Characterization of thin Ta-Si-Nx layers of different nitrogen content using XPS, UPS and STM

Reactively sputtered Ta-Si-N_x barrier systems of different nitrogen content on copper were investigated by photoelectron spectroscopy (XPS, UPS) and scanning tunnelling microscopy (STM). The measured photoelectron spectra (excitation He-I) showed a clear dependence of the electron state density near the Fermi edge on the content of nitrogen. These results correlate with the I(U) characteristics of the STM measurements and the electrical conductivity of these layers.     

Phonons in Ge/Si quantum dot structures: influence of growth temperature

In this paper we present the results of a Raman study of Ge/Si quantum dot (QD) superlattices grown with different thicknesses of a Si interlayer and at different substrate temperatures. The built-in strain and atomic intermixing in the QDs are deduced from an analysis of optical phonon frequencies of the QDs obtained from Raman spectra of the structures.     

Radiation detected resonance ionization spectroscopy on208Tl and242fAm

An ultra-sensitive laser spectroscopic method has been developed for the hyperfine spectroscopy of short-lived isotopes far off stability produced by heavy ion induced nuclear reactions at very weak intensity (> 1/s). It is based on resonance ionization spectroscopy in a buffer gas cell with radiation detection of the ionization process (RADRIS). As a first on-line application of RADRIS optical spectroscopy at^242fAm fission isomers is in progress at the low target production rate of 10/s. The resonance ionization has been performed in two steps utilizing an excimer dye laser combination with a repetition rate of 300 Hz. The first resonant step proceeds through terms which correspond to wavelengths of 466.28, 468.17 or 426.56 nm; the second non-resonant step is achieved with the 351 nm radiation of the excimer laser itself, running with XeF. The frequency scans of the tuneable dye laser at 466.28 and 468.17 nm exhibit broad resonance ionization signals, the latter with a large isotope shift between^242fAm and²⁴³Am which is in accordance with the large quadrupole moment of the^242fAm fission isomer.Work supported by the Bundesministerium für Forschung und Technologie under contract 06 MZ 188 I.     

Magnetic Fluid and Nanoparticle Applications to Nanotechnology

Magnetic field based micro/nanoelectromechanical systems (MEMS/NEMS) devices are proposed that use 10 nm diameter magnetic particles, with and without a carrier fluid, for a new class of nanoduct flows, nanomotors, nanogenerators, nanopumps, nanoactuators, and other similar nanoscale devices. A few examples of macroscopic ferrohydrodynamic instabilities that result in patterns, lines, and structures are shown that can be scaled down to sub-micron dimensions.     

Turbulent Transport in Stellar Interiors

Differential rotation is probably the major cause of turbulence in stably stratified stellar interiors. The boundary of the superficial solar convection zone plays a critical role for both the large scale circulation and the differential rotation. The turbulence arises from the barotropic instability in a vertically stratified medium and is expected to be anisotropic. It tends to suppress one of its causes, namely differential rotation in latitude. It offers an explanation for the thinness of the solar tachocline, the boundary layer beneath the convection zone where solar seismology shows that rotation varies from differential above to apparently uniform below. The anisotropy of turbulence also strongly reduces the efficiency of vertical particle transport. We show that for an anisotropy A of horizontal to vertical velocities, the vertical diffusivity is a factor A ² less than the horizontal diffusivity. Transport by meridional circulation is also reduced, as well as the efficiency of a composition gradient in suppressing meridional circulation. These effects of anisotropy explain the very small upper limit that observations of the concentration of chemical elements impose to vertical transport in stars. However the recent results of helioseismology, that the solar core rotates at nearly the same rate as the whole radiative zone, cannot currently be explained by anisotropic turbulent transport. It suggests the need for an additional transport process such as a magnetic torquing or gravity waves. Furthermore, near the base of the convection zone, magnetic instabilities could provide an alternate mechanism to mix angular momentum preferentially in latitude compared with radial mixing. The quality of the helioseismology data is improving very rapidly. It holds the promise to determine, within the next few years, the velocity field within the Sun to great accuracy. This should allow us to distinguish between the various hydrodynamical and hydromagnetic models. Received 20 May 1997 and accepted 4 January 1998     

The application of homotopy analysis method to solve nonlinear differential equation governing Jeffery–Hamel flow

In this paper Jeffery–Hamel flow has been studied and its nonlinear ordinary differential equation has been solved through homotopy analysis method (HAM). The obtained solution in comparison with the numerical ones represents a remarkable accuracy. The results also indicate that HAM can provide us with a convenient way to control and adjust the convergence region.     

Experimental realization of a model glass former in 2D

We have studied binary two-dimensional (2D) mixtures of superparamagnetic colloidal particles interacting through magnetic dipole moments, which were induced by an external magnetic field B. By tuning B the effective system temperature could be widely adjusted. Time-dependent particle coordinates measured by video-microscopy provide radial pair-distribution functions, mean-square displacements as well as evidence for heterogeneous dynamics. Characteristic features of 3D glass formers are observed experimentally in 2D for the first time.     

Über die Bindung von Vinylsulfon-und Dichlortriazin-Reaktivfarbstoffen an Kollagen

Zusammenfassung Eine aus Rinderachillessehne gewonnene Kollagenfolie wurde mit einem mono-und einem bifunktionellen Vinylsulfonfarbstoff sowie einem Dichlortriazinfarbstoff gefärbt. Als günstigste Reaktivfärbebedingungen für kollagenes Material ergaben sich für Vinylsulfonfarbstoffe pH-Werte von 8–10, bei Färbetemperaturen bis 35°C; der Dichlortriazinfarbstoff reagiert bei 25°C und p_H-Werten ab 7 ausreichend.In Totalhydrolysaten der mit dem Vinylsulfonfarbstoff Remazolbrillantblau R bei p_H-Werten bis 10 und 35° umgesetzten Kollagenfolie konnten Farbstoffderivate von Lysin und Hydroxylysin identifiziert werden. Durch präparative Schichtchromatographie wurde beide Derivate analysenrein isoliert. Damit ist der eindeutige Beweis der kovalenten Bindungsverhältnisse für reaktiv gefärbtes Proteinmaterial erbracht.

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Summary A collagen film was dyed with a monofunctional and bifunctional vinylsulfone dye as well as with a dichlorotriazine dye. The optimum conditions for dyeing the collagen film with vinylsulfone dyes was found to be at p_H 8–10 and temperature 35°C, while with dichlorotriazine dye at p_H 7/35°.In the totalhydrolysate of collagen dyed with Remazolbrillantblue (Farbwerke Hoechst), a monofunctional vinylsulfone dye, at p_H 10 and temperature 35°C, lysine and hydroxylysine derivates were identified. Both the derivates were obtained in the pure form by chromatography. This is the clear evidence of covalent linking of the reactive dye with the protein.

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Mit 7 Abbildungen und 4 Tabellen

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13. Mitteilung über Kollagen. 12. Mitt.:H. Zahn undG. Reinert, Kolloid-Z. u. Z. Polymere; vorstehende Mitt., gleichzeitig 4. Mitteilung über Reaktivität von Aminosäuregruppen. 3. Mitt.:H. Zahn undG. Reinert, Kolloid-Z. u. Z. Polymere (im Druck).

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Teil der Dissertation, TH Aachen 1967.