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  • 1
    Electronic Resource
    Electronic Resource
    Seismological models for mining-induced seismic events (1989)
    Springer
    Pure and applied geophysics 129 (1989), S. 513-521 
    Details
    ISSN: 1420-9136
    Keywords: Mine-induced seismicity ; source models ; barrier/asperity models ; seismic moment ; rockbursts ; damaged area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract One possibility to estimate and to interpret the source parameters of low-stress drop seismic events to use the barrier or the asperity model. These models serve as the description of seismic events in a in which a horizontal room and pillar mining method is used in great depth. An additional macroseismic parameter, the destroyed or damaged area in the mine, allows the estimation of the real static stress drop of mining-induced seismic events. This stress drop, derived from a simplified barrier-or asperity-model, appears to be a constant and a characteristic parameter for a given source region. On this base, a relation between the underground destruction or damages and the seismologically estimated parameters is derived and is used for the classification of the mining-induced seismic events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874522
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  • 2
    Electronic Resource
    Electronic Resource
    Flight hardware for chemical fixation of living material in the microgravity environment (1986)
    Springer
    Naturwissenschaften 73 (1986), S. 435-437 
    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/BF00367290
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  • 3
    Electronic Resource
    Electronic Resource
    Development and gravity sensing of cress roots under microgravity (1986)
    Springer
    Naturwissenschaften 73 (1986), S. 438-441 
    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/BF00367291
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  • 4
    Electronic Resource
    Electronic Resource
    Membrane-potential responses following gravistimulation in roots of Lepidium sativum L. (1985)
    Springer
    Planta 163 (1985), S. 463-472 
    Details
    ISSN: 1432-2048
    Keywords: Electrical current (graviperception) ; Gravielectrical response ; Graviperception ; Intracellular potential ; Lepidium ; Root tip (graviperception) ; Statocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Membrane potentials were measured in lateral statocytes of vertically and nonvertically growing roots of Lepidium sativum L. using conventional glass-microelectrode techniques. Statocytes in vertically growing roots showed a stable resting potential of-118±5.9 mV without spontaneous fluctuations. Upon tilting the root 45° from the vertical, an electrical asymmetry was observed. Statocytes on the physically lower side of the root depolarized by approx. 25 mV. This depolarization occurred following a latent period of 8 s reaching a minimum (approx.-93 mV) after 170 s. This depolarization is the earliest event in graviperception ever recorded. After this depolarization, the cell repolarized within 60 s to a potential approx. 10 mV more positive than the original resting potential. Statocytes on the upper flank showed a slow hyperpolarization (t 1/2h=half time for hyperpolarization=168 s) reaching a final, stable potential at a level 10 mV more negative. These effects of gravistimulation were statenchyma-specific, since cells in the cortex and rhizodermis showed no similar effects. The gravi-electrical responses were observed in 25% of all roots tested. Roots which showed no gravi-electrical response had a reduced elongation growth, lacked gravity-induced bending and lacked the typical structural polarity in punctured statocytes. This observed transition from a symmetrical pattern of resting potential in the statenchyma to an asymmetrical pattern following gravistimulation supports the results observed with external current measurements (Behrens et al., Plant Physiol. 70, 1079–1083, 1982) and extends these results to the cellular level and to considerably improved temporal resolution. The asymmetry in the gravi-electrical response extends the graviperception model of Sievers and Volkmann (Planta 102, 160–172, 1972) which comprises an asymmetrical sedimentation of the amyloplasts on the distal endoplasmic reticulum of statocytes. This generates an intraorgan signal which then must be transmitted to the growth zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392703
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  • 5
    Electronic Resource
    Electronic Resource
    Electrical properties of the vertically growing root tip of Lepidium sativum L. (1985)
    Springer
    Planta 163 (1985), S. 453-462 
    Details
    ISSN: 1432-2048
