Symmetry factoring of the characteristic equations of graphs corresponding to polyhedra

A systematic procedure is described which uses two-and three-fold symmetry elements in graphs to reduce their adjacency matrices to lead to corresponding factorings of their characteristic polynomials. A graph splitting algorithm based on this matrix reduction procedure is described. Applications of these methods to the factoring of the characteristic polynomials of 28 polyhedra with nine or less vertices are given. General expressions for the eigenvalues of prisms, pyramids, and bipyramids in terms of the eigenvalues of their basal or equatorial regular polygons are calculated by closely related matrix methods.     

Improved procedure for the preparation of deoxynucleoside phosphoramidites: Arylphosphoramidites as new convenient intermediates for oligodeoxynucleotide synthesis

A simplified procedure for the preparation of deoxynucleoside methyl- and arylphosphoramidites is described. Both types of phosphoramidites can be conveniently activated by N-methylaniline trifluoracetate for their use in oligodeoxynucleotide synthesis.     

Determination of organophosphorus insecticides,their oxygen analogs and metabolites by high pressure liquid chromatography

Summary A convenient procedure for the extraction and determination of three organophosphate insecticides, their active oxygen analogs, and their inactive metabolites in biological tissues is described. The utility of this technique is demonstrated by measurement of thein vitro biotransformation of both parathion and chlorpyrifos by mouse hepatic microsomes.     

Synthesis, characterisation and high-performance liquid chromatography of C6-C16 dicarboxylyl-mono-coenzyme A and -mono-carnitine esters.

The synthesis and purification of the mono-coenzyme A and mono-carnitine esters of the homologous series of straight-chain even-numbered dicarboxylic acids (C6-C16) is described. The corresponding 3-hydroxyacyl- and 2-enoyl-CoA esters were prepared enzymatically. A reversed-phase high-performance liquid chromatographic (HPLC) system for the analysis of the intact CoA esters is described and their chromatographic behaviour documented. Reversed-phase HPLC systems for the analysis of the 4-bromophenacyl derivatives of the dicarboxylyl-mono-carnitines and the 4-nitrobenzyl derivatives of the free acids are also described. Some preliminary studies of the metabolism of [U-14C]hexadecanedionoyl-mono-CoA by rat liver peroxisomes and rat skeletal muscle mitochondria are described illustrating the application of these methods.     

Über die Reaktion von Phenolen mit N-substitutierten Maleinimiden

The Reaction of Phenols with N-substituted Maleinimides Phenoxysuccinimides are formed by the base catalysed addition of phenols to N-substituted maleinimides. In the presence of catalytic amounts of tertiary aliphatic amines yields as high as 90% are obtained. A series of adducts of mono-and di-phenols to mono- and bismaleinimides is described. Pure phenoxysuccinimides are stable compounds but the basic catalysts of their formation give rise to their decomposition into the phenolic component and oligomeric maleinimide. A nucleophilic reaction mechanism both for the formation and the decomposition is discussed. A new crosslinked addition polymer from a diphenol and a bismaleinimide with a surprisingly high heat stability is described.     

Analysis of ethoxylated alcohol surfactants in water by HPLC

Summary An HPLC procedure for the determination of linear alcohol polyethoxylates in surface water, waste water, and detergents is described. After extraction of the alcohol ethoxylates into an organic phase the alcohol ethoxylates are derivatized with phenyl isocyanate to apply an UV detection. A reversed-phase HPLC procedure is used to separate different ethoxylate species by their different alkyl chain length. A normal phase procedure is employed to separate alcohol polyethoxylates by their different number of ethoxylate groups in the molecule.     

Simultaneous determination by GC-MS-SIM of o-, m-, p-hydroxyphenylacetic acid, 3:4-dihydroxyphenylacetic acid and homovanillic acid in biological samples using a common selected ion

A GC-MS-SIM method is described for the simultaneous determination of five acid metabolites, o-, m-, and p-hydroxyphenylacetic acid, 3:4-dihydroxyphenylacetic acid and homovanillic acid in biological samples using a common selected ion for all the acids. The TMS ethers of methyl or ethyl esters of these compounds have a common ion at m/e 179 which is used for their quantitation by selected ion monitoring. The molecular ion at m/e 238 of the three monohydroxy phenylacetic acids, which is also the M-30 ion for homovanillic acid, is also used for their quantitation. The GC conditions for their separation, the relative sensitivities and some advantages of TMS ethers over other derivatives are described. The application of this method to biological samples is illustrated by data on human urine and plasma.     

Determination of boron and nitrogen in boron nitride

Improved techniques are described for the determination of boron and nitrogen in pure boron nitride. Controlled fusion of boron nitride with sodium carbonate in a muffle furnace is followed by a potentiometric titration of the boric acid. A special quartz vessel is described for the determination of nitrogen. The boron nitride is fused with sodium hydroxide and the resulting ammonia is swept into a receiver and titrated with standard hydrochloric acid. Boron and nitrogen values with their standard deviation are given for a typical pure boron nitride.     

Determination of heroin by means of the pitch of induced cholesteric mesophases

A method is described for the determination of chromatographic fractions of heroin and strychnine in the mug and sub-mug range by measurement of the pitch and handedness of their induced cholesteric mesophases in MBBA and Phase IV, respectively.     

Amine-induced growth of an In2O3 shell on colloidal InP nanocrystals

A simple and rapid method for the growth of an In2O3 shell on colloidal InP nanocrystals is described, increasing their fluorescence efficiency by one order of magnitude.     

