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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 23 (1977), S. 393-395 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 26 (1975), S. 703-706 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Autoclave arrangement for oxidation and corrosion tests of materials in pressurized waterThe authors describe an arrangement with an autoclave for corrosion and oxidation tests in pressurized water and steam. The autoclave has been conceived for a pressure of 250 bar at 500 °C. It is equipped with four locks enabling the specimens to be exchanged during operation without any markable influence on the working conditions. The aggressive medium can be exchanged continuously at a rate of 2,5 l/h. In addition to pressure and temperature controls the arrangement is equipped with a water quality control system.
    Notes: Es wird eine Autoklavenanlage für Korrosions-und Oxidationsuntersuchungen mit Hochdruckwasser bzw. Wasserdampf beschrieben. Die Auslegungsdaten des Autoklaven sind 250 bar bei 500 °C. Der Autoklav besitzt 4 Schleusen, über die während des Betriebes ein Probenwechsel ohne größeren Einfluß auf die Betriebsbedingungen möglich ist. Das korrodierende Medium kann kontinuierlich mit einer max. Rate von 2,5 l/h ausgetauscht werden. Neben der Druck- und Temperaturkontrolle ist eine Überwachung der Wasserqualität vorgesehen.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 28 (1977), S. 676-683 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Phase transformations of the ZrNb 3 Sn 1 alloyThe phases transformations of cold-worked Zr-Nb 3-Sn 1-alloy have been studied as a function of heat tratements between 500-600°C in vacuum. Microscopic and X-ray diffraction analyses reveal allow us to state that again of a 50% cold-worked Zr-Bb 3-Sn 1-alloy at 597°C gives rise to a maximum ß-Nb content in the ß-Zr-matrix after 4 hours annealing.
    Notes: Die Phasenumwandlungen der Zr-Nb3-Sn 1-Legierung mit verschiedenen Kaltverformungen wurden in Abhängigkeit der Wärmebehandlung bei Temperaturen zwischen 500 und 600°C im Vakuum untersucht. Durch lichtmikroskopische Beobachtung und Röntgenbeugungsanalyse konnte im Fall einer Zr-Nb 3-Sn 10-Legierung mit 50%iger Kaltverformung, die einer Wärmebehandlung bei 597°C unterworfen wurde, nachgewiesen werden. Daß die ß-Nb-Konzentration in der ß-Zr-Matrix nach etwa 4 Stunden Wärmebehandlungszeit praktisch ein Maximum erreicht hat.
    Additional Material: 19 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 29 (1978), S. 258-265 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Influence of a mechanical treatment on the oxidation behaviour of ZrNb 3 Sn 1 alloy in oxygenIt has been found by means of gravimetric, microscopic, screen electron microscopic and x-ray diffraction investigations that the corrosion resistance of a Zr-Nb 3-Sn 1 alloy in oxygen (po2 = 3.3 × 104 Pa) between 400 and 460° C increases with increasing extent of cold rolling between 10 and 50%. Initially, the oxidation obeys a parabolic rate law with an activation energy the value of which becomes larger with increasing cold forming. After a critical thickness of the oxide layer is reached a transfer to a linear rate law occurs. The time of this transition becomes larger with increasing cold forming. Form the three processes which are responsible to the oxide layer growth mainly the diffusion of oxygen through the oxide layer via oxygen ion vacancies is the rate-determining step. In the later period of oxidation, however, a diffusion via grain boundaries must also be considered. The manner of the oxide growth is decisively determined by the cold forming regarding to a preferred orientation of the α-Zr grains in the alloy and to an epitaxial formation of oxide nucleus and of oxide crystals in the later period of oxidation.
