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  • 1
    ISSN: 0749-1581
    Keywords: Chalcone oxides ; Absolute configuration ; Lanthanide-induced shifts ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absolute configuration of an unknown 2′- or 4- and (or) 4′ phenyl-substituted chalcone oxide can be predicted from the chemical shift behaviour of the 1H NMR spectrum of the substrate in the presence of the lanthanide chiral complex Eu(hfbc)3.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Homogeneous films of poly(1,4-phenylene) (PPP) can be deposited on various materials by electro-reduction of 4,4′-dibromobiphenyl in presence of a nickel complex catalyst. UV and IR spectra indicate that the polymer has a regular structure (exclusively 1,4-phenylene units) and an unusual average molecular weight. The nascent PPP films are obtained in their neutral from and can be either reduced or oxidized.
    Additional Material: 4 Ill.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New methacrylic copolymers with prospective second-order nonlinear optical effects are synthesized by radical copolymerization of methyl methacrylate with conjugated zwitterionic methacrylate monomers (2,6-di-tert-butyl-4-[1-(ω-methacryloyloxyalkyl)-4-pyridino]phenolates,1a and 1b). These monomers are obtained via a multi-step reaction. First, 4-(3,5-di-tert-butyl-4-hydroxyphenyl)pyridine (2) is electrosynthesized by an SRN1 reaction in liquid ammonia. Then, this pyridine derivative is N-alkylated by an ω-bromoalkyl methacrylate (5a or 5b) which, in its turn, is obtained by esterification of an ω-bromoalcohol and methacryloyl chloride.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Conjugated polymers were prepared by electroreduction of aryl dihalides in presence of nickel complexes as catalysts. For instance, poly(1,4-phenylene) was obtained from 4,4′-dibromobiphenyl in high yield (85%). According to the coupling mechanism and to IR spectra, the chains of the polymer are expected to have regular para-linkages and an average length ranging from 6 to 18 phenylene units. The effects of temperature, nature of monomer, catalyst and electrolyte on the yields and on the properties of the polymer were explored.
    Additional Material: 1 Ill.
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 4-Methylstyrene (S) was copolymerized with methyl methacrylate (M) or acrylonitrile (A) in benzene or N,N-dimethylformamide solution, respectively. The reactions were carried out at 50°C, using 2,2′-azoisobutyronitrile as free-radical initiator. The copolymer compositions were determined from oxygen (SM) or nitrogen (SA) analysis, 100 MHz 1H NMR, and 25 MHz 13C NMR spectra. These methods lead to the same results. Data plotted according to the Kelen-Tüdős (K-T) procedure indicate that the copolymerization of S with M can be adequately described by the terminal-unit model. The corresponding reactivity ratios (rS = 0,46 ± 0,02 and rM = 0,35 ± 0,02) were in good agreement with literature values and conform with the Q, e-scheme. On the other hand, the K-T plot for copolymerization of the SA system indicates deviations from the terminal model (rS = 0,27 ± 0,02 and rA = 0,10 ± 0,01) in the S- and A-rich regions. This departure was interpreted in terms of penultimate effects on the reactivity of the S- and A-ended radicals. The values of the corresponding reactivity ratios were as follows: rSS = 0,18 ± 0,03, rAS = 0,34 ± 0,04, rAA = 0,06 ± 0,01, and rSA = 0,13 ± 0,01. The theoretical curve of copolymer composition versus monomer feed, calculated with these parameters, is in excellent agreement with the experimental data. This finding shows that, on the basis of the composition data alone, the penultimate model provides an appropriate description of the copolymerization of S and A.
    Additional Material: 8 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The kinetics of acetalization of polyvinl alcohol with acetaldehyde has been examined in water-dioxane solution at different temperatures in the presence of sulfuric acid as catalyst. The reaction is first order with respect to the concentration of acid and of acetaldehyde. With respect to the concentration of alcohol, it is only first order in N/2 sulfuric acid solution; in more diluted acid (f.e. N/200) the order of reaction varies on account of the association phenomena in these solutions. The energy of activation in N/2 and N/200 sulfuric acid is respectively equal to 9.5 Kcal. and 15 Kcal.; this difference is interpreted by the association of the hydroxyl groups with each other. The kinetics of the reverse reaction has also been examined on the basis of four acetalized polyvinyl alcohol different in their acetal content (10, 20, 27, and 51 %). While in N/2 acid solution the rate of hydrolysis is proportional to the concentration of acetal and independent of the concentration of alcohol, the kinetics are much more complicated in more diluted acid solutions, and may be summarized as follows: (1) the rate of hydrolysis decreases with an increase of concentration for a same polymer; (2) at a same molar concentration of acetal, the hydrolysis proceeds most rapidly for the copolymer with the highest alcohol content; (3) the addition of pure polyvinyl alcohal increases considerably the rate of hydrolysis.In order to interprete these data, a catalytic effect of the alcohol group directly neighbouring the acetal group has been admitted, in agreement with the hypothesis of SAKURADA for the hydrolysis of polyvinyl acetate. The energy of activation of hydrolysis is equal to 15.8 and 12 Kcal. in N/200 and N/2 sulfuric acid solutions respectively.
