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  • 1
    Electronic Resource
    Electronic Resource
    Elastin dehydration through the liquid and the vapor phase: A comparison of osmotic stress models (1996)
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 627-639 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The swelling and viscoelastic behaviors of samples of purified arterial elastin were investigated to develop a model for studying the viscoelastic behavior of elastin. Two osmotic stress models were used: the vapor phase model (VPM), in which the stress on the elastin sample was applied through the vapor phase by equilibrating the sample over a saline solution, and the liquid phase model (LPM), in which the stress was applied through the liquid phase by equilibrating the sample in aqueous solutions of large molecular weight polymers. The elastin in the VPM showed a highly varied viscoelastic response, and was slightly stiffer and had a slightly higher damping coefficient than the elastin in the LPM at equivalent nominal relative humidities. We believe the difference in behavior of the elastin in the two models was due to geometric distortions of the elastin that occur during dehydration in the VPM. In the LPM, the spaces between the elastin fibrils are filled with water, and in the VPM these spaces collapse when the water is removed. Removal of only the interfibrillar water deswelled the tissue and increased its stiffness and damping coefficient.Viscoelastic spectra obtained at different levels of osmotic stress in the LPM were reducible to one master curve, indicating that the dominant effect of dehydration is a nonspecific reduction of molecular mobility. We conclude that the LPM is a better model than the VPM for studying the effects of dehydration on the mechanical behavior of elastin. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Quartz dissolution kinetics from 100-200°C as a function of pH and ionic strength (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3442-3457 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Of importance to geothermal energy development, oil, gas and mineral recovery, and waste storage is the characterization of the dissolution rate of host reservoir rock as a function of temperature, pressure and liquid-phase composition. As a major constitutive mineral in natural geologic systems, quartz was selected for study. Dissolution experiments were carried out in a continuous-flow, titanium autoclave reactor system at 100-200°C in various chemical environments. Acidification to pH 1.1 using nitric acid showed very little effect on the quartz dissolution rate. The effect of hydroxide ion concentration and ionic strength were evaluated in NaOH, NaOH/NaCl and NaOH/Na2SO4 solutions. The fractional-order dependency of the quartz dissolution rate on hydroxide ion and sodium ion (or ionic strength) concentration was determined in NaOH/NaCl solutions. The results that extend the available range of kinetic data for quartz generally agree with previous work. The observed fractional-order kinetics were qualitatively described using classical adsorption isotherms. No significant variation in the apparent reaction order of the hydroxide ion with increasing temperature could be determined due to the scatter in the data. Quartz dissolution rates were slower by about 40% in NaOH/Na2SO4 solutions than in NaOH/NaCl solutions at sodium concentrations higher than 0.01 molal. The apparent activation energy from 100 to 200°C in NaOH/NaCl solutions up to 0.01 molal hydroxide ion and 0.1 molal sodium ion was estimated to be 72 (±6) kJ/mol.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690421214
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  • 3
    Electronic Resource
    Electronic Resource
    Flow regimes of the three-phase circulating fluidized bed (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 267-271 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas-solids circulating fluidized beds have been successfully used in catalytic cracking of heavy oil, coal combustion, and some metallurgical and physical processes (Grace, 1990). Gas-liquid-solids fluidized beds are operated mainly in conventional fluidization regimes without solids circulation or in the transport regime with low solids holdups (less than 5%) (Fan, 1989). A circulating/fast fluidization regime, however, has not been studied. A three-phase circulating fluidized bed has several potential applications in biochemical and chemical processes. Three-phase fluidized-bed bioreactors generally use light and small particles (Berk et al., 1984). Circulating operation can promote solids mixing and increase product throughput per unit bed cross section, while high shear stress can promote biofilm renewal (Pirozzi et al., 1990). In three-phase hydrotreating reactors, solids catalysts lose their activity due to the deposit of metal and coke on the surface. Circulating operation not only regenerates deactivated catalyst continuously using accompanying downcomers but also transfers heat to and from the reactor. This article discusses the flow regimes of the three-phase circulating fluidized bed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410209
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of dynamic interfacial properties on droplet breakup in plane hyperbolic flow (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1436-1447 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Droplet breakup in laminar flows is important in emulsification processes and polymer blending. The influence of surfactants on droplet deformation and breakup in a plane hyperbolic flow was studied experimentally in an opposed-stream device. As in the case of simple shear flow, the inhomogeneity of the surfactant distribution along the droplet interface has a pronounced effect. Our results are qualitatively consistent with other numerical studies for droplet breakup in an axisymmetric elongational flow. Also a striking similarity is noted with other experimental observations for the deformation and breakup of polymeric drops in a quasi-steady-plane hyperbolic flow. The critical capillary number for droplet breakup in the experiments correlates with the interfacial viscoelasticity, and a reformulation of the numerical framework in terms of interfacial elasticity parameters is suggested for future numerical work including other linear flows.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430607
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  • 5
    Electronic Resource
    Electronic Resource
    Unsaturated polyester diol-polyurethane composite networks (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 163-170 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article introduced the formation of an unsaturated polyester/diol-polyurethane hybrid polymer networks(UP/PU HPNs). The phase behavior was examined by the dynamic mechanical properties and the morphology was investigated by transmission microscope(TEM) and atomic force microscopy(AFM). The effect of phase separation on mechanical properties is briefly described as well.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400114
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  • 6
    Electronic Resource
