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Search Results: 1 - 10 of 302646 matches for " Vargas J. "
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Nucleocytoplasmic Gynodioecy  [PDF]
R. Doroteo, J. A. Vargas
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.412226

We study the evolution of a gynodioecious species under mixed-mating through a nucleocytoplasmic male sterility model. We consider two cytoplasmic types and a nuclear locus with two alleles. Here, the interaction between one cytoplasmic type and a recessive nuclear male-sterility factor gives rise to only one female genotype, while the remaining types correspond to hermaphroditic plants. We include two fitness paramaters: the advantageous female fitness t of females relative to that of hermaphrodites; and a silent and dominant cost of restoration, that is, a diminished fitness for plants carrying a dominant restorer gene relative to that of hermaphrodites. The parameter related to the cost of restoration is assumed to be present on outcrossing male fertility only. We find that every population converges to a stable population. We also determine the nature of the attracting stable population, which could be a nucleocytoplasmic polymorphism, a nuclear polymorphism or another population with some genotypes absent. This depends on the position of t with respect to critical values expressed in terms of the other parameters and also on the initial population.

Vargas J.
Revista de la Facultad de Medicina Veterinaria y de Zootecnia , 2005,
Abstract: Una enfermedad celular puede darse por acumulaciones de sustancias endógenas o exógenas. Uno de los pigmentos endógenos que puede ser recaptado en las células es la melanina. Los neoplasmas melanocíticos son comunes en especies domesticas, pero no en bovinos, en quienes el número de reportes es sustancialmente menor. La búsqueda paralela para el tratamiento del melanoma tanto en humanos como en animales domésticos incluye técnicas quirúrgicas, farmacológicas e incluso ha llevado al estudio y manipulación genética de algunas especies. La problemática del melanoma va más allá del simple aspecto cosmético: los melanomas, e incluso los melanocitomas, pueden presentar cursos agresivos asociados con la disminución en la calidad de vida del animal o con su muerte.
Vena cava superior izquierda persistente asociada con cardiopatías congénitas
Vargas,Florentino J.;
Revista argentina de cardiolog?-a , 2008,
Abstract: persistent left superior vena cava associated with congenital heart defects is generally a benign finding without hemodynamic impact which does not need surgery. nevertheless, in some circumstances, it may result a condition needing a treatment, or it may be necessary to perform certain modifications in surgical techniques used for other congenital heart defects. the present article deals with a review of those situations in which a persistent left superior vena cava needs a specific surgical approach. in addition, an original surgical procedure used in these patients, which has been recently reported by our team, is commented in relationship with each of the different anatomic presentations.
Vena cava superior izquierda persistente asociada con cardiopatías congénitas
Florentino J. Vargas
Revista Argentina de Cardiología , 2008,
Abstract: La persistencia de la vena cava superior izquierda asociada con cardiopatías congénitas suele ser un hallazgo benigno, sin repercusión hemodinámica ni quirúrgica. Sin embargo, en ocasiones su presencia puede constituir una entidad fisiopatológica que requiere tratamiento o conducir a modificaciones en las técnicas quirúrgicas utilizadas para otras malformaciones. Estas situaciones en las que la presencia de la vena cava superior izquierda requiere un abordaje quirúrgico específico son motivo de revisión en el presente trabajo. Asimismo, se comenta una técnica quirúrgica original utilizada en estos pacientes, y recientemente comunicada por nuestro grupo, en relación con cada una de las diferentes presentaciones anatómicas.
Cirugía cardiovascular con circulación extracorpórea en recién nacidos de bajo peso
Florentino J. Vargas
Revista Argentina de Cardiología , 2010,
Influencia de un sólido sobre el secado de mezclas líquidas parcialmente miscibles
M. Vargas,J. Martínez
Nexo , 2006,
Abstract: Un estudio experimental del secado convectivo de un sólido humedecido con una mezcla líquida que exhibe separación de fases durante el proceso de evaporación ha sido efectuado. Los experimentos fueron realizados en un secador de túnel a escala de laboratorio bajo diferentes condiciones de operación tales como temperatura y velocidad del gas así como diferentes composiciones de las mezclas líquidas. Se humedeció el sólido con mezclas binarias y ternarias, y se efectuó la evaporación a partir de la superficie libre líquida. Se utilizo como humedad el sistema binario agua-hexano y la mezcla ternaria agua-hexano-etanol, ambos involucrados en la extracción de biopesticida a partir de semillas de nim. Esferas de vidrio y semillas de nim trituradas fueron usadas como sólido. La densidad y el índice de distribución másico de las fases tienen gran influencia en el proceso de evaporación. Si la fase menos densa del hexano esta en exceso, la superficie es cubierta solamente por esta fase y no existe evaporación de la otra fase hasta que el índice de distribución másico es tal que la segunda fase es expuesta al gas. La presencia de un sólido poroso interrumpe este patrón y la fase más densa puede ser removida simultáneamente incluso a bajas fracciones de esta última. En este caso, también la forma en que el sólido fue humedecido tiene influencia en el proceso.
