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161.
Radio-frequency (RF) floating zone single crystal growth is an important technique for the preparation of single bulk crystals. The advantage of the floating-zone method is the crucible-free growth of single crystals of reactive materials with high melting points. The strong heat diffusion on the surface, as well as the melt convection in the molten zone due to induction heating, often leads to an undesired solid-liquid interface geometry with a concave (towards the solid phase) outer rim. These concave parts aggravate the single crystal growth over the full cross-section. A two-phase stirrer was developed at IFW Dresden in order to avoid the problems connected with these concave parts. It acts as a magnetic field pump and changes the typical double vortex structure to a single roll structure, thus pushing hot melt into the regions where the concave parts may arise. The current in the secondary coil is induced by the primary coil, and the capacitor and the resistance of the secondary circuit are adjusted to get a stable 90 degree phase-shift between the coil currents. Single crystal growth of industrial relevant RuAl and TiAl intermetallic compounds was performed based on the material parameters and using the adjusted two-phase stirrer. Very recently, the magnetic system was applied to the crystal growth of biocompatible TiNb alloys and antiferromagnetic Heusler MnSi compounds. 相似文献
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Hermann E. Posch Marc J. P. Leiner Otto S. Wolfbeis 《Fresenius' Journal of Analytical Chemistry》1989,334(2):162-165
Summary This work describes the development of the first optical pH-sensor capable of measuring pH-values in the 0–7 range. The pH-sensitive material consists of fibrous amino-ethyl cellulose onto which fluorescein and eosin were covalently immobilised. Fluorescein was immobilised via its isothiocyanate, and immobilised eosin was obtained by bromination of the immobilised fluorescein. The material thus obtained was mechanically fixed at the end of a bifurcated optical fibre bundle. Fluorescence was excited at 490 nm and measured at >540 nm. The accuracy of the sensor is ±0.05 pH units, its response time ranges from 25 to 30 s. Practically no signal loss was observed upon constant illumination over periods of more than 15 h.
Entwicklung einer Magensonde: Eine Optode für den pH-Bereich 0–7相似文献
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Hermann Emde 《Fresenius' Journal of Analytical Chemistry》1909,48(10):641-642
Ohne Zusammenfassung 相似文献
168.
Eberhard Reimann Wolfgang Erdle Eugen Hargasser Hermann Lotter 《Monatshefte für Chemie / Chemical Monthly》2002,133(7):1017-1030
Summary. The stereoselective synthesis of cis-ergoline is presented. Starting from rac-N-benzoyl tryptophan methyl ester, the key compound indolinylmethylpyridin-3-one was prepared via a seven-step reaction in good yield. Since its cyclization to the desired ergolinone failed, the key compound was reduced
to yield the two diastereomeric pyridin-3-ols; only one of them cyclized in trifluoromethanesulfonic acid, affording cis-ergoline. Catalytic hydrogenation of the latter gave N,N′-dimethyldihydroergoline, the X-ray crystallography of which revealed both the correct structure and identical relative configurations
at C-5a and C-6a (SS or RR). Hydroboration and subsequent perruthenate oxidation of the Δ9-ergoline provided access to the regioisomeric ergolinols and ergolinones.
Received December 27, 2001. Accepted January 15, 2002 相似文献
169.
We consider the Goursat problem in the plane for partial differential operators whose principal part is the pth power of the standard Laplace operator. The data is posed on a union of 2p distinct lines through the origin. We show that the solvability of this Goursat problem depends on Diophantine properties
of the geometry of lines on which the data is posed.
The first author is supported in part by DMS-0401215.
The second author is supported in part by Grant MTM2006-13000-C03-03 of the D.G.I. of Spain. 相似文献
170.
We consider the product AB of two finite mutually permutable subgroups A, B and find some subnormal subgroups of the product. This leads to local and otherwise generalized statements about products of supersolvable groups.Received: 19 May 2004 相似文献