Bifurcation Analysis of a Van der Pol-Duffing Circuit with Parallel Resistor

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Design and Analysis of Optical Interconnection Networks for a Dataflow Parallel Computer

This work shows the design, simulation, and analysis of two optical interconnection networks for a Dataflow parallel computer architecture. To verify the optical interconnection network performance on the Dataflow architecture, we have analyzed the load balancing among the processors during the parallel programs executions. The load balancing is a very important parameter because it is directly associated to the dataflow parallelism degree. This article proves that optical interconnection networks designed with simple optical devices can provide efficiently the dataflow requirements of a high performance communication system.

An investigation on parallel, divergent and convergent acetylene dual jet diffusion flames

Results are presented and discussed of an experimental investigation on acetylene turbulent dual jet diffusion flames. The study includes parameters of flames in parallel, divergent and convergent configurations. Tests with two parallel jets with addition of helium in the fuel stream were also performed and analysed. The variation of overall flame length and of other name physical characteristics, such as width, volume and conditions for lifting, are presented as functions of burner tip Reynolds number, jet distance from each other and inclination angle. The effects of diluent concentration in the fuel gas stream are presented for single and two parallel jets. (C) 1999 Elsevier B.V. Ltd.

Differential-Evolution-Based Optimization of the Dynamic Response for Parallel Operation of Inverters With No Controller Interconnection

In this paper, the use of differential evolution ( DE), a global search technique inspired by evolutionary theory, to find the parameters that are required to achieve optimum dynamic response of parallel operation of inverters with no interconnection among the controllers is proposed. Basically, in order to reach such a goal, the system is modeled in a certain way that the slopes of P-omega and Q-V curves are the parameters to be tuned. Such parameters, when properly tuned, result in system's eigenvalues located in positions that assure the system's stability and oscillation-free dynamic response with minimum settling time. This paper describes the modeling approach and provides an overview of the motivation for the optimization and a description of the DE technique. Simulation and experimental results are also presented, and they show the viability of the proposed method.

On the dynamic behaviour of a mass supported by a parallel combination of a spring and an elastically connected damper

This paper presents a consistent and concise analysis of the free and forced vibration of a mass supported by a parallel combination of a spring and an elastically supported damper (a Zener model). The results are presented in a compact form and the physical behaviour of the system is emphasised. This system is very similar to the conventional single-degree-of freedom system (sdof)-(Voigt model), but the dynamics can be quite different depending on the system parameters. The usefulness of the additional spring in series with the damper is investigated, and optimum damping values for the system subject to different types of excitation are determined and compared.There are three roots to the characteristic equation for the Zener model; two are complex conjugates and the third is purely real. It is shown that it is not possible to achieve critical damping of the complex roots unless the additional stiffness is at least eight times that of the main spring. For a harmonically excited system, there are some possible advantages in using the additional spring when the transmitted force to the base is of interest, but when the displacement response of the system is of interest then the benefits are marginal. It is shown that the additional spring affords no advantages when the system is excited by white noise. (c) 2007 Elsevier Ltd. All rights reserved.

Remifentanil, Isoflurane, and Preconditioning Attenuate Renal Ischemia/Reperfusion Injury in Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chimerism induction by nonmyeloablactive preconditioning and bone marrow infusion in rat small bowel transplantation

Em estudo recente demonstramos que a infusão de células da medula óssea do doador após o transplante intestinal não aumentou a sobrevida do enxerto quando se utilizou series curtas de drogas imunossupressoras. OBJETIVO: Neste estudo avaliamos se a utilização de diferentes regimes de irradiação em associação com a infusão de medula óssea altera a sobrevida do enxerto e a morbidade sobre receptor. MÉTODOS: Realizou-se o transplante heterotópico de intestino delgado, utilizando-se ratos Lewis como receptores e da como doadores, imunossuprimidos com FK 506 na dose de 1mg/kg/dia por 5 dias e distribuídos em 4 grupos: G1 (n= 4), não irradiado e sem infusão de medula óssea; G2 (n= 6), G3 (n= 9) e G4 (n= 6) foram infundidos com 100 x 10(6) células de medula após o transplante. Grupos 3 e 4 foram irradiados com 250 e 400 rd respectivamente. Os animais foram examinados diariamente para a detecção de rejeição e reação do enxerto versus hospedeiro, tendo sido colhidas amostras semanais de sangue para estudos de quimerismose biopsias quinzenais da estomia. RESULTADOS: Animais nos G1 e G2 apresentaram rejeição mínima no 15º pós-operatório, enquanto a reação do enxerto versus hospedeiro foi caracterizada nos G3 e G4. Os níveis de quimerismo total e de células T foram maiores nos grupos irradiados em comparação aos não irradiados. A causa mortis nos G1 e G2 foi a rejeição enquanto que nos G3 e G4 foi a reação do enxerto versus hospedeiro. CONCLUSÃO: Concluímos que a utilização de baixas doses de irradiações retardam o aparecimento da rejeição, mas não previne a ocorrência da reação do enxerto versus hospedeiro.

