Onset of motion and dynamic reordering of a vortex lattice.

Time resolved transport measurements on a driven vortex lattice in an undoped 2H-NbSe2 crystal show that the response to a current pulse is governed by healing of defects as the lattice evolves from a stationary to a moving steady state and that the response time reflects the degree of order in the initial vortex state. We find that stationary field cooled vortex lattices become more ordered with decreasing temperature and identify a temperature below which a qualitative change in the response signals the disappearance of topological defects.

Observation of the vortex lattice spinodal in NbSe2.

Metastable superheated and supercooled vortex states in NbSe2 crystals were probed with fast transport measurements over a wide range of field and temperature. The limit of metastability of the superheated vortex lattice defines a line in the phase diagram that lies below the superconducting transition and is clearly separated from it. This line is identified as the vortex lattice spinodal, and is in good agreement with recent theoretical predictions by Li and Rosenstein [Phys. Rev. B 65, 220504 (2002)]; cond-mat/0305258]. By contrast, no limit of metastability is observed for the supercooled disordered state.

Depinning of a metastable disordered vortex lattice.

We report on experiments investigating the depinning dynamics of a strongly pinned vortex lattice in 2H-NbSe2. We find that the depinning process starts at currents that are well below the critical current of the entire lattice and that it is governed by the formation of contiguous channels of mobile vortices connecting the sample edges. We obtain the formation time of the first channel by monitoring the delayed voltage response to a driving current step and by measuring the ramping rate dependence of the critical current. The subsequent increase in the number of moving vortices is determined from the temporal evolution of the voltage response and the critical current.

Equilibration and dynamic phase transitions of a driven vortex lattice.

We report on the observation of two types of current driven transitions in metastable vortex lattices. The metastable states, which are missed in usual slow transport measurements, are detected with a fast transport technique in the vortex lattice of undoped 2H-NbSe2. The transitions are seen by following the evolution of these states when driven by a current. At low currents we observe an equilibration transition from a metastable to a stable state, followed by a dynamic crystallization transition at high currents.

Solid state systems for the potentiometric determination of CO(2).

In a survey of solid state systems for the potentiometric determination of CO(2) their different fundamentals, possibilities and problems are demonstrated. Experimental results are given, obtained from sensors in which Na(2)CO(3) reacts electrochemically with an oxide forming the sodium salt thermodynamically stable in contact with it. Sensors with Na(2)YZr(PO(4)) as solid electrolyte and MoO(3) or SiO(2) did not yield long-term stable signals, probably mainly because of chemical reactions between the oxides and the solid electrolyte. Satisfactory results were obtained with galvanic cells represented by the symbol. Their standard cell tensions U* (= -emf*) determined with different test gases are in relatively good agreement with values thermodynamically calculated.