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  • 1
    Electronic Resource
    Electronic Resource
    The effect of polymer structure on the efficiency of acid generation from triarylsulfonium salts (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 309-316 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The irradiation of triarylsulfonium salts produces Brönsted acid along with diarylsulfide products. This photochemical conversion has been applied in several areas of polymer film technology including imaging and curing of films. This paper discusses the dependency of acid generation in polymer films on the structures of both polymer and sulfonium salt. The results suggest that the structures of both polymer and sulfonium salt. The results suggest that the efficiency of acid generation is dependent on the interaction between polymer structure and the charged sulfonium salt. Studies have been carried out for both deep-UV and electron beam irradiation of polymer films. The variation of acid generation with sulfonium salt loading has been determined. Finally the effect of accelerating voltage on the amount of acid generation following electron beam irradiation is discussed. ESR spectroscopy has been done on films after uv irradiation to determine the nature of the radicals which are formed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290303
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  • 2
    Electronic Resource
    Electronic Resource
    Customized neonatal incubator for measurement of platelet-artificial microvascular graft interactions under controlled flow, temperature, and transmural pressure (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 3 (1992), S. 1-7 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A neonatal incubator has been custom modified to enable measurement of initial platelet retention on biomaterials in vitro under clinically relevant hemodynamic conditions. To calibrate this device, platelet retention on several materials having microconduit geometry (0.7-1.0 mm i.d.) has been measured after perfusion with citrated whole blood (containing 111 Indium-labelled platelets) at a shear rate of 312 s-1, 37°C, and 80 cm H2O transmural pressure. The relative reactivity of these materials toward platelets was: glass 〈 Fibrinogen(Fg)-coatedglass 〈 Fg-coated polyethylene 〈 polyethylene ∼ = Expanded polytetrafluoroethylene. Interindividual variation is relatively large (coefficient of variation = 35.5 ± 9.3%), but comparison to intraindividual controls reduces the variability to 14.8 ± 10.3%, a level which is suitable for economical testing of platelet retention to biomaterials in the presence or absence of drugs. This approach may have particular value in the study of the mechanism of platelet interactions with artificial microvascular grafts under perfusion conditions which are relevant to the first moments of flow, when initial platelet deposition occurs.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770030102
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Rheological investigation of shear-induced structure changes in multiblock copolymers (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 663-673 
    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: Styrene-butadiene multiblock copolymers were examined with both newly introduced and established rheological techniques and by transmission electron microscopy (TEM) to evaluate shear-induced structural changes in these polymers. Transient rheological tests (based on superposed flow principles) were developed which probed structural changes that occur in the copolymers during and at the cessation of steady shear. Data from these tests indicated that for the cylindrical morphology copolymer (SB1) there were structural changes occurring during steady shear that were recovered upon cessation of shear. The recovery process took place on time scales that could be significant in processing. The lamellar morphology material (SB2) did not exhibit this recovery behavior. Longer-term structure changes were investigated using established techniques and showed differences between the cylindrical and lamellar copolymers. When tested at 210°C, peaks in tan δ occurred at 30 rad/s for SB1 and at 0.5 rad/s for SB2 with saturation strain levels of 150 strain units (SU) for SB1 and 80 SU for SB2. TEM analysis of SB2 indicated that, although rheological changes are significant up to 80 SU, better alignment of the domain morphology can be achieved at moderately low strains of 7 SU. This indicates that the copolymers' rheological changes, which occur as a result of steady shearing, may not be due entirely to domain alignment, but may also be due to more local molecular rearrangements (e.g., chain disentanglement). © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Spatial and temporal changes in compliance following implantation of bioresorbable vascular grafts (1992)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 1449-1461 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Compliance matching between the host vessel and vascular grafts used for smalldiameter arterial replacements is thought to be important for longterm patency. However, currently available grafts elicit fibroplastic reactions, resulting in decreasing compliance with time after implantation. Bioresorbable prostheses elicit ingrowth of myofibroblasts containing abundant contractile elements. This led us to investigate whether compliance of implanted bioresorbable prostheses decreased as a function of time and if the kinetics of change correlated with the progession of tissue ingrowth. Woven polyglactin 910 prostheses (10 mm × 4 mm i.d.) were implanted into adult NZW rabbit infrarenal aortas and replicates were harvested serially through 8 months. Control grafts were implanted, and immediately resected. Dynamic compliance was measured a t 1-mm axial increments along each explant using a pulse duplicator apparatus which exposed the harvested samples to realistic pulsatile hemodynamics. Compliance was calculated for proximal, mid, and distal segments of each graft and averaged at each time point by grouping into control (zero time, n =3), early (1-4 weeks, n = 13), and late (6-36 weeks, n = 9) explant periods. At late explant periods both proximal and distal compliance were significantly greater than mid graft compliance (p ≤ .02 and p ≤ .03, respectively). There was a significant increase in proximal compliance between early and late explant times (p ≤ .01). Measured increases in mid and distal segment compliance over time did not reach statistical significance. Myofibroblast laden tissue ingrowth into the inner capsule followed macrophage phagocytosis and was nearly complete prior to the time that an increase in compliance was demonstrated. Thus since the major histologic episodes precede the change in compliance, these are not likely initiated by this biomechanical change. We hypothesize the graft resorption coupled with the ingrowth of more compliant tissue likely leads to the increased compliance of the graft material. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820261105
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  • 5
    Electronic Resource
    Electronic Resource
