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  • Polymer and Materials Science  (14,223)
  • Magnetic resonance imaging  (749)
  • 1
    Electronic Resource
    Electronic Resource
    Dielectric investigation of isotropic and anisotropic solutions of hydroxypropyl cellulose in dioxan (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 34 (1994), S. 363-367 
    Details
    ISSN: 0959-8103
    Keywords: hydroxypropyl cellulose ; dioxan ; dielectric behaviour ; refractive index ; isotropy ; 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 dielectric behaviour of hydroxypropyl cellulose in dioxan has been studied at 10-50°C over a range of concentration of 10-55 wt% to include the isotropic and anisotropic phases. The study showed that the loss maximum ε″max magnitude of polarization ε0 - ε∞ relaxation time 1/2πfm degree of broadening of the absorption curves 1-h or α, and the mean-square dipole moment 〈gμ2〉, steadily increase with concentration up to 42 wt%, above which a rapid decrease takes place. This indicates that the isotropic solution transforms to an anisotropic solution with a smaller mean dipole moment. The critical concentration is realized to be temperature invariant. This was evidenced by measuring the refractive index of solutions covering the same concentration and temperature ranges.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210340402
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric investigation of isotropic and anisotropic solutions of cellulose acetate in dioxane (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 27-32 
    Details
    ISSN: 0959-8103
    Keywords: cellulose acetate ; dioxane solutions ; dielectric behaviour ; anisotropy ; 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 dielectric and optical characteristics of a sample of cellulose acetate (DS = 2.45) in dioxane solutions were studied at 10-50°C of concentration 10-50 wt% to include both isotropic and anisotropic phases. The study showed that the loss maximum, εmax″, magnitude of polarization, (ε0 - ε∞), static dielectric constant, ε0, time of relation, (2πfm)-1, and refractive index, nD, steadily increase with concentration up to the critical concentration (41 wt%) and then decrease. The mean-square dipole moment, 〈gμ2〉, decreases steadily up to the critical concentration then remains nearly constant, indicating that the isotropic solution changes to anisotropic, with smaller mean-square dipole moment. Comparison between the results of cellulose acetate (CA) and those of hydroxypropyl cellulose (HPC) reveals that, at the critical concentration in dioxane, the cholesteric structure of HPC possesses a greater mean-square dipole moment with higher temperature coefficient than does CA. The activation energy of the relaxation process for hydroxypropyl cellulose is higher, indicating a greater intrachain interaction compared with cellulose acetate.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210370103
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  • 3
    Electronic Resource
    Electronic Resource
    MRI after successful lumbar discectomy (1996)
    Springer
    Neuroradiology 38 (1996), S. S90 
    Details
    ISSN: 1432-1920
    Keywords: Key words Spine ; Intervertebral discs ; Magnetic resonance imaging ; Spinal surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our aim was to establish the normal range of MRI findings after successful lumbar discectomy. We prospectively examined 34 consecutive patients with an excellent clinical outcome by MRI 6 weeks and 6 months after surgery. All examinations included sagittal and axial spin-echo (SE) T1-weighted images before and after intravenous gadolinium-DTPA and fast SE T2-weighted images. Contrast enhancement along the surgical tract was seen in all patients 6 weeks and 6 months after surgery. After 6 months minimal or no mass effect on the dural sac by epidural scar was seen. In 20 % of patients there was recurrent disc herniation, with mass effect. Enhancing nerve roots were seen in 20 % of patients 6 weeks postoperatively, and half of these were associated with recurrent disc herniation at the same side. None of these patients still showed nerve root enhancement 6 months after surgery. Postoperative MRI studies must be interpreted with great care since the features described in the failed back surgery syndrome are also found, to some extent, in asymptomatic postoperative patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050929
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  • 4
    Electronic Resource
    Electronic Resource
    MRI after successful lumbar discectomy (1996)
    Springer
    Neuroradiology 38 (1996), S. S90 
    Details
    ISSN: 1432-1920
    Keywords: Spine ; Intervertebral discs ; Magnetic resonance imaging ; Spinal surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our aim was to establish the normal range of MRI findings after successful lumbar discectomy. We prospectively examined 34 consecutive patients with an excellent clinical outcome by MRI 6 weeks and 6 months after surgery. All examinations included sagittal and axial spin-echo (SE) T1-weighted images before and after intravenous gadolinium-DTPA and fast SE T2-weighted images. Contrast enhancement along the surgical tract was seen in all patients 6 weeks and 6 months after surgery. After 6 months minimal or no mass effect on the dural sac by epidural scar was seen. In 20% of patients there was recurrent disc herniation, with mass effect. Enhancing nerve roots were seen in 20% of patients 6 weeks postoperatively, and half of these were associated with recurrent disc herniation at the same side. None of these patients still showed nerve root enhancement 6 months after surgery. Postoperative MRI studies must be interpreted with great care since the features described in the failed back surgery syndrome are also found, to some extent, in asymptomatic postoperative patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278130
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic resonance imaging of cor triatriatum (1988)
    Springer
    Pediatric cardiology 9 (1988), S. 149-151 
    Details
    ISSN: 1432-1971
    Keywords: Cor triatriatum ; Magnetic resonance imaging ; Phase display
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Magnetic resonance imaging utilizing spin echo sequences was used to demonstrate cor triatriatum in an 18-year-old boy. Phase map images aided the diagnosis by demonstrating the presence of slowly flowing blood in the accessory atrial chamber. Magnetic resonance is an excellent modality for the noninvasive diagnosis of cor triatriatum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02080555
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  • 6
    Electronic Resource
    Electronic Resource
    Carotid atherosclerosis and cerebral white matter lesions in a population based magnetic resonance imaging study (2000)
