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  • 1
    Electronic Resource
    Electronic Resource
    Ozone uptake in the sun and shade crown of spruce: quantifying the physiological effects of ozone exposure (1993)
    Springer
    Trees 7 (1993), S. 227-232 
    Details
    ISSN: 1432-2285
    Keywords: Ozone uptake ; Stomatal conductance ; Spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The uptake of air pollutants depends both on pollutant concentration and on stomatal conductance. This paper deals with the uptake of ozone (O3) from the air into the needles of Norway spruce [Picea abies (L.) Karst.] under ambient climatic conditions. Regulation of O3 uptake by the stomata is shown and also the difference between the “physiologically active O3 concentration” and the O3 concentration of the ambient air. Data from the sun and shade crown of spruce trees at 1000 m a.s.l. are presented. Analysis of data from three vegetation periods has shown that at low ambient O3 concentrations the O3 uptake is largely regulated by stomatal conductance. Water vapour pressure deficit (VPD) of the atmosphere is the climatic factor which showed the highest positive correlation with O3 concentration. However, a high leaf-air VDP led to stomatal closure, thus reducing the O3 uptake in the needles despite high O3 concentrations in the ambient air. The potential O3 stress caused by high O3 concentrations can be strongly mitigated by this natural closing of the stomata and the simultaneous occurrence of moderate drought stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202078
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology and distribution of Müller cells in the retina of the toad Bufo marinus (1993)
    Springer
    Cell & tissue research 272 (1993), S. 183-192 
    Details
    ISSN: 1432-0878
    Keywords: Retina ; Müller cells ; Neuron-specific enolase ; Immunocytochemistry ; Quantitative analysis ; Ultrastructure ; Bufo marinus (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have previously shown that an antibody against neuron-specific enolase (NSE) selectively labels Müller cells (MCs) in the anuran retina (Wilhelm et al. 1992). In the present study the light- and electron-microscopic morphology of MCs and their distribution were described in the retina of the toad, Bufo marinus, using the above antibody. The somata of MCs were located in the proximal part of the inner nuclear layer and were interconnected with each other by their processes. The MCs were uniformly distributed across the retina with an average density of 1500 cells/mm2. Processes of MCs encircled the somata of photoreceptor cells isolating them from each other by glial sheath, except for those of the double cones. Some of the photoreceptor pedicles remained free of glial sheath. Electron-microscopic observations confirmed that MC processes provide an extensive scaffolding across the neural retina. At the outer border of the ganglion cell layer these processes formed a non-continuous sheath. The MC processes traversed through the ganglion cell layer and spread beneath it between the neuronal somata and the underlying optic axons. These processes formed a continuous inner limiting membrane separating the optic fibre layer from the vitreous tissue. Neither astrocytic nor oligodendrocytic elements were found in the optic fibre layer. The significance of the uniform MC distribution and the functional implications of the observed pattern of MC scaffolding are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323585
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  • 3
    Electronic Resource
    Electronic Resource
    The orientation distribution in an industrial sample of poly(p-phenylenetere-phthalamide) determined by two- and three-dimensional NMR techniques (1993)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 44 (1993), S. 279-284 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two new solid-state NMR methods for measuring orientation distributions in partially ordered solids are applied to high tensile-strength fibre polymers. Both methods use the anisotropy of the carbon-13 chemical shift tensor as a probe for local molecular directions, but they differ in the manner in which the information is extracted and complement one other. The spectral resolution is higher in the ORDER (ORientation Distributions with Enhanced Resolution) experiment, which employs rotor-synchronized three-dimensional magic angle spinning (MAS) NMR, while the angular precision with which the orientation distribution can be determined is higher in the DECODER (Direction Exchange with Correlation of Orientation Distribution Evaluation and Reconstruction) experiment. The utility of the two techniques is demonstrated by their application to the study of industrially produced poly(p-phenyleneterephthalamide) fibres. Both give the same result for the width (χ = 13°) and the order parameters (〈P2〉=0.85, 〈P4〉=0.57, 〈P6〉=0.34, 〈P8〉=0.14) of the orientation distribution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1993.010440604
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of chemical-shift tensor orientations in methylene groups by separated-local-field NMR (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 352-356 
    Details
    ISSN: 0749-1581
    Keywords: Separated-local-field NMR ; Chemical-shift tensor orientations ; Poly(ethylene oxide) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C chemical-shift tensor orientations in the OCH2CH2O moieties of poly(ethylene oxide) (PEO) and poly(ethylene terephthalate) (PET) were determined by means of 1H—13C separated-local-field NMR spectroscopy, and the literature values for the shift tensors in polyethylene (PE) and polyoxymethylene (POM) were improved. An angular resolution of ± 4° was attained on standard equipment with 90° pulse lengths exceeding 4 μs. Relatively high uniformity of the methylene tensor orientations, complying with local molecular symmetry, was found.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310408
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    Paper (German National Licenses)
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