    Notes: La cinétique d'acétalisation de l'alcool polyvinylique au moyen d'acétaldéhyde a été étudiée en soulution dioxanne-eau à différentes températures en présence d'acide sulfurique comme catalyseur.L'ordre de la réaction est unitaire par rapport à la concentration en acide et en acétaldéhyde. Par rapport à la concentration en alcool, il est uniquement unitaire en présence d'acide sulfurique N/2; en solution acide plus diluée (tel N/200) I'ordre est variable par suite des phénomènes d'association au sein de ces solutions. L'énergie d'activation en milieu N/2 et N/200 d'acide sulfurique s'élève respectivement à 9,5 Kcal. et 15 Kcal.; la différence peut s'interprèter à nouveau par I'association considérable des groupes hydroxyles entre eux.La cinétique da la réaction inverse a également été étudiée au départ de quatre alcools polyvinyliques acélisés à des taux différents (10, 20, 27 et 51%). Alors qu'en milieu acide N/2, la vitesse d'hydrolyse est proportionelle à la concentration en acétal, et est indépendante de la concentration en alcool, la cinétique en milieu acide dilué est beaucoup plus complexe.Elle peut se caractériser par les points suivants:(1) La vitesse d'hydrolyse décroît avec une augmentation de concentration pour un même polymère. (2) A concentration égale en acétal l'hydrolyse est la plus rapide pour le copolymère le plus riche au fonction alcool. (3) L'addition d'alcool polyvinylique pur à la solution accroît considérablement la vitesse d'hydrolyse. En vue d'interpréter ces données, on admet une influence catalytique favorable due au groupe alcoolique directement voisin da la fonction acétalique, en accord avec I'hypothèse de SAKURADA dans le cas de l'hydrolyse de l'acétate de polyvinyle. L'énergie d'activation d'hydrolyse s'élève à 15.8 et 12 Kcal. suivant que la solution était respectivement N/200 et N/2 en acide sulfurique.
    Additional Material: 4 Ill.
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  • 7
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An in vitro study was performed to evaluate the effect of Staphylococcus aureus and Staphylococcus epidermidis on the integrity of a hydroxylapatite coating. The coating plasmasprayed on poly(L-lactide), showed dissolution during a 24 h incubation period. This was indicated by an increase in pH and calcium release in the buffer solution., After 4 h of incubation, calcium levels decreased due to the precipitation of calcium phosphate complexes on the coating. The bacteria digested or dissolved the coating, creating irregularly shaped holes. Although the integrity of the hydroxylapatite coating was focally damaged within 2-4 h of incubation with staphylococci, the extent of the damage was only marginal. Due to the formation of a layer of CaP precipitates though, bacteria could not be counted accurately after 4-8 h of incubation. This model could reveal part of the failure mechanism of infected hydroxylapatite coated implants. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 8
    ISSN: 0021-9304
    Keywords: total hip arthroplasty ; ceramic and polyethylene particles ; macrophage response ; flow cytometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Using the J774 macrophage cell line, we designed an in vitro model to analyze by flow cytometry the effects of size, concentration, and composition of ceramic (Al2O3 and ZrO2) and high density polyethylene (HDP) particles on phagocytosis and cell mortality. Inflammatory mediator (TNF-α) also was measured by ELISA. Kinetic studies revealed that phagocytosis of the particles begins very early after cell exposure, increasing with time and particle concentration and reaching a plateau after 15 h. This implies that the optimum period to evaluate cellular response to particulate debris is between 15 and 24 h of incubation. Results also showed that phagocytosis increases with concentration for particles up to 2 μm. For larger particles (up to 4.5 μm), phagocytosis seems to reach a plateau independent of size and concentration, which suggests a saturation of phagocytosis that is most likely dependent on overall particle volume ingested. We did not detect any significant difference in phagocytosis between Al2O3 and ZrO2 at 0.6 μm. Al2O3 seems to be more easily phagocytosed than HDP at the same size (4.5 μm) and concentrations. Cytotoxicity studies revealed that macrophage mortality increases with particle size and concentration for sizes greater than 2 μm. Smaller particles (0.6 μm) cause cell mortality only at higher concentrations (from 1,250 particles per cell), but the mortality is still very low (10%). No significant difference in cell mortality and TNF-α release was found between Al2O3 and ZrO2. Effects of Al2O3 and HDP at 4.5 μm were compared by measuring TNF-α release. Results showed that TNF-α release increases with particle concentrations and is higher with HDP than with Al2O3. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 600-607, 1998.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 10
    ISSN: 0935-6304
    Keywords: High performance size exclusion chromatography ; molecular weight ; lignin derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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