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  • 1990-1994  (6)
  • 1950-1954
  • 1991  (6)
  • Polymer and Materials Science  (3)
  • Engineering  (2)
  • electroporation
  • 1
    ISSN: 1573-5028
    Keywords: chalcone synthase promoter ; electroporation ; elicitor ; transient gene expression ; alfalfa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A chimeric gene consisting of a bean (Phaseolus vulgaris L.) chalcone synthase (CHS) promoter fused to a bacterial chloramphenicol acetyltransferase (CAT) reporter gene was strongly expressed, and further induced by fungal elicitor, when electroporated into alfalfa (Medicago sativa L.) suspension cell protoplasts. Functional analysis of 5′ deletions of the CHS promoter-CAT construct in these protoplasts indicated that the region between −326 and −130 contained both activator and silencer elements. Co-electroporation experiments confirmed that these cis-acting elements were binding sites for functionally active trans factors. In vitro DNase I footprinting revealed four potential binding sites for alfalfa suspension cell nuclear proteins between positions −326 and −130 of the CHS promoter. These sites mapped to regions shown to contain functional cis-acting elements on the basis of the deletion analysis. Three of these sites mapped to previously identified binding sites for bean nuclear proteins. Competition gel retardation analysis using oligonucleotide probes containing binding site sequences revealed sequence-specific binding of alfalfa nuclear proteins to an AT-rich element and a putative GT-1 factor consensus binding sequence. Our results define cis elements and their cognate trans factors functionally active in determining the quantitative expression of a defense response gene in a heterologous transient expression system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 581-588 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyurethanes based on methylene bis(p-phenyl isocyanate), bis(hydroxymethyl) propanoic acid, and poly (tetramethylene oxide) were synthesized, and their morphology and physical properties investigated. The acid polyurethanes exhibited very poor phase separation and mechanical properties, but upon neutralization with alkali metals phase separation improved dramatically and the materials resembled tough elastomers. The choice of cation played a much less important role than hard segment content in determining morphology and properties. Small-angle x-ray scattering patterns of these ionic polyrethanes exhibit two peaks, one characteristic of scattering between the hard and soft domains and the other reflecting scattering from aggregates of ionic groups residing within the hard domains. While ionic aggregation is the primary driving force for phase separation in these materials, their morphology more closely resembles that for nonionic polyurethanes than that for conventional ionomers, because the ionic groups exist in blocks composed primarily of rigid diisocyanate residues.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The interaction between several polymeric materials, typical of those that have application as parenteral product containers, and 16 marker solutes was evaluated. Polymers used included polypropylene, polyvinyl chloride, ethylenevinyl acetate, an olefin rubber, a polyester ether block copolymer, and various composites of these materials. In addition, the partitioning of solutes between two common PVC plasticizers (dioctyl phthalate and butyryl hexyl citrate) and water was also examined. Correlation between equilibrium interaction constants (Eb) (which describe the equilibrium distribution of a solute between contacting polymer and solution phases) and solute octanol-water (Po-w) or hexane-water (Ph-w) partition coefficients were in general poor for all materials studied. However, a bivariate linear interaction model relating Eb to both partition coefficients: \documentclass{article}\pagestyle{empty}\begin{document}$$ \log E_b = a\left( {\log P_{{\rm o} - {\rm w}} } \right) + b\left( {\log P_{{\rm h} - {\rm w}} } \right) + c$$\end{document} effectively mimicked the interaction behavior of all materials evaluated. The utilization of the developed models to facilitate container compatability assessments is discussed. In addition, the use of a critical ratio of binding constants for a pair of solutes is introduced as a means of qualitatively assessing the effectiveness of a particular solvent as a polymer model.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical behavior of the copper(II) complex of bleomycin, a glycopeptide antibiotic with antitumor activity, was investigated in several buffer systems using cyclic voltammetry, polarography, coulometry, and spectroelectrochemistry. The copper bleomycin complex exhibited irreversible one-electron reduction on glassy carbon and mercury electrodes and was electroinactive on platinum, gold, and silver. After the initial reduction process on mercury, the appearance of the Cu(0)/(II) redox couple indicated dissociation of the complex and subsequent reduction of the Cu(I) to the metal. In the presence of excess bleomycin, the Cu(II) reoxidized from the mercury electrode is rapidly complexed and no copper reduction process is observed. On glassy carbon, however, the Cu(I) bleomycin complex is stable and does not undergo further reduction, as demonstrated by spectroelectrochemistry at a reticulated vitreous carbon optically transparent electrode. Consequently, as with many metallo-organic redox processes, there appear to be several possible electrochemical pathways depending on the pH, the electrode materials, and the experimental time domain.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 12 (1991), S. 911-928 
    ISSN: 0271-2091
    Keywords: Direct stress solution ; Vertical velocity profiles ; Three-dimensional circulation model ; Spectral methods ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A simple technique is presented that allows a numerical solution to be sought for the vertical variation of shear stress as a substitute for the vertical variation of velocity in a three-dimensional hydrodynamic model. In its most general form the direct stress solution (DSS) method depends only upon the validity of an eddy viscosity relation between the shear stress and the vertical gradient of velocity. The rationale for preferring a numerical solution for shear stress to one for velocity is that shear stress tends to vary more slowly over the vertical than velocity, particularly near boundaries. Consequently, a numerical solution can be obtained much more efficiently for shear stress than for velocity. When needed, the velocity profile can be recovered from the stress profile by solving a one-dimensional integral equation over the vertical. For most practical problems this equation can be solved in closed form.Comparisons are presented between the DSS technique, the standard velocity solution technique and analytical solutions for wind-driven circulation in an unstratified, closed, rectangular channel governed by the linear equations of motion. In no case was the computational effort required by the velocity solution competitive with the DSS when a physically realistic boundary layer was included.The DSS technique should be particularly beneficial in numerical models of relatively shallow water bodies in which the bottom and surface boundary layers occupy a significant portion of the water column.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 12 (1991), S. 835-857 
    ISSN: 0271-2091
    Keywords: Boundary element ; Free surface ; Hydrodynamic ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Free surface phenomena are described by equations that exhibit two types of non-linearities. The first is inherent to the equations themselves and the second is caused by the application of boundary conditions at a free surface at an unknown location. Numerical calculations usually do not specifically recognize the second non-linearity, nor treat it in a fashion consistent with the more obvious non-linearities in the boundary conditions. A consistent formulation is introduced in the present paper. The field equation is integrated and the free surface boundary conditions are applied on the unknown geometry by means of appropriate series expansions. The consistent formulation introduces improvements in accuracy and computing speed. The method is demonstrated on several hydrodynamic free surface problems and an error analysis is included.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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