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  • 1985-1989  (8)
  • Polymer and Materials Science  (8)
  • Amphibian
  • brain
  • 1
    Electronic Resource
    Electronic Resource
    Dielectric properties of an epoxy resin and its composite I. Moisture effects on dipole relaxation (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 1771-1784 
    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: Dipole relaxation dielectric loss behavior of a fiberglass-epoxy composite has been studied as a function of moisture uptake. A single widely distributed loss peak, centered at -16°C for 10 kHz measurement, is observed in the dry composite. Very low moisture concentrations (〈0.1%) interact with the composite, through either dipole pairing or by inducing chemical changes, to decrease loss intensity. At moisture concentrations from 0.1 to 1.4%, loss peak intensity generally increases with moisture uptake. Over this moisture concentration range water dipoles presumably relax in phase with the epoxy segments or side groups upon which they adsorb. Arrhenius relaxation activation energy decreases, and improved loss peak definition at increasing moisture concentrations is interpreted as indicating resin plasticization by adsorbed moisture. At moisture concentrations above 1.4%, the appearance of a second loss peak suggests formation of a new colloidal or weakly adsorbed moisture phase, as well as the saturation of primary adsorption sites.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070310622
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Preconcentration and determination of lead(II) at crown ether and cryptand containing chemically modified electrodes (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 13-21 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemically modified electrodes (CMEs) containing incorporated crown ether and cryptand ligands as modifiers were evaluated for their ability to preconcentrate metal cations prior to quantitation by conventional voltammetric methods. Stable CMEs were formed for 18-crown-6, dibenzo-18-crown-6, poly(dibenzo-18-crown-6), dibenzo-24-crown-8, and 2.2.2-cryptand by mixing the desired amount of the ligand into carbon paste. The resulting electrodes exhibited complexing capabilities that were similar to those of the free ligands. In particular, the CMEs were very reactive toward Pb2+ and Hg2+. Pb2+ uptake was sufficiently strong that a detection limit of 1 μM was obtained following a 20-sec exposure to the sample and transfer to a blank electrolysis solution for differential pulse voltammetric analysis. Accurate quantitation of micromolar levels of Pb in water and urine reference standards was achieved at the CMEs by means of a simple procedure requiring minimal sample preparation. Finally, the analytical characteristics of CME preconcentration were directly compared to those of the electrodeposition approach ordinarily employed in stripping voltammetry.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010104
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    LCEC determination of the copper protein ceruloplasmin in human serum at a polyaniline chemically modified electrode (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 133-140 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chemically modified electrode (CME) for use in the amperometric detection of the copper protein ceruloplasmin was constructed by electropolymerizing a polyaniline coating onto glassy carbon. The resultant CME, used in liquid chromatographic detection, gave an electrocatalytic response for ceruloplasmin reduction that could be employed directly by itself or could be greatly enhanced by the addition of Fe2+ to the mobile phase. Optimum detection was achieved at an applied potential of -0.10 V vs. Ag/AgCl and with 1 mM Fe2+ in the mobile phase. The detection limit obtained under these conditions was 2 pmol injected, and the response was linear for concentrations at least 2 orders of magnitude higher. The CME retained more than 90% of its initial response to ceruloplasmin over 30 hours of continuous exposure to the chromatographic flowstream. In practice, the liquid chromatography CME response was sensitive and selective enough to permit quantitation of physiologically relevant levels of ceruloplasmin in human serum with no sample pretreatment other than preinjection filtration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010208
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The ligation and flexibility of four-arm DNA junctions (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1337-1352 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four-arm DNA branched junctions are stable analogs of Holliday recombination intermediates, constructed from oligonucleotides. The conformational flexibility of junctions can be estimated by ligating them together and determining the set of closed macrocyclic products that are obtained among the linked units. We have performed a series of these experiments, using pairs of sticky ends that flank each of the six angles of a four-arm junction. In every case, the ligated junctions are separated by 20 nucleotide pairs, about two turns of DNA. All expected short linear products, starting with dimers, are observed for all ligations. All ligations result in a macrocyclic series that begins with trimers. Thus, over the time scale of these reactions, the arms of this junction can form angles as low as 60°. The response of this junction to torsional stress has been tested in a companion experiment. A smaller version of this same four-arm junction has been oligomerized so that successive junctions are separated by 16 nucleotide pairs, approximately 1.5 turns of DNA. If junctions were as rigid as linear duplex DNA, this system would not be expected to form macrocycles until the continuous chain approaches the Shore-Baldwin limit, ca. 160 base pairs. However, macrocyclic closure is observed in a regular ligation ladder, starting from tetramers. Model building suggests that the most likely explanation for the observed closure is that the junction adopts two different conformations, which bend the continuous strand toward opposite grooves. The junction structures formed by these ligations represent fluctuations from equilibrium structures.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270902
