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71.
Direct measurements of the bulk flow of a ferrofluid in a uniform rotating magnetic field were obtained using the ultrasonic velocity profile method. The fluid was observed to corotate with the field in a rigid-body-like fashion throughout the bulk of the container, except near the air-fluid interface, where it was observed to counterrotate. The results were found in qualitative agreement with the spin diffusion theory of Zaitsev and Shliomis [J. Appl. Mech. Tech. Phys. 10, 696 (1969)]10.1007/BF00907424. 相似文献
72.
73.
Helmut Zahn 《Colloid and polymer science》1949,113(3):157-159
Zusammenfassung Die Verkürzung verschiedener Keratinfasern in 50proz. Phenol wurde in Abh?ngigkeit von der Temperatur untersucht.
Die zur Erzielung einer mittleren Schrumpfung der Haare erforderliche Temperatur (Erweichungstemperatur) h?ngt von der Herkunft
der Haare ab. Schafwolle erweicht bei 84°, Menschenhaar bei 95° C. Zusammenh?nge zwischen der Erweichungstemperatur, dem Verhornungsgrad,
Cystingehalt und dem histologischen Aufbau der Fasern werden besprochen.
31. Mitteilung über Struktur und Reaktions-f?higkeit der Faserkeratine; 30. Mitt. E. El?d und H. Zahn, Kolloid-Z.113, 10 (1949).
Herrn Professor Dr.-Ing. E. El?d danke ich für das f?rdernde Interesse, Frl. M. Schneider für die Durchführung der Messungen. 相似文献
74.
75.
Meier R Maigut J Kallies B Lehnert N Paulat F Heinemann FW Zahn G Feth MP Krautscheid H van Eldik R 《Chemical communications (Cambridge, England)》2007,(38):3960-3962
The equilibrium between the twist-boat (tb) and half-chair (hc) conformers of the central diamine chelate ring of [Fe(III)(tmdta)]- in solids and aqueous solution has been studied by Raman spectroscopy, supported by calculated Raman spectra using Density Functional Theory. 相似文献
76.
A. Milekhin N.P. Stepina A.I. Yakimov A.I. Nikiforov S. Schulze D.R.T. Zahn 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):355-359
Self-organised Ge dot superlattices grown by molecular beam epitaxy of Ge and Si layers utilizing Stranski-Krastanov growth
mode were investigated by Raman spectroscopy. An average size of Ge quantum dots was obtained from transmission electron microscopy
measurements. The strain and interdiffusion of Ge and Si atoms in Ge quantum dots were estimated from the analysis of frequency
positions of optical phonons observed in the Raman spectra. Raman scattering by folded longitudinal acoustic phonons in the
Ge dot superlattices was observed and explained using of elastic continuum theory.
Received 25 January 2000 相似文献
77.
D.W. Hough U. Jaenicke‐Roessler G. Zahn A. Belger A. Guembel C.‐G. Oertel W. Skrotzki 《Crystal Research and Technology》2000,35(4):409-417
Y2Pd14B5 is the major phase in as‐cast and annealed multiphase alloys with nominal compositions near YPd5B3C0.3. Its crystal structure determined the first time here by single crystal X‐ray diffraction is body‐centered tetragonal (space group I41/amd). Transmission electron microscopy (TEM) reveals that in as‐cast specimens the tetragonal phase has a modulated structure and is oriented intergrown with a face‐centered cubic phase of similar composition, namely YPd7B2. According to Rietveld analyses of the multiphase system the structure of this phase can be well‐described by space group Fm m. Annealing the sample for 150 hrs at 973 K results in a coarsening and enrichment of the tetragonal phase as well as a disappearance of the modulations allowing a detailed structure analysis by single crystal diffractometry. 相似文献
78.
Fleischhauer J Zahn S Beckert R Grummt UW Birckner E Görls H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4549-4557
Pentacene and its derivatives are among the most important examples of π-electron-rich molecules used in organic field effect transistors. The replacement of CH groups by nitrogen atoms opens an elegant way to generate highly electron-deficient molecules, known as oligoazaacenes. We describe the synthesis and spectroscopic properties of two novel derivatives of this family, namely the zwitterionic and quinoidal conjugated forms of dihydro-5,6,7,12,13,14-hexaazapentacene (fluorubine). We outline a powerful strategy to tune the electronic properties of these redox-active azaacenes by the selective introduction of substituted pyrazines. Their acidochromic and solvatochromic behaviour is investigated experimentally and interpreted with the help of theoretical calculations. The simple "exchange" of substituents or protonation is shown to significantly alter the spectroscopic and electronic properties of these remarkably stable π-systems. Their exceptional optical properties, such as high fluorescence quantum yields combined with a redox-active behaviour, make them promising candidates for sensor materials. Additional marked features in the solid state, such as herringbone packing in combination with short π-π distances, will open access to electronic materials. 相似文献
79.
Gradhand M Fedorov DV Pientka F Zahn P Mertig I Gy?rffy BL 《J Phys Condens Matter》2012,24(21):213202
Recent progress in wave packet dynamics based on the insight of Berry pertaining to adiabatic evolution of quantum systems has led to the need for a new property of a Bloch state, the Berry curvature, to be calculated from first principles. We report here on the response to this challenge by the ab initio community during the past decade. First we give a tutorial introduction of the conceptual developments we mentioned above. Then we describe four methodologies which have been developed for first-principle calculations of the Berry curvature. Finally, to illustrate the significance of the new developments, we report some results of calculations of interesting physical properties such as the anomalous and spin Hall conductivity as well as the anomalous Nernst conductivity and discuss the influence of the Berry curvature on the de Haas-van Alphen oscillation. 相似文献
80.
Oleksandr Stroyuk Alexandra Raevskaya Felix Spranger Prof. Nikolai Gaponik Prof. Dietrich R. T. Zahn 《Chemphyschem》2019,20(12):1640-1648
The temperature dependence of the photoluminescence (PL) intensity of colloidal semiconductor nanocrystals (NCs) makes them an appealing option in bio-sensing applications. Here, we probed the temperature-dependent PL behavior of aqueous glutathione (GSH)-capped Ag−In−S (AIS) NCs and their core/shell AIS/ZnS heterostructures. We show that both core and core-shell materials reveal strong PL quenching upon heating from 10 to 80 °C, which is completely reversible upon cooling. The PL quenching is assigned to the thermally activated dissociation of complexes formed by ligands with the metal cations on the NC surface and the introduction of water into the NC coordination sphere. This unique mechanism of the thermal PL quenching results in a much higher temperature sensitivity of the aqueous colloidal AIS (AIS/ZnS) NCs as compared with previously reported analogs capped by covalently bound ligands. Our results are expected to stimulate further studies on aqueous ternary NCs as colloidal luminescent nano-thermometers applicable for ratiometric temperature sensing. 相似文献