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  • 1
    Electronic Resource
    Electronic Resource
    Modelling the behaviour of gas bubbles in an epoxy resin: Evaluating the input parameters for a diffusion model using a free-volume approach (1995)
    Springer
    Journal of materials science 30 (1995), S. 916-922 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Models based on a mass-diffusion theory successfully represent the growth and collapse of gas bubbles in an epoxy resin. A quantitative evaluation of the steady-state diffusion equations requires values for the diffusion coefficient and the solubility of the mobile species within the resin precursor. These parameters are affected by changes in temperature and/or pressure, and they are generally not measured as part of a processing schedule. Models have been evaluated that predict the temperature dependence of the gas diffusion coefficient in the resin. A free volume approach describes the viscosity of the resin successfully at temperatures of up to 100 K above the glass-transition temperature. At higher temperatures, a thermal-energy-barrier approach is more appropriate. A direct correlation between the viscosity of the resin and the gas diffusion coefficient is proposed which is considered to be applicable to any gas/resin system where specific component interactions are negligible and the solute concentration is sufficiently low that it does not affect the free volume of the medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01178425
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  • 2
    Electronic Resource
    Electronic Resource
    Ambient and biochemical effect monitoring of workers exposed to ethylene oxide (1998)
    Springer
    International archives of occupational and environmental health 71 (1998), S. 14-18 
    Details
    ISSN: 1432-1246
    Keywords: Key words Ambient monitoring ; Biological monitoring ; Biochemical effect monitoring ; Protein adducts ; Ethylene oxide ; N-Alkyl-Edman method ; N-2-Hydroxyethylvaline ; Sterilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives: Ethylene oxide is an alkylating agent known to be a directly acting mutagen and carcinogen. This study describes the relationship between workplace ambient air concentrations of ethylene oxide and the concentration of N-2-hydroxyethylvaline in the globin of exposed workers. Methods: During the sterilization of medical equipment, 12 workers were occupationally exposed to ethylene oxide. Personal and stationary ambient air measurements were carried out to monitor the external exposure. The determination of the protein adducts was based on the N-alkyl-Edman method, introducing a new commercially available dipeptide standard for calibration purposes. Results: Ethylene oxide concentrations ranging from 0.2 to 8.5 ppm were found in the workplace air. The adduct concentrations ranged from 5,219 to 32,738 pmol N-2-hydroxyethylvaline/g globin in the case of regularly exposed workers (n = 9) and from 518 to 3,321 pmol N-2-hydroxyethylvaline/g globin for three persons with occasional contact with ethylene oxide. Conclusions: The Deutsche Forschungsgemeinschaft established in 1993 a relationship between the ethylene oxide concentration in ambient air and the amount of N-2-hydroxyethylvaline in human globin. By extrapolation, constant exposure to 1 ppm ethylene oxide should yield approximately 4,000 pmol N-2-hydroxyethylvaline/g globin. The ambient air concentrations of ethylene oxide and the amount of N-2-hydroxyethylvaline determined within the present study confirm this extrapolation in practice. In addition, the determination of adducts based on the use of commercially available dipeptide standards for calibration purposes turned out to be an advantageous alternative to the commonly used protein standards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004200050244
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Biomonitoring of manganese in blood, urine and axillary hair following low-dose exposure during the manufacture of dry cell batteries (1999)
    Springer
    International archives of occupational and environmental health 72 (1999), S. 521-527 
    Details
    ISSN: 1432-1246
    Keywords: Key words Manganese ; Biomonitoring ; Ambient air monitoring ; Hair analysis ; Dry cell manufacturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives: A cross-sectional study was carried out on 100 workers from three different workplace areas in a dry cell battery manufacturing plant and on 17 currently nonexposed referents, to examine the relationship between the external exposure to manganese dioxide (MnO2) and the body burden of manganese in blood, urine and hair. Methods: Inhalable dust was measured gravimetrically after stationary active sampling. Manganese was analyzed in dust samples, blood, urine and axillary hair by atomic absorption spectro- metry. Results: The average air concentrations of manganese in the three workplace areas were 4 μg/m3 (range: 1–12 μg/m3), 40 μg/m3 (12–64 μg/m3) and 400 μg/m3 (137–794 μg/m3). Manganese in blood and axillary hair correlated with airborne manganese in group-based calculations but not on an individual level. The manganese concentrations varied between 3.2 μg/l and 25.8 μg/l in the blood (mean: 12.2 ± 4.8 μg/l) and between 0.4 μg/g and 49.6 μg/g in hair (mean: 6.2 ± 6.2 μg/g in the proximal sequence), respectively. The results for the nonexposed referents were 7.5 ± 2.7 μg/l (mean) in the blood (range: 2.6–15.1 μg/l) and 2.2 ± 1.8 μg/g (mean) in axillary hair (range: 0.4–6.2 μg/g). In these matrices, manganese differed significantly between the highly exposed workers and both the reference and the low-exposure group. Manganese in blood revealed the lowest background variance. No differences for manganese in urine were observed between workers (mean: 0.36 ± 0.42 μg/l, range: 0.1–2.2 μg/l) and referents (mean: 0.46 ± 0.47 μg/l, range: 0.1–1.7 μg/l). Conclusions: Manganese in blood is a specific and suitable parameter for the biomonitoring of MnO2 exposure, although its validity is limited to group-based calculations. Urinary manganese failed to allow a differentiation between exposed workers and referents. The suitability of manganese analysis in hair for biomonitoring purposes suffers from a relatively great background variation as well as from analytical problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004200050410
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    Paper (German National Licenses)
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