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Search Results: 1 - 10 of 579173 matches for " C. M. Silva "
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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.
A nonautonomous epidemic model with general incidence rate and quarantine
César M. Silva
Quantitative Biology , 2012,
Abstract: We obtain conditions for eradication and permanence of the infectives for a nonautonomous SIQR model with time-dependent parameters, that are not assumed to be periodic. The incidence is given by functions of all compartments and the threshold conditions are given by some numbers that play the role of the basic reproduction number. We obtain simple threshold conditions in the autonomous, asymptotically autonomous and periodic settings and show that our thresholds coincide with the ones already established. Additionally, we obtain threshold conditions for the general nonautonomous model with mass-action, standard and quarantine-adjusted incidence.
Application of Photo-Fenton Process for the Treatment of Kraft Pulp Mill Effluent  [PDF]
M. D. Rabelo, C. R. Bellato, C. M. Silva, R. B. Ruy, C. A. B. da Silva, W. G. Nunes
Advances in Chemical Engineering and Science (ACES) , 2014, DOI: 10.4236/aces.2014.44050
Abstract: The present work evaluated the use of photo-Fenton process for the treatment of kraft pulp mill effluent. The photo-Fenton best operating conditions, such as pH, concentration, and H2O2: Fe2+ ratio were evaluated. The efficiency of the treatment was measured by COD (chemical oxygen demand) removal. The results showed that the optimum pH for the photo-Fenton process was equal to 3. The increase in H2O2 application resulted in an efficiency increase of the photo-Fenton process, although this was not a directly proportional relation. For most cases, the H2O2: Fe2+ proportion of 100:1 yielded the best results for COD removal. Solar radiation was more efficient than artificial UV to the COD removal. During the treatment the organic matter of the effluent was more oxidized than mineralized, showing a higher removal of COD than BOD (biochemical oxygen demand) and TOC (total organic carbon), respectively. So, photo-Fenton process increased the BOD/ COD ration but decreased the BOD/TOC ratio.
A Study on Ethanolysis and Methanolysis of Coconut Oil for Enzymatically Catalyzed Production of Biodiesel  [PDF]
Livia M. O. Ribeiro, Albanise E. Silva, Margarete C. S. Silva, Renata M. R. G. Almeida
Journal of Sustainable Bioenergy Systems (JSBS) , 2014, DOI: 10.4236/jsbs.2014.44020
Abstract: Biodiesel production by enzymatic catalysis has been the subject of much research for developing processes that can potentially compete with other types of catalysis. The objective of this study was to investigate the variables that influenced the transesterification of coconut oil catalyzed by immobilized lipase for biodiesel production. A full 24 factorial design with the variables tempera-ture (40°C - 60°C), enzyme concentration (3% - 7%), oil-ethanol ratio (1:6 - 1:10) and alcohol type (methanol-ethanol) was performed. The best conversion result (80.5%) was obtained using ethanol with a higher temperature, molar ratio and enzyme concentration. The obtained yields showed that the results attained with ethanol were more significant when compared with methanol.
Charged Gravastar in a Dark Energy Universe  [PDF]
C. F. C. Brandt, R. Chan, M. F. A. da Silva, P. Rocha
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.46118

Here we constructed a charged gravastar model formed by an interior de Sitter spacetime, a charged dynamical infinitely thin shell with an equation of state and an exterior de Sitter-Reissner-Nordstrom spacetime. We find that the presence of the charge is crucial to the stability of these structures. It can as much favor the stability of a bounded excursion gravastar, and still converting it in a stable gravastar, as make disappear a stable gravastar, depending on the range of the charge considered. There is also formation of black holes and, above certain values, the presence of the charge allows the formation of naked singularity. This is an important example in which a naked singularity emerges as a consequence of unstabilities of a gravastar model, which reinforces that gravastar is not an alternative model to black hole.

Axial Monopoles, Quantization of Electric Charge and Dynamical Discreteness of Space-Time
M. C. Nemes,Saulo C. S. Silva
Physics , 1993,
Abstract: In the present contribution we show that the introduction of axial currents in electrodynamics can explain the quantization of electric charge and introduces a dynamical discreteness of space-time, justifying thus the regularization of Feymman's integrals.
Dirac Monopoles and the Angular Momentum of the Electromagnetic Field
M. C. Nemes,Saulo C. S. Silva
Physics , 1993,
Abstract: We present a possible solution for the long standing problem of the incompatibility of Dirac's charge quantization condition with integer values for the angular momentum of the electromagnetic field.
On the Necessity of Rational Velocities: a Gedankenexperiment
M. C. Nemes,Saulo C. S. Silva
Physics , 1993,
Abstract: In the present contribution we propose a gedankenexperiment in which the restriction of rational values on the velocities emerges as a necessary condition from Classical Electromagnetism and Quantum Mechanics. This restriction is shown to be intimately connected to Dirac's electric charge quantization condition.
Frequency-Domain Receivers for Rate-1 Space-Time Block Codes  [PDF]
Mário Marques da Silva, Rui Dinis, Américo M. C. Correia
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2009, DOI: 10.4236/ijcns.2009.29098
Abstract: This paper considers iterative frequency-domain receivers for block transmission techniques with rate-1 Space Time Block Coding (STBC) for two and four transmit antennas using both Orthogonal Frequency Division Multiplexing (OFDM) and Single-Carrier (SC) schemes. The proposed receiver includes an interference canceller which enhances the performance of the non-orthogonal STBC scheme with 4 transmit antennas, allowing performances close to those of orthogonal codes. Our performance results show that combining STBC with block transmission techniques allows excellent performances.
Simulation of Multi-Frequency Induced Currents in Biophysical Models and Agar Phantoms of Breast Cancer  [PDF]
César A. González, Jesús G. Silva, Lucila M. Lozano, Salvador M. Polo
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2012, DOI: 10.4236/jemaa.2012.48044
Abstract: Breast cancer is the most frequent malignant neoplasm and the leading cause of cancer death in women in the world. Early detection techniques have been proposed on the basis of bioelectrical measurements. The aim of this study was to evaluate analytically and experimentally the inductive phase shift as a function of multi-frequency induced currents in breast cancer conditions. Virtual simulation by biophysical models and experimental measurements by magnetic induction in agar phantoms were developed to estimate the inductive phase shift as a function of the bulk electrical properties in typical breast volumes with tumors in specific positions. The analytical and experimental results are qualitatively consistent and provide evidence that the inductive phase shift has a potential clinical value to detect cancerous tumors toward inside a typical volume of breast tissue.
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