Determination of percent composition of a mixture analyzed by gas chromatography. Comparison of a helium pulsed-discharge photoionization detector with a flame ionization detector

We present the results of a study of percent composition for a mixture which has been separated by gas chromatography and analyzed using helium pulsed-discharge photoionization detection (He-PDPID) and flame ionization detection (FID). FID has long been the means by which the percent composition of a hydrocarbon mixture has been determined since it has been previously established as a "carbon counting device". However, in this study we present results which show that He-PDPID is more accurate in determining the percent composition of a hydrocarbon mixture and, because it is a universal detection method and can detect compounds that FID cannot, it is also more effective for determining the percent composition of mixtures containing organic compounds with a variety of other functional groups.     

Dispersion forces in methane

The dispersion energy of methane has been calculated by a second-order perturbation treatment. The free-electron model has been used to describe the isolated molecule, which has been assimilated to a spherical, two-dimensional box. Agreement with experiment is gratifying.     

Group contribution analysis applied to the Havriliak–Negami model for polyurethanes

Group contribution analysis (GCA) has been applied to many of the physical properties of polymers in the past. In this paper, GCA has been applied for the first time to the frequency dependent complex modulus of polymeric materials, which may be described in terms of the Havrialiak–Negami (H–N) equation. This approach has been tested on a set of polyurethanes for which the H–N parameters have been uniquely determined. It has been shown that the dynamic mechanical behaviour of polymers may be described in terms of group additive relationships, at least for the 14 polyurethanes and nine structural groups which were studied here.     

The application of the brönsted concept to the calculation of pH in systems involving two acid-base couples : Systems involving two independent acid-base couples

The BRÖNSTED concept has been applied to the derivation of a single equation which is valid for the calculation of pH in any system containing two independent acid-base couples in an amphiprotic solvent. Bxamples of the application of this equation to a few representative systems have been given. The advantages of the method of approach which, has been outlined have been emphasized.     

On the molecular structure of uranium dicarbide: T-shape versus linear isomers

A theoretical study of the molecular structure of uranium dicarbide has been carried out employing DFT, coupled cluster, and multiconfigurational methods. A triangular species, corresponding to a (5)A(2) electronic state, has been found to be the most stable UC(2) species. A triplet linear CUC species, which has been observed in recent infrared spectroscopy experiments, lies much higher in energy. A topological analysis of the electronic density has also been carried out. The triangular species is shown to be in fact a T-shape structure with a U-C interaction which can be considered to be a closed-shell interaction.     

A study of the effect of network angle of fabrics on kinetics of impregnation upon molding of articles made from carbon plastics

The permittivity coefficient, volume, and porosity of an elementary cell of fabric filler have been calculated. Two types of fabric structures have been considered using the example of carbon fabric: standard, in which filament yarn is cylindrical, and spread, it which it has a rectangular shape. A reflector of a mirror space antenna has been considered characterized by the presence of doubly curved surfaces is used as the object of study. Modeling of the kinetics of impregnation of reflector for two types of fabric structures has been carried out using the RAM–RTM program. In the work, the effect of the network angle on the duration of impregnation process has also been investigated. Based on the results of calculation, reflector samples have been made and their quality has been evaluated. Theoretical and experimental results have been compared.     

Modification of Chemically Amplified Resists by Radical Copolymerization

Modification of a phenolic resist has been carried out by copolymerization with methacrylic monomers. Influence of irradiation source and its intensity has been studied by analyzing sensitive curves of a various resist composition. Inversion of imaging type at varying post exposure bake temperature has been investigated for resists based on copolymers containing methacrylic acid units, which has been related with crosslinking of macromolecules.     

Perturbation of the chemotactic tumbling of bacteria.

The bacterial sensing system has been studied on three levels. First, a quantitative method has been devised for measuring the "action spectrum" of the bacterium in response to a sudden addition of attractant. Second, a technique has been developed for the rapid isolation of mutants defective in the transmission part of the sensing system. Third, a study of the effects of light on the transmission system reveals two components, one which generates, tumbling and another which inhibits it.     

