252 research outputs found

    Identification of Colorants in Food by Surface-enhanced Raman Spectroscopy and Wavelet-based Reverse Search

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    使用金纳米粒子为增强因子的表面增强拉曼光谱技术,通过连续小波变换将拉曼光谱信号转化到小波空间(墨西哥帽小波作为小波基)。该步骤能够减轻信号中基线; 变化及随机噪音的影响并找到峰位置和最佳小波尺度系数。依据小波空间中的信息,对混合物光谱及标准谱光谱进行反向搜索得到反向搜索匹配系数(Revere; match quality,; RMQ),作为判断混合物中目标成分是否存在的依据。该算法可对混合物中的目标物质进行准确定性,并已成功应用于多种食品中色素鉴定。食品中色素的检出率; 达到99%,且结果稳健,其效果明显优于传统的命中质量系数法(Hit quality index,; HQI)。这证实了小波空间反向搜索方法是一种快速而准确的拉曼光谱定性算法。In this study, a gold nanocrystal colloid was used as the enhancement; factor for surfaceenhanced Raman scattering (SERS). Raman spectra were; transformed by continuous wavelet transform (CWT),and Mexican hat; wavelet were chosen as the wavelet basis. This procedure could be used; to alleviate the influence of baseline variations and random noise,and; find peak positions and the best scale wavelet coefficients of signal.; Reverse search method was proposed to compare the spectrum of an unknown; sample with a spectrum of standard using the information in wavelet; space. Reverse match quality (RMQ) could be obtained automatically to; determine whether a substance is present. It was used to identify; colorants in a variety of food successfully. The colorants could be; identified with 99 percent accuracy. It shows a better performance; compared with traditional hit quality index (HQI). The study confirmed; that the wavelet-based reverse search is feasible and accurate in; qualitative analysis.国家自然科学基金资助项目; 国家重大科学仪器设备开发专

    鲁米诺电致化学发光机理的研究

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    The electrochemiluminescence (ECL) of the luminol in aqueous alkaline solu tion has been studied using cyclic voltammetry, potential step tecdrique and time resolved UV/Vis spectroscopy. The results of the electrochemical experimens showed that the ECL of the luminol can carry out in the potential region of oxygen adsorption also and lead us suggest a new light-endtting pathway for the bonol on which the reaction between some of the luminol radical Anons and the adsorbed superokide radical sndtaneously gener ated in the anodic oxidation process yields excited 3-drinophthalate, the light emitting species. The results of the time resolved spectroscopic experiments manifested that the formation of the polymeric film produced by the luminol radical anions is one of important faetors decreasing the ECL of the luminol

    水飞蓟素固体分散体的制备及5种成分的溶出度

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    目的制备水飞蓟素固体分散体,并评价5种成分的溶出度。方法以F68与PVPk30为联合载体,溶剂熔融法制备固体分散体。再考察联合载体比例、药物-载体比例对水飞蓟宾、异水飞蓟宾、水飞蓟宁、水飞蓟亭、花旗松素溶出度的影响。结果最佳条件为联合载体比例1∶3,药物-载体比例1∶5。固体分散体中5种成分的溶出度显著高于原料药和物理混合物(水飞蓟素-载体)中。结论固体分散体可显著提高水飞蓟素中有效成分的溶出度。福建省自然科学基金项目(2015J01491

    普鲁兰基肿瘤靶向性纳米粒子的制备、稳定性和体外释放

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    背景:普鲁兰多糖以其独特的优点在纳米递药系统领域受到越来越多的关注,但是,以普鲁兰多糖为材料进行改性制备的肿瘤靶向的纳米药物载体仍有待进一步研究与开发。目的:观察纳米粒子和载药纳米粒子的体外稳定性及所包载药物的释放特征,初步评价其作为纳米药物载体的潜力。方法:应用透析法制备乙酰普鲁兰叶酸偶合体纳米粒子,以表阿霉素为模型药物,制备乙酰普鲁兰叶酸偶合体/表阿霉素载药纳米粒子(FPA/EPI),应用储存法考察其稳定性,应用透析袋法观测体外释放特征。结果与结论:乙酰普鲁兰叶酸偶合体纳米粒子和FPA/EPI的粒径分别为(204.2±10.9)nm和(273.4±11.0)nm,在蒸馏水和体积分数10%胎牛血清中表面电位均较低,乙酰普鲁兰叶酸偶合体纳米粒子在水溶液中粒径1年内未见显著改变。载药纳米粒子对所包载的药物表阿霉素进行很好地释放,pH5.0磷酸盐缓冲液中释放速度明显高于pH7.4;乙酰普鲁兰叶酸偶合体纳米粒子和FPA/EPI制备容易,稳定性好,初步说明了两种粒子可望成为新型肿瘤靶向药物递药系统

