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  • Polymer and Materials Science  (8)
  • Anterior cruciate ligament  (1)
  • Atomic, Molecular and Optical Physics  (1)
  • Biopsy, endomyocardial  (1)
  • 1
    ISSN: 1432-2277
    Keywords: Heart transplantation, endomyocardial biopsy ; Biopsy, endomyocardial ; Endomyocardial biopsy, heart transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Since 1989, the immunosuppressive regimen used in all heart transplant (HTx) patients at our center has consisted of a combination of cyclosporin, azathioprine, and prednisone. No prophylactic cytolytic agents have been given. One hundred consecutive patients were followed for periods of 4–56 months (mean 27 months). The incidence of rejection was so low in the initial 18 patients that we felt confident about reducing the number of routine endomyocardial biopsies (EMBs) that were performed. The mean number of EMBs in this subgroup was 10 (median 11). In the next 20 patients, EMB was performed routinely on only three occasions during the 1st post-transplant year (at 2, 4, and 8 weeks). In the subsequent 62 patients, EMB was performed on post-transplant days 10, 20, 30, and 60. Further EMBs were performed after acute rejection episodes had been treated. No noninvasive methods of diagnosing rejection were employed. In 82 consecutive patients, therefore, the mean number of EMBs within the 1st year was five per patient (median four), with 58% undergoing fewer than five EMBs and 25% requiring more than five EMBs. In the entire group of 100 patients, the mean number of EMBs was 5.9. The incidence of acute rejection requiring increased therapy was 24%. Only 7% required i.v. steroids, two of whom (2%) also required ALG and/or OKT3, with 17% requiring increased oral immunosuppression alone. Actuarial survival was 98% at 30 days, 94% at 1 year, and 92% at 2 years. It is possible that we may have missed acute rejection episodes that resolved spontaneously. However, the excellent mediumterm results would suggest that any such rejection episode did not progress to become hemodynamically significant. It may be, therefore, that when an effective immunosuppressive regimen is utilized, the number of EMBs performed at many centers is excessive.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Knee surgery, sports traumatology, arthroscopy 6 (1998), S. S20 
    ISSN: 1433-7347
    Keywords: Key words Graft excursion ; patterns ; Endoscopic reconstruction ; Anterior cruciate ligament
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract The effect of femoral guide rotation in endoscopic anterior cruciate ligament (ACL) reconstruction is reviewed based on a previous report. The effect of varied offsets of the femoral guide (5.5 and 7.0 mm) are described. This is one of the few isometry studies to evaluate the knee through a practically full range of motion (0°–120°). A 7-mm offset guide rotated to the 12 : 00 position yields the best single fiber and graft excursion patterns (P 〈 0.05). A 5.5-mm offset guide yields inferior single fiber and graft excursion patterns. Single fiber and graft isometry are similar but not identical in endoscopic ACL reconstruction. Centering the single fiber in the tibial tunnel has little effect on isometry patterns, demonstrating that the more posterior tibial positions needed for endoscopic reconstruction are acceptable from an isometry standpoint.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 985-991 
    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 effect of zinc catalysts on the hydrolytic depolymerization of polyethylene terephthalate (PET) melts in excess water was studied using a 2-L stirred pressure reactor at temperatures of 250, 265, and 280°C. The main products of the reaction were found to be terephthalic acid, ethylene glycol, and diethylene glycol. Rate constants were calculated from initial rate data at each temperature and found to be about 20% greater than the corresponding rate constants for uncatalyzed hydrolysis. The catalytic effect of zinc, as well as sodium, salts is attributed to the electrolytic destabilization of the polymer-water interface during hydrolysis. The depolymerization rate data at 265°C were found to fit a kinetic model proposed earlier for the uncatalysed hydrolysis of PET. The effect of zinc and sodium salts on the activation energy of hydrolysis, or on the formation of ethylene glycol monomer is unclear. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 1731-1740 
    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 reaction of poly(ethylene terephthalate) (PET) melts with ethylene glycol was examined in a pressure reactor at temperatures above 245°C. The reaction rate was found to depend on temperature and on the concentrations of liquid ethylene glycol and of ethylene diester groups in the polymer. A kinetic model proposed for the initial period of the reaction was found to be consistent with experimental data. It was found that internal catalysis by ethylene glycol does not play an important role in the glycolytic depolymerization of PET. The rate constants for glycolysis were calculated for three different temperatures, yielding an activation energy of 92 kJ/mol. Zinc salts, which have a catalytic effect on glycolysis of PET below 245°C, do not appear to influence glycolysis rates above that temperature. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 2133-2140 