    Electronic Resource
    Phase separation of poly(ether sulfone imide) modified epoxy resin (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 2423-2435 
    Details
    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: Poly(ether sulfone imide)s (PEI) with molecular weight Mn ∼ 104 were synthesized from 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and amine terminated poly(ether sulfone) having molecular weights ranging from Mn ∼ 400 to Mn ∼ 4000. Thus, the PEIs had the same molecular weight but various imide and ether sulfone contents. The PEIs were mixed with a stoichiometric mixture of diglycidyl ether bis-phenol-A (DGEBA)/diamino diphenyl sulfone (DDS). The effect of PEI on the curing reaction of DGEBA/DDS and the morphology of the polymer blend were studied by differential scanning calorimetry (DSC) and optical microscopy. In the DGEBA/DDS/PEI blend with a fixed PEI molecular weight and PEI concentration but with various imide content, the experimental data revealed the PEI with a higher content of ether sulfone had a lower Tg and a better compatibility with solvents and epoxy resins; the curing reaction rate of DGEBA/DDS/PEI was faster for PEI with a higher imide content; the DSC data of cured DGEBA/DDS/PEI showed two Tgs, indicating phase separation between PEI and cured epoxy resins; and the data of optical microscopy showed that the compatibility of PEI with epoxy resins increased with the content of ether sulfone in PEI. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Initial adsorption of trimethylsilane on Ge(100) surfaces (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 113-120 
    Details
    ISSN: 0142-2421
    Keywords: XPS ; x-ray photoelectron spectroscopy ; Ge ; adsorption ; trimethylsilane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Trimethylsilane (TMSiH) was adsorbed onto a Ge(100) surface at a temperature of -150±3°C and x-ray photoelectron spectroscopy (XPS) was used to study the resulting surface species as functions of the TMSiH exposure in Langmuir (L). The core-level C 1s, Si 2p and Ge 3d photoelectrons were monitored after each dosing. It was observed that the C-C bonds are the dominant species formed at the low doses of TMSiH. The second abundant species at the low coverage is the C-Ge bond. This indicated dissociative adsorption of TMSiH molecules onto a clean Ge(100) surface, which is similar to the adsorption of TMSiH molecules onto an Si(100) surface. As the dose increases, the Si-C species gradually increase due to physisorbed TMSiH on top of the C-C- and C-Ge-covered surface. This study clearly reveals the growth processes of TMSiH on a Ge(100) surface. The electronegativities of C, Si and Ge and the bond strengths of C-C, C-Si and C-Ge were invoked to discuss the initial formation of C-C and C-Ge on the Ge(100) surface. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Retardation experiments in glass-forming liquids and their description in terms of the conformon model (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 150-160 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Relaxation in glass-forming liquids as measured by dielectric, by light- and by neutron-scattering experiments can be described with the aid of the conformon model. Conformons behave like bosons which display a photon statistics. Conformons are excited and can also be annihilated. They show a universal reduced energy density distribution, revealing their thermodynamic roots. Each relaxation mode is assumed to be directly connected with a distinct conformon. The coupling is described by an empirical power law. The actual relaxation time distribution is then obtained by scaling each relaxation mode with the same kinetic factor. The relaxation behavior of liquids is therefore self-similar, characterized by individual factors such as the relaxation power, the coupling parameter and the temperature of pressure dependence of the kinetic factor (“shift factor”).
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010470403
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  • 9
    Electronic Resource
    Electronic Resource
    The Electrothermal Enhancement of Propellant Burning by Plasma Injection (1997)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 22 (1997), S. 212-217 
    Details
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A series of experimental demonstrations of plasma injection into a burning propellant interface is presented. The propellant is a nitro-guanidine based material in the form of a right cylinder with a bore along its central axis. It is ignited by a hot-wire system and, when a pre-set pressure is achieved, a second wire is exploded using a high-voltage capacitor discharge circuit. The second wire forms a plasma, precisely at, or well away from the burning interface. Comparing the pressure histories from these different geometries allows the effect of increased burning rate to be separated from Joule heating of the product gases. Analysis of these histories shows a pressure increase over that caused by Joule heating of the products.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19970220406
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of polyimides endcapped with phenylethynylphthalic anhydride (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2141-2149 
    Details
    ISSN: 0887-624X
    Keywords: polyimides ; 4-phenylethynylphthalic anhydride ; thermooxidative stability ; high-temprature MAS NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of high glass transition temperature (Tg 〉 300°C), amorphous, soluble, poly-imide oligomers of controlled molecular weight endcapped with 4-phenylethynylphthalic anhydride endcapping agent is described. The 4-phenylethynylphthalic anhydride was employed to afford a higher curing temperature (380-420°C) which widens the processing window compared to unsubstituted acetylene-endcapped polyimides. The polyimides were synthesized via solution imidization techniques, using the ester-acid of various dianhydrides and aromatic diamines. A “ one-pot” procedure utilizing NMP as the solvent and o-dichlo-robenzene as the azeotroping agent reproducibly produced fully imidized, but yet soluble wholly aromatic polyimides. Thermally cured samples were prepared with gel contents of up to 98% that displayed good solvent resistance. Glass transition temperatures comparable to high molecular weight linear analogs were produced. These polyimides also show excellent thermal stability as judged by thermogravimetric analysis (TGA). Model phenylethynyl imide compounds were synthesized and used to follow and elucidate the nature of the products formed from the phenylethynyl curing by using high temperature magic-angle 13C nuclear magnetic resonance (MAS NMR). Preliminary results indicate that the cure reaction can be followed by MAS NMR. However, the nature of the products being formed during the curing process is difficult to determine by the solid-state MAS NMR alone. Differential scanning calorimetry (DSC) data clearly show that the model system does indeed melt and displays a wide window before the strong cure exotherm is observed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331307
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