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  • Articles: DFG German National Licenses  (11)
  • 1990-1994  (11)
  • 1980-1984
  • 1991  (11)
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  • Articles: DFG German National Licenses  (11)
Material
Years
  • 1990-1994  (11)
  • 1980-1984
Year
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the transmission Mossbauer spectra of Fe/Ag(100) single crystal multilayers with large thicknesses (∼100 ML) of intervening Ag as a function of both temperature and magnetic field applied perpendicular to the surface. In contrast to earlier work on samples with less silver between layers, ordering temperatures are much reduced and the initial relaxation effects observed on cooling down appear to set in with a very small or zero order parameter.1,2 Measurements with a magnetic field applied perpendicular to the film surface showed a single well defined order parameter, which rules out superparamagnetizatism as the source of the observed relaxation effects. As an example, a sample measured earlier with 2.4 ML of Fe and 4 ML of Ag exhibited a well defined order parameter in zero field with a transition temperature near 200 K. In the present case a 3.0 ML Fe sample with ∼100 ML of intervening Ag exhibited relaxation effects setting in near 100 K, with a nonzero order parameter below ∼60–70 K. Measurements in a magnetic field showed clear evidence for long range spin–spin correlations even at temperatures above 100 K. Our interpretation is that for the films with relatively thin (∼4 ML) Ag layers between the Fe, there is sufficient coupling between layers to drive an essentially 3-d magnetic transition. With a very thick Ag interlayer separation, the characteristics of the film become much more like an ideal 2-d Heisenberg model, which builds up very long range spin–spin correlations at low temperatures, but whose actual magnetic ordering transition is depressed to T=0 (finite T with anisotropy).3 Presumably the transition which we estimate to be at 60–70 K is driven by the fact that the perpendicular anisotropy is not zero, but in fact is larger than the demagnetizing field.〈ks〉
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1575-1579 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the effect on the superconducting and microstructural properties of YBa2Cu3O7−x screen printed thick films as a function of silver content (in the form of Ag and Ag2O) from 0 to 40 wt. % by employing different experimental techniques has been carried out. It has been found that silver improves the sinterability and intergrain connectivity and reduces the normal state resistivity. The superconducting transition temperature of the above films was found to be in the range of 82 to 91 K. Our results show that a small addition of silver (Ag or Ag2O) helps in enhancing the superconducting properties. However, large amounts lead to formation of 211 phase as the decomposed product and thereby deteriorate the quality of the superconductor. Silver has been found to remain as metal in the samples for the entire range. Further, in light of our results, it seems that an addition of Ag metal is more beneficial than the addition of Ag2O.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3646-3648 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improvement in zero resistance temperature (T0c) of the 2223 phase in the Bi-Sr-Ca-Cu-O system by using a nominal composition Bi0.8Pb0.2SrCa2Cu2Ox has been achieved. The bulk Bi0.8Pb0.2SrCaCu2Ox samples synthesized from a matrix reaction method exhibited a superconducting transition with T0c of 110 K. Addition of one Ca-atom per molecule of the above composition, that is, Bi0.8Pb0.2SrCa2Cu2Ox resulted in enhanced T0c of 122 K with onset temperature (Tonsetc) of 140 K. Interestingly, T0c of 122 K was also observed in the Pb-free BiSrCa2Cu2Ox samples, but it decreases to 115.5 K after 3–4 thermal cycles. However, no such decrease in T0c was observed in the Pb-doped samples, indicating the formation of stable 2223 phase. On the basis of x-ray diffraction, energy dispersive spectra and scanning electron microscopy data, it is concluded that excess of Ca facilitate the nucleation of 2223 phase.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0942-0940
    Keywords: Head trauma ; contre-coup injury ; CT ; prognosis ; traumatic cerebral haemorrhage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The clinical and radiological prÒfiles of 63 patients with contrecoup haematomas were studied. The overall mortality was 53%. The mortality in patients with contre-coup haematomas alone was only half of that found in patients with associated coup injury (80%).
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Human genetics 〈Berlin〉 87 (1991), S. 513-515 
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Human genetics 〈Berlin〉 87 (1991), S. 665-670 
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The frequencies of chromosome aberrations and sister chromatid exchanges (SCEs), cell proliferation kinetics and mitotic indices were studied in peripheral blood lymphocyte cultures of leprosy patients both before and after chemotherapy. The differences in the frequencies of chromosome aberrations and SCEs between controls, paucibacillary and multibacillary patients were found to be statistically highly significant (P 〈 0.001). The extent of cytogenetic damage seemed to depend on the severity of the disease. Lymphocytes of untreated leprosy patients showed a low mitotic index and a slow rate of cell proliferation. Following combined treatment with dapsone and rifampicin there was an increase, but to a lesser degree (P 〈 0.01), in the frequency of SCEs and chromosome aberrations while the drug combination of dapsone, rifampicin and clofazamine had a non-mutagenic effect on chromosomes of the patient. Furthermore, after drug treatment, the cell proliferation rate and mitotic indices in paucibacillary patients were comparable to that of controls. These results indicate the clastogenic potency of Mycobacterium leprae and the remedial effects that follow therapeutic drug treatment.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 26 (1991), S. 6606-6612 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The scanning electron microscope and the energy dispersive X-ray based analytical techniques have been used to study the sulphuric acid corrosion resistance of standard “E” fibre glass and PPG developed and patented 1201 [1], an “ECR” acid-resistant fibre glass. While it is well agreed by the experts in the field that direct exposure of fibre glass to 0.5 m sulphuric acid is much too severe a condition to simulate service conditions of most filament wound fibre glass products, nevertheless, the above corrosive environment was used to demonstrate a significant superiority of PPG 1201 glass in acid resistance over the standard “E” glass regardless of the source of its origin. It is also demonstrated that not only boron oxide leached out during acid exposure but a significant amout of calcium, aluminium, and magnesium oxides also were depleted from the “E” glass composition during acid treatment. It is also demonstrated that heat treatment of “E” glass products reduced the rate of acid attack. It did not, however, eliminate it completely. Heat treatment affects the strength properties of this fibre glass adversely.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 26 (1991), S. 6606-6612 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The scanning electron microscope and the energy dispersive X-ray based analytical techniques have been used to study the sulphuric acid corrosion resistance of standard “E” fibre glass and PPG developed and patented 1201 [1], an “ECR” acid-resistant fibre glass. While it is well agreed by the experts in the field that direct exposure of fibre glass to 0.5 m sulphuric acid is much too severe a condition to simulate service conditions of most filament wound fibre glass products, nevertheless, the above corrosive environment was used to demonstrate a significant superiority of PPG 1201 glass in acid resistance over the standard “E” glass regardless of the source of its origin. It is also demonstrated that not only boron oxide leached out during acid exposure but a significant amout of calcium, aluminium, and magnesium oxides also were depleted from the “E” glass composition during acid treatment. It is also demonstrated that heat treatment of “E” glass products reduced the rate of acid attack. It did not, however, eliminate it completely. Heat treatment affects the strength properties of this fibre glass adversely.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 10 (1991), S. 1299-1300 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1885-1890 
    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: Infrared spectra of raw and chemically treated pineapple leaf fibers (PALF) have been studied using the KBr disk technique. Bands due to lignin and hemicellulose in the spectra of the fibers and their changes due to chemical (NaOH and NaCIO2) treatment have been discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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