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Search Results: 1 - 10 of 219466 matches for " Cárdenas "
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An Iterative Method for Solving Two Special Cases of Lane-Emden Type Equation  [PDF]
Pedro Pablo Cárdenas Alzate
American Journal of Computational Mathematics (AJCM) , 2014, DOI: 10.4236/ajcm.2014.43021

In this work we apply the differential transformation method or DTM for solving some classes of Lane-Emden type equations as a model for the dimensionless density distribution in an isothermal gas sphere \"\" and as a study of the gravitational potential of (white-dwarf) stars ,\"\" which are nonlinear ordinary differential equations on the semi-infinite domain [1] [2]. The efficiency of the DTM is illustrated by investigating the convergence results for this type of the Lane-Emden equations. The numerical results show the reliability and accuracy of this method.

A Survey of the Implementation of Numerical Schemes for Linear Advection Equation  [PDF]
Pedro Pablo Cárdenas Alzate
Advances in Pure Mathematics (APM) , 2014, DOI: 10.4236/apm.2014.48052

The interpolation method in a semi-Lagrangian scheme is decisive to its performance. Given the number of grid points one is considering to use for the interpolation, it does not necessarily follow that maximum formal accuracy should give the best results. For the advection equation, the driving force of this method is the method of the characteristics, which accounts for the flow of information in the model equation. This leads naturally to an interpolation problem since the foot point is not in general located on a grid point. We use another interpolation scheme that will allow achieving the high order for the box initial condition.

