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Search Results: 1 - 10 of 235982 matches for " Maria E. Riveros "
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Histamine and motivation
Fernando Torrealba,Maria E. Riveros,Jose L. Valdes
Frontiers in Systems Neuroscience , 2012, DOI: 10.3389/fnsys.2012.00051
Abstract: Brain histamine may affect a variety of different behavioral and physiological functions; however, its role in promoting wakefulness has overshadowed its other important functions. Here, we review evidence indicating that brain histamine plays a central role in motivation and emphasize its differential involvement in the appetitive and consummatory phases of motivated behaviors. We discuss the inputs that control histaminergic neurons of the tuberomamillary nucleus (TMN) of the hypothalamus, which determine the distinct role of these neurons in appetitive behavior, sleep/wake cycles, and food anticipatory responses. Moreover, we review evidence supporting the dysfunction of histaminergic neurons and the cortical input of histamine in regulating specific forms of decreased motivation (apathy). In addition, we discuss the relationship between the histamine system and drug addiction in the context of motivation.
Periodic motions: How their period changes with amplitude of the oscillations and the friction?
H. G. Riveros,E. Cabrera Bravo
Latin-American Journal of Physics Education , 2007,
Abstract: The pendulum is a classical experiment, easy to perform and produces data with very simple equipment. The change in the period with the amplitude appears even with small amplitudes if you have some precision in the period. To measure amplitudes larger than 90° we need to change the cord for a rigid rod. We found that for a cylindrical magnet hanging horizontally in the Earth magnetic field, the movement equation is similar to that of a pendulum. We measured amplitudes and times so we can fit a numerical solution to the equation. The initial amplitude is near to 162° and we found that the change in the period comes mainly from the non-linear terms in the equation, and that the friction (either proportional to the angular velocity or its square) only reduces the amplitude with time. With periods from 9 to 4 seconds, the measurements with a protractor can be made manually for many oscillations. For the umerical calculations Δt needs to be 0.0001 seconds to conserve the energy.
A decomposition of a measurable function f by a one-sided local sharp maximal function and applications to one-sided operators
R. E. Vidal,M. S. Riveros
Mathematics , 2014,
Abstract: Following the ideas of Andrei Lerner in [ A pointwise estimate for the local sharp maximal function with applications to singular integrals" Bull. London Math. Soc. 42 (2010) 843856], we obtain another decomposition of an arbitrary measurable function f in terms of local mean oscillations. This allows us to get new estimates involving one-sided singular integrals and one-sided maximal operator. As an application to this result we obtain two weighted inequality for one-sided singular integrals and a L(w) inequality relating a measurable function f and sharp one-sided operator. These estimates are more precise in sense that they are valid for a greater class of weights.
Contenido de glicosaminoglicanos del líquido sinovial de la articulación metacarpofalángica de caballos castrados y yeguas de diferentes edades
Archivos de medicina veterinaria , 2003, DOI: 10.4067/S0301-732X2003000100005
Abstract: total concentration of synovial fluid glycosaminoglycan (gags) and a fraction of it (gagst) which correspond to different gags from hyaluronic acid or sulfated gags (gagss) that mainly consist of chondroitin sulfate and keratan sulfate, were measured. samples of synovial fluid were taken from normal metacarpophalangeal joints of crossbred equines immediatelly after slaughter by aseptic needle aspiration. post mortem joints examination showed that there was no gross evidence of osteoarthritis or other joint disease, based on the appearance of synovial membrane and articular cartilage. synovial fluid samples were evaluated by its external appearance, protein concentration and mucin clot test. samples were alloted in four age groups by teeth examination and divided in mares (m) and castrated horses (c.h.) as follows: 1.5 - 2 years (n = 23: 12 m. and 11 c.h.; 4 - 5 years (n = 15: 9 m. and 6 c.h.); 6 - 8 years (n = 23: 13 m. and 10 c.h.) and over 10 years old (n = 17: 12 m. and 5 c.h.). a colorimetric method with alcian blue using different electrolyte concentrations was used to quantify these gags. there were no significant differences of gagst concentration between mares and castrated horses, but the average of both older groups ( 10 years) was lower (1.71 ± 0.79 mg/ml) than the previous age group (3.39 ± 1.93 mg/ml). the gagss content of the synovial fluid, that reflects the catabolic processes of extracellular matrix (mec) of the articular cartilage, showed no differences between mares and castrated horses in any age group, but these concentrations were always higher in castrated horses. however, the final average of these gagss, was higher (p the difference bettween gagst and gagss represents the concentration of synovial fluid hyaluronic acid, which was lower in the older group of mares (1.62 ± 0.76 mg/ml) and castrated horses (0.96 ± 0.64 mg/ml), suggesting a greater susceptibility to cartilage damage in these animals. these results verify the effect of age or sex
Prosopis alpataco Phil. (Fabaceae, Mimosoideae)
Cecilia Vega Riveros,Pablo A Meglioli,Pablo E Villagra
Kurtziana , 2011,
Contenido de glicosaminoglicanos del líquido sinovial de la articulación metacarpofalángica de caballos castrados y yeguas de diferentes edades Synovial fluid glycosaminoglycan concentration in metacarpophalangeal joint of castrated horses and mares of different ages
Archivos de medicina veterinaria , 2003,
