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  • Artikel  (3)
  • 79.60.-i  (1)
  • Phenothiazines  (1)
  • degradation  (1)
  • Springer  (3)
  • American Geophysical Union (AGU)
  • American Institute of Physics (AIP)
  • Geological Society of America (GSA)
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  • Artikel  (3)
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  • Springer  (3)
  • American Geophysical Union (AGU)
  • American Institute of Physics (AIP)
  • Geological Society of America (GSA)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 276 (1998), S. 388-394 
    ISSN: 1435-1536
    Schlagwort(e): Key words Hyaluronic acid ; degradation ; molecular weight ; metal surface ; hydroxyl radical
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  When the viscosity of hyaluronic acid (HA) solution was measured with a rotational visco-meter, depolymerization occurred only by leaving the sample in the cup of the viscometer, while the solution in a glass test tube at the same temperature, 37 °C, was practically stable during the entire period of investigation. As the parts where the sample solution had contact with the viscometer are stainless steel, the participation of metal ions in the depolymerization was suspected. Therefore, experiments were carried out with stainless-steel beads in the HA solution. The results show that the molecular weight of HA decreased on exposure to the beads under aerobic conditions. The addition of 10 beads to 2 ml of a 0.1% HA solution prepared with 0.2 M NaCl reduced the molecular weight to about 75% of the initial value after 4 h. The degradation rate was proportional to the surface area of the beads. However, no dissolution of metal ion was detected, and therefore, this reaction was thought to proceed at the surface of the metal.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 97 (1995), S. 439-452 
    ISSN: 1434-6036
    Schlagwort(e): 61.44.+p ; 71.20.Cf ; 72.15.-v ; 79.60.-i
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Measurements with photoemission spectroscopy in the photon-energy range 35–130 eV have been used to determine the valence band of the stable icosahedral Al65Cu20Os15. Resonant photoemission near the Os 5p → 5d and 4f → 5d transitions has been employed to show that the feature in the valence band with the maximum intensity at 1.5 (1) eV below the Fermi level is predominantly of the Os 5d character. This has been additionally verified by conducting the photoemission measurements in the constant-initial-state mode and by using the effect of the Cooper minimum in the photoionization cross section of the Os 5d orbitals. The valence band feature with the maximum intensity at 3.7 (1) eV below the Fermi level has been shown as being due mainly to the states of the Cu 3d character. The Os 5d and Cu 3d empirical partial density of states have been determined from the photoemission spectra. The decrease of intensity towards the Fermi level has been interpreted as being indicative of the presence of a theoretically predicted pseudogap around the Fermi level. It has been indicated, however, that the Fermi cut-off also contributes to the observed intensity decrease. It has been demonstrated that the energy resolution of the spectroscopic measurements performed so far on quasicrystals was not high enough to unambiguously determine the presence of such a pseudogap. No unusual features in the valence band of icosahedral Al65Cu20Os15, which could be ascribed to its quasiperiodic nature, have been observed within the resolution of the experiment. High energy-resolution spectroscopic measurements were also shown to be essential to observe the theoretically predicted spikiness of the density of states in quasicrystals. A critical review of published spectroscopic data on the electronic structure of quasicrystals has also been presented.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 278 (2000), S. 84-89 
    ISSN: 1435-1536
    Schlagwort(e): Key words Hyaluronate ; Depolymerization ; Phenothiazines ; Sulfacetamide ; UV irradiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Phenothiazines (promazine, promethazine, chlorpromazine) and sulfacetamide, known as phototoxic drugs, depolymerize aqueous sodium hyaluronate (HA) on exposure to light. The reduction in the HA molecular weight was followed by size-exclusion chromatography with low-angle laser light scattering. In the low-concentration region of the drugs below 0.05 mM, the rate constants of depolymerization increased. The molecular weight of HA was practically unchanged without UV irradiation in the presence of drugs or with UV irradiation in the absence of drugs, indicating the phenothiazines and sulfacetamide require photoenergy to yield any kind of damaging chemical species for HA depolymerization. An involvement of active oxygen radicals in the effects of promazine and promethazine was evidenced by inhibition under anaerobic conditions. Further, addition of mannitol controlled the reaction in the presence of oxygen, pointing to hydroxyl radicals as the damaging agent. Chlorpromazine and sulfacetamide preferably depolymerized HA under anaerobic conditions, suggesting the participation of hydrated electrons.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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