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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary GC ; Derivatization ; (Chloro)alkyl chloroformates ; Non-aqueous reaction media ; Aqueous reaction media ; Fatty acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fatty acids can be conveniently derivatized in less than one minute with (chloro)alkyl chloroformates such as methyl chloroformate, 2-chloroethyl chloroformate and 2,2,2-trichloroethyl chloroformate. 2,2,2-Trichloroethyl chloroformate is the most reactive reagent, and yields a reaction product which can be sensitively detected by GC ECD (detection limit 50 ng/ml, i.e. 25 pg/injection, for C8, C10, and C12 acids).In non-aqueous media 3-picoline, N-methylpiperidine, and dimethylaminopyridine show catalytic activity comparable with that of pyridine and can, therefore, replace it. N-methylpiperidine is the best basic catalyst in aqueous media (i.e. media containing up to 40 % water).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 503-507 
    ISSN: 0749-1581
    Keywords: 13C NMR ; Triterpene hydrocarbons ; Hopanes ; Revised assignments ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR assignments of ten triterpene hydrocarbons of the hopane group are presented. Assignments for eight of the hydrocarbons are reported for the first time, whilst revisions to the published assignments of hopane and 17 α-hopane are described.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 182-192 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental measurements of the crystal-size distribution (CSD) clearly indicate a pronounced difference in the dynamic behavior of a 20- and 970-L continuous crystallizer that produces ammonium sulfate. The difference in their circulation time offers a probable explanation for this phenomenon. It causes different supersaturation profiles in the two crystallizers, which leads to internal fines dissolution in the large crystallizer. This contributes to the observed oscillations in the 970-L crystallizer as opposed to the first-order responses in the 20-L crystallizer. To numerically study the effect of the supersaturation profile a dynamic model, from which the MSMPR (mixed suspension mixed product removal) assumption is omitted, is developed. Calculated supersaturation profiles differ considerably for the 20-L, the 970-L and an imaginary 50,000-L continuous evaporative crystallizer. Coincident with changes in the supersaturation profiles, the numerical solution of the model indicates the tendency of large crystallizers to oscillate and supports this suggested explanation.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1465-1472 
    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 oxygen and nitrogen permeability coefficients and oxygen/nitrogen selectivities of a series of isophorone-based polyarylates have been measured. The monomeric bisphenols used in this study are easily accessible in two steps from cheap, commercially available, isophorone (3,5,5-trimethyl-2-cyclohexen-1-one). The corresponding polyarylates can easily be prepared in high yield by means of the well-known interfacial polycondensation route. The effect of substituents (CH3, Cl, or Br) on all positions ortho to both hydroxyl groups in the bisphenol and the influence of the terephthalic acid/isophthalic acid molar ratio in the polyarylate on the oxygen/nitrogen separation performance have been studied in detail. It has been found that the polyarylate with four bromine substituents displays a significantly increased oxygen and nitrogen permeability coefficient, combined with a high oxygen/nitrogen selectivity, relative to conventional polyarylates. Obviously, the bulky 3,3,5-trimethylcyclohexylidene moiety in the bisphenol has structural features that hinder an effcient chain packing and reduce polymer segmental mobility. A further improvement in the gas permeability of these polyarylates can be achieved when the bulky t-butyl group is introduced on the 5 position in isophthalic acid. For example, the polyarylate prepared from the isophorone-based bisphenol with four methyl substituents and 5-t-butylisophthalic acid is characterized by an oxygen permeability coefficient of 34.7 Barrer! © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 1429-1440 
    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: Poly(ethylene-2,6-naphthalenedicarboxylate) (PEN) has been prepared from commercial dimethyl-2,6-naphthalenedicarboxylate (DM-2,6-NDC) and ethylene glycol (EG) according to the well-known transesterification/polycondensation route. PEN fibers, intended for industrial yarn applications, were obtained by melt spinning and drawing high molecular weight PEN. The properties of these yarns were measured in detail and compared with those of PET industrial yarns. The development of molecular orientation in the spinline is more pronounced for PEN than for PET. Because the yield stress is lower, PEN yarns can more easily be drawn. Breaking tenacities of PEN yarns are comparable with those of PET yarns, but the modulus is much higher and the thermal shrinkage is lower. Therefore, PEN yarns have a better dimensional stability than PET yarns. In addition, it was demonstrated that the thermal resistance of PEN yarns is better. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electrophoresis 13 (1992), S. 475-483 
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Recent interest in capillary gel electrophoresis has been fueled by the Human Genome Project and other large-scale sequencing projects. Advances in gel polymerization techniques and detector design have enabled sequencing of DNA directly in capillaries. Efforts to exploit this technology have been hampered by problems with the reproducibility and stability of gels. Gel instability manifests itself during electrophoresis as a decrease in the current passing through the capillary under a constant voltage. Upon subsequent microscopic examination, bubbles are often visible at or near the injection (cathodic) end of the capillary gel. Gels have been prepared with the polyacrylamide matrix covalently attached to the silica walls of the capillary. These gels, although more stable, still suffer from problems with bubbles. The use of actual DNA sequencing samples also adversely affects gel stability. We examined the mechanisms underlying these disruptive processes by employing polyacrylamide gel-filled capillaries in which the gel was not attached to the capillary wall. Three sources of gel instability were identified. Bubbles occurring in the absence of sample introduction were attributed to electroosmotic force; replacing the denaturant urea with formamide was shown to reduce the frequency of these bubbles. The slow, steady decline in current through capillary sequencing gels interferes with the ability to detect other gel problems. This phenomenon was shown to be a result of ionic depletion at the gel-liquid interface. The decline was ameliorated by adding denaturant and acrylamide monomers to the buffer reservoirs. Sample-induced problems were shown to be due to the presence of template DNA; elimination of the template allowed sample loading to occur without complications. The improved samples permitted multiple consecutive DNA sequencing runs on the same capillary.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 107 (1995), S. 346-349 
    ISSN: 0044-8249
    Keywords: Helixverbindungen ; Molekulare Schalter ; Optische Datenspeicherung ; Thioxanthene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0570-0833
    Keywords: helices ; molecular switches ; optical data storage ; thioxanthenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1945-1951 
    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: A new amorphous heat-resistant aromatic polyamide was prepared by solution polymer-ization in N-methylpyrrolidone, (NMP) from equimolar amounts of 4,4′-methylenedianiline, p-phenylenediamine, isophthaloyl chloride, and terephthaloyl chloride. After neutralization of the byproduct HCl, with calcium hydroxide, the as-polymerized polymer solution (15.7% polyamide in NMP) was spun directly on a horizontal wet-spinning device. Yarn drawing of as-spun fibers, near the glass transition temperature of the polymer, was performed on a hot-drawing equipment. To determine the optimal drawing conditions, the influence of the draw ratio on the tensile properties was studied in detail. On the basis of these results, a draw ratio of 1.7 was applied to prepare a larger quantity of drawn polyamide multifilament yarn (f330 and f500). Tensile properties of both fibers and filaments were determined by standard methods. The fibers are characterized by an excellent thermal stability as indicated by temperature-dependent tensile measurements, long-term heat resistance, boiling-water shrinkage, hot-air shrinkage, etc., of the fibers. Despite the amorphous character of the polyamide fiber, it offers an excellent resistance to common organic solvents (except to THF and DMF). Moreover, the fiber exhibits a good resistance toward diluted inorganic acids, salts, and bases. Depending on the specific properties of the polyamide fiber, the material may find applications in, e. g., hot-air filter fabrics, protective clothing, electrical insulation paper, or advanced structural materials. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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