415 research outputs found
The Epigenetic Eeffects of Alcohol, AM630, and JWH-015 on Mmonocyte-Derived Dendritic Cell Function
Previous studies have demonstrated that substances of abuse such as alcohol (Aroor et al., 2014) and marijuana (Yang et al., 2014) play a role in epigenetically modifying gene expression in immune system cells through site-specific histone modifications. Interestingly, THC, the main psychotropic constituent in marijuana, is also known to interact with differentially associated genes responsible for cellular functions such as cell cycle regulation and metabolism (Yang et al., 2014). THC and related synthetic cannabinoids such as JWH-015 and AM630 are functionally similar in that they all bind to the two main cannabinoid receptors, CB1 and CB2 (Fattore & Fratta, 2011). Our own preliminary data analyzing histone modifications clearly revealed the ability of alcohol and the synthetic cannabinoid, JWH-015, to alter the presence of histones H3 and H4 in a previous model where treatments were administered chronically. In this model, alcohol and cannabinoids will be administered to monocyte-derived dendritic cells (MDDCs) at specific time points (24, 48, and 72 hours). Cells will be treated in-vitro with varying concentrations of alcohol (0.05, 0.1, 0.2, 0.3, and 0.4 %), the CB2 receptor agonist: JWH-015 (1,5, and 10 μM), and the CB2 receptor antagonist: AM630 (1,5,10 μM), in order to assess the ability of these substances to epigenetically modify the function of these key immune system cells. H3 and H4 histone quantification will be performed after treatments. The role of histone deacetylases will be confirmed by the use of histone deacetylase inhibitors, TSA and MGCD0103. Results emanating from this study will elucidate the epigenetic mechanisms of alcohol and cannabinoids on dendritic cell regulation
A BEM approach for grounding grid computation
16th International Conference on Boundary Element Methods, 1994, Southampton, England[Abstract] Grounding systems are designed to preserve human safety and grant
the integrity of equipments under fault conditions. To achieve these goals,
the equivalent electrical resistance of the system must be low enough to
ensure that fault currents dissipate (mainly) through the grounding electrode into the earth, while maximum potential gradients between close
points on the earth surface must be kept under certain tolerances (step
and touch voltages) [1,2].
In this paper, we present a Boundary Element approach for the numerical computation of grounding systems. In this general framework,
former intuitive widespread techniques (such as the Average Potential
Method) are identified as the result of specific choices for the test and
trial functions, while the unexpected anomalous asymptotic behaviour of
these kind of methods [3] is mathematically explained as the result of
suitable assumptions introduced in the BEM formulation to reduce computational cost. On the other hand, the use of high order elements allow to
increase accuracy, while computing time is drastically reduced by means
of new analytical integration techniques. Finally, an application example
to a real problem is presented
Una formulación aproximada mediante el método de elementos de contorno para la solución de problemas en teorÃa del potencial
2º Congreso de Métodos Numéricos en IngenierÃa, 1993, A Coruña[Resumen] El diseño de tomas de tierra para subestaciones eléctricas requiere el cálculo de la resistencia equivalente y la distribución de potencial en la superficie del terreno cuando se produce un ortocircuito [1]. Durante las dos últimas décadas
se han propuesto diversos métodos de cálculo, la mayor parte de los cuales se
fundamentan en ideas intuitivas como la superposición de fuentes puntuales de
corriente o el promediado del error [2,3]. A pesar del importante avance que han
supuesto estas técnicas, se han puesto de manifisto algunas anomalÃas notables
en su aplicación, tales como sus elevados requerimientos computacionales, los
resultados poco realistas que se obtienen al aumentar la segmentación de los
conductores, y la incertidumbre en su margen de error [3].
En este artÃculo se presenta una formulación 1D de Elementos de Contorno,
que incluye como casos particulares a los métodos intuitivos más ampliamente
utilizados en la actualidad. Las ideas sobre las que se fundamentan estos métodos
se contemplan como simplifiaciones adecuadas, introducidas en la formulación
BEM con el objetivo de reducir el coste computacional. Todo ello permite
explicar matemáticamente el anómalo comportamiento asintótico de esta clase de
métodos, e identificar las fuentes de error, asà como introducir elementos de orden
superior con el fin de incrementar la precisión. Finalmente se presenta un ejemplo
de aplicación a un problema real, utilizando nuevas técnicas de integración
analÃtica que permiten reducir drásticamente los tiempos de computación.Ministerio de Industria y EnergÃa; TC0722UPC-FECS
Formulaciones numéricas para el cálculo, diseño y evaluación de la seguridad de las redes de tierra de instalaciones eléctricas
Congreso de Métodos Numéricos en IngenierÃa 2005, Granada, SpainLa determinación de los niveles de potencial en la superficie del terreno cuando tiene
lugar una derivación de corriente es fundamental en el cálculo y diseño de redes de tierras de
subestaciones eléctricas.