Regge Calculus in Teleparallel Gravity
J. G. Pereira,T. Vargas
Physics , 2002, DOI: 10.1088/0264-9381/19/19/301
Abstract: In the context of the teleparallel equivalent of general relativity, the Weitzenbock manifold is considered as the limit of a suitable sequence of discrete lattices composed of an increasing number of smaller an smaller simplices, where the interior of each simplex (Delaunay lattice) is assumed to be flat. The link lengths between any pair of vertices serve as independent variables, so that torsion turns out to be localized in the two dimensional hypersurfaces (dislocation triangle, or hinge) of the lattice. Assuming that a vector undergoes a dislocation in relation to its initial position as it is parallel transported along the perimeter of the dual lattice (Voronoi polygon), we obtain the discrete analogue of the teleparallel action, as well as the corresponding simplicial vacuum field equations.
Many disjoint edges in topological graphs
Andres J. Ruiz-Vargas
Mathematics , 2014,
Abstract: A monotone cylindrical graph is a topological graph drawn on an open cylinder with an infinite vertical axis satisfying the condition that every vertical line intersects every edge at most once. It is called simple if any pair of its edges have at most one point in common: an endpoint or a point at which they properly cross. We say that two edges are disjoint if they do not intersect. We show that every simple complete monotone cylindrical graph on $n$ vertices contains $\Omega(n^{1-\epsilon})$ pairwise disjoint edges for any $\epsilon>0$. As a consequence, we show that every simple complete topological graph (drawn in the plane) with $n$ vertices contains $\Omega(n^{\frac 12-\epsilon})$ pairwise disjoint edges for any $\epsilon>0$. This improves the previous lower bound of $\Omega(n^\frac 13)$ by Suk which was reproved by Fulek and Ruiz-Vargas. We remark that our proof implies a polynomial time algorithm for finding this set of pairwise disjoint edges.
Procedural Utility in the Work Place, Evidence from Mexico  [PDF]
André Vargas
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.49104
Abstract: The concept of Utility usually refers to the satisfaction a person acquires by consuming, in general under circumstances bonded to income, and the price of goods. In a psychological vision of personal well-being, happiness and its components, consider the fact that people can value anything. This notion has led to the study of Procedural Utility, that means people not only value the outcome of something, but also values the process and conditions in which the outcome is achieved. Procedural Utility can be obtained from various economic procedures in which individuals are part of, e.g. Work and consumption among others. Evidence has been found that in the work place the fact of being attached to hierarchy generates negative Procedural Utility because it disrupts psychological precepts that determine happiness, well-being, or utility [1]. In other cases it has been found that the process on how a wage cut is done must be considered [2]. In the light of this phenomena, I’ll discuss the concept of Procedural Utility and analyze empirical evidence for the Mexican case with “Instituto Nacional de Estadistica y Geografía” INEGI’s self-reported well-being survey (BIARE), with the finality to give suggestions on possible applications of processes to improve the worker’s satisfaction.
On Fostering a Co-Creative Process within a CSCL Framework  [PDF]
J. R. Rojano-Caceres, F. Ramos-Quintana, M. D. Vargas-Cerdán
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.34061
Abstract: In this article is introduced a co-creative process fostered by a Collaborative Learning Framework which pursues to engage peers of students in a synchronous collaborative dynamic to build the knowledge by representing it by a formal digraph called Networks of Concepts (NoC). This digraph, the NoC, allows building and representing the knowledge in a synthetic way, whilethe co-creative process aims at developing cognitive skills and collaborative attitudes as essential part of 21st century skills for students. Nowadays,the Collaborative Learning Framework has been and is currently being used in Mexican universities in different undergraduate programs such as Industrial Engineering, Computer Science, Sociology, Accounting, Business Administration, and Molecular Biology; in this article we analyze and discuss a particular case of an example in the Engineering program. Thus, the analyzed digraphs are the outcome of a co-creative process that is carried out through synchronous-mode argumentation and shared interactions by peers of students.
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