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Search Results: 1 - 10 of 6343 matches for " Raul Cesar; "
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Unbiased diffusion of Brownian particles on disordered correlated potentials
Raul Salgado-Garcia,Cesar Maldonado
Physics , 2015,
Abstract: In this work we study the diffusion of non-interacting overdamped particles, moving on unbiased disordered correlated potentials, subjected to Gaussian white noise. We obtain an exact expression for the diffusion coefficient which allows us to prove that the unbiased diffusion of overdamped particles on a random polymer does not depend on the correlations of the disordered potentials. This universal behavior of the unbiased diffusivity is a direct consequence of the validity of the Einstein relation and the decay of correlations of the random polymer. We test the independence on correlations of the diffusion coefficient for correlated polymers produced by two different stochastic processes, a one-step Markov chain and the expansion-modification system. Within the accuracy of our simulations, we found that the numerically obtained diffusion coefficient for these systems agree with the analytically calculated ones, confirming our predictions.
Markov Approximations of Gibbs measures for long-range potentials on 1D lattices
Cesar Maldonado,Raul Salgado-Garcia
Physics , 2013, DOI: 10.1088/1742-5468/2013/08/P08012
Abstract: We study one-dimensional lattice systems with pair-wise interactions of in?nite range. We show projective convergence of Markov measures to the unique equilibrium state. For this purpose we impose a slightly stronger condition than summability of variations on the regularity of the interaction. With our condition we are able to explicitly obtain stretched exponential bounds for the rate of mixing of the equilibrium state. Finally we show convergence for the entropy of the Markov measures to that of the equilibrium state via the convergence of their topological pressure.
Efectos de la roturación del suelo y fertilización con fósforo en el crecimiento inicial de plantaciones de Pinus taeda, en suelos rojos del Noreste de la provincia de Corrientes, Argentina
IBA?EZ,CESAR; NU?EZ,PATRICIO; PEZZUTTI,RAUL; RODRIGUEZ,FRANCISCO;
Bosque (Valdivia) , 2004, DOI: 10.4067/S0717-92002004000200007
Abstract: growth response of a two-year-old pinus taeda l. (loblolly pine) plantation is evaluated for differing soil preparation and phosphorus fertilization regimes. the study was of first and second rotation sites on the díaz de vivar soil series, kandihumults subgroup of the ultisols order, corrientes province, argentina. a divided plot design was used in each trial, using a factorial experiment of 3 x 2 with three replicates. treatment was: plowing; 50 and 80 cm ripping plus plowing, combined with 0 and 120 g/plant of triple super phosphate (0 - 46 - 0). on first rotation sites, higher responses resulted from 50 and 80 cm ripping showing a large difference compared with plowed-only areas. at second rotation sites, no significant distinction was seen between soil preparation methods. for both site types, the application of phosphorus had a significant positive effect on growth.
Development and Characterization of Cefoxitin Loaded D,L-PLA Nanoparticles
Sílvia Regina Pengo Machado,Raul Cesar Evangelista
Revista de Ciências Farmacêuticas Básica e Aplicada , 2010,
Abstract: Nanoparticles containing cefoxitin (CEF) made of D,L-PLA (PLA) were designed by a multiple emulsion/solvent evaporation method. The particles were extensively evaluated in relation to morphology, encapsulation efficiency, drug-polymer interactions as well as in vitro drug release kinetics. Nanoparticles were spherical in shape and isolated, with a mean diameter of about 600 nm. The thermal behaviour (DSC) of CEF-containing nanoparticles suggested that the drug was dispersed at a molecular level within the system. The drug encapsulation efficiency in the system for a CEF concentration of 30 mg/mL was 5.5%, as assessed after the drug extraction, by a validated HPLC method. This low encapsulation efficiency is understandable, since CEF is highly hydrophilic. The in vitro assays showed a strong sustained drug release profile from the nanoparticles with kinetics following pure Fickian diffusion. Keywords: Nanoparticles. Controlled release. D,L-PLA. Cefoxitin. In vitro release. RESUMO Desenvolvimento e Caracteriza o de Nanopartículas de D,L-PLA contendo Cefoxitina As nanopartículas de D, L-PLA (PLA) contendo cefoxitina (CEF) foram preparadas pelo método de emuls o múltipla / evapora o do solvente. As partículas foram avaliadas em rela o à morfologia, à eficiência de encapsula o, às intera es polímero-fármaco, bem como à cinética de libera o do fármaco in vitro . As nanopartículas s o esféricas e isoladas, com um diametro médio de cerca de 600 nm. O comportamento térmico (DSC) das nanopartículas contendo CEF sugeriu que o fármaco está disperso em um nível molecular dentro do sistema. A eficiência de encapsula o do fármaco no sistema quando a concentra o de CEF é 30 mg / mL foi de 5,5%, determinada após a extra o de fármaco, através de um método de HPLC validado. Esta baixa eficiência de encapsula o é compreensível, uma vez que a CEF é altamente hidrofílica. Os ensaios in vitro mostraram um perfil de libera o do fármaco a partir das nanopartículas fortemente sustentado e com uma cinética de difus o Fickiana pura. Palavras-chave: Nanopartículas. Libera o controlada. D,L-PLA. Cefoxitina. Libera o In vitro.
