An efficient method for constructing nonorthogonal localized molecular orbitals

A new method for constructing nonorthogonal localized molecular orbitals (NOLMOs) is presented. The set of highly localized NOLMOs is obtained by minimization of the spread functional starting from an initial set of canonical orthogonal molecular orbitals. To enhance the stability and efficiency, the centroids of the NOLMOs are constrained to be those of the corresponding orthogonal localized molecular orbitals (OLMOs), which are obtained with the Boys criterion in advance. In particular, these centroid constraints make the optimization for each NOLMO independent of the others, which is an attractive feature for application to large systems. The minimization with the constraints incorporated through the multiplier-penalty function method is stable and efficient in convergence. While exhibiting the classical bonding pattern in chemistry and sharing a spatial distribution similar to that of the corresponding OLMOs, the obtained NOLMOs are more compact than the corresponding OLMOs with about 10%-28% reduction in the value of the spread functional and devoid of the troublesome "orthogonalization tails."     

An attempt on the VOC oxidation using mechanically activated catalyst

A catalytic action of the mechanochemical products of copper hydroxocarbonate with calcium carbonate was investigated in n-butyl alcohol oxidation tests. The solid products of high-energy milling were identified using thermogravimetry supplemented by X-ray diffraction method. It was shown that the mechanical activation induces more effective tested catalyst because it promotes the alcohol conversion at lower temperatures than that unmilled one. This revised version was published online in July 2006 with corrections to the Cover Date.     

Breakup of a Multiple Emulsion Drop in a Uniform Electric Field

The steady deformation and breakup of emulsion drops in a uniform electric field are considered experimentally. Due to the low volume fraction of inner drops, the emulsions can be effectively assumed as Newtonian fluids with spatial nonuniformity. The measurements of the electrical properties show that the oil-in-water (o/w) emulsion drop behaves like a conducting drop. On the other hand, the water-in-oil (w/o) emulsion drops can be regarded as inhomogeneous leaky dielectric drops. It is found that the viscosity ratio is not an important parameter within the small deformation limit and breakup mode of the o/w emulsion drops. In the case of w/o emulsion drops, however, the breakup mode depends on the viscosity ratio. Inherent nonuniformity of the emulsion drops makes drop more deformable and unstable. The tip-streaming is the dominant breakup mode of o/w emulsion drops when the nonuniformity of drop phase is appreciable. Copyright 1999 Academic Press.     

Synthesis and Second‐Order Nonlinearities of Chiral Prolinol‐Substituted Chromophores

A new series of thiophene‐ and furan‐containing chromophores with a chiral prolinol donor and a sulfone acceptor has been synthesized. The UV‐vis absorptions, second‐order nonlinear optical properties, and X‐ray crystal structures are described.     

菲林B近红外分光光度法测定维生素C

在pH 3的三氯乙酸酸性介质中,菲林B可以定量地将还原型维生素C氧化成脱氢型维生素C,利用脱氢型维生素C在920 nm处有最大吸光度,测定其含量,建立了一种测定维生素C的新方法,并研究了影响反应的各种因素。该方法对维生素C的检出限为0.17 mg/L;线性范围为0.5~10 mg/L,对水果中维生素C含量测定的RSD<2.31%;回收率为99.7%~101.1%,比2,4-二硝基苯肼分光光度法测定结果的相对偏差<±1.6%。     

Remarkably efficient oxidative coupling of N,N-dialkylarylamines in water mediated by cerium(IV) ammonium nitrate

A highly effective, economical, and environmentally friendly method using of CAN as oxidant and water as solvent for oxidative coupling of N,N-dialkylarylamines was reported.     

Asymmetric Diels-Alder Reactions of Chiral Menthyl α-Sulfinylacrylates

Introducing two chiral auxiliaries, sulfoxide and menthol, into an acrylate would have either matched or mismatched pair systems. The presence of chiral menthol in α-sulfinylacrylates can change the diastereoselectivity from 24% d.e. to a single diastereomer by manipulation of the double asymmetric strategy.     

乙苯脱氢铁系催化剂的穆斯堡尔谱研究

用穆斯堡尔法对乙苯脱氢铁系催化剂在反应条件下进行了研究。结果表明,反应前催化剂中的铁主要以α-Fe_2O_3和α-FeOOH的形式存在,在反应中主要组分为Fe_3O_4。用K_2CO_3和α-Fe_2O_3在高温下加热可以生成KFeO_2,后者在室温下很不稳定,在同样条件下很容易转化为Fe_3O_4。但钾的存在可促进催化剂中Fe~(3+)还原为Fe~(2+),有利于电子的交换,对催化活性起着助催作用。     

原子发射光谱法间接测定黄连素片剂中盐酸小檗碱的研究

本文提出了离子对-原子发射光谱间接测定黄连素片剂中盐酸小檗碱的新方法。发现用1,2-二氯乙烷作萃取剂效果最佳。用此怯测定实际样品的结果与药典法一致,相对误差为0.61％,单一测定的相对标准偏差为0.67％。本法还可在盐酸普鲁卡因共存下单独测定盐酸小檗碱。方法可靠、适用,选择性较好。     

生物质裂解产物的制备及HPLC检测其成分的虚拟仿真实验开发

In order to improve university laboratory teaching and practical education under the background of information technology, as well as overcome the difficulty for practical training, develop a virtual simulation experiment platform for rapid pyrolysis of natal materials and high-performance liquid chromatographic (HPLC) detection of its components. The experiment integrates the actual operation process of the plant to produce cleaved products by rapid pyrolysis of biomass with HPLC detection. The virtual experiment is divided into biomass sample pretreatment, rapid biomass pyrolysis, bio-oil extraction, and HPLC determination of complex components, making the biomass cleavage workshop "real" through simulation. This virtual simulation experiment fully integrates the utilization of biomass resources and basic chemistry courses (such as organic chemistry, instrumental analysis, chemical engineering principles, etc.), which are widely involved in agricultural and forestry majors with advantageous characteristics value.