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Search Results: 1 - 10 of 596125 matches for " María L Vranic "
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Desarrollo de un Sellador Post-Orde o con Goma Espina Corona Development of a Post-Milking Sealant with Espina Corona Gum
Rosa S Ríos,Nelsi A Ramos,María L Vranic,María E Farías
Información Tecnológica , 2013,
Abstract: Con la finalidad de evitar infecciones por mastitis en el ganado vacuno, es recomendable utilizar sellador de pezones post orde o. El objetivo del trabajo fue desarrollar un sellador post orde o antiséptico y con estabilidad fisicoquímica, para evitar pérdidas del producto por escurrimiento. El sellador se formuló con la goma espina corona, que cumple la función de incrementar la viscosidad del producto. Se aplicó el dise o central compuesto rotable para obtener la formulación óptima. Se evaluó la viscosidad aparente, como variable de respuesta con un viscosímetro Brookfield DVII+LV2. Se determinó la fórmula óptima: espina corona (1,7%), agua desmineralizada (88.60%), glicerina (4,70%), solución de yodo y tensioactivo (3,00%) y solución buffer pH=5±0.3 (2,00%). El sellador mostró un comportamiento reológico del tipo pseudoplástico. Se concluye que la goma espina corona es apta para formular un sellador post orde o, tiene estabilidad fisicoquímica adecuada y mantiene su principio activo como bactericida. To prevent infection by mastitis in cattle, it is advisable to use post milking teat dip. The objective of this study was to develop a post milking antiseptic sealant with physicochemical stability, to avoid product losses by leakage. The sealant was formulated with the espina corona gum, which increases the viscosity of the product. A central composite rotatable design was applied to obtain the optimal formulation. The apparent viscosity was evaluated as the response variable with a Brookfield DVII + LV2. The optimal formula was determined as: espina corona gum (1.7%), dematerialized water (88.60%), glycerin (4.70%), iodine solution and surfactant (3.00%) and buffer solution pH = 5±0.3 (2.00%). The sealant showed a rheological behavior of the pseudoplastic type. It is concluded that the espina corona gum is suitable to formulate a post milking sealant with acceptable physicochemical stability and that also keeps its active principle as a bactericide.
Modelling radiation emission in the transition from the classical to the quantum regime
J. L. Martins,M. Vranic,T. Grismayer,J. Vieira,R. A. Fonseca,L. O. Silva
Physics , 2015, DOI: 10.1088/0741-3335/58/1/014035
Abstract: An emissivity formula is derived using the generalised Fermi-Weizacker-Williams method of virtual photons which accounts for the recoil the charged particle experiences as it emits radiation. It is found that through this derivation the formula obtained by Sokolov et al using QED perturbation theory is recovered. The corrected emissivity formula is applied to nonlinear Thomson scattering scenarios in the transition from the classical to the quantum regime, for small values of the nonlinear quantum parameter \chi. Good agreement is found between this method and a QED probabilistic approach for scenarios where both are valid. In addition, signatures of the quantum corrections are identified and explored.
Classical Radiation Reaction in Particle-In-Cell Simulations
Marija Vranic,Joana L. Martins,Ricardo A. Fonseca,Luis O. Silva
Physics , 2015,
Abstract: Under the presence of ultra high intensity lasers or other intense electromagnetic fields the motion of particles in the ultrarelativistic regime can be severely affected by radiation reaction. The standard particle-in-cell (PIC) algorithms do not include radiation reaction effects. Even though this is a well known mechanism, there is not yet a definite algorithm nor a standard technique to include radiation reaction in PIC codes. We have compared several models for the calculation of the radiation reaction force, with the goal of implementing an algorithm for classical radiation reaction in the Osiris framework, a state-of-the-art PIC code. The results of the different models are compared with standard analytical results, and the relevance/advantages of each model are discussed. Numerical issues relevant to PIC codes such as resolution requirements, application of radiation reaction to macro particles and computational cost are also addressed. The Landau and Lifshitz reduced model is chosen for implementation.
Laser absorption via QED cascades in counter propagating laser pulses
Thomas Grismayer,Marija Vranic,Joana L. Martins,Ricardo A. Fonseca,Luis O. Silva
Physics , 2015,
Abstract: A model for laser light absorption in electron-positron plasmas self-consistently created via QED cascades is described. The laser energy is mainly absorbed due to hard photon emission via nonlinear Compton scattering. The degree of absorption depends on the laser intensity and the pulse duration. The QED cascades are studied with multi-dimensional particle-in-cell simulations complemented by a QED module and a macro-particle merging algorithm that allows to handle the exponential growth of the number of particles. Results range from moderate-intensity regimes ($\sim$ 10 PW) where the laser absorption is negligible, to extreme intensities (> 100 PW) where the degree of absorption reaches 80%. Our study demonstrates good agreement between the analytical model and simulations. The expected properties of the hard photon emission and the generated pair-plasma are investigated, and the experimental signatures for near-future laser facilities are discussed.
