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  • 1990-1994  (6)
  • Chemistry  (5)
  • Polymer and Materials Science  (3)
  • Ionized calcium  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Plasma ionized calcium and blood lactate concentrations are inversely associated in human lactic acidosis (1992)
    Springer
    Intensive care medicine 18 (1992), S. 286-289 
    Details
    ISSN: 1432-1238
    Keywords: Ionized calcium ; Hypocalcemia ; Lactate ; Lactic acidosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Plasma ionized calcium [Ca++] concentrations are decreased in patients having lactic acidosis. To further investigate this observation, we prospectively studied nine critically ill patients who had lactic acidosis and measured arterial pH, PCO2, [Ca++], lactate, and albumin concentrations. We found a strong association between decreased [Ca++] and increased plasma lactate concentrations (r 2=0.78,p≤0.001). This unexpected association — [Ca++] usually increases with increasing acidosis — might be clinically important and the mechanism deserves further investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01706475
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Biosurfactants and aqueous two-phase fermentation (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 86-90 
    Details
    ISSN: 0006-3592
    Keywords: aqueous two-phase system ; biosurfactant ; extractive bioconversion ; cell partitioning ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The partition of surfactants and a biosurfactant-producing microorganism was studied in polyethylene glycol and dextran aqueous two-phase systems. In the presence of sodium phosphate, surfactants distributed themselves according to charge. Cationic surfactants preferred the bottom phase, while anionic surfactants were attracted to the top phase. Incresing the phosphate molarity or the pH resulted in a more 1-sided surfactant partitioning. Biosurfactant partitioning was weaker than synthetic surfactant partitioning due to the weaker effective charge and lack to strong specific affinity for any of the phase-forming polymers. Bacillus Subtilis cells partitioned very storngly to the bottom phase. The bioscurfactant, surfactin, produced by this microorganism partitioned to the top phase. Batch fermentations were carried out in an aqueous 2-phase system. Surfactin was produced in larger quanities in the 2-phase fermentation than in the regular mineral salts medium.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400113
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Catalyzed hydrolysis of polyethylene terephthalate melts (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 985-991 
    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 effect of zinc catalysts on the hydrolytic depolymerization of polyethylene terephthalate (PET) melts in excess water was studied using a 2-L stirred pressure reactor at temperatures of 250, 265, and 280°C. The main products of the reaction were found to be terephthalic acid, ethylene glycol, and diethylene glycol. Rate constants were calculated from initial rate data at each temperature and found to be about 20% greater than the corresponding rate constants for uncatalyzed hydrolysis. The catalytic effect of zinc, as well as sodium, salts is attributed to the electrolytic destabilization of the polymer-water interface during hydrolysis. The depolymerization rate data at 265°C were found to fit a kinetic model proposed earlier for the uncatalysed hydrolysis of PET. The effect of zinc and sodium salts on the activation energy of hydrolysis, or on the formation of ethylene glycol monomer is unclear. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530801
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics of glycolysis of poly(ethylene terephthalate) melts (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 1731-1740 
    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 reaction of poly(ethylene terephthalate) (PET) melts with ethylene glycol was examined in a pressure reactor at temperatures above 245°C. The reaction rate was found to depend on temperature and on the concentrations of liquid ethylene glycol and of ethylene diester groups in the polymer. A kinetic model proposed for the initial period of the reaction was found to be consistent with experimental data. It was found that internal catalysis by ethylene glycol does not play an important role in the glycolytic depolymerization of PET. The rate constants for glycolysis were calculated for three different temperatures, yielding an activation energy of 92 kJ/mol. Zinc salts, which have a catalytic effect on glycolysis of PET below 245°C, do not appear to influence glycolysis rates above that temperature. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070541115
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  • 5
    Electronic Resource
    Electronic Resource
    A kinetic study of the hydrolytic degradation of polyethylene terephthalate at high temperatures (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 443-451 
    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 hydrolytic depolymerization of molten PET in excess water was studied using a 2 L stirred pressure reactor at temperatures of 250, 265, and 280°C. Rate constants for hydrolysis are calculated from the initial rate data. At initial water: PET charge ratios (w/w) exceeding 5.1, essentially complete depolymerization to monomer is possible at 265°C. At lower water: PET initial charges, an equilibrium is established. The equilibrium constants are calculated for 2 g water/g PET at three temperatures. A kinetic model is proposed to describe the hydrolysis reaction. The model is shown to fit experimental data and to yield good predictions for the equilibrium concentration of carboxyl groups. Carboxyl-group concentrations are measured using an end-group analysis technique. Potentiometric titrations are carried out in one of two solvent systems, dimethylphenol:chloroform or dimethylsulfoxide, depending on the extent of hydrolysis. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070480309
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanism of production of ions in electrospray mass spectrometry (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 721-728 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mechanism for the production of multiply charged molecular ion species in electrospray mass spectrometry (ES-MS) is still required. A concise discussion of a recently published ionic solution equilibrium model offering a partial mechanism is presented. That publication proposed that the ion abundance-charge profile could be fitted by one or a series of superimposed Gaussian functions, in accord with a solution equilibrium model. It is shown that indeed a simulated mass spectrum based on a solution odel can compare well with the observed spectrum. However, some new and recently published experimental evidence is presented which shows that the ES mass spectra of many proteins give rise to multiply charged molecular ions which carry higher charges than those calculated by the model. Further, the ion abundance-charge profile is very sensitive to some experimental parameters, e.g. cone voltage; it does not necessarily reflect the solution or gaseous ion populations in the mass spectrometer source. Therefore, the concept that gaseous multi-charged ions originate from equivalently charged solvated ions in electrically neutral solution must be treated with caution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280612
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