Deoxygenation of Pyridones Via Their Tetrazolyl Ethers

A mild process for the conversion of pyridones to the corresponding pyridines by palladium catalyzed ammonium formate hydrogenolysis of their (1-phenyltetrazol-2-yl) ethers is described.     

Analysis of natural corticosteroids in adrenal extracts and in biological fluids by high-performance liquid chromatography

A liquid chromatographic procedure is described for the analysis of the principal natural corticosteroids in extracts of adrenal glands. Microparticulate silicic acid columns and gradients of methanol in chloroform are used: conditions are described for the quantitative analysis of the single principal steroidal components of adrenal extracts for pharmaceutical use and of adrenal extracts of rats. In the last case, the use of a 5-micron silica column with the appropriate gradient allows the determination of corticosterone and of 18-hydroxydeoxycorticosterone, which were identified by means of mass spectrometry on their eluates. A single analysis can be performed on the extract of 15 mg of rat adrenal tissue. For the last type of analysis, isocratic conditions on a 10-micron LiChrosorb Diol column are also described. The application of the gradient elution procedure to the analysis of steroidal compounds in human plasma is also described.     

Remote measurements of ozone concentration and aerosols in the Arctic stratosphere

Summary A LIDAR instrument for measurements of the ozone concentration and of aerosols in the middle atmosphere is briefly described. Data sets for ozone and aerosols, obtained at Spitsbergen during winter and early spring in 1989 and 1990, are presented. The Arctic ozone layer was found to be strongly influenced by atmospheric dynamics; a dramatic ozone depletion was not observed. Polar stratospheric clouds were detected in each winter, their dependence on the ambient atmospheric temperature is described.     

The use of formic acid in carrier gas. Rapid method for identification and determination of phytanic acid by gas chromatography-mass spectrometry-chemical ionization

A rapid gas chromatographic method to determine phytanic acid in plasma from Refsum's disease is described. After a brief alkaline hydrolysis of lipids, the biological sample is directly injected into a glass pre-column; an acid carrier gas (formic acid in nitrogen) is used to displace the long-chain fatty acids from their sodium salts and from their binding to proteins. Formic acid introduced through the column may also be used as a reagent gas for chemical ionization in combined gas chromatography--mass spectrometry; fatty acids (C14 to C18:2 and phytanic acid) are easily identified by their M + 1 (base peak) and M - 17 peaks. The described procedure is also suitable for studying normal fatty acids from plasma lipids.     

Gas Chromatographic Analysis of Aminothiol Radioprotective Compounds

Abstract

A gas chromatographic method is described for aminothiols and disulfides. This method is based upon the formation of the trimethysilyl derivatives and their separation by gas chromatography. The kinetics of the derivative formation were investigated. A synthetic method for C4 to C6 aminothiols is given.     

Half-numerical evaluation of pseudopotential integrals

A half-numeric algorithm for the evaluation of effective core potential integrals over Cartesian Gaussian functions is described. Local and semilocal integrals are separated into two-dimensional angular and one-dimensional radial integrals. The angular integrals are evaluated analytically using a general approach that has no limitation for the l-quantum number. The radial integrals are calculated by an adaptive one-dimensional numerical quadrature. For the semilocal radial part a pretabulation scheme is used. This pretabulation simplifies the handling of radial integrals, makes their calculation much faster, and allows their easy reuse for different integrals within a given shell combination. The implementation of this new algorithm is described and its performance is analyzed.     

Stereoselective synthesis and structural correction of the naturally occurring lactone stagonolide G

A convergent synthesis of the structure proposed for the naturally occurring lactone stagonolide G is described. All three stereocenters were created with the aid of asymmetric Brown allylations. The lactone ring was built by means of a ring-closing metathesis (RCM). The synthetic and the natural compound differed in their spectral properties. A new structure is now proposed for stagonolide G and demonstrated by means of a chemical transformation.     

Three-dimensional synchronous fluorescence spectrometry for the analysis of three-component alkaloid mixtures

A study of a simple and sensitive method for the determination of berberine, luguine and sanguinarine in mixtures by normal and synchronous derivative spectrofluorimetry is described. The influence of solvents and other experimental variables is discussed. A three-dimensional plot of both emission-excitation and synchronous spectra obtained by a new software program provides additional information for optimizing instrumental parameters. Linear, normal and derivative calibration graphs are established in the ng/ml range. A statistical analysis of the results and their application to synthetic and natural samples is given.     

离子色谱不对称色谱峰的处理

介绍了通过微分处理分辨离子色谱中不对称峰的方法。实验将Ｆ＾－、Ｃｌ＾－、Ａｃ＾－、ＮＯ２＾－、ＮＯ３＾－、ＰｈＣＯＯ＾－、ＳＣＮ＾－、柠檬酸根、水杨酸根、山梨酸根和葡萄糖酸根等常见离子按一定比例配合混合液,对出现的不对称峰进行微分处理,得到的导数谱图可进行峰高定量,收到了较好的效果。     

Preparation of methoxysilyl humic acid derivatives with the use of 3-isocyanatopropyltrimethoxysilane

A new method for modifying (methoxysilylating) coal humic acids by reacting them with 3-isocyanatopropyltrimethoxysilane is described. The modification products structurally characterized by FTIR and NMR spectroscopy. The sorption ability of methoxysilated humic acids on silica gel is studied in the batch mode to illustrate their affinity to silicon minerals.