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Search Results: 1 - 10 of 244099 matches for " I. E. Medina-Ramirez "
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Computational treatment of traveling-wave solutions of a population model with square-root dynamics
J. E. Macias-Diaz,I. E. Medina-Ramirez
Advanced Studies in Biology , 2013,
Abstract: Motivated by a recent report by R. E. Mickens, we design an efficient,non-standard, two-step, nonlinear, explicit, exact finite-differencemethod to approximate solutions of a population equation with squarerootreaction law. Mickens’ report establishes the existence of nonnegative,traveling-wave solutions of that model which are boundedfrom above by 1, and which are spatially and temporally monotone.As its analytic counterpart, the computational technique proposed inthe present manuscript is capable of preserving the non-negativity andthe boundedness of initial profiles under suitable and flexible conditionson the computational parameters. We provide theoretical results on theexistence and uniqueness of non-negative and bounded solutions of themethod, and we establish that our technique conditionally preserves thespatial and temporal monotonicity of the approximations. The numericalsimulations obtained through a computer implementation of ourfinite-difference scheme support the fact that the method preserves allof the mathematical characteristics of approximations mentioned above.
Semantic Information Retrieval: a return on experience
R. Carolina Medina-Ramirez
Engineering Letters , 2007,
Abstract:
A TEM Study of Cobalt-Base Alloy Prototypes Fabricated by EBM  [PDF]
Sara M. Gaytan, Larry E. Murr, Diana A. Ramirez, Brenda I. Machado, Edwin Martinez, Daniel H. Hernandez, Jose L. Martinez, Francisco Medina, Ryan B. Wicker
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.25046
Abstract: A novel microstructural architecture consisting of Cr23C6 carbide spatial columns was created in solid components of Co-26Cr-6Mo-0.2C fabricated from powder by additive manufacturing using electron beam melting. These columns of carbides extended in the build direction and are formed by the x-y rastering of the electron beam to pre-heat and melt powder layers using CAD models. These microstructural architectures are similar to rapidly solidified/unidirectionally solidified structures created by heat extraction in the direction perpendicular to the build plane. These columnar carbide architectures were observed by optical metallography and transmission electron microscopy (TEM) and compared with intrinsic stacking fault microstructures observed in annealed components. The TEM analysis allowed the details of the carbide crystal structure and corresponding cubic morphology to be observed.
Ciprofibrate diminishes NON-HDLc and improves HDLc in patients with Frederickson type IV dyslipidemia phenotype
Bermúdez-Pirela,V; Souki,A; Cano-Ponce,C; Bermúdez-Arias,F; Mengual-Moreno,E; Leal-Gonzalez,E; Lemus-Antepaz,M; Cabrera de B,M; Amell de D,A; Leal de P,N; Cano-Pe?aloza,R; Puche-Medina,G; Ramirez,I; Contreras,F; Velasco,M;
Archivos Venezolanos de Farmacología y Terapéutica , 2005,
Abstract: objective: hypertriacylglyceridemia and low hdlc combination is one of the most common lipidic abnormalities. thus, the aim of this study was to determine the effects of ciprofibrate on patients with frederickson?s type iv dyslipidemia phenotype. research design and methods: 75 patients with type iv dyslipidemia were assigned at random to one of two therapeutic options: group a, aha diet and physical activity and b, aha diet, physical activity and ciprofibrate 100 mg daily for 12 weeks. all patients underwent lipidic profile quantification before and after therapeutic intervention. results: ciprofibrate treatment group exhibited significantly reduction in total cholesterol (-14,2% vs. -4,8%; p<0,02), triglycerides (-38% vs. -21,6%; p<0,007), vldlc (-38% vs. -21,6%; p<0,007) non-hdlc (-20,5% vs. -7,1%; p<0,007) and total cholesterol to hdlc ratio (-25,6% vs. -9,4%; p<0,01) when comparing with diet/physical activity group . hdlc showed an important increase in ciprofibrate group when contrast with diet/physical activity group (+25% vs. +9,6%, p<0,02). conclusions: ciprofibrate treatment effectively reduced triglycerides rich particles and non-hdlc and significantly increased hdlc, proving it?s usefulness in low hdlc syndrome and type iv frederickson?s hyperlipidemia.
Crioconservación espermática en peces, un acercamiento en Siluriformes
Ramirez-Merlano,Juan A; Medina Robles,Victor M; Cruz-Casallas,Pablo E;
ORINOQUIA , 2010,
Abstract: this review compile information concerning to fish semen cryopreservation, based on experiences in different species of catfish. the siluriformes include genera with a high potential for the continental aquaculture. however, the investigations in this field are scarce. the introduction of this method in the fish farming industry has generated benefits in pro of improving the population and the diversification of species with destiny to commercial production. the cryopreservation involves certain parameters in search of efficiency in the protocols and it offers of diminishing the damages caused by the mechanical stress and the extreme temperature changes, which induce a decrease in the sperm population. different freezing protocols vary widely in answer post-thawed on factors such as motility, structure and function of the sperm cell, factors such as motility, structure and function of the sperm cell, features that may generate an adverse response in the fertilization of oocytes, and which are discussed in this article.
