食用天然抗氧化剂研究进展

综述了各种来源的天然抗氧化剂，它们的抗氧化成分和抗氧化效果。     

Selective synthesis of para–para′-dimethyldiphenylmethane over H-beta zeolite

Selective synthesis of para–para′-dimethyldiphenylmethane (para–para′-DMDPM) from the condensation between toluene and formaldehyde was investigated over H-X, H-Y, H-ZSM-5, H-mordenite and MCM-41. Characterizations (NH₃-TPD-MS and pore structure) disclosed that the catalytic activity of various zeolites depends mainly on its strong acid site and accessibility of the internal pores. H-beta zeolite, with a unique pore sized in 0.66 nm and higher proportion of stronger acid site, exhibited the highest activity and stereo-selectivity (86.5%). Small sized H-beta zeolite was more active due to the enhanced accessibility of its acid site, and this kind of zeolite remained a higher stereo-selectivity (>80%) even at higher temperature, longer reaction time and recycle usage. The best yield of para–para′-DMDPM reached 71.1% at 140°C over H-beta zeolite and it could be used in recycle without loss of its structure, activity and stereo-selectivity.     

大孔隙地层防渗堵漏灌浆新技术及工程应用

渗漏是水电工程、地下矿山等工程中经常碰到的问题,对于多数工程而言,渗漏水多是由大孔隙形成的集中渗漏通道造成的。灌浆是解决工程渗漏问题的重要手段,但对于动水条件下大孔隙地层的防渗堵漏,常规灌浆技术无法经济、有效解决此类问题。本文基于已有研究成果,根据大孔隙地层防渗堵漏特点,总结了新型速凝膏浆和低热沥青两种新型灌浆材料及灌浆工艺技术,并在工程中得到了成功应用,可为解决大孔隙地层防渗堵漏问题提供有益参考。     

Efficient reductive dechlorination of monochloroacetic acid by sulfite/UV process

Most halogenated organic compounds (HOCs) are toxic and persistent, and their efficient destruction is currently a challenge. Here, we proposed a sulfite/UV (253.7 nm) process to eliminate HOCs. Monochloroacetic acid (MCAA) was selected as the target compound and was degraded rapidly in the sulfite/UV process. The degradation kinetics were accelerated proportionally to the increased sulfite concentration, while the significant enhancement by increasing pH only occurred in a pH range of 6.0-8.7. The degradation proceeded via a reductive dechlorination mechanism induced by hydrated electron (e(aq)(-)), and complete dechlorination was readily achieved with almost all the chlorine atoms in MCAA released as chloride ions. Mass balance (C and Cl) studies showed that acetate, succinate, sulfoacetate, and chloride ions were the major products, and a degradation pathway was proposed. The dual roles of pH were not only to regulate the S(IV) species distribution but also to control the interconversion between e(aq)(-) and H(?). Effective quantum efficiency (Φ) for the formation of e(aq)(-) in the process was determined to be 0.116 ± 0.002 mol/einstein. The present study may provide a promising alternative for complete dehalogenation of most HOCs and reductive detoxification of numerous toxicants.     

富水条件下低热沥青浆液流动特性试验研究

低热沥青灌浆是在动水条件下封堵大空隙地层渗流通道的一种非常有效的方法。文中开展了富水条件下低热沥青浆液扩散性能和抗冲性能试验研究,揭示了低热沥青浆液在富水条件下的性能变化规律,该浆液具有良好的扩散能力,可基本满足在中等块石地层中灌浆孔排距对浆液扩散范围的要求。通过试验获得了不同流速条件下低热沥青的抗冲性能指标、并与速凝膏浆、水泥-水玻璃浆液进行了对比研究,采用低热沥青浆液进行封堵时,封堵率100%,封堵速度快,并且低热沥青-水泥基灌浆材料的复合灌浆弥补低热沥青结石体强度较低的不足。其成果可为类似工程提供有益的参考。     

基于光谱聚类的高分影像复杂地块特征提取方法研究

高空间分辨率遥感技术为大范围判识农用地利用类型提供了丰富的数据源.农用地类型多样性和复杂性给高效应用高分影像识别农用地类型带来很大挑战.地块矢量的引入可以帮助更好综合利用多元影像特征,进而提高农用地类型判识精度.但是,传统地块特征提取方法将地块视为一个整体,通过对地块内部像元特征平均实现地块特征表达,不能很好适用于地块...     

