Hydrogen Dissociation and Diffusion on Ni and Ti -doped Mg(0001) Surfaces

It is well known, both theoretically and experimentally, that alloying MgH$_2$ with transition elements can significantly improve the thermodynamic and kinetic properties for H$_2$ desorption, as well as the H$_2$ intake by Mg bulk. Here we present a density functional theory investigation of hydrogen dissociation and surface diffusion over Ni-doped surface, and compare the findings to previously investigated Ti-doped Mg(0001) and pure Mg(0001) surfaces. Our results show that the energy barrier for hydrogen dissociation on the pure Mg(0001) surface is high, while it is small/null when Ni/Ti are added to the surface as dopants. We find that the binding energy of the two H atoms near the dissociation site is high on Ti, effectively impeding diffusion away from the Ti site. By contrast, we find that on Ni the energy barrier for diffusion is much reduced. Therefore, although both Ti and Ni promote H$_2$ dissociation, only Ni appears to be a good catalyst for Mg hydrogenation, allowing diffusion away from the catalytic sites. Experimental results corroborate these theoretical findings, i.e. faster hydrogenation of the Ni doped Mg sample as opposed to the reference Mg or Ti doped Mg.Comment: 17 pages, 15 figures, to appear in Journal of Chemical Physic

A public dataset of 24-H multi-levels psycho-physiological responses in young healthy adults

Wearable devices now make it possible to record large quantities of physiological data, which can be used to obtain a clearer view of a person’s health status and behavior. However, to the best of our knowledge, there are no open datasets in the literature that provide psycho-physiological data. The Multilevel Monitoring of Activity and Sleep in Healthy people (MMASH) dataset presented in this paper provides 24 h of continuous psycho-physiological data, that is, inter-beat intervals data, heart rate data, wrist accelerometry data, sleep quality index, physical activity (i.e., number of steps per second), psychological characteristics (e.g., anxiety status, stressful events, and emotion declaration), and sleep hormone levels for 22 participants. The MMASH dataset will enable the investigation of possible relationships between the physical and psychological characteristics of people in daily life. Data were validated through different analyses that showed their compatibility with the literature

Thermal and electrical conductivity of iron at Earth's core conditions

The Earth acts as a gigantic heat engine driven by decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes, and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing to grow the solid inner core, and on chemical convection due to light elements expelled from the liquid on freezing. The power supplied to the geodynamo, measured by the heat-flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat-flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent difficulties in experimentation and theory. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles- the first directly computed values that do not rely on estimates based on extrapolations. The mixtures of Fe, O, S, and Si are taken from earlier work and fit the seismologically-determined core density and inner-core boundary density jump. We find both conductivities to be 2-3 times higher than estimates in current use. The changes are so large that core thermal histories and power requirements must be reassessed. New estimates of adiabatic heat-flux give 15-16 TW at the CMB, higher than present estimates of CMB heat-flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted and future models of mantle evolution must incorporate a high CMB heat-flux and explain recent formation of the inner core.Comment: 11 pages including supplementary information, two figures. Scheduled to appear in Nature, April 201

Structure of nanoparticles embedded in micellar polycrystals

We investigate by scattering techniques the structure of water-based soft composite materials comprising a crystal made of Pluronic block-copolymer micelles arranged in a face-centered cubic lattice and a small amount (at most 2% by volume) of silica nanoparticles, of size comparable to that of the micelles. The copolymer is thermosensitive: it is hydrophilic and fully dissolved in water at low temperature (T ~ 0{\deg}C), and self-assembles into micelles at room temperature, where the block-copolymer is amphiphilic. We use contrast matching small-angle neuron scattering experiments to probe independently the structure of the nanoparticles and that of the polymer. We find that the nanoparticles do not perturb the crystalline order. In addition, a structure peak is measured for the silica nanoparticles dispersed in the polycrystalline samples. This implies that the samples are spatially heterogeneous and comprise, without macroscopic phase separation, silica-poor and silica-rich regions. We show that the nanoparticle concentration in the silica-rich regions is about tenfold the average concentration. These regions are grain boundaries between crystallites, where nanoparticles concentrate, as shown by static light scattering and by light microscopy imaging of the samples. We show that the temperature rate at which the sample is prepared strongly influence the segregation of the nanoparticles in the grain-boundaries.Comment: accepted for publication in Langmui

