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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 10 (1971), S. 257-261 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung In Fortsetzung einer früheren Untersuchung wird in der vorliegenden Arbeit die Spannungsverteilung in einer viskoelastischen Flüssigkeit diskutiert, die trägheitslos zwischen zwei parallelen Wänden strömt, wenn die obere Wand mit konstanter Geschwindigkeit bewegt wird und an der unteren, in Ruhe befindlichen eine gleichförmige konstante Absaugung erfolgt. Das Spannungsfeld wird indessen im einzelnen nur für den Spezialfall diskutiert, daß auch die obere Wand ruht, und die infolge der Absaugung entstehenden Effekte werden aufgezeigt. Der wichtigste Unterschied im Verhalten einer viskoelastischen Flüssigkeit, verglichen mit einerNewtonschen Flüssigkeit, besteht darin, daß der Gradient der Normalspannungskomponente in horizontaler Richtung vom Wandabstand abhängt. Abschließend wird noch die Strömung durch ein zylindrisches Rohr mit gleichmäßiger konstanter Absaugung kurz diskutiert. Man findet, daß die Situation hier ganz ähnlich ist wie bei der ebenen Strömung, wenngleich dies nicht aus allgemeinen Betrachtungen gefolgert werden kann.
    Notes: Summary In continuation of an earlier investigation, the present paper discusses the stress distribution in the inertialess flow of a viscoelastic fluid confined between two plane parallel walls, in which the upper wall moves with a constant velocity while the lower is held at rest with a uniform constant suction applied on its surface. However, the stress field is discussed in detail for the case when the upper wall is also held at rest and the effects arising due to application of suction are pointed out. The most important difference in the behaviour of viscoelastic fluid, compared with that ofNewtonian fluid, lies in the fact that the gradient of the normal stress component in the horizontal direction depends on the distance from the walls. A short discussion has also been provided for the flow in a cylindrical tube with uniform constant suction applied on its surface. Though not evident from general considerations, it is seen that the situation here also is quite similar to that of plane flow.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 17 (1978), S. 557-567 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Die Strömung einer viskoelastischen Flüssigkeit vom Rivlin-Ericksen-Typ zwischen zwei rotierenden koaxialen Kreisscheiben wird numerisch untersucht. Die das Problem beschreibenden nichtlinearen Differentialgleichungen werden in analogen Gleichungen für finite Differenzen umgeschrieben und unter angepaßten Randbedingungen mit einem punktweisen Über-Relaxations-Verfahren (SOR) gelöst. Es werden zwei interessierende Fälle behandelt, zuerst der Fall, bei dem eine Platte ruht und die andere mit konstanter Winkelgeschwindigkeit rotiert, als zweiter derjenige, bei dem beide Platten mit gleichen konstanten Winkelgeschwindigkeiten, jedoch entgegengesetztem Drehsinn rotieren. Typische Beispiele für Reynoldszahlen zwischen 10 und 1000 werden für verschiedene Werte der nicht-newtonschen Parameter beschrieben und die Ergebnisse mit denen für newtonsche Flüssigkeiten verglichen.
    Notes: Summary A numerical investigation is made of the problem of flow of a viscoelastic fluid of the Rivlin-Ericksen type between rotating coaxial disks. The finite-difference analogues of the governing nonlinear ordinary differential equations are written and the resulting equations are solved using point successive overrelaxation method (SOR) under the appropriate boundary conditions. Two cases of interest are treated, namely, when one of the disk is at rest while the other rotates with a constant angular velocity and when both the disks rotate with constant angular velocities but in the opposite directions. Typical examples of Reynolds numberR in the range 10 ≤R ≤ 1000 are described for various values of the non-Newtonian parameters and results are compared with those for a classical viscous fluid.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 22 (1983), S. 268-274 
    ISSN: 1435-1528
    Keywords: Coating ; planar contraction ; moving boundary ; Oldroyd constitutive equation ; finite-difference method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The industrial process of coating flat surfaces with polymeric substances is numerically simulated by solving the full equations of motion for a flow through a contraction with a moving boundary. The four-constant Oldroyd constitutive equation is used to represent the viscoelastic fluid. Some adjustments to existing finite-difference methods are made in such a way as to avoid singular iterative matrices during the solution process. Results are presented for flow situations with Weissenberg numbers up to about three times larger than any previously published results for this problem.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 9 (1970), S. 419-423 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Das in einer früheren Untersuchung behandelte Problem der Wärmeübertragung in einer unendlich ausgedehnten nicht-Newtonschen Flüssigkeit infolge der stationären Rotation einer Kugel bei verschiedenen thermischen Randbedingungen wird für den Fall der thermisch isolierten Kugel hier ausführlich diskutiert. In erster Linie werden Bedingungen betrachtet, bei denen die Sekundärströmung in zwei getrennte Zonen zerfällt und die Konvektion von erheblich stärkerem Einfluß ist als die Dissipationseffekte infolge Viskoelastizität. Man findet, daß die Änderung der Sekundärströmung vom Beginn der Trennung in zwei Zonen bis zur vollständigen Richtungsumkehr von einer ausgeprägten Änderung der Temperaturverteilung begleitet ist. Der hier untersuchte Fall entspricht genähert den Bedingungen eines vor kurzem beschriebenen Experiments, bei dem Silikonöl verwendet wurde. Die vorhergesagten Ergebnisse stimmen mit den beobachteten in qualitativer Hinsicht recht gut überein.
