Simulation of Heme using DFT+U: a step toward accurate spin-state energetics

We investigate the DFT+U approach as a viable solution to describe the low-lying states of ligated and unligated iron heme complexes. Besides their central role in organometallic chemistry, these compounds represent a paradigmatic case where LDA, GGA, and common hybrid functionals fail to reproduce the experimental magnetic splittings. In particular, the imidazole pentacoordinated heme is incorrectly described as a triplet by all usual DFT flavors. In this study we show that a U parameter close to 4 eV leads to spin transitions and molecular geometries in quantitative agreement with experiments, and that DFT+U represents an appealing tool in the description of iron porphyrin complexes, at a much reduced cost compared to correlated quantum-chemistry methods. The possibility of obtaining the U parameter from first-principles is explored through a self-consistent linear-response formulation. We find that this approach, which proved to be successful in other iron systems, produces in this case some overestimation with respect to the optimal values of U.Comment: To be published in The Journal of Physical Chemistry B 30 pages, 15 figure

Physical activity for children in special school environment

&nbsp;Key Messages1. We assessed children&rsquo;s physical&nbsp;activity (PA) in structured (physical&nbsp;education) and unstructured&nbsp;(recess, lunch, before and after&nbsp;school) periods in special schools&nbsp;and examined its association&nbsp;with modifiable area contextual&nbsp;characteristics.2. Children with disabilities were not&nbsp;highly active, but were more active&nbsp;during recess and lunch periods&nbsp;than at other times including&nbsp;physical education classes.3. Areas were often not accessible&nbsp;during unstructured settings.&nbsp;Children were more active in areas&nbsp;when supervision and organised&nbsp;activities were provided.4. Providing an interactive game&nbsp;during free play did not significantly&nbsp;increase group&rsquo;s PA.5. Children&rsquo;s PA accrual is influenced&nbsp;by contextual characteristics of&nbsp;the school environment. There is a&nbsp;need to make areas more accessible&nbsp;and to use social marketing and&nbsp;programming to attract more users.&nbsp;School and health professionalsshould modify contextual&nbsp;characteristics by providing more&nbsp;direct supervision and organised&nbsp;activities during free play.</div

Hydrogen bonding and coordination in normal and supercritical water from X-ray inelastic scattering

A direct measure of hydrogen bonding in water under conditions ranging from the normal state to the supercritical regime is derived from the Compton scattering of inelastically-scattered X-rays. First, we show that a measure of the number of electrons $n_e$ involved in hydrogen bonding at varying thermodynamic conditions can be directly obtained from Compton profile differences. Then, we use first-principles simulations to provide a connection between $n_e$ and the number of hydrogen bonds $n_{HB}$. Our study shows that over the broad range studied the relationship between $n_e$ and $n_{HB}$ is linear, allowing for a direct experimental measure of bonding and coordination in water. In particular, the transition to supercritical state is characterized by a sharp increase in the number of water monomers, but also displays a significant number of residual dimers and trimers.Comment: 14 pages, 5 figures, 1 tabl

Associations between the neighbourhood environment characteristics and physical activity in older adults with specific types of chronic conditions: The ALECS cross-sectional study

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Recreational destinations and leisure-time physical activity in Chinese urban elders

Conference Theme: Promoting Healthy Eating and Activity WorldwideSession - S36 The relationships between the physical environment and physical activity in older adults: results from four different continents: abstract S36.4PURPOSE: The built environment may impact on elders’ ability to engage in leisure-time physical activity (LTPA). Environmental correlates of LTPA in Chinese older residents of ultra-dense cities are unknown. The main aim of this study was to examine associations of objectively-measured recreational facilities in the neighborhood with LTPA (walking and other forms of activity) in Chinese elders residing in an ultra-dense city. We also examined whether these associations depend on other environmental factors. METHOD: This study was conducted in Hong Kong in …postprin

Neighbourhood environment, physical activity, quality of life and depressive symptoms in Hong Kong older adults: A protocol for an observational study

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Thin-Film Metamaterials called Sculptured Thin Films

Morphology and performance are conjointed attributes of metamaterials, of which sculptured thin films (STFs) are examples. STFs are assemblies of nanowires that can be fabricated from many different materials, typically via physical vapor deposition onto rotating substrates. The curvilinear--nanowire morphology of STFs is determined by the substrate motions during fabrication. The optical properties, especially, can be tailored by varying the morphology of STFs. In many cases prototype devices have been fabricated for various optical, thermal, chemical, and biological applications.Comment: to be published in Proc. ICTP School on Metamaterials (Augsut 2009, Sibiu, Romania

Persistence of Covalent Bonding in Liquid Silicon Probed by Inelastic X-ray Scattering

Metallic liquid silicon at 1787K is investigated using x-ray Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Our results show persistence of covalent bonding in liquid silicon and provide support for the occurrence of theoretically predicted liquid-liquid phase transition in supercooled liquid states. The population of covalent bond pairs in liquid silicon is estimated to be 17% via a maximally-localized Wannier function analysis. Compton scattering is shown to be a sensitive probe of bonding effects in the liquid state.Comment: 5pages, 3 postscript figure