A power amplifier system for testing of distance relay operating characteristic

This paper describes a power amplifier system for testing of distance relay operating characteristic. This power amplifier is based on two three phase inverters with a neutral wire. The output power currents and voltages are controlled by a sliding mode controller. A developed matlab/simulink digital simulator generates the test signals. This test signals are converted in current and voltage references using a microcontroller to connect the digital simulator to the power converter amplifier. Experimental results from a laboratory prototype are presented and discussed

Impact of washing and freezing on nutritional composition, bioactive compounds, antioxidant activity and microstructure of mango peels

Mango peels are widely produced and highly perishable. Disinfectant washing and freezing are among the most used methods to preserve foods. However, their impact on products’ properties is conditioned by the foods’ features. This study evaluated for the first time the phytochemical composition, antioxidant activity, and microstructure of mango peels washed with peracetic acid (27 mg/mL for 19 min) and frozen at −20 °C for 30 days. Washing decreased the content of vitamin C (−7%), penta-O-galloyl-β-D-glucose (−23 %), catechin (−30 %), and lutein (−24 %), but the antioxidant activity was preserved. Freezing changed mango peels’ microstructure, increased free phenolic compounds, namely acid gallic (+36 %) and catechin (+51 %), but reduced bound phenolic compounds (−12 % to −87 %), bound phenolic compounds’ antioxidant activity (−51 % to −72 %), and violaxanthin (−51 %). Both methods were considered adequate to conserve mango peels since fiber and the main bioactive compounds (free mangiferin, free gallic acid, and β-carotene) remained unchanged or increased.info:eu-repo/semantics/publishedVersio

A simple low-cost simulation protocol for approximate localization of structural water molecules in DNA oligonucleotides

Using a computational low-cost protocol by combining molecular mechanics energy minimization and molecular dynamics employing the OPLS-AA force field, we were able to reproduce the main structural features of the first hydration shell of double-helix DNA hetero-oligonucleotides in the A (1DPL) and B-conformations (1DPN and 1ENN), whose coordinates are available with atomic resolution from crystallographic data. Our simple protocol also reproduced the main hydration patterns of DNA homo-oligonucleotides in the B-conformation [(AT)12 and (CG)12], obtained before by computer simulation using a longer and more sophisticated molecular dynamics protocol. A preliminary model of the first hydration shell of oligonucleotides may be very useful to those interested in performing quantum-mechanical calculations of systems where hydration features are unknown at the molecular level; the model may also be used by crystallographers during refinement steps.Utilizando um protocolo combinado de mecânica e dinâmica molecular, de baixo custo computacional, empregando-se a expressão e os parâmetros do campo de força OPLS-AA, foi possível reproduzir as principais características da primeira camada de hidratação de hetero-oligonucleotídeos de DNA em duplas hélices na conformação A (1DPL) e B (1DPN e 1ENN), conforme descrições cristalográficas com resolução atômica; nosso protocolo também reproduziu satisfatoriamente as características das primeiras camadas de hidratação de homo-oligonucleotídeos de DNA na conformação B [(AT)12 e (CG)12] obtidas em simulações por dinâmica molecular empregando-se protocolos mais longos e mais sofisticados. Um modelo preliminar da primeira camada de hidratação de oligonucleotídeos poderia ser útil para aqueles interessados em proceder cálculos mecânico-quânticos em sistemas cujas características de hidratação são desconhecidas em nível molecular ou, ainda, para refinamento de estruturas cristalográficas por comparação com padrões de difração experimentais