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  • 1
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Naturkonvektion und Wärmeübertragungscharakteristik über eine vertikale Dichteinversionsebene hinweg wurde numerisch für Wasser untersucht. Die Kopplung und Wechselwirkung der Konvektionsströmungen, welche sich in zwei vertikalen Flüssigkeitsschichten mit gegensätzlichen Dichtegradienten einstellen, wird im Detail für Rayleighzahlen von 103 bis 106 analysiert. Der Abstand zwischen den Ebenen Θ=0 and Ψ=0 wird zur quantitativen Beschreibung der sich ändernden Temperatur- und Strömungsfeldern über die Dichteinversionsebene hinweg benutzt. Die numerischen Resultate zeigen, daß die dominante Konvektionsstruktur durch die horizontale Position der Ebene maximaler Dichte festgelegt ist bzw. durch die Temperaturen, welche an die vertikalen isothermen Wände angelegt werden. Das geometrische Seitenverhältnis des Behälters hat einen starken Einfluß auf die Struktur der Konvektion.
    Notes: Abstract Natural convection and heat transfer characteristics in water across a vertical density inversion plane is studied numerically. The coupling and interaction of the convective flows, which are generated in two vertical liquid layers of opposite density gradient, are presented in detail for Rayleigh numbers ranging from 103 to 106. The distance between θ=0 and Ψ=0 planes is used as quantitative description of the variations of the temperature and flow fields across the density inversion interface. The numerical results reveal that the dominant convection is determined by the horizontal location of the maximum density plane, i.e., the temperatures applied at the vertical isothermal walls. The cavity aspect ratio has a strong influence on the convective flow.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 32 (1997), S. 489-498 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Mittels einer radioskopischen Technik zur Visualisation von Strömungen wurden Experimente im Bereich freier Konvektion während des Schmelzens einer binären metallischen Ga/In-Legierung durchgeführt. Dieses Verfahren ermöglicht die Sichtbarmachung von Dichtefeldern in undurchsichtigen, durch niedrige Prandtl-Zahlen charakterisierten Fluiden und ihrer festen Phase. Nachdem einer mit 5 Gewichtsprozent Indium legierten Galliumschmelze ein horizontaler Temperaturgradient aufgeprägt worden war, entwickelte sich in der Binärschmelze eine vertikale Konzentrations-Stratifikation, wobei der Wärmeübergang nur durch Leitung erfolgte. Bei einer als ,,kritisch“ zu bezeichnenden Temperaturdifferenz trat Konvektion auf, die nach Erniedrigung der Temperaturdifferenz auf einen endlichen Wert wieder in den reinen Leitungsmechanismus umschlug. Diese Schwelle für das Einsetzen natürlicher Konvektion in binären Ga/In-Schmelzen fand noch keine theoretische Erklärung.
    Notes: Abstract Experiments were performed with a new radioscopic flow visualization technique on natural convection during melting of a binary metallic Ga-In alloy. This technique provides visualization of the density fields within opaque low Prandtl number fluids and their solids. Upon applying a horizontal temperature gradient to a gallium melt alloyed with 5 weight percent indium, the binary melt developed a vertical concentrational stratification and heat transfer was by conduction only. Convective flow developed at a higher temperature difference, which may be termed “critical”. After reducing the temperature difference the thermosolutal convection breaks down and a conductive state reappears at ΔT0 K. This threshold for onset of natural convection in binary Ga-In melts is in need of a theoretical explanation.
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  • 3
    ISSN: 1432-1181
    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 stability of Rayleigh-Bénard convection in a transparent model alloy was investigated with holographic interferometry. The dispersed minority phase is the heavier component. The majority component is lighter. A vertical temperature difference was applied to the liquid layer keeping the hot temperature always above phase separation. The upper cold side temperature was kept above or below the phase separation temperature. Fluid separation occurs when the cold temperature drops below consolute temperature. When the liquid is kept at higher than consolute temperature, it is noticed that the stability of the layer is increased when the average temperature approaches the consolute temperature.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Human genetics 〈Berlin〉 34 (1976), S. 73-76 
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Leukocyte peroxidase activity was estimated in 5 patients with the juvenile form of neuronal ceroid lipofuscinosis (Spielmeyer-Vogt's disease) and in 15 healthy controls. In contradiction to recent reports normal activity of p-phenylene diamine mediated peroxidase was found in the patients. The possible role of contamination of the white cell preparation with hemoglobin is discussed.
