2,158 research outputs found

    Computer vision for Pedestrian detection using Histograms of Oriented Gradients

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    Proyecto de visión por computador para la detección de peatones, entendidas como personas en posición vertical, en imágenes estáticas. La detección se basa en el descriptor propuesto por Dalal & Triggs; Histograma de gradientes orientados (HOG) más un clasificador SVM

    A hydrated ion model of [UO2]2+ in water: Structure, dynamics, and spectroscopy from classical molecular dynamics

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    A new ab initio interaction potential based on the hydrated ion concept has been developed to obtain the structure, energetics, and dynamics of the hydration of uranyl in aqueous solution. It is the first force field that explicitly parameterizes the interaction of the uranyl hydrate with bulk water molecules to accurately define the second-shell behavior. The [UO2(H2O)5 ] 2+ presents a first hydration shell U–O average distance of 2.46 Å and a second hydration shell peak at 4.61 Å corresponding to 22 molecules using a coordination number definition based on a multisite solute cavity. The second shell solvent molecules have longer mean residence times than those corresponding to the divalent monatomic cations. The axial regions are relatively de-populated, lacking direct hydrogen bonding to apical oxygens. Angle-solved radial distribution functions as well as the spatial distribution functions show a strong anisotropy in the ion hydration. The [UO2(H2O)5 ] 2+ solvent structure may be regarded as a combination of a conventional second hydration shell in the equatorial and bridge regions, and a clathrate-like low density region in the axial region. Translational diffusion coefficient, hydration enthalpy, power spectra of the main vibrational modes, and the EXAFS spectrum simulated from molecular dynamics trajectories agree fairly well with the experiment.Junta de Andalucía de España, Proyecto de Excelencia-P11-FQM 760

    A general study of actinyl hydration by molecular dynamics simulations using ab initio force fields

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    A set of new ab initio force fields for aqueous [AnO2] 2+/+ (An = Np(VI,V), Pu(VI), Am(VI)) has been developed using the Hydrated Ion (HI) model methodology previously used for [UO2] 2+. Except for the non-electrostatic contribution of the HI-bulk water interaction, the interaction potentials are individually parameterized. Translational diffusion coefficients, hydration enthalpies, and vibrational normal mode frequencies were calculated from the MD simulations. Physico-chemical properties satisfactorily agree with experiments validating the robustness of the force field strategy. The solvation dynamics and structure for all hexavalent actinoids are extremely similar and resemble our previous analysis of the uranyl cation. This supports the idea of using the uranyl cation as a reference for the study of other minor actinyls. The comparison between the NpO2+ 2 and NpO+ 2 hydration only provides significant differences in first and second shell distances and second-shell mean residence times. We propose a single general view of the [AnO2] 2+/+ hydration structure: aqueous actinyls are amphiphilic anisotropic solutes which are equatorially conventional spherically symmetric cations capped at the poles by clathrate-like water structures.Junta de Andalucía de España, Plan Andaluz de Investigación-FQM-28

    Case Study: Body Composition Changes Resulting from a Nutritional Intervention on a Professional Vegan Powerlifter

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    Powerlifting is a weight-class strength sport where achieving low fat mass (FM) and high fat-free mass (FFM) is desirable to improve performance. Recent studies have evaluated the nutritional considerations of different eating patterns, such as vegan diets (VD), in athlete populations. VD are a challenge for athletes who want to attain body composition changes. The aim of this case study is to report on the body composition changes and subjective feelings of a male professional vegan powerlifter following VD for six weeks. The body mass of the powerlifter decreased from 79.3 to 77.4 kg (2.39%). Along with this, FM decreased from 15.0 to 11.4 kg (24%). Conversely, FFM increased from 64.3 to 66.0 kg (2.64%). Moreover, the powerlifter communicated no subjective feelings of low energy availability during training sessions. The VD might compromise adherence in a nutritional intervention which aims to improve body composition due to the nutritional requirements for fat loss. Therefore, more appropriate health assessments, including blood and psychological tests, are required for professional athletes. This short-term VD intervention was satisfactory for improving body composition and no adverse outcomes were reported

