El consumo de probiótico Lactobacillus plantarum CECT 7315/7316 mejora el estado de salud general en personas de edad avanzada

Fundamentos: Con la edad avanzada se producen cambios en la microflora intestinal que pueden afectar al estado de salud general. En este trabajo analizamos el efecto de Lactobacillus plantarum CECT 7315/7316 sobre la regulación del tránsito intestinal y el estado nutricional. Métodos: Hemos realizado un estudio clínico dobleciego, controlado por placebo y aleatorizado. Hemos evaluado la evolución de la frecuencia de defecación semanal y los niveles en sangre de proteínas totales, albúmina,colesterol y proteína C-reactiva. Resultados: Lactobacillus plantarum CECT 7315/7316 ayuda a regular el tránsito intestinal y mejora el estado nutricional en personas mayores. Conclusiones: El consumo de productos funcionales que contengan L. plantarum CECT 7315/7316 mejora la calidad de vida de personas de la tercera edad

Dense Packings of Random Binary Assemblies of Disks

The most dense random packings of binary assemblies of hard disks in the plane are considered for the case of disks with a small difference in their radii. An expression for the dependence of the packing density on the relative difference in disk sizes, disk concentration, and mean value of the gaps is derived. The computer simulation of the random dense packing is carried out using various algorithms and theoretical results are confirmed. The gap distribution is shown to be of the exponential type for very dense random packings

Plastic deformation of glassy polymethylene : computer-aided molecular-dynamic simulation

Molecular-dynamic simulation of low-temperature plastic deformation (T def = 50 K, T def/T g = 0.3) is studied for glassy polymethylene under the regime of active uniaxial compression and tension for a cell composed of 64 chains containing 100 -CH2 groups in each (as united atoms) and with periodic boundary conditions. Thirty-two such cells are created, and, in each cell, polymethylene chains in the statistical coil conformation are independently constructed. The cells are subjected to isothermal uniaxial compression at T def = 50 K by ¿ = 30% and by ¿ = 70% under uniaxial tension. In the course of loading, a s-¿ diagram is recorded, while the mechanical work spent on deformation, the changes in the overall potential energy of the system, and the contributions from various potential interactions (noncovalent van der Waals bonds, chemical links, valence and torsional angles) are estimated. The results are averaged over all 32 cells. The relaxation of stored potential energy and residual strain after complete unloading of the deformed sample is studied. The relaxation of stored energy and residual strain is shown to be incomplete. Most of this energy and strain is stored in the sample at the deformation temperature for long period. The conformational composition of chains and the average density of polymer glass during loading are analyzed. Simulation results show that inelastic deformations commence not with the conformational unfolding of coils but with the nucleation of strain-bearing defects of a nonconformational nature. The main contribution to the energy of these defects is provided by van der Waals interactions. Strain-bearing defects are nucleated in a polymer glass during tension and compression primarily as short-scale positive volume fluctuations in the sample. During tension, the average density of the glass decreases; during compression, this parameter slightly increases to ¿ ˜ 8% and then decreases. An initial increase in the density indicates that, during compression and at ¿ <8%, coils undergo compactization via an increase in chain packing. During compression, the concentration of trans conformers remains unchanged below ¿ ˜ 8% and then decreases. During compression, it means that in a glass, coils do not increase their sizes at strains below ¿ ˜ 8%. During tensile drawing, coils remain unfolded below ¿ ˜ 35%; at higher strains, coils become enriched with trans conformers or unfold. At this stage, the concentration of trans conformers linearly increases. The development of a strain-induced excess volume (strain-bearing defects) entails an increase in the potential energy of the sample. Under the given conditions of deformation, nucleation of strain-bearing defects and an increase in their concentration are found to be the only processes occurring at the initial stage of loading of glassy polymethylene. The results of computer-aided simulation are compared with the experimental data reported in the literature

Patterns of vortex generation behind a cylinder in a wall-bounded cross-flow during transition to turbulence