A Survey of the Implementation of Numerical Schemes for the Heat Equation Using Forward Euler in Time  [PDF]
Pedro Pablo Cárdenas Alzate
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.213135
Abstract: We establish the conditions for the compute of the Global Truncation Error (GTE), stability restriction on the time step and we prove the consistency using forward Euler in time and a fourth order discretization in space for Heat Equation with smooth initial conditions and Dirichlet boundary conditions.
A Special Case of Variational Formulation for Two-Point Boundary Value Problem in L2(Ω)  [PDF]
Pedro Pablo Cárdenas Alzate
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.64065
Abstract: We consider the nonlinear boundary value problems for elliptic partial differential equations and using a maximum principle for this problem we show uniqueness and continuous dependence on data. We use the strong version of the maximum principle to prove that all solutions of two-point BVP are positives and we also show a numerical example by applying finite difference method for a two-point BVP in one dimension based on discrete version of the maximum principle.
Assessment and Monitoring Damage by Coraebus florentinus (Coleoptera: Buprestidae) in Mediterranean Oak Forests  [PDF]
Ana M. Cárdenas, Patricia Gallardo
Open Journal of Ecology (OJE) , 2018, DOI: 10.4236/oje.2018.85020
Abstract: Coraebus florentinus (Herbst) is a wood borer beetle that damages the most abundant Quercus species making up the Mediterranean forests. Damage is due to the feeding activity of the larvae which cuts the sap flow into the branch where it develops, drying it. In the last decades, the geographical range and the damage records of this species have expanded northwardly as a result of the climate global change since warmer conditions favor higher reproduction and quicker development of this species. On this paper, historical series of data after ten years evaluating damages by C. florentinus in Hornachuelos Natural Park (Southern Spain) are analyzed under the perspective of the environmental temperature increase linked to the global climate change. The assessment was done between 2007 and 2017, in two sampling plots of Mediterranean mixed-oak forests where holm and cork oaks are the predominant tree species. Results show that the infestation levels of this species at the beginning of the assessment period were higher than those described previously in the nineties and that they increased progressively during the monitoring time. The results also agree with the expansion of its distribution areas noticed in other areas of Europe. The foreseeable rising of damages of C. florentinus is discussed, at greater scale, under the perspective of future scenery of environmental warming and oaks decaying by losing fitness due to higher soil aridity.
?Y VERáS COMO QUIEREN EN CHILE...?: Un estudio sobre el prejuicio hacia los inmigrantes bolivianos por parte de los jóvenes chilenos
Cárdenas C,Manuel;
Ultima década , 2006, DOI: 10.4067/S0718-22362006000100006
Abstract: the main objective of this study was to investigate in the forms that the prejudice takes towards the immigrants of bolivian origin. we have used the typology that stem from the scales of subtle and blatant prejudice (pettigrew and meertens, 1995) to compare to the subjects in different psycosocial variables relevant in the existing literature on prejudice and racism. the sample was formed of 167 school students of last year of average education, belonging to diverse education centers both public and private of the antofa-gasta city, chile.
Psicología social y contexto: sobre la fuerza de las situaciones sociales perversas
Manuel Cárdenas C.
Límite , 2006,
Abstract: Para entender la conducta de los sujetos y comprender lo que pasa al interior de los individuos haríamos mejor si dejásemos de mirar únicamente al interior de éstos y nos centramos en las condiciones sociales que sirven de marco para su acción. De lo que se trata es de mirar afuera para comprender lo que pasa dentro, de entender que las acciones correctivas sobre ciertos fenómenos sociales sólo son posibles de ser abordadas desde los marcos que delimitan la acción de los individuos y sus relaciones, y no pueden ser achacadas exclusivamente a éstos. Para abordar este tema se hace referencia a tres conocidos experimentos en Psicología Social que nos muestran qué ocurre cuando los sujetos son puestos en situaciones perversas.
Laser in medicine Láser en medicina
Juan C. Cárdenas
Iatreia , 1993,
Abstract: The fundamentals of laser functioning and a brief historic description on the subject are presented; laser Is classified according to emission potency, materials with which it is built and pulsation. Different mechanisms of action of laser as well as Its indications and contraindications are discussed. Emphasis is given to low-power laser. Local and foreign experiences with Its medlcal use are briefly described Se revisan los principios fundamentales del funcionamiento del láser, se hace una breve revisión histórica del mismo y se lo clasifica de acuerdo con la potencia de emisión, los materiales de fabricación y la pulsación. Se enumeran los diferentes mecanismos de acción del láser y sus indicaciones y contraindicaciones haciendo énfasis en lo concerniente al láser de baja potencia, tanto pulsado como no pulsado; se alude a las experiencias nacionales y de otros países.
Y veras como quieren en Chile... : Un estudio sobre el prejuicio hacia los inmigrantes bolivianos por parte de jóvenes chilenos
Manuel Cárdenas C.
Ultima Década , 2006,
Abstract: El objetivo principal de este estudio fue indagar en las formas que toma el prejuicio hacia los inmigrantes de origen boliviano. Hemos utilizado las tipologías que se derivan de las escalas de prejuicio sutil y manifiesto (Pettigrew & Meertens, 1995) para comparar a los sujetos en diferentes variables psicosociales relevantes en la literatura existente sobre prejuicio y racismo. La muestra se compuso de 167 estudiantes de último a o de ense anza media, pertenecientes a diversos centros educacionales, tanto públicos como privados de la ciudad de Antofagasta, Chile.
Evasion of the Interferon-Mediated Antiviral Response by Filoviruses
Washington B. Cárdenas
Viruses , 2010, DOI: 10.3390/v2010262
Abstract: The members of the filoviruses are recognized as some of the most lethal viruses affecting human and non-human primates. The only two genera of the Filoviridae family, Marburg virus (MARV) and Ebola virus (EBOV), comprise the main etiologic agents of severe hemorrhagic fever outbreaks in central Africa, with case fatality rates ranging from 25 to 90%. Fatal outcomes have been associated with a late and dysregulated immune response to infection, very likely due to the virus targeting key host immune cells, such as macrophages and dendritic cells (DCs) that are necessary to mediate effective innate and adaptive immune responses. Despite major progress in the development of vaccine candidates for filovirus infections, a licensed vaccine or therapy for human use is still not available. During the last ten years, important progress has been made in understanding the molecular mechanisms of filovirus pathogenesis. Several lines of evidence implicate the impairment of the host interferon (IFN) antiviral innate immune response by MARV or EBOV as an important determinant of virulence. In vitro and in vivo experimental infections with recombinant Zaire Ebola virus (ZEBOV), the best characterized filovirus, demonstrated that the viral protein VP35 plays a key role in inhibiting the production of IFN-α/β. Further, the action of VP35 is synergized by the inhibition of cellular responses to IFN-α/β by the minor matrix viral protein VP24. The dual action of these viral proteins may contribute to an efficient initial virus replication and dissemination in the host. Noticeably, the analogous function of these viral proteins in MARV has not been reported. Because the IFN response is a major component of the innate immune response to virus infection, this chapter reviews recent findings on the molecular mechanisms of IFN-mediated antiviral evasion by filovirus infection.
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