757 research outputs found

    Synthesis and Characterization of CMK Porous Carbons Modified with Metals Applied to Hydrogen Uptake and Storage

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    In this chapter, we have shown that hopeful hydrogen storage material can be obtained by ordered mesoporous carbons (carbons mesostructured from Korea, CMK-1 and CMK-3) and modified with metal/cations species. The pristine CMK-1 and CMK-3 were synthesized by replication using MCM-48 and SBA-15 as hard templates and sucrose as a carbon source. Incorporation of metal species was carried out by wetness impregnation. The mesoporous materials modified were characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), RAMAN, transmission electron microscopy (TEM), and adsorption/desorption N2 isotherms. Carbon modified with metal/cations shows a better capacity for hydrogen uptake than that of the mesoporous carbons. The evolution of high-pressure hydrogen adsorption measured at 77 K shows that composites can significantly enhance hydrogen adsorption capacity and hydrogen storage performance of carbon materials, proving to be prospective candidates for application in hydrogen storage. The improved activity and the larger performance of composite materials are attributed to improved dispersion of uniform metal/cations nanoparticles as well as to efficient use of the support, which may originate a high-surface area and pore volume, allowing a large dispersion of clusters

    Scale-by-scale analysis of probability distributions for global MODIS-AQUA cloud properties: how the large scale signature of turbulence may impact statistical analyses of clouds

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    Means, standard deviations, homogeneity parameters used in models based on their ratio, and the probability distribution functions (PDFs) of cloud properties from the MODerate resolution Infrared Spectrometer (MODIS) are estimated globally as function of averaging scale varying from 5 to 500 km. The properties – cloud fraction, droplet effective radius, and liquid water path – all matter for cloud-climate uncertainty quantification and reduction efforts. Global means and standard deviations are confirmed to change with scale. For the range of scales considered, global means vary only within 3% for cloud fraction, 7% for liquid water path, and 0.2% for cloud particle effective radius. These scale dependences contribute to the uncertainties in their global budgets. Scale dependence for standard deviations and generalized flatness are compared to predictions for turbulent systems. Analytical expressions are identified that fit best to each observed PDF. While the best analytical PDF fit to each variable differs, <i>all</i> PDFs are well described by log-normal PDFs when the mean is normalized by the standard deviation inside each averaging domain. Importantly, log-normal distributions yield significantly better fits to the observations than gaussians at all scales. This suggests a possible approach for both sub-grid and unified stochastic modeling of these variables at all scales. The results also highlight the need to establish an adequate spatial resolution for two-stream radiative studies of cloud-climate interactions

    [Accepted Manuscript] Birth characteristics and all-cause mortality: a sibling analysis using the Uppsala birth cohort multigenerational study.

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    This paper investigates the association between perinatal health and all-cause mortality for specific age intervals, assessing the contribution of maternal socioeconomic characteristics and the presence of maternal-level confounding. Our study is based on a cohort of 12,564 singletons born between 1915 and 1929 at the Uppsala University Hospital. We fitted Cox regression models to estimate age-varying hazard ratios of all-cause mortality for absolute and relative birth weight and for gestational age. We found that associations with mortality vary by age and according to the measure under scrutiny, with effects being concentrated in infancy, childhood or early adult life. For example, the effect of low birth weight was greatest in the first year of life and then continued up to 44 years of age (HR between 2.82 and 1.51). These associations were confirmed in within-family analyses, which provided no evidence of residual confounding by maternal characteristics. Our findings support the interpretation that policies oriented towards improving population health should invest in birth outcomes and hence in maternal health

    Diabetes Mellitus and Depression as Risk Factors for Dementia: SADEM Study

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    Aim: 3Evidence indicates that the comorbidity of dementia with diabetes and depression may affect most cognitive functions. Our chief interest was to examine the patterns of cognitive functioning in individuals diagnosed with dementia, diabetes, and depression as compared with dementia plus diabetes (DDM), or dementia plus depression (DD) and healthy controls

