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  • 1975-1979  (16)
  • 1935-1939  (20)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 51 (1979), S. 77-82 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The occurrence of light-induced chromatophore displacements and concomitant transmittance changes in marine algae was investigated by microscope and photometrically with an automated recording microphotometer system; 16 brown, 6 green and 20 red algae were studied. In most of the brown algae, both phaeoplast displacements and transmittance changes were found. In some red algae which are frequently exposed to direct sun light during emergence at low tide, light-induced transmittance changes were measured, but they could not unequivocally be correlated with changes in the position of rhodoplasts. Among green algae, only Ulva lactuca shows chloroplast displacements which, however, follow circadian rhythms and are consequently not light-induced in the strict sense. The dose-response curves of light-induced chromatophore displacements were measured in the following Fucus and Laminaria species: F. spiralis, F. vesiculosus, F. serratus, L. digitata, L. saccharina and L. hyperborea. While in Fucus species correlations between light-induced transmittance changes and zonation of the intertidal area seem to exist, no significant differences have been found in the Laminaria species. The physiological role and ecological importance of light-induced chromatophore displacements for seaweeds living in the intertidal belt are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 284 (1977), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Helgoland marine research 32 (1979), S. 228-238 
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of light and darkness on chromatophore arrangements inFucus vesiculosus thalli exposed to air with one side (half dry) or with both sides (dry) were investigated. Low-intensity arrangement, high-intensity arrangement and dark arrangement were induced in submerged thalli. Then the thalli were exposed to air while light conditions were either kept constant or were changed. Independently of the light conditions, in all thalli exposed to air the chromatophores arranged more or less in the inner area of the cells, in epidermal cells as well as in cortical cells. Thus the chromatophore arrangements observed in submerged thalli differ in some respect from those exposed to low-tide conditions. Based on these observations the physiological and ecological role of chromatophore displacements in seaweeds is discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Helgoland marine research 31 (1978), S. 333-346 
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-induced transmission changes, measured microphotometrically in the brown algaFucus vesiculosus, are mainly the result of chromatophore displacements. Dose-response curves, as well as observations by microscope, have shown that the typical low-intensity arrangement occurs at 1 000 lux and the complete high intensity arrangement at 20 000 lux. The arrangements of the chromatophores — as well as their shapes — in dim light, strong light and darkness have been investigated. The chromatophore arrangements are different in the epidermal, cortical and medullary cells. In dim light the chromatophores are relatively large. The chromatophores of the epidermis are placed in the plasma layer of the inner cell halves. In the cortical and medullary cells the chromatophores occupy mainly the cell walls facing the light. In strong light the chromatophores are shorter and tend to become spherical. In the epidermis facing the light they move into the basal part of the cells, in the cortical and medullary cells they move to the center of the cell surrounding the nucleus. After some days of darkness the chromatophores of the epidermal cells occupy the inner periclinal and 2/3 of the anticlinal cell walls. In the cortical and medullary cells they are evenly distributed in the cytoplasmic layer at the wall. Obviously, the transmission changes measured are mainly due to chromatophore displacements in the cortical cells. Changes in shape and size play a minor role.
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  • 5
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The 70 eV electron impact mass spectra of a series of substituted 1-phenylnaphthalenes and their corresponding 1,4-dihydro-1-naphthols have been studied. Plausible fragmentation modes which account for the formation of all the major ions are proposed. An interesting hydrogen transfer reaction, leading to major fragments through the elimination of methanol, seems to proceed via an 8-membered transition state mechanism.
    Notes: Une étude par spectrométrie de masse d'une série de phényl;-1 naphtalenes substitués et des dihydro-1,4napthols-1 correspondants permet de proposer des modes de formation plausibles pour tous les ions importants. L'élimination de méthanol, qui aboutit à des ions majeurs, fait probablement intervenir le transfert d'un atome d'hydrogène par un état de transition à huit atomes.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 7 (1977), S. 188-190 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 699-710 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The processes involved in photoenolisations are theoretically simulated by an ab initio SCF-CI method, using cis-2-butenal as a prototype structure. The prominent role of the hydroxyl group conformation in the resulting transient (2a) is emphasized; its rotation ‘out of the reaction site’ allows the next reaction paths to proceed exothermally. The equilibration of the different types of twisted biradicals in the triplet manifold, which only involves a low energy barrier, is thus possible, populating in quite equal weights the precursors of both E- and Z-dienols. In the singlet state, the formation of the Z-isomer is expected to be kinetically dominant. An examination of the role of the substituents suggests that, in related systems, the steric crowding induces important structural relaxation of the dienol geometries.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 21 (1938), S. 1524-1531 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: L'huile essentielle des bourgeons du Populus trichocarpa Torr. et Gray. est constituée principalement par un mélange de salicylate de benzyle et de benzoate de benzyle.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 22 (1939), S. 640-654 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: L'odeur des essences de vétiver est principalement due à un groupe de cétones sesquiterpéniques C15H22O, bicycliques, α-éthyléniques. Ces cétones peuvent être isolées par la cristallisation fractionnée de leurs semicarbazones.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 22 (1939), S. 550-554 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: L'hydrogénation de la vanilline, en présence d'acide acétique et de charbon palladié, à la pression atmosphérique et à la température du laboratoire, donne, à côté du créosol, une forte proportion de méthyl-2-dioxy-4′,5-diméthoxy-3′,4-diphénylméthane.
    Type of Medium: Electronic Resource
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