    Relative Age Effect on Motor Competence in Children Aged 4–5 Years

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    The purpose of this study was to evaluate whether a Relative Age Effect (RAE) exists in motor competence of preschool children. The hypothesis was that motor competence, assessed by the Movement Assessment Battery for Children-2 (MABC-2), would be higher in preschool children born in the first quarter of the year compared to those who were born in the last quarter of the same year. A total of 360 preschool children were evaluated of whom 208 (57.8%) were boys and 152 (42.8%) were girls, with a mean age of 4.52 years old (± 0.50). The distribution of the participants was 172 children aged 4 years old and 188 aged 5 years old. The data showed a main effect on the age factor in the total score of aiming and catching (p < 0.001) and in the total test score (p < 0.001), in the quarter of birth factor in all the dimensions studied (i.e., total score of manual dexterity (p < 0.001); total score of aiming and catching (p = 0.001); total score of balance (p < 0.001); total test score (p < 0.001)) and in the interaction between both factors (i.e., total score of manual dexterity (p = 0.005); total score of aiming and catching (p = 0.002); total score of balance (p < 0.001); total test score (p < 0.001)). Age and quarter of birth produce a RAE in 4 and 5-year-old preschool children’s motor competenceS

    Disruptive behaviours in Physical Education classes: A descriptive research in compulsory education

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    The aim of this research was determining disruptive behaviours of Primary and Secondary Schoolchildren in physical education classes according to educational stage, age and gender. The sample consisted of a total of 1304 students from 10 to 16 years old (M = 12.77; SD = 1.89), of whom 548 were Primary Education and 756 of Secondary Education; 612 were boys (46.9%) and 692 were girls (53.1%). The data collection was conducted through to the appropriate conduct scale in physical education and sport (CCDEF). The results obtained showed significant statistical differences in the age factor on Aggressiveness (AGR) (p < .001), Irresponsibility (IRRP) (p < .001), Fails to follow directions (FFD) (p < .001), Distracts or disturbs others (DDO) (p < .001) and Poor self-management (PSM) (p < .001). Regarding gender, there were statistically significant differences between boys and girls in FFD and on PSM (p < .001). Also, significant statistical differences were found on stage factor on AGR (p < .001), IRRP (p < .001), FFD (p < .001), DDO (p < .001) and PSM (p < .001). Disruptive behaviours scores increase with age and are higher in Compulsory Secondary Education than in Primary education schoolchildren. Boys in Primary Education scores higher than girls in all dimensions studied, while boys in Compulsory Secondary Education do so on aggressiveness

    The structural and electronic properties of nanostructured Ce1–x–yZrxTbyO2 ternary oxides: Unusual concentration of Tb3+ and metal_oxygen_metal interactions

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    10 pages, 12 figures, 1 table.Ceria-based ternary oxides are widely used in many areas of chemistry, physics, and materials science. Synchrotron-based time-resolved x-ray diffraction, x-ray absorption near-edge spectroscopy (XANES), Raman spectroscopy, and density-functional calculations were used to study the structural and electronic properties of Ce–Zr–Tb oxide nanoparticles. The nanoparticles were synthesized following a novel microemulsion method and had sizes in the range of 4–7 nm. The Ce1–x–yZrxTbyO2 ternary systems exhibit a complex behavior that cannot be predicted as a simple extrapolation of the properties of Ce1–xZrxO2, Ce1–xTbxO2, or the individual oxides (CeO2, ZrO2, and TbO2). The doping of ceria with Zr and Tb induces a decrease in the unit cell, but there are large positive deviations with respect to the cell parameters predicted by Vegard's rule for ideal solid solutions. The presence of Zr and Tb generates strain in the ceria lattice through the creation of crystal imperfections and O vacancies. The O K-edge and Tb LIII-edge XANES spectra for the Ce1–x–yZrxTbyO2 nanoparticles point to the existence of distinctive electronic properties. In Ce1–x–yZrxTbyO2 there is an unexpected high concentration of Tb3+, which is not seen in TbO2 or Ce1–xTbxO2 and enhances the chemical reactivity of the ternary oxide. Tb_O_Zr interactions produce a stabilization of the Tb(4f,5d) states that is responsible for the high concentration of Tb3+ cations. The behavior of Ce1–x–yZrxTbyO2 illustrates how important can be metal_oxygen_metal interactions for determining the structural, electronic, and chemical properties of a ternary oxide.The research carried out at the Chemistry Department of Brookhaven National Laboratory was financed through Contract No. DE-AC02-98CH10886 with the US Department of Energy (Division of Chemical Sciences). The NSLS is supported by the Divisions of Materials and Chemical Sciences of DOE. Work at the “Instituto de Catálisis y Petroleoquímica (CSIC)” was done with financial support from CICYT (Project No. MAT2000-1467).Peer reviewe