Gas mixture flow in nanoporous media in the presence of surface forces. The dusty-gas model

The dusty-gas model has been generalized to the case of gas mixture flow in nanoporous media under the conditions of the action of surface forces. A basic set of transport equations has been derived proceeding from kinetic equations for a gas mixture and dust particles. To take into account the surface forces, the interaction between a gas and dust particles has been represented as a sum of a long-range potential, which reflects the surface forces, and a short-range potential, which describes gas molecule scattering on the surface of pore walls. The contribution of the long-range component has been taken into account in the self-consistent approximation, while the short-range component has been considered in the standard manner. The surface forces have been shown to have a substantial effect on the transfer of mixed gases through porous bodies; in particular, it becomes possible to separate mixture components due to different potentials of the interaction of their molecules with pore surface.     

New quinone from a marine sponge of the order dictyoceratida

Two pigments of quinoid nature, one of which has been identified as ilimaquinone, have been isolated from a hexane extract of a marine spongeHyatella sp., family Spongiidae, order Dictyoceratida. The second was a new benzoquinone of the drimane series with the composition C₂₂H₃₂O₅, which has been called hyatoquinone. Its structure has been established on the basis of spectral characteristics and chemical transformations.     

On temperature- and space-dimension dependent matter agglomerations in a mature growing stage

Model matter agglomerations, with temperature as leading control parameter, have been considered, and some of their characteristics have been studied. The primary interest has been focused on the grain volume fluctuations, the magnitude of which readily differentiates between two commonly encountered types of matter agglomeration/aggregation processes, observed roughly for high- and low-density matter organizations. The two distinguished types of matter arrangements have been described through the (entropic) potential driving the system. The impact of the potential type on the character of matter agglomeration has been studied, preferentially for (low-density) matter aggregation for which a logarithmic measure of its speed has been proposed. A common matter diffusion as well as mechanical relaxation picture, emerging during the mature growing stage, has been drawn using a phenomenological line of argumentation. Applications, mostly towards obtaining soft agglomerates or so-called jammed materials, have been mentioned.     

The application of thiosalts in analysis : A new scheme of qualitative analysis - part a

1. A new scheme of qualitative analysis for mixtures containing the common as well as the so-called “rare” elements has been discussed. 2. The new scheme is based upon the immediate formation of thiosalts by metals of the arsenic group (and vanadium) on adding concentrated ammonium sulphide solution and the subsequent decomposition of the thiosalts with excess of hydrochloric acid. 3. This scheme has the following advantages over the classical scheme now in use: a. The slow precipitation of the copper and arsenic groups by hydrogen sulphide in hydrochloric acid solution has been replaced by a more simple and rapid method of precipitating the sulphides completely. A considerable saving of time taken in analysis is thus effected. b. The use of the hydrogen sulphide gas which is extremely inconvenient especially in large classes of students, has been eliminated and its place has been taken by concentrated ammonium sulphide—a reagent which can be easily prepared and used as a shelf reagent. c. The use of yellow ammonium sulphide which does not give a satisfactory separation of the copper group from the arsenic group has been eliminated. d. As the main features of the new scheme are similar to those of the classical scheme the student who has been trained in the old technique can take to the new scheme without much difficulty.     

Preparation and polymerization of a diisocyanate from the Diels-Alder adduct of levopimaric acid and acrylic acid

Starting from tetrahydroabietic acid the model compounds tetrahydroabietoyl chloride, 2-aminoethyltetrahydroabietate hydrochloride, and 2-isocyanatoethyltetrahydroabietate have been prepared. Carbamate and urea derivatives of the isocyanate have been prepared. A Diels-Alder adduct of levopimaric acid and acrylic acid has been prepared and converted to its diacid chloride. The β-aminoethyl ester hydrochloride has been synthesized and converted to a diisocyanate which has been polymerized with poly(tetramethylene glycol) and also with p-phenylenediamine. Dimerex resin, a technical polymerized rosin, has been similarly converted to a diisocyanate. This isocyanate has not proven to be useful as a polymer-forming intermediate.     

