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  • 1
    Electronic Resource
    Electronic Resource
    An investigation of the physico-chemical basis of foaming in fungal fermentations (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 801-807 
    Details
    ISSN: 0006-3592
    Keywords: foaming ; fermentations ; biochemical basis ; biosurfactants ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed physico-chemical analysis of two foaming fungal fermentations was carried out to identify that key groups of compounds responsible for foam formation. Fermentations were carried out on a 20-L scale in a stirred aerated tank, over 7 days, using a commercial, defined medium. The organisms investigated were Penicillium herqueii, a hyphomycete, and an unidentified Ingoldian fungus. Samples of broth and, where possible, foam were analyzed to determine which groups of compounds were concentrated into generated foams. Surface tension, bulk viscosity, and antifoam A concentration were additionally determined in broth samples. To date the cause of foaming in fermentations has been attributed to the surfactant properties of extracellular proteins. This assumption was tested and found to be incomplete as many additional groups of biochemicals were found to be enriched into the foam. The results of the investigation revealed the presence of proteins, carbohydrates, α-keto acids, and lipophilic biosurfactants, particularly extracellular pigments, enriched within stable foams. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440705
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  • 2
    Electronic Resource
    Electronic Resource
    Rapid screening for metabolite overproduction in fermentor broths, using pyrolysis mass spectrometry with multivariate calibration and artificial neural networks (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1205-1216 
    Details
    ISSN: 0006-3592
    Keywords: pyrolysis mass spectrometry ; artificial neural networks ; fermentor broths ; regression analysis ; chemometrics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Binary mixtures of model systems consisting of the antibiotic ampicillin with either Escherichia coli or Staphylococcus auresu were subjected to pyrolysis mass spectrometry (PyMS). To deconvolute the pyrolysis mass spectra, so as to obtain quantitative information on the concentration of ampicilin in the mixtures, partial least squares regression (PLS), principal components regression (PCR), and fully interconnected feedforward artificial neural networks (ANNs) were studied. In the latter case, the weights were modified using the standard backpropagation algorithm, and the nodes used a sigmoidal squsahing funciton. It was found that each of the methods could be used to provide calibration models which gave excellent predictions for the concentrations of ampicillin in samples on which they had not been trained. Furthermore, ANNs trained to predict the amount of ampicilin in E. coli were able to generalise so as to predict the concentration of ampicillin in a S. aureus background, illustrating the robustness of ANNs to rather substantial variations in the biological background. The PyMS of the complex mixture of ampicilin in bacteria could not be expressed simply in terms of additive combinations of the spectra describing the pure components of the mixtures and their relative concentrations. Intermolecular reactions took place in the pyrolysate, leading to a lack of superposition of the spectral components and to a dependence of the normalized mass spectrum on sample size. Samples from fermentations of a single organism in a complex production medium were also analyzed quantitatively for a drug of commercial interest. The drug could also be quantified in a variety of mutant-producing strains cultivated in the same medium. The combination of PyMS and ANNs constitutes a novel, rapid, and convenient method for exploitation in strain improvement screening programs. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260441008
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  • 3
    Electronic Resource
    Electronic Resource
    Equibiaxial deformation of poly(4-methyl-1-pentene) by a forging process (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 535-540 
    Details
    ISSN: 0887-6266
    Keywords: poly (4-methyl-1-pentene) ; isotactic polypropylene ; biaxial deformation ; stress-strain behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(4-methyl-1-pentene) (PMP) has been uniaxially compressed by a forging (equibiaxial) process. The rheology of the process has been examined for this semicrystalline polyolefin, melting point about 235°C. The yield energy, area under the compressive stress-strain curve up to the yield point, as a function of temperature was found to consist of two linear components of different slope. These two linear relations arise from the glassy and crystalline phases of PMP. The intercept temperature (Ti) at zero yield energy for the glassy phase has been evaluated. The attainable maximum compression ratio without sample rupture (CRmax) increased steadily on increasing forging temperature above Ti, and below Tm. In this range, the crystalline relaxation temperature (Tc), evaluated from an Arrhenius plot of yield stress was 160°C. Above Tc, a CRmax of 240 was reached. This value is five times higher than that attained for isotactic polypropylene (i-PP). However, the draw efficiency evaluated by elastic recovery in the plane direction of PMP (0.76) is lower than for i-PP (0.97). Differential scanning calorimetry analyses showed that the melting peak became a complex doublet on increasing compression ratio ( 〉 100). The drawing and stress-strain behavior of PMP are compared with i-PP. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320314
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  • 4
    Electronic Resource
    Electronic Resource