    Springer
    Journal of neurology 247 (2000), S. 291-296 
    Details
    ISSN: 1432-1459
    Keywords: Key words Leukoaraiosis ; Aged ; Atherosclerosis ; Magnetic resonance imaging ; Carotid artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebral white matter lesions are frequently observed on magnetic resonance imaging of elderly, nondemented persons. There is evidence that white matter lesions are involved in the pathophysiology of cognitive decline and dementia. White matter lesions can be divided into those in the periventricular and those in the subcortical region. Pathological and epidemiological studies suggest that atherosclerosis is involved in the pathogenesis of these lesions. Our study reports on the association between atherosclerosis in the carotid arteries and white matter lesions in a population-based study among 1077 elderly subjects. We randomly sampled 1077 subjects aged between 60–90 years from two prospective population-based studies. All subjects underwent ultrasonography of the carotid artery. In addition, 1.5 T magnetic resonance imaging was performed; white matter lesions in the subcortical and periventricular regions were rated separately. With increasing number of plaques in the carotid artery the severity of periventricular white matter lesions increased (P trend = 0.03), but not the severity of subcortical white matter lesions (P trend = 0.19). In addition, an increase in intima media thickness was borderline significantly associated with an increased severity of periventricular white matter lesions (P trend = 0.09), but not of subcortical white matter lesions (P trend = 0.68). These findings suggest that partly dissimilar pathogenetic mechanisms are involved in the etiology of periventricular and subcortical white matter lesions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050586
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of hydrostatic pressure on the electrical conductivity of FEF carbon black-loaded sbr vulcanizates (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 21-32 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die elektrische Leitfähigkeit von Styrol-Butadien-Kautschuk (SBR-1502), der mit unterschiedlichen Konzentrationen von sehr schnell spritzbarem Furnace-Ruß (70, 80, 90 und 100 phr) beladen war, untersucht. Auf der Basis des Modells von Holm wurde eine qualitative Beschreibung für die elektrische Leitfähigkeit durch diese Verbundstoffe gesucht. Der Druckkoeffizient K wurde berechnet und zeigte eine starke Abhängigkeit von den Rußkonzentrationen.
    Notes: The electrical conduction was investigated in styrene butadiene rubber (SBR-1502) loaded with different concentrations of fast extrusion furnace (FEF) black (70, 80, 90, and 100 phr). On the bases of Holm's model, a qualitative description for the electrical conduction through these composites was sought. The pressure coefficient K was calculated and found to be strongly dependent on the carbon black concentrations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1987.051500103
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of solvent traces on the ultraviolet degradation of poly(vinyl chloride) (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 16 (1972), S. 83-97 
    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: The ultraviolet degradation of poly(vinyl chloride) films was studied in a photoreactor which supplied energy near 3000 Å. It was noted that the rate of degradation and color development was increased when the level of residual solvent in the cast films was increased. Two solvents were employed in the study: tetrahydrofuran and dichloroethane. The amount of residual solvent was correlated with the height of a characteristic peak at 2800 Å for tetrahydrofuran and 1900 Å for dichloroethane. Films which had very small traces of solvent showed excellent resistance to ultraviolet degradation, even in the absence of ultraviolet stabilizers. The analysis of solubility data showed that chain scission was controlling in the early stages of exposure, while crosslinking was controlling at later stages. As a result, it was not possible to apply Charlesby's treatment of radiation-induced degradation. Comparison with the results obtained by other workers for degradation at 2537 Å showed that degradation at this wavelength was much faster than degradation at 3000 Å. Furthermore, degradation at 2537 Å appeared to be controlled by crosslinking at all stages of exposure.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1972.070160108
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  • 9
    Electronic Resource
    Electronic Resource
    Copolymerization and interaction of acrylonitrile and indene (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 185-191 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The donor-acceptor interaction of acrylonitrile (AN) with indene (In) has been investigated by means of ultraviolet spectroscopy and dielectric polarization measurements. The latter method yielded a value of 0.5 for the association constant of the charge-transfer-complex (CTC) and a 4.02 D for its dipole moment. The copolymerization of the two monomers was characterized by a tendency towards alternation when conducted in the bulk. This might be due to the participation of a weak CTC in the process of copolymerization. However, this tendency disappeared in polar solvents such as DMF.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270116
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  • 10
    Electronic Resource
    Electronic Resource
    Optothermal properties of fibers. IV. Optical properties of nylon 66 fibers as a function of quenching process (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1269-1288 
    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: In this work, optical properties of samples of nylon 66 fibers were quenched in coarse-grained ice after annealing in the temperature range 80-180°C for 1-10 h. Two independent techniques were used to study optical parameters in these fibers. The first technique is the application of the diffraction technique to study the effect of quenching on the swelling factors of these fibers for some different liquids at room temperature of 25 ± 1°C. The second method dealt with the application of multiple-beam Fizeau fringes in transmission to estimate the refractive indices and birefringence of the skin and core of these fibers. The obtained results were utilized to calculate the polarizability per unit volume, isotropic refractive indices, and the Cauchy's dispersion constants. The relationship between n∥,⊥s, n∥,⊥c, n∥,⊥a, Δns, Δnc, Δna, n(iso)s, n(iso)c, and n(iso)a different annealing times and temperatures is given for these fibers. Microinterferograms and curves are also given. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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