Efectos de la roturación del suelo y fertilización con fósforo en el crecimiento inicial de plantaciones de Pinus taeda, en suelos rojos del Noreste de la provincia de Corrientes, Argentina Soil ripping and phosphorus fertilization effects on Pinus taeda initial growth in red soils of Northeast Corrientes Province, Argentina
CESAR IBA?EZ,PATRICIO NU?EZ,RAUL PEZZUTTI,FRANCISCO RODRIGUEZ
Bosque (Valdivia) , 2004,
Abstract: Se evalúa la respuesta del crecimiento de una plantación de Pinus taeda L. de dos a os, bajo diferentes modalidades de roturación de suelos y fertilización con fósforo en terrenos de primera y segunda rotación de la serie Díaz de Vivar, pertenecientes al subgrupo de los Kandihumultes típicos del orden Ultisoles, del Noreste de la provincia de Corrientes, Argentina. El dise o utilizado en cada ensayo corresponde a parcelas divididas en un experimento factorial de 3 x 2 con tres repeticiones. Los tratamientos corresponden a la aplicación de rastra, subsolado a 50 y 80 cm de profundidad más rastra, combinados con 0 y 120 g pl-1 de superfosfato triple (0 - 46 - 0). Para el sector de primera rotación los mejores crecimientos se logran subsolando a 50 y 80 cm de profundidad, diferenciándose significativamente de las áreas preparadas sólo con rastra. En cambio, para el área de segunda rotación no se observan diferencias significativas entre los métodos de roturación de suelo. En ambos ensayos la aplicación de fósforo tuvo un efecto positivo y significativo sobre el crecimiento. Growth response of a two-year-old Pinus taeda L. (loblolly pine) plantation is evaluated for differing soil preparation and phosphorus fertilization regimes. The study was of first and second rotation sites on the Díaz de Vivar soil series, Kandihumults subgroup of the ultisols order, Corrientes Province, Argentina. A divided plot design was used in each trial, using a factorial experiment of 3 x 2 with three replicates. Treatment was: plowing; 50 and 80 cm ripping plus plowing, combined with 0 and 120 g/plant of triple super phosphate (0 - 46 - 0). On first rotation sites, higher responses resulted from 50 and 80 cm ripping showing a large difference compared with plowed-only areas. At second rotation sites, no significant distinction was seen between soil preparation methods. For both site types, the application of phosphorus had a significant positive effect on growth.
Minimal Inflation
Luis Alvarez-Gaume,Cesar Gomez,Raul Jimenez
Physics , 2009, DOI: 10.1016/j.physletb.2010.04.069
Abstract: Using the universal X superfield that measures in the UV the violation of conformal invariance we build up a model of multifield inflation. The underlying dynamics is the one controlling the natural flow of this field in the IR to the Goldstino superfield once SUSY is broken. We show that flat directions satisfying the slow roll conditions exist only if R-symmetry is broken. Naturalness of our model leads to scales of SUSY breaking of the order of 10^{11-13} Gev, a nearly scale-invariant spectrum of the initial perturbations and negligible gravitational waves. We obtain that the inflaton field is lighter than the gravitino by an amount determined by the slow roll parameter eta. The existence of slow-roll conditions is directly linked to the values of supersymmetry and R-symmetry breaking scales. We make cosmological predictions of our model and compare them to current data.
