[Effects of pulsed electric fields on phenols and colour in young red wine].

The effects of pulsed electric fields (PEFs) applied on the 2 phenolic acids and 3 flavan-3-ols in young red wine, as well as the changes in colour intensity and colour hue, were investigated using a parallel treatment chamber. High performance liquid chromatography (HPLC) coupled with UV-visible detector was used to analyze the contents of these two phenols. The high voltage pulse generator in this experiment designed and produced by Tsinghua University can generate exponential decay pulses. The chambers of this experiment were parallel plate treatment chambers with interelectrode distances of 0.5 cm. The experimental results show that after PEF treatment (energy density: 24.5, 40.5, 60.5 J x mL(-1)) the concentration of most phenolic compounds changed significantly. Moreover, the energy density of 60. 5 J x mL(-1) was chosen as the optimal parameter.

[Spectral analysis of polyphenol oxidase (PPO) and lipoxygenase (LOX) treated by pulsed electric field].

Inactivation effect of pulsed electric field (PEF) on polyphenol oxidase (PPO) and lipoxygenase (LOX) was investigated using a laboratory PEF system with a coaxial treatment chamber. Circular dichroism (CD) and fluorescence analysis were used to study the conformation change of the protein. The experimental results show that PPO and LOX can be effectively inactivated by the PEF treatment. Inactivation effect of PPO and LOX increases with the increase in the applied electric strength and the treatment time. Activity of PPO and LOX can be reduced by 60.3% and 21.7% at 20 kV x cm(-1) after being treated for 320 micros respectively. The decrease of the negative peaks (208 and 215 nm in PPO spectra, 208 nm and 218 nm in LOX spectra) in CD spectra of PPO and LOX shows that PEF treatment caused a loss of alpha-helix and increase in beta-sheet content, indicating that conformation changes occur in the secondary structure of PPO and LOX enzyme. This effect was strengthened as the applied electric field increased: alpha-helical content of PPO and LOX was 56% and 29% after being treated at 8 kV x cm(-1), however, when the electric field was increased up to 20 kV x cm(-1), alpha-helical content of PPO and LOX decreased to 21% and 16% respectively. The decrease rate of alpha-helix and increase rate of beta-sheet in PPO are higher than LOX, indicating that the second conformation of PPO is less resistant to PEF treatment than LOX. The fluorescence intensity of LOX increases after PEF treatment. At the same time, increasing the applied pulsed electric field increases the fluorescence intensity emitted. Fluorescence measurements confirm that tertiary conformation changes occur in the local structure of LOX. However the possible mechanism of the conformation change induced by the PEF treatment is beyond the scope of the present investigation.

Kinetics of decolorization of azo dye by bipolar pulsed barrier discharge in a three-phase discharge plasma reactor.

Removal of amaranth, a commercial synthetic azo dye widely used in the dye and food industry, was examined as a possible remediation technology for treating dye-contaminated water. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetition frequency, etc., on decolorization kinetics were investigated. Experimental results show that an aqueous solution of 24 mg/l dye is 81.24% decolorized following 30 min plasma treatment for a 50 kV voltage and 0.75 m(3)/h gas flow rate. Decolorization reaction of amaranth in the plasma reactor is a pseudo first order reaction. Rate constant (k) of decolorization increases quickly with increasing the applied voltage, pulse repetition frequency and the gas flow rate. However, when the applied voltage is beyond 50 kV and increases further, increase rate of k decreases. In addition, k decreases quickly when the solution conductivity increases from 200 to 1481 microS/cm. The decolorization reaction has a high rate constant (k=0.0269 min(-1)) when the solution pH is beyond 10. Rate constant k decreases with the decrease of pH and reaches minimum at a pH of about 5 (k(min)=0.01603 min(-1)), then increases to 0.02105 min(-1) when pH decreases to 3.07. About 15% of the initial TOC can be degraded only in about 120 min non-thermal plasma treatment.

Inactivation effects of electrostatic field on Bacillus subtilis.

In order to study the inactivation effects of electrostatic field of electret films on Bacillus subtilis, a plane-plane electrode system was used to simulate the electric field of the electret films and the viability of B. subtilis affected by electrostatic field for different applying durations was investigated. It was found that the survival ratio of B. subtilis can be considerably affected by the field and duration. It was also found that the viability of bacillus decreases with the increase of the duration. In addition, the comparative survival ratio (CSR) of B. subtilis decreases to 35% even during a short duration as the applied field reaches an enough high value of more than 15 kV/cm. These indicated that the uniform field inactivated the viability of B. subtilis availability. Based on the inactivation effect of the applied field on the B. subtilis, the effectiveness of charged polypropylene films on the inactivation of B. subtilis was measured and discussed.

Image segmentation based on Mumford-Shah functional.

In this paper, the authors propose a new model for active contours segmentation in a given image, based on Mumford-Shah functional (Mumford and Shah, 1989). The model is composed of a system of differential and integral equations. By the experimental results we can keep the advantages of Chan and Vese's model (Chan and Vese, 2001) and avoid the regularization for Dirac function. More importantly, in theory we prove that the system has a unique viscosity solution.