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  • 1
    Electronic Resource
    Electronic Resource
    Influence of trace elements and nitrogen sources on versicolorin production by a mutant strain of Aspergillus parasiticus (1979)
    Springer
    Mycopathologia 69 (1979), S. 161-166 
    Details
    ISSN: 1573-0832
    Keywords: Aspergillus parasiticus ; Furobenzofuran ; Versicolorin A ; Versicolorin C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A mutant strain of Aspergillus parasiticus blocked in aflatoxin biosynthesis accumulates versicolorin A and versicolorin C. The effect of trace elements on the growth and versicolorin production by this strain was studied in a defined medium. The omission of manganese was slightly stimulatory to versicolorin production; when zinc was omitted from the medium, no detectable versicolorins were produced. Experiments on nitrogen sources in a highsucrose medium indicated that fourfold to fivefold increases in versicolorin yields could be obtained by substituting 3 ml/l corn steep liquor or 0.1 M NH4NO3 for the 0.023 M (NH4)2SO3 used previously as the nitrogen source in studies on versicolorin production by this strain. These improved yields will facilitate attempts to accumulate enough versicolorin A and versicolorin C for toxicity and carcinogenicity testing. Chromatographic profiles of mycelial extracts of cultures grown in a defined medium with 0.1 M NH4NO3 as the nitrogen source revealed 2 previously unrecognized compounds. The accumulation of these new metabolites in a mutant blocked in aflatoxin production may indicate that they are biosynthetically related to aflatoxin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00452829
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of acetone on production of aflatoxins and versicolorin pigments by resting cell cultures of aspergillus parasiticus (1976)
    Springer
    Mycopathologia 58 (1976), S. 9-12 
    Details
    ISSN: 1573-0832
    Keywords: Aflatoxins ; Versicolorins ; Aspergillus parasiticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Resting cell cultures of Aspergillus parasiticus were grown in medium containing four different concentrations of glucose, with and without acetone. In addition, the effect of different equimolar concentrations of acetone, acetic acid, ethanol, and sodium acetate was compared at two glucose levels. Aflatoxin and versicolorin pigment production increased in resting cell medium containing increasing concentrations of glucose. In the presence of glucose high concentrations of acetone (1.0 and 0.25 M) inhibited secondary biosynthesis and low concentrations of acetone (0.1, 0.025 and 0.01 M) stimulated secondary biosynthesis of aflatoxins and versicolorin pigments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00493586
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamic behavior of a single screw plasticating extruder part I: Experimental study (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 144-151 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: The dynamic responses of a 2-1/2 inch single screw plasticating extruder and extrusion line were investigated. Step changes in screw speed, take-up speed, back pressure, and processing materials were used to determine the transient responses of barrel pressures, die pressure, melt temperature, and extrudate thickness. Dynamic responses of the entire extrusion line can be explained by the flow mechanism of the extruder and the logical properties of the polymer used. A capillary rheometer was also used to determine if it could simulate pressure responses in the extruder for screw speed changes. Results showed that capillary rheometer was helpful in estimating the short term pressure responses in the die.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260206
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamic behavior of a single screw plasticating extruder part II: Dynamic modeling (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 152-161 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: The dynamic response of a 2.5 inch plasticating extruder and the extrusion line are modeled using high density polyethylene and acrylics us extrudate. Screw speed, back pressure valve position, and material changes are used as forcing functions. Three fundamental transfer functions in the Laplace domain: a first order, a second order, and a lead-lag, are developed to simulate the short term and long term responses of temperatures, pressures, and extrudate thickness. A kinetic-elastic model which can predict rheological properties of non-Newtonian, viscoelastic materials is also applied to the pressure responses of the extrusion process. This model can fit the experimental data well but due to the complexity involved in its parameter setting, more modifications are required before it can be applied for the control of extrusion process.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260207
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  • 5
    Electronic Resource
    Electronic Resource
    Process control of polymer extrusion. Part II: Feedforward control (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 205-213 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: A feedforward plus feedback control method (FFC) and an adaptive feedforward plus feedback control method (AFFC) were proposed in this study to control the extrudate thickness of polymer extrusion. They were tested by step changes of screw speed and feedstock, and square wave type of screw speed changes. It is found that these feedforward control methods worked very well for various load disturbances but they required a good process model and accurate on-line measurements of manipulated variables and load variables. The feedback function was necessary to compensate the over- or under-corrections of the feedforward controllers and to handle other disturbances which were not considered in the feedforward model.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260305
