Improved determination of D-glucosamine hydrochloride in health foods by HPLC using 7-fluoro-4-nitrobenzo-2-oxa-l,3-diazole as a derivative

Abstract: This article presents an improved method to detect d ‐glucosamine hydrochloride in health foods. A simple precolumn derivatization procedure with 7‐flouro‐4‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐F) reagent was employed. The separation of the derivatized d ‐glucosamine hydrochloride (NBD‐d ‐glucosamine hydrochloride) was performed using a mobile phase consisting of acetonitrile, potassium dihydrogen phosphate (0.01 mol/L), and trifluoroacetic acid (350:649.74:0.26, volume ratio) at a flow rate of 1.0 mL/min with the column temperature 35 °C. Under the optimum chromatographic conditions, the peak area of NBD‐d ‐glucosamine hydrochloride compared with its absolute value of the peak area of NBD‐d ‐glucosamine hydrochloride in a standard solution concentration range from 1.0 to 500.0 mg/L showed a good linear calibration (R = 0.9999). Recoveries, at spiked concentrations of 10.0, 40.0, and 500.0 mg/L, varied between 97.2% and 102.6% with relative standard deviations ranging from 0.4% to 1.5%. The present method provides sufficient sensitivity as reflected by the values of limit of detection (LOD) and limit of quantification (LOQ). LOD was determined from the signal‐to‐noise ratios (S/N) of NBD‐d ‐glucosamine hydrochloride peak of at least 3 in the recovery test at 0.02 mg/L, and the estimated LOQ was 0.06 mg/L (S/N = 10). The proposed method was successfully applicable to detect d ‐glucosamine hydrochloride in health foods and drugs containing a variety of complex materials.     

A survey of total hydrocyanic acid content in ready-to-eat cassava-based chips obtained in the Australian market in 2008

Cassava (Manihot esculenta Crantz) is a widely consumed food in the tropics that naturally contains cyanogenic glycosides (cyanogens, mainly composed of linamarin, acetone cyanohydrin, and hydrocyanic acid). If cassava is not adequately processed to reduce the level of cyanogens prior to consumption, these compounds can lead to the formation of hydrocyanic acid in the gut. Exposure to hydrocyanic acid can cause symptoms ranging from vomiting and abdominal pain to coma and death. In 2008, a survey of ready-to-eat (RTE) cassava-based snack foods was undertaken to determine levels of cyanogens measured as total hydrocyanic acid. This survey was undertaken in response to the New South Wales Food Authority being alerted to the detection of elevated levels of cyanogens in an RTE cassava-based snack food. This survey took 374 samples of RTE cassava chips available in the Australian marketplace. Significant variation in the levels of total hydrocyanic acid were observed in the 317 samples testing positive for cyanogens, with levels ranging from 13 to 165 mg of HCN equivalents per kg (mean value, 64.2 mg of HCN eq/kg for positive samples). The results from this survey serve as a timely warning for manufacturers of RTE cassava chips and other cassava-based snack foods to ensure there is tight control over the levels of cyanogens in the cassava ingredient. Evidence from this survey contributed to an amendment to the Australia New Zealand Food Standards Code, which now prescribes a maximum level for hydrocyanic acid in RTE cassava chips of 10 mg of HCN eq/kg, which aligns with the Codex Alimentarius Commission international standard for edible cassava flour.     

A stacked memory device on logic 3D technology for ultra-high-density data storage

We have demonstrated, for the first time, a novel three-dimensional (3D) memory chip architecture of stacked-memory-devices-on-logic (SMOL) achieving up to 95% of cell-area efficiency by directly building up memory devices on top of front-end CMOS devices. In order to realize the SMOL, a unique 3D Flash memory device and vertical integration structure have been successfully developed. The SMOL architecture has great potential to achieve tera-bit level memory density by stacking memory devices vertically and maximizing cell-area efficiency. Furthermore, various emerging devices could replace the 3D memory device to develop new 3D chip architectures.     

Hydroxyapatite-anatase-carbon nanotube nanocomposite coatings fabricated by electrophoretic codeposition for biomedical applications

In order to eliminate micro-cracks in the monolithic hydroxyapatite (HA) and composite hydroxyapatite/carbon nanotube (HA/CNT) coatings, novel HA/TiO₂/CNT nanocomposite coatings on Ti6Al4V were attempted to fabricate by a single-step electrophoretic codeposition process for biomedical applications. The electrophoretically deposited layers with difference contents of HA, TiO₂ (anatase) and CNT nanoparticles were sintered at 800°C for densification with thickness of about 7–10 μm. A dense and crack-free coating was achieved with constituents of 85 wt% HA, 10 wt% TiO₂ and 5 wt% CNT. Open-circuit potential measurements and cyclic potentiodynamic polarization tests were used to investigate the electrochemical corrosion behavior of the coatings in vitro conditions (Hanks’ solution at 37°C). The HA/TiO₂/CNT coatings possess higher corrosion resistance than that of the Ti6Al4V substrate as reflected by nobler open circuit potential and lower corrosion current density. In addition, the surface hardness and adhesion strength of the HA/TiO₂/CNT coatings are higher than that of the monolithic HA and HA/CNT coatings without compromising their apatite forming ability. The enhanced properties were attributed to the nanostructure of the coatings with the appropriate TiO₂ and CNT contents for eliminating micro-cracks and micro-pores.     

