Use of hydrolyzed chlorosilanes for the preparation of high resolution glass capillary columns

Summary A new procedure for the preparation of high resolution open tubular glass capillary columns is described. This procedure involves the preparation of polysiloxane polymers obtained by alkaline hydrolysis of alkyl chlorosilane. The mixture of polysiloxane polymers is then coated on the wall of previously HCl treated glass capillary columns using a dynamic method. A base-catalysed reaction using gaseous ammonia, applied to the coated polymers leads to a stable chemically bonded stationary phase, with non-polar characteristics. This type of column is easier to prepare than conventional ones and exhibits excellent chromatographic properties, both with regard to their resolution, stability and reproducibility. The flexibility of this method permits the use of other types of commercially available chlorosilanes (i.e. methylphenyl chlorosilane) to prepare polar polysiloxane polymers suitable for analysis of complex biochemical mixtures, such as steroid metabolites.     

Application of the Carman–Kozeny Correlation to a High‐Porosity and Anisotropic Consolidated Medium: The Compressed Expanded Natural Graphite

The Carman–Kozeny correlation is applied to a medium which is consolidated, highly porous and anisotropic: the expanded then compressed natural graphite. The effective textural properties (i.e. the mean pore diameter, porosity and tortuosity) have been measured by a mercury porosimeter and a heterogeneous diffusion cell. The texture and the permeability (according to the Darcy's law) measured for the two main directions of these orthotropic porous media change over a very wide range depending on their apparent mass densities. Experimental data show that only a part of the total porosity participates in the gas flow in steady state conditions.     

Study of the 208Pb(n, γ0)209Pb reaction between 0.8 and 7.7 MeV

The reaction ²⁰⁸Pb(n, γ₀)²⁰⁹Pb was studied from 0.8 to 7.7 MeV to investigate relative contributions of the compound-nucleus and direct and semidirect processes in this energy range. Compound-nucleus reactions dominate below about 5 MeV and semidirect processes above 6 MeV. The direct-semidirect (DSD) model with a complex particle-vibration coupling describes the experimental data in the giant resonance region. A relatively large imaginary term is necessary to obtain a good fit to the data indicating either that the reactions proceed to a large extent in more complicated ways than the simple two-step semidirect reaction or that the model has a serious defect in its present formulation. A second objective was to search for a possible excitation of the isoscalar E2 and the M1 giant resonances by measuring asymmetries around 90° in the angular distribution of the γ-rays. The results indicate no (or very weak) asymmetry effects.     

Experimental and numerical analysis of automotive gearbox rattle noise

The aim of this work is to characterize the rattle noise of automotive gearboxes, resulting from impacts between toothed wheels of unselected gear ratios. These stereo-mechanical impacts are modeled by a coefficient of restitution which describes damping during the squeezing of the lubricant film for approaching surfaces, and the elastic deformation of impacting bodies. The dynamic response of the loose gear first depends on the design parameters and the engine operating conditions. The unknown parameters are the drag torque and the coefficient of restitution. They are identified experimentally through implementation of two optical encoders in an actual automotive gearbox and the operation of a specific test bench which replicates the automotive power train. Models of the different drag torque sources are validated from analysis of the free damped response of the driveline. The coefficient of restitution and its probability density function are measured from experiments under stationary operating conditions. A nonlinear model is built. The dynamic response of the loose gear depends on the dimensionless backlash, the coefficient of restitution and a dimensionless parameter proposed to describe the rattle excitation level. Experiments under controlled excitation are performed to validate the assumptions, to confirm the ability of the parameter proposed to describe the rattle noise threshold, and to characterize the dynamic response. The nonlinear model predictions are fitted with the drag torque and coefficient of restitution previously identified. They are compared with measurements to demonstrate the ability of the model to predict gear rattle for any loose gear, any gearbox and any operating condition.     

Glass capillary gas chromatography with electron-capture detection. Separation of prostaglandins

Glass capillary gas chromatography of the prostaglandins was performed on a system including an all-glass, solventless injector; thermostable methylphenyl-polysiloxane glass capillary columns; and a conventional electron-capture detector fitted with a make-up gas tee. The principal stable metabolites of prostaglandin endoperoxide were separated as perfluorinated derivatives in 35 min. Detection limits equal or exceed those obtained for packed column separations and electron capture detection. Prostaglandin endoperoxide metabolic profiles from mammalian cell cultures were obtained using this system. These profiling studies are not possible with other chromatographic methods because of inferior resolution and sensitivity.     

Glass capillary column chromatography of mixed derivatives of primary prostaglandins, 6-keto prostaglandin F1α and thromboxane B2

This work describes the use of glass capillary columns (GCC) in the rapid concurrent analysis of primary prostaglandins (PGs) (e. g. PGE₂, PGE₂, PGF_2α) and other functionally significant metabolites of arachidonic acid (AA) such as TXB₂ and 6-keto PGF_1α. The use of a new multistep mixed derivatization approach that generates the methyl esters of n-butylboronate, pentafluorobenzyloxime, trimethylsilyl ether derivatives of these compounds remarkably simplifies the GC profiling of the three main pathways of AA metabolism (PGs, thromboxane, and prostacyclin). Furthermore, isomeric species giving very similar or identical mass spectral patterns can be easily identified by their relative retention times on high efficiency capillary columns.