    Nitrogen, phosphorus, potassium, calcium and magnesium releasefrom two compressed fertilizers: column experiments

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    The objective of this work was to study nutrients release from two compressed nitrogen–potassium–phosphorous (NPK) fertilizers. In the Lourizán Forest Center, tablet-type controlled-release fertilizers (CRF) were prepared by compressing various mixtures of fertilizers without covers or binders. We used soil columns (50 cm long and 7.3 cm inner diameter) that were filled with soil from the surface layer (0–20 cm) of an A horizon corresponding to a Cambic Umbrisol. Tablets of two slow-release NPK fertilizers (11–18–11 or 8–8–16) were placed into the soil (within the first 3 cm), and then water was percolated through the columns in a saturated regime for 80 days. Percolates were analyzed for N, P, K+, Ca2+ and Mg2+. These elements were also determined in soil and fertilizer tablets at the end of the trials. Nutrient concentrations were high in the first leachates and reached a steady state when 1426 mm of water had been percolated, which is equivalent to approximately 1.5 years of rainfall in this geographic area. In the whole trial, both tablets lost more than 80% of their initial N, P and K contents. However, K+, Ca2+ and Mg2+ were the most leached, whereas N and P were lost in leachates to a lesser extent. Nutrient release was slower from the tablet with a composition of 8–8–16 than from the 11–18–11 fertilizer. In view of that, the 8–8–16 tablet can be considered more adequate for crops with a nutrient demand sustained over time. At the end of the trial, the effects of these fertilizers on soil chemical parameters were still evident, with a significant increase of pH, available Ca2+, Mg2+, K+, P and effective cation exchange capacity (eCEC) in the fertilized columns, as well as a significant decrease in exchangeable Al3+, reaching values < 0.08 cmol (+) kg−1.S

    Hydration of Heavy Alkaline-Earth Cations Studied by Molecular Dynamics Simulations and X-ray Absorption Spectroscopy

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    The physicochemical properties of the three heaviest alkaline-earth cations, Sr2+, Ba2+, and Ra2+ in water have been studied by means of classical molecular dynamics (MD) simulations. A specific set of cation-water intermolecular potentials based on ab initio potential energy surfaces has been built on the basis of the hydrated ion concept. The polarizable and flexible model of water MCDHO2 was adopted. The theoretical-experimental comparison of structural, dynamical, energetic, and spectroscopical properties of Sr2+ and Ba2+ aqueous solutions is satisfactory, which supports the methodology developed. This good behavior allows a reasonable reliability for the predicted Ra2+ physicochemical data not experimentally determined yet. Simulated extended X-ray absorption fine-structure (EXAFS) and X-ray absorption near-edge spectroscopy spectra have been computed from the snapshots of the MD simulations and compared with the experimental information available for Sr2+ and Ba2+. For the Ra2+ case, the Ra L3-edge EXAFS spectrum is proposed. Structural and dynamical properties of the aqua ions for the three cations have been obtained and analyzed. Along the [M(H2O)n]m+ series, the M-O distance for the first-hydration shell is 2.57, 2.81, and 2.93 Å for Sr2+, Ba2+, and Ra2+, respectively. The hydration number also increases when one is going down along the group: 8.1, 9.4, and 9.8 for Sr2+, Ba2+, and Ra2+, respectively. Whereas [Sr(H2O)8]2+ is a typical aqua ion with a well-defined structure, the Ba2+ and Ra2+ hydration provides a picture exhibiting an average between the ennea- and the deca-hydration. These results show a similar chemical behavior of Ba2+ and Ra2+ aqueous solutions and support experimental studies on the removal of Ra-226 of aquifers by different techniques, where Ra2+ is replaced by Ba2+. A comparison of the heavy alkaline ions, Rb+ and Cs+, with the heavy alkaline-earth ions is made.Universidad de Sevilla US-126447

    Molecular-dynamics-based investigation of scattering path contributions to the EXAFS spectrum: The Cr3¿ aqueous solution case

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    Extended x-ray absorption fine structure spectra were computed based on molecular-dynamics (MD) struc- tural data of a [ Cr(H2O)6 ]3+ aqueous solution using nonempirical cation-water potentials. An excellent re- production of the experimental spectrum was achieved. A simple estimation of Debye-Waller factors of the multiple-scattering paths is deduced from MD simulations. The influence of the single-scattering path due to the second hydration shell as compared with the multiple-scattering paths within the first hydration shell allows a reasonable determination of the second hydration shell distance R(Cr-OII) within 0.1 Å
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