High precision titrimetry: A System of weight titrimetric analysis using arbitrary standards

A technique of arbitrary standard weight titrimetric analysis has been proposed for realising the ultimate degree of mechanical precision of which titrimetric processes are capable, and has been applied to reactions and methods of end-point location which are particularly favourable. A form of needle-valve weight burette is also described. It has been found that, even in the most favourable cases and working under the conditions of atomic weight determination, there is a limit to the precision and therefore accuracy of the analytical results, which is set by physico-chemical considerations, and which is at least one order less than the maximum attainable mechanical precision of measurement.     

Octaphenylbiphenylene and dodecaphenyltriptycene

Octaphenylbiphenylene, the expected dimer of tetraphenylbenzyne, has been prepared in low yield by diazotization of 3,4,5,6-tetraphenylanthranilic acid, and its X-ray structure has been determined. The X-ray structure of a second, abnormal dimer of tetraphenylbenzyne, 1,2,3,8,9,10-hexaphenyldibenzo[fg,op]naphthacene has also been determined; this is a saddle-shaped polycyclic aromatic hydrocarbon. 1,2,3,4,5,6,7,8,13,14,15,16-Dodecaphenyltriptycene, perhaps the most crowded triptycene derivative yet prepared, has been made by the reaction of tetraphenylbenzyne with 1,2,3,4,5,6,7,8-octaphenylanthracene, which in turn was synthesized in two steps from commercial starting materials. The X-ray structure of the dodecaphenyltriptycene nonabenzene solvate is a remarkable channel containing structure in which more than 50% of the unit cell volume is occupied by the benzene molecules.     

Porous Gels Made by Phase Separation: Recent Progress and Future Directions

Recent progress in the sol-gel science concerning the porous gels made by phase separation has been reviewed. Based on the principle and technique explored for monoliths, the material shape has been extended to a macroporous thick film and a macroporous gel in a confined space such as capillary, both of which are expected to find useful applications in the chromatography. The modifiable size range of the additional porosity within the micrometer-sized gel skeleton has been broadened from micropores by zeolite, mesopores by surfactant templates to macropores by intensive hydrothermal treatments. A detailed investigation of 3D interfacial structure in real space has been performed using the laser scanning confocal microscope, which enabled quantitative comparison of the structure with those of other phase-separating systems.     

Thermodynamics and mechanism of reduction of silicon with carbon in a crucible reaction

A thermodynamic analysis of a crucible reaction, which takes place in crucible induction furnaces, has been represented. A new diagram of a crucible reaction, with due account for partial pressures and activities of the participating components, has been suggested. For the first time ever, the electrochemical mechanism of a crucible reaction has been studied; the research has confirmed the correctness of the suggested diagram.     

A fluorimetric and circular dichroism study of hemoglobin--effect of pH and anionic amphiphiles

In this work, bovine hemoglobin (Hb) has been studied mainly by the fluorescence method. pH has been found to exert a profound effect on Hb structure. This has been confirmed by fluorescence and circular dichroism (CD) studies. The pH-induced change in quaternary structure of Hb indirectly affects its secondary structure. This in turn affects ligand binding to Hb at various pH. The binding of two amphiphiles, a bile salt and a surfactant, have been investigated. The pH-induced structural modification of Hb has been confirmed by studies with the well-known denaturant urea and the polarity probe ANS, which has been used as an extrinsic fluorophore.     

Simultaneous optimization of the analysis time and the concentration detectability in open-tubular liquid chromatography

Scott's OT-LC minimal analysis time problem has been solved analytically and has been extended to thick-film and/or large diameter columns. The optimisation analysis has also been applied to a number of relative performance indexes (Cmax/t(anal), Cmax x d/t(anal) and Cmax x u x d2/t(anal) which provide a quantitative insight on the extent to which OT-LC allows to combine short analysis times with a large concentration detectability.     

Indole derivatives

The Fischer cyclization of arylhydrazones of 1-butyl-, 1-benzyl-, and 1-cyclohexyl-3-pyrrolidinones has been studied, as a result of which a synthesis of 1, 2,3,4-tetrahydropyrrolo[3,4-b]indoles has been developed. The structure of the compounds obtained has been confirmed by their UV and NMR spectra and by a number of chemical properties.