Dependences of the Casimir-Polder interaction between an atom and a cavity wall on atomic and material properties

The Casimir-Polder and van der Waals interactions between an atom and a flat cavity wall are investigated under the influence of real conditions including the dynamic polarizability of the atom, actual conductivity of the wall material and nonzero temperature of the wall. The cases of different atoms near metal and dielectric walls are considered. It is shown that to obtain accurate results for the atom-wall interaction at short separations, one should use the complete tabulated optical data for the complex refractive index of the wall material and the accurate dynamic polarizability of an atom. At relatively large separations in the case of a metal wall, one may use the plasma model dielectric function to describe the dielectric properties of wall material. The obtained results are important for the theoretical interpretation of experiments on quantum reflection and Bose-Einstein condensation.Comment: 5 pages, 1 figure, iopart.cls is used, to appear in J. Phys. A (special issue: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005

Presentación: A educación social como relato histórico de amplas avenidas pedagóxicas e sociais

As primeiras referencias documentadas sobre a Educación Social sitúanse cronoloxicamente nos inicios do século XIX. Dende entón, en converxencia coa crecente relevancia que irán adquirindo as Ciencias Sociais e a súa énfase na consideración da educación como un feito ou unha práctica social, suscitará novas lecturas do quefacer educativo; en particular os que aspiran a dar resposta ás múltiples necesidades que emerxen da vida cotiá, como son a atención á infancia e á mocidade en situación de inadaptación e risco social, a educación das persoas adultas, ou a animación sociocultural. En todo caso, sen que poidan obviarse os importantes avances que se rexistran nas Ciencias da Educación (en particular da Pedagoxía Social), na acción-Intervención social e o Traballo Social. A democratización das sociedades, o auxe das políticas educativas, sociais e culturais, en conxunción co desenvolvemento da formación académica nas Universidades, xunto coa incesante profesionalización destes ámbitos, marcará decisivamente o seu percorrido histórico en Europa e no mundo. Así se reflicte neste monográfico ao salientar o importante recoñecemento que están adquirindo a Pedagoxía Social e a Educación Social no espazo iberoamericano, con alusións explícitas ás realidades galega, española, portuguesa e latinoamericana, focalizando a mirada histórica en catro dimensións principais: a contextual, a teórico-epistemolóxica, a formativa-académica e a profesional.info:eu-repo/semantics/publishedVersio

Crisis miasténica generalizada en un Shih Tzu

La miastenia gravis (MG) es una de las enfermedades neuromusculares más frecuentes en perros. Según su causa puede ser congénita o adquirida, y según su localización puede ser focal o generalizada. Puede afectar a animales de distintas edades, sexos y razas, aunque existen algunas razas con mayor predisposición. Dentro de los tipos de presentación clínica de las MG adquiridas, está la denominada Miastenia fulminante o Crisis miasténica, cuya frecuencia de aparición es menor, pero de mayor gravedad al poder afectar a los músculos intercostales y al diafragma, comprometiendo seriamente la capacidad respiratoria del animal. El diagnóstico precoz para establecer el tratamiento adecuado es primordial para intentar estabilizar al animal y tratar de recuperar su función motora. En este artículo presentamos un caso de crisis miasténica en un Shih Tzu macho joven, sin enfermedades tumorales o paraneoplásicas reconocidas, y cuyo origen desencadenante de la respuesta inmunomediada no fue posible dilucidar. Un diagnóstico presuntivo precoz mediante pruebas de electrodiagnóstico y su confirmación posterior tras la detección de anticuerpos circulantes contra los receptores de acetilcolina mediante radioinmunoanálisis, permitieron una mejoría más rápida al establecer un diagnóstico temprano y la instauración urgente de una terapia adecuad

A theory of Plasma Membrane Calcium Pump stimulation and activity

The ATP-driven Plasma Membrane Calcium pump or Ca(2+)-ATPase (PMCA) is characterized by a high affinity to calcium and a low transport rate compared to other transmembrane calcium transport proteins. It plays a crucial role for calcium extrusion from cells. Calmodulin is an intracellular calcium buffering protein which is capable in its Ca(2+) liganded form of stimulating the PMCA by increasing both the affinity to calcium and the maximum calcium transport rate. We introduce a new model of this stimulation process and derive analytical expressions for experimental observables in order to determine the model parameters on the basis of specific experiments. We furthermore develop a model for the pumping activity. The pumping description resolves the seeming contradiction of the Ca(2+):ATP stoichiometry of 1:1 during a translocation step and the observation that the pump binds two calcium ions at the intracellular site. The combination of the calcium pumping and the stimulation model correctly describes PMCA function. We find that the processes of calmodulin-calcium complex attachment to the pump and of stimulation have to be separated. Other PMCA properties are discussed in the framework of the model. The presented model can serve as a tool for calcium dynamics simulations and provides the possibility to characterize different pump isoforms by different type-specific parameter sets.Comment: 24 pages, 6 figure

Composição, abundância e biomasa sazonal da assembleia de peixes no subestuário do Solís Chico (Estuário do Río de la Plata, Uruguay)

The large estuaries can present long narrow branches called subestuaries or tidal creeks. These types of subsystems are distributed along the Uruguayan coast of the Río de la Plata estuary and are very important as nursery and refuge areas for fish. For the first time, the seasonal composition and abundance of the fish community of the Solís Chico subestuary was studied by using beach and gill nets. Fourteen species, mainly euryhaline (86%) presented a significant representation of juvenile stages. The fish community was dominated by Odontesthes argentinensis, Platanichthys platana, Mugil liza, Brevoortia aurea, Micropogonias furnieri and Paralichthys orbignyanus, similar to adjacent subestuaries. While Micropogonias furnieri and B. aurea were the most abundant species, some other species were rarely caught. A seasonal variation of the fish assemblage abundance was detected, with higher values in autumn showing a positive correlation with temperature. Species that complete their life cycle in the Río de la Plata estuary, some of which are relevant to fisheries (64% of the analyzed species) were captured in the Solís Chico subestuary. The importance of this environment as a transitional system for some estuarine fish species is advised

Lateral projection as a possible explanation of the nontrivial boundary dependence of the Casimir force

We find the lateral projection of the Casimir force for a configuration of a sphere above a corrugated plate. This force tends to change the sphere position in the direction of a nearest corrugation maximum. The probability distribution describing different positions of a sphere above a corrugated plate is suggested which is fitted well with experimental data demonstrating the nontrivial boundary dependence of the Casimir force.Comment: 5 pages, 1 figur