液相色谱–光谱图法定性确证食品中苯甲酸、山梨酸

建立液相色谱– 光谱图法定性确证食品中的苯甲酸、山梨酸.样品经提取后,以Agilent Poroshell 120 EC–C18色谱柱分离,2 mmol/L甲酸与20 mmol/L乙酸铵混合溶液–甲醇(体积比为95:5)为流动相洗脱,于230 nm波长检测,同时利用二极管阵列检测器全光谱扫描功能(190～400 nm,...     

微波消解-电感耦合等离子体质谱法（ICP-MS）测定淡水产品中多种金属元素

摘要：建立了微波消解-电感耦合等离子质谱（ICP-MS）同时测定淡水产品多11种金属元素的定量分析方法。比较了传统的湿法消解和微波消解两种消解方式对淡水产品测定影响。实验结果表明,微波消解方法不仅能够快速地将待测元素从淡水产品基体中释放出来,而且能够很好地保留在消解液中,待测元素的回收率较高。所建立方法测定了GBW10024（GSB-15）扇贝和GBW10051（GSB-29）猪肝标准物质,所得结果与标准值吻合度较高。采用微波消解-ICP-MS法测定市售的淡水产品中多种金属元素,其样品回收率在91.20%~110.81%。该方法快捷、准确、灵敏高,满足大批量淡水产品中金属元素分析测定要求,可为公安部门维护“食药环”领域安全稳定提供依据。     

A Riemannian submersion-based approach to the Wasserstein barycenter of positive definite matrices

In this paper, we introduce a novel geometrization on the space of positive definite matrices, derived from the Riemannian submersion from the general linear group to the space of positive definite matrices, resulting in easier computation of its geometric structure. The related metric is found to be the same as a particular Wasserstein metric. Based on this metric, the Wasserstein barycenter problem is studied. To solve this problem, some schemes of the numerical computation based on gradient descent algorithms are proposed and compared. As an application, we test the k-means clustering of positive definite matrices with different choices of matrix mean.     

A comparative study on wear and friction characteristics of phenolic composite coatings filled with different morphologies ZnO

In this paper, different morphologies ZnO (disk‐like, rod‐like, and nanoparticles) were introduced into phenolic composite coatings to comparatively investigate the tribological properties. The structural and morphological characterization was conducted with Raman spectroscopy, X‐ray diffraction, and scanning electron microscopy. The tribological performances of composite coatings were evaluated using ring‐on‐block tester under dry condition at room temperature. Experimental results indicated that composite coatings filled with 1 wt% ZnO micro‐disks possessed the optimal tribological performances. It was attributed to the strong interfacial interaction between ZnO micro‐disks and phenolic matrix induced by their specific polar structure. Moreover, different loads and sliding speeds were employed to further evaluate the tribological performances of ZnO micro‐disks/phenolic composite coatings. The outcome revealed that ZnO micro‐disks were potential anti‐wear fillers under harsh condition.     

对等式约束非线性规划问题的Hestenes-Powell增广拉格朗日函数的进一步研究

本文对用无约束极小化方法求解等式约束非线性规划问题的Hestenes-Powell 增广拉格朗日函数作了进一步研究．在适当的条件下,我们建立了Hestenes-Powell增广拉格朗日函数在原问题变量空间上的无约束极小与原约束问题的解之间的关系,并且也给出了Hestenes-Powell增广拉格朗日函数在原问题变量和乘子变量的积空间上的无约束极小与原约束问题的解之间的一个关系．因此,从理论的观点来看,原约束问题的解和对应的拉格朗日乘子值不仅可以用众所周知的乘子法求得,而且可以通过对Hestenes-Powell 增广拉格朗日函数在原问题变量和乘子变量的积空间上执行一个单一的无约束极小化来获得．     

一个新的填充函数

填充函数法是一种解无约束全局极小化问题的方法.这种方法的关键是构造填充函数,在已发表的文献中已经介绍了几种填充函数.在此介绍只含一个参数的填充函数,并且根据此填充函数提出了一种填充函数算法.给出了用这种填充函数法解几个测试问题的计算结果.     

NMR STUDIES ON POLYETHER-POLYURETHANE ZWITTERIONOMERS——CHAIN STRUCTURE AND PHASE SEPARATION

The ~1H and ~(13)C NMR spectra of polyether-polyurethancs (A) based on 4, 4'-diphenylmethanediisocyanate (MDI), N-methyl diethanolamine (MDEA), and polytetramethyleneoxide (PTMO)and the zwitterionomers derived from A with various degree of ionization was assigned by comparingwith model compounds. Phase separation of the samples was visualized through pulsed NMR investigations. The FIDsignals of these multiphase elastomers were recorded and decomposed by non-linear least squaresregression into fast Gaussian and slow exponential components assodated with the hard, the soft andthe interface respectively. Thus pulsed NMR gives both qualitative and quantitative informationabout the existence of multiphases and the relative amounts of materials in each phase.     

Dual-site fluorescent probe for highly selective and sensitive detection of sulfite and biothiols

A dual-site fluorescent probe that could discriminatively respond to Cys and HSO^3- through two emission channels was reported, and it could further applied in imaging biothiols in living cells.     

微生物传感器快速测定生化需氧量

利用微生物传感器快速测定水中生化需氧量。用该法对标准样品进行测定,测定结果的相对标准偏差为3.30%~4.67%(n=4),与标准值的相对误差在±5%之内。用该方法和经典稀释接种法对实际样品进行测定,该方法测定结果的相对误差为4.1%~11.3%。微生物传感器法能满足环境监测的要求。     

Metallogels Self‐Assembled from Linear Rod‐Like Platinum Complexes: Influence of the Linkage

Two linear rod‐like platinum complexes, which only differed in the linkage, were prepared. They both self‐assemble into metallogels in nonpolar solvents; however, a very big contrast was observed. Unexpectedly, a much weaker gel was acquired upon replacing the ester linkage by an amide group. The intermolecular hydrogen bonding offered by the amide motif leads to a different stacking fashion and mechanism. The results demonstrated herein contribute to the rational design of metallogels as well as other functional supramolecular materials.