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  • Polymer and Materials Science  (180)
  • Life and Medical Sciences  (74)
  • thema EDItEUR::D Biography, Literature and Literary studies::D Biography, Literature and Literary studies::DN Biography and non-fiction prose  (26)
  • Inorganic Chemistry  (18)
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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 2815-2819 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two different ways of analyzing the composition of insoluble, partly hydrogenated, partly fluorinated copolymers by NMR are described. The first relies on a quantitative comparison of 1H and 19F free induction decays, as observed in the solid state, with those of reference samples. The second relies on medium resolution spectra which can be achieved, thanks to the large scale of 19F chemical shifts, on softening of the samples at high temperature. A special probe working up to 400°C was built for this purpose. The two methods are in good agreement in the case of vinylidene fluoride (VF2)/tetrafluoroethylene (VF4) copolymers, leading to a determination of the rectivity ratios; the special usefulness of the second method is illustrated by the identification of a third comonomer in VF2/VF4 terpolymers.
    Additional Material: 5 Ill.
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  • 2
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a sensitive birefringence instrument, the birefringence arising from the orientation of the DNA chain during electrophoretic transport has been recorded. This birefringence is shown to proceed both from the alignment (stretching) of the molecule in the direction of the electric field and from the extension of the length of its primitive path (overstretching). The contribution of these two processes can be separated in the decay of the birefringence after the end of the application of the electric field. The fast relaxation of the overstretching occurs first and is demonstrated to be the main contribution to the birefringence. The orientation factor of the remaining stretched state and its decay can be quantitatively understood using the biased reptation model. It provides, in addition, a high value for the tube diameter or gel pore size a (4500 ± 450 Å for a 0.7% agarose gel with a c-0.6g dependence in the agarose concentration cg) and a low value for the effective charge per base pair (0.2e as compared to 0.5e using the condensation hypothesis). The contribution of overstretching to the birefringence is also quantitatively interpreted in term of the change in the mean length l of DNA inside a pore size a. The dynamics of decay of this overstretching is well represented by a stretched exponential with a stretching exponent α = 0.44. The mean decay time decreases slightly with increasing fields and scales with the overall DNA length close to N20. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 177-189 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von CO2-Laserstrahlung auf die Oberflächeneigenschaften eines Epoxid-Laminierharzes (wärmebeständig bis 120°C) für kohlefaserverstärkte Kunststoffe (CFK) wird untersucht. Infrarot- und XPS-Spektroskopie zeigen, daß die Hydroxygruppen des Harzes unter Bildung von Doppelbindungen eliminiert werden. In Kohlendioxidatmosphäre werden tiefer liegende Teile des Harzes modifiziert als bei der Behandlung in Luft. Eine Steigerung der Reproduzierbarkeit der Klebfestigkeit des verwendeten CFK auf Basis des untersuchten Harzes ist nur bei gleichzeitiger Verringerung der Klebfestigkeit selbst möglich. Beim Einsatz eines heißhärtenden Klebstoffes kann kein Einfluß der Laserbehandlung auf die Klebfestigkeit festgestellt werden.
    Notes: The influence of CO2 laser radiation on the surface properties of a lamination resin (temperature resistant up to 120°C) which is used for carbon fibre-reinforced plastics (CFRP) is examined. It is shown by XPS and infrared spectroscopy that the hydroxy groups of the resin are eliminated by the laser radiation. Using a carbon dioxide atmosphere, also deeper parts of the resin are influenced compared to the treatment in air. The reproducibility of the bond strength is higher for the laser-treated samples than for untreated samples if a room temperature-curing adhesive is used, but the bond strength itself is lower. Laser treatment shows no influence at all if a hot-curing adhesive is used.
    Additional Material: 5 Ill.
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolymers of benzylaspartate with the corresponding para-nitro and ortho-nitro derivatives are known to undergo, at increasing nitro content, a transition from a left-handed α-helical conformation to a right-handed α-helical conformation. The circular dichroism associated with the n, π* transition of the amide group, as well as the extrinsic bands associated with the nitrobenzyl chromophore, have been studied for these copolymers as a function of the nitro content. The circular dichroism associated with the 330-nm extrinsic band is shown to present an abrupt change, which parallels the change in the 222-nm band characteristic of the left- to right-handed helix transition. The intensity of the 222-nm CD band seems unaffected by the interaction with the side-band chromophore. The circular dichroism associated with the 330-nm band is much stronger in the right-handed conformation and is unaffected by increasing interactions between side chains. Interpretation in the light of the possible mechanism for optical activity of helical molecules seems to indicate that the 330-nm extrinsic effect is essentially due to the Condon, Altar, and Eyring (CAE) mechanism and μ-m perturbation (in Schellmann terminology) on the side-chain chromophore n, π* transition.