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  • 6
    Electronic Resource
    Electronic Resource
    Process control of polymer extrusion. Part I: Feedback control (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 197-204 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: On-line computer control of extrudate thickness was carried out using a 2-1/2 Inch single screw plasticating extruder. Predried poly(methyl methacrylate) (PMMA) was extruded through a slit die. Two feedback control methods, a conventional PI controller and a Smith predictor dead time compensation, were tried for both set point changes (i. e., extrudate thickness changes) and load changes (i. e., screw speed changes). Results showed that both the PI feedback control and the Smith predictor were satisfactory for long term set point changes but not for load changes. Since the Smith predictor may compensate the process dead time, it would be useful for regulating short term set point changes such as barrel temperature settings.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260304
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  • 7
    Electronic Resource
    Electronic Resource
    Multidimensional control of profile extrusion (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 233-238 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: Dimensional changes in complex profile extrusions are classified as overall size and local shape changes which can be related naturally and systematically to changes in operating conditions. The theoretical basis and supporting experimental data for simultaneous, independent control of certain classes of extrudate dimensions are presented for the following strategies: (1) size control by manipulating line speed relative to extruder output rate, (2) shape control by manipulating extrudate swell through adjustments in stock temperature, and (3) shape control by manipulating local die flow by adjusting the die temperature set point.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260308
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  • 8
    Electronic Resource
    Electronic Resource
    Flow analysis of rubber transfer molding (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 403-414 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: An experimental study has been carried out on rubber I transfer molding. It reveals that the filling is frequently limited more by the resistance of flow across the transfer pot than by resistance of flow through the sprue holes into the cavities. A mathematical model has been derived, which predicts semi-quantitatively the molding behavior observed. The mode1 predicts that fill time is proportional to the ratio of compound viscosity divided by molding pressure raised to about the fourth power. For the common cases where most of the fill time is from the resistance to the transverse flow on the top of the sprue plate, the fill time is proportional to about the fifth power of the ratio of transverse distance divided by the charge thickness. Experimental results showed that preheating and mastication of the compound reduced transfer time substantially. The charge pattern did not seem to have a major influence on transfer time.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760240604
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  • 9
    Electronic Resource
    Electronic Resource
    Reaction kinetics of polyurethane-polyester interpenetrating polymer network in the bulk polymerization (1985)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 25 (1985), S. 951-958 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: Kinetics of simultaneous interpenetrating networks (SIN) composed of a polyurethane resin (PU) and an unsaturated polyester resin was studied. A differential scanning calorimeter (DSC) was used to monitor the polymerization course. It was found that increasing the polyester content in a PU-polyester SIN enhanced the polymerization of PU due to the “solvent effect” of polyester. On the other hand, increasing the PU content in the SIN retarded the polymerization of polyester due to the “cage effect” of PU. Polymerization sequence of the SIN could be controlled by employing different initiators for polyester reaction. The degree of crosslinking in each SIN component had a significant effect on the dynamics of the SIN formation and on the limiting conversion of the polyester reartion.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760251507
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  • 10
    Electronic Resource
    Electronic Resource
    Rheological changes during the polymerization of polyurethane based interpenetrating polymer network(IPN) (1987)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 716-726 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: Experimental results on reactions forming polyurethanes and polyurethane-polyester Interpenetrating polymer network (IPN) are discussed with particular interest in rheological and kinetic changes before the gel point. In the IPN formation, viscosity rise is affected by the amount of styrene and polyester in the reaction system. Plots of reduced viscosity vs. conversion do not fall into a single curve. The results may be explained by the concept of having intra-molecular reaction or ring formation. The existence of hydroxyl group at the end of polyester molecule causes the graft reaction between the polyurethane phase and the polyester phase, which may speed up the viscosity rise of the reactive system. A simple method which based on rheological measurements only is proposed. This method of plotting reduced viscosity vs. reduced reaction time provides similar results as in the plots of reduced viscosity vs. conversion.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760271004
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