© Published under licence by IOP Publishing Ltd. The paper elaborates on experimental investigation and direct numerical simulation of the wake flow behind a circular cylinder located near the wall of a rectangular channel. The study considers the Reynolds number range that covers transition to turbulence in the wake. Spiral fluid motion directed from the sidewalls to the channel center is revealed behind the cylinder for both positions of the cylinder considered in the study. The paper describes the effect of this motion on the critical Reynolds number corresponding to the onset of Karman vortex street and on the vortex topology. The spiral motion is shown to correlate with the onset of low-pressure regions behind the cylinder near the sidewalls. These regions result from the interaction between the boundary layer on the sidewalls and the separation region behind the cylinder

Study of acelerated agening under concentrated solar radiation of silicon oxycarbide glases as high temperature solar receivers

Solar energy and especially concentrated solar power systems (CSP) need materials that can tolerate the demanding working conditions. In this sense, the receivers are exposed to large fluxes of solar radiation&nbsp; that produce very high temperatures. In addition, due to the operational conditions of receivers large temperature variations occur during day and night, or on cloudy days being these the main aging factors. However, other factors such as humidity, salines environments or pollutans in industrial zones can not be ruled out. Silicon oxycarbide glasses (SiOC) are composite materials formed by a SiOC glass phase (matrix phase) and a C phase (reinforcing phase) homogeneously dispersed and they can be very promising candidates for this type of applications due to their excellent intrinsic properties like their high resistante against to both oxidation and very aggressive environments, good mechanical properties, etc. In this work we have focused in the evaluation of the composite materials (SiOC porous and dense) against thermal shock produced by Frenel lens that concentrated solar radiation more than 2600 times. In every cycle materials they have been heated (32 &ordm;C s-1) an cooled (27 &ordm;C s-1) at very high rates from room temperature to 1000 &ordm;C. This process has been repeated 100 times or lesser in the case of catastrophic material damage. The evolution of material surface during thermal shock cycles has been followed by several techniques such confocal and electronic microscopies and Raman, Infrarred and UV-Visible spectroscopies. Porous silicon oxycarbide materials experiencied a rapid and severe degradation during the first cycles but dense one tolerates quite well the exposure againts concentrated solar radiation

Estudio del envejecimiento acelerado bajo radiación solar concentrada de vidrios de oxicarburo como receptores de alta temperatura

La energía solar y en especial los sistemas de energía solar concentrada (ESC) necesita materiales que puedan soportar sus exigentes condiciones de trabajo. En este sentido los receptores están sometidos a grandes flujos de radiación solar que dan lugar a elevadas temperaturas. Además, debido a la propias condiciones ambientales los sistemas de ESC se encuentran sometidos a grandes fluctuaciones de temperatura durante el día o la noche o en condiciones meteorológicas adversas, siendo éstos los principales factores de envejecimiento, sin que puedan quedar excluidos otros efectos como la humedad ambiental, atmósferas salinas u otros agentes contaminantes de zonas industriales. Los vidrios de oxicarburo (SiOC) son materiales compuestos formados por una fase de SiOC (matriz) y otra de C (refuerzo) homogéneamente dispersa, por lo que se considera que pueden ser unos candidatos idóneos como receptores solares, debido a sus buenas propiedades intrínsecas, tales como su elevada resistencia frente a la oxidación y a ambientes agresivos a elevadas temperaturas, buenas propiedades mecánicas, etc. En este trabajo nos hemos centrado en la evaluación de la resistencia de los composites (SiOC porosos y densos) frente al choque térmico producido en una lente Fresnel que concentra la radiación solar más de 2600 veces. Para ello el material estudiado se ha sometido a 100 ciclos de calentamiento (velocidad: 32 ºC s-1) desde temperatura ambiente hasta 1000 ºC durante 10 min, seguidos de un enfriamiento rápido (velocidad: 27 ºC s-1). La evolución de la superficie del material se ha llevado a cabo mediante microscopia confocal y microscopia electrónica de barrido, así como con espectroscopia infrarroja, Raman y UV-Vis. Los materiales porosos sufren una degradación severa desde los primeros ciclos de tratamiento, mientras que los materiales densos permanecen prácticamente inalterados tras los ciclos de choque térmico ensayados.Los autores agradecen al Dr. J.I. Robla Villalba por su ayuda con los sistemas de medida de la temperatura. Este trabajo ha sido financiado por los proyectos ENE2012-39385-CO3-01 (Investigación en Materiales y Diseños Innovadores para Receptores Avanzados Solares (MIRASOL) del Ministerio de Economía Industria y Competitividad de España y por el proyecto MAT2016-78700-R financiado por la Agencia Española de Investigación y los Fondos Europeos de Desarrollo Regional (Nuevos supercondensadores híbridos basados enelectrodos de Nanocomposites de carbono/grafeno deirivados de oxicarburos