    Notes: Mittels gravimetrischer, lichtmikroskopischer, rasterelektronenmikroskopischer und röntgendiffraktometrischer Untersuchungen wurde unmittelbar bestätigt, daß sich die Oxidationsbeständigkeit der Zr-Nb 3-Sn 1-Legierung im Sauerstoff (po2 = 3,33 × 104 Pa) bei Temperaturen zwischen 400 und 460 °C mit zunehmender Kaltverformung (zwischen 10 und 50% Kaltverformungsgrad) erhöht. Die Oxidation folgt zuerst einem parabolischen Zeitgesetz mit einer Aktivierungsenergie, deren Wert mit steigender Kaltverformung zunimmt. Nach Erreichen einer kritischen Schichtdicke wird ein Übergang zu einem linearen Zeitgesetz beobachtet. Die Übergangszeit ihrerseits nimmt mit steigender Kaltverformung zu. Obwohl während des Aufbaus des Zunders drei miteinander verknüpfte Vorgänge erfolgen, stellt die Diffusion von Sauerstoff durch die Oxidschicht über Sauerstoffionen-Leerstellen und längs von Kanten und Korngrenzen den reaktionsbestimmenden Schritt dar. Die Kaltverformung bestimmt die Art des Wachstums des Zirkonoxids, zunächst durch eine bevorzugte Orientierung der α-Zr-Körner in der Legierung und danach durch eine epitaktische Ausbildung der Oxidkeime und der Oxidkristallite im weiteren Verlauf der Oxidation.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 75 (1979), S. 215-222 
    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: Mit abgebauten PVC-Proben verschiedener Taktizitäten wurden zwei Reihen Ozonolysereaktionen mit 1 und 24 h durchgeführt. Bei der Ozonolyse wurde die Verteilug der Polyensequenzlängen durch UV-Vis-Spektroskopie verfolgt. Die Kettenspaltungszahl der analysierten Proben wurde durch Bestimmung des Molekulargewichtes vor und nach der Ozonolyse berechnet.Die beobachtete Zunahme der kürzeren Polyensequenzen im Vergleich zu längeren Polyensequenzen bei der Ozonolyserektion hängt von den syndiotaktischen Sequenzen ab. Es wurde andererseits gefunden, daß bei PVC die Zahl der Kettenspaltungen nach der vollständigen Ozonolyse um so kleiner ist, je größer der Anteil von taktischen Sequenzen ist.
    Notes: Two sets of ozonization reactions, for 1 h and 24 h respectively, have been carried out at -20°C on degraded samples of PVC having different contents of tactic sequences. The evolution of the polyene sequences distribution with the ozonization was followed by UV-Visible spectroscopy. The number of chain scissions of ozonized samples was calculated from the number average molecular weight measurements before and after ozonization.The observed increase of short polyenes relative to the long polyenes with ozonization was found to depend markedly on the content of syndiotactic sequences. On the other hand, the number of chain scissions after total ozonization was found to be the higher the lower the content of tactic sequences in PVC samples is.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 45 (1975), S. 177-184 
    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: Bei 40, 0 und -50°C hergestellte PVC-Proben wurden nach verschiedenen Methoden fraktioniert. Die Fraktionen wurden durch Viskositätsmessungen und IR-Spektroskopie charakterisiert. Der thermische Abbau der Fraktionen wurde bei 175, 180 und 185°C durch fortlaufende Messung des abgespaltenen Chlorwasserstoffs in einem Leitfähigkeitsapparat untersucht. Die kinetischen Ergebnisse und die Spektren der Proben zeigen, daß die syndiotaktischen Sequenzen die Ursache für den schnellen Abbau sind und daß dabei lange Polyensequenzen entstehen, wie schon früher bei unfraktionierten Polymeren ermittelt wurde.