Preparation and characterization of a novel porous titanium scaffold with 3D hierarchical porous structures

This study aims to prepare a novel porous titanium (Ti) scaffold in order to improve the biocompatibility of the metallic implants. Porous Ti was produced by a Liquid foaming method and subsequent chemical treatments. It was found that the scaffold had three-dimensionally hierarchical porous structures with pore size ranging from nanometer to micrometer scale, and it also had activated surface. Mechanical test results showed that the scaffold also has sufficient compressive strength to meet the requirements of implantation. Protein adsorption results indicated that the novel scaffolds significantly enhanced the protein adsorption.     

汽车动力总成悬置耐久性模拟试验研究

探讨了悬置道路模拟实验中频响函数的建立和路谱迭代方法。以某款轿车的发动机液压悬置为研究对象,在试验场采集了悬置的道路载荷谱。通过基于远程控制参数技术（RPC）对发动机悬置道路载荷谱进行了重构,重构的道路载荷谱达到了预期的精度要求。论述了建立悬置路谱模拟试验的总载荷序列的方法。应用文中的方法,在MTS831试验台架上对液压悬置进行了道路模拟耐久性试验,试验结果表明,所采用方法可成功用于悬置耐久性试验。     

半主动液阻型橡胶隔振器动态性能测试与计算分析

设计并制造了一种解耦膜刚度可调的半主动液阻型橡胶隔振器,对其静态、动态特性进行了实验测试.建立了半主动液阻悬置动特性计算分析的集总参数模型,利用该模型计算分析了一半主动液阻悬置在低频大振幅激励下的动刚度和滞后角,计算结果和实验值的对比结果证明了模型的正确性.给出了半主动液阻悬置在解决汽车在怠速、巡航与粗糙路面激励下的驾驶员座椅振动问题的应用实例.该分析方法和结论有助于被动式液阻悬置和半主动液阻悬置的设计与开发.     

具有光学活性高性能高分子材料的研究进展

旋光性聚合物可以使通过它的偏振光发生偏转,在手性识别和对映体拆分、手性催化剂、液晶、生物医药、光学开关和非线性光学等领域展现出良好的应用前景。本文综述了几种利用旋光性单体缩聚合成具有光学活性高分子材料的方法,对所得聚合物的热稳定性、可溶性、旋光性等主要性能进行分析比较,得到一系列重要的结论,并对其影响机理进行讨论。在此...     

Baselines for carbon emissions in the Indian and Chinese power sectors: Implications for international carbon trading

The study examines the dynamics of carbon emissions baselines of electricity generation in Indian states and Chinese provinces in the backdrop of ongoing electricity sector reforms in these countries. Two Indian states—Gujarat and Andhra Pradesh, and three Chinese provinces–Guangdong, Liaoning and Hubei have been chosen for detailed analysis to bring out regional variations that are not captured in aggregate country studies. The study finds that fuel mix is the main driver behind the trends exhibited by the carbon baselines in these five cases. The cases confirm that opportunities exist in the Indian and Chinese electricity sectors to lower carbon intensity mainly in the substitution of other fuels for coal and, to a lesser extent, adoption of more efficient and advanced coal-fired generation technology. Overall, the findings suggest that the electricity sectors in India and China are becoming friendlier to the global environment. Disaggregated analysis, detailed and careful industry analysis is essential to establishing a power sector carbon emissions baseline as a reference for CDM crediting. However, considering all the difficulties associated with the baseline issue, our case studies demonstrate that there is merit in examining alternate approaches that rely on more aggregated baselines.     

A new technique for boosting efficiency of silicon solar cells

A new type of photovoltaic system with higher generation power density has been studied in detail. The feature of the system is a V-shaped module (VSM) with two tilted monocrystalline solar cells. Compared to solar cells in a flat orientation, the VSM enhances external quantum efficiency and leads to an increase of 31% in power conversion efficiency. Due to the VSM technique, short-circuit current density was raised from 24.94 to 33.7 mA/cm², but both fill factor and open-circuit voltage were approximately unchanged. For the VSM similar results (about 30% increase) were obtained for solar cells fabricated by using mono-crystalline silicon wafers with only conventional background impurities.