Projectivep-algebras

Presented by R. Freese.     

Effects of nebulizing and drying gas flow on capillary electrophoresis/mass spectrometry

This study was focused on examining the influence of gas flow parameters on capillary electrophoresis/mass spectrometry (CE /MS) performance using sheath-liquid CE /MS interfaces. The effects of nebulizing and drying gas velocity and drying gas temperature on CE separation and MS detection sensitivity were systematically determined. Nebulizing gas velocity was observed to be a critical parameter in the optimization of CE /MS method, since it affected both MS detection sensitivity, and also CE separation efficiency for one interface design tested. Better detection sensitivity was obtained when the nebulizing gas velocity was increased. However, high velocity of the nebulizing gas flow can cause a hydrodynamic bulk flow inside the CE capillary, thus clearly increasing the apparent mobility and decreasing the resolution obtained for the compounds studied. Increasing the drying gas velocity or temperature did not affect the apparent mobility or the separation efficiency and the temperature could be increased to achieve the optimal detection sensitivity in the CE /MS analysis. For comparison, the effects of nebulizing gas flow were studied using a different design of the coaxial sheath-liquid CE /MS interface, and in this case better detection sensitivity but no effect on CE separation efficiency was observed with increased nebulizing gas velocity. These different effects of nebulizing gas flow on the CE bulk flow were concluded to result from pressure differences at the tip of the CE capillaries for the different CE /MS interface arrangements. It is therefore recommended that the cross-sectional dimensions of the fused-silica and steel capillaries, and the gas streamlines, should be optimized when CE /MS interfaces are built. Moreover, the effect of gas flow on CE separation should be studied when optimizing the CE /MS operation parameters.     

A concept for bifocal contact‐ or intraocular lenses: liquid single crystal hydrogels (“LSCH”)

The synthesis of liquid single crystal hydrogels (“LSCH”) in suitable molds offers an innovative concept to realize bifocal contact‐ or intraocular‐lenses. LSCH combine the properties required for applications as bifocal ophthalmic lenses: the soft and water‐containing hydrogel enables oxygen permeation and exhibits high birefringence due to the liquid crystalline phase structure built up by rigid rod‐like amphiphiles. Via a photo‐initiated crosslinking reaction of aqueous solutions of monomeric lyotropic liquid crystalline amphiphiles in the macroscopically ordered liquid crystalline state, we obtain optically uniaxially ordered and transparent LSCH. The orientation process and the phase structure of the anisotropic hydrogel is analyzed by deuterium NMR‐spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd.     

Orientation of a chiral smectic C elastomer by mechanical fields

It is well known that, with respect to the director, nematic elastomers can be macroscopically aligned by uniaxial mechanical fields. Extending this method to a chiral smectic C elastomer, depending on the experimental set-up either smectic layer orientation or director orientation parallel to the stress axis occurs. In order to align the director and the smectic layers a biaxial mechanical field (e.g. shear field) consistent with the phase symmetry has to be used to achieve a macroscopically uniform orientation of the untwisted smectic C^* structure.     

Determination of wear metals in lubrication oils: a comparison study of ICP-OES and FAAS.

Certain wear metals (Fe, Cr, Ni, Cu and Zn) of various lubrication oils were determined by means of ICP-OES and FAAS. The kerosene dilution method, which is used widely together with ICP-OES, was applied with both methods here. Calibration standards were made from a commercial organo-metallic standard. Our aim was to clarify the possibility of using the quick kerosene dilution method together with FAAS for a rapid check for certain indicator metals. Metal determinations with FAAS were accurate enough for quantitative work in machine condition diagnostics and waste oil characterization, when compared with those with ICP-OES.     

Comparison of rheological properties of cross-linked and thermal-mechanically degraded HDPE

Rheological properties of a high-density polyethylene (HDPE) subjected to thermal-mechanical degradation were compared with those of the HDPE degraded by the addition of small quantities of peroxides as free radical initiator. The high molecular weight fraction of HDPE changes quantitatively during processing, which has a remarkable effect on the rheological properties of the material, when the MWD narrows and the HMW tail decreases. The molecular weight distribution, especially the highest molecular weight fraction, is concluded to be more important than the long chain for HDPE rheology. © 1995 John Wiley & Sons, Inc.