    Research Progress of Metal Material Liquid Forming Technology

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    随着汽车工业的迅速发展以及市场竞争对铸件质量要求的提高,推动了金属材料液态成型技术发展。从20世纪70年代压铸技术的广泛运用,到90年代挤压铸造技术的不断完善,随后挤压压铸技术不断创新,使液态成型技术向多学科渗透融合发展,应用领域不断拓展,铸件用量逐年上升。重点介绍了压铸、挤压铸造、挤压压铸这三种重要的成型技术发展以及取得的最新成果。With the rapid development of auto industry and the market competition on the increase of the requirement of the casting quality,the development of metal material liquid forming technology was promoted.From the extensive use of the die casting technology in the nineteen seventies to constant maturity of the 90's the squeeze casting technology,and then the continuous innovation of squeezing die casting,the liquid forming technology for multidisciplinary permeated and developed,application area continued to expand,and casting quantities increased year by year.The development and the latest achievements of three kinds of important forming technologies(die casting,squeezing casting and squeezing die casting) were mainly introduced.贵州省(贵阳市)工业攻关项目(黔科合GY字[2012]3004;筑科合同[2012101]2-13号

    估计葡萄糖处置率与冠状动脉狭窄严重程度关系的横断面研究

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    目的探讨估计葡萄糖处置率(eGDR)与冠心病(CAD)严重程度的关联。方法采用以医院为基础的横断面研究设计,纳入因疑似冠心病而接受冠状动脉造影检查的患者共1 258人(平均年龄:62(53~68)岁;男性占53.9%)。按照eGDR公式计算胰岛素抵抗水平(IR):eGDR =21.158 - [0.09×腰围(WC, cm)] - [3.407×高血压(hypertension, 是/否)] - [0.551×糖化血红蛋白(HbA1c, %)]。根据eGDR三分位数对研究对象进行分组。冠心病的严重程度由狭窄血管的数量决定: 无明显CAD组(所有冠脉狭窄均<50%,n=704),单支血管CAD组(只有一条受累的主要冠脉狭窄≥50%,n=205),多支血管CAD组 (两条或两条以上受累的主要冠脉存在狭窄≥50%,n=349);以无明显CAD作参照,采用多因素logistic回归模型分析eGDR与CAD严重程度之间的关联。采用限制性立方样条分析eGDR和CAD在整个eGDR范围内的线性关联。采用亚组分析评估不同糖尿病状态下eGDR和CAD严重程度之间的关联。受试者工作特征(ROC)曲线分析eGDR对提高CAD筛查模型的价值。结果eGDR降低与CAD严重程度的风险增加显著相关。(OR:2.79;95%CI:1.72~4.55;P<0.001)。多因素logistic回归模型中,eGDR最低分位(T1)的个体患多支血管CAD的风险是eGDR最高分位(T3)的2.79倍。(OR:2.79;95%CI:1.72~4.55;P<0.001)。限制性立方样条分析显示,eGDR与CAD以及多支血管CAD之间存在负线性关联(P-linearity<0.05)。在非糖尿病患者中,与参照组(T3)相比,T1组患CAD和多支血管CAD的风险显著增加,OR分别为1.42 (95% CI:1.00~2.01;P<0.05)和1.86 (95%CI:1.21~2.86;P<0.05)。而在糖尿病患者中未发现此关联有统计学意义(P>0.05)。ROC曲线分析,eGDR加入到CAD传统筛查模型中时,AUC、IDI、NRI的结果显示,模型对CAD和多支血管CAD的筛查有显著改善。结论eGDR与CAD及CAD严重程度呈负相关。eGDR作为一种无创且易于获取的非胰岛素测量指标,具有筛查大规模人群中CAD严重程度的潜在价值

    关于“经济发展方式转变进程中的财税政策”的探讨(笔谈)

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    转变经济发展方式是当前中国的热门话题,而上海在城市发展中又肩负着率先转变的重要任务,在这一意义和背景下,2010年4月24日由上海金融学院学院主办、上海金融学院公共经济管理学院承办的“《中国城市财政发展报告2009/2010:促进‘两个中心’建设的上海城市财政》首发式暨‘经济发展方式转变进程中的财税政策’论坛“在我校举行。与会专家围绕经济发展方式转变进程中的财税政策的“趋势与目标“、“机遇和挑战“、“实施方略“和“地方实践“等四个专题进行研讨,各抒己见,智慧交锋。现将其真知灼见整理摘要与读者分享,以期待更多学者共同关注当前经济发展方式转变进程中的财税政策

    First Sagittarius A* Event Horizon Telescope Results. VIII. Physical Interpretation of the Polarized Ring

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    In a companion paper, we present the first spatially resolved polarized image of Sagittarius A* on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3 mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%–28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87*, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of Sgr A* (equivalent to ≈46° ± 12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow

    由二氧化碳制备乙酸

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