Nachweis und Bestimmung des Mangans, sowie seine Trennung von anderen Elementen

Ohne Zusammenfassung     

Zum Nachweis, zur Bestimmung und zur Trennung des Arsens

Ohne Zusammenfassung     

ARPES studies of the electronic structure of LaOFe(P, As)

We report a comparison study of LaOFeP and LaOFeAs, two parent compounds of recently discovered iron-pnictide superconductors, using angle-resolved photoemission spectroscopy. Both systems exhibit some common features that are very different from well-studied cuprates. In addition, important differences have also been observed between these two ferrooxypnictides. For LaOFeP, quantitative agreement can be found between our photoemission data and the LDA band structure calculations, suggesting that a weak coupling approach based on an itinerant ground state may be more appropriate for understanding this new superconducting compound. In contrast, the agreement between LDA calculations and experiments in LaOFeAs is relatively poor, as highlighted by the unexpected Fermi surface topology around (π, π). Further investigations are required for a comprehensive understanding of the electronic structure of LaOFeAs and related compounds.     

Effect of the Rate of the Rise in Current on Transient Processes in a Superconducting Fault Current Limiter

The effect of the rate of the rise in the current to 1700 A/ms on the characteristics of a transition of units of superconducting (HTSC) modules from a superconducting to normal state has been experimentally studied. The units differed by the critical current of the HTSC tape and design. The units of HTSC modules are used as a part of the resistive superconducting fault current limiter (SFCL) for ac and dc grids. The obtained dependences should be taken into account when designing a resistive SFCL.     

Vocal Folds Detect Ionic Perturbations on the Luminal Surface: An In Vitro Investigation

The homeostasis of fluid bathing the luminal surface of the vocal folds is important for phonation and laryngeal defense. Dehydration of the respiratory tract during mouth breathing can perturb the concentration of sodium and chloride ions in surface fluid. Exposure to dry air also increases the osmolarity of airway surface fluid. We hypothesized that viable vocal fold epithelium would detect changes in the ionic and osmotic composition of fluid on the luminal surface. Therefore, we examined bioelectric responses of vocal folds exposed to physiologically real, luminal ionic and osmotic challenges in vitro. The study used randomized factorial design with experimental and sham control groups. Fifty native ovine vocal folds were exposed to five challenges (ionic, osmotic, combined ionic-osmotic, and sham) on the luminal surface. Bioelectric measures of potential difference (PD), short-circuit current (I(SC)), and tissue resistance were assessed at prechallenge baseline, during challenge, and after removal of challenge. Ionic and combined ionic-osmotic challenges reduced PD and I(SC) (P<0.01). These reductions depended on the nature of the ionic challenge, were observed within 10 minutes, lasted for the duration of exposure, and were reversible after removal of the challenge. Conversely, sham or osmotic challenge did not alter bioelectric parameters over time (P>0.05). Viable ovine vocal fold epithelia detect ionic perturbations to the luminal surface. This sensitivity to luminal ionic challenge may be necessary to maintain the homeostasis of surface fluid.     

Monitoring thickness deviations