1,388 research outputs found
Observing the evaporation transition in vibro-fluidized granular matter
By shaking a sand box the grains on the top start to jump giving the picture
of evaporating a sand bulk, and a gaseous transition starts at the surface
granular matter (GM) bed. Moreover the mixture of the grains in the whole bed
starts to move in a cooperative way which is far away from a Brownian
description. In a previous work we have shown that the key element to describe
the statistics of this behavior is the exclusion of volume principle, whereby
the system obeys a Fermi configurational approach. Even though the experiment
involves an archetypal non-equilibrium system, we succeeded in defining a
global temperature, as the quantity associated to the Lagrange parameter in a
maximum entropic statistical description. In fact in order to close our
approach we had to generalize the equipartition theorem for dissipative
systems. Therefore we postulated, found and measured a fundamental dissipative
parameter, written in terms of pumping and gravitational energies, linking the
configurational entropy to the collective response for the expansion of the
centre of mass (c.m.) of the granular bed. Here we present a kinetic approach
to describe the experimental velocity distribution function (VDF) of this
non-Maxwellian gas of macroscopic Fermi-like particles (mFp). The evaporation
transition occurs mainly by jumping balls governed by the excluded volume
principle. Surprisingly in the whole range of low temperatures that we measured
this description reveals a lattice-gas, leading to a packing factor, which is
independent of the external parameters. In addition we measure the mean free
path, as a function of the driving frequency, and corroborate our prediction
from the present kinetic theory.Comment: 6 pages, 4 figures, submitted for publication September 1st, 200
Biogas production from grape pomace: Thermodynamic model of the process and dynamic model of the power generation system
Recently, thermoelectric generators (TEGs) have emerged as a potential alternative for clean energy generation, due mainly to the technology innovation and the marked cost reduction of modules, as well as their distinctive advantages. In a TEG system, the electronic power conditioning system (PCS) plays a vital role in ensuring the effective power grid integration, since it is subject to requirements related not only to the variable thermal source itself but also to its effects on the grid operation. This paper proposes an enhanced structure of PCS for the grid integration of TEG arrays to maximize the energy capture from a variable heat source. The innovative topology employed consists of a Z-source inverter that allows the flexible, efficient and reliable generation of high quality electric power from the TEG array. A full detailed model is described and its control scheme is designed. The dynamic performance of the proposed systems is fully validated by computer simulation and experimental studies.Fil: Cáceres, Clara Ximena. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Cáceres, R. E.. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Hein, D.. Universitat Siegen; AlemaniaFil: Molina, Marcelo Gustavo. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Pia, J .M.. Universidad Nacional de San Juan. Facultad de Ingeniería; Argentin
Oferta de implantes de prótesis total de cadera en Cataluña
El crecimiento exponencial de la oferta de implantes de prótesis total de cadera
hace difícil para el cirujano ortopédico establecer criterios de elección, por este motivo hemos realizado
un análisis de la oferta actual de los mismos. Se han identificado 67 modelos de implantes
de prótesis total de cadera primaria y 19 modelos de revisión comercializados en la comunidad
catalana por 24 empresas. El número de variables, de material o diseño de los distintos modelos,
sin tener en cuenta las diversas medidas de vástagos, cuellos y cótilos, ha sido de 55. Hemos encontrado
referencias bibliográficas de resultados clínicos de un 25% de las prótesis. El rango de
coste de los implantes ha sido de 70.000 a 300.570 pesetas para las prótesis cementadas, con un
precio medio de 172.805 pesetas; de 375.654 a 648.606 pesetas para las no cementadas, con un
precio medio de 480.301 pesetas, y de 412.552 a 713.000 pesetas de las prótesis de revisión, con
una media de 568.138 pesetas. Esta dispersión de modelos y precios es mayor que la de otros países
de nuestro entorno, y el porcentaje de publicaciones de resultados clínicos encontrado es algo
menor que el reportado por algunos autores. Frente a esta situación creemos que serían necesarios
estudios clínicos a largo término y sistemas de evaluación estandarizados para poder decidir
con criterios rigurosos si los nuevos implantes que aparecen en el mercado con costes más elevados
tienen ventajas suficientes para cambiar indicaciones de implantes largamente probados.The exponential growth of the different models of THA actually in offer makes
difficult to the orthopaedic surgeon to find sound criteria for the selection of the proper implant.
