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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 280 (1988), S. 246-251 
    ISSN: 1432-069X
    Keywords: Retinoids ; Sebum ; Arotinoid ; Hypervitaminosis A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Retinoids are known to modulate sebaceous gland activity in humans and animals. The nonpolar arotinoid Ro 15-0778 [(E)-1,2,3,4-tetrahydro-1,1,4,4-tetramethyl-6-(1-methyl-2-phenylethenyl) naphthalene] does not contain a polar end group and is devoid of the classical retinoid side effects of hypervitaminosis A. The favorable toxicological profile stimulated the evaluation of this arotinoid in animal models of sebum production. In castrated, testosterone-stimulated male rats, Ro 15-0778 is 50 times more potent than 13-cis-retinoic acid in inhibiting the production and subsequent secretion of sebum. The oral ED50 value of Ro 15-0778 is 30μg/kg, while an oral dose of 0.5 mg/kg inhibited sebum secretion nearly 1005. In testosterone-stimulated female rats, Ro 15-0778 inhibits sebum secretion significantly with an oral ED50 of 140 μg/kg and an s.c. ED50 of 75μg/kg. Ro 15-0778 was also evaluated for its ability to prevent testosterone induction of the immature hamster flank organ. The topical ED50 is 0.53 mg/kg and the oral ED50 is 38 mg/kg. This arotinoid is similarly active in mature male hamsters without testosterone treatment. In addition, the retinoid is active topically and orally in reducing the size of the gerbil abdominal sebaceous gland. The compound exhibits no antiandrogenic activity when tested in ventral prostrate and seminal vesicle assays in rats. Additionally, the compound does not have estrogenic activity when tested in the rat uterine weight assay. High doses of Ro 15-0778 in humans did not demonstrate significant sebumsuppressing activity. This study indicates that extra-polation of retinoid data from rodent animal models to activity in human sebaceous glands can not be made with a high degree of certainty. There is a need to develop new, more predictive models for retinoid activity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 467-472 
    ISSN: 1573-7357
    Keywords: 75.25.+z ; 75.10.Jm ; 75.40.Gb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Inelastic neutron scattering measurements have been performed on the S=1/2 quasi-one-dimensional system Sr14Cu24O41, which has both simple chains and two-leg ladders of copper ions. We have observed that both the chain and the ladder exhibit a spin gap, which originate from a dimerized state.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 93 (1994), S. 277-297 
    ISSN: 1434-6036
    Keywords: 75.30.K ; 68.65 ; 25.40.F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stage-2 CoCl2-GIC approximates a two-dimensional easy-plane (XY) ferromagnet on a triangular lattice. It has been found in prior work to order in two steps, with the intermediate phase showing long-ranged ferromagnetic correlations within the intercalate plane, but no correlations between neighboring planes. We have probed the wave vector and temperature dependence of the static and dynamic spin correlations in detail, including measurements of the critical scattering, the quasielastic scattering from vortex diffusion and the spin wave excitations with and without an external magnetic field. Some of the predictions for a Kosterlitz-Thouless type transition are met in this compound, at least qualitatively, including an apparent jump in the spin stiffness at the critical point and the existence of a diffusive central peak in the scattering function possibly originating from vortex autocorrelations. However, there are some inconsistencies between our observations and recent analytical studies as well as Monte Carlo-molecular dynamics simulations of the vortex dynamics that prevent unambigous assignment of the upper critical temperature as a vortex-binding transition.
    Type of Medium: Electronic Resource
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