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  • 1
    ISSN: 1572-9729
    Keywords: model reduction ; Monod model ; nonlinear parameter estimation ; pure culture ; repeated batch experiments ; toluene degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Experimental data indicate that certain microbiological degradation experiments have a limited reproducibility. Nine identical batch experiments were carried out on 3 different days to examine reproducibility. A pure culture, isolated from soil, grew with toluene as the only carbon and energy source. Toluene was degraded under aerobic conditions at a constant temperature of 28 °C. The experiments were modelled by a Monod model – extended to meet the air/liquid system, and the parameter values were estimated using a statistical nonlinear estimation procedure. Model reduction analysis resulted in a simpler model without the biomass decay term. In order to test for model reduction and reproducibility of parameter estimates, a likelihood ratio test was employed. The limited reproducibility for these experiments implied that all 9 batch experiments could not be described by the same set of parameter values. However, experiments carried out the same day (within the same run) were more uniform than experiments carried out on different days (between runs), and a common set of parameter estimates could be accepted for experiments within runs, but not for experiments from different runs. The limited reproducibility may be caused by variability in the preculture, or more precisely, variations in the physiological state of the bacteria in the precultures just before used as inoculum.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7225
    Keywords: breast cancer ; database ; register
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: Clinical databases have been invented to monitor treatment outcomes, therapies or diseases, often in great detail. The traditional population-based cancer registry has been invented to collect a minimum of information about all incident cancers. Do clinical databases render population-based cancer registers obsolete as sources of cancer cases for epidemiological study? Methods: We compared the study base of first incident breast cancer cases in Denmark in 1978–1994 known from the national cancer register and from the national clinical database on breast cancer patients. The clinical database is used for monitoring protocoled treatment. Results: Combining the two data sources we found 48,522 first primary breast cancers in Denmark 1978–1994. Of these, 37,640 were included in both data sources, 2151 were included only in the clinical database, and 8731 were included only in the cancer register. A major part of the difference between the two data sources was due to treatment-focused data collection in the clinical database, and a minor part due to differences in the registration of second primaries, date of diagnosis and invasiveness. Conclusions: Cancer incidence data are sensitive to registration procedures and definitions. Clinical cancer databases cannot generally replace the traditional cancer register as a reliable data source for incident cancer cases in a national population.
    Type of Medium: Electronic Resource
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