Energy partition and segregation for an intruder in a vibrated granular system under gravity

The difference of temperatures between an impurity and the surrounding gas in an open vibrated granular system is studied. It is shown that, in spite of the high inhomogeneity of the state, the temperature ratio remains constant in the bulk of the system. The lack of energy equipartition is associated to the change of sign of the pressure diffusion coefficient for the impurity at certain values of the parameters of the system, leading to a segregation criterium. The theoretical predictions are consistent with previous experimental results, and also in agreement with molecular dynamics simulation results reported in this paper.Comment: To appear in Phys. Rev. Let

Symmetry breaking and clustering in a vibrated granular gas with several macroscopically connected compartments

The spontaneous symmetry breaking in a vibro-fluidized low-density granular gas in three connected compartments is investigated. When the total number of particles in the system becomes large enough, particles distribute themselves unequally among the three compartments. Particles tend to concentrate in one of the compartments, the other two having the (relatively small) same average number of particles. A hydrodynamical model that accurately predicts the bifurcation diagram of the system is presented. The theory can be easily extended to the case of an arbitrary number of connected compartments

Hydrodynamic profiles for an impurity in a open vibrated granular gas

The hydrodynamic state of an impurity immersed in a low density granular gas is analyzed. Explicit expressions for the temperature and density fields of the impurity in terms of the hydrodynamic fields of the gas are derived. It is shown that the ratio between the temperatures of the two components, measuring the departure from energy equipartition, only depends on the mechanical properties of the particles, being therefore constant in the bulk of the system. This ratio plays an important role in determining the density profile of the intruder and its position with respect to the gas, since it determines the sign of the pressure diffusion coefficient. The theoretical predictions are compared with molecular dynamics simulation results for the particular case of the steady state of an open vibrated granular system in absence of macroscopic fluxes, and a satisfactory agreement is found

Influence of the Yesa reservoir on floods of the Aragón River, central Spanish Pyrenees

International audienceThe Yesa reservoir, the largest Pyrenean reservoir, was constructed in 1959 to supply water to new irrigated areas in the Ebro Depression, NE Spain. It is filled from October to May-June and then releases large quantities of water in the summer via the Bardenas Canal. The results confirm that the frequency of floods downstream of the dam decreased. The reduction mainly depends on two factors: i) the water storage level, and ii) the season of the year. Floods are very well controlled when the reservoir level is lower than 50%. Between 50 and 70%, only the highest floods are controlled. Finally, the reservoir retains mainly autumn and spring floods; most winter floods are released downstream to ensure the safety of the dam. Keywords: reservoir, flood control, flood seasonality, flood frequency, river regime, Pyrenees</p

Ac magnetic susceptibility of a molecular magnet submonolayer directly patterned onto a microSQUID sensor

We report the controlled integration, via Dip Pen Nanolithography, of monolayer dots of ferritin-based CoO nanoparticles (12 Bohr magnetons) into the most sensitive areas of a microSQUID sensor. The nearly optimum flux coupling between these nanomagnets and the microSQUID improves the achievable sensitivity by a factor 100, enabling us to measure the linear susceptibility of the molecular array down to very low temperatures (13 mK). This method opens the possibility of applying ac susceptibility experiments to characterize two-dimensional arrays of single molecule magnets within a wide range of temperatures and frequencies.Comment: 4 pages 3 figure

Steady state representation of the homogeneous cooling state of a granular gas

The properties of a dilute granular gas in the homogeneous cooling state are mapped to those of a stationary state by means of a change in the time scale that does not involve any internal property of the system. The new representation is closely related with a general property of the granular temperature in the long time limit. The physical and practical implications of the mapping are discussed. In particular, simulation results obtained by the direct simulation Monte Carlo method applied to the scaled dynamics are reported. This includes ensemble averages and also the velocity autocorrelation function, as well as the self-diffusion coefficient obtained from the latter by means of the Green-Kubo representation. In all cases, the obtained results are compared with theoretical predictions

Myopic maculopathy: Current status and proposal for a new classification and grading system (ATN)

