响应面法微波降解EGCG制备EGC研究

目的 为探究微波降解EGCG方法制备EGC的效果,以EGC得率最大化为目标,探究微波降解的最佳工艺参数,并建立反映各参数间关系的二次多元方程模型。方法 本研究采用EGCG溶液为原料,运用微波加热降解EGCG制备EGC,通过梯度设置EGCG浓度、微波时长、微波强度三个工艺参数,进行单因素实验、响应面分析及最佳工艺组合验证实验,优化确定EGCG微波降解制备EGC的最佳工艺参数。结果 综合单因素实验及响应面分析,得到的最佳微波降解参数为：EGCG浓度5mg/ml、微波时长3.5min、微波强度为400W,且利用响应面法建立了EGC得率(Y)与EGCG浓度(A)、微波时长(B)、微波强度(C)的二次多元方程模型：Y=59.52+8.38*A+5.38*B+3.53*C-4.04*AB+6.92*AC-9.19*BC-9.99A2⁺0.0786*B2^-15.36*C2^,模型中,EGC得率最高可达62.08%。对最佳微波降解工艺参数进行验证实验,EGC得率为63.40%,与模型预测值接近。结论 运用微波降解EGCG制备EGC具有操作简单,可行性高的优势,且EGC得率稳定性高。     

1750m m热轧粗轧EGC冲顶故障的分析及处理

文章介绍了Siemens SE系列变频装置在八钢1750mm热轧厂粗轧立辊辊缝控制中的应用。通过分析EGC冲顶故障的原因,制定相应的整改措施,对传动装置和程序控制进行了改进。     

EGR/EGC技术结合系统降低柴油机排放的研究

对柴油机的排放尾气NOx，CO，HC和PM等进行全面分析，探索设计了一套由EGR（废气再循环技术）和EGC（发动机机外废气净化技术）结合的系统，EGR技术可以有效降低NOx的排放，机外废气净化技术技术可以在有效除去PM的同时降低HC，CO的排放，该系统能在较宽的转速和负荷范围内有效降低废气排放，解决同时降低NOx与PM排放的矛盾，废气排放全面降低。     

西门子SINAMICS S120传动系统在轧机EGC中的应用

本文主要介绍了西门子SINAMICS S120传动系统在济钢4300m新厚板轧机电动压下控制系统中的应用。     

Catechin stability of EGC- and EGCG-enriched tea drinks produced by a two-step extraction procedure

Catechin content of green tea drinks commercially available is reported to be very low in comparison with tea traditionally prepared, due to catechins conversion to their corresponding epimers during production. The purpose of this present study was to produce catechin-enriched tea drinks according to a two-step brewing procedure and to verify the catechin stability of those enriched drinks during storage. Those results confirmed that it is possible to produce EGC- and EGCG-enriched tea drinks regardless of the green tea used. Good extraction efficiencies were reached for the first and second extraction steps with catechin extraction yields ranging from 63.6% to 84.8%. Furthermore, it appeared that the catechin content in the two enriched tea drinks demonstrated a great stability since no significant degradation occurred within 8 weeks of storage. This simple two-step extraction procedure could be considered as an interesting way to produce enriched green tea drinks with more potent and stable bioactive catechins.     

The ability of gallate and pyrogallol moieties of catechins to inhibit P-glycoprotein function

The role of structure–activity relationships in the ability of catechins to inhibit P-glycoprotein (P-gp) function was investigated with respect to gallate and pyrogallol moieties. Experiments using octyl derivatives of gallic acid indicated that the gallate moiety required the catechol group and a neighboring carbonyl group to inhibit P-gp. On the other hand, the pyrogallol moiety appeared to require three hydroxyl groups to inhibit P-gp, according to comparisons between (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG). The difference in the number of hydroxyl groups that gallate or pyrogallol moieties required for P-gp inhibition, was due to the presence of a carbonyl group. The P-gp inhibition by catechins was restricted by their hydrophobicity. The pyrogallol moiety of EGC did not appear to inhibit P-gp because of its low hydrophobicity. The P-gp inhibitory activity of EGCG was speculated to be increased by the addition of long carbon chains to the C3″of gallate moieties.     

Interference analysis and capacity for forward link 3G CDMA network with adaptive antennas

In code division multiple access (CDMA) systems, the capacity of forward link (FL) communication to mobile receivers is limited primarily by co‐channel interference (CCI). Adaptive antenna arrays (AAAs) that use antenna arrays along with advanced signal processing at the base station (BS) have been proposed to mitigate this limitation. For a 3G CDMA cellular network, where each BS equipped with an AAA serves mixture of voice and data users within its coverage, we study FL capacity and investigate the effects of different factors (array topology, multipath angle spread, data rate, and beamforming algorithm) on this capacity under Rayleigh fading channel. By modeling the instantaneous signal‐to‐interference power ratio received at the mobile, we derive the system outage equation that considers blocking of either desired voice or data user. Simulation results show that for the same element spacing and number of antenna elements per cell, the uniform circular array (UCA) topology results in larger capacity than the sectorized uniform linear array (ULA) topology does, and that a larger angle spread or data user rate reduces FL capacity. Copyright © 2007 John Wiley & Sons, Ltd.     

Analysis of catechins from milk–tea beverages by enzyme assisted extraction followed by high performance liquid chromatography

Extraction and analysis of physiologically significant tea catechins from complex food matrices is complicated by strong association of tea catechins with macronutrients such as proteins. Dependable extraction methods are required to accurately assess and validate levels of bioactive tea catechins in new products. The objective of this work was to investigate recovery of tea catechins from dairy matrices and evaluate pepsin treatment as an enzymatic step to enhance catechin recovery from milk and other protein rich formulations. Brewed green tea was combined with skim milk to produce test solutions ranging from 10% to 50% milk. Samples were treated by either acid (0.1 N HCl), methanol, or by pepsin (40.0 mg/mL). Following treatments, samples were centrifuged and supernatants analyzed for tea catechins by reversed phase C18 HPLC with photodiode array detection. Recovery of total catechins was highest for pepsin treated samples (89–102%), followed by methanol deproteination (78–87%) and acid precipitation (20–74%) with values decreasing with increased milk content. Individual recovery of gallated catechins, namely epigallocatechin-gallate (EGCG) and epicatechin-gallate (ECG), was most affected by the presence and level of milk. The usefulness of pepsin treatment for enhancing recovery of tea catechins was further demonstrated in analysis of commercial soy and milk–tea beverages.     

A Quadrature Coded OFDM for Reducing Effects of Frequency Offset in Wireless Transmission System

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