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  • 1
    Electronic Resource
    Electronic Resource
    Metabolic precursor regulation of aflatoxin formation in toxigenic and non-toxigenic strains ofAspergillus flavus (1989)
    Springer
    Mycopathologia 107 (1989), S. 127-130 
    Details
    ISSN: 1573-0832
    Keywords: aflatoxin ; Aspergillus flavus ; non-toxigenic O-methylsterigmetocystin ; sterigmetocystin ; nontoxigenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Non-aflatoxin-producing isolates ofAspergillus flavus from nature and isolates ofA. flavus that had lost their toxigenic trait following laboratory transfer were compared biochemically. After the addition of aflatoxin B1 precursors sterigmatocystin or O-methylsterigmatocystin to whole cell cultures, the non-toxin producing isolates from nature remained non-toxigenic while toxigenicity was restored in the nontoxigenic laboratory strains. Results imply a lack of enzymes needed for biochemical conversions of precursors to aflatoxin B1 in natural non-producers and suppression of these enzymes in the nonproducing laboratory strains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707549
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  • 2
    Electronic Resource
    Electronic Resource
    Identification of triploid Citrus by isozyme analysis (1996)
    Springer
    Euphytica 90 (1996), S. 223-231 
    Details
    ISSN: 1573-5060
    Keywords: Citrus ; digital densitometry ; isozymes ; triploids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seedlessness is a desirable horticultural attribute in Citrus and is positively associated with triploidy. The conventional cytological method for triploid identification is a laborious technique involving the preparation of root tips for chromosomal analysis. Digital densitometry of isozymes, however, offers the possibility of distinguishing triploid Citrus from large populations of seedlings both quickly and cheaply. Where there are no gene dosage regulation effects, greater band density should be evident in the allozyme contributed by the diploid gamete for a heterozygous locus. The isozymes of 4 enzymes; malate dehydrogenase, 6-phosphogluconate dehydrogenase, shikimate dehydrogenase, and phosphoglucose isomerase, were investigated with polyacrylamide gel electrophoresis. Band densities of these isozymes for triploid Citrus, their diploid siblings and diploid progenitors were measured using a digital densitometer. Of the 4 enzymes investigated only allozymes for shikimate dehydrogenase exhibited consistent differences over a wide range of Citrus cultivars. Greater band density was evident in the allozyme contributed by the diploid gamete. The band density ratio between allozymes for triploid Citrus was close to 0.5, while for diploid Citrus band density ratios were close to 1.0. This effect is due to the extra protein coded by the additional gene dose and was not observed in diploids. Shikimate dehydrogenase proved to be an accurate molecular marker for distinguishing between diploid and triploid Citrus for heterozygous progeny.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023862
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  • 3
    Electronic Resource
    Electronic Resource
    Substrate depletion during formation of aflatoxin and kojic acid on corn inoculated with Aspergillus flavus (1986)
    Springer
    Mycopathologia 93 (1986), S. 105-107 
    Details
    ISSN: 1573-0832
    Keywords: Aspergillus flavus ; starch ; reducing sugars ; kojic acid ; aflatoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Depletion of sugar and starch carbon sources and concomitant formation of secondary fungal metabolites, aflatoxin and kojic acid, were examined in growing corn inoculated with Aspergillus flavus. Kernels from control and inoculated ears were removed and analyzed after 16, 24, 48, 96 and 168 hrs. Reducing sugars were not significantly different for inoculated and control non-inoculated samples, but after 168 hrs (seven days) starch content was 20% lower in inoculated than in control samples. Kojic acid was detected before aflatoxins formed. Kojic acid, the oxidized product of kojic acid, and aflatoxin were all present in samples two days from inoculation. The formation of this oxidation product may influence toxin levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00437741
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  • 4
    Electronic Resource
    Electronic Resource
    The occurrence of Aspergillus flavus in vegetative tissue of cotton plants and its relation to seed infection (1986)
    Springer
    Mycopathologia 95 (1986), S. 171-174 
    Details
    ISSN: 1573-0832
    Keywords: Aspergillus flavus ; aflatoxin ; Gossypium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Twenty-seven mature cotton bolls with Aspergillus flavus Link colonies naturally occurring on the surface of the boll or lint were collected in the field in Arizona along with their subtending stems and peduncles. Bolls inoculated through the carpel wall 30 days after anthesis were allowed to mature in the field and were collected in the same manner. The seed and stem and peduncle sections of each boll were surface-sterilized, plated on agar media and observed for A. flavus. Seventy-eight percent of the naturally contaminated bolls with A. flavus in the seed also had the fungus in the stem and peduncle, whereas only 31% of the naturally contaminated bolls with no A. flavus in the seed had the fungus in the stem or peduncle. This difference was significant (P=0.0125), indicating a positive relationship between seed infection and stem and peduncle infection. All of the bolls inoculated through the carpel wall had A. flavus in the seed, but only 11% of the stem and peduncle sections were infected, indicating that the fungus does not readily grow downward from the boll into the supporting stem or peduncle. This unidirectional pattern of movement (upward) was further substantiated in greenhouse experiments where cotton seedlings were inoculated at the cotyledonary leaf scar with A. flavus and plants were sequentially harvested, surface sterilized and plated. Aspergillus flavus was isolated from the cotyledonary leaf scar, flower buds, developing bolls, and stem sections in the upper portion of the plant. It was never isolated from roots or stem sections below the cotyledonary node, again indicating that the fungus does not readily move downward through the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00437123
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    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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