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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Planta 171 (1987), S. 130-135 
    ISSN: 1432-2048
    Schlagwort(e): Calcium (enzyme activation) ; 1,3-β-Glucan synthase ; Glycine (glucan synthase activation) ; Plasma membrane ; Polyamine ; Polycation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Sucrose-density-gradient centrifugation and partitioning in a polyethylene glycol/dextran two-phase system were used to isolate plasmamembrane vesicles from microsomal preparations of soybean cell suspension cultures. Both methods resulted in the enrichment of the activity of a 1,3-β-glucan synthase which forms a polymer consisting of more than 99% of 1,3-linked glucose (callose). Digitonin increases the 1,3-β-glucan synthase activity in the various membrane fractions to a different degree, supporting the suggestion that this enzyme is vectorially arranged in the plasma membrane. The enzyme is greatly activated either by poly-l-ornithine or synergistically by Ca2+ and spermine, indicating that the same enzyme is affected and exhibits the regulatory properties necessary for callose synthesis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of geometry 21 (1983), S. 59-65 
    ISSN: 1420-8997
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Affine planes which admit a point transitive collineation group and at least one affine elation are considered. Such a plane is shown to be (A,ℓ∞)-transitive for some point A on ℓt8 and to be a translation plane if at least two distinct elation centers exist. If the plane has at least (order)1/2+1 distinct elation centers and the group generated by the elations is nonsolvable then the plane is either Desarguesian or Lüneburg-Tits.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1432-0630
    Schlagwort(e): PACS: 61.46+w; 71.20.Tx; 71.20.-b
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: \chem{Rb_1C_{60}} and dimerised \chem{C_{59}N} using electron energy-loss spectroscopy in transmission. From the C1s excitation spectra a reduced density of \pi^\star states is observed for polymerized \chem{Rb_1C_{60}} . This is in contrast to \chem{(\chem{C_{59}N})_2} and can be explained by the different type of \squt{doping} and by the different bonding between the fullerene molecules in the two systems. Additional information about the optical properties was obtained from the low energy loss function. Using a Kramers-Kronig analysis, the dielectric function, ( \epsilon ), and the optical conductivity, ( \sigma ), have been derived. \epsilon(0) and the onset of the spectral weight have been compared between the polymer, the dimer and \chem{C_{60}} . This onset of spectral weight is found to be at \valunit*{1.2}{\eV} and \valunit{1.4}{\eV} for o- \chem{Rb_1C_{60}} and for \chem{(\chem{C_{59}N})_2} , respectively.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1432-0630
    Schlagwort(e): PACS: 71.20Tx
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 82 using photoemission and electron energy-loss spectroscopy in transmission. In particular, the impact of the isomer symmetry of the C82 cage (Cs or C3v) on the electronic structure and on the optical properties is analysed in detail. For both isomers, combined XPS and XAS measurements of the Tm 4f and 4d states offer conclusive proof of a divalent encaged Tm ion. No significant change of the valence of the rare earth ion upon changes in the cage symmetry is observed. From the C 1s excitation spectra we find a more pronounced LUMO for the C3v(8) isomer, as is expected for the higher symmetry of the cage. Additional information about the optical properties was obtained from the low-energy loss function. With use of a Kramers–Kronig analysis, the dielectric function, ε, and the optical conductivity, σ, have been derived. ε(0) and the onset of the spectral weight are found to be 7.7 [12.8] and 0.6 eV [0.8 eV] for the Cs(6) {C3v(8)} isomer, respectively.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Bulletin of volcanology 57 (1995), S. 229-239 
    ISSN: 1432-0819
    Schlagwort(e): Lava dome ; Lava flowmechanisms ; Laboratory simulations ; Mt St Helens ; Soufrière of St Vincent ; Venus volcanism ; Pancake domes ; Planetary volcanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract To better understand the factors controlling the shapes of lava domes, laboratory simulations, measurements from active and prehistoric flows and dimensional analysis were used to explore how effusion history and cooling rate affect the final geometry of a dome. Fifty experiments were conducted in which a fixed volume of polyethylene glycol wax was injected into a tank of cold sucrose solution, either as one continuous event or as a series of shorter pulses separated by repose periods. When the wax cooling rates exceeded a critical minimum value, the dome aspect ratios (height/diameter) increased steadily with erupted volume over the course of a single experiment and the rate at which height increased with volume depended linearly on the time-averaged effusion rate. Thus the average effusion rate could be estimated from observations of how the dome shape changed with time. Our experimental results and dimensional analyses were compared with several groups of natural lava flows: the recently emplaced Mount St Helens and Soufrière domes, which had been carefully monitored while active; three sets of prehistoric rhyolite domes that varied in eruptive style and shape; and two sets of Holocene domes with similar shapes, but different compositions. Geometric measurements suggest that dome morphology can be directly correlated with effusion rate for domes of similar composition from the same locality, and that shape alone can be related to a dimensionless number comparing effusion rate and cooling rate. Extrapolation to the venusian ‘pancake domes’ suggests that they formed from relatively viscous lavas extruded either episodically or at average effusion rates low enough to allow solidified surface crust to exert a dominating influence on the final morphology.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1432-0630