    Detection of glucose at a rotating gold composite electrode by pulsed amperometric detection (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 443-446 
    Details
    ISSN: 1040-0397
    Keywords: Glucose ; Composite electrodes ; Pulsed amperometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Segregated composite electrodes mimic microelectrode ensembles. In this preliminary report, the use of a rotating gold-polychlorotri- fluoroethylene (or Kel-F, a 3M Company polymer) composite electrode in combination with pulsed amperometric detection (PAD) is described for the detection of glucose. Comparisons are made with results obtained at a solid gold disk electrode. The composite electrode exhibits a higher signal and a lower background than does the solid gold electrode. In terms of current density, the enhancement of the signal above the background is over 3-fold, similar to that observed with segregated graphite composite electrodes used in a constant potential mode. Little or no glucose signal is observed at either the solid gold or the gold composite electrode when employed in the constant potential mode. In the PAD mode, the signal is stable for periods in excess of an hour.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140080508
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  • 6
    Electronic Resource
    Electronic Resource
    Seven new organic superconductors in the system (ET)2M(CF3)4(solvent) (M = Cu, Ag): effect of solvent replacement**This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences, under contract No. W-31-109-ENG-38. Research at the University of Cologne was supported by the Fonds der Chemischen Industrie and the Ministerium für wissenschaft and Forschung des Landes Nordrhein-Westfalen (Arbeitsge-meinschaft Fluorchemie). We thank Dr. Patricia M. Keane for technical assistance with EDAX studies. M. E. K. and S. A. S. are undergraduate research participants from Hope College (Holland, MI) and Mansfield University (Mansfield, PA) respectively, sponsored by the Argonne Division of Educational Programs. (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 634-639 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950070705
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  • 7
    Electronic Resource
    Electronic Resource
    Ribozyme chemogenetics (1998)
    New York : Wiley-Blackwell
    Biopolymers 48 (1998), S. 65-81 
    Details
    ISSN: 0006-3525
    Keywords: nucleotide analogue interference mapping ; phosphorothioate ; group I intron ; interference suppression ; RNA ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this review I will outline several chemogenetic approaches used to determine the chemical basis of large ribozyme function and structure. The term chemogenetics was first used to describe site-specific functional group modification experiments in the analysis of DNA-protein interactions. Within the past few years equivalent experiments have been performed on large catalytic RNAs using both single-site substitution and interference mapping techniques with nucleotide analogues. While functional group mutagenesis is an important aspect of a chemogenetic approach, chemical correlates to genetic revertants and suppressors must also be realized for the genetic analogy to be intellectually valid and experimentally useful. Several examples of functional group revertants and suppressors have now been obtained within the Tetrahymena group I ribozyme. These experiments define an ensemble of tertiary hydrogen bonds that have made it possible to construct a detailed model of the ribozyme catalytic core. The model includes a functionally important monovalent metal ion binding site, a wobble-wobble receptor motif for helix-helix packing interactions, and a minor groove triple helix. © 1998 John Wiley & Sons, Inc. Biopoly 48: 65-81, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Deuterium Isotope Effects during RDX Combustion: Mechanistic burn rate-controlling step determination (1991)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 16 (1991), S. 279-286 
    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: High pressure (500 psig/3.55 MPa and 1000 psigl6.99 MPa) burn rate comparisons from the combustion of solid RDX (hexahydro- 1.3,.5-trinitro-1,3,5-triazine) and perdeuterio-labeled RDX-dh cylindrical pressed pellets reveals a large kinetic deuterium isotope cffect (KDIE). This experimental KDIE confirms that chemical reaction kinetics are a significant mechanistic factor in controlling the inherent RDX burn rate and further shows the six-membered RDX hcterocycle's rate-controlling mechanistic step during com- bustion is the same as that previously reported for its larger eight-membered HMX (octahydro-l.3,5,7-tetranitro-l.3.5,7 tetrazocine) homologuc. As with HMX. This experimental KDTE approach also demonstrates a direct mechanistic relationship between RDX's higher order cornbustion regime and its ambient pressure thermochemical decomposition process.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19910160605
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetic Deuterium Isotope Effects in the combustion of formulated nitramine propellants (1994)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 19 (1994), S. 42-58 
    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: The kinetic deuterium isotope effect was used to investigate the rate-limiting process in the combustion of formulated nitramine propellants. Model propellant formulations containing either octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), or their deuteriated analogues were pressed into pellets and burned under nitrogen pressure in a window bomb. The magnitudes of the observed deuterium isotope effects indicate that the HMX and RDX exert significant control over the combustion phenomenon of the propellants studied. Furthermore, assuming a consistent mechanism between decomposition and combustion, the observed isotope effects suggest that a carbon-hydrogen bond rupture in HMX or RDX is the rate-controlling step in the combustion of the model nitramine propellants. Observed isotope effect values for HMX-CW5 and RDX-CW5 formulated propellants at 1000 psig (6.99 MPa) pressure were 1.29 ± 0.09 and 1.24 ± 0.07, respectively, compared to a theoretical estimate of 1.29 for a primary effect due to C—H bond rupture at 673 K.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19940190108
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  • 10
    Electronic Resource
    Electronic Resource
    Heat of Fusion for 1,3,5,5- Tetranitrohexahydropyrimidine (DNNC) and its DNNC-d6 deuterium labelled analogue (1995)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 20 (1995), S. 1-4 
    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: The heat of fusion for DNNC (1,3,5,5-tetranitrohexahydropyrimidine) and its DNNC-d6 analogue compound have been determined using differential scanning calorimetry analysis. No significant difference in the DNNC and DNNC-d6 heat of fusion values was detected at the 95 and 99 percent student t confidence levels. Melting points were also determined for the subject compounds using this analysis technique. These melting points are compared to literature values obtained by conventional methods.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19950200102
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