五味子藤茎木脂素对小鼠镇静催眠及抗焦虑作用研究

目的:研究五味子藤茎木脂素（Schisandra chinensis vine stem lignans,SSL）的镇静、抗焦虑及催眠作用并初步探讨其作用机制。方法:将150只ICR雄性小鼠平均随机分为5组,分别为空白对照组、SSL低、中、高剂量组和地西泮阳性对照组。采用灌胃给药,每次0.1 mL/10 g,每天一次,连续7 d。应用小鼠自主活动实验观察镇静效果;应用高架十字迷宫、高架零迷宫实验观察抗焦虑作用;通过戊巴比妥钠协同睡眠实验观察催眠作用;用酶联免疫吸附法检测小鼠脑组织中γ-氨基丁酸（γ-aminobutyric acid, GABA）、谷氨酸（glutamate, Glu）含量。应用Western blot方法检测小鼠脑组织中GABA_Aα1表达水平。结果:与对照组比,各剂量SSL显著减少小鼠站立次数和活动次数（P<0.01）;中、高剂量SSL显著增加小鼠进入开放臂次数（open arm entry, OE）,开放臂停留时间（open arm time, OT）和开放探头次数（open arm probe, OP）（P<0.05或P<0.01）;各剂量SSL均增加阈下剂量戊巴比妥钠诱导小鼠睡眠只数,显著延长阈剂量戊巴比妥钠诱导的小鼠睡眠时间（P<0.05或P<0.01）,缩短小鼠睡眠潜伏期（P<0.01）;各剂量SSL组小鼠脑组织中GABA含量极显著增加（P<0.01）,而中、高剂量SSL组小鼠脑组织中Glu含量极显著降低（P<0.01）,GABA/Glu极显著增加（P<0.01）。高剂量SSL组小鼠脑组织中GABA_Aα1蛋白表达极显著增加（P<0.01）。结论:SSL对小鼠具有镇静、催眠及抗焦虑作用,其机制可能与其调节其脑组织中GABA及Glu含量及GABA_Aα1受体表达水平有关。     

基于水化度的泵送混凝土温升模型及参数反演

针对泵送大体积混凝土绝热温升高、早期水化速率快的特点,结合绝热温升试验,构建了基于水化度的水化温升速率模型(简称水化度模型),采用人工蜂群算法对水化度模型、双曲线模型、单指数模型和双指数模型参数进行反演对比分析,将水化度模型应用于5组绝热温升试验结果拟合中,使用4种温升模型对上海某泵闸工程混凝土试块温度场进行了反馈仿真...     

可调整式“一面两销”定位装置的应用

“一面两销”定位是机械加工中工件与夹具、夹具与机床定位方式中最常用的一种形式,介绍了一种可调整式“一面两销”定位装置的设计特点,通过定位销基座的方式完成定位销和机床夹具本体的连接,同时具有位置可调性,从而满足定位销的位置优化。相对于固定式“一面两销”定位装置,在专用夹具设计应用中具有较大的便捷性、优越性和兼容性,能够针对夹具定位误差进行补偿校正,有效地消除各种定位误差带来误差影响,提高一面两销定位精度,大大提高工件加工的位置精度。     

低压综合配电箱JP柜标准换版试验分析

介绍GB/T 15576标准换版后低压综合配电箱JP柜的型式试验项目,逐项分析标准换版后JP柜新增的试验项目及试验要求,有变化的试验项目及试验要求,总结无变化的试验项目.对于工频耐受电压试验、电磁兼容性试验(EMC)、涌流试验用表格的形式进行了比对说明.