Patrones de actividad forrajera y tama o de nido de Acromyrmex lobicornis (Hymenoptera: Formicidae) en una zona urbana de San Luis, Argentina Foraging activity patterns and nest size of Acromyrmex lobicornis (Hymenoptera: Formicidae) in an urban zone of San Luis, Argentina
Laura E. Jofré,Ana I. Medina
Revista de la Sociedad Entomol?3gica Argentina , 2012,
Abstract: Diversos factores pueden influir sobre la actividad de forrajeo de las hormigas cortadoras de hojas. Sin embargo, los factores climáticos, especialmente la temperatura, pueden ser considerados los más importantes en las regiones templadas. Se midió la actividad de forrajeo y el tama o del nido en cuatro colonias de Acromyrmex lobicornis Emery en la localidad de Juana Koslay, San Luis. La actividad forrajera se determinó a partir del número de hormigas que ingresan al nido cargadas con fragmentos vegetales por unidad de tiempo, a lo largo de un a o. Se midió la temperatura del aire y el suelo en cada oportunidad. Para estimar el tama o del nido, se midió el área de forrajeo, el diámetro del túmulo y el número de obreras en cada colonia. Se encontraron asociaciones entre la actividad de forrajeo y las temperaturas del aire y del suelo en todos los meses del a o, a excepción de febrero, julio y diciembre. Esta asociación fue positiva en los meses de octubre, mayo, junio, agosto y setiembre; pero negativa en los meses de noviembre, enero, marzo y abril. Las colonias mostraron actividad diurna en invierno y nocturna en verano. La temperatura y el tama o del nido son factores que influyen sobre la actividad de forrajeo de A. lobicornis. Many factors can affect the foraging activity of leaf-cutting ants. However, climatic factors, especially temperature, could be considered the most important in temperate regions. In this work, we measured foraging activity and nest size in four colonies of Acromyrmex lobicornis Emery located in Juana Koslay, San Luis. Foraging activity was determined by the number of ants carrying plant fragments that entered the nest per unit time during a year. In each opportunity air and soil temperature were measured. To estimate nest size we used foraging area, mound diameter and number of workers in each colony Foraging activity and air and soil temperature correlated in every month of the year except February, July and December. However, the correlation was positive during October, May, June, August and September, and negative in November, January, March and April. The nests showed activity all the year, but diurnal in winter and nocturnal in summer. The temperature and the nest size are factors that influence the foraging activity of A. lobicornis.
Geometry of the Banach spaces C(beta mathbb N times K, X) for compact metric spaces K
Dale E. Alspach,Elói Medina Galego
Mathematics , 2010,
Abstract: A classical result of Cembranos and Freniche states that the C(K, X) spaces contains a complemented copy of c_0 whenever K is an infinite compact Hausdorff space and X is an infinite dimensional Banach space. This paper takes this result as a starting point and begins a study of the conditions under which the spaces C(alpha), alpha
A complete classification of the spaces of compact operators on C([1,alpha], l_p) spaces, 1
Dale E. Alspach,Elói Medina Galego
Mathematics , 2014,
Abstract: We complete the classification, up to isomorphism, of the spaces of compact operators on C([1, gamma], l_p) spaces, 1
A thermodynamic counterpart of the Axelrod model of social influence: The one-dimensional case
Y. Gandica,E. Medina,I. Bonalde
Computer Science , 2012, DOI: 10.1016/j.physa.2013.08.033
Abstract: We propose a thermodynamic version of the Axelrod model of social influence. In one-dimensional (1D) lattices, the thermodynamic model becomes a coupled Potts model with a bonding interaction that increases with the site matching traits. We analytically calculate thermodynamic and critical properties for a 1D system and show that an order-disorder phase transition only occurs at T = 0 independent of the number of cultural traits q and features F. The 1D thermodynamic Axelrod model belongs to the same universality class of the Ising and Potts models, notwithstanding the increase of the internal dimension of the local degree of freedom and the state-dependent bonding interaction. We suggest a unifying proposal to compare exponents across different discrete 1D models. The comparison with our Hamiltonian description reveals that in the thermodynamic limit the original out-of-equilibrium 1D Axelrod model with noise behaves like an ordinary thermodynamic 1D interacting particle system.
Una estrategia instruccional para el laboratorio de Física I usando la "V de Gowin"
Sanabria, I;M, Ramirez de M;Aspée, M;
Revista mexicana de física , 2006,
Abstract: this research emerges from a concern of a unet teacher's research team called grupo de investigacion epistemológica en el aprendizaje las ciencias duras, to generate strategies in order to facilitate the learning of physics. there is a tool that has shown to be very effective in faciliting the learning: the gowin's vee, it has multiple uses: teachers use it to facilitate learning in the lab, to improve the planning and organization of research, as well as for reporting studies. most of the teachers and students at the unet did not know this tool, however its use has been proved in some educational contexts and many studies favor its use in the learning process. this research that lead to the design and trial out of a strategy called "the practices in the physics lab: using the gowin's vee as a tool of learning" emerges as an attempt to transform the physics lab in adequate space for the development of scientific thinking skills. instructional design and content experts evaluated the strategy and found it apropiate, adecuate and useful to facilitate experimental physic's learning.
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