Myopia is a highly frequent ocular disorder worldwide and pathologic myopia is the 4th most common cause of irreversible blindness in developed countries. Pathologic myopia is especially common in East Asian countries. Ocular alterations associated with pathologic myopia, especially those involving the macular area—defined as myopic maculopathy—are the leading causes of vision loss in patients with pathologic myopia. High myopia is defined as the presence of a highly negative refractive error (>−6 to −8 diopters) in the context of eye elongation (26–26.5 mm). Although the terms high myopia and pathologic myopia are often used interchangeably, they do not refer to the same eye disease. The two key factors driving the development of pathologic myopia are: 1) elongation of the axial length and 2) posterior staphyloma. The presence of posterior staphyloma, which is the most common finding in patients with pathologic myopia, is the key differentiating factor between high and pathologic myopia. The occurrence of staphyloma will, in most cases, eventually lead to other conditions such as atrophic, traction, or neovascular maculopathy. Posterior staphyloma is for instance, responsible for the differences between a myopic macular hole (MH)—with and without retinal detachment—and idiopathic MH. Posterior staphyloma typically induces retinal layer splitting, leading to foveoschisis in myopic MH, an important differentiating factor between myopic and emmetropic MH. Myopic maculopathy is a highly complex disease and current classification systems do not fully account for the numerous changes that occur in the macula of these patients. Therefore, a more comprehensive classification system is needed, for several important reasons. First, to more precisely define the disease stage to improve follow-up by enabling clinicians to more accurately monitor changes over time, which is essential given the progressive nature of this condition. Second, unification of the currently-available classification systems would establish standardized classification criteria that could be used to compare the findings from international multicentric studies. Finally, a more comprehensive classification system could help to improve our understanding of the genetic origins of this disease, which is clearly relevant given the interchangeable—but erroneous—use of the terms high and pathologic myopia in genetic researc

Construcción del conocimiento didáctico del contenido biológico en formación inicial de profesores

Presentamos la sistematización de los datos obtenidos a partir de los documentos que presentaron dos grupos de futuros profesores de Biología, a lo largo de un semestre, al diseñar Unidades Didácticas para la enseñanza de dos temáticas relacionadas con el auto-mantenimiento de los organismos. Analizamos los referentes de los docentes en formación acerca del Conocimiento Didáctico del Contenido Biológico (contemplamos 9 categorías de investigación) y los cambios de los mismos durante el proceso formativo en el que los estudiantes-profesores realizaron la propuesta

Síntesis y aplicación de nuevas nanopartículas de plata biocompatibles para el control del crecimiento de bacterias lácticas y acéticas en vinos

Este libro recoge el amplio y significativo elenco de estudios (microbiología) recientemente realizados por los grupos de investigación de la red GIENOL (Grupos de investigación enológica).-- et al.Es bien conocido que la plata tiene propiedades antimicrobianas muy potentes. Actualmente, la nanoplata es el nanomaterial más utilizado, representando aproximadamente la cuarta parte de todos los nanomateriales comercializados en el mercado. El presente trabajo tiene por objetivo explorar la potencial utilización de nuevas nanopartículas de plata como agentes antimicrobianos en enología, como una alternativa al empleo de los sulfitos. En primer lugar, se ha llevado a cabo la síntesis y caracterización de dos materiales de plata: PEG‐Ag NPs 1, nanopartículas sólidas soportadas sobre polietilenglicol, y GSH‐Ag NPs 2, nanopartículas en solución soportadas sobre glutatión. A continuación, se ha evaluado su actividad antimicrobiana frente a un total de 11 especies, que incluyen bacterias lácticas y bacterias acéticas. Se han establecido los parámetros de inhibición bacteriana, comprobándose que los nanomateriales con recubrimientos a base de ambos polímeros solubles (polietilenglicol y glutatión), son capaces de inhibir el crecimiento de ambos tipos de bacterias, y en concreto, el efecto inhibidor sobre las bacterias acéticas, fue superior al del metabisulfito potásico. También se ha estudiado el mecanismo de acción antimicrobiano de las nanopartículas de plata, en el que parece que están implicados cambios en la membrana plasmática de la célula bacteriana con pérdida de la viabilidad celular y de las funciones vitales de la célula.Los autores agradecen la financiación recibida del Ministerio de Economía y Competitividad (MINECO) a través de los proyectos PRI‐PIBAR‐2011‐1358 y AGL2012‐40172‐C02‐01.Peer Reviewe