THREE-DIMENSIONAL SPORT MOVEMENT ANALYSIS BY MEANS OF FREE FLOATING TV CAMERAS WITH VARIABLE OPTICS

INTRODUCTION: Video analysis and off-line manual digitalization is usually used for 2-D and 3-D studies of human movement in sport science. The main advantage of this approach, with respect to the recourse to opto-electronic automatic motion analyzers, is the high flexibility in system set-up, the avoidance of marking procedures and the possibility of successful operation in a wide range of environmental situations. Such features turn out to be particularly important for recordings to be performed in the frame of high-level competition, when the experimental set-up must be adapted to a pre-defined competitive environment, without interfering with the performances of the athletes. However, when methods proper to conventional close-range photogrammetry are used, most of the advantages offered by the flexibility of video analysis are not obtained. Particularly critical is the restriction of the useful calibrated volume to the field of view made possible by fixed pairs of TV cameras. In this case the useful sequence of images (where the dimension of the acquired subject allows one to limit macroscopic digitalization errors) is often insufficient for the analysis of a complete movement cycle. This limitation hinders a fruitful application of video analysis in the frame of sport activities (alpine and Nordic skiing, swimming, track and field) in which the execution of the particular technical movement is performed within a large physical space. A solution to the problem is proposed based on the use of free moving and zooming cameras. The corresponding dedicated software for repeated calibration based on Direct Linear Transformation (DLT)(Abdel Aziz and Karara, 1971) is described. Results of recording performed in the laboratory are discussed aiming at the validation of the implemented method. The description of the methodology for the recording of sport activities and the presentation of the related results confirm the operational feasibility of the proposed method and the reliability of the resulting quantitative kinematics analysis

Qualidade nos cuidados de enfermagem: que realidade?

Este trabalho de revisão bibliográfica foi realizado no âmbito do IX Programa de Doutoramento em Enfermagem, do Instituto de Ciências da Saúde da Universidade Católica Portuguesa do Porto. A existência de sistemas de saúde que garantam a prestação efectiva de cuidados de qualidade é, actualmente uma das prioridades de variadas organizações, entre elas constam: a ODCE, OMS, SNS e OE. A qualidade dos cuidados de enfermagem para além da importância que tem para a instituição e doente, deve ter uma importância máxima para o prestador de cuidados. O enfermeiro deve almejar a qualidade em cada gesto realizado, deve procurar que o desempenho da sua função seja mais do que uma simples execução de tarefas (Ascensão, 2010). Objectivos: Conhecer o estado da arte em língua portuguesa em termos da qualidade dos cuidados de enfermagem. Conhecer as metodologias usadas no estudo da qualidade dos cuidados de enfermagem. Material e Tratou-se de uma revisão de literatura tendo por finalidade identificar o conhecimento existente sobre esta temática. Foi realizada uma pesquisa na base de dados B-On, tendo em conta Dissertações de Licenciatura, de Mestrado, de Doutoramento e artigos, disponíveis em texto integral, que tivessem como palavras-chave no título: Cuidados, Qualidade e Enfermagem. A pesquisa foi efectuada para documentos em português entre os anos de 2000 e 2013. Resultados: A pesquisa encontrou, na B-on dezoito documentos, artigos de periódicos da área da saúde. Destes dezoito um artigo encontrava-se em quadruplicado e outro em duplicado. Quatro deles não foram incluídos por não dizerem respeito à área em questão. No final, após aplicação dos critérios de pesquisa, reunimos um conjunto de dez documentos (cinco teses, três artigos e duas comunicações em conferências) que se constituíram como o nosso corpus de análise. Os documentos estão disponíveis em texto integral. Discussão e Conclusão: Depois de analisados os documentos encontrados concluímos que os enfermeiros proporcionam um importante contributo na melhoria da qualidade das organizações (Aleixo, 2010). Conclui-se também que existe uma urgência na execução de ações de educação continuada, uma vez que a formação é considerada instrumento de reflexão e mudança, sendo esta um dos pilares para a prestação de cuidados de enfermagem de excelência (Padilha, 2010; Castro, 2007). Paralelamente, conclui-se que os principais resultados da qualidade dos cuidados de enfermagem envolvem mais trabalho e decisão em equipa multidisciplinar, mais recursos materiais e humanos e melhores condições físicas (Carvalhais, 2010)