1,440 research outputs found
El Derecho canĂłnico como derecho estatutario en el Ordenamiento jurĂdico español.
Material incluido en el volumen especial de la revista del Instituto MartĂn de Azpilcueta, Universidad de Navarra : Ius Canonicum (1999), en honor de Javier Hervada
AnĂĄlisis del pedaleo ciclista con sistemas convencionales VS no circulares en pruebas submĂĄximas y supramĂĄximas
El objetivo de este trabajo ha sido analizar y comparar el rendimiento mecånico måximo (pruebas supramåximas) y la eficiencia energética (pruebas submåximas) desarrollada por ciclistas profesionales con un sistema de pedaleo convencional (C) y con un sistema de pedaleo no circular (Sistema RotorŸ o SR); asà como valorar sus efectos en la cinemåtica del pedaleo. 15 ciclistas profesionales realizaron varias pruebas submåximas y supramåximas, con un sistema C y con 4 variantes del SR. Los datos de eficiencia energética obtenidos en el estudio fueron similares a los descritos en otros trabajos, sin diferencias entre C y SR, aunque sà se alteró la cinemåtica del pedaleo del tobillo y la rodilla. Las variables de rendimiento mecånico måximo fueron mayores con SR, lo que parece indicar que estos sistemas pudieran incrementar el rendimiento en las modalidades de Ciclismo en Pista.Peer Reviewe
Solving shallow-water systems in 2D domains using Finite Volume methods and multimedia SSE instructions
AbstractThe goal of this paper is to construct efficient parallel solvers for 2D hyperbolic systems of conservation laws with source terms and nonconservative products. The method of lines is applied: at every intercell a projected Riemann problem along the normal direction is considered which is discretized by means of well-balanced Roe methods. The resulting 2D numerical scheme is explicit and first-order accurate. In [M.J. Castro, J.A. GarcĂa, J.M. GonzĂĄlez, C. Pares, A parallel 2D Finite Volume scheme for solving systems of balance laws with nonconservative products: Application to shallow flows, Comput. Methods Appl. Mech. Engrg. 196 (2006) 2788â2815] a domain decomposition method was used to parallelize the resulting numerical scheme, which was implemented in a PC cluster by means of MPI techniques.In this paper, in order to optimize the computations, a new parallelization of SIMD type is performed at each MPI thread, by means of SSE (âStreaming SIMD Extensionsâ), which are present in common processors. More specifically, as the most costly part of the calculations performed at each processor consists of a huge number of small matrix and vector computations, we use the Intel© Integrated Performance Primitives small matrix library. To make easy the use of this library, which is implemented using assembler and SSE instructions, we have developed a C++ wrapper of this library in an efficient way. Some numerical tests were carried out to validate the performance of the C++ small matrix wrapper. The specific application of the scheme to one-layer Shallow-Water systems has been implemented on a PCâs cluster. The correct behavior of the one-layer model is assessed using laboratory data
New inequalities involving the geometric-arithmetic index
Let G = (V, E) be a simple connected graph and di be the degree of its ith
vertex. In a recent paper [J. Math. Chem. 46 (2009) 1369-1376] the first geometricarithmetic index of a graph G was defined as
GA1 = X
uvâE
2
â
dudv
du + dv
.
This graph invariant is useful for chemical proposes. The main use of GA1 is for designing so-called quantitative structure-activity relations and quantitative structureproperty relations. In this paper we obtain new inequalities involving the geometricarithmetic index GA1 and characterize the graphs which make the inequalities tight.