    Additional Material: 9 Ill.
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rise of the birefringence following the application of an electric field to DNA in an agarose gel has been quantitatively analyzed to demonstrate the major role played by the chain overstretching. By analyzing the field free decay after short times, we demonstrate that the overshoot is completely due to overstretching. Its time of appearance τov varies with the field and DNA length in fair agreement with the E-lN0ln N0 prediction of Lim et al. [ (1990), Journal of Chemical Physics, Vol. 92, pp. 709-721]. The τov is also the time corresponding to one tube renewal after relaxation of the overstretching. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Condensed Isoquinolines, III. Studies on the Reactivity of s-Triazolo[3.4-a]isoquinolinesHMO-Calculations of s-triazolo[3.4-a]isoquinoline (1) reveal a high doublebond character of the C-5/C-6 bond. Halogenaddition, catalytic hydrogenation and oxidation reactions are in experimental agreement. It appears from oxidation reactions of derivatives of 1 that unsaturated side chains are also oxidatively degradated at the same time under the same conditions.
    Notes: Aus HMO-Berechnungen des s-Triazolo[3.4-a]isochinolins (1) geht u. a. ein hoher Doppelbindungscharakter der C-5/C-6-Bindung hervor, was auch experimentell bei Halogenaddition, katalytischer Hydrierung und Permanganat-Oxydation beobachtet wird. Oxydationsreaktionen der Derivate von 1 zeigen, daß ungesättigte Seitenketten unter gleichen Bedingungen gleichzeitig oxydativ abgebaut werden.
    Additional Material: 8 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1726-1747 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions with Diazoazoles, VII. 3H-Azolo-1,2,4-triazoles by 1,8- or 1,12-Electrocyclizations of 3H-Pyrazol-3-one- or 3H-Indazol-3-one (Diorganylmethylene)hydrazones, Respectively3H-Azolo-1,2,4-triazoles 3 are formed by cycloreactions 2b) of diazoazoles 1 with diazoalkanes 2 and with fluorene--N-, P-, S-ylides 4, respectively, (Method A) or by cyclizing dehydrogenation of diorganylmethanone (1H-azol-3-yl)hydrazones 7 (Method B). In both methods the anellation of the triazol system results from 1,8- or 1,12-electrocyclization of azol-3-one (diorganylmethylene)-hydrazones (azines) 9, as could be shown in the case of the 4-nitrophenyl compound 9dk. - Spectroscopic data (UV, 1H NMR, 13C NMR) of the 3H-azolo-1,2,4-triazoles 3 are discussed.
    Notes: 3H-Azolo-1,2,4-triazole 3 entstehen durch Cycloreaktion2b) von Diazoazolen 1 mit Diazoalkanen 2 bzw. mit Fluoren-N-, P-, S-Yliden 4 (Methode A) oder durch cyclisierende Dehydrierung von Diorganylmethanon-(1H-azol-3-yl)hydrazonen 7 (Methode B). Bei beiden Methoden erfolgt die Triazolanellierung durch 1,8- bzw. 1,12-Elektrocyclisierung von Azol-3-on-(diorganylmethylen)-hydrazonen (Azine) 9, wie im Fall der 4-Nitrophenylverbindung 9dk gezeigt werden konnte. - Spektroskopische Daten (UV, 1H-NMR, 13C-NMR) der 3H-Azolo-1,2,4-triazole 3 werden diskutiert.
    Additional Material: 7 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1375-1395 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions with Diazoazoles, VIII1). - Syntheses of Azolo [5,1-d]-1,2,3,5,-tetrazin-4(3H-onesAzolo[5,1-d]-1,2,3,5-tetrazin-4(3H)-ones 4 and 5 are formed by cycloaddition reactions of α-diazoazoles 2 with aryl or alkyl isocyanates 3a-p, respectively, as well as with diisocyanates 3q, r (Method A). Alternative syntheses for 4 are presented by diazotization of N-alkyl(aryl)-5-amino-1H-pyrazole-1-carboxamides (6) and subsequent intramolecular coupling (Method B), by coupling of 3-diazo-5-methyl-4-phenyl-3H-pyrazole (2A) with primary amines 11 to give pyrazolyltriazenes 12A, and by their carbonylation reaction (Method C). The lability of azolotetrazinones against bases is exemplified with-methyl-3,8-diphenylpyrazolo-[5,1-d]-1,2,3,5-tetrazine-4(3H)-one (4Aa) in its reaction with hydroxide ions or morpholine.