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Craze growth and healing in polystyrene (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 2541-2560 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of craze growth and craze healing were studied by dark-field optical microscopy in monodisperse molecular weight polystyrene (PS) that varied in molecular weight from 88,000 to 1,334,000. The following observations were made. (1) G1 the virgin growth rate, decreased rapidly with increasing molecular weight until Mn ∼ 200,000 and then remained constant. (2) G1 decreased with increasing craze density. (3) The growth rates of approaching craze tips decreased when the craze tips overlapped, and the effect was less for crazes whose parallel growth paths were greater than 40 μm apart. (4) Complete craze healing was observed by comparison of the nucleation times, τ2, and growth rates, G2, of healed individual crazes with the craze kinetics of the virgin sample. (5) The extent of healing was characterized using four cases in which τ and G were measured as a function of healing time, temperature, constant stress, and molecular weight. (6) Craze healing times were found to increase with molecular weight and were analyzed in terms of the modified molecular weight of the craze zone. (7) Significant bond rupture was determined to occur during crazing by comparison of healing times with stress relaxation and diffusion data. (8) Craze healing studies provide insight into both crack healing and fracture of glassy polymers.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090251209
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Dielectric properties of an epoxy resin and its composite II. Solvent effects on dipole relaxation (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 2293-2303 
    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: Dipole relaxation dielectric loss behavior of a fiberglass-epoxy composite has been studied following submersion in polar and nonpolar organic solvents as well as in acidic and basic aqueous solutions. Certain adsorbed organic solvents, such as 1,2-dichloroethane, had little influence on the epoxy relaxation behavior. Other solvents, including chloroform, increased the composite relaxation intensity and shifted the temperature-frequency region over which the relaxation occurred. Both the amount of solvent uptake and the degree of interaction of solvent molecules with epoxy polar functional groups appear to control the amount of relaxation behavior perturbation. Arrhenius activation energies for relaxation were lowered by solvent uptake from the dry composite value of 18 kcal/M to between 6 and 16 kcal/M, depending on the solvent adsorbed. Submersion in methanol and chloroform sharply increased the direct current conductivity of the composite. Two molar acidic and basic solutions had little influence on composite dipole relaxation behavior other than the well known behavior associated with moisture uptake.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070330703
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Liquid chromatography and electrochemical detection of alditols and acidic sugars at a cobalt phthalocyanine-containing chemically modified electrode (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 389-395 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemically modified carbon paste electrodes containing incorporated cobalt phthalocyanine (CoPC) were shown to exhibit an electrocatalytic response for the oxidation of carbohydrate derivatives from the alditol and aldonic, uronic, and aldaric acid families. The electrocatalysis, which is similar to that previously seen for simple carbohydrates, resulted in the electrolysis of these compounds between +0.4 and +0.6 V vs. Ag/AgCl where Co(II)PC is oxidized to Co(III)PC. The response was greatest for the alditols and decreased from the aldonic to the aldaric acids. When used to quantify these compounds following anion exchange chromatography, detection limits at +0.42 V ranged from 10 pmol for the alditols to the nanomole level for some of the aldaric acids.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010503
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Capacitor-Discharge Initiation of a Detonator containing a vacuum-deposited thin-film chromium bridge (1988)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 13 (1988), S. 129-134 
    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: An experimental program is described in which the capacitor-discharge initiation characteristics of a detonator containing a vacuum-deposited thin-film chromium bridge were studied. The objective of the effort was to define the conditions that would result in overall function times of 10 μs or less. The threshold initiation energy of the detonator was in the range of 11.5 mJ-20.0 mJ. Consistent performance was obtained from a firing energy of 54 mJ, which was achieved by a 5-μF capacitor charged to 147 V. Under these conditions, the average overall function time was 4.2 μs, with a standard deviation of 0.2 μs. Other tests showed that at higher capacitances and lower voltages the function time increased substantially and became more nonreproducible, even though the stored energy was considerably above the threshold value.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19880130502
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    Paper (German National Licenses)
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