Das Laserlöten als Kontaktierungsverfahren für Mikrosensoren

Miniaturized sensor elements (e.g. temperature sensors, flow sensors, gas sensors, humidity sensors, etc.) are frequently carried only by their lead-in wires. Laser soldering provides a possibility to attach relatively thick wires to thin film metallizations on a sensor chip. This paper first discusses theoretical aspects of the dynamic wetting process and the leaching phenomenon. Subsequently, it describes the influence of the substrate material on the soldering parameters (laser power and pulse duration) and analyzes the soldering process by temperature measurements using thin film thermocouples integrated in the soldering pad.     

Nachruf

Ohne Zusammenfassung     

Betriebsführung und Instandhaltung von Wasser- und Wärmekraftwerken vor dem Hintergrund der Veränderungen im Europäischen Elektrizitätsmarkt

Verbund-Elektrizitätserzeugungs-Ges.m.b.H. (VEG) is operating and maintaining the power stations of Donaukraft, Tauernkraft and Verbundkraft since 1. 1. 1997. The new operation and maintenance strategy which is adjust to circumstances of the significant changes in the European electricity market will reduce the operation and maintenance staff of the 46 hydropower stations with a capacity of appr. 6 300 MW and a yearly production of approx. 20 TWh from 1 744 MY (man year) in 1997 to approx. 1 090 MY. The engineering and administration employees will be reduced from 570 MY to 360 MY in the same period.     

Differential regulation of chordin expression domains in mutant zebrafish

Patterning along the dorsal-ventral (D-V) axis of Xenopus and Drosophila embryos is believed to occur through a conserved molecular mechanism, with homologous proteins Chordin and Short gastrulation (Sog) antagonizing signaling by bone morphogenetic protein 4 (BMP-4) and Decapentaplegic (Dpp), respectively. We have isolated a zebrafish gene that is highly homologous to chordin and sog within cysteine-rich domains and exhibits conserved aspects of expression and function. As in Xenopus embryos, zebrafish chordin is expressed in the organizer region and transiently in axial mesoderm. Injection of zebrafish chordin mRNA to the ventral side of Xenopus embryos induced secondary axes. Ectopic overexpression in zebrafish resulted in an expansion of paraxial mesoderm and neurectoderm at the expense of more lateral and ventral derivatives, producing a range of defects similar to those of dorsalized zebrafish mutants (Mullins et al., 1996). In accordance with the proposed function of chordin in D-V patterning, dorsalized zebrafish mutants showed expanded domains of chordin expression by midgastrulation, while some ventralized mutants had reduced expression; however, in all mutants examined, early organizer expression was unaltered. In contrast to Xenopus, zebrafish chordin is also expressed in paraxial mesoderm and ectoderm and in localized regions of the developing brain, suggesting that there are additional roles for chordin in zebrafish embryonic development. Surprisingly, paraxial mesodermal expression of chordin appeared unaltered in spadetail mutants that later lack trunk muscle (Kimmel et al., 1989), while axial mesodermal expression was affected. This finding reveals an unexpected function for spadetail in midline mesoderm and in differential regulation of chordin expression during gastrulation.