Modulation of the antioxidant/pro-oxidant balance,cytotoxicity and antiviral actions of grape seed extracts

Grape seed extracts (GSEs) were investigated in yeast cells harbouring defects in their antioxidant system (regarding the cellular growth and growth recovery from H₂O₂ insult). GSEs antioxidant activity was detected in wild-type and mutant strains Δcta1, Δgsh1 and Δoye2glr1, while pro-oxidant activity in Δsod1 cells was seen. Assessment of proliferation of prostate cancer PC3 and HBV-replicating HepG2 2.2.15 cells treated with GSEs has shown higher cytotoxicity of red grape seed extract (RW) than white grape seed extract (WW) subjective to dose and period of administration. No antiviral effect was detected by measuring the secreted virion particles in HepG2 2.2.15 cells treated with GSEs. The GSEs play a dual antioxidant/pro-oxidant role in vivo according with the cellular antioxidant system deficiencies and exhibit cytotoxic properties in PC3 and HepG2 2.2.15 cell lines, but no antiviral action against HBV.     

加工过程中夏橙汁香气成分的SPME-GC-MS分析

采用固相微萃取- 气相色谱- 质谱法对伏令夏橙汁加工过程中5 个关键点样品的主要香气成分进行分析,共鉴定出50 种香气成分,主要为柠檬烯(84.79%～86.92%)、β- 月桂烯(3.87%～5.83%)、α- 蒎烯(1.03%～2.05%)、芳樟醇(0.02%～1.72%)、葵醛(0.15%～0.28%)、辛醛(0.03%～0.52%)和丁酸乙酯(0.12%～0.44%)等。加工过程对夏橙汁香气成分种类和含量有重要影响,5 个样品香气成分种类分别为38 种、36 种、31 种、30 种和20 种。精滤后烃类相对含量增加2.01%,醇类物质下降2.00%;脱气后烃类下降0.95%,醇类下降0.15%;灭菌后香气成分与脱气后相近;浓缩还原对香气影响最大,烃类和醇类比精滤后橙汁分别降低3.85%、1.16%。     

Antimicrobial activity of food-compatible plant extracts and chitosan against naturally occurring micro-organisms in tomato juice

BACKGROUND: Chitosan (AC) and five hydroalcoholic extracts from Lithospermum erythrorhizon (SE), Rheum palmatum (RE), Thymus vulgaris (AT), Lippia citriodora (PLX) and a mixture of Rosmarinus officinalis, Salvia lavandulifolia and Thymus mastichina (LA) were tested for antimicrobial activity against bacteria, yeasts and filamentous fungi using two broth dilution methods. The effects of adding single extracts on naturally occurring micro‐organisms and sensory qualities of raw tomato juice were also evaluated. RESULTS: SE extract exhibited the strongest activity, with minimum inhibitory concentrations (MICs) of 100–400 µg mL^?1 for Gram‐positive and 1600–3200 µg mL^?1 for Gram‐negative bacteria. Enterobacter aerogenes showed the greatest susceptibility to AC (MIC 1600 µg mL^?1). Lethal effects of extracts and AC were achieved at a minimum bactericidal concentration (MBC)/MIC ratio of 2 in 88% of assays. SE and RE extracts and AC also exhibited antifungal effect against yeasts, but they had no activity on filamentous fungi. Control and 100 mg L^?1 SE‐added tomato juices did not differ in acceptance, but this SE concentration was not effective in the control of microbial load throughout cold storage. CONCLUSION: Results confirm the antimicrobial potential of the plant extracts, but additional research is needed until the agents responsible for the activities have been determined in order to use them as natural constituents of multiple‐barrier food preservation systems. Copyright © 2012 Society of Chemical Industry     

Feasibility of preparing additive manufactured porous stainless steel felts with mathematical micro pore structure as novel catalyst support for hydrogen production via methanol steam reforming

In this paper, an additive manufacturing prepared porous stainless steel felt (AM-PSSF) is proposed as a novel catalyst support for hydrogen production via methanol steam reforming (MSR). In the method, 316 L stainless steel powder with diameter of 15–63 μm is processed by the additive manufacturing technology of selective laser melting (SLM). To accomplish the preparation, the reforming chamber where the AM-PSSF is embedded is firstly divided into an all-hexahedron mesh. Then, the triply periodic minimal surface (TPMS) unit with mathematical form, high interconnectivity and large specific surface area is mapped into the hexahedrons based on shape function, forming the fully connected three-dimensional (3D) micro pore structure of the AM-PSSF. By correlating the mathematical parameter and the porosity of the TPMS unit, and taking into account the SLM process, the porosity of the AM-PSSF is well controlled. Based on the designed 3D pore structure model, the AM-PSSF is produced using standard SLM process. The application of the AM-PSSF as catalyst support for hydrogen production through MSR indicates that: 1) both the naked and catalyst-coated AM-PSSF have the characteristics of high porosity, large specific surface area and high connectivity; 2) the MSR hydrogen production performance of the AM-PSSF is better than that of the commercial stainless steel fiber sintered felt. The feasibility of AM-PSSF as catalyst support for MSR hydrogen production may pave a better way to balance different requirements for catalyst support, thanks to the excellent controllability provided by AM on both the external shape and the internal pore structure, and to the produced rough surface morphology that benefits the catalyst adhesion strength. In addition, catalyst support with pore structures that are more accommodated with the flow field and the reaction rate of MSR reaction may be prepared in future, since the entire catalyst support structure, from macro scale to micro scale, is under control.     

