The caffeine contents of dietary supplements commonly purchased in the US: analysis of 53 products with caffeine-containing ingredients

As part of a study initiating the development of an analytically validated Dietary Supplement Ingredient Database (DSID) in the United States (US), a selection of dietary supplement products were analyzed for their caffeine content. Products sold as tablets, caplets, or capsules and listing at least one caffeine-containing ingredient (including botanicals such as guarana, yerba mate, kola nut, and green tea extract) on the label were selected for analysis based on market share information. Two or three lots of each product were purchased and analyzed using high-pressure liquid chromatography (HPLC). Each analytical run included one or two National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) and two products in duplicate. Caffeine intake per serving and per day was calculated using the maximum recommendations on each product label. Laboratory analysis for 53 products showed product means ranging from 1 to 829 mg caffeine/day. For products with a label amount for comparison (n = 28), 89% (n = 25) of the products had analytically based caffeine levels/day of between −16% and +16% of the claimed levels. Lot-to-lot variability (n = 2 or 3) for caffeine in most products (72%) was less than 10%.     

Measuring vitamins and minerals in dietary supplements for nutrition studies in the USA

This article illustrates the importance of having analytical data on the vitamin and mineral contents of dietary supplements in nutrition studies, and describes efforts to develop an analytically validated dietary supplement ingredient database (DSID) by a consortium of federal agencies in the USA. Preliminary studies of multivitamin mineral supplements marketed in the USA that were analyzed as candidates for the DSID are summarized. Challenges are summarized, possible future directions are outlined, and some related programs at the Office of Dietary Supplements, National Institutes of Health are described. The DSID should be helpful to researchers in assessing relationships between intakes of vitamins and minerals and health outcomes.     

Raman and IR spectroscopy study of corrosion products on the surface of the hot‐dip galvanized steel with alkaline mud adhesion

The corrosion products formed on hot‐dip galvanized steel sheets for the automobile application with adhesion of alkaline mud containing different Cl⁻ ion contents are investigated by means of Raman and infrared (IR) spectroscopy. Results show that the Cl⁻ ion content in alkaline mud has great influence on the corrosion behavior of the galvanized steel. The Cl⁻ ions are responsible for the formation of the Zn₅Cl₂(OH)₈· H₂O layer on the surface of the steel at the early stage of corrosion. The rest of the Cl⁻ ions then penetrate and interrupt corrosion product layer resulting in pitting corrosion. Subsequently, the red corrosion product of α‐FeOOH (shaped as needle‐like structure) is formed, which then transforms into black rust of Fe₃O₄ (having a shape of slim needle). It is interesting to find out that pitting depth is inversely proportional to the Cl⁻ ion content. However, corrosion rate decreases with the increase of the Cl⁻ ions in mud. Copyright © 2009 John Wiley & Sons, Ltd.     

Instability theory of shock wave in a shock tube

The instability theory of shock wave in a shock tube including the effects of tube wall and contact surface is studied. The experimental data of unstable shock wave coincide with one of instability criteria derived in the present paper.     

Cu（Ⅱ）－Ln（Ⅲ）双核配合物的合成、磁性和抗菌活性

合成和表征了６种以草酰胺为桥联的异双核配合物Ｃｕ（ｏｘｅｎ）Ｌｎ（ｐｈｅｎ）２（ＣｌＯ４）３（ｏｘｅｎ代表Ｎ，Ｎ′－双（２－氨乙基）草酰胺根阴离子；ｐｈｅｎ为１，１０－邻菲咯琳；Ｌｎ表示Ｙ、Ｌａ、Ｃｅ、Ｎｄ、Ｇｄ和Ｙｂ）．测定了Ｃｕ（ｏｘｅｎ）Ｇｄ（ｐｈｅｎ）２（ＣｌＯ４）３·Ｈ２Ｏ的变温磁化率（４～３００Ｋ）；井用最小二乘法和从自旋Ｈａｍｉｌｔｏｎｉａｎ算符导出的磁方程拟合，求得交换积分Ｊ＝２．３ｃｍ－１；表明配合物中Ｃｕ（Ⅱ）和Ｇｄ（Ⅲ）离子间存在弱的铁磁性超交换作用。测试了配合物的抗菌活性。     

输气管道声波法泄漏检测技术的理论与实验研究

为探究输气管道声波法泄漏检测技术的基本原理和研究方法,建立了输气管道泄漏仿真模型和实验模型。首先,研究输气管道发生泄漏时声波产生机理,从而明确声波法泄漏检测技术的工作原理;其次根据声波法泄漏检测的原理建立Fluent仿真模型,通过CFD软件模拟输气管道泄漏得到流场和声场,得到声波信号特征;再次根据声波法泄漏检测的原理搭建实验管道,设计完成声波信号数据采集终端,并在仿真结果指导下完成输气管道泄漏检测实验,采集得到实验数据并进行分析,得到泄漏时声波信号特征并对仿真结果进行验证;最后对比多工况条件下的实验结果和仿真结果,分析不同工况条件对压力波动值的影响规律,从而总结输气管道声波法泄漏检测的仿真与实验研究方法,为声波法泄漏检测的实际工程应用提供理论基础。研究结果表明:输气管道泄漏产生的声波来源于泄漏时气体不稳定流动产生的偶极子声源和四极子声源;仿真模拟和实验研究的方法都可以完成声波法泄漏检测技术的研究,可以对声波法泄漏检测技术的推广和工程应用提供强大的理论支持和可行性保证。结论是:声波法泄漏检测技术可以很好的检测输气管道泄漏,是一种灵敏度高,检测时间短,值得推广的方法。      

铁磁偶合的间苯二甲酸根桥联Cu(Ⅱ)-Cu(Ⅱ)双核配合物的合成与表征

合成了两种新的双核配合物 [Cu2 (IPHTA) (Me2 bpy) 2 ] (Cl O4) 2 (a)和 [Cu2 (IPHTA) (NO2 - phen) 2 ](Cl O4) 2 (b) ,IPHTA代表间苯二甲酸根二价阴离子 ;Me2 bpy和 NO2 - phen分别表示 4,4′-二甲基 - 2 ,2′-联吡啶和 5-硝基 - 1 ,1 0 -邻菲罗啉。并通过元素分析、红外光谱、可见 -紫外光谱、ESR谱及电导等对配合物进行了表征 ;基于变温磁化率测量和自旋哈密顿算符 (H=- 2 JS1 · S2 )已推出交换积分 J=2 .36cm-1 (NO2 - phen)和J= 1 6.2 cm-1 (Me2 bpy) ,表明两个双核配合物中 Cu( )和 Cu( )离子间为铁磁偶合。     

求解时谐涡流模型鞍点问题的分块交替分裂隐式迭代算法的改进

分块交替分裂隐式迭代方法是求解具有鞍点结构的复线性代数方程组的一类高效迭代法.本文通过预处理技巧得到原方法的一种加速改进方法,称之为预处理分块交替分裂隐式迭代方法·理论分析给出了新方法的收敛性结果.对于一类时谐涡旋电流模型问题,我们给出了若干满足收敛条件的迭代格式.数值实验验证了新型算法是对原方法的有效改进.