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Search Results: 1 - 10 of 339297 matches for " L. O. Silva "
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Physical problems (microphysics) in relativistic plasma flows
L. O. Silva
Physics , 2006, DOI: 10.1063/1.2356387
Abstract: Many problems in astrophysics involve relativistic outflows. The plasma dynamics in these scenarios is critical to determine the conditions for the self-consistent evolution of the fields and particle acceleration. Advances in computer power now allow for kinetic plasma simulations, based on the particle-in-cell (PIC) paradigm, capable of providing information about the role of plasma instabilities in relativistic outflows. A discussion of the key issues associated with PIC simulations is presented, along with some the most important results and open questions, with a particular emphasis on the long time evolution of the filamentation, or Weibel, instability, and on the possible collisionless mechanisms for particle acceleration arising in the collision of relativistic plasma shells.
Synthesis of ZSM-22 in Static and Dynamic System Using Seeds  [PDF]
Lenivaldo V. de Sousa Júnior, Antonio O. S. Silva, Bruno J. B. Silva, Soraya L. Alencar
Modern Research in Catalysis (MRC) , 2014, DOI: 10.4236/mrc.2014.32007

ZSM-22 was synthesized using various sources of silica, organic template 1,6-diaminohexane, under hydrothermal conditions, with and without agitation during crystallization. Subsequently, the crystallized material was used as seeds to accelerate the crystallization process. Characterization of the ZSM-22 samples was performed by XRD, ATG/DTG and FT-IR. It was found that it is possible to synthesize ZSM-22 employing colloidal silica and pyrolytic silica as silicon sources only if the system is stirred during crystallization. The crystallization time for these systems was 13 hours, longer times of crystallization do not significantly increase the crystallinity of the sample. The addition of seeds significantly accelerates the crystallization of ZSM-22, reducing the crystallization time to only 7 hours, with stirring and with systems employing colloidal silica.

Gastric Neoplasia during Anti-TNF Therapy for Crohn’s Disease: Casual Event?  [PDF]
F. M. L. Fortes, B. C. Silva, B. C. Silva, M. C. Lyra, A. M. Pimentel, G. O. Santana
Journal of Cancer Therapy (JCT) , 2015, DOI: 10.4236/jct.2015.68081
Abstract: The increase risk of cancer development in patients with inflammatory intestinal disease (IBD) has already studied for decades. The anti-TNF therapy has changed the treatment strategy of IBD. By using on a larger scale and for a longer time, the anti-TNF raised concern over its potential adverse events. A male Crohn’s disease (CD) patient, 55 years old, diagnosed for nine years, treated with infliximab for 6 years. In 2011, he underwent a nupper endoscopy (UE) which showed flat erosive gastritis with moderate intensity in antrum, gastric polyps and gastric erosion. Pathological examination revealed a chronic gastritis in erosive activity and search for Helicobacter pylori resulted positive. In May 2014, the patient was asymptomatic, when it held UE, which showed suggestive lesion of early gastric cancer, measuring 1.5 cm and search for Helicobacter pylori negative. Histopathological exams confirmed the adenocarcinoma. The patient underwent to a laparoscopic surgery (total gastrectomy with lymphadenectomy and reconstruction Roux-en-Y). Risk factors for the development of gastric cancer in general population are already well defined. However studying a possible association among CD and the different therapeutic modalities used in the treatment of this disease with gastric cancer appearance is important to set specific assessment strategies, prevention and follow-up. While there is no consensus on a proper monitoring for gastric cancer prevention in these patients, individualized conduct, taking into account individual characteristics, family record and other risk factors, should be adopted to avoid unfavorable outcomes in CD patients.
Experimental Design in Solvent Extraction: A Study for Divalent Metals Separation in D2EHPA/Isoparaffin System  [PDF]
Clenilson Da Silva Sousa Junior, Marisa Nascimento, Lídia Yokoyama, Osvaldo Galv?o Caldas Da Cunha
Engineering (ENG) , 2012, DOI: 10.4236/eng.2012.411104
Abstract: The solvent extraction process combined with tools of experimental design assists in developing procedures for separation and purification of elements or mineral compounds with high purity. In this work the technique was used to replace the traditional methods for the collection of basic information required for the development of a circuit of solvent extraction. According to the literature, several factors may influence the extraction of divalent metals by D2EHPA in sulfate media, among which the concentration of metals in solution. The objective was to study the variables affecting the separation process Mn/Ni/Co/Cu, such as the aqueous/organic (A/O), contact time, concentrations of the divalent metals in sulfuric medium, pH and solvent concentration. An investigation into the variables that control the process was done using a “cube + star” experimental design, with central point. The results demonstrate it is possible to obtain of a satisfactory mathematical model that describes the process.
Educa??o profissional e gest?o em saúde: pressupostos teórico-conceituais na forma??o de profissionais de nível médio
Silva, Ana Lúcia Abrah?o da;
Trabalho, Educa??o e Saúde , 2005, DOI: 10.1590/S1981-77462005000200006
Abstract: this article discusses the theoretical and conceptual premises that serve as guidelines for the program of the joaquim venancio polytechnic health school course on professional education on administration of health services. the article simultaneously describes how the administration of health services was assembled, seeking to identify the knowledge required of technicians in administration of health services, and debates the configuration that was designed for professional education since the promulgation of the lei de diretrizes e bases da educa??o (education guidelines and principles act), of 1996. in the end, the article proposes the creation of a sequential course comprised of crossing axes which seek to train independent professionals that comply with the proposed changes, especially those regarding decentralization, regionalization and democratization in health administration.
