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  • 1990-1994  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Preparation and crystal structure of C60S16 (1993)
    Springer
    Applied physics 56 (1993), S. 169-174 
    Details
    ISSN: 1432-0630
    Keywords: 61.50 ; 61.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new fullerene-containing van der Waals-compound, C60S16, has been synthesized and its crystal structure determined from single-crystal X-ray diffraction data collected at room temperature. The compound is monoclinic, space group C 2/c with a=20.867(4) Å, b=21.062(4) Å, c=10.508(2) Å, β=111.25(7)° and four formula units per cell. The C60 molecules form a three-dimensional framework with one-dimensional channels along c which contain crown-shaped S8 rings. The structure has been determined by direct methods and has been refined to atomic resolution on the C60 molecule. The two independent C-C bond distances, averaged under the idealized point symmetry of the “free” C60 molecule, amount to 1.340(8) Å and 1.448(8) Å, corresponding to a “bond alternation” as large as 0.108(8) Å. The bond lengths are compared with the results of theoretical calculations of the molecular structure of C60 as well as with bond lengths from various experimental sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00539470
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  • 2
    Electronic Resource
    Electronic Resource
    Dietary Restriction in Nonhuman Primates: Progress Report on the NIA Study (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 673 (1992), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1992.tb27434.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Microcirculatory dynamics in experimental human gingivitis (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of clinical periodontology 20 (1993), S. 0 
    Details
    ISSN: 1600-051X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract The purpose of this study was to determine the changes that occur in the gingival microcirculation during the development of experimental gingivitis in humans. There have been no studies published to date combining videomicroscopy and laser Doppler flowmetry to study vascular dynamics in experimental gingivitis. Alterations occurring in the microcirculation of the marginal gingiva in 10 (18–30-year-old), healthy male humans when they suspended oral hygiene procedures in a proscribed area for 12–16 days were monitored. A partial mouth, experimental gingivitis model was employed. Gingival health was evaluated before and after the experimental period by assessing gingival and plaque indices and gingival crevicular fluid volume. Gingival vascular monitoring included measurement of red blood cell velocity in individual gingival microvessels via video-microscopy and measurement of regional gingival blood flow using laser doppler flowmetry. The number of vessels visible in a given microscopic field in a given subject and the number of vessels exhibiting flow were also determined from the videotapes. Systemic cardiovascular and respiratory parameters were monitored to ensure that gingival vascular changes were not secondary to systemic changes. Gingivitis developed in all subjects; significant increases (Student t-test, P 〈 0.05) were seen in plaque index, gingival index, bleeding on probing and crevicular fluid volume. No change in superficial capillary blood velocity and a significant decrease in gingival regional blood flow were seen with gingivitis. A significant increase in the number of vessels visible in microscopic fields and a decrease in the % of vessels exhibiting flow were observed. Gingival microcirculation exhibited a dramatic, dynamic change in response to the development and progression of gingivitis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-051X.1993.tb00774.x
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  • 4
    Electronic Resource
    Electronic Resource
    Aging and microcirculatory dynamics in human gingiva (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of clinical periodontology 20 (1993), S. 0 
    Details
    ISSN: 1600-051X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract There have been no published reports characterizing gingival vascular function in humans of different ages. In this study, we compared gingival vascular dynamics in 60 healthy male humans ranging in age from 18–75 years (young, 18–25 years (Y); middle, 35–45 years (M); old, 65–75 years (O), 20 subjects/group). Both videomicroscopy of individual microvessels and laser doppler flowmetry were employed to assess marginal gingival circulation. Systemic cardio-pulmonary parameters were monitored as controls. The number of gingival vessels visible in a microscopic field was higher and the number of microvessels exhibiting active flow was lower in M and O compared to Y. There were no differences among age groups in laser doppler flow values (tissue blood flow) or in red blood cell velocity in individual vessels. Although not statistically significant with age there was a trend towards decreasing blood flow velocity in both the laser doppler and videomicroscopic measurements. Blood pressure increased slightly with age. Peripheral oxygen saturation was lower in O compared to Y and M. No differences were seen in heart rate, respiratory rate or end-tidal carbon dioxide concentration. The changes in blood pressure and oxygen saturation were expected. The differences in numbers of visible vessels and the number of vessels with active blood flow may reflect the way the gingival microcirculation adapts with age to changing nutritional needs or to microbial and/or mechanical challenge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-051X.1993.tb00393.x
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  • 5
    Electronic Resource
    Electronic Resource
    Changes in G Protein-mediated Signal Transduction in Aging and Alzheimer's Disease (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 695 (1993), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: Previous reports have shown that there are age-related reductions in muscarinic receptor (mAChR) sensitivity to agonist stimulation. Our research has elucidated the mechanisms involved in this loss. These studies have shown that this decline is the result of decreases in mAChR concentration, reductions in the number of neuronal cells, and altered phosphoinositide (PI)-mediated signal transduction (ST). The decrements in PI-mediated ST are observed as a reduced ability of muscarinic (m) agonists to enhance K+-evoked release of DA (K+ERDA) from striatal slices from old rats. Additional experiments indicated that the locus of the ST deficits appears to be at the mAChR-G protein interface, since attempts to bypass this interface reduced m-enhanced K+ERDA deficits in the striata from old rats. Moreover, it appears that the ability of mAChR to decouple from their respective G proteins is reduced as a function of age, since carbachol-stimulated low KM GTPase activity was found to be reduced in hippocampal and striatal tissue obtained from old rats. Similar findings were observed in this parameter in AD hippocampus and basal ganglia. Further reductions were seen in carbachol-stimulated low KM GTPase as a function of the duration of the disease. Results are discussed in terms of structural membrane alterations in aging and disease that may lead to reductions in the efficacy of receptor-G protein coupling/uncoupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1993.tb23024.x
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  • 6
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1993)
    Springer
    Naturwissenschaften 80 (1993), S. 141-143 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01131021
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  • 7
    Electronic Resource
    Electronic Resource
    Neutron scattering study of intermolecular excitations in solid C60 and C70 (1993)
    Springer
    The European physical journal 90 (1993), S. 325-329 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spectrum of intermolecular excitations in solid C60 and C70 is investigated by neutron time-of-flight spectroscopy. The quasielastic scattering above the ordering transition is studied in detail and compared to a rotational diffusion model. Below the transition the scattering spectra have essentially a three peak structure with a prominent libronic excitation near ±2 meV for both fullerenes. A detailed analysis gives evidence for a broader distribution of librational modes with an additional pronounced maximum near 5 meV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01433056
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  • 8
    Electronic Resource
    Electronic Resource
    Phase transition at 240 K in C70 single crystal (1993)
    Springer
    Applied physics 56 (1993), S. 227-229 
    Details
    ISSN: 1432-0630
    Keywords: 31.70.Ks ; 64.70.Pf ; 65.70.+y
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The thermal expansion of single- and polycrystalline C70 is studied between 5 and 315K using an ultrahigh-resolution capacitance dilatometer. We observe a first-order phase transition in single crystalline C70 at ≈240K and a transition at ≈280K in polycrystalline C70. X-ray diffraction measurements at 300K show that the C70 single crystal has fcc symmetry, whereas the polycrystalline sample is multiphase (fcc and hcp). The results are compared to thermal expansion measurements of solid C60.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00539479
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