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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 26 (1998), S. 859-869 
    ISSN: 1573-9686
    Keywords: Spectral analysis ; Matching pursuit ; Stomach ; Gastric motility ; Electrogastrography ; Evolutionary programming ; Signal analysis ; Electrogastrogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The electrogastrogram (EGG) is a surface measurement of gastric myoelectrical activity. The normal frequency of gastric myoelectrical activity in humans is 3 cycles/min. Abnormal frequencies in gastric myoelectrical activity have been found to be associated with functional disorders of the stomach. The aim of this article was, therefore, to develop new time-frequency analysis methods for the detection of gastric dysrhythmia from the EGG. A concept of overcomplete signal representation was used. Two algorithms were proposed for the optimization of the overcomplete signal representation. One was a fast algorithm of matching pursuit and the other was based on an evolutionary program. Computer simulations were performed to compare the performance of the proposed methods in comparison with existing time-frequency analysis methods. It was found that the proposed algorithms provide higher frequency resolution than the short time Fourier transform and Wigner-Ville distribution methods. The practical application of the developed methods to the EGG is also presented. It was concluded that these methods are well suited for the time-frequency analysis of the EGG and may also be applicable to the time-frequency analysis of other biomedical signals. © 1998 Biomedical Engineering Society. PAC98: 8780+s, 0705Kf
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 533-549 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A periodic countercurrent whole beer process was developed for the recovery of novobiocin to eliminate the high cost of mycelium filtration and accompanying antibiotic losses in the filter cake. In such a process screened, but unfiltered, novobiocin fermentation beer is contacted with a special grade of an anionic-exchange resin in a series of specially designed, well mixed columns. Each column is fitted with a screen sized to retain resin within the column but allow the cells to press. Periodically the lead column is isolated from the column train, washed free of beer solids, and eluted. A freshly eluted column is placed in the trail position to allow countercurrent operation. The eluate is then processed to crystalline product.A mathematical model for the sorption of novobiocin was developed based on a suitable continuity equation and mass transfer and equilibrium relationships determined in the laboratory. Digital computations of this model correlated well with laboratory and pilot plant data, and predicted well the performance of the production units. This simulation has been in continued use to predict and reoptimize plant operation as process changes (such as improved beer titers, increased production rate, and the evaluation of superior ion-exchange resins) occurred or were anticipated.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 13 (1971), S. 271-292 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxygen transfer coefficients were evaluated for a 14-liter stirred tank fermentor equipped with an oxygen probe, employing elemental copper adsorbed on a weakly basic anion-exchange resin as a solid phase oxygen acceptor. The use of a solid phase oxygen acceptor allowed evaluation of mass transfer resistances associated with the solid phase, and the effect of an oxygen adsorbing solid phase on the overall oxygen transport system, portions of the oxygen transfer process that are neglected by the conventional sulfite oxidation method commonly employed. It was concluded from the data obtained that a transport pathway involving transfer of oxygen to particles present near the air-water interface was a significant oxygen transport pathway for the system studied. Oxygen probe measurements performed on the bulk liquid did not recognize this pathway, suggesting that data taken on biological systems by use of techniques involving oxygen concentration measurements in the bulk liquid may not give the true oxygen absorbing capacity of a system.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 4 (1962), S. 65-78 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mathematical models for the kinetics of 1-dehydrogenation of steroids by Septomyxa affinis are considered. A model providing for product inhibition fits experimental data best. Product inhibition was also demonstrated directly.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 151-155 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The physiological activity of microorganisms in environments with low dissolved oxygen concentrations often differs from the metabolic activity of the same cells growing under fully aerobic or anaerobic conditions. This article describes a laboratory-scale system for the control of dissolved oxygen at low levels while maintaining other parameters, such as agitator speed, gas flowrate, position of sparger outlet, and temperature at fixed values. Thus, it is possible to attribute in dilute nonviscous fermentations all physiologic changes solely to changes in dissolved oxygen. Experiments were conducted with Azotobacter vinelandii and Escherichia coli. Critical oxygen concentrations for growth (that value of oxygen allowing growth at 97% of μmax) were measured as 0.35 ± 0.03 mg/L for A. vinelandii and 0.12 ± 0.03 mg/L for E. coli. These values are significantly different from the commonly quoted values for critical oxygen concentrations based on respiration rates. Because of the superior dissolved oxygen control system and an improved experimental protocol preventing CO2 limitation, we believe that the values reported in this work more closely represent reality.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 29 (1991), S. 351-357 
    ISSN: 1741-0444
    Keywords: Bioelectric potential ; Electrogastrogram ; Electromyography ; Gastric motility ; Slow wave ; Stomach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The gastric electric activity paces the contractions of the stomach and can be measured noninvasively using surface electrodes placed on the abdomen. In this paper, response of the gastric electric activity to water and a solid meal was investigated using surface electrodes. Applying an improved recording technique, power spectral analysis and statistical analysis methods, the gastric electric activity in preprandial, postwater and postprandial states was measured and analysed from ten healthy volunteers. To more convincingly show the effect of water and the solid meal on the gastric slow wave and gastric motility, simultaneous recordings of the cutaneous EGG and manometric activities in the stomach were performed in three gastroparetic patients. It was found that water does not induce contractions of the stomach, but the gastric slow wave amplitude increases (p〈0·05) and frequency decreases (p〈0·05). The solid meal results in an increase in both the amplitude (p〈0·01) and the frequency (p〈0·02) of the gastric slow wave. It appears that the postprandial EGG amplitude increases because of a combination of stomach contractions and gastric distension bringing the stomach closer to the recording electrodes. The slow wave frequency, however, correlates well with stomach contractions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 31 (1993), S. 60-67 
    ISSN: 1741-0444
    Keywords: Electrogastrogram ; Electrogastrography ; Gastric motility ; Intestinal motility ; Myoelectrical activity ; Spectral analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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