In particular, we improve some known results, generalize other, and we relate GA1
to other well-known topological indices.We are grateful to the constructive comments from anonymous referee on our pape. The first and third authors are supported by the "Ministerio de EconomĂa y Competititvidad" (MTM2013-46374-P and MTM2015-69323-REDT), Spain, and by the CONACYT (FOMIX-CONACyT-UAGro 249818), Mexico
Magnetic order and magnetic properties of the oxygen deficient SmBaMn2O5 layered perovskite
Magnetism in SmBaMn2O5 was investigated on a single crystal by magnetic and neutron diffraction measurements. This is an oxygen deficient perovskite with a layered ordering of Sm and Ba cations. Mn atoms are coordinated with five oxygens forming a square pyramid and they are ordered in a checkerboard pattern of expanded-compressed pyramids in the ab-plane. The neutron diffraction study revealed a ferrimagnetic ordering of Mn moments below TN=134 K. Macroscopic measurements reveal a very anisotropic behavior. Measurements with the external magnetic field parallel (M||c) and perpendicular (MÂżc) to the c-axis confirm that this is the easy axis above 10 K. Below this temperature, the Sm sublattice begins to polarize and the magnetization M||c decreases while MÂżc experiences a huge increase. This indicates that Sm moments begin to order around 10 K in the ab-plane with a minor component on the c-axis that opposes the overall magnetization from Mn sublattices
Magnetic order and magnetoelectric properties of R2CoMn O6 perovskites (R=Ho, Tm, Yb, and Lu)
We present a detailed study on the magnetic structure and magnetoelectric properties of several double perovskites R2CoMnO6 (R=Ho, Tm, Yb, and Lu). All of these samples show an almost perfect (~94%) ordering of Co2+ and Mn4+ cations in the unit cell. Our research reveals that the magnetic ground state strongly depends on the R size. For samples with larger R (Ho and Tm), the ground state is formed by a ferromagnetic order (F type) of Co2+ and Mn4+ moments, while R either remains mainly disordered (Ho) or is coupled antiferromagnetically (Tm) to the Co/Mn sublattice. For samples with smaller R (Yb or Lu), competitive interactions lead to the formation of an E-type arrangement for the Co2+ and Mn4+ moments with a large amount of extended defects such as stacking faults. The Yb3+ is partly ordered at very low temperature. The latter samples undergo a metamagnetic transition from the E into the F type, which is coupled to a negative magnetodielectric effect. Actually, the real part of dielectric permittivity shows an anomaly at the magnetic transition for the samples exhibiting an E-type order. This anomaly is absent in samples with F-type order, and, accordingly, it vanishes coupled to the metamagnetic transition for R=Yb or Lu samples. At room temperature, the huge values of the dielectric constant reveal the presence of Maxwell-Wagner depletion layers. Pyroelectric measurements reveal a high polarization at low temperature, but the onset of pyroelectric current is neither correlated to the kind of magnetic ordering nor to the magnetic transition. Our study identified the pyroelectric current as thermally stimulated depolarization current and electric-field polarization curves show a linear behavior at low temperature. Therefore, no clear ferroelectric transition occurs in these compounds
Influencia de los parĂĄmetros biomecĂĄnicos en el rendimiento y la economĂa de corredores de fondo aficionados
Los objetivos de este estudio son analizar la relaciĂłn entre las variables biomecĂĄnicas, la economĂa de carrera y el rendimiento en corredores de fondo aficionados. AdemĂĄs, determinar si existe algĂșn cambio en los parĂĄmetros biomecĂĄnicos coincidente con el umbral anaerĂłbico ventilatorio. Participaron 10 corredores de fondo aficionados realizando: AntropometrĂa, baterĂa de saltos verticales, prueba de economĂa de carrera y prueba de consumo mĂĄximo de oxĂgeno. Estas Ășltimas realizadas en tapiz rodante, registrĂĄndose parĂĄmetros fisiolĂłgicos (ventilatorios y frecuencia cardiaca) y biomecĂĄnicos (tiempos de contacto y de vuelo, frecuencia y amplitud de zancada, âduty factorâ). Por primera vez, se ha observado una relaciĂłn entre parĂĄmetros biomecĂĄnicos espacio-temporales de la carrera (frecuencia y amplitud de zancada), el rendimiento y la economĂa de carrera. AdemĂĄs, se ha comprobado que la apariciĂłn del umbral anaerĂłbico ventilatorio se encuentra relacionada con cambios en la biomecĂĄnica de la carrera (fundamentalmente âduty factorâ y amplitud de zancada). Las relaciones encontradas entre las variables antropomĂ©tricas y de salto, economĂa de carrera y rendimiento estĂĄn en consonancia con las mencionadas en estudios previos, asĂ como que la relaciĂłn entre la economĂa de carrera y el rendimiento. Futuros trabajos deberĂan realizarse en corredores de mayor nivel para contrastar estos hallazgos.The aim of this study is to analyze the relationship between running biomechanics, running economy and performance in recreational long distance runners. Additionally, determine if there is any change in running biomechanical parameters that coincides with the anaerobic threshold. Ten recreational runners performed an anthropometric evaluation, a battery of vertical jumps, a running economy test and a maximal incremental test. Both running tests were performed in a treadmill, registering simultaneously physiological (ventilation and heart rate) and biomechanical (contact and flight times, stride length and rate, âduty factorâ) parameters. A relationship between running biomechanics (step length and rate), running economy and performance was obtained. Furthermore, the appearance of the ventilatory anaerobic threshold was related with changes in running biomechanics (mainly with âduty factorâ and step length). The relationships between anthropometry and vertical jumpsâ parameters, running economy and performance still consistent with those identified in previous studies, as well as the relationship between running economy and performance. Future studies should be done with a higher level sample to contrast these findings.Peer Reviewe