    Notes: PVC samples prepared in bulk at 40, 0, and -50°C were fractionated by different methods. The samples were characterized by viscosimetric measurements and by IR spectroscopy in order to determine the tacticity. The thermal degradation of the samples was studied at 175, 180, and 185°C by means of continuous measuring of the evolved HCl in a conductivity apparatus. From the kinetic results and the UV-visible spectra recorded on equally degraded samples follows that syndiotactic sequences give rise to high degradation rates as well as to long polyene sequences in agreement with results previously obtained with unfractionated polymers.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 46 (1975), S. 81-87 
    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: Ein technisches PVC und eine andere in Substanz bei 40°C hergestellte Probe wurden nach der Lösungsmethode mit Methanol-Cyclohexanon-Gemischen fraktioniert. Beide Polymere geben Fraktionen mit gleicher Taktizität, aber verschiedenen Molekulargewichten. Der thermische Abbau wurde bei 175, 180 und 185°C durch fortlaufende Bestimmung des abgespaltenen HCl in einem Leitfähigkeitsapparat untersucht. Je niedriger das Molekulargewicht ist, desto größer ist die Abbaugeschwindigkeit; dies gilt aber nur für Polymere mit Molekulargewichten bis etwa 60 000 oder 90 000; oberhalb dieser Werte ist die Abbaugeschwindigkeit vom Molekulargewicht unabhängig. Die Spektren der Proben mit dem gleichen Abbauumsatz zeigen, daß die Verteilung der Polyensequenzen gleich ist und daher nicht vom Molekulargewicht beeinflußt wird.
    Notes: A commercial PVC and another one prepared in bulk at 40°C were fractionated by means of fractional solution method using cyclohexanone-methanol mixtures. Both fractionations resulted in two sets of fractions. Their thermal degradation at 175, 180 and 185°C was followed by means of a conductivity cell which allows a continuous titration of the evolved HCl. The results showed that the lower the molecular weight the higher the degradation rate was; nevertheless, this relationship is only valid up to molecular weights of 60 000 to 90 000, from which the degradation rate appeared to be independent on the molecular weight. The UV-visible spectra of the degraded polymers suggest a similar polyene sequence distribution for all the fractions which accounts for a similar mechanism of degradation in contrast to what happens to fractions with different tacticity.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 13 (1975), S. 385-390 
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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  • 9
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Four fractions of poly(vinyl chloride) (PVC) having appreciably different tacticity distributions were prepared by selective extractions on samples polymerised at temperatures between +60 and -50°C. They were degraded thermally at 180°C in the solid state to conversions in the range 0,2 to 0,5% and in solution at 200°C to conversions in the range 1,6 to 5%. The polyene sequence distribution was investigated by ultra violet/visible (UV/VIS) and resonance Raman spectroscopy. The results show that the type of polyene sequence distribution depends markedly on the tacticity distribution of the polymer. Cross-linking reactions occur more readily as the syndiotacticity increases. The results are discussed and interpreted with reference to previous work relating degradation processes and tacticity.
    Additional Material: 6 Ill.
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  • 10
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Endogenous tryptamine, 5-hydroxytryptamine, indoleacetic acid, 5-hydroxyindoleacetic and tryptophan have been recovered from urine and cerebro-spinal fluid by adsorption on XAD-2 resin (0.3 g). After adsorption of the sample on the resin, desorption with methanol provides a single fraction that contains all of these metabolites. The mass spectra of their pentafluoropropionyl derivatives show prominent ions at m/e 276 and 438 which are characteristic of indoles and 5-hydroxyindoles, respectively, a feature that allows the concurrent determination of all the components of each group by functional group analysis. A method has been developed to carry out single ion monitoring with the peak matching system of an Hitachi RMU-6H mass spectrometer. Identifications are based on the respective Kovats Indices and single ion monitoring of two characteristic ions per compound: tryptophan (m/e 276 and 347); tryptamine (m/e 276 and 289); indoleacetic acid (m/e 276 and 335); 5-hydroxytryptamine (m/e 438 and 451); 5-hydroxyindoleacetic acid (m/e 438 and 497). The method described illustrates the feasibility of assaying biogenic indoleamines and acidic metabolites, as well as their precursor amino acid on a single fraction in contrast to other standard fractionation methods. This is possible even if the mass spectrometer is not equipped with an alternating voltage accelerator provided that it has a peak matcher, although the lack of an alternating voltage accelerator requires two separate injections of the same sample, for quantification and identification; one for the indole profile and another for the 5-hydroxyindole profile. Both profiles can be verified by individual monitoring of the other confirmatory ions. With this method the use of a multiple ion detector would allow a simultaneous determination of all of these metabolites in one gas chromatograph mass spectrometer run.
    Additional Material: 3 Ill.
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