Phenomenology of the minimal inflation scenario: inflationary trajectories and particle production
Luis Alvarez-Gaume,Cesar Gomez,Raul Jimenez
Physics , 2011, DOI: 10.1088/1475-7516/2012/03/017
Abstract: We discuss the phenomenology of the minimal inflation scenario. We concentrate on two aspects: inflationary trajectories and particle production. Our findings can be summarized in two main results: first, that inflationary trayectories that are very flat and provide enough number of e-foldings are natural in the scenario without fine tunning. We present a general formalism to identify attractors in multi-field inflation regardless of trajectories fulfilling the slow-roll conditions. We then explore particle production in the model and show how the inflaton naturally transmutes into a dark matter particle. One interesting feature of our model is that it provides a novel mechanism to generate particles and entropy in the universe: the filling of the Fermi sphere up to a given momentum p_F due to the sea of goldstinos that are an important part of the matter generated after inflation. With this mechanism in hand we predict that the gravitino should have a mass of > 100-1000 TeV. Another interesting feature of our model is that the predicted level of gravity waves is r=0.1 - 0.001, which is in the range of detectability from Planck and upcoming CMB polarization experiments.
A Minimal Inflation Scenario
Luis Alvarez-Gaume,Cesar Gomez,Raul Jimenez
Physics , 2011, DOI: 10.1088/1475-7516/2011/03/027
Abstract: We elaborate on a minimal inflation scenario based entirely on the general properties of supersymmetry breaking in supergravity models. We identify the inflaton as the scalar component of the Goldstino superfield. We write plausible candidates for the effective action describing this chiral superfield. In particular the theory depends (apart from parameters of O(1)) on a single free parameter: the scale of supersymmetry breaking. This can be fixed using the amplitude of CMB cosmological perturbations and we therefore obtain the scale of supersymmetry breaking to be 10^{12-14} GeV. The model also incorporates explicit R-symmetry breaking in order to satisfy the slow roll conditions. In our model the eta-problem is solved without extra fine-tuning. We try to obtain as much information as possible in a model independent way using general symmetry properties of the theory's effective action, this leads to a new proposal on how to exit the inflationary phase and reheat the Universe.
Initial conditions for inflation and the energy scale of SUSY-breaking from the (nearly) gaussian sky
Luis Alvarez-Gaume,Cesar Gomez,Raul Jimenez
Physics , 2013, DOI: 10.1063/1.4891111
Abstract: We show how general initial conditions for small field inflation can be obtained in multi-field models. This is provided by non-linear angular friction terms in the inflaton that provide a phase of non-slow-roll inflation before the slow-roll inflation phase. This in turn provides a natural mechanism to star small-field slow-roll at nearly zero velocity for arbitrary initial conditions. We also show that there is a relation between the scale of SUSY breaking sqrt (f) and the amount of non-gaussian fluctuations generated by the inflaton. In particular, we show that in the local non-gaussian shape there exists the relation sqrt (f) = 10^{13} GeV sqrt (f_NL). With current observational limits from Planck, and adopting the minimum amount of non-gaussian fluctuations allowed by single-field inflation, this provides a very tight constraint for the SUSY breaking energy scale sqrt (f) = 3-7 x 10^{13} GeV at 95% confidence. Further limits, or detection, from next year's Planck polarisation data will further tighten this constraint by a factor of two. We highlight that the key to our approach is to identify the inflaton with the scalar component of the goldstino superfield. This superfield is universal and implements the dynamics of SUSY breaking as well as superconformal breaking.
Semisimple Group (and Loop) Algebras over Finite Fields
Raul A. Ferraz,Edgar G. Goodaire,Cesar Polcino Milies
Mathematics , 2009,
Abstract: We determine the structure of the semisimple group algebra of certain groups over the rationals and over those finite fields where the Wedderburn decompositions have the least number of simple components. We apply our work to obtain similar information about the loop algebras of indecomposable RA loops and to produce negative answers to the isomorphism problem over various fields.
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