空间均匀有理张力样条参数曲线

引入了基于双曲样条函数的、具有张力参数的空间有理等距节点样条参数曲线，给出了这种曲线在每个样条子区间上为挠曲线段(即非平面曲线)的充分必要条件；分析了这种挠曲线段没有尖点、重结点和泛拐点的特性；因而在用于空间曲线几何造型时可避免奇异性．当张力参数趋于零或趋于无穷大时的极限曲线，分别是等距节点的有理三次B样条曲线和其控制多边形，故张力参数可用于调节曲线的光顺性．还给出了将权系数用于曲线插值的一种方法．     

Lateral error recovery for media streaming in application-level multicast

We consider media streaming using application-level multicast (ALM) where packet loss has to be recovered via retransmission in a timely manner. Since packets may be lost due to congestion, node failures, and join and leave dynamics, traditional "vertical" recovery approach where upstream nodes retransmit the lost packets is no longer effective. We therefore propose lateral error recovery (LER). In LER, hosts are divided into a number of planes, each of which forms an independent ALM tree. Since error correlation across planes is low, a node effectively recovers its error by "laterally" requesting retransmission from nearby nodes in other planes. We present analysis on the complexity and recovery delay on LER. Using Internet-like topologies, we show via simulations that LER is an effective error recovery mechanism. It achieves low overhead in terms of delivery delay (i.e., relative delay penalty) and physical link stress. As compared with traditional recovery schemes, LER attains much lower residual loss rate (i.e., loss rate after retransmission) under a certain deadline constraint. The performance can be substantially improved in the presence of some reliable proxies.     

量器不确定度在实验室标准溶液配制过程中的评定

摘 要: 目的 不确定度对移液管、移液枪与容量瓶配制标准溶液时准确性评价,为量器选择提供参考,加强实验室对量器准确性与实验人员操作水平的监管。方法 评定并比较量器3个不确定度分量（测量重复性、校准与温度效应）,评定并比较不同标准溶液配制方案量器引入的不确定度。结论 量器测量重复性不确定度结果表明：移液管对实验人员的操作要求更高,移液枪更易操作;测量重复性实验实现了量器定期标定或校准;移取不同体积液体时,移液管与移液枪有不同的优先选择;定容时优先选用小量程容量瓶;标准储备液与标准中间液选用移液管与容量瓶配制,标准工作曲线可完全用移液枪配制。     

A novel label-free voltammetric immunosensor for the detection of α-fetoprotein using functional titanium dioxide nanoparticles

A highly sensitive label-free voltammetric immunosensor was developed based on the functional titanium dioxide nanoparticles (PV-NTiP), which was prepared by capping 1,1′-bis-(2-phosphonoethyl)-4,4′-bipyridinium dibromide (PV) on the surface of the titanium dioxide nanoparticles (NTiP) with covalent attachment. The PV-NTiP has prominent biocompatibility, good electron transfer ability, primarily excellent adsorption, large specific surface area and positively charged environment. As a result, the negatively charged gold nanoparticles (NGP) could be adsorbed on the PV-NTiP modified electrode surface by electrostatic adsorption, and then to immobilize α-1-fetoprotein antibody (anti-AFP) for the assay of α-1-fetoprotein (AFP). The fabricated procedures and electrochemical behaviors of the immunosensor were characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The anti-AFP/NGP/PV-NTiP modified electrode was sensitive to AFP in linear relation between 1.25 and 200 ng/mL with the correlation coefficient of 0.9982, and the detection limit (S/N = 3) is 0.6 ng/mL under the optimal conditions. In addition, the proposed immunosensor exhibits good sensitivity, selectivity, stability and long-term maintenance of bioactivity and it may be used to immobilize other biomoleculars to develop biosensor for the detection of other antigens or biocompounds.     