    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 thermolysis of 60/40 mixtures of polyethylene (PE) and polystyrene (PS) was investigated at temperatures below 440°C. Liquid yield from the mixture, 84.1%, was comparable to yields obtained with the individual polymers. The yields of styrene monomer, 57.1%, and α-olefins, 27.7%, increased over those obtained when the polymers were processed individually. A significant interaction was observed between the polymers in which the addition of PS enhanced the rate of thermolysis of PE. It is proposed that this enhancement was due to the abstraction of hydrogen from the PE fraction by polystyryl radicals. The result of this effect is to increase the rate of volatile production from the PE and increase the solubility of the residue in chloroform. The data also support a mechanism for dimer production other than the generally accepted 1,3 transfer. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 443-451 
    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 hydrolytic depolymerization of molten PET in excess water was studied using a 2 L stirred pressure reactor at temperatures of 250, 265, and 280°C. Rate constants for hydrolysis are calculated from the initial rate data. At initial water: PET charge ratios (w/w) exceeding 5.1, essentially complete depolymerization to monomer is possible at 265°C. At lower water: PET initial charges, an equilibrium is established. The equilibrium constants are calculated for 2 g water/g PET at three temperatures. A kinetic model is proposed to describe the hydrolysis reaction. The model is shown to fit experimental data and to yield good predictions for the equilibrium concentration of carboxyl groups. Carboxyl-group concentrations are measured using an end-group analysis technique. Potentiometric titrations are carried out in one of two solvent systems, dimethylphenol:chloroform or dimethylsulfoxide, depending on the extent of hydrolysis. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 843-851 
    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 was recovered from polystyrene (molecular weight of 138,000) by thermolysis in a nitrogen atmosphere at temperatures between 368 and 407°C. The results were independent of the initial weight of polystyrene, which was varied between 30 and 480 g. Up to 90% of the polystyrene was converted to liquid products. The liquid products had a styrene concentration as high as 90% and the styrene yield increased with temperature. Above 390°C, the residue left in the reactor (less than 30% of initial polystyrene charge) consisted mainly of styrene monomer, dimer, and trimer (MW of 190). The kinetics support a first-order reaction with regard to the rate of production of volatiles. The activation energy was estimated to be 166.5 kJ/mol. © 1995 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2045-2056 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of polyglycollide [poly(methylene carboxylate)] has been studied over the temperature range 250-400°C by using the combined kinetic and analytical technique previously described. The results obtained from thermogravimetry and product analysis were in many ways similar to those from previous work involving higher poly-α-esters. Thus the reaction was predominantly first-order and the major degradation product was glycollide monomer. This confirms the observations of Carothers and is best interpreted in terms of an intramolecular ester interchange process. Kinetic studies have shown that the first-order rate constant k is related to temperature T by the expression: \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 2.1 \times 10^8 e^{ - 32,{{600} \mathord{\left/ {\vphantom {{600} {RT}}} \right. \kern-\nulldelimiterspace} {RT}}{\rm sec}^{ - {\rm 1}} } $$\end{document} The results from gas evolution analysis showed consistent and marked deviation from first-order behavior. This is interpreted in terms of the greater sensitivity of this technique to traces of acidic degradation products. Solution viscometry was used to demonstrate the effect of degradation conditions on molecular weight change in both thermogravimetric and gas evolution techniques.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 123-146 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of poly(3-pentylidene carboxylate) has been studied kinetically over the temperature range 200-300°C using thermogravimetry, gas evolution analysis, and rheogoniometry together with isolation and analysis of the reaction products. The observed behavior is completely different from that previously reported for poly(isopropylidene carboxylate) and poly(methylene carboxylate). Whereas in the latter cases the decomposition occurs by a first-order intramolecular ester interchange process characterized by an activation energy in the region of 27 kcal mole-1, poly(3-pentylidene carboxylate) decomposition occurs by random chain scission superimposed on a first-order hydrogen abstraction process. The activation energy associated with this decomposition reaction is in the region of 47 kcal mole-1, and the major degradation products are cis- and trans-2-ethyl crotonic acid.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 225-233 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The goal of obtaining accurate potential energy surfaces for the study of intermolecular forces is of fundamental importance. In this article, we propose a new method to generate a set of virtual orbitals optimized in such a way to give very compact valence bond (VB) wave functions with the same accuracy of very large VB calculations. These optimized virtual orbitals, completely free from BSSE, are developed in the framework of spin coupled theory. Test calculations on the He ··· LiH system are presented together with a comparison with previous studies. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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