How micro-phase separation alters the heating rate effects on globular protein gelation

This study was conducted to determine how the combination of heating rate and pH can be used to alter viscoelastic properties and microstructure of egg white protein and whey protein isolate gels. Protein solutions (1% to 7% w/v protein, pH 3.0 to 8.5) were heated using a range of heating rates (0.2 to 60 °C/min) to achieve a final temperature of 80 °C. The gelation process and viscoelastic properties of formed gels were evaluated using small strain rheology. Single phase or micro-phase separated solution conditions were determined by confocal laser scanning microscopy. In the single phase region, gels prepared by the faster heating rates had the lowest rigidity at 80 °C; however, a common G' was achieved after holding for 4 h at 80 °C . On the other hand, under micro-phase separation conditions, faster heating rates allowed phase separated particles to be frozen in the network prior to precipitation. Thus, gels produced by slower heating rates had lower rigidities than gels produced by faster heating rates. The effect of heating rate appears to depend on if the solution is under single phase or micro-phase separated conditions. PRACTICAL APPLICATION: The effect of heating rate and/or time on protein gel firmness can be explained based on protein charge. When proteins have a high net negative charge and form soluble aggregates, there is no heating rate effect and gels with equal firmness will be formed if given enough time. In contrast, when electrostatic repulsion is low, there is a competition between protein precipitation and gel formation; thus, a faster heating rate produces a firmer gel.     

Axial heterostructure nanoarray as all‐solid‐state micro‐supercapacitors

The end‐to‐end axial heterojunction one‐dimensional nanoarray combined poly(3,4‐ethylenedioxythiophene) (PEDOT) and manganese dioxide (MnO₂) have been successfully designed and fabricated. The electrochemical performance was investigated in detail after processing the axial PEDOT/MnO₂ heterostructure nanoarray (APMHN) into flexible micro‐supercapacitors, namely, PM‐MSC. The presence of flexible PEDOT segment effectively improved the conductivity and also provided an important material basis for the preparation of flexible PM‐MSC. Further, PEDOT has good contact with both Au substrate and MnO₂ segment, ensuring that the charge can quickly shuttle back and forth between the electrode and the current collector. The PM‐MSC showed the highest specific capacitance of 209.89 mF·cm^?2 compared with the P‐MSC assembled from PEDOT nanoarray and M‐MSC assembled from MnO₂ nanoarray. The PM‐MSC possesses good flexibility, making the capacitance performance of the PM‐MSC show almost no deterioration under the 180° bent state. Moreover, several series or parallel PM‐MSCs enable a variety of electronic devices to work properly. The APMHN exhibits some new advantages, enabling the integration of physical and chemical properties of the two separate components, while providing a new way of thinking for the design and manufacture of MSC for flexibility.     

沼气成分对微型燃气轮机燃烧室影响的数值分析

为了探究沼气成分的变化对微型燃气轮机燃烧室性能产生的影响,对微型燃气轮机环形燃烧室在不同成分沼气条件下的流动及燃烧过程进行了数值分析,得到了燃烧室内部的压力、温度及污染物生成量等参数,并对比了在不同甲烷含量的沼气下,燃烧室燃气侧的来流参数、内部温度和污染物分布以及出口参数的变化。计算结果表明:为保证微型燃气轮机的热负荷,燃气中甲烷含量的降低将增大燃气侧的流量以及压力。而燃气中二氧化碳含量的增加,增大了燃烧室内的高温区域面积以及温度梯度,并影响了燃烧反应的充分进行,增加了NO_x与CO的生成量。     

微型燃气轮机燃烧室性能影响因素的探讨

针对微型燃气轮机燃烧室性能的各种影响因素(进气条件、燃料热值、燃烧室结构等)对燃烧稳定性和燃烧效率的影响,介绍了国内外相关实验和数值模拟研究现状,分析了燃烧室主要污染物的生成机理和影响因素,以及降低氮氧化物排放浓度的技术措施。     

三种加热方式对油脂品质影响的比较

采用电磁炉、微波炉、常规加热对大豆油、花生油进行处理，测定其酸价和过氧化值，以比较三种加热方式对油脂品质的影响。结果表明，电磁炉加热对油脂品质的影响最大，微波炉加热对油脂品质的影响次之，常规加热的影响最小；花生油、豆油依次对热效应的敏感程度增加；间歇加热、加新油加热有利于油脂品质的保护。     

基于STM32的开环霍尔电流传感器的温度补偿研究

研究了一种基于软件补偿结合恒流源补偿的改进温度补偿方法,应用单片机、恒流源、数字温度传感器、乘法器等硬件电路,对传统软件补偿进行了优化,补偿效果较传统恒流源补偿有了明显提升,“温漂”整体下降了约13.7%。在传统的温度补偿方法如热敏元件补偿、恒流源补偿、软件补偿等方式上做了补充,对于霍尔电流传感器精度的提升及实际生产需求的满足有重要意义。