This paper is an attempt to analyse the models actually in offer. We have identified 67 primary
THAs types and 19 revision models, commercialised by 24 companies at the catalonian community.
The number of variables, materials or designs between different patterns, independently of the size
of femoral and acetabular components, has been of 55. Only 25% of implants are supported by
reports in the orthopaedic literature. The cost range of implants varied from 70,000 to 300,570 pts.
for cemented prosthesis (average: 172,895); from 375,654 to 648,606 pts. for cementless models
(average: 480,391); the cost range for revision models varied from 412,552 to 713,000 pts., with an
average of 568,138 pts. Such a variety of designs and prices is greater than in other countries
of our environment, and the percentage of reports about clinical results that we have found is
smaller than the noticed by some authors. We believe that it would be necessary some long term
prospective studies and standarized evaluation systems in order to decide if the newer implants,
with more expensive price, have enough advantages to substitute the classic implants widely used
On the Stability of Non-Extremal Conifold Backgrounds with Sources
We present finite temperature solutions describing N_c D5 branes wrapped on
the S^2 of the resolved conifold in the presence of N_f flavor brane sources
and their backreaction, i.e. N_f/N_c ~ 1. In these solutions the dilaton does
not blow up at infinity but stabilizes to a finite value. Thus, we can use them
to generate new ones with D5 and D3 charge. The resulting backgrounds are
non-extremal versions of the "flavored" resolved deformed conifold. It is
tempting to interpret these solutions as gravity duals of finite temperature
field theories exhibiting non-trivial phenomena as Seiberg dualities, Higgsing
and confinement. However, a first necessary step in this direction is to
investigate their stability. We study the specific heat of these new flavored
backgrounds and find that they are thermodynamically unstable. Our results on
the stability also apply to some of the non-extremal backgrounds with
Klebanov-Strassler asymptotics found in the literature.Comment: 34+16 pages, 26 figures. Published versio
Drag Force in a Charged N=4 SYM Plasma
Following recent developments, we employ the AdS/CFT correspondence to
determine the drag force exerted on an external quark that moves through an N=4
super-Yang-Mills plasma with a non-zero R-charge density (or, equivalently, a
non-zero chemical potential). We find that the drag force is larger than in the
case where the plasma is neutral, but the dependence on the charge is
non-monotonic.Comment: 16 pages, 1 eps figure; v2: references added, typos fixed; v3: more
general ansatz, new nontrivial solution obtained, nonmonotonicity of the drag
force made explicit in new figure, version to appear in JHE
When white people experience the weight of the past:The role of white identity strategies in linking colonialism to current racial inequalities
How do White Europeans address racial inequalities in times of burgeoningdiscussions about colonialism? The current research explores the strategies that White people in the Netherlands use to manage their racial-ethnic identity in relation to linking colonialism and current racial inequalities. With this, we examined how White identity strategies were related to ideologies legitimizing racial inequalities. Using mixed-methods consisting of qualitative interviews (N = 24) and quantitative surveys (N = 564), we found that White people exhibited different combinations of prideful (“I am a proud person of our ethnic heritage”), dissociated (“My ethnic group does not have a significant impact on how I see the world”), and power-cognizant (“I am a White person with privileges because of my ethnic group”) identity strategies. Moreover, these White identity strategies were associated withlinking colonialism and racial inequalities and, thereby, with ideologies legitimizing them. Specifically, White people holding prideful and dissociated strategies were less likely to link colonialism and racial inequalities than White people who exclusively endorsed powercognizance. Furthermore, power-cognizant people challenged current-day racial inequalities the most. We conclude by discussing how White European people legitimize or question racial inequalities by managing their whiteness and the theoretical and practical implications of these findings
Consensus recommendations on sleeping problems in Phelan-McDermid syndrome