    Notes: Summary In continuation of an earlier investigation, where the problem of heat transfer due to a sphere steadily rotating in an infinitely extending non-Newtonian fluid is discussed under various types of thermal boundary conditions, we presently reconsider this problem for the case in which the sphere is thermally insulated in some more details. The main attention is given to a situation where the secondary flow breaks down into two distinct zones and in which heat convection is strongly dominating over dissipation effects due to viscoelasticity. It is found that, for flow situations from beginning of separation up to complete reversal, the temperature distribution also undergoes marked changes. The chosen conditions correspond to those used in a recently reported experiment performed with polysiloxane. The theoretical and the observed results provide a fairly good qualitative agreement.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 111 (1980), S. 927-933 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Vanadium(V)-Oxidation vonL-Arabinose verläuft bezüglich des Oxidationsmittels und Substrats erster Ordnung. Bezüglich der Änderung von [H+] zeigte sich für den Bereich 2,5M–4,5M eine Abhängigkeit erster, im Bereich 5,0M–6,5M eine von zweiter Ordnung. Die Oxidationsgeschwindigkeit steigt mit der Ionenstärke und fällt mit der Dielektrizitätskonstanten des Mediums. Es wurden die thermodynamischen Parameter ΔE, ΔS ≠ und ΔG ≠ bestimmt: 22,63±0,19 kcal mol−1. −3,00±0,65 e. u. und 23,59±±0,05 kcal mol−1. Es wurde festgestellt, daß die Reaktion über die Bildung eines freien Radikals in einem langsamen, geschwindigkeitsbestimmenden Schritt initiiert wird.
    Notes: Abstract Vanadium(V) oxidation ofL-arabinose has been found to be first order with respect to oxidant and substrate concentrations. It has been found that the order with respect to [H+] changes from one in 2.5M–4.5M acid concentration range to two in 5.0M–6.5M acid concentration range. The oxidation rate has been found to increase with ionic strength and decrease with dielectric constant of the medium. Thermodynamic parameters ΔE, ΔS ≠ and ΔG ≠ have been evaluated as 22.63±0.19 kcal/mol,−3.00±0.65 e. u. and 23.59±±0.05 kcal/mol respectively. The reaction has been found to be initiated by the formation of free radical in a slow rate determining step.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 109 (1978), S. 319-323 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation ofd-xylose by Mn(III) pyrophosphate in sulphuric acid has been found to be first order with respect to [Mn(III)]. Variation of rate with [d-xylose] suggests the rapid formation of reversible cyclic complex between Mn(III) and id-xylose, which further disproportionates in a slow rate determining step. Oxidation rate has been found to increase with [H+]. Retardation of rate due to [pyrophosphate] and increase due to [Mn(II)] have been also observed. The value of thermodynamic parameters ΔE, ΔS≠, and ΔG≠ have been found to be 17.6±0.1 kcal/mole, −10.1±0.1 e.u. and 20.6±0.1 kcal/ mole respectively. A mechanism involving a free radical has been proposed for the reaction under study.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 36 (1980), S. 313-315 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Maltol inhibited growth and lactic acid synthesis byLactobacillus casei. The inhibition was partially overcome by the addition of casein hydrolysate and yeast extract. Some amino acid mixtures were also effective, among which glutamic acid was able to reverse the inhibition completely.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 44 (1988), S. 758-759 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rats fed on a rice diet deficient in lysine and threonine showed increased activities of CDP-Choline pathway enzymes and incorporation of (methyl-3H)-choline into hepatic microsomal phosphatidylcholine, compared to rats fed on the same diet supplemented with lysine and threonine. However, the amount of microsomal phosphatidylcholine was significantly decreased in rats fed a deficient rice diet. These results suggest an enhanced phosphatidylcholine catabolism in rats fed on a rice diet deficient in lysine and threonine. Malathion administration reduced the amount of phosphatidylcholine in all the groups.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 70 (1978), S. 373-380 
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Wanderung von 10 Metallionenarten im elektrischen Feld in wäßrigem sowie in wäßrig-alkoholischem Milieu mit Natriumnitrit als Komplexbildner wurde untersucht. Metallionen, die stabile Nitritkomplexe bilden, wandern mit negativer Ladung zur Anode, während die anderen zur Kathode wandern. Der Unterschied der Wanderungswerte in 2%iger und 5%iger Natriumnitritlösung bei 5 V/cm Ladung ist groß genug, so daß dieser komplexierende Elektrolyt sich zur Trennung auf Filterpapierstreifen sehr gut eignet. Die Wirkung der Potentialänderung sowie der Zugabe von Methanol, Äthanol bzw. Propan-2-ol zum Elektrolytgemisch wurde gleichfalls untersucht.
    Notes: Summary The electromigration of ten metal ions in aqueous and mixed water-alcohol media, with sodium nitrite as complexing electrolyte has been studied. Metal ions which form stable metal nitrite complexes were shown to move towards the anode as negative species, while the others moved towards the cathode. Differences in migration values in 2 and 5% sodium nitrite electrolyte at a potential gradient of 5 V/cm were large enough to make sodium nitrite a very useful complexing electrolyte for separation of these ions on filter paper strips. The effects of varying the applied potential gradient and of adding methanol, ethanol and propan-2-ol to the electrolyte system were also studied.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 7 (1979), S. 99-102 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of lithium on growth and aflatoxin production in chemically defined medium was studied on three aflatoxigenic strains of Asperigillus flavus group. The three strains used differed in their aflatoxin producing capacities. The possible mechanism of lithium induced stimulation of aflatoxin biosynthesis is discussed.
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