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  • 1
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Factor assays of normal citrated plasma following incubation with nonleaching heparinized surfaces in high surface area-plasma volume ratios showed a marked pattern of reduction in factor IX activity, with lesser depression of II and X. No or modest effect on other factors was observed. In particular, no significant adsorption of factor XII (Hageman) by either cationic or anionic surfaces, was found. No consistent pattern of effects was seen with a group of strongly anionic surfaces, analogous to the sulfate and sulfamate groupings of the heparin molecule. However, certain members of this class showed profound effects on factor XI.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Russian Abstract.
    Abstract: It seems advisable to investigate polycondensation processes extended systematically from low to high conversion by carefully chosen model systems, considering the statistical data available on the processes themselves and the relationship between structure and properties of the resulting polymers. In a previous paper (Rev. Gén. Caoutchouc Plastiques, Éd. Plastiques, 4, (1967) 111) dealing with conventional crosslinking agents, the possibility was suggested to perform polycondensation processes approaching more closely the classical random distribution. This can be achieved with symmetrical monomers having functional groups well spaced out to avoid substitution effects and cyclisation. Cyclisation is also rendered more difficult by greater stiffness of the structure of the monomers. This paper shows by some examples that, in favourable cases, the deviation from the classical random distribution can be reduced to the limits of experimental error, thus enabling the physical properties to be compared with the results of comparatively simple model calculations.
    Notes: Es ist ratsam, Polykondensationsprozesse an äußerst sorgfältig gewählten Modellsystemen zu studieren, und zwar systematisch von niedrigeren nach höheren Umsätzen, und indem man die Kenntnis der Prozesse selbst, der resultierenden Struktur der Produkte, und deren strukturgebundenen physikalischen Eigenschaften gleichzeitig auf statistischer Basis vertieft. In einem früheren Bericht (Rev. Gén. Caoutchouc Plastiques, Éd. Plastiques, 4, 1967, 111) über bekannte organische und anorganische Netzformer wurde auf die Möglichkeit hingewiesen, Polykondensationssysteme zu entwickeln, die den reinen klassischen Zufallsverteilungen in viel besserer Näherung folgen. Hierzu wählt man symmetrische Monomere mit räumlich weit auseinanderliegenden Funktionen, um Substitutionseffekte und Ringschlüsse weitgehend zu vermeiden; weiterhin werden Ringschlüsse auch durch Steifheit der Monomerstruktur sehr erschwert. In diesem Vortrag wird an einigen Beispielen belegt, daß man so tatsächlich die Abweichungen vom klassischen (cyclenfreien) Zufallsmodell in günstigen Fällen erwartungsgemäß bis zur Grenze der Unmeßbarkeit zurückdrängen kann, und daß sich das deshalb lohnt, weil man dann physikalische Eigenschaften der Produkte mit relativ einfachen Modellrechnungen vergleichen kann.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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