931 research outputs found

    Barium Stars: Theoretical Interpretation

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    Barium stars are extrinsic Asymptotic Giant Branch (AGB) stars. They present the s-enhancement characteristic for AGB and post-AGB stars, but are in an earlier evolutionary stage (main sequence dwarfs, subgiants, red giants). They are believed to form in binary systems, where a more massive companion evolved faster, produced the s-elements during its AGB phase, polluted the present barium star through stellar winds and became a white dwarf. The samples of barium stars of Allen & Barbuy (2006) and of Smiljanic et al. (2007) are analysed here. Spectra of both samples were obtained at high-resolution and high S/N. We compare these observations with AGB nucleosynthesis models using different initial masses and a spread of 13C-pocket efficiencies. Once a consistent solution is found for the whole elemental distribution of abundances, a proper dilution factor is applied. This dilution is explained by the fact that the s-rich material transferred from the AGB to the nowadays observed stars is mixed with the envelope of the accretor. We also analyse the mass transfer process, and obtain the wind velocity for giants and subgiants with known orbital period. We find evidence that thermohaline mixing is acting inside main sequence dwarfs and we present a method for estimating its depth.Comment: 8 pages, 11 figures, 6 table

    First-trimester 3-dimensional power Doppler of the uteroplacental circulation space: a potential screening method for preeclampsia

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    ObjectiveThe objective of the study was to compare 3-dimensional power Doppler (3DPD) of the uteroplacental circulation space (UPCS) in the first trimester between women who develop preeclampsia (PEC) and those who do not and to assess the 3DPD method as a screening tool for PEC.Study DesignThis was a prospective observational study of singleton pregnancies at 10 weeks 4 days to 13 weeks 6 days. The 3DPD indices, vascularization index (VI), flow index (FI), and vascularization flow index (VFI), were determined on a UPSC sphere biopsy with the virtual organ computer-aided analysis (VOCAL) program.ResultsOf 277 women enrolled, 24 developed PEC. The 3DPD indices were lower in women who developed PEC. The area under the receiver-operating characteristics curve for the prediction of PEC was 78.9%, 77.6%, and 79.6% for VI, FI, and VFI, respectively.ConclusionPatients who develop PEC have lower 3DPD indices of their UPCS during the first trimester. Our findings suggest that this ultrasonographic tool has the potential to predict the development of PEC

    Effects of the built environment on physical activity: a systematic review of longitudinal studies taking sex/gender into account

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    Background Individual health behavior is related to environmental and social structures. To promote physical activity (PA) effectively, it is necessary to consider structural influences. Previous research has shown the relevance of the built environment. However, sex/gender differences have yet not been considered. The aim of this systematic review was to identify built environmental determinants of PA by taking sex/gender into account. Methods A systematic literature search was carried out using six electronic databases (PubMed, CINAHL, SportDiscus, PsycInfo, Scopus, Web of Knowledge) to identify studies analyzing the effect of changes in the built environment on PA, taking sex/gender into account. To be included, studies had to be based on quantitative data and a longitudinal study design. Changes in the built environment had to be objectively assessed. The methodological quality of the studies was examined using the QualSyst tool for examining risk of bias. Results In total, 36 studies published since 2000 were included in this review. The data synthesis revealed that the majority of reviewed studies found the built environment to be a determinant of PA behavior for both, males and females, in a similar way. Creating a new infrastructure for walking, cycling, and public transportation showed a positive effect on PA behavior. Findings were most consistent for the availability of public transport, which was positively associated with overall PA and walking. The improvement of walking and cycling infrastructure had no effect on the overall level of PA, but it attracted more users and had a positive effect on active transportation. In women, the availability of public transport, safe cycling lanes, housing density, and the distance to daily destinations proved to be more relevant with regard to their PA behavior. In men, street network characteristics and road environment, such as intersection connectivity, local road density, and the presence of dead-end roads, were more important determinants of PA. Conclusion This review sheds light on the relevance of the built environment on PA. By focusing on sex/gender differences, a new aspect was addressed that should be further analyzed in future research and considered by urban planners and other practitioners

    How to disseminate national recommendations for physical activity: a qualitative analysis of critical change agents in Germany

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    Physical activity recommendations are reached by only a small part of the population. A common problem is that research findings on public health-related topics such as physical activity promotion are oftentimes not translated into practice. The involvement of relevant stakeholders, such as change agents (role models, decision-makers, and/or knowledge mediators), is a common strategy to implement physical activity recommendations in specific settings, as they have the necessary knowledge of contextual factors. However, dissemination and implementation of physical activity recommendations are often prevented by focusing exclusively on the health sector and by underestimating the individual perceptions and needs of change agents. Therefore, the purpose of this study was to address the problem of how physical activity recommendations can be translated into practice through comprehensive consideration of the situation and context of change agents from various sectors of society at different administrative levels. This allows for deriving recommendations for action on how a national dissemination strategy of physical activity recommendations should be designed. Methods Qualitative expert interviews were conducted with change agents from different sectors of society and administrative levels in Germany (N = 21). Case selection took place via a sampling plan. The interviews were recorded, transcribed verbatim, and analysed by two trained researchers using qualitative content analysis. Results The change agents’ perceived relevance of physical activity and physical activity promotion and their knowledge of physical activity recommendations varied across different sectors. Nine themes were identified covering the change agents’ needs for the implementation of physical activity recommendations: strengthening of political will and cooperation, availability of public space for physical activity, change in awareness and health education, professional qualification, financial incentives, development of physical activity-promoting programmes and structures, provision of resources, bridging the theory–practice gap, and knowledge of physical activity recommendations. Conclusions This exploratory study contributes to the development of an evidence-based dissemination strategy of physical activity recommendations involving change agents from various sectors. Cross-sectoral needs and obstacles were identified indicating gaps that have to be addressed. Future research should choose practice-oriented approaches to develop dissemination strategies that are adapted to the needs of local contexts

