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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 125-139 
    ISSN: 0887-6266
    Keywords: poly-4-methyl-entene-1 ; PT phase diagram ; amorphization under pressure ; disordering on cooling ; thermodynamic anomalies ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report some highly unusual phase behavior, of general implication for condensed matter, on the polymer poly(4-methyl-pentene-1) (P4MP1) induced by changes in pressure and temperature, as observed in situ by x-ray diffraction. Upon increasing pressure beyond a threhold, the polymer, crystalline under ambient conditions, loses its crystalline order isothermally, passing through a continuously varying sequence of mesomorphic states, the process being reversible. This behavior is observed in two widely separated temperature regions, suggesting, for the first time in a single component system, the possibility of reentrant liquid-crystal and amorphous phases. At the upper temperature region (ca. 250°C) there is a consecutive increase and decrease of melting point with pressure. In the lower temperature region (room temperature) the pressure converts the crystal into an amorphous-like glass obviating the need for going through the melt first, and this in a reversible manner. The latter pressure-induced disordered phase converts into crystal on raising the temperature, and reverts to the glassy, disordered phase on lowering the temperature. Some aspects of this behavior have been found quite recently in water-ice and silica but the process of “melting on cooling” has no precedent in any known system. Other unexpected findings include a new pressure-induced modification of P4MP1 with a one-way only entry with temperature, but full reversibility with pressure leading to a triple point in the PT phase diagram. The above highly uncommon results are putting several prevailing preconceptions to test which are being scrutinized. In the course of it some early expectations on general phase behavior, allowing among others for reentrant phases in one component systems, are being invoked as potentially appropriate for certain polymeric systems, if not for condensed matter in general. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2013-11-21
    Description: Aims Autonomic dysfunction is a feature of chronic heart failure (HF). This study tested the hypothesis that chronic open-loop electrical vagus nerve stimulation (VNS) improves LV structure and function in canines with chronic HF. Methods and results Twenty-six canines with HF (EF ~35%) produced by intracoronary microembolizations were implanted with a bipolar cuff electrode around the right cervical vagus nerve and connected to an implantable pulse generator. The canines were enrolled in Control ( n = 7) vs. VNS therapy ( n = 7) or a crossover study, with crossovers occurring at 3 months (C x VNS, n = 6; VNS x C, n = 6). After 6 months of VNS, LVEF and LV end-systolic volume (ESV) were significantly improved compared with Control (EF Control –4.6 ± 0.9% vs. VNS 6.0 ± 1.6%, P 〈 0.001) and (ESV Control 8.3 ± 1.8 mL vs. VNS –3.0 ± 2.3 mL, P = 0.002. Plasma and tissue biomarkers were also improved. In the crossover study, VNS also resulted in a significant improvement in EF and ESV compared with Control (EF Control –2.3 ± 0.65% vs. VNS 6.7 ± 1.1 mL, P 〈 0.001 and ESV Control 3.2 ± 1.2 mL vs. VNS –4.0 ± 0.9 mL, P 〈 0.001). Initiation of therapy in the Control group at 3 months resulted in a significant improvement in EF (Control –4.7 ± 1.4% vs. VNS 3.7 ± 0.74%, P 〈 0.001) and ESV (Control 1.5 ± 1.2 mL vs. NS –5.5 ± 1.6 mL, P = 0.003) by 6 months. Conclusions In canines with HF, long-term, open-looped low levels of VNS therapy improves LV systolic function, prevents progressive LV enlargement, and improves biomarkers of HF when compared with control animals that did not receive therapy.
    Print ISSN: 1388-9842
    Electronic ISSN: 1879-0844
    Topics: Medicine
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