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  • Polymer and Materials Science  (2)
  • Hippocampus  (1)
  • 1995-1999  (3)
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  • 1
    ISSN: 0887-6266
    Keywords: tensile drawing ; morphology ; polybutylene ; terephthalate ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The concept of the drawing of a molecular network has been employed to derive a total network draw ratio from the combination of the two deformations occurring in the production of poly(butylene terephthalate), PBT, fibers by the consecutive processes of melt spinning and cold drawing. The mechanical properties of PBT can then be more readily explained in terms of increases in this total network draw ratio. However, the preorientation and crystallization that occurs in the melt-spinning process can occur at different strain rates and temperatures, depending on the wind up speed employed, on the extensional viscosity of the polymer, and on the variation of the extensional viscosity with temperature. Therefore, for polymers such as poly(butylene terephthalate), which can exist in two crystalline forms, the morphology of the final drawn fiber might be expected to depend on the first melt-spinning stage of the process as well as on the total network draw ratio. In this work, density, birefringence, mechanical measurements, and WAXD measurements, which have been made on the melt-spun fibers and on the drawn fibers, are described. Small differences in some of the drawn yarn mechanical properties at the same overall network draw ratio are related to the crystallinity and in particular to differences in the proportion of the α and β phases present in the drawn yarn. These in turn are related to differences in the temperature and stress during melt spinning and drawing. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2465-2481, 1997
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Direct depth profiling techniques to date have largely lacked the necessary depth resolution to investigate interfacial phenomena of the order of the bulk correlation length (5 - 10 nm for a wide range of systems). Here we investigate the optimal spatial resolution and depth of probe that may be attained for composition  -  depth profiling of polymeric samples via nuclear reaction analysis (NRA) using the 2H(3He, 1H)4He reaction. We find that the spatial resolution can be greatly improved by using a grazing incidence geometry of the incident 3He beam on the sample, and analyzing the emitted protons in a backwards direction. This results in spatial resolutions down to about 3 nm at the sample surface, compared to a value of some 7 nm or more previously reported in earlier studies when emitted α-particles were detected in the forward direction. At the same time the depth to which samples can be profiled via the backwards emitted protons may be considerably extended relative to the α-particle detection mode, when the 3He beam impinges on the sample surface at normal incidence (up to about 4 μm into the sample for incident energies of 1.2 MeV in the proton-detection mode compared to only 1 μm for the equivalent α-particle detection mode).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1912
    Keywords: Key words Ethanol ; Acetylcholine ; Scopolamine ; Hippocampus ; Microdialysis ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using the microdialysis technique and sensitive HPLC procedures for the determination of acetylcholine (ACh) and ethanol, we investigated the release of ACh in rat hippocampus after acute ethanol administration. Systemic administration of ethanol (0.8 and 2.4 g/kg i.p.) led to peak ethanol concentrations of 21 and 42 mM in the hippocampus, respectively. The high dose caused a long-lasting inhibition of basal ACh release by up to 33%. Local infusion of scopolamine (1 µM) enhanced hippocampal ACh release up to eightfold in the presence of neostigmine (10 µM), and this stimulated release was also inhibited after systemic ethanol administration (by up to 45%). The low dose of ethanol (0.8 g/kg) led to a delayed stimulation of hippocampal ACh release. A stimulatory effect on ACh release was also observed when ethanol (50–100 mM) was infused directly into the hippocampus or into the septal area, i.e. to the origin of the cholinergic septohippocampal pathway; thus, the stimulatory effect may be mediated by a direct effect on cholinergic fibres. We conclude that ethanol exerts dual modulatory effects on the activity of the septohippocampal cholinergic fibres, depending on the dose and the site of administration. It is suggested that the inhibition of hippocampal ACh release by intoxicating doses of ethanol may contribute to the well-known cognitive and amnesic effects of ethanol intake.
    Type of Medium: Electronic Resource
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