Abstract: Se midió la concentración de glicosaminoglicanos (GAGs) del líquido sinovial en su valor total (GAGsT) y de una fracción de éstos, que corresponde a los GAGs diferentes del ácido hialurónico o GAGs sulfatados (GAGsS), entre los que se describen condroitin sulfato y queratán sulfato. Las muestras de líquido sinovial se obtuvieron por artrocéntesis aséptica desde articulaciones metacarpofalángicas normales de equinos mestizos en matadero, después del beneficio de los animales. El exámen post mortem de las articulaciones permitió descartar articulaciones con evidencias de osteoartritis u otras patologías articulares. La normalidad del líquido sinovial se evaluó por de su aspecto y por las pruebas del coágulo de mucina y de concentración de proteínas (<15mg/ml). Se escogieron 4 grupos de edad que se dividieron a su vez, en yeguas (y.) y caballos castrados (c.c.), de la siguiente forma: 1,5 - 2 a os (n = 23: 12 y. y 11 c.c.; 4 - 5 a os (n = 15: 9 y. y 6 c.c.); 6 - 8 a os (n = 23: 13 y. y 10 c.c.) y sobre 10 a os de edad (n = 17: 12 y. y 5 c.c.). Para cuantificar los GAGs se utilizó un método colorimétrico con Alcian Blue usando diferentes concentraciones de MgCl2. Al comparar la concentración de GAGsT entre yeguas y caballos castrados, no se encontraron diferencias significativas. Sin embargo, al analizar el promedio del grupo mayor de 10 a os de ambos sexos (1.71 ± 0.79 mg/ml), éste fue inferior (p< 0.05) con respecto al grupo de 6 a 8 a os (3.39 ± 1.93 mg/ml). El contenido de GAGsS, que refleja la actividad catabólica de la MEC del cartílago, no mostró diferencias entre yeguas y caballos castrados en cada grupo de edad. Sin embargo, el promedio de estos GAGsS fue mayor (p< 0.05) en los caballos castrados (0.48 ± 0.28 mg/ml) que en las yeguas (0.34 ± 0.15 mg/ml) y tienden a disminuir a través de la edad en ambos grupos. La diferencia entre los GAGsT y los GAGsS, permitió estimar el contenido de ácido hialurónico del líquido sinovial, cuyo perfil fue semejante al de los GAGsT. Su concentración fue menor en el grupo de mayor edad de yeguas (1.62 ± 0.76 mg/ml) y de caballos castrados (0.96 ± 0.64 mg/ml). Estos resultados apoyan la influencia de la edad y de la condición de sexo sobre la concentración de GAGs en el líquido sinovial, lo que podría reflejar la condición metabólica de los componentes articulares y que podría ser útil para la comparación con las patologías articulares Total concentration of synovial fluid glycosaminoglycan (GAGs) and a fraction of it (GAGsT) which correspond to different GAGs from hyaluronic acid or sulfated GAGs (GAGsS) that mainly
A Program for Electronic Medical Education in Colombia: Educación Electrónica Estructurada (E3) A Succesful Experience
Rafael E Riveros,Andres Isaza,Andres Espinosa,Felipe Lobelo
Journal of Systemics, Cybernetics and Informatics , 2004,
Abstract: Medical education in Colombia remains, almost completely, with the physical presence of the lecturer in the classroom. In recent years, new alternatives in higher education have been explored, on a balanced basis. Our faculty traditionally remains teaching with conservative methods; therefore, strategies for incorporating informatics, virtual education and in general, electronics are vital in our academic environment. Our electronic medical education group, E3, is constituted by faculty, undergraduate and graduate students. E3 was designed to provide the urgent need to develop an appropriate scenario for a group of faculty and students who will provide the school with clear cut policies and strategies, to establish a permanent and dynamic program of ICT locally, institutionally and regionally. The project, enveloped in the objectives of E3 includes: Electronic Academic Contents (EAC), Virtual Education Project (VEP) and Electronic Clinical Record (ECR). We will improve and increase, by the end of 2003, electronic medical education at our School and radiate to the University and the academic community.
Amphibia, Anura, Leiuperidae, Pleurodema thaul (Lesson, 1827): Altitudinal distribution extension and new records from its northern range
Quezada, C. C.,Riveros, E.,Lobos, G.,Velásquez, N.
Check List , 2010,
LSDA+U approximation-based analysis of the electronic estructure of CeFeGe3
E. Chigo Anota,A Flores Riveros,J. F. Rivas Silva
Physics , 2005, DOI: 10.1142/S0217979206033243
Abstract: We perform ab initio electronic structure calculations of the intermetallic compound CeFeGe3 by means of the Tight Binding Linear Muffin-Tin Orbitals-Atomic Sphere Approximation (TB-LMTO-ASA) within the Local Spin Density Approximation containing the so-called Hubbard correction term (LSDA+U^SIC), using the Sttutgart's TB (Tight Binding)-LMTO-ASA code in the framework of the Density Funcional Theory (DFT).
Fracture Response of Reinforced Concrete Deep Beams Finite Element Investigation of Strength and Beam Size  [PDF]
Guillermo A. Riveros, Vellore Gopalaratnam
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.411212
Abstract: This article presents a finite element analysis of reinforced concrete deep beams using nonlinear fracture mechanics. The article describes the development of a numerical model that includes several nonlinear processes such as compression and tension softening of concrete, bond slip between concrete and reinforcement, and the yielding of the longitudinal steel reinforcement. The development also incorporates the Delaunay refinement algorithm to create a triangular topology that is then transformed into a quadrilateral mesh by the quad-morphing algorithm. These two techniques allow automatic remeshing using the discrete crack approach. Nonlinear fracture mechanics is incorporated using the fictitious crack model and the principal tensile strength for crack initiation and propagation. The model has been successful in reproducing the load deflections, cracking patterns and size effects observed in experiments of normal and high-strength concrete deep beams with and without stirrup reinforcement.
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