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  • 1
    Digitale Medien
    Digitale Medien
    Behavior of drops in contact with pool surfaces of different liquids (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 2786-2796 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The behavior of small liquid drops, hanging from a circular disk and approaching a pool surface of the same liquid at different temperatures, is studied experimentally and numerically. The experiments show that if isothermal conditions prevail the drop is immediately engulfed by the liquid. On the contrary, if the temperature of the drop is sufficiently larger or sufficiently smaller than the temperature of the liquid surface, this engulfment is prevented even if the drop is pressed on the liquid surface and "enters" the liquid pool. A number of experiments have been carried out on silicone oils (with different viscosities). At the same time the problem was studied numerically with the assumption that a thin air film is formed between the drop and the liquid bath surface, due to the entrainment of the surrounding air caused by the Marangoni flow; the pressure in the air film balances the pressure necessary to keep the drop submerged in the liquid bath. The critical temperature differences for the drop engulfment are determined experimentally. A parametric numerical analysis is performed to determine the influence of the viscosities of the liquids. The experimental findings are correlated by computed critical temperature differences. A sufficient agreement is found between numerical and experimental results. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.869802
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  • 2
    Digitale Medien
    Digitale Medien
    Instability of thermocapillary convection in liquid bridges (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 555-565 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: It is well known that thermocapillary convection arises in liquid bridges when the support discs are heated differentially and uniformly. Upon increasing the temperature difference, the convective flow shows a transition from an axisymmetric to an oscillatory regime. This phenomenon has been investigated both experimentally and theoretically, but prior experimental results exhibit some discrepancies with respect to the predictions of stability analyses. The present paper discusses experimental results obtained under microgravity conditions, comparing them with previous experimental observations made on ground and in space and with recent theoretical models of the instability. The results agree with the description of oscillations in terms of superposition of hydrothermal waves. Finally, a possible mechanism for a "pulsating" instability is proposed, together with a new scaling law for the oscillation frequencies at onset; this law, which correlates the critical frequency to the fluid properties, the geometrical parameters and the critical temperature difference, agrees with all the available experimental data. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.869583
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  • 3
    Digitale Medien
    Digitale Medien
    Oscillatory Marangoni convection in cylindrical liquid bridges (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 2906-2922 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Oscillatory Marangoni convection in silicon–oil liquid bridges, sustained by two circular coaxial disks with prescribed time-dependent temperature profiles and bounded by cylindrical free surfaces, is investigated by direct three-dimensional (3-D) and time-dependent simulation of the model equations, using finite difference methods explicit in time and a staggered spatial mesh in cylindrical coordinates. It is shown that, for low enough values of the dimensionless rate of ramping, the time-dependent nature of the boundary conditions becomes unimportant and the computed critical Marangoni numbers approach the values obtained with steady stability analyses. For typical microgravity experiments, involving unsteady boundary conditions, the computed critical Marangoni numbers and the oscillation frequencies agree with available experimental data of sounding rockets and Spacelab experiments. The 3-D thermo-fluid-dynamic oscillatory regime structures are depicted, discussed, and compared with previous experimental and theoretical analyses, providing physical explanations of the onset of instability and coherent pictures of the flow organization when oscillatory conditions are established. Immediately after the onset of instability, the oscillatory flow can be described by a standing wave and a pulsating temperature distribution. When the oscillatory disturbances become large, the azimuthal velocity causes the rotation of "temperature spots'' along the free surface of the liquid bridge so that the time-dependent temperature and velocity fields can be properly described by the dynamic model of an azimuthally traveling wave. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.869070
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  • 4
    Digitale Medien
    Digitale Medien