Early onset sleep problems and disorders are very common in individuals with Phelan-McDermid Syndrome (PMS) with rates of up to 90%. These sleep problems and disorders cannot be taken lightly. Not only do they have a major impact on the health, behaviour, functioning and learning opportunities of affected individuals, they can also have detrimental effects on the well-being and resilience of parents and caregivers, ultimately affecting the physical health, mental health and well-being of the whole social system. In this review we aim to understand the types and frequencies of sleeping problems in PMS as the basis for recommendations on their management and treatment and to provide general guidelines for clinicians and practitioners. We conducted an in-depth literature search, summarised findings, and participated in a series of consensus meetings with other consortium members - experts on PMS and stakeholders - to agree on guidelines and recommendations. In parallel, a world-wide survey was created and distributed amongst parents to include their perspective. Our literature search found only four articles specifically focused on sleeping problems in PMS, although some other articles mentioned prevalence and associated factors. Country-specific prevalence rates ranged between 24% and 46%, whereas our parental survey reported 59%. The main problems reported involved difficulty falling asleep and numerous night awakenings, with being restless in sleep, night-time incontinence, and tooth grinding also commonly reported. Only a small number of individuals had undergone a sleep study monitored by a specialist. Bedtime resistance normally decreases with age, but sleep-onset delay, sleep anxiety, parasomnias, problems falling and remaining asleep remain throughout lifespan, with total sleep time improving during adulthood. However, this improvement was also accompanied by a substantial increase in parasomnias. Ultimately, an increase in sleep disorders in children correlates with increased sleep disorders and daytime sleepiness in parents/caregivers. No study to date has focused on the underlying causes of sleeping problems in PMS, but comorbid mental health conditions, somatic causes, or (poly)pharmacy have been proposed as triggers for sleeping disturbances. Currently there is no PMS-specific treatment for sleeping problems, and current recommendations are mostly based on individuals with intellectual disability and/or neurodevelopmental conditions.</p
Geodesic Deviation Equation in Bianchi Cosmologies
We present the Geodesic Deviation Equation (GDE) for the
Friedmann-Robertson-Walker(FRW) universe and we compare it with the equation
for Bianchi type I model. We justify consider this cosmological model due to
the recent importance the Bianchi Models have as alternative models in
cosmology. The main property of these models, solutions of Einstein Field
Equations (EFE) is that they are homogeneous as the FRW model but they are not
isotropic. We can see this because they have a non-null Weyl tensor in the GDE.Comment: Submitted to Journal of Physics: Conference Series (JPCS), ERE200
Distanciamiento social ante la COVID-19: Simulación del aforo máximo de personas mediante PHP
Population confluence in internal or external areas considerably increases transmission of COVID-19, due to not respecting the social distancing established by the health system. The objective of this work was to make use of programming techniques,
using the PHP language (hypertext preprocessor), for the development of an application that simulates the maximum capacity of people who can enter an internal or external area. The methodology allowed recognizing common internal and external areas, configurating to the development environment, coding, simulation proposing and executing of the simulator where a practical case and ten places were evaluated to determine its reliability. The simulator provided the maximum capacity of people who can enter an internal or external area, complying with the social distancing of 2 m. The results made it possible to know that the use of information technologies through programming techniques and the PHP language contributed to being a technological alternative for the fight against the spread of the virus.La confluencia poblacional en áreas internas o externas incrementa considerablemente la trasmisión de la COVID-19, por no respetar el distanciamiento social que establece el sistema de salud. El objetivo de este trabajo fue hacer uso de técnicas de programación, empleando el lenguaje PHP (preprocesador de hipertexto), para el desarrollo de una aplicación que simule el aforo máximo de personas que pueden ingresar a un área interna o externa. La metodología permitió el reconocimiento de áreas internas y externas comunes, configuración al entorno de desarrollo, codificación, propuesta de simulación y ejecución del simulador donde se ha evaluado un caso práctico y diez lugares para determinar su confiabilidad. El simulador brindó el aforo máximo de personas que pueden ingresar a un lugar de área interna o externa cumpliendo el distanciamiento social de 2 m. Los resultados permitieron conocer que el uso de las tecnologías de información a través de las técnicas de programación y el lenguaje PHP contribuyó en ser una alternativa tecnológica para la lucha contra la propagación del virus
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