    Keywords: Electrical anisotropy ; Electrotonic coupling ; Lepidium ; Root tip ; Resting potential ; Tissue resistivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Electrical transmembrane potential differences and resistances in different tissues of intact root tips of Lepidium sativum L. were investigated in a humid atmosphere by conventional glass-microelectrode techniques with the reference electrode at the surface (apoplast) of the root. The resting potential (inside negative) in cells of the root cap rose from-80 mV in external cell layers (secretion cells) to approx.-140 mV in central cells (statocytes). Measurements of the electric input resistance within the apoplast of the root tip (calyptra, meristem and elongation zone) yielded a preference for longitudinal contact (resistance per length of tissue approx. 3.4 GOhm m-1) compared with transversal contact (approx. 14 GOhm m-1). Similarly, the symplastic coupling expressed as the characteristic length (L) where a signal is reduced to 1/c compared with the origin yielded L y =390 μm in the longitudinal (y) direction and L x =140 μm in the transversal (x) direction. Cable analytical treatment of the symplastic input resistances (approx. 10 MOhm) resulted in low membrane resistances in the y-direction at the ends of cells compared with the membrane resistances in the x-direction (approx. 0.2 Ohm m2) of the lateral membranes in the approximately cylindrical cells. This anisotropy is discussed in terms of model calculations. The resistivity of the symplast was calculated to be about 2.5 Ohm m. The input current-voltage relationship displayed a slight curvature with increasing slope for the more negative membrane potential typical of membranes with electrogenic pumps. Even after massive electrical stimulation in the range from-50 to-150mV carried out to trace current-voltage curves, electrical excitations (action potentials) were not detected in the cells investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392702
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  • 6
    Electronic Resource
    Electronic Resource
    Struktur und Morphologie von Polyethylen-Füllstoff-Compositen. I. Untersuchungen zur Morphologie von Polyethylen-Füllstoff-Compositen mit Hilfe der Rasterelektronenmikroskopie (1988)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 39 (1988), S. 282-285 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The morphology of high density polyethylene filled with chalk, suprasil and sodium chloride powder, respectively, has been investigated by scanning electron microscopy of the polished and etched surfaces. All composites show a different morphology of the polyethylene in the interfacial region. This effect is due to the different structure determining activities of the used fillers.
    Notes: Die Morphologie von Compositen aus Polyethylen hoher Dichte mit Kreide, Suprasil und Steinsalzpulver wurde mit Hilfe der Rasterelektronenmikroskopie an geätzten Schliffen untersucht. Bei allen drei Compositen wird eine unterschiedliche Morphologie des Polyethylens in der Grenzschicht zu den Füllstoffpartikeln gefunden. Dieser Effekt wird mit einer unterschiedlichen Strukturaktivität der eingesetzten Füllstoffe erklärt.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1988.010390603
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  • 7
    Electronic Resource
    Electronic Resource
    Untersuchungen zur Bildung transkristalliner Strukturen an Polyethylengrenzflächen. Teil I. Polarisationsmikroskopische Untersuchungen (1989)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 40 (1989), S. 504-508 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Recrystallization of polyethylene frequently results in characteristic supermolecular structures on surfaces or at interfaces to mineral powders, the so-called transcrystalline layers. Results of examination by polarization microscopy show that these structures are combined with thermooxidative degradation in layers about 100 μm thick in the vicinity of the surfaces of polyethylene.
    Notes: Bei der Rekristallisation von Polyethylen entstehen an der Oberfläche oder an Grenzflächen zu pulverförmig aufgebrachten mineralischen Beschichtungsstoffen häufig charakteristische übermolekulare Strukturen, die transkristallinen Schichten. Die Ergebnisse polarisationsmikroskopischer Untersuchungen weisen darauf hin, daß diese Strukturen mit dem thermooxidativen Abbau in den oberflächennahen etwa 100 μm dicken Schichten des Polyethylens verknüpft sind.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1989.010400804
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  • 8
    Electronic Resource
    Electronic Resource
    Untersuchungen zur Bildung transkristalliner Strukturen an Polyethylengrenzflächen. Teil II. Molmassenbestimmung, gravimetrische, DSC- und RöntgenkleinwinkelmessungenTeil I: siehe [1] (1989)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 40 (1989), S. 555-558 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: By small-angle X-ray scattering, differential scanning calorimetry, gravimetry, and determination of molecular mass it is confirmed that transcrystalline layers, which frequently arise at free polyethylene surfaces or at interfaces to mineral powders, are the consequence of thermooxidative degradation of the polymer. A comparison of the structures at interfaces between two different types of polyethylene in absence of oxygen shows the same mechanism of formation.
    Notes: Durch Röntgenkleinwinkelstreuung, Differential-Scanning-Calorimetrie, Gravimetrie und Molmassenbestimmung wird bestätigt, daß die an freien Polyethylenoberflächen oder an Grenzflächen zu pulverförmig aufgebrachten mineralischen Beschichtungsstoffen häufig entstehenden transkristallinen Schichten durch thermooxidativen Abbau des Polyethylens bedingt sind. Ein Vergleich mit den zwischen zwei unterschiedlichen Polyethylenen ohne Einfluß des Luftsauerstoffs entstehenden Strukturen zeigt, daß der Bildungsmechanismus der gleiche ist.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1989.010400901
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