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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5191-5200 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Steady state Förster energy transfer is investigated in multilayer structures of self-assembled films prepared via the layer-by-layer deposition of oppositely charged polyelectrolytes. The samples consist of a single layer of the conjugated polymer poly(p- phenylene vinylene) (PPV) as a donor, several layers of poly(styrene sulfonate) (PSS), and poly(allylamine hydrochloride) (PAH) as a transparent spacer, and a single layer of dye labeled PAH as an acceptor. The dyes are rhodamine B and fluorescein, whereas the molar ratio with respect to the PAH monomers is less than 0.2% for both systems. The steady state fluorescence intensity of the PPV is measured for a series of samples with different spacer thicknesses. The spacer thicknesses are evaluated from x-ray reflectivity measurements. At large thickness of the spacer the donor intensity I versus distance d follows the 1/(1+(d0/d)4) law as theoretically predicted for the case of ideal two-dimensional layers. At short distances a different behavior is observed which is explained first, by the low lateral density of the acceptor molecules and second, by a distribution of the dyes normal to the layer plane. Good agreement between the experimental data and computer simulations is obtained under the assumption of a Gaussian distribution of both donor and acceptor molecules, in the direction normal to the film plane with a width of 25–30 Å. However, a mismatch is observed between the Förster radius derived from the spectroscopic properties and that obtained from the layer-to-layer energy transfer. This is discussed under the consideration of a nonperfect layer structure and the photophysics of the PPV. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1173
    Keywords: Schlüsselwörter Steinkohlenteer ; Polyzyklische aromatische Kohlenwasserstoffe ; Externe Therapie ; 1-Hydroxypyren ; Renale Ausscheidung ; Key words Coal tar ; Polycyclic aromatic hydrocarbons ; Topical treatment ; 1-Hydroxypyrene ; Urinary excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In order to study the dermal uptake, time course, and urinary excretion of polycyclic aromatic hydrocarbons, the concentration of 1-hydroxypyrene in urine was determined by means of high performance liquid chromatography with fluorescence detection before, during, and after the topical treatment with coal tar in 19 patients suffering from prurigo simplex subacuta, microbial eczema, atopic dermatitis, eczematization after scabies, exanthematous lichen ruber, pityriasis lichenoides and cutaneous sarcoidosis. Beginning with a value of 6.04±2.06 µg 1-hydroxypyrene/g creatinine before treatment, the urinary excretion significantly increased during the therapy with coal tar (p〈0.0001 at 3rd, 5th, and 6th day of therapy). A maximum was reached at day 8 of topical treatment with a value of 584.35± 191.96 µg 1-hydroxypyrene/g creatinine (p〈0.002). Already during treatment at day 10 there was a beginning decrease of 1-hydroxypyrene to 361.63±170.13 µg/g creatinine. After the end of treatment, the excretion further decreased reaching a value of 5.31±2.85 µg 1-hydroxypyrene/g creatinine at the 10th day after therapy. Skin carcinomas due to therapeutical use of coal tar occur extremely rarely and only after vergoten, non-controlled use. We suggest that the duration of exposure is the most important factor for the carcinogenic effect of coal tar.
    Notes: Zusammenfassung Bei insgesamt 19 Patienten mit Prurigo simplex subacuta, mikrobiellem, atopischem sowie postskabiösem Ekzem, Lichen ruber exanthematicus, Pityriasis lichenoides and Hautsarkoidose wurde die 1-Hydroxypyren-Konzentration im Urin vor, während und nach einer externen Steinkohlenteerbehandlung mittels Hochleistungsflüssigkeitschromatographie mit Fluoreszenzdetektion bestimmt, um so einen Rückschluß auf die dermale Aufnahme und den zeitlichen Verlauf der renalen Exkretion der potentiell kanzerogenen polyzyklischen aromatischen Kohlenwasserstoffe aus dem Teer zu erhalten. Ausgehend von einem prätherapeutischen Wert von 6,04±2,06 µg 1-Hydroxypyren/g Kreatinin steigt die renale Ausscheidung während der Teerbehandlung signifikant an (p〈0,0001 am 3., 5. und 6. Tag der Therapie), um am achten Tag das Maximum von 584,35±191,96 µg 1-Hydroxypyren/g Kreatinin zu erreichen (p〈0,002). Noch unter der Teerbehandlung ist am Tag 10 ein erster Abfall von 1-Hydroxypyren auf 361,63± 170,17 µg/g Kreatinin zu verzeichnen. Nach Absetzen der Teerbehandlung sinkt die Ausscheidung weiter steil ab, um am 10. Tag nach Therapie mit einem Wert von 5,31± 2,86 µg 1-Hydroxypyren/g Kreatinin wieder Ausgangsniveau zu erreichen. Da Hautkarzinome durch eine therapeutische Teeranwendung extrem selten auftreten und auf eine unkontrollierte und jahrzehntelange Anwendung zurückzuführen sind, wird gefolgert, daß die Expositionsdauer für die kanzerogene Wirkung des Teers anscheinend eine entscheidende Rolle spielt.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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