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  • 1
    Electronic Resource
    Electronic Resource
    Column wall modifications using polyethylene oxide for capillary electrophoresis of ribonucleotides (1999)
    Springer
    Chromatographia 49 (1999), S. 299-305 
    Details
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Column technology ; Deactivation ; Polyethyleneoxides ; Ribonucleotides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this study, a variety of fused silica capillaries with different combinations and sequences of treatments with HMDS and polyethylene oxide were prepared in order to develop an optimized column modification method for analysis of ribonucleotides. The 12 most common ribonucleotides (UTP, CTP, ATP, GTP, UDP, CDP, ADP, GDP, UMP, CMP, AMP, and GMP) in human cells were used as test solutes. Column performance measurements, including electroosmotic flow (EOF), solute migration speed and retention, column efficiency, peak shape, and resolution were investigated. By analyzing solute migration speed and retention of various hydrophilic/hydrophobic solutes, the column wall effects (EOF and adsorption) can be distinguished. This analysis method can give guidance in optimizing polymer coating properties (hydrophilicity/hydrophobicity) for CE columns. By studying the performance of these columns after various surface treatments, we were able to improve the separation of ribonucleotides from real samples to within 16 minutes with high efficiency and stability (over 300 analyses) using columns first deactivated with hexamethyldisilazane, and then coated with polyethylene oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467560
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  • 2
    Electronic Resource
    Electronic Resource
    Polymethylhydrosiloxane surface deactivation of silica particles for packed capillary column supercritical fluid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 665-670 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Surface modification ; Deactivation ; Silica particles ; Stationary phases ; Packing materials ; Packed capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Spherical porous silica particles (10 μm diameter, 300 Å and 80 Å pores), spherical nonporous silica particles (10 μm diameter), and irregular porous silica particles (≈10 μm diameter, 80 Å pores) were deactivated with polymethylhydrosiloxane (PS). The surface activities of the deactivated silica particles were investigated using various polar compounds under supercritical fluid chromatography (SFC) conditions (neat CO2), and compared with a commercial C18-bonded phase. The small pore (80 Å) silica particles could be more completely deactivated than larger pore (300 Å) and nonporous silica particles. The success of the PS deactivation method is ascribed to the excellent match between the reactive groups on the polymer backbone and the silica surface, and the formation of a highly crosslinked polymeric layer over the surface. Physical processes, such as adsorption and desorption of the deactivation reagent on the surface and diffusion from the surface, were found to have important effects on the deactivation. Using capillary columns packed with PS deactivated silica particles, typical polar organic compounds, including hydroxyl-containing compounds, carbonyl-containing compounds, free amines, and free carboxylic acids, were separated by SFC and compared with results from a commercial C18-bonded phase. While the results clearly show that the PS deactivated particles were more inert than the C18-bonded phase, better deactivation methods are still needed for separation of free acids and alkylamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267802
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  • 3
    Electronic Resource
    Electronic Resource
    Parallel conjugate gradient performance for least-squares finite elements and transport problems (1998)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 1421-1440 
    Details
    ISSN: 0271-2091
    Keywords: parallel ; conjugate gradient ; least squares ; FEM ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this study we consider parallel conjugate gradient solution of sparse systems arising from the least-squares mixed finite element method. Of particular interest are transport problems involving convection. The least-squares approach leads to a symmetric positive system and the conjugate gradient scheme is directly applicable. The scheme is applied to both the convection-diffusion equation and to the stationary Navier-Stokes equations. Here we demonstrate parallel solution and performance studies for a representative MIMD parallel computer with hypercube architecture. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Least-squares finite elements for fluid flow and transport (1998)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 27 (1998), S. 97-107 
    Details
    ISSN: 0271-2091
    Keywords: least-squares ; finite elements ; flow ; transport ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The least-squares mixed finite element method is concisely described and supporting error estimates and computational results for linear elliptic (steady diffusion) problems are briefly summarized. The extension to the stationary Navier-Stokes problems for Newtonian, generalized Newtonian and viscoelastic fluids is then considered. Results of numerical studies are presented for the driven cavity problem and for a stick-slip problem. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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