    Drops pushing by Marangoni forces (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 1513-1516 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Numerical simulations and laboratory experiments show that Marangoni effects are responsible for a pushing force on a droplet interacting with a solid wall in the presence of a temperature gradient. The results clarify questions of interest in the field of material science, in particular, they may provide some explanation for the minority phase separation observed during solidification processes under microgravity conditions. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1359418
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  • 5
    Digitale Medien
    Digitale Medien
    Influence of buoyancy forces on Marangoni flow instabilities in liquid bridges (2000)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 10 (2000), S. 721-749 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The influence of buoyancy forces on oscillatory Marangoni flow in liquid bridges of different aspect ratio is investigated by three-dimensional, time-dependent numerical solutions and by laboratory experiments using a microscale apparatus and a thermographic visualisation system. Liquid bridges heated from above and from below are investigated. The numerical and experimental results show that for each aspect ratio and for both the heating conditions the onset of the Marangoni oscillatory flow is characterized by the appearance of a standing wave regime; after a certain time, a second transition to a travelling wave regime occurs. The three-dimensional flow organization at the onset of instability is different according to whether the bridge is heated from above or from below. When the liquid bridge is heated from below, the critical Marangoni number is larger, the critical wave number (m) is smaller and the standing wave regime is more stable, compared with the case of the bridge heated from above. For the critical azimuthal wave number, two correlation laws are found as a function of the geometrical aspect ratio A.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615530010350444
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  • 6
    Digitale Medien
    Digitale Medien
    Lymphocytes on sounding rockets
    Amsterdam : Elsevier
    Advances in Space Research 12 (1992), S. 141-144 
    Details
    ISSN: 0273-1177
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(92)90276-4
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  • 7
    Digitale Medien
    Digitale Medien
    Measurement of surface temperature in microgravity experimentation - problems and solutions
    Amsterdam : Elsevier
    Advances in Space Research 8 (1988), S. 121-132 
    Details
    ISSN: 0273-1177
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(88)90012-9
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  • 8
    Digitale Medien
    Digitale Medien
    Non-intrusive techniques for thermal measurements in microgravity fluid science experiments
    Amsterdam : Elsevier
    Advances in Space Research 6 (1986), S. 69-80 
    Details
    ISSN: 0273-1177
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(86)90186-9
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  • 9
    Digitale Medien
    Digitale Medien
    REPLACEMENT OF THE UPPER DECK OF THE GEORGE WASHINGTON BRIDGE (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 352 (1980), S. 0 
    Details
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1749-6632.1980.tb16369.x
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  • 10
    Digitale Medien
    Digitale Medien
    Production, purification and characterization of an extracellular inulinase from Kluyveromyces marxianus var. bulgaricus (2000)
    Springer
    Journal of industrial microbiology and biotechnology 25 (2000), S. 63-69 
    Details
    ISSN: 1476-5535
    Schlagwort(e): Keywords: inulin; inulinase; Kluyveromyces marxianus var. bulgaricus; extracellular enzyme
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The yeast Kluyveromyces marxianus var. bulgaricus produced large amounts of extracellular inulinase activity when grown on inulin, sucrose, fructose and glucose as carbon source. This protein has been purified to homogeneity by using successive DEAE-Trisacryl Plus and Superose 6HR 10/30 columns. The purified enzyme showed a relative molecular weight of 57 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and 77 kDa by gel filtration in Superose 6 HR 10/30. Analysis by SDS-PAGE showed a unique polypeptide band with Coomassie Blue stain and nondenaturing PAGE of the purified enzyme obtained from media with different carbon sources showed the band, too, when stained for glucose oxidase activity. The optimal hydrolysis temperature for sucrose, raffinose and inulin was 55°C and the optimal pH for sucrose was 4.75. The apparent K m values for sucrose, raffinose and inulin are 4.58, 7.41 and 86.9 mg/ml, respectively. Thin layer chromatography showed that inulinase from K. marxianus var. bulgaricus was capable of hydrolyzing different substrates (sucrose, raffinose and inulin), releasing monosaccharides and oligosaccharides. The results obtained suggest the hypothesis that enzyme production was constitutive. Journal of Industrial Microbiology & Biotechnology (2000) 25, 63–69.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/sj.jim.7000032
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