Kinetics and equilibria of tea infusion: Rates of extraction of theaflavin,caffeine and theobromine from several whole teas and sieved fractions

The rates of infusion of theaflavin and caffeine into water at 80°C have been measured for Kapchorua Pekoe Fannings, Kapchorua Pekoe Dust, Betjan Flowery Broken Orange Pekoe and Rupai Flowery Orange Fannings whole teas and sieved fractions. For Kapchorua PF fractions the rates of theobromine infusion were also determined. Caffeine always infused faster than theobromine, and both infused faster than theaflavin. Rate constants were obtained from the slopes of first order kinetic plots which yielded straight lines with small intercepts. The rate constants for all three constituents increased by a factor of 2.2 as leaf size decreased from 850–1000μm to 500–600μm. The rates of extraction from whole teas varied more than fourfold. Kapchorua PD gave the most rapid rates and Betjan FBOP the slowest. Comparisons of similarly sized fractions of teas showed that leaf size distributions accounted for half these differences and the intrinsic properties of the leaf for the remaining factor of two. The Kenyan CTC teas gave higher rate constants than the Indian orthodox teas. From the rate constants, the effective diffusion coefficients for theaflavin and caffeine in Betjan FBOP leaf were calculated and found to be some 100 times smaller than in water. This shows the diffusion processes within the leaf to be complex ones.     

Analysis and Design of ITER 1 MV Core Snubber

The core snubber, as a passive protection device, can suppress arc current and absorb stored energy in stray capacitance during the electrical breakdown in accelerating electrodes of ITER NBI. In order to design the core snubber of ITER, the control parameters of the arc peak current have been firstly analyzed by the Fink-Baker-Owren (FBO) method, which are used for designing the DIIID 100 kV snubber. The B-H curve can be derived from the measured voltage and current waveforms, and the hysteresis loss of the core snubber can be derived using the revised parallelogram method. The core snubber can be a simplified representation as an equivalent parallel resistance and inductance, which has been neglected by the FBO method. A simulation code including the parallel equivalent resistance and inductance has been set up. The simulation and experiments result in dramatically large arc shorting currents due to the parallel inductance effect. The case shows that the core snubber utilizing the FBO method gives more compact design.     

美国食品保护和进口食品监管新动向与我国对策建议

对美国食品药品管理局(FDA)新近推出的《食品保护计划》进行了分析与研究,阐述了美国食品保护和进口食品监管的新动向及对我国可能造成的影响,并提出了我国的对策建议。认为美国上述食品保护和食品监管新举措将对我国出口食品安全体系运行的有效性提出新的挑战,可能增加我国输美食品企业的负担,导致我国部分输美食品企业遭到淘汰,美方认可的第三方检查机构将在我境内异军突起。建议密切关注美国食品保护和进口食品监管新动向,评估美国新推出的食品保护计划对我国可能造成的影响,关注和研究第三方食品检查机构的发展和运行趋势,加强与美国FDA在进出口食品监管领域的交流与合作,对美国食品保护与进口食品监管研究课题进行科研立项,借鉴国外食品监管先进经验加强进出口食品安全保障体系建设。     

美食旅游开发模式研究进展

从消费者和经济发展两方面分析了美食旅游的价值和意义,将美食旅游开发模式分为地域美食旅游、节庆美食旅游和主题美食旅游3类,列举国内外3种美食旅游模式的开发现状,并给出了未来美食旅游发展建议。     

一类随机利率下的变额寿险模型

以反射布朗运动和泊松分布为基础,建立了一个半连续时间情形下的随机利率的模型.在此模型下对寿险理论中的纯保费、年金和责任准备金进行研究,不仅可以保证利率的恒正性,还可以通过参数调节有效地控制利率随机波动的幅度,从而在一定程度上降低利率风险的影响.     

城市规划视野下公共决策研究

城市规划公共决策是城市规划作为一项公共政策的制定和实施过程.在决策理论基础上,本文通过对国内外城市规划公共决策的研究现状进行梳理和比较,对研究的差异性及研究重点领域等相关问题进行评论和总结,拟对我国城市规划公共决策发展提出建议.     

施氮量对烤烟产质量和烟碱含量的影响

为解决烤烟上部叶烟碱含量偏高问题,确定适宜的施氮量,通过田间试验,研究了东南烟区烤烟主栽品种K326、云烟85在不同施氮量条件下的烟叶产、质量和烟碱含量的变化。结果表明:在保障烟草正常生长发育和烟叶产质量的基础上,适当控制氮肥用量可有效降低烟叶中烟碱含量和上部烟叶的比例,提高烟叶(尤其是上部烟叶)的可用性。     

当前国际国内超硬材料动态分析

经常研究国内外行业动态,对行业、企业决策和发展是有益的。该文以最新的信息分析了原G.E公司、De beers公司及俄国相关企业的最新动态;同时讨论了我国的大压机、小压机及两面顶压机现状;国际上大颗粒单晶研究方向。此外,还就当前业内人士应注意的相关技术问题,如设备、触媒、石墨、传压介质等的现状和近期应注意的核心技术问题作了广泛的讨论,并对市场竞争作了阐述。文后重申了几多几少和六句话,这对合成优质高产金刚石极为重要。     

我国苹果生产的国际地位与差距分析

近年来,我国苹果生产发展速度很快,对全球苹果供给贡献巨大,地位举足轻重。但同时在单产水平、栽培制度、机械化、标准化和品种砧木等方面与国际先进水平相比仍存在巨大差距。本文利用统计数据对我国苹果生产的国际地位和发展趋势进行了分析,并在国际比较的基础上提出了我国苹果生产存在的差距和问题。     

International Regulations of Propolis Quality: Required Assays do not Necessarily Reflect their Polyphenolic‐Related In Vitro Activities

Propolis has been proposed as a polyphenolic‐rich natural product potentially able to be used for human consumption or even for medicinal proposes. To guarantee a minimum phenolic and flavonoid content and as consequence of their related‐biological activities, international requirements of propolis quality are commonly applied. In this work we assessed phenolic and flavonoid contents of propolis; the antioxidant capacity (toward peroxyl radicals and hypochlorous acid); the ability to generate nitric oxide (NO); and, finally the antimicrobial activity of 6 propolis samples from the VI region of Chile. Our results show that the total phenolic and flavonoid content of propolis samples are not always in agreement with their polyphenolic‐associated in vitro activities. For example, P03 and P06 samples showed the lowest (25 ± 4 GAE/g propolis) and the highest (105 ± 3 GAE/g propolis) total phenolic content, respectively. This was in agreement with flavonoid content and their Oxygen Radical Absorbance Capacity (ORAC) activity. However, this dependence was not observed toward HOCl, NO release and antimicrobial activity. Based on our results, we consider that, in order to guarantee the antioxidant or antimicrobial in vitro effects, the international regulations of propolis quality should contemplate the convenience of incorporating other simple analytical test such as ORAC or antimicrobial tests.