    Quantum entanglement between electronic and vibrational degrees of freedom in molecules

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    We consider the quantum entanglement of the electronic and vibrational degrees of freedom in molecules with a tendency towards double welled potentials using model coupled harmonic diabatic potential-energy surfaces. The von Neumann entropy of the reduced density matrix is used to quantify the electron-vibration entanglement for the lowest two vibronic wavefunctions in such a bipartite system. Significant entanglement is found only in the region in which the ground vibronic state contains a density profile that is bimodal (i.e., contains two separate local minima). However, in this region two distinct types of entanglement are found: (1) entanglement that arises purely from the degeneracy of energy levels in the two potential wells and which is destroyed by slight asymmetry, and (2) entanglement that involves strongly interacting states in each well that is relatively insensitive to asymmetry. These two distinct regions are termed fragile degeneracy-induced entanglement and persistent entanglement, respectively. Six classic molecular systems describable by two diabatic states are considered: ammonia, benzene, semibullvalene, pyridine excited triplet states, the Creutz-Taube ion, and the radical cation of the "special pair" of chlorophylls involved in photosynthesis. These chemically diverse systems are all treated using the same general formalism and the nature of the entanglement that they embody is elucidated

    Specific characteristics of STEMI in COVID-19 patients and their practical implications

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    ST-elevation myocardial infarction (STEMI) is one of the cardiac emergencies whose management has been most challenged by the COVID-19 pandemic. Patients presenting with the “lethal combo” of STEMI and concomitant SARS-CoV-2 infection have faced dramatic issues related to the need for self-isolation, systemic inflammation with multi-organ disease and difficulties to obtain timely diagnosis and treatment. The interplay between these and other factors has partly neutralized the major advances in STEMI care achieved in the last decades, significantly impairing prognosis in these patients. In the present review article, we will provide an overview on mechanisms of myocardial injury, specific clinical and angiographic characteristics and contemporary management in different settings of STEMI patients with COVID-19, alongside the inherent implications in terms of in-hospital mortality and short-term clinical outcomes

    How to predict conduction disturbances after transcatheter aortic valve replacement?

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    Transcatheter aortic valve replacement (TAVI) has evolved into the gold standard management option for high-risk patients with severe aortic stenosis. Despite procedural, electrocardiographic and clinical predictors of important post-procedural conduction disturbances (left bundle branch block [LBBB] and high-degree atrioventricular block [HAVB]) being identified, and continuous technological refinement of transcatheter aortic valves, the rate of post-procedural conduction disturbance remains high, and challenging to manage. New strategies are required to reduce the overall rate of post-procedural PPI. In this article, we will review the incidence, predictive factors, and clinical implications of conduction disturbances after TAVI

    Assessing incomplete deprotection of microarray oligonucleotides in situ

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    En masse analysis of gene structure and function by array technologies will have a lasting and profound effect on biology and medicine. This impact can be compromised by low quality of probes within arrays, which we show can be caused by incomplete removal of chemical protecting groups. To solve this quality control problem, we present a sensitive, specific and facile method to detect these groups in situ on arrays using monoclonal antibodies and existing instrumentation. Screening of microarrays with these monoclonal antibodies should guide the consideration given to data derived from these and should enhance the accuracy of the results obtained

    DFT study of polar Zno (000-1) surface stability due to transition metals (Co, Mn) as dopants

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    This work presents a study, through the density functional theory (DFT), of the effect of Coand Mn as dopants -substitutional and interstitial- on the surface of polar ZnO. Formation energy, ofthese doped surfaces, was calculated and it is performed an analysis of the magnetic changes inducedby these dopant species. Moreover, the geometric changes were studied. From the formation energyvalues obtained, it is observed that the interstitial location in the first bilayer is more favorable forboth dopants. The highest magnetic moment values are obtained for substitutional Co and interstitialMn. Finally, both impurities produce a weakening of the surface zinc-oxygen bonds.En este trabajo hemos estudiado, mediante la teoría del funcional de la densidad (DFT), el efecto de Co y Mn como dopantes -sustitucionales e intersticiales- en la superficie de ZnO polar. Se calcularon energías de formación de estas superficies dopadas, y se realizó un análisis de los cambios magnéticos que estas especies inducen. También se estudiaron los cambios geométricos producidos por estos dopantes. En cuanto a la energía de formación, para ambos dopantes, la ubicación intersticial en la primera bicapa es más favorable respecto a la sustitucional. El mayor valor de momento magnético se obtiene en Co como impureza sustitucional, mientras que intersticial para la especie Mn. Ambas especies producen un debilitamiento de los enlaces zinc 3 oxígenos superficiales.Fil: Reimers, Walter Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Gallegos, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Luna, Carla Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Damonte, Laura Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Sambeth, Jorge Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Marchetti, Jorge Mario. Norwegian University of Life Sciences; Noruega. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentin

    Vitamin D-related gene polymorphisms, plasma 25-hydroxyvitamin D, and breast cancer risk

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    Studies of vitamin D pathway genetic variants in relation to cancer risk have been inconsistent. We examined associations between vitamin D-related genetic polymorphisms, plasma 25-hydroxyvitamin D [25(OH)D], and breast cancer risk
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