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991.
目的建立一种用于壳寡糖含量检测的乙酰丙酮-分光光度检测方法。方法采用浓盐酸将含有壳寡糖的样品彻底水解,用6 mol/L的氢氧化钠将水解液调成中性,采用乙酰丙酮法于525nm处测定吸光度,代入回归方程,测定壳寡糖含量。结果壳寡糖含量在0.02~0.12 mg/mL浓度范围内时,其含量与吸光度之间呈良好线性关系,r2=0.999。该方法的加样平均回收率为99.25%,精密度和稳定性试验的相对标准偏差RSD分别为0.346%和0.145%,。结论该方法灵敏、准确、简便,可作为一般生产企业进行壳寡糖含量的常规测定。 相似文献
992.
993.
There is no systematic procedure described in the literature to establish a robust and accurate reference method for determining the moisture content in any solid food product. In this paper, we are proposing a new approach based on simultaneous thermogravimetry and differential thermal analysis (TG–DTA), with data for several amorphous food powders that result from spray-drying, freeze-drying or extrusion. In the first step, by heating a representative sample of about 20 mg at 2 °C/min we would detect the temperature and the mass loss at the inflection point that characterises, if there is an inflection, the end of the drying and the onset of chemical reactions. In cases of not too much sensitive products, the mass loss at the inflection may be considered as a good estimation of the moisture content. At 2 °C/min heating rate, the inflection temperature Ti is an indicator that allows estimating the optimal isothermal drying temperature Td about 15–30 °C below Ti, depending on the product sensitivity to heat treatments and the kinetics of water molecule diffusion through the amorphous matrix. Then, a series of three isothermal drying are performed at about Td−12 °C, Td and Td+8 °C, and a simple multilinear model allows calculating the best oven temperature to achieve the optimal moisture content determination in 2 h. This procedure is described and results are shown for several dehydrated food products: milk, coffee, cereal and pet food. This fast procedure may be applied either for establishing optimal oven conditions for most amorphous new products or for revising conditions that have been established in the past but are not robust enough for several ones. 相似文献
994.
68种保健食品常用原料植物甾醇含量研究 总被引:3,自引:0,他引:3
目的对68种中草药植物甾醇的含量进行检测,为进一步认识和利用中草药中的有效成分提供依据。方法选择目前保健食品原料中批准可用的中草药68种,按照本实验室建立的方法,用气相色谱法分析了β-谷甾醇、菜油甾醇、豆甾醇、谷甾烷醇的含量,并计算各成分占总量的百分比。结果保健食品原料中可用的68种中草药中,植物甾醇的总含量从5.2mg/100g(诃子、鲜白茅根)到321.4mg/100g(蒲黄)。来源于植物的"花"、"种子"、"皮"等部位的样品中植物甾醇的含量较高。本次研究发现所有检测样品中都含有β-谷甾醇,且在绝大多数样品中此成分的含量最多;传统用来降血脂、抗炎的中草药中均含有较高的植物甾醇。结论 68种中草药中均含有一定量的植物甾醇,这可能是中药发挥作用的功能成分之一。 相似文献
995.
研究了Mg含量、冷却速度、固溶处理对Al-6.8Mg-0.3Mn、Al-3.8Mg-0.3Mn两种合金力学性能的影响。结果表明,随着Mg含量提高,晶界相增多。当Mg含量提高到6.8%时,晶界出现网状组织;随着Mg含量升高,合金强度提高,塑性下降;通过砂型铸造空冷、金属型铸造空冷、金属型铸造淬火来实现不同的冷却速度,发现金属型淬火试样的金相组织中,在晶界附近没有析出网絮状或颗粒状第二相,而强度和伸长率要高于其他两种工艺。两种合金经过430℃×60h固溶处理后,合金的综合力学性能得到大幅度提高。Al-6.8Mg-0.3Mn金属型铸造空冷试样固溶后抗拉强度由280MPa提高到335MPa,伸长率由10.4%提高到20%。 相似文献
996.
997.
PIM-SM (Protocol Independent Multicast-Sparse Mode) is a main multicast routing protocol in the IPv6 (Internet Protocol version 6). It can use either a shared tree or a shortest path tree to deliver data packets, consequently the multicast IP lookup engine requires, in some cases, two searches to get a correct lookup result according to its multicast forwarding rule, and it may result in a new requirement of doubling the lookup speed of the lookup engine. The ordinary method to satisfy this requirement in TCAM (Ternary Content Addressable Memory) based lookup engines is to exploit parallelism among multiple TCAMs. However, traditional parallel methods always induce more resources and higher design difficulty. We propose in this paper a novel approach to solve this problem. By arranging multicast forwarding table in class sequence in TCAM and making full use of the intrinsic characteristic of the TCAM, our approach can get the right lookup result with just one search and a single TCAM, while keeping the hardware of lookup engine unchanged. Experimental results have shown that the approach make it possible to satisfy forwarding IPv6 multicast packets at the full link rate of 20 Gb/s with just one TCAM with the current TCAM chip. 相似文献
998.
根据广电的OTT(over the top)业务,对流媒体支撑系统中的电视直播/时移服务平台、视频点播等平台进行设计。在这个设计方案中,时移业务采用微分片技术,目的是让用户的体验效果更佳;内容分发网络系统采用双向化的设计方式,任意节点间可进行内容分发,可以缓解骨干网的压力;利用HTTP Referer特性,能有效地防止非法用户进行访问。 相似文献
999.
Amit K. Shah Bonnie A. Avery Christy M. Wyandt 《Drug development and industrial pharmacy》2013,39(9):907-916
Content analysis and stability studies were performed for the commercial products of St. John's wort. Six marketed formulations were analyzed for their hypericin and pseudohypericin content. These products were standardized to contain 0.3% hypericin. Results revealed total hypericin as 7.72–38.57% of the labeled claim with varying concentrations of pseudohypericin. Stability studies were carried out under three different storage conditions: 1) 25 ± 2°C, 60 ± 5%RH for six months, 2) 40 ± 2°C, 75 ± 5%RH for six months, and 3) 50°C for one month. Tablet formulations were also analyzed for their hardness and friability. Stability studies revealed significant decrease in the content of the marker compounds with time. 相似文献
1000.
Offloading cellular traffic through mobile social networks has arisen as a promising way for relieving cellular networks. Prior studies mainly focused on caching data in a number of pre-selected helpers. However, such a strategy would fail when mobile users enter and leave the target area over time. In this paper, we examine the research decisions and design tradeoffs that arise when offloading cellular traffic in such a dynamic area of interest, referred to as a MobiArea, and we design an offloading framework, MobiCache, for maximizing cellular operators’ revenues and minimizing the overhead imposed on mobile devices. On the user side, we propose a content floating-based cooperative caching strategy that caches data in geographical floating circles, instead of selected helpers in previous studies, to cope with the dynamics. A geographical routing scheme is designed for delivering data and queries towards floating circles. We also develop a cache replacement scheme to improve caching cost-effectiveness inside floating circles. On the operator side, query history and feedback are maintained for cellular operators to optimize framework parameters that maximize their revenues. Extensive trace-driven simulations show that, compared with a state-of-the-art scheme, MobiCache offloads up to 52% more traffic with 15% shorter delay and 6% less forwarding cost. 相似文献