An analysis of cubic approximation schemes for conic sections

In this paper a piece of a conic section is approximated by a cubic or piecewise cubic polynomial. The main tool is to define the two inner control points of the cubic as an affine combination, defined by [0, 1], of two control points of the conic. If is taken to depend on the weightw of the latter, a function (w) results which is used to distinguish between different algorithms and to analyze their properties. One of the approximations is a piecewise cubic havingG ⁴ continuity at the break points.     

The theoretical basis of column chromatography in multicomponent separations. Part 2: Peak capacity. Column systems with good selectivity

The selectivity of a column system, S, defined by equation 28, includes a variation coefficient (β) of plate number with capacity ratio which has a large influence on the peak capacity, as shown in Fig. 18. Some typical chromatograms are given. In order to predict S for a column system from Kovat's Index, equations 40 and 41 are given to calculate the constant of the carbon number rule for squalane at different temperatures or for different stationary phases. The specific retention value of heptane on squalane at different temperatures can be calculated from equation 42. The nonpolarity index, defined by equation 43, was used to calculate the retention value of heptane on various stationary phases. In liquid chromatography, the order of elution may be reversed by changing the composition of the eluent on the same chemically bonded silica (manufactured in China). The linear relations between the log retention values of different kinds of solutes or of a single solute on the silicas of different surface areas when using the same eluent are given.     

用高分辨质谱研究二茂铁类化合物

研究了八种N－二茂铁甲基苯胺衍生物的电子电离质谱（EI－MS），并与快原子轰击质谱（FAB－MS）作了比较，讨论了这些化合物的质谱特征。通过精确质量测量，确认了M^ -2 OH离子，并采用碰撞诱导裂解（CID）探讨了化合物质谱中主要离子间的关系。     

Radiation-induced polymerization of methyl methacrylate in microemulsion with high monomer content

γ-Ray-induced polymerization of methyl methacrylate was conducted in a microemulsion stabilized by a mixture of sodium of 12-acryloxy-9-octadecenoic acid (AOA) and sodium dodecyl sulfate (SDS) with various weight ratios at room temperature. The experimental data showed that the mixture of AOA and SDS with a weight ratio 2 was an efficient surfactant system for the microemulsion containing 38.6 wt% MMA and 5.5 wt% surfactant. The effects of MMA concentration and dose rate on the polymerization kinetics and particle size are discussed.     

大鼠脑组织中不同部位单胺类神经递质含量的HPLC测定

单胺类神经递质,多巴胺(DA)、去甲肾上腺素(NA)和肾上腺素(A)是哺乳动物和人类中枢重要的信息传递物质。了解脑组织中各部位单胺类神经递质的含量对于研究其生理功能、有关疾病的诊断和药物及手术疗效的评价均有重要的意义。     

New approach to calibrating conductivity meters in the low conductivity range

There is currently a major issue with the calibration of conductivity meters used for high purity water: the lack of availability of a reference material or reference methods for low conductivity ranges (conductivity below 1 S cm^–1 at 25.0 °C, resistivity >1 M cm at 25.0 °C). This paper describes the current status of conductivity measurements in high purity water. A new and improved approach, currently being investigated, should allow us to make the calibration of conductivity meters used for low conductivity ranges traceable to the SI.Milipore, Milli-Q and Elix are registered trademarks of Millipore Corporation.     

Unusual features of micellar diffusion

Diffusion coefficients of tetradecyltrimethylammonium bromide in aqueous solutions have been determined at 25, 95 and 135 °C using the Taylor dispersion technique. The diffusion coefficient exhibits a minimum at a surfactant concentration above the critical micelle concentration (CMC). The results are interpreted in terms of electrostatic coupling and rapid exchange between micelle, surfactant monomer and counterions.     

Determination of triclosan in foodstuffs

A reverse-phase high-performance liquid chromatographic (RP-HPLC) method coupled with an ultraviolet detector was developed to determine triclosan which had migrated into foodstuffs from packaging materials. The method includes extraction with hexane, followed by evaporation to dryness and residue re-dissolution in ACN 90%. Chromatographic separation was performed with a Kromasil 100 C18 column (15 cm x 0.4 cm ID, 5 microm particle size) at 30 degrees C and using ACN and water as mobile phases. Regarding recoveries, good results (higher than 83% and lower than 112%) were obtained for the three representative food matrixes selected (orange juice, chicken breast meat, and Gouda cheese).