutionary outcome of the model leading to selection of more similar dispersal behaviour among the two sexes. Thirdly, models of invasion spread rate often ignore the dependency of dispersal on environmental heterogeneity. We expanded on a reaction-diffusion model to improve this deficit and show that the invasion dynamics of an ecto-parasite (deer ked, Lipoptena cervi) is dependent on the local density of its main host, moose (Alces alces), across its Finnish range. In conclusion, these studies point at the necessity to consider interactions between dispersal and environmental variability, feedbacks between causal factor of dispersal, and realistic assumptions about space and time in order to solve the conundrum of factors determining the spatio-temporal distribution of species.Ei saatavill

    Lagrangian model using CFD flow data to predict the current-voltage characteristics of a solid oxide fuel cell repeat unit

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    A model framework is presented to predict the current-voltage (I-U) characteristics and hence the electrical performance of a solid oxide fuel cell (SOFC) repeat unit, i. e., a planar SOFC with adjacent current collector plates. The model uses as input residence times obtained from 3D CFD data for the fuel flowing through the anodic gas channels of a current collector plate. These residence times are then used by an electrochemical model to predict the fuel conversion along different flow paths for various electrical loads. This way, the overall (I-U) behaviour of the repeat unit follows from combining the fuel conversion rates (and respective electrical currents) for the individual flow paths. Since we use a Lagrangian reference frame for the electrochemical model, for a given electrical load, only a simple time-integration of a first-order ODE is required. Therefore, this modelling approach is very efficient and well suited for extensive parameter studies, e. g., to optimise the fuel residence times with respect to the electrical performance of the repeat unit. To ensure its reliability, the model has been validated by comparison with both experimental data and other (I-U) models
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