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  • Chemistry  (17)
  • 2,4-D adsorption  (1)
  • 2.virialcoef.  (1)
  • 1990-1994  (15)
  • 1980-1984  (4)
  • 1991  (5)
  • 1990  (10)
  • 1984  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Ultracentrifuge studies on the interaction of some basic polypeptides with water-structure influencing anions (1990)
    Springer
    Colloid & polymer science 268 (1990), S. 1141-1147 
    Details
    ISSN: 1435-1536
    Keywords: Ultracentrifuge ; sedimentation-equilibriumrun ; poly-L-lysine ; N ε -methylated-poly-L-lysine ; anions ; molecularweight ; 2.virialcoef. ; part.specvolume andassociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The aim of this work is to investigate the dependence of the molecular weight and the 2. virial coefficient of poly-L-lysine and N ε -methylated poly-L-lysine in solutions of water-structure-influencing anions. In the case of poly-L-lysine, the ultracentrifugal and CD-spectroscopic measurements show an increasing molecular weight and a complex between poly-L-lysine and the strong-water-structure-breaking anion ClO 4 − . In solutions of structure-forming anions, an independence of the molecular weight from the anion-concentration can be recognized. The 2. virial coefficient of structure-breaking anions is generally higher than for structure-forming anions. At a pH of 10.6, the molecular weight and the 2. virial coefficient is independent of the structure-breaking anion. In NaCH3 SO4 solutions, the tendency of the anion concentration and the molecular weight are parallel. Compared to this behavior, N ε -methylated poly-L-lysine was likewise investigated; it shows a similar trend of the molecular weight in dependence of the NaCH3 SO4 concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410679
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  • 2
    Electronic Resource
    Electronic Resource
    Assessment of the changes of 2,4-dichlorophenoxyacetic acid concentrations in plant tissue culture media in the presence of activated charcoal (1990)
    Springer
    Plant cell, tissue and organ culture 20 (1990), S. 165-172 
    Details
    ISSN: 1573-5044
    Keywords: activated charcoal ; 2,4-D adsorption ; coconut palm ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rate of adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) by activated charcoal (AC) from liquid and semi-solid tissue culture media was determined using 2-[14C]-2′,4′-D. In liquid medium 99.5% of the added 2,4-D (10-4 M) was adsorbed by AC (2.5 gl-1) within 5 days of preparation of the medium. Higher 2,4-D levels of reduced AC concentrations increased the level of available 2,4-D in the medium and extended the period necessary for the level of 2,4-D in the medium to become stabilized. In semi-solid medium the rate of adsorption of 2,4-D by AC was considerably reduced. A stable ratio of gel/2,4-D:AC/2,4-D was only reached after 10 to 20 days, depending on the 2,4-D concentration used. Low pH levels and maintenance of the medium at higher temperatures (20–30°C) accelerated the adsorption of 2,4-D by AC. In vitro tissue cultures of coconut palm showed marked differences in their growth response according to the age of the medium used and the associated variations in 2,4-D concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041877
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  • 3
    Electronic Resource
    Electronic Resource
    On the kinetics and mechanism of thermal degradation of polystyrene, 2.Part 1: cf.1. Formation of volatile compounds (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 991-1001 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal degradation of polystyrene (PS) was carried out in the absence of oxygen between 292 and 336°C. The formed volatile products were analysed qualitatively and quantitatively by means of gas charomatography. It was found that the composition of the volatile fraction is a function of conversion and independent of temperature for most of the products. A radical chain mechanism is proposed to explain these experimental results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850513
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  • 4
    Electronic Resource
    Electronic Resource
    Elastic and quasielastic light scattering studies on the branching characteristics of dextrans (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 2205-2212 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of branching on the radius of gyration and the hydrodynamic radius of dextran macromolecules was studied by elastic and quasielastic light scattering (ELS and QELS). The hydrodynamic radius is more sensitive to low levels of branching than the radius of gyration. At higher branching levels a saturation of the hydrodynamic radius rh is observed, while the radius of gyration rG still changes distinctly. The ratio rG/rh proves to be a measure of the flexibility of the macromolecules; the latter is increasing with molecular weight for short linear chains and is decreasing with increasing degree of branching. Measurements were carried out in water (thermodynamically good solvent) and in ethylene glycol (under theta conditions) on four series of dextran fractions having rather narrow molecular weight distributions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021851015
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  • 5
    Electronic Resource
    Electronic Resource
    13C NMR spectroscopic studies on polyanion-polycation complexes and their component polyelectrolytes (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 651-658 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Position and intensities of the 13C NMR signals and relaxation times T1 of several anionic and cationic polyelectrolytes in the solid state were compared with those of the appropriate polyanion-polycation complexes. At a high charge density of the components, the most significant changes of the parameters in question due to complex formation are observed for the C atoms adjacent to the charge centers, indicating a strong Coulombic interaction. At lower charge density, conformational changes of the polymer chains have also to be taken into consideration.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910320