En el presente trabajo se presenta una formulación numérica del método de elementos de
contorno para el análisis de un problema común en la ingenierÃa eléctrica, como es la existencia
de potenciales transferidos en una instalación de puesta a tierra. La transferencia de potenciales
entre la zona puesta a tierra y puntos exteriores de la misma a través de conductores
enterrados tales como circuitos de comunicación, neutros, tuberÃas, raÃles o cierres periféricos
metálicos, puede producir serios problemas de seguridad. En este artÃculo se analizan y calculan
problemas de potenciales inducidos por tomas de tierras de subestaciones considerando
modelos de terreno no uniformes y concretamente estratificados en dos capas. AsÃ, en primer
lugar se resume brevemente la formulación numérica empleada y el modelo bicapa considerado
y se presenta el análisis del problema de transferencia de potenciales. Finalmente, se muestran
algunos ejemplos haciendo uso de la geometrÃa real de una red de tierras de una subestación
eléctrica considerando diversos tipos de modelo de terreno
¿Son fiables los métodos convencionales para el cálculo de redes de puesta a tierra?
Congresso de Métodos Computacionais em Engenharia, Lisboa, 31 de Maio - 2 de Junho, 2004[Resumen] Para diseñar una toma de tierra es preciso calcular su resistencia equivalente y la distribución de potencial en la superficie del terreno durante una derivación de corriente [1, 2, 3]. Para elllo las normas sólo proponen fórmulas aproximadas para los casos más sencillos.
Desde los años 70 se han desarrollado métodos matriciales (Computer Methods) como el APM, en los que los electrodos se subdividen en segmentos cuyo comportamiento se modela a partir de
ideas intuitivas (superposición de fuentes de corriente puntuales, promediado del error, etc.) [1,
3, 4, 5, 6]. Sin embargo, la aplicación de estos métodos da lugar a anomalÃas desconcertantes al
aumentar la segmentación de los conductores, con la consiguiente incertidumbre en su margen
de error [2, 5].
Los autores han desarrollado una formulación de elementos de contorno en las que se enmarcan
los citados métodos matriciales. De esta forma, los metodos matriciales admiten finalmente
una fundamentación rigurosa, y es posible explicar su comportamiento asintóticamente
anómalo, asà como identificar las fuentes de error y valorar la fiabilidad de los resultados de
su aplicación.Ministerio de Ciencia y TecnologÃa; DPI2001-0556Ministerio de Ciencia y TecnologÃa; DPI2002-0029
Analysis of transferred earth potentials in grounding systems: a BEM numerical approach
[Abstract] In this work we present a numerical formulation for the analysis of a common problem in electrical engineering
practice, that is, the existence of transferred earth potentials
in a grounding installation [1]. The transfer of potentials
between the grounding area to outer points by buried
conductors, such as communication or signal circuits, neutral
wires, pipes, rails, or metallic fences, may produce serious
safety problems [2]. In this paper we summaryze the
BE numerical approach and we present a new technique for the transferred potential analysis. Finally, we show some examples by using the geometry of real grounding systems in different cases of transferred potentials.Ministerio de Ciencia y TecnologÃa; DPI2001-055
A numerical approach based on the BEM for computing transferred earth potentials in grounding analysis
Second MIT Conference on Computational Fluid and Solid Mechanics, Cambridge, USA[Abstract] In this paper we present a numerical approach based on the Boundary Element Method for the analysis
of a very common problem in electrical engineering practice: the existence of transferred earth potentials
in a grounding installation [1]. We propose a numerical approach to analyze this phenomenum. We demonstrate its feasibility by means of an application example with the geometry of a real grounding system.Ministerio de Ciencia y TecnologÃa; DPI2001-055
A validation of the boundary element method for grounding grid design and computation
[Abstract] Several widespread intuitive techniques developed during the last two decades for substation grounding analysis, such as the Average Potential Method
(APM), have been recently identified as particular cases of a more general Boundary Element formulation [1]. In this approach, problems encountered with the
application of these methods [3] can be explained from a mathematically rigorous point of view, and innovative advanced and more eficient techniques can be
derived [2].
Numerical results obtained with low and medium levels of discretization
(equivalent resistance and leakage current density) seem to be reasonable. However, these solutions still have not been validated. Unrealistic results are obtained when domain discretization is increased, since no one procedure is yet
available to eliminate the above mentioned problems. Hence, numerical convergence analyses are precluded. The obtention of highly accurate numerical
results by means of standard techniques (FEM, Finite Differences) implies unapproachable computing requirements in practical cases. On the other side,
neither practical error estimates have been derived, nor analytical solutions are
known for practical cases, nor suficiently accurate experimental measurements
have been reported up to this point.
In this paper, we present a validation of the results obtained by the Boundary Element proposed formulation, including the classical methods. A highly
accurate solution to a specially designed test problem is obtained by means of a
2D FEM model, using up to 80; 000 degrees of freedom. Results are compared
with those carried out by Boundary Elements
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