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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 41 (1994), S. 487-493 
    ISSN: 1432-0614
    Keywords: Key words Limonin ; Debittering ; Immobilization ; Rhodococcus fascians ; Continuous Stirred Tank Reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Limonin can be effectively degraded by Rhodococcus fascians cells. These bacteria can be entrapped in κ-carrageenan, and used in a continuous stirred tank reactor to degrade limonin in a continuous process. The effects of temperature, limonin concentration, dilution rate, and aeration on the reactor behaviour have been tested, and the results correlated with changes in limonin conversion, substrate degradation rate, and free and immobilized biomass. Results showed that the immobilized cells were able to debitter limonin-containing media and the immobilized biomass was quite stable throughout the operational conditions tested. A population of free biomass was present in the reactor, the quantity of which was dependent on dilution rate. The immobilized bacteria increased its limonin-degrading capability when the substrate concentration was increased. The aeration was not strictly necessary for limonin degradation. Additionally, the immobilized cells were active and stable for more than 2 months of continuous operation, and were able to recover their limonin-degrading capability when used intermittently. Finally, none of the main components of a juice was noticeably altered during limonin degradation, so the reactor response was good enough to consider its application.
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  • 2
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The main fragmentation pathway of vinyl triflates in mass spectra involves the loss of CF3SO2·, followed by the loss of olefin and/or CO. The loss of TfOH takes place with fragmentation of a vinylic C—H bond. TfOH2+ ions are formed via regiospecific double hydrogen transfer from five- and six-membered cyclic triflates.
    Additional Material: 3 Tab.
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  • 3
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have prepared two new tetracyclic phenylboronic esters 4 and 5 derived from myo-inositol and from 1,2-O-isopropylidene-myo-inositol, respectively. The structures of these compounds were established from NMR and IR spectra, elemental analyses, and an X-ray diffraction study in the case of 4. Compound 4 is a tetracyclic derivative of the less stable conformer of inositol (five axial hydroxy groups and one equatorial) with two dioxaboroline rings at opposite faces of the six-membered ring, one formed between the boron atom and the axial hydroxyl groups at C-3 and C-5 and the other between the boron atom and the hydroxyl groups at C-4 and C-6, and a dioxaborolidine ring bridging C-1 and C-2 at axial and equatorial positions. A similar structure was found for 5 with the difference that bridging C-1 and C-2 there is a dioxolane ring. The boron atoms are planar with their attached atoms, stabilized by retrocoordination between the boron and oxygen and carbon atoms, respectively. The two phenyl rings that are in the same face of the molecule are essentially parallel, with a dihedral angle between planes of 28.26 ± 0.79°.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: This work suggests a theoretical approach for the description of a primary x-ray beam by means of the K fluorescence which it excites on a set of thin targets made of pure elements. Physical quantities, defined as weighted integrals over hv of the photon spectral distribution, are obtained directly as weighted integrals of the Kα yields over the variable Ez (the ionization energy of the K shell of the element with atomic number Z), without needing any explicit reconstruction of the spectral distribution. The set of Kα yields produced by an x-ray beam as a function of Ez is a functional description of the exciting beam. Theoretically, such a description is suited to x-ray fluorescence analysis.
    Additional Material: 2 Ill.
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  • 5
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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  • 6
    ISSN: 0749-1581
    Keywords: 1H, 13C, 15N and 113Cd NMR ; Two-dimensional NMR ; CP/MAS NMR ; Hg and Cd complexes 4(1H) -Quinazolinone-2,3-dihydro-2-thioxo ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Cd(II) and Hg(II) complexes of 4(1H)-quinazolinone-2,3-dihydro-2-thioxo (1) and the free ligand were studied by 1D and 2D multinuclear magnetic resonance in solution and 13C cross polarization magic angle spinning NMR in the solid state. Compound 1 adopts only one of five possible tautomeric structures in solution, namely the thiouracyl-like structure. It was found that the metal atom is linked to two molecules of deprotonated 1 by N-1 and coordinated by the sulphur atom. The compounds retain the same structure in the solid state and in dimethyl sulphoxide solution.