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  • 6
    Electronic Resource
    Electronic Resource
    Chemometric optimization of an asymmetric reduction catalyzed by baker's yeast (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 928-934 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The stereoselective reduction of ethyl acetoacetate to (+)-(S)-ethyl 3-hydroxybutyrate catalyzed by Saccharomyces cerevisiae was optimized by means of chemometric methods. The quantitative effects of temperature, time of incubation, and concentrations of yeast and substrate on the optical purity and on the percent of reduced substrate were investigated using a factorial design at two levels. This approach gave information about the chemical behavior of the catalyst. The variability of the two responses was expressed by means of their corresponding response surfaces. Use of desirability functions allowed the overall optimization of the process, also taking into account the importance of economic factors. The investigation showed that it is possible to reduce the substrate completely obtaining (+)-(S)-ethyl 3-hydroxybutyrate with percent of enantiomeric excess〉98% and, at the same time, to operate in more convenient experimental conditions than those previously reported.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350910
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal decomposition of 2, 3-dimethyl butane: Experiments and mechanistic modelling (1990)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 13 (1990), S. 241-251 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pyrolysis of 2,3-dimethyl butane (DMB) was carried out in a quartz flow reactor in the temperature range from 740 to 1032 K at normal pressure. The input concentration of DMB was 3.3 × 10-3 mol/1 using argon as diluent. Reaction time ranged between 3.1 and 3.9 s. The following products were analyzed by two-column gas chromatography: hydrogen, methane, ethene, propane, propene, butenes, butadiene, 2-methyl-2-butene, isoprene, benzene and toluene. Compared to thermal decomposition of n-hexane under similar experimental conditions, the main difference concerned the formation of ethylene, ethane and branched alkanes. A reaction model, based on elementary reactions, was developed to predict the experimental results and to verify our data basis of elementary reactions under different conditions. The model gives a quantitative description of the complex chemistry of the process. In addition, an algorithm is presented for model reduction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270130133
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  • 8
    Electronic Resource
    Electronic Resource
    Design Data for Cyclones (1991)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 301-307 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For many years efforts have been made to describe the complex process of particle separation in cyclones, and a multitude of separation models have been set up. A comparison of such separation models fails because insufficient usable test results are available and systematic and precise investigations are missing.It is important for the design of cyclones to rate their separation properties by means of the fractional collection efficiency. On account of the known measuring problems, the data supply of reliable fractional efficiency curves of cyclones is still too small. Fractional efficiency as a function of the entrance velocity was measured with a high-speed optical measuring technique. Measurements of low dust concentrations are presented. Geometrically similar cyclones of four different sizes were investigated. The fractional efficiency curves are plotted versus dimensionless parameters and the validity of the design criteria gained in this way is shown. The influence of particle shape on the fractional efficiency curves is discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19910080155
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  • 9
    Electronic Resource
    Electronic Resource
    Electrochemical impedance spectroscopy of oxygen and hydrogen evolution on amorphous alloys in 1 M KOHDedicated to Professor Dr. Dr. hc. Dieter Behrens on the occasion of his 65th birthday (1991)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 263-269 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mechanisms of oxygen and hydrogen evolution on amorphous alloys G 14 (Fe60Co20Si10B10) and G 16 (Co50Ni25Si15B10) in 1 M KOH at T = 298 K and 333 K were studied by electrochemical impedance spectroscopy (EIS). Comparative measurements were carried out on polycrystalline Pt electrodes. Impedance spectra in the frequency range 10-3 Hz ≤ f ≤ 104 Hz were analyzed to determine the kinetic behaviour of amorphous alloys by application of transfer function analysis, using non-linear fit routines. The EIS-data are interpreted in terms of consecutive reaction mechanisms for both oxygen and hydrogen evolution.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270140408
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  • 10
    Electronic Resource
    Electronic Resource
    Induction and variation of discotic columnar phases through doping with electron acceptors (1990)
    Weinheim : Wiley-Blackwell
    Advanced Materials 2 (1990), S. 141-144 
    Details
    ISSN: 0935-9648
    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: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19900020306
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