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  • 5
    ISSN: 1432-1041
    Keywords: Key words Etidronate ; Vitamin D deficiency; postmenopausal women ; osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The effects of vitamin D deficiency in osteopenic postmenopausal women treated with intermittent cyclical etidronate have been studied. Bone mass and biochemical parameters as bone markers were measured before and after one year of therapy with intermittent cyclical etidronate. Results: In 30 patients without vitamin D deficiency, bone mass in the lumbal spine and femoral neck was significantly increased compared to 28 vitamin D deficient patients. After cyclical intermittent etidronate therapy, serum osteocalcin and PTH were significantly increased in the vitamin D deficient patients, whereas in non-vitamin D deficient patients they did not change. Conclusion: It is worthwhile measuring serum vitamin D before starting etidronate therapy and, in case of deficiency, to give vitamin D.
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  • 6
    ISSN: 1432-2323
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Chez les malades atteints de sténose du tronc coronaire gauche (TCG), les accidents du cathétérisme sont plus fréquents, les résultats du traitement médical sont moins bons, la morbidité et la mortalité postopératoire sont plus élevées que chez les patients présentant d'autres lésions d'artériosclérose coronaire, simples ou multiples. La sténose du TCG se traduit par des manifestations cliniques très variées, allant du patient “asymptomatique” qui n'a que des tests d'effort perturbés jusqu'au malade gravement atteint chez qui la coronarographie et l'opération doivent être faites en urgence. Au Peter Bent Brigham Hospital, entre 1970 et 1977, nous avons opéré 141 malades atteints de sténose du TCG. La mortalité opératoire a été de 10% (5 sur 49) pour les malades en état instable, de 4% (4 sur 92) pour les malades stables, de 6% (9 sur 141) au total. La survie actuarielle jusqu'à 90 mois est meilleure chez les malades stables que chez les instables, chez les patients chez qui une revascularisation complète a pu être réalisée, chez ceux qui avaient comme seule lésion une sténose du TCG. Des études prospectives, des traitements médicaux et chirurgicaux, indiquent que les malades atteints de sténose du TCG doivent être opérés de pontage coronaire.
    Notes: Abstract Catheterization morbidity, results of medical treatment, and operative morbidity and mortality in patients with left main coronary artery stenosis (LCA) are higher than in patients with other coronary atherosclerotic lesions, occurring in combination or alone. Patients with LCA stenosis have a wide variety of clinical manifestations and range from “asymptomatic” patients with only positive exercise tests to critically ill, unstable patients requiring emergency angiography and operation. Experience with the surgical treatment of LCA stenosis in 141 patients at the Peter Bent Brigham Hospital from 1970–1977 is reviewed. Operative mortality rates were 10% (5/49) in unstable patients, 4% (4/92) in stable patients, and 6.4% (9/141) overall. Actuarial survival up to 90 months was better in stable than unstable patients, in patients who were completely rather than incompletely revascularized, and in patients in whom only LCA stenosis existed and was bypassed. Prospective studies of medical and surgical treatment support the concept that patients with LCA disease should be treated with coronary bypass surgery.
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  • 7
    ISSN: 1432-0630
    Keywords: PACS: 44.30.+v; 81.10.Fq; 81.30.Fb
    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 vertical layer of an eutectic gallium indium mixture was subjected to a horizontal temperature gradient. The well stirred melt was first solidified and then remelted in a slow, quasi-steady fashion. Real-time visualization of the processing is provided by radioscopy. It was observed that gravitational segregation leads to 1) a break down of convection, and 2) an early solidification of β-indium, followed by an eutectic solidification of most of the remaining melt. The amount of observed concentrational segregation is higher than predicted by theory. The experimental findings have never been predicted in modeling efforts of similar situations including convection; possible reasons are discussed.
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  • 8
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 175 (1955), S. 36-37 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In order to test this prediction, one of us (J. R. K.) has carried out a series of observations in the audiofrequency band at Achimota, Gold Coast (lat. 6 N., long. 0 12' W.), which is about 10 north of the geomagnetic equator. The atmospherics were received on the equipment that was previously ...
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 191 (1961), S. 1083-1084 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Work on these disturbances now being pursued at University College, Ibadan, and at the University of Ghana, Accra, shows that the irregularities in the pattern on the ground are elongated in the direction of the Earth's magnetic field, that the axial ratio is greater than 6:1, and that the smaller ...
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