    Notes: Azolo[5,1-d]-1,2,3,5-tetrazin-4(3H)-one 4 und 5 entstehen durch Cycloaddition von α-Diazoazolen 2 an Aryl- oder Alkylisocyanate 3a-p bzw. an Diisocyanate 3q, r (Methode A). Alternativsynthesen für 4 werden durch Diazotierung von N-Alkyl(Aryl)-5-amino-1H-pyrazol-1-carboxamiden 6 und nachfolgende intramolekulare Kupplung (Methode B) sowie durch Kupplung von 3-Diazo-5-methyl-4-phenyl-3H-pyrazol (2A) mit primären Aminen 11 zu Pyrazolyltriazenen 12A und deren Carbonylierung (Methode C) vorgestellt. Die Basenlabilität der Azolotetrazinone wird am Beispiel des 7-Methyl-3,8-diphenylpyrazolo[5,1-d]-1,2,3,5-tetrazin-4(3H)-ons (4Aa) in dessen Reaktion mit Hydroxidionen oder Morpholin aufgezeigt.
    Additional Material: 9 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 145-149 
    ISSN: 0009-2940
    Keywords: Cycloalkenes, 1-methyl- ; Ozonolysis ; Peroxyhemiacetals, cyclic ; Rubber, natural ; Tetrahydrofurans, 2-hydroperoxy- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ozonolyses of 1-Methylcyclopentene, 1-Methylcyclobutene, 5-Hexen-2-one and Natural Rubber in the Presence of MethanolOzonolyses of 1-methylcyclopentene (8a) and of 1-methylcyclobutene (8b) in methanol proceeded in each case in the two possible directions. The resulting methoxyperoxides 13 and 14 afforded the corresponding peroxyhemiacetals 15 and 19 by intramolecular reactions of the OOH with the corresponding carbonyl groups. Ozonolysis of 1-methylcyclobutene (8b) additionally gave the corresponding ozonide 17b and 2-hydroperoxy-5-methoxy-2-methyl-as well as 5-hydroperoxy-2-methoxy-2-methyltetrahydrofuran (16b and 18b). The mode of formation of these hydroperoxy compounds has been elucidated by ozonolyses of 5-hexen-2-one (25) and of natural rubber (28) in the presence of methanol.
    Notes: Ozonolysen von 1-Methylcyclopenten (8a) und von 1-Methylcyclobuten (8b) in Methanol verliefen jeweils nach beiden möglichen Spaltungsrichtungen. Die dabei gebildeten Methoxyhydroperoxide 13 und 14 ergaben durch intramolekulare Reaktionen der OOH- mit den Carbonylgruppen die entsprechenden Peroxyhalbacetale 15 bzw. 19. Bei der Ozonolyse von 1-Methylcyclobuten (8b) wurden zusätzlich das entsprechende Ozonid 17b sowie 2-Hydroperoxy-5-methoxy-2-methyl- und 5-Hydroperoxy-2-methoxy-2-methyltetrahydrofuran (16b und 18b) gebildet. Die Bildungsweise dieser Hydroperoxy-Verbindungen wurde durch Ozonolysen von 5-Hexen-2-on (25) und von Naturkautschuk (28) im Beisein von Methanol aufgeklärt.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 455-458 
    ISSN: 0009-2940
    Keywords: N-Boryl lactams / Isourea, triborated / Isothiourea, triborated /N/O Borotropism / Calculations, MNDO ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contribution to the Chemistry of Boron, 201. - Boration of Lactams and Ureas by an Amino-Imino-BoranePyrrolidon reacts with (tert-butylimino)(2,2,6,6-tetramethylpiperidino)borane (1) to give the N-borated lactam 2. Diketopiperazine behaves similarly. It is borated on both of its N atoms to form 3. Urea and 1 give access to the O,N,N′-triborated isourea derivative 4, which contains the structural unit of a ketiminoborane. The diborated carbodiimide 10 is ultimately obtained from 1 and thiourea via the triborated isothiourea derivative 9. MNDO calculations have been used to estimate the relative thermodynamic stabilities of O/N borotropes of carbonic acid amides and lactams. They demonstrate that the O isomers gain in stability by increasing the size of N substituents.
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