Comparison of greenhouse gas emissions from Mexican intensive dairy farms
The objectives of this study were to compare estimates of greenhouse gas emissions (GHG) as CH4 (enteric-manure), N2O (manure), and CO2 (fuel and energy use), the use of water and soil, the excretion of nutrients in manure, and feed efficiency from Mexican intensive dairy farms. Data from 26 dairy farms were analysed with a multivariable cluster analysis. Three grades of intensifications were identified (low, medium and high). Mathematical models were used to estimate GHG. Feed efficiency (kg milk per kg DMI) was better in high intensive production systems. Enteric methane was identified as the major source of GHG in all types of systems. High intensive dairies generated the lowest emissions of CH4, N2O and CO2 equivalent by unit of product, 18.6 g, 0.12 g and 828 g, respectively. Water footprint was lower in low intensive dairies using 427 L of water/L of milk. Cropland was highest in intensive systems but milk yield per area was better (30,938 kg/ha). Excretions of N, P, and K were lower in intensive dairies per kg of milk, at 13.2, 2.4, and 6.4 g, respectively. As intensification in the dairy system increased feed efficiency (kg milk/kg DMI) was better. Per unit of product (kg of milk), dairies with the highest intensification generated the lowest GHG emissions, nutrient excretion values and land and water use as compared to dairies with medium and low intensification. Increasing intensification and therefore feed efficiency of Mexican dairy systems could help to decrease GHG emissions, natural resources use and nutrient excretion.Keywords: Carbon footprint, environmental impact, methane, milk productio
Structural, Magnetic, and Electronic Properties of CaBaCo4- xMxO7 (M = Fe, Zn)
The effect of substituting iron and zinc for cobalt in CaBaCo4O7 was investigated using neutron diffraction and X-ray absorption spectroscopy techniques. The orthorhombic distortion present in the parent compound CaBaCo4O7 decreases with increasing the content of either Fe or Zn. The samples CaBaCo3ZnO7 and CaBaCo4-xFexO7 with x = 1.5 are metrically hexagonal, but much better refinements in the neutron diffraction patterns are obtained using an orthorhombic unit cell. The two types of substitution have opposite effects on the structural and magnetic properties. Fe atoms preferentially occupy the sites at the triangular layer. Thus, the replacement of Co by Fe suppresses the ferrimagnetic ordering of the parent compound, and CaBaCo4-xFexO7 (0.5 = x = 2) samples are antiferromagnetically ordered following a new propagation vector k = (1/3, 0, 0). However, the Zn atoms prefer occupying the Kagome layer, which is very detrimental for the long-range magnetic interactions giving rise to a magnetic glass-like behavior in the CaBaCo3ZnO7 sample. The oxidation states of iron and zinc are found to be 3+ and 2+, respectively, independently of the content, as confirmed by X-ray absorption spectroscopy. Therefore, the average Co oxidation state changes accordingly with the Fe3+ or Zn2+ doping. Also, X-ray absorption spectroscopy data confirm the different preferential occupation for both Fe and Zn cations. The combined information obtained by neutron diffraction and X-ray absorption spectroscopy indicates that cobalt atoms can be either in a fluctuating Co2+/Co3+ valence state or, alternatively, Co2+ and Co3+ ions being randomly distributed in the lattice. These results explain the occurrence of local disorder in the CoO4 tetrahedra obtained by EXAFS. An anomaly in the lattice parameters and an increase in the local disorder are observed only at the ferrimagnetic transition for CaBaCo4O7, revealing the occurrence of local magneto-elastic coupling
Magnetoelectric and structural properties of Y2CoMn O6: The role of antisite defects
We have carried out an investigation on the magnetoelectric properties of the presumed multiferroic Y2CoMnO6 with different degrees of Co/Mn atomic ordering. The magnetic ground state was studied by neutron diffraction, showing a collinear ferromagnetic (FM) ordering of Co and Mn moments with a small antiferromagnetic canting. No superstructure peaks from an E-type magnetic structure were detected in our measurements. Magnetic measurements reveal FM transitions with pinned magnetic domains. The degree of Co/Mn ordering affects the Curie temperature only a little, but has strong effects on the magnetic hysteresis loops, and the FM moment signal at high field increases with increasing such order. The loops display steps at critical fields whose number and extent depends on each specimen. The most ordered sample exhibits the greatest steps ascribed to the alignment of magnetic domains separated by antiphase boundaries. All samples are insulators exhibiting low dielectric loss and dielectric constants at low temperature. On warming, they show a step increase in the real dielectric permittivity accompanied by peaks in the dielectric loss typical of thermally activated hopping processes. At room temperature, the huge values of the dielectric constant reveal the presence of Maxwell-Wagner depletion layers. Pyroelectric measurements reveal a high polarization at low temperature for these compounds that increases with increasing the Co/Mn ordering. There is no correlation between the magnetic transition and the onset of pyroelectric current. No significant changes are observed in the pyroelectric effect measured under an external magnetic field, so magnetoelectric coupling is negligible. This paper identifies the pyroelectric current as thermally stimulated depolarization current ascribed to the reorientation of defect dipoles with activation energy of about 0.05 eV. Therefore, no ferroelectric transition occurs in these compounds, discarding the existence of intrinsic magnetoelectric multiferroicity
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