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 41 (1994), S. 487-493 
    ISSN: 1432-0614
    Keywords: Limonin ; Debittering ; Immobilization ; Rhodococcus fascians ; Continuous Stirred Tank ; Reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Limonin can be effectively degraded byRhodococcus fascians cells. These bacteria can be entraped in κ-carrageenan, and used in a continuous stirred tank reactor to degrade limonin in a continuous process. The effects of temperature limonin concentration, dilution rate, and aeration on the reactor behaviour have been tested, and the results correlated with changes in limonin conversion, substrate degradation rate, and free and immobilized biomass. Results showed that the immobilized cells were able to debitter limonin-containing media and the immobilized biomass was quite stable throughout the operational conditions tested. A population of free biomass was present in the reactor, the quantity of which was dependent on dilution rate. The immobilized bacteria increased its limonin-degrading capability when the substrate concentration was increased. The aeration was not strictly necessary for limonin degradation. Additionally, the immobilized cells were active and stable for more than 2 months of continuous operation, and were able to recover their limonin-degrading capability when used intermittently. Finally, none of the main components of a juice was noticeably altered during limonin degradation, so the reactor response was good enough to consider its application.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 41 (1994), S. 487-493 
    ISSN: 1432-0614
    Keywords: Limonin ; Debittering ; Immobilization ; Rhodococcus fascians ; Continuous Stirred Tank ; Reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Limonin can be effectively degraded byRhodococcus fascians cells. These bacteria can be entraped in κ-carrageenan, and used in a continuous stirred tank reactor to degrade limonin in a continuous process. The effects of temperature limonin concentration, dilution rate, and aeration on the reactor behaviour have been tested, and the results correlated with changes in limonin conversion, substrate degradation rate, and free and immobilized biomass. Results showed that the immobilized cells were able to debitter limonin-containing media and the immobilized biomass was quite stable throughout the operational conditions tested. A population of free biomass was present in the reactor, the quantity of which was dependent on dilution rate. The immobilized bacteria increased its limonin-degrading capability when the substrate concentration was increased. The aeration was not strictly necessary for limonin degradation. Additionally, the immobilized cells were active and stable for more than 2 months of continuous operation, and were able to recover their limonin-degrading capability when used intermittently. Finally, none of the main components of a juice was noticeably altered during limonin degradation, so the reactor response was good enough to consider its application.
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  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 495-503 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High strength alumina fibers were fabricated with a polymer precursor process which was monitored with 13C-NMR, elemental analysis, gas evolution, SEM, and X-ray diffraction. Methylaluminoxane was chain extended by reaction with H2O, the unreacted methyl groups were converted to propanoyloxyl and i-propanoyl groups in molar ratios of 0.2 : 0.8 to 0.4 : 0.6 to afford spinning dope of adequate fluidity which can be spun into filaments with suitable stability. These precursor fibers were hydrolyzed in two stages at ambient temperatures and at 320-350°C, and then calcined at 950°C. The resulting alumina fibers have average tensile strengths up to 1.1 GPa and modulus of greater than 140 GPa.
    Additional Material: 6 Ill.
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  • 10
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleophilic substitution of PVC with sodium thiophenate was carried out in cyclohexanone solution at 5, 25, 40, 60, and 70°C. The initial rate obeys an Arrhenius law from 25 to 60°C, with an activation energy of 70 kJ/mol. Conversion limits are observed which strongly depend on the temperature. The stereoselectivity of the reaction with respect to the configurational triads does not depend on the temperature: the distribution of configurations is only dependent on the conversion. Assuming an SN2 substitution mechanism governed by steric factors, the Monte Carlo simulation procedure described in a prior study is shown to give a good account for all temperatures above 40°C assuming for the mm, mr or rm, and rr triads a reactivity such as Rmm = 2 Rmr and Rrr nil at low temperature and very low at temperatures ≥ 40°C. The low conversion limits observed at 5 and 25°C cannot be explained by a limited accessibility of a part of the polymer. Finally, it is shown that the elimination reaction, which remains limited, does not interfere with the substitution process.
    Additional Material: 8 Ill.
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