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Search Results: 1 - 10 of 302891 matches for " Oscar J; "
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The Nuclear Imperative in Russia’s Security Strategy
J. Oscar Alvarez Calzada
Revista CIDOB d'Afers Internacionals , 2005,
Abstract: The process which culminated in the disappearance of the USSR was heavily influenced by that Soviet Union’s inability to maintain the level of technology reached by the US in the arms race. Under the circumstances of deteriorating Russian power which have been developing since 1991, and given the precariousness that affects its armed forces, nuclear weapons have become the core element of the Russian Federation’s national security strategy. This article explores the causes that have led to this nuclear imperative in Russia’s security strategy; and secondly, it presents the most relevant, and worrying, consequence that this dependence has generated, which is the lowering of the threshold necessary forthe use of nuclear weapons.
Drawing the Caspian Sea: The defining of its legal status in the uncertain post-soviet scenario
J. Oscar álvarez Calzada
Revista CIDOB d'Afers Internacionals , 2003,
Abstract: With the disappearance of the USSR, the Caspian Sea ceased to be an inland sea controlled by the USSR and Iran, to become the object of desire of the new states bordering on it which see in it, and concretely in its extraordinary natural resources, the great hope ofeconomic salvation for their uncertatin future. If we add to this the interests of the great regional actors, Russia and Iran, and those of the United States and the large multinational energy corporations, we get one of the post-Soviet scenarios that arouses the most interestin international public opinion. In this context, the article analyses the unstable situation created in the area in the face of the impossibility of the states bordering on this sea to arrive at a unanimous agreement on the method to follow for dividing up its waters and, therefore, to settle the question of access to the vast natural resources that lie beneath its floor.
Dise o razonado de muestras y captación de datos para la investigación sanitaria
Mujica Oscar J.
Revista Panamericana de Salud Pública , 2001,
Bounds on Scalar Leptoquarks from the LEP Data
Oscar J. P. Eboli
Physics , 1995,
Abstract: We obtain the constraints on scalar leptoquarks coming from radiative corrections to $Z$ physics. We perform a global fitting to the LEP data including the contributions of the most general effective Lagrangian for scalar leptoquarks, which exhibits the $SU(2)_L \times U(1)_Y$ gauge invariance. Our bounds on leptoquarks that couple to the top quark are much stronger than the ones obtained from low energy experiments.
Superradiant instability of large radius doubly spinning black rings
Oscar J. C. Dias
Physics , 2006, DOI: 10.1103/PhysRevD.73.124035
Abstract: We point out that 5D large radius doubly spinning black rings with rotation along S^1 and S^2 are afflicted by a robust instability. It is triggered by superradiant bound state modes. The Kaluza-Klein momentum of the mode along the ring is responsible for the bound state. This kind of instability in black strings and branes was first suggested by Marolf and Palmer and studied in detail by Cardoso, Lemos and Yoshida. We find the frequency spectrum and timescale of this instability in the black ring background, and show that it is active for large radius rings with large rotation along S^2. We identify the endpoint of the instability and argue that it provides a dynamical mechanism that introduces an upper bound in the rotation of the black ring. To estimate the upper bound, we use the recent black ring model of Hovdebo and Myers, with a minor extension to accommodate an extra small angular momentum. This dynamical bound can be smaller than the Kerr-like bound imposed by regularity at the horizon. Recently, the existence of higher dimensional black rings is being conjectured. They will be stable against this mechanism.
Pair creation of particles and black holes in external fields
Oscar J. C. Dias
Physics , 2001,
Abstract: It is well known that massive black holes may form through the gravitational collapse of a massive astrophysical body. Less known is the fact that a black hole can be produced by the quantum process of pair creation in external fields. These black holes may have a mass much lower than their astrophysical counterparts. This mass can be of the order of Planck mass so that quantum effects may be important. This pair creation process can be investigated semiclassically using non-perturbative instanton methods, thus it may be used as a theoretical laboratory to obtain clues for a quantum gravity theory. In this work, we review briefly the history of pair creation of particles and black holes in external fields. In order to present some features of the euclidean instanton method which is used to calculate pair creation rates, we study a simple model of a scalar field and propose an effective one-loop action for a two-dimensional soliton pair creation problem. This action is built from the soliton field itself and the soliton charge is no longer treated as a topological charge but as a Noether charge. The results are also valid straightforwardly to the problem of pair creation rate of domain walls in dimensions greater than 2.
Pair creation of anti-de Sitter black holes on a cosmic string background
Oscar J. C. Dias
Physics , 2004, DOI: 10.1103/PhysRevD.70.024007
Abstract: We analyze the quantum process in which a cosmic string breaks in an anti-de Sitter (AdS) background, and a pair of charged or neutral black holes is produced at the ends of the strings. The energy to materialize and accelerate the pair comes from the strings tension. In an AdS background this is the only study done in the process of production of a pair of correlated black holes with spherical topology. The acceleration $A$ of the produced black holes is necessarily greater than (|L|/3)^(1/2), where L<0 is the cosmological constant. Only in this case the virtual pair of black holes can overcome the attractive background AdS potential well and become real. The instantons that describe this process are constructed through the analytical continuation of the AdS C-metric. Then, we explicitly compute the pair creation rate of the process, and we verify that (as occurs with pair creation in other backgrounds) the pair production of nonextreme black holes is enhanced relative to the pair creation of extreme black holes by a factor of exp(Area/4), where Area is the black hole horizon area. We also conclude that the general behavior of the pair creation rate with the mass and acceleration of the black holes is similar in the AdS, flat and de Sitter cases, and our AdS results reduce to the ones of the flat case when L=0.
Cambios dinámicos y mecánicos de una mezcla asfáltica densa por las propiedades del asfalto y la energía de compactación
Reyes-Ortiz,Oscar J.;
Ingeniería y Desarrollo , 2009,
Abstract: the objective of this study was to evaluate the influence of three types of asphalt with different characteristics (60/70 of penetration, 85/100 of penetration and polymer modified asphalt) and compaction energy in the mechanical and dynamic changes of the dense asphalt mixture, used as a rolling layer by specifications idu. the ideal asphalt content was determined by the marshall. the mechanics and dynamic characterization of the mixture, was realized with diametral compression tests at 15 ° c, rutting with 900 mpa and 60° c, resilient modulus with 15, 20 and 30 °c, 5 hz frequency and the cohesion curve through the characterization universal binders (ucl) test with 0, 10, 20, 30 and 40° c. the study found that the results show that the mixture prepared with asphalt 60/70 presents highter resilient modulus value at temperatures studied and the mixture manufactured with modified asphalt has rutting lower than conventional asphalt. finally, resistance to traction and indirect cohesion curve state is best for the modified asphalt
Studying and simulating transformer configuration to improve power quality
Pe?a Huaringa,Oscar J.;
Ingeniería e Investigación , 2011,
Abstract: this paper presents a study and simulation of transformer configurations to improve power quality; it provides theoretical support based on the expansion of the fourier series and analysis of symmetrical components. a test system was set up in the laboratory, taking measurements and checking configuration effectiveness in reducing the system's harmonic content. the configurations were modelled with pscad / emtdc software, using two 6 pulse rectifiers as test loads and two variable speed drives.
Análisis de enzimos pancreáticos en lactantes y ni os peque os
Revista chilena de pediatría , 1948,
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