肉品中β-受体激动剂类药物残留检测 技术研究进展

肉品中β-受体激动剂类药物残留问题严重影响着人体健康。近几年来暴露出来的肉品中β-受体激动剂类药物残留事件层出不穷, 为了加强监控, 越来越多的检测方法被建立起来, 极大地提高了肉品中β-受体激动剂类药物残留检测的效率。本文综述了检测肉品中β-受体激动剂类药物残留的色谱法、酶联免疫法、胶体金法和其他一些新方法的研究进展, 以及我国现行的β-受体激动剂类药物残留标准检测方法。对现有的检测方法的优缺点和发展阶段作了归纳总结, 并对β-受体激动剂类药物残留检测方法发展的方向提出了一些展望。未来的发展主要是一些特异性和灵敏度更高的快检方法和样品前处理更加简化的液质色谱联用法。     

葡萄酒中多糖的研究进展

多糖是构成葡萄酒中大分子物质的主要成分之一,其含量及组成对葡萄酒质量产生重要的影响.对葡萄酒中常见多糖的来源、葡萄酒酿造过程中多糖的变化、多糖对葡萄酒感官影响和多糖的检测方法等方面进行阐述,对未来这一领域的研究进行了展望.     

碳纤维负载TiO2光催化薄膜的制备及其性能

 以PAN基碳纤维(CF)为基体,钛酸丁酯为前驱体,通过溶胶-凝胶浸渍涂覆法将TiO2负载于经过表面修饰的CF上,制备CF负载的TiO2光催化薄膜。采用扫描电子显微镜（SEM）和X射线衍射仪（XRD）表征了制备材料的形态结构,通过超声震荡清洗测试了CF对TiO2的负载牢度,以质量浓度为80 mg/L的酸性橙Ⅱ溶液为目标降解物,测试了材料在紫外线光照下的催化性能。结果表明：溶胶浓度影响制备材料的形态结构、CF对TiO2的负载率及负载牢度;溶胶浓度和退火温度对制备材料的催化活性有明显的影响。Ti浓度为0.5 mol/L的溶胶制备的TiO2/CF负载牢度好,负载率高,催化活性好。     

叔丁基对苯二酚对小鼠肠道菌群的影响

目的 研究食品添加剂叔丁基对苯二酚(tert-butylhydroquinone, TBHQ)对小鼠肠道菌群的影响。方法 BALB/c小鼠随机分为空白对照组和TBHQ处理组, 分别饮用纯水和TBHQ溶液(200 mg/L)。干预5周后, 利用酶联免疫吸附试验(enzyme linked immunosorbent assay, ELISA)测定小鼠血液样本炎症因子水平; 收集两组小鼠的粪便, 利用16S rDNA扩增子高通量测序分析肠道微生物群落结构和组成变化, 判断TBHQ对肠道菌群的影响。结果 与对照组相比, TBHQ处理显著降低了小鼠肠道疣微菌门(Verrucomicrobia)、拟杆菌门(Bacteroidetes)、阿克曼氏菌(Akkermansia)、瘤胃球菌属(Ruminococcus)等菌的相对丰度, 提高了厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)、毛罗菌属(Lachnospira)、螺杆菌属(Helicobacter)等微生物的相对丰度。结论 本研究剂量TBHQ显著影响了小鼠的肠道菌群组成, 该变化对机体健康的影响有待进一步研究。     

冲泡模式对祁门红茶主要生化成分及抗氧化能力的影响

目的 为了解不同冲泡模式对祁门红茶(祁门工夫、祁红香螺、祁红毛峰)品质及抗氧化能力的影响。方法 从审评模式和品饮模式角度,通过测定茶汤中人体必需金属元素含量、呈味物质含量、滋味、色度和抗氧化能力,对品质和抗氧化差异进行研究。结果 冲泡模式的不同会导致红茶品质、抗氧化能力有显著差异。单杯短时多次冲泡茶汤中的有效成分含量更高,其中总儿茶素、咖啡碱、总氨基酸、人体必需金属元素含量分别是审评模式的1.95、2.17、1.46、1.49倍,滋味品质较优,抗氧化能力更强。结论 相比审评模式冲泡,单杯短时多次冲泡更有利于茶叶有效成分的溶出,且前3泡(共2 min)较好,第2次冲泡40 s内含物质最丰富。