    Schlagwort(e): PACS: 81.05.Tp; 81.10.Jt
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract. The abundance of carbon single-wall nanotubes (SWNTs) in soot synthesized by pulsed laser evaporation of graphite is studied over a wide range of synthesis conditions. The derived SWNT growth time-scale appears to be much longer than any characteristic time-scale in a simplified model of the relaxation of a high-pressure hot condensing gas bubble in a background atmosphere. It is concluded that SWNT nucleation and growth take place in relaxed, condensed, thermalized evaporation products at an optimal temperature between 850–1250 °C at a rate of few μm length per second, which is consistent with a condensed state “precipitation” mechanism for the SWNT formation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 1432-2048
    Schlagwort(e): Callose ; Cell culture (1,3-β-glucan synthase) ; Digitonin-1,3-β-Glucan synthase (purification, immunology) ; Glycine (1,3-β-glucan synthase)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The plasma-membrane-localized 1,3-β-glucan synthase (EC 2.4.1.34) from suspension cultures of Glycine max (L.) Merr. was greatly enriched by a three-step purification procedure. Starting with a microsomal preparation, a six- to eightfold enrichment of the enzyme was achieved by isolating plasma-membrane vesicles in a polyethyleneglycol/dextran two-phase system. The enzyme was solubilized with the nonionic detergent digitonin and further purified 12-fold by successive centrifugations on two linear sucrose density gradients. The most purified enzyme preparation showed enrichment in a 31-kilodalton (kDa) polypeptide and was used to raise polyspecific antibodies which precipitated 1,3-β-glucan synthase activity. These antibodies were purified by affinity chromatography against immobilized membrane protein fractions of lower molecular weight which were devoid of 1,3-β-glucan synthase activity. The purified antibodies specifically labelled a single polypeptide of 31 kDa in the 1,3-β-glucan-synthase-containing heavy fractions of the first sucrose gradient indicating that this polypeptide represents part of the active enzyme complex.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Polymer bulletin 7 (1982), S. 159-163 
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary Experimentally observed deviations from the classical rate laws of radical polymerization in solution can be treated as solvent interactions concerning the growth step. The theory of hot radicals and the theory of donor-acceptor complexes are based on these considerations. It had been shown that the experimental data rather fit the former theory. However by a modification of the latter theory with respect to termination reactions of the different radicals a remarkable equivalence between these different views is exposed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of fusion energy 1 (1981), S. 69-86 
    ISSN: 1572-9591
    Schlagwort(e): Neutral beam injector ; fusion ; 3He ; direct energy conversion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract We describe a design for a 120-keV, 2.3-MW,3He neutral beam injector for use on a D-3He fusion reactor. The constraint that limits operating life when injecting He is its high sputtering rate. The sputtering is partly controlled by using an extra grid to prevent ion flow from the neutralizer duct to the electron suppressor grid, but a tradeoff between beam current and operating life is still required. Hollow grid wires functioning as mercury heat pipes cool the grid and enable steady state operation. Voltage holding and radiation effects on the acceleration grid structure are discussed. We also briefly describe the vacuum system and analyze use of a direct energy converter to recapture energy from unneutralized ions exiting the neutralizer. Of crucial importance to the technical feasibility of the3He-burning reactor are the injector efficiency and cost; these are 53% and $5.5 million, respectively, when power supplies are included.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 1434-6036
    Schlagwort(e): PACS. 71.20.Tx Fullerenes and related materials; intercalation compounds - 79.60.Fr Polymers; organic compounds - 78.90.+t Other topics in optical properties, condensed matter spectroscopy and other interactions of particles and radiation with condensed matter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: We report the results of a detailed study of the occupied and unoccupied electronic structure of dimers of the new heterofullerene by means of photoemission and electron energy-loss spectroscopy. A close similarity is found between the electronic structures of pristine and with an additional broadening of the spectra in the former due to the distortion of the fullerene cage caused both by dimerization and the chemical substitution. Both the occupied and unoccupied electronic states, as well as the interband transitions between them, attest to the high degree of molecular character retained in the solid state. Comparison of the shake-up structures in the and X-ray photoemission spectra confirm that the highest lying occupied states in the heterofullerene have a strong degree of N character, whereas the lowest lying unoccupied states have mainly C character. We also present the optical conductivity of the heterofullerene (derived from the loss function), which shows an optical gap of 1.4 eV, some 0.4 eV smaller than that of .
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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