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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography A 604 (1992), S. 243-246 
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 83 (1952), S. 205-209 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Zusammenfassung An verschiedenen Ligninpräparaten wurden die Sulfitierung und alkalische Hydrolyse der gebildeten Ligninsulfosäuren zu Vanillin und Acetaldehyd untersucht.Brauns' Nativlignin läßt sich quantitativ aufschließen und ergibt in kürzester Zeit die besten Ausbeuten an diesen Aldehyden, während Cuproxamlignin und Salzsäurelignin zwar weitgehend sulfitierbar sind, aber die entsprechenden Aldehyde erst nach längerer Hydrolysendauer ergeben. Die Maskierung des mit Alkali spaltbaren Systems ist somit in der Konstitution des Lignins selbst begründet, da es sich bei diesen Präparaten um weitgehend zuckerfreie Lignine handelt.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 83 (1952), S. 197-204 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Zusammenfassung Die alkalische Hydrolyse chinolingefällter Fichtenligninsulfosäure (S 4,8%, OCH3 12,4%, Asche 12,1%) zeigt, daß in dieser Fraktion nur sehr wenig freie Coniferylaldehydhydrosulfosäure-Gruppen (1∶400 OCH3) vorhanden sind. Steigert man die Laugenkonzentration stufen weise von 0,1 bis 6 n, so wurden gleichartige Stufen der Acetaldehydabspaltung beobachtet, wobei mit 1 bis 2 n NaOH die maximalen Bereiche festgestellt werden konnten. An methyliertem Coniferylaldehyd wurde der quantitative und zeitliche Verlauf der hydrolytischen Spaltung zu Veratrumaldehyo und Acetaldehyd untersucht. Nach Ausarbeitung einer chromatographischen Trennungsmethode ließ sich zeigen, daß diese Spaltung in 14 Stdn. mit einer Ausbeute von etwa 80% vor sich geht. Methylierte Fichtenligninsulfosäure (OCH3 26,4%, S 2,34%) gab ein chromatographisch schwer trennbares Gemisch von Veratrumaldehyd, Acetaldehyd und einer noch nicht identifizierten Carbonylverbindung. Neben diesen Aldehyden wurde Vanillin isoliert, so daß man — eine vollständige Methylierung vorausgesetzt — annehmen kann, daß etwa ein Drittel des gebildeten Vanillins der unmethylierten LS aus abgedeckten Guajacylkernen stammt. Eine neue Darstellungsweise des Glukoconiferylaldehyds durch Oxydation des Coniferins wird beschrieben.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1430-4171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Supercritical fluid extraction (SFE) is a technique for sample preparation that is quickly replacing Soxhlet extraction and ultrasonic extraction. This manuscript introduces two real-world applications of SFE that serve as the basis of undergraduate laboratory experiments: the analysis of caffeine in ground coffee and nicotine in cigarette tobacco. The extracts are analyzed with gas chromatography-mass spectrometry (GC-MS). The experiments are presented in a discovery fashion that enables students to develop a theoretical understanding of the role of intermolecular forces in the extraction process. The focus on theoretical aspects of SFE makes these experiments appropriate for analytical and physical chemistry labs.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric radiology 26 (1996), S. 141-144 
    ISSN: 1432-1998
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lemierre's syndrome is a rare syndrome caused byFusobacterium necrophorum, a gram-negative anaerobic organism that normally inhabits the oropharynx. The syndrome follows primary oropharyngeal infection and affects previously healthy adolescents in a characteristic manner with fatal results if left untreated. The authors present two cases seen at their institution and discuss the clinical and radiologic features of the syndrome, along with considerations for patient management.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied mechanics and technical physics 40 (1999), S. 1126-1132 
    ISSN: 1573-8620
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A possible physical mechanism for additional hardening is proposed on the basis of an analysis of experiments on nonproportional cyclic loading of metals. A model for an elastoplastic polycrystal with a hardening law taking into account the interaction of slip systems is developed. The effect of additional hardening for elliptic strain paths and the shapes of stress paths and hysteresis loops typical of elliptic strain paths are described qualitatively. A violation of the assumption of the local determinacy and orientations of stress paths is considered for the square strain paths taking place in tests of chromium-nickel austenite stainless steels.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Fluid dynamics 25 (1990), S. 495-500 
    ISSN: 1573-8507
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Potentially unstable equilibrium is stabilized by means of a method of control based on the single-channel feedback principle using the characteristics of the solution of the complete nonlinear thermal convection equations. The convection equations are solved by a finite-difference method.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-8507
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The vibrational-convective instability of a plane horizontal fluid layer subject to longitudinal harmonic vibrations of finite frequency and transverse stratification in a static gravity field is studied. The analysis is based on the complete convection equations in the Boussinesq approximation. It is demonstrated that in the limiting case of high-frequency vibrations the results thus obtained coincide with those obtained earlier on the basis of the averaged equations. In the limiting low-frequency case the nature of the instability is quite different being due to the instability of oscillating counterstreams.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Fluid dynamics 30 (1995), S. 175-182 
    ISSN: 1573-8507
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Convection in a Hele-Shaw cell is studied analytically and numerically with allowance for heat exchange on the wide faces according to Newton's law. It is shown that this heat exchange has a considerable effect on the amplitude in the neighborhood of the threshold and explains laboratory experiments in which convection was observed even in the case of heating from above.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Fluid dynamics 31 (1996), S. 933-937 
    ISSN: 1573-8507
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The effect of weak mixture concentration on the threshold of convective instability of a binary mixture filling a cavity of arbitrary shape is investigated. In the case of thermally insulated boundaries in the neighborhood of the critical Rayleigh number monotonicity of perturbations is proved. This makes it possible to express the critical Rayleigh number for the mixture in terms of its analog for a single-component fluid at any values of the Soret parameter. In the general case of boundaries of arbitrary thermal conductivity an estimate of the critical Rayleigh number is obtained for small values of the Soret parameter.
    Type of Medium: Electronic Resource
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