In search of colonial El Ni o events and a brief history of meteorology in Ecuador
A. O. Cardoso ,P. L. Silva Dias
Advances in Geosciences (ADGEO) , 2006,
Abstract: Several studies indicate that there is a relationship between the climatic variability in the South American continent and alterations of the position and intensity of the heat sources in the equatorial region. The El Ni o phenomenon can influence the precipitation over some regions of South America such as the Brazilian Northeast, Amazonia, South of Brazil and Uruguay. Over 80% of Brazil's energy comes from hydropower, and decisions concerning future availability and pricing require forecasts of river flow, ideally several months in advance. In this work the relationship between the Paraná River flow and the ENSO (El Ni o/Southern Oscillation) mode is investigated and statistical forecasts of river flow are tested. An evaluation of the relationship between the Pacific sea surface temperature and the Paraná River flow indicates an ENSO pattern over the equatorial Pacific. The time series of the ENSO mode obtained by applying principal components analysis on the sea surface temperature (SST) were used as predictors for the Paraná River flow forecast. Improvement in the model forecast skill is also obtained by considering the lagged river flow time series as a predictor.
Power spectrum for inflation models with quantum and thermal noises
Ramos, Rudnei O.;da Silva, L. A.
High Energy Physics - Phenomenology , 2013, DOI: 10.1088/1475-7516/2013/03/032
Abstract: We determine the power spectrum for inflation models covering all regimes from cold (isentropic) to warm (nonisentropic) inflation. We work in the context of the stochastic inflation approach, which can nicely describe both types of inflationary regimes concomitantly. A throughout analysis is carried out to determine the allowed parameter space for simple single field polynomial chaotic inflation models that is consistent with the most recent cosmological data from the nine-year Wilkinson Microwave Anisotropy Probe (WMAP) and in conjunction with other observational cosmological sources. We present the results for both the amplitude of the power spectrum, the spectral index and for the tensor to scalar curvature perturbation amplitude ratio. We briefly discuss cases when running is present. Despite single field polynomial-type inflaton potential models be strongly disfavored, or even be already ruled out in their simplest versions in the case of cold inflation, this is not the case for nonisentropic inflation models in general (warm inflation in particular), though higher order polynomial potentials (higher than quartic order) tend to become less favorable also in this case, presenting a much smaller region of parameter space compatible with the recent observational cosmological data. Our findings also remain valid in face of the recently released Planck results.
Comment on ``Neutrino masses and mixing angles in a predictive theory of fermion masses''
L. Lavoura,Jo?o P. Silva
Physics , 1993, DOI: 10.1103/PhysRevD.49.3783
Abstract: In the extension of the Dimopoulos--Hall--Raby model of the fermion mass matrices to the neutrino sector, there is an entry in the up-quark and neutrino Dirac mass matrices which can be assumed to arise from the Yukawa coupling of a {\bf 120}, instead of a {\bf 10} or a {\bf 126}, of SO(10). Although this assumption leads to an extra undetermined complex parameter in the model, the resulting lepton mixing matrix exhibits the remarkable feature that the $ \nu_{\tau} $ does not mix with the other two neutrinos. Making a reasonable assumption about the extra parameter, we are able to fit the large-mixing-angle MSW solution of the solar-neutrino problem, and we obtain $ m_{\nu_{\tau}} \sim 10 $ eV, the right mass range to close the Universe. Other possibilities for explaining the solar-neutrino deficit are also discussed.
Wigner-Moyal description of free variable mass Klein-Gordon fields
J. P. Santos,L. O. Silva
Physics , 2005, DOI: 10.1063/1.2049169
Abstract: A system of coupled kinetic transport equations for the Wigner distributions of a free variable mass Klein-Gordon field is derived. This set of equations is formally equivalent to the full wave equation for electromagnetic waves in nonlinear dispersive media, thus allowing for the description of broadband radiation-matter interactions and the associated instabilities. The standard results for the classical wave action are recovered in the short wavelength limit of the generalized Wigner-Moyal formalism for the wave equation.
High-brilliance synchrotron radiation induced by the plasma magnetostatic mode
F. Fiuza,L. O. Silva,C. Joshi
Physics , 2010, DOI: 10.1103/PhysRevSTAB.13.080701
Abstract: Using multi-dimensional PIC simulations we show that the magnetic undulator-type field of the plasma magnetostatic mode is indeed produced by the interaction of a laser pulse with a relativistic ionization front, as predicted by linear theory for a cold plasma. When the front with this magnetostatic mode is followed by a relativistic electron beam, the interaction of the beam with this magnetic field, produces FEL-type synchrotron radiation, providing a direct signature of the magnetostatic mode. The possibility of generating readily detectable ultrashort wavelength radiation using this mode, by employing state-of-the-art laser systems, is demonstrated, thus opening the way towards experimental observation of the hitherto unseen magnetostatic mode and the use of this plasma FEL mechanism to provide a source of high-brilliance ultrashort wavelength radiation.
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