    Vanadate reduces sodium-dependent glucose transport and increases glycolytic activity in LLC-PK1 epithelia (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 158 (1994), S. 459-466 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of vanadate pentoxide on apical sodium-dependent glucose transport in LLC-PK1 epithelia was examined. Epithelia grown in the presence or absence of 1 μM vanadate formed confluent monolayers and exhibited no differences in DNA, protein, or ultrastructure. Vanadate-supplemented epithelia demonstrated a lower steady-state α-methyl-D-glucopyranoside (AMG) concentrating capacity and a twofold reduction in apical AMG uptake Jmax. This decreased AMG transport occurred as a consequence of a reduction in the number of transport carriers and was not associated with a change in the sodium electrochemical gradient. The vanadate-induced reduction in apical glucose carrier functional activity and expression was accompanied by a stimulation of intracellular glycolytic flux activity, as evidenced by increased glucose consumption, lactate production, PFK-1 activity, and intracellular ATP. There was no difference in intracellular cAMP levels between vanadate-supplemented and non-supplemented epithelia. These results demonstrate an association between stimulation of glycolytic pathway activity and an adaptive response in the form of a reduction in the function and expression of the sodium-dependent apical glucose transporter in LLC-PK1 epithelia. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041580310
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  • 5
    Electronic Resource
    Electronic Resource
    Scanning probe microscope imaging of polyaniline thin films in non-contact mode (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 814-817 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The structure of electropolymerized thin films of polyaniline has been studied using the techniques of contact and non-contact scanning probe microscopy (SPM). Films exposed to Ir+ cations in solution, as well as unexposed films, were examined. Contact-mode SPM images of these films reveal only a diffuse, amorphous surface structure in both types of film, while non-contact SPM images indicate an intricate, nanometer-scale domain structure. Film growth is in a layer-by-layer mode, with each layer consisting of small polymer bundles of average dimension 1000 ± 75 Å. The Ir+ incorporation in these films does not involve a restructuring of the film morphology. The relevance of the microscopic domain structure to models describing conduction mechanisms in these films is also discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740211113
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  • 6
    Electronic Resource
    Electronic Resource
    A review on the tensile strength of polyethylene fibers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 266-268 
    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
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340406
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  • 7
    Electronic Resource
    Electronic Resource
    Properties of oriented polyethylene bars of large cross section (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1211-1215 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 solid-state extrusion technique has been used to prepare uniaxially oriented polyethylene bars with rectangular end cross sections of 6 × 50 mm2. They were extruded at 110°C from billets of high density polyethylene. The tensile modulus and strength for the extrudate with a draw ratio (DR) of 14 were 17.9 and 0.32 GPa, respectively. The mechanicals were also measured in the transverse direction by means of the proportional elastic limit (PEL) bending test. The PEL results do not change after DR 14 due to the fibrillate structure formation. Crystallinity and shrinkage tests were made on samples taken over the bar cross section. They show that uniform properties were achieved across the width of the bar with proper die design. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520905
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  • 8
    Electronic Resource
    Electronic Resource
    A Tribute to William P. (Bill) Gergen (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1-2 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340102
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  • 9
    Electronic Resource
    Electronic Resource
    Composite of polyethylene and kenaf, a natural cellulose fiber (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 1781-1783 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070541121
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  • 10
    Electronic Resource
    Electronic Resource
    Transformation-associated recombination between diverged and homologous DNA repeats is induced by strand breaks (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 10 (1994), S. 93-104 
    Details
    ISSN: 0749-503X
    Keywords: Transformation ; recombination ; DNA divergence ; DNA breaks ; rad52, radl ; DNA repeats ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Rearrangements within plasmid DNA are commonly observed during transformation of eukaryotic cells. One possible cause of rearrangements may be recombination between repeated sequences induced by some lesions in the plasmid. We have examined the mechanisms of transformation-associated recombination in the yeast Saccharomyces cerevisiae using a plasmid system which allowed the effects of physical state and/or extent of homology on recombination to be studied. The plasmids contain homologous or diverged (19%) repeats of the URA3 genes (from S. cerevisiae or S. carlsbergensis) separated by the genetically detectable ADE2 colour marker. Recombination during transformation for covalently closed circular plasmids was over 100-fold more frequent than during mitotic growth. The frequency of recombination is partly dependent on the method of transformation in that procedures involving lithium acetate or spheroplasting yield higher frequencies than electroporation. When present in the repeats, unique single-strand breaks that are ligatable, as well as double-strand breaks, lead to high levels of recombination between diverged and identical repeats. The transformation-associated recombination between repeat DNAs is under the influence of the RAD52 and RAD1 genes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320100109
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