874 resultados para expression of power


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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In the present study, the GPD2 gene from Saccharomyces cerevisiae, which codifies for the enzyme glycerol-3-phosphate dehydrogenase (GPDH), was cloned from the pPICZ-alpha expression vector and used with the purpose of inducing the extracellular expression of the glycerol-3-phosphate dehydrogenase under the control of the methanol-regulated AOX promoter. The presence of the GPD2 insert was confirmed by PCR analysis. Pichia pastoris X-33 (Mut(+)) was transformed with linearized plasmids by electroporation and transformants were selected on YPDS plates containing 100 mu g/mL of zeocin. Several clones were selected and the functionality of this enzyme obtained in a culture medium was assayed. Among the mutants tested, one exhibited 3.1 x 10(-2) U/mg of maximal activity. Maximal enzyme activity was achieved at 6 days of growth. Medium composition and pre-induction osmotic stress influenced protein production. Pre-induction osmotic stress (culturing cells in medium with either 0.35 M sodium chloride or 1.0 M sorbitol for 4h prior to induction) led to an increase in cell growth with sorbitol and resulted in a significant increase in GPDH productivity with sodium chloride in 24h of induction approximately fivefold greater than under standard conditions (without pre-induction). (C) 2010 Elsevier B.V. All rights reserved.

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A great deal of effort has been devoted to elucidating the psychopharmacology underlying addiction and relapse. Long-term neuroadaptations in glutamate transmission seem to be of great relevance for relapse to stimulant abuse. In this study, we investigated amphetamine-induced conditioned place preference during adolescence and the reinstatement of the conditioned behavior following a priming injection of the drug 1 day (adolescence), 30 days (early adulthood) and 60 days (adulthood) after the extinction test. The nucleus accumbens was dissected immediately after the reinstatement test to examine alterations in GluR1 and NR1 subunits of glutamatergic receptors. Our results showed that a priming injection of amphetamine was able to reinstate the CPP 1 and 30 days after extinction. However, it failed to reinstate the conditioned response after 60 days. GluR1 levels were decreased on days 1 and 30 but not on day 60 while NR1 levels were unaltered in the reinstatement test. Using a relapse model we found that reinstatement of amphetamine-induced conditioning place preference during adolescence is long lasting and persists through early adulthood. Decreased levels of GluR1 in the nucleus accumbens might be related to the reinstatement of amphetamine-induced conditioning place preference. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.

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The conventional Newton and fast decoupled power flow (FDPF) methods have been considered inadequate to obtain the maximum loading point of power systems due to ill-conditioning problems at and near this critical point. It is well known that the PV and Q-theta decoupling assumptions of the fast decoupled power flow formulation no longer hold in the vicinity of the critical point. Moreover, the Jacobian matrix of the Newton method becomes singular at this point. However, the maximum loading point can be efficiently computed through parameterization techniques of continuation methods. In this paper it is shown that by using either theta or V as a parameter, the new fast decoupled power flow versions (XB and BX) become adequate for the computation of the maximum loading point only with a few small modifications. The possible use of reactive power injection in a selected PV bus (Q(PV)) as continuation parameter (mu) for the computation of the maximum loading point is also shown. A trivial secant predictor, the modified zero-order polynomial which uses the current solution and a fixed increment in the parameter (V, theta, or mu) as an estimate for the next solution, is used in predictor step. These new versions are compared to each other with the purpose of pointing out their features, as well as the influence of reactive power and transformer tap limits. The results obtained with the new approach for the IEEE test systems (14, 30, 57 and 118 buses) are presented and discussed in the companion paper. The results show that the characteristics of the conventional method are enhanced and the region of convergence around the singular solution is enlarged. In addition, it is shown that parameters can be switched during the tracing process in order to efficiently determine all the PV curve points with few iterations. (C) 2003 Elsevier B.V. All rights reserved.

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One of the important issues about using renewable energy is the integration of dispersed generation in the distribution networks. Previous experience has shown that the integration of dispersed generation can improve voltage profile in the network, decrease loss, etc. but can create safety and technical problems as well. This work report the application of the instantaneous space phasors and the instantaneous complex power in observing performances of the distribution networks with dispersed generators in steady state. New IEEE apparent power definition, the so-called Buchholz-Goodhue effective apparent power, as well as new proposed power quality (oscillation) index in the three-phase distribution systems with unbalanced loads and dispersed generators, are applied. Results obtained from several case studies using IEEE 34 nodes test network are presented and discussed. (C) 2006 Elsevier B.V. All rights reserved.

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The parameterized fast decoupled power flow (PFDPF), versions XB and BX, using either theta or V as a parameter have been proposed by the authors in Part I of this paper. The use of reactive power injection of a selected PVbus (Q(PV)) as the continuation parameter for the computation of the maximum loading point (MLP) was also investigated. In this paper, the proposed versions obtained only with small modifications of the conventional one are used for the computation of the MLP of IEEE test systems (14, 30, 57 and 118 buses). These new versions are compared to each other with the purpose of pointing out their features, as well as the influence of reactive power and transformer tap limits. The results obtained with the new approaches are presented and discussed. The results show that the characteristics of the conventional FDPF method are enhanced and the region of convergence around the singular solution is enlarged. In addition, it is shown that these versions can be switched during the tracing process in order to efficiently determine all the PV curve points with few iterations. A trivial secant predictor, the modified zero-order polynomial, which uses the current solution and a fixed increment in the parameter (V, theta, or mu) as an estimate for the next solution, is used for the predictor step. (C) 2003 Elsevier B.V. All rights reserved.

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This work presents the application of the Decentralized Modal Control method for pole placement in multimachine power systems utilizing FACTS (Flexible AC Transmission Systems), STATCOM (Static Synchronous Compensator) and UPFC (Unified Power Flow Controller) devices. For this, these devices are equipped with supplementary damping controllers, denominated POD ( Power Oscillation Damping), achieving a coordinated project with local controllers (Power System Stabilizers - PSS). Comparative analysis on the function of damping of the FACTS, STATCOM and UPFC is performed using the New England System that has 10 generators, 39 buses and 46 transmission lines. (c) 2011 Elsevier Ltd. All rights reserved.

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The power system stability analysis is approached taking into explicit account the dynamic performance of generators internal voltages and control devices. The proposed method is not a direct method in the usual sense since conclusion for stability or instability is not exclusively based on energy function considerations but it is automatic since the conclusion is achieved without an analyst intervention. The stability test accounts for the nonconservative nature of the system with control devices such as the automatic voltage regulator (AVR) and automatic generation control (AGC) in contrast with the well-known direct methods. An energy function is derived for the system with machines forth-order model, AVR and AGC and it is used to start the analysis procedure and to point out criticalities. The conclusive analysis itself is made by means of a method based on the definition of a region surrounding the equilibrium point where the system net torque is equilibrium restorative. This region is named positive synchronization region (PSR). Since the definition of the PSR boundaries have no dependence on modelling approximation, the PSR test conduces to reliable results. (C) 2008 Elsevier Ltd. All rights reserved.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)