Silicon oxycarbide and silicon oxycarbonitride materials under concentrated solar radiation

The potential application of silicon oxycarbonitride (SiOCN), silicon oxycarbide (SiOC) and silicon oxycarbide¿SiC (SiOC¿SiC) for photothermal devices such as volumetric solar absorbers has been studied evaluating the response to thermal shock from a Fresnel lens. The accelerated ageing test comprises fast heating (32¿C min¿1 ) and cooling rates (27¿C min¿1 ) from 100 to 1000¿C and dwelling times of 10 min. Porous materials (SiOCNp and SiOCp) failed the thermal shock tests; they were massively degraded by the formation of a large depression in the focus of solar radiation. Dense materials (SiOCd and SiOC¿SiCd) withstood 100 cycles of thermal shock ageing tests due to the formation of a protective silica layer. The absorptance values for dense materials remained fairly constant before and after thermal shock tests: from 94.5 to 94.3% for SiOCd and from 93.3 to 93.3% for SiOC¿SiCd . These preliminary studies indicate their potential for high-temperature solar receiver applications.This research was funded by MINISTERIO DE ECONOMÍA, INDUSTRIA Y COMPETITIVIDAD OF SPAIN, [ENE2012-39385-CO3-01] and SPANISH RESEARCH AGENGY AND THE EUROPEAN REGIONAL DEVELOPMENT FUND (AEI/FEDER, UE), [MAT2016-78700-R].We acknowledge support of the publication fee by the Spanish National Research Council (CSIC) Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)

Tornado-like vortices behind a cylinder in a channel at moderate Reynolds numbers

© Published under licence by IOP Publishing Ltd. Experiments and direct numerical simulation were employed to study the near wake of a circular cylinder in a cross flow in a rectangular channel. The gap between the cylinder and the channel wall was varied. Moderate Reynolds numbers were considered. The analysis of experimental results in combination with numerical simulation revealed the common patterns in the vortical structure of flow behind the cylinder, namely the tornado-like vortices formed in the region where the cylinder was attached to the sidewalls of the channel. The effect of the cylinder location on the onset of Karman vortex street was estimated. The formation mechanism of tornado-like vortices was described

El consumo de probiótico Lactobacillus plantarum CECT 7315/7316 mejora el estado de salud general en personas de edad avanzada

Fundamentos: Con la edad avanzada se producen cambios en la microflora intestinal que pueden afectar al estado de salud general. En este trabajo analizamos el efecto de Lactobacillus plantarum CECT 7315/7316 sobre la regulación del tránsito intestinal y el estado nutricional. Métodos: Hemos realizado un estudio clínico dobleciego, controlado por placebo y aleatorizado. Hemos evaluado la evolución de la frecuencia de defecación semanal y los niveles en sangre de proteínas totales, albúmina,colesterol y proteína C-reactiva. Resultados: Lactobacillus plantarum CECT 7315/7316 ayuda a regular el tránsito intestinal y mejora el estado nutricional en personas mayores. Conclusiones: El consumo de productos funcionales que contengan L. plantarum CECT 7315/7316 mejora la calidad de vida de personas de la tercera edad