Full-scale ab initio 3D PIC simulations of an all-optical radiation reaction configuration at $10^{21}\mathrm{W/cm^2}$
Marija Vranic,Joana L. Martins,Jorge Vieira,Ricardo A. Fonseca,Luis O. Silva
Physics , 2013, DOI: 10.1103/PhysRevLett.113.134801
Abstract: Using full-scale 3D particle-in-cell simulations we show that the radiation reaction dominated regime can be reached in an all optical configuration through the collision of a $\sim$1 GeV laser wakefield accelerated (LWFA) electron bunch with a counter propagating laser pulse. In this configuration radiation reaction significantly reduces the energy of the particle bunch, thus providing clear experimental signatures for the process with currently available lasers. We also show that the transition between classical and quantum radiation reaction could be investigated in the same configuration with laser intensities of $10^{24}\mathrm{W/cm^2}$.
Particle Merging Algorithm for PIC Codes
Marija Vranic,Thomas Grismayer,Joana L. Martins,Ricardo A. Fonseca,Luis O. Silva
Physics , 2014, DOI: 10.1016/j.cpc.2015.01.020
Abstract: Particle-in-cell merging algorithms aim to resample dynamically the six-dimensional phase space occupied by particles without distorting substantially the physical description of the system. Whereas various approaches have been proposed in previous works, none of them seemed to be able to conserve fully charge, momentum, energy and their associated distributions. We describe here an alternative algorithm based on the coalescence of N massive or massless particles, considered to be close enough in phase space, into two new macro-particles. The local conservation of charge, momentum and energy are ensured by the resolution of a system of scalar equations. Various simulation comparisons have been carried out with and without the merging algorithm, from classical plasma physics problems to extreme scenarios where quantum electrodynamics is taken into account, showing in addition to the conservation of local quantities, the good reproducibility of the particle distributions. In case where the number of particles ought to increase exponentially in the simulation box, the dynamical merging permits a considerable speedup, and significant memory savings that otherwise would make the simulations impossible to perform.
Length-mass relationships for macroinvertebrates in freshwater environments of Patagonia (Argentina)
Miserendino,María L;
Ecolog?-a austral , 2001,
Abstract: mass-length equations were obtained for aquatic macroinvertebrates collected in different streams and rivers of patagonia, argentina. thirty six taxa were studied: plecoptera (10 species), ephemeroptera (3 species, 3 genera), trichoptera (4 species, 1 genus), diptera (6 genera), coleoptera (1 species, 1 genus) anisoptera (1 genus), crustacea (2 species), oligochaeta (1 genus, 1 family), gasteropoda (1 species) and turbellaria (1 genus). additional relationships were obtained at the order level for plecoptera, ephemeroptera, trichoptera and diptera. mass-length relationships were estimated by fitting the model y = axb linearized by logarithmic transformation) to data of dry mass vs. body length of preserved specimens. the regressions were highly significant and explained a high proportion of variation of the dependent variable, as expressed by the coefficient of determination (r2 = 0.58-0.98). the equations obtained allow the estimation of biomass of invertebrates in patagonian running waters from measurements of linear dimensions, facilitating calculations of benthic standing crop and of secondary production.
Vida cotidiana, ciudadanía y el género de la política
Lagos,María L.;
Cuadernos de antropolog?-a social , 2008,
Abstract: this essay discusses gender relations in rural cochabamba, bolivia, from a perspective that takes into account the material and cultural aspects of production, politics, and the state. it focuses on the tensions that the conflicting demands of livelihood generate within households and villages, in order to describe how women and men deal with them as gendered subjects. it also examines the role of the state in defining social categories and in prescribing gendered spheres of public and private practices, and analyzes how these prescriptions interplay with entrenched unequal gender relations and ideologies in shaping the gender of politics.
Phytochemical profile of the stems of Aeonium lindleyi
Kennedy, María L.;
Revista Brasileira de Farmacognosia , 2012, DOI: 10.1590/S0102-695X2012005000037
Abstract: aeonium species are plants rich in phenols and terpenoids and have been widely used in the canary folk medicine. following our project concerning bioactive compounds from macaronesian region, a phytochemical study was carried out to investigate the constituents of the stems of aeonium lindleyi webb & berthel.,crassulaceae. air dried and chopped stems of this plant were extracted with ethanol in a soxhlet apparatus and the total extract was chromatographed on silica gel to afford sixteen known compounds including, one sterol, four lupane triterpenes and eleven phenolic compounds. their structures were elucidated by means of 1h- and 13c-nmr spectroscopic studies and comparison of their spectral data with values in the literature. both group of isolated metabolites are known by their diverse biological activities and they have been described as antioxidant, cytotoxic, anti-inflammatory. our results contribute to the knowledge of a. lindleyi as a potential source of bioactive compounds.
Los imaginarios en la construcción de la identidad latinoamericana
No?l Lapoujade,María;
Revista de Filosofía , 2004,
Abstract: this article examines the many contributions of an imaginary in the construction of latinamerican identity elaborated since the discovery of america to present contemporary society. the category of homo imaginans is affirmed as a key to understanding the process of constructing latin american identity.
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