    Waiting for Unruh

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    How long does a uniformly accelerated observer need to interact with a quantum field in order to record thermality in the Unruh temperature? We address this question for a pointlike Unruh–DeWitt detector, coupled linearly to a real Klein–Gordon field of mass and treated within first order perturbation theory, in the limit of large detector energy gap . We first show that when the interaction duration is fixed, thermality in the sense of detailed balance cannot hold as , and this property generalises from the Unruh effect to any Kubo–Martin–Schwinger state satisfying certain technical conditions. We then specialise to a massless field in four spacetime dimensions and show that detailed balance does hold when grows as a power-law in as , provided the switch-on and switch-off intervals are stretched proportionally to and the switching function has sufficiently strong Fourier decay. By contrast, if grows by stretching a plateau in which the interaction remains at constant strength but keeping the duration of the switch-on and switch-off intervals fixed, detailed balance at requires to grow faster than any polynomial in , under mild technical conditions. The results also hold for a static detector in a Minkowski heat bath. The results limit the utility of the large regime as a probe of thermality in time-dependent versions of the Hawking and Unruh effects, such as an observer falling into a radiating black hole. They may also have implications on the design of prospective experimental tests of the Unruh effect

    Care dependency in patients with heart failure: A cross-sectional study in Spain

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    Background: Heart failure (HF) is a progressive and debilitating condition that represents an ever-growing problem for health systems worldwide. HF patients feel that they are a burden on their families, they feel socially isolated and have a low perception of their health. Accordingly, the objectives of this study were to: (1) to explore the profile of care dependency in a representative sample of Spanish HF patients through the Care Dependency Scale (CDS), and (2) to identify correlates of care dependency in this population. Material and Methods: We performed a cross-sectional study of 187 patients admitted for HF decompensation to the Hospital Clínico of Zaragoza (Spain). Results: Only 15% of our sample was highly or completely dependent on care from others. More specifically, our results indicate that HF patients felt a greater level of dependency on care from others when it comes to moving, getting dressed and undressed, maintaining good personal hygiene, participating in daily and recreational activities and being continent. Conclusions: We find association between the CDS categories that present a low score for care dependency in HF patients and the patients’ physical deterioration

    3D characterization of CdSe nanoparticles attached to carbon nanotubes

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    The crystallographic structure of CdSe nanoparticles attached to carbon nanotubes has been elucidated by means of high resolution transmission electron microscopy and high angle annular dark field scanning transmission electron microscopy tomography. CdSe rod-like nanoparticles, grown in solution together with carbon nanotubes, undergo a morphological transformation and become attached to the carbon surface. Electron tomography reveals that the nanoparticles are hexagonal-based with the (001) planes epitaxially matched to the outer graphene layer.Comment: 7 pages, 8 figure

    Quadratic Time-dependent Quantum Harmonic Oscillator

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    We present a Lie algebraic approach to a Hamiltonian class covering driven, parametric quantum harmonic oscillators where the parameter set -- mass, frequency, driving strength, and parametric pumping -- is time-dependent. Our unitary-transformation-based approach provides a solution to the general quadratic time-dependent quantum harmonic model. As an example, we show an analytic solution to the periodically driven quantum harmonic oscillator without the rotating wave approximation; it works for any given detuning and coupling strength regime. For the sake of completeness, we provide an analytic solution to the historical Caldirola--Kanai quantum harmonic oscillator that, in a suitable reference frame, is just a time-independent parametric quantum harmonic oscillator.Comment: 22 pages, 4 figure

    Instituto Internacional de Investigaci ́on e Innovaci ́on del Envejecimiento

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    El Instituto Internacional de Investigaci on e Innovaci on del Envejecimiento es un proyecto transfronterizo y multidisciplinar centrado en la mejora de la calidad de vida de los ancianos mediante el uso de la tecnolog a. En este proyecto colaboran la Universidad de Evora, el Instituto Polit ecnico de Porto Alegre, el Instituto Polit ecnico de Beja, la Administraci on Regional de Salud de Alentejo y la Universidad de Extremadura. Los objetivos del proyecto se centran en comprender los aspectos biom edicos, funcionales y psicol ogicos del envejecimiento; generar nuevos modelos y procesos de cuidado a ancianos y desarrollar soluciones tecnol ogicas que contribuyan a la salud y calidad de vida de los ancianos y a la sostenibilidad de los servicios
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