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Search Results: 1 - 10 of 191405 matches for " Bimonte D. "
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Isoelectronic determination of the thermal Casimir force
G. Bimonte,D. Lopez,R. S. Decca
Physics , 2015,
Abstract: We report the results of isoelectronic thermal Casimir force measurements between a metal coated sphere and a rotating disk with a periodic distribution of magnetic and non-magnetic metals. The differential force measurement technique considerably reduces the background, allowing to unequivocally rule out a Drude response with magnetic properties taken into account. Results are best modeled with a dielectric plasma response with magnetic properties included. Neither a Drude nor a plasma dielectric response provide a satisfactory description if the magnetic properties are disregarded.
Comparación entre heridas por proyectiles de fuego calibre .22 de baja velocidad y de aire comprimido calibre .177 sobre flanco derecho de cadáveres frescos de conejos (Wounds produces by fire projectils caliber .22 low velocity and air compressed caliber.177 on right side of fresh dead rabbits. a trial study)
Bimonte, D.,Vedovatti, E.,Pacheco, J.,Arredondo, C.
REDVET , 2009,
Abstract: ResumenEl objetivo del trabajo fue comparar, los efectos de proyectiles .177 Airecomprimido (AC), y .22 Rimfire Baja Velocidad (LV) sobre tejidos óseos ymusculares, utilizando n=12 cadáveres frescos de conejos de 3 kilogramosde peso, (Oriyctolagus cuniculus) híbridos Línea Genética Verde divididos endos grupos: (n=6 para .22 Rimfire (LV), peso 2,68 gramos velocidad inicialde 325 m/s y energía inicial 137 Julios y n=6 para .177 AC peso de 0,475gramos, velocidad de 138 m/s y Energía inicial de 4,54Julios).;suspendidos para simular condiciones reales de impacto. El dise oexperimental fue aprobado por Comisión de Bioética, Facultad deVeterinaria, Universidad de la República, Uruguay. Ensayo de penetraciónrealizados en el Club Uruguayo de Tiro. A la necropsia se describieron laslesiones sobre tejidos musculares, huesos y órganos huecos, así como lascaracterísticas de los orificios de entrada (OE) y de salida (OS), para cadatipo de munición y propulsión. Se halló que los disparos producidos pormunición. 22 Rimfire (LV) producían fracturas de huesos largos mientrasque para el calibre .177 (AC) usado no se registraron fracturas. Loshallazgos en órganos viscerales (toráxicos y abdominales) fueron letalespara cualquiera de los dos tipos de munición disparada a 16 m. Solo en elcaso de la munición .177 (AC) se encontraron los proyectiles alojados en pared del flanco opuesto al del ingreso. El proyectil .22 Rimfire (LV) traspasa ambos flancos. Ambos tipos de proyectiles disparados a unadistancia de 16 metros, son capaces de producir lesiones letales.SummaryThe objective of this paper was to make a comparison the effectsproduced by projectiles .177 Air compressed (AC) and .22 Rimfire Lowvelocity (LV) on muscular and osseous tissues, using n=12 recently deadrabbit 3 kilogramos of weight, (Oriyctolagus cuniculus) hybrid Greengenetical line divided in two groups: (n=6 for .22 Rimfire (LV), weight2,68 grams, initial velocity 325 m/s y initial energy 137 Joules and n=6for .177 AC weight 0,475 grams, initial velocity 138 m/s and initial energy4,54 Joules).; ,supported for simulation of real impact conditions. Thisexperimentally design was approved by the Bioethical Committee ofVeterinary Faculty. Universidad de la República, Uruguay. Penetration testwere done at Club Uruguayo de Tiro. At necropsy injuries on muscles,osseous tissues, and cavitary organs; and the caracteritics of entranceholes (OE) and exit holes (OS), for each type off ammunition andpropulsión system, were done. There was evidence, that firing with .22Rimfire (LV) ammunition produce long bones fractures, an
Uso de subproductos de obtención de biocombustibles (expeller de girasol) en alimentación
Vedovatti E.,Bimonte D.,Aldrovandi, A.,Cavallero, B.
REDVET , 2009,
Abstract: ResumenEl objetivo fue el de comprobar ganancia de pesos en conejos alimentados con expeller de girasol, sub producto de la obtención debiocombustibles comparado con otras dietas. Se utilizaron 30 conejosmachos de un mes de edad, entre 1,2 y 1,3 kg Línea Genética Verde, y se dividió en 5 grupos de 6 conejos cada uno: Grupo 0 (Expeller de girasol al 100%); Grupo 1 (Verduras y Frutas con un 25 % de Expeller de Girasol),; Grupo 2 (Frutas y verduras 100%); Grupo 3 (Ración comercial con un 25% de Expeller de Girasol); Grupo 4 (Ración comercial al 100%). Fueron alimentados durante 6 semanas, hasta que el cual el Grupo 4 alcanzó el peso de faena (2,5 kg.) Se registraron los pesos semanalmente, y compararon los pesos vivos previo a la faena, mediante análisis de varianza (ANOVA), el cuál determinó diferencias significativas entre los tratamientos (p<0,0005). Los grupos 1, 3 y 4 se diferenciaron de los grupos 0 y 2. Pero entre los grupos 0 y 1, se encontró un punto de contacto entre los mismos usando Test de Tukey para comparaciones pareadas (p≤0,0005). Los restos de frutas y verduras y el expeller de girasol, suministrados por si solos, no aportan los nutrientes necesarios para llegar a los pesos de finales a la faena. El uso del expeller de girasol (residuo obtención de biocombustibles), no produjo muertes ni trastornos digestivos en el presente estudio y puede suministrarse solo o combinado con otras fuentes, para la alimentación de conejos.