Ethyl Carbamate Analysis in German Fruit Spirits and Brazilian Sugarcane Spirits (Cachaca): Improved Sample Cleanup with Automated Parallel Evaporation

The analysis of alcoholic beverages for the important carcinogenic contaminant ethyl carbamate is very time-consuming and expensive. Due to possible matrix interferences, sample cleanup using diatomaceous earth (Extrelut) column is required prior to gas chromatographic and mass spectrometric measurement. A limiting step in this process is the rotary evaporation of the eluate containing the analyte in organic solvents, which is currently conducted manually and requires approximately 20-30 min per sample. This paper introduces the use of a parallel evaporation device for ethyl carbamate analysis, which allows for the simultaneous evaporation of 12 samples to a specified residual volume without manual intervention. A more efficient and, less expensive analysis is therefore possible. The method validation showed no differences between the fully-automated parallel evaporation and the manual operation. The applicability was proven by analyzing authentic spirit samples from Germany, Canada and Brazil. It is interesting to note that Brazilian cachacas had a relatively high incidence for ethyl carbamate contamination (55% of all samples were above 0.15 mg/l), which may be of public health relevance and requires further evaluation.

Hypoxic-preconditioning induces neuroprotection against hypoxia-ischemia in newborn piglet brain

Preconditioning-induced ischemic tolerance has been documented in the newborn brain, however, the signaling mechanisms of this preconditioning require further elucidation. The aims of this study were to develop a hypoxic-preconditioning (PC) model of ischemic tolerance in the newborn piglet, which emulates important clinical similarities to human situation of birth asphyxia, and to characterize some of the molecular mechanisms shown to be implicated in PC-induced neuroprotection in rodent models. One day old piglets were subjected to PC (8% O(2)/92% N(2)) for 3 h and 24 h later were exposed to hypoxia-ischemia (HI) produced by a combination of hypoxia (5% FiO(2)) for a period of 30 min and ischemia induced by a period of hypotension (10 min of reduced mean arterial blood pressure; 70% of baseline). Neuropathologic analysis and unbiased stereology, conducted at 24 h, 3 and 7 days of recovery following HI, indicated a substantial reduction in the severity of brain damage in PC piglets compared to non-PC piglets (P<0.05). PC significantly increased the mRNA expression of hypoxia-inducible factor-1 alpha (HIF-1 alpha) and its target gene, vascular endothelial growth factor (VEGF) at 0 h, 6 h, 24 h, 3 and 7 days of recovery. Immunoblot analysis demonstrated that PC resulted in HIF-1 alpha protein stabilization and accumulation in nuclear extracts of cerebral cortex of newborn piglet brain compared to normoxic controls. Protein levels of VEGF increased in a time-dependent manner in both cortex and hippocampus following PC. Double-immunolabeling indicated that VEGF is mainly expressed in neurons, endothelial cells and astroglia. Our study demonstrates for the first time the protective efficacy of PC against hypoxic-ischemic injury in newborn piglet model, which recapitulates many pathophysiological features of asphyxiated human neonates. Furthermore, as has been shown in rodent models of preconditioning, our results suggest that PC-induced protection in neonatal piglets may involve upregulation of VEGF. (C) 2011 Elsevier B.V. All rights reserved.

Postoperative periodontal pain prevention using two dexamethasone medication protocols: A double-blind, parallel-group, placebo-controlled randomized clinical trial

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Exercise preconditioning modulates genotoxicity induced by doxorubicin in multiple organs of rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermal performance of multipass parallel and counter-cross-flow heat exchangers

A thorough study of the thermal performance of multipass parallel cross-flow and counter-cross-flow heat exchangers has been carried out by applying a new numerical procedure. According to this procedure, the heat exchanger is discretized into small elements following the tube-side fluid circuits. Each element is itself a one-pass mixed-unmixed cross-flow heat exchanger. Simulated results have been validated through comparisons to results from analytical solutions for one- to four-pass, parallel cross-flow and counter-cross-flow arrangements. Very accurate results have been obtained over wide ranges of NTU (number of transfer units) and C* (heat capacity rate ratio) values. New effectiveness data for the aforementioned configurations and a higher number of tube passes is presented along with data for a complex flow configuration proposed elsewhere. The proposed procedure constitutes a useful research tool both for theoretical and experimental studies of cross-flow heat exchangers thermal performance.

THEORY OF ELASTICITY OF THE ABRIKOSOV FLUX-LINE LATTICE FOR UNIAXIAL SUPERCONDUCTORS - PARALLEL FLUX LINES

In this paper, we consider the extension of the Brandt theory of elasticity of the Abrikosov flux-line lattice for a uniaxial superconductor for the case of parallel flux lines. The results show that the effect of the anisotropy is to rescale the components of the wave vector k and the magnetic field and order-parameter wave vector cut off by a geometrical parameter previously introduced by Kogan.