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  • General Chemistry  (1)
  • PACS. 75.45.+j Macroscopic quantum phenomena in magnetic systems - 75.50.Xx Molecular magnets - 61.46.+w Clusters, nanoparticles, and nanocrystalline materials  (1)
  • Sleep  (1)
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Material
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  • 1
    Electronic Resource
    Electronic Resource
    Changes in the temperature rhythm of submariners following a rapidly rotating watchkeeping system for a prolonged period (1979)
    Springer
    International archives of occupational and environmental health 42 (1979), S. 185-190 
    Details
    ISSN: 1432-1246
    Keywords: Circadian rhythm ; Body-temperature ; Submariners ; Watchkeeping ; Sleep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary On-watch readings of oral temperature were obtained at hourly intervals from submariners during two continuously submerged voyages of 48 days duration. The subjects followed a rapidly rotating watchkeeping system of 4-h dutyspells during the entire period. In the majority of cases, the amplitude of the circadian temperature rhythm progressively declined, and this was accompanied by a tendency for the rhythm to disintegrate into shorter periods, associated with the length of the duty spell and the particular pattern of sleep adopted. On one voyage, one subject's rhythm showed a tendency to “free-run”, with a period of 24.6 h. It is concluded that the results give pointers to the kind of effect to be looked for in studies of shift-workers following similarly highly irregular patterns of work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377772
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic tunneling told to ignorants by two ignorants (2000)
    Springer
    The European physical journal 17 (2000), S. 69-83 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.45.+j Macroscopic quantum phenomena in magnetic systems - 75.50.Xx Molecular magnets - 61.46.+w Clusters, nanoparticles, and nanocrystalline materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Magnetic tunneling of a large spin subject to the Hamiltonian is investigated by elementary methods for weak fields H. In zero field (H=0) the tunnel frequency in the ground state is found to be equal to [0pt] multiplied by a quantity whose variation with s is slower than exponential. This result coincides with that of path integral methods [#!schi!#]. For the values of the longitudinal field which allow tunneling, the tunnel frequency is shown to vanish when H y =0 for certain “diabolic" values of [0pt] , in qualitative agreement with experiments by Wernsdorfer and Sessoli. The particular case H z =0 was already obtained by Garg by means of path integrals. The diabolic values of are in agreement with numerical results but, as already noticed by Wernsdorfer and Sessoli, they disagree with the experimental ones. This may be an effect of higher order anisotropy terms, which is briefly addressed in the conclusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070161
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  • 3
    Electronic Resource
    Electronic Resource
    Large Quadratic Hyperpolarizabilities with Donor-Acceptor Polyenes Exhibiting Optimum Bond Length Alternation: Correlation Between Structure and Hyperpolarizability (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1091-1104 
    Details
    ISSN: 0947-6539
    Keywords: chromophores ; donor-acceptor systems ; hyperpolarizability ; nonlinear optics ; polyenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Donor-acceptor polyenes of various lengths, and that combine aromatic electron-donating moieties with powerful heterocyclic electron-withdrawing terminal groups, have been synthesized and characterized as efficient nonlinear optical (NLO) chromophores. Their linear and nonlinear optical properties have been investigated, and variations in these properties have been related to ground-state polarization (dipole μ) and structure. In particular, unprecedented quadratic hyperpolarizabilities (β) have been achieved (up to β(0) = 1500 × 10-30 esu) by reduction of the bond-length alternation (BLA) in the polyenic chain. In each series of homologous compounds, increasing the number n of conjugated double bonds in the polyenic chain results in a marked bathochromic shift, more pronounced BLA, and exponential increases in μβ(0) values. As a result, polyenic chromophores displaying excellent optical quadratic nonlinearities (μβ values as large as 100 times that of the quadratic NLO benchmark 4-dimethyl-amino-4′-nitrostilbene (DANS)), as well as satisfactory solubility, have been obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030717
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