Inverse Symmetry Breaking on the lattice: an accurate MC study
G. Bimonte,D. Iniguez,A. Tarancon,C. L. Ullod
Physics , 1999, DOI: 10.1016/S0550-3213(99)00421-6
Abstract: We present here a new MC study of ISB at finite temperature in a $Z_2\times Z_2$ $\lambda\phi^4$ model in four dimensions. The results of our simulations, even if not conclusive, are favourable to ISB. Detection of the effect required measuring some critical couplings with six-digits precision, a level of accuracy that could be achieved only by a careful use of FSS techniques. The gap equations for the Debye masses, resulting from the resummation of the ring diagrams, seem to provide a qualitatively correct description of the data, while the simple one-loop formulae appear to be inadequate.
The thermal Casimir effect for conducting plates and the Bohr-van Leeuwen theorem
Giuseppe Bimonte
Physics , 2009,
Abstract: We examine recent prescriptions for estimating the thermal Casimir force between two metallic plates from the point of view of their consistency with the Bohr-van Leeuwen theorem of classical statistical physics. We find that prescriptions including the effect of ohmic dissipation satisfy the theorem, while prescriptions that neglect ohmic dissipation do not.
A generalized Kramers-Kronig transform for Casimir effect computations
Giuseppe Bimonte
Physics , 2010, DOI: 10.1103/PhysRevA.81.062501
Abstract: Recent advances in experimental techniques now permit to measure the Casimir force with unprecedented precision. In order to achieve a comparable precision in the theoretical prediction of the force, it is necessary to accurately determine the electric permittivity of the materials constituting the plates along the imaginary frequency axis. The latter quantity is not directly accessible to experiments, but it can be determined via dispersion relations from experimental optical data. In the experimentally important case of conductors, however, a serious drawback of the standard dispersion relations commonly used for this purpose, is their strong dependence on the chosen low-frequency extrapolation of the experimental optical data, which introduces a significant and not easily controllable uncertainty in the result. In this paper we show that a simple modification of the standard dispersion relations, involving suitable analytic window functions, resolves this difficulty, making it possible to reliably determine the electric permittivity at imaginary frequencies solely using experimental optical data in the frequency interval where they are available, without any need of uncontrolled data extrapolations.
Commutation relations for the electromagnetic field in the presence of dielectrics and conductors
Giuseppe Bimonte
Physics , 2009, DOI: 10.1088/1751-8113/43/15/155402
Abstract: We determine the commutation relations satisfied by the quantized electromagnetic field in the presence of macroscopic dielectrics and conductors, with arbitrary dispersive and dissipative properties. We consider in detail the case of two plane-parallel material slabs, separated by an empty gap, and we show that at all points in the empty region between the slabs, including their surfaces, the electromagnetic fields always satisfy free-field canonical equal-time commutation relations. This result is a consequence of general analyticity and fall-off properties at large frequencies satisfied by the reflection coefficients of all real materials. It is also shown that this result does not obtain in the case of conductors, if the latter are modelled as perfect mirrors. In such a case, the free-field form of the commutation relations is recovered only at large distances from the mirrors, in agreement with the findings of previous authors. Failure of perfect-mirror boundary conditions to reproduce the correct form of the commutation relations near the surfaces of the conductors, suggests that caution should be used when these idealized boundary conditions are used in investigations of proximity phenomena originating from the quantized electromagnetic field, like the Casimir effect.
Johnson noise and the thermal Casimir effect
Giuseppe Bimonte
Physics , 2007, DOI: 10.1088/1367-2630/9/8/281
Abstract: We study the thermal interaction between two nearby thin metallic wires, at finite temperature. It is shown that the Johnson currents in the wires give rise, via inductive coupling, to a repulsive force between them. This thermal interaction exhibits all the puzzling features found recently in the thermal Casimir effect for lossy metallic plates, suggesting that the physical origin of the difficulties encountered in the Casimir problem resides in the inductive coupling between the Johnson currents inside the plates. We show that in our simple model all puzzles are resolved if account is taken of capacitive effects associated with the end points of the wires. Our findings suggest that capacitive finite-size effects may play an important role in the resolution of the analogous problems met in the thermal Casimir effect.
The thermal Casimir effect for rough metallic plates
G. Bimonte
Physics , 2007,
Abstract: We propose a new theory of thermal Casimir effect, holding for the experimentally important case of metallic surfaces with a roughness having a spatial scale smaller than the skin depth. The theory is based on a simple phenomenological model for a rough conductor, that explicitly takes account of the fact that ohmic conduction in the immediate vicinity of the surface of a conductor is much impeded by surface roughness, if the amplitude of roughness is smaller than the skin depth. As a result of the new model, we find that surface roughness strongly influences the magnitude of the thermal correction to the Casimir force, independently of the plates separation. Our model, while consistent with recent accurate measurements of the Casimir force in the submicron range, leads to a new prediction for the not yet observed thermal correction to the Casimir force at large plates separation. Besides the thermal Casimir problem, our model is relevant for the correct theoretical interpretation of current experiments probing other proximity effects between conductors, like radiative heat transfer and quantum friction.
Casimir effect in a superconducting cavity and the thermal controversy
Giuseppe Bimonte
Physics , 2008, DOI: 10.1103/PhysRevA.78.062101
Abstract: One of the most important and still unresolved problems in the field of dispersion forces, is that of determining the influence of temperature on the Casimir force between two metallic plates. While alternative theoretical approaches lead to contradictory predictions for the magnitude of the effect, no experiment has yet detected the thermal correction to the Casimir force. In this paper we show that a superconducting cavity provides a new opportunity to investigate the problem of the thermal dependence of the Casimir force in real materials, by looking at the change of the Casimir force determined by a small change of temperature. The actual feasibility of the proposed scheme is briefly discussed.
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