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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 923-934 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have determined extinction angles and flow birefringence of T7 bacteriophage DNA over a wide range of shear, polymer concentration, and solvent ionic strength. From these data, information on the simple salt dependence of coil permeability to solvent and on short-range intrachain interactions (persistence length) was obtained. At all ionic strengths, our results are consistent with a partially draining coil in the Gaussian subchain dynamical theory of Rouse-Zimm-Tschoegl-Bloomfield. Salt dependence of persistence length is comparable to, although somewhat less than, that obtained previously using similar methods with a fivefold higher-molecular-weight DNA (T2 bacteriophage DNA). Possible reasons for observed discrepancies are analyzed, and the results of this work are compared in detail to other current studies of solvent ionic strength dependence in persistence length and hydrodynamic properties of DNA.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1807-1823 
    ISSN: 0887-624X
    Keywords: polyacrylamide ; thermal analysis ; thermogravimetry ; evolved gas analysis ; infrared ; mass spectrometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dried samples of polyacrylamide in an He atmosphere have been subjected to thermogravimetric analysis in the 30-600°C range, and the evolved gases were monitored by FTIR. Water, ammonia, and small quantities of carbon dioxide are released in the first stages of decomposition (220-340°C), where the polymer chains remain intact and the reaction occurs on the pendant amide groups. In the second stage of decomposition (340-440°C), the majority of the weight loss occurs, and main chain breakdown occurs, releasing carbon dioxide, water, nitrile compounds, and imides. Trapping of the gases in this stage and analysis by GC-FTIR and GC-MS reveals the presence of more than 20 decomposition products, and confirms that a large proportion of these can be assigned to glutarimide and its substituted analogs. Imidization and dehydration reactions on the amide groups, as well as free radical breakdown of the main chains, with inter- and intramolecular hydrogen transfer, can account for many of the products of the decomposition. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 279-283 
    ISSN: 1040-0397
    Keywords: Chemical oxygen demand ; Coulometry ; Chromium ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical oxygen demand (COD) of solutions containing various organic compounds is calculated from the net faradaic charge (Qnet) estimated for the total electrolytic oxidation of CrIII generated during oxidative degradation of the organic compounds in acidic media containing excess CrVI. Values of Qnet for conversion of CrIII to CrVI are estimated from the linearized chronoamperometric data plotted as In {itat, t} vs. t. This procedure is preferred over determinations of Qnet from the total integrals of itot over the entire electrolysis period because of large errors that can result from uncertainty in the background current (ibkg) for t → ∞. The proposed coulometric procedure offers the benefit that reagent solutions can be reused, thereby minimizing the need for disposal of wastes containing toxic CrVI. This procedure was applied in a single digest solution for consecutive determinations of COD. Average COD values for potassium acid phthalate and glucose were 103.8% (s - 6.0, N - 10) and 100.2% (s - 4.2, N - 11), respectively, based on the theoretical degradation to CO2. In comparison for these same samples, an EPA approved method, based on colorimetric determination of CrIII, gave COD values of 101.4% (S - 1.4, N - 5) and 100.1% (s - 1.4, N - 5) of the theoretical. Statistical tests indicate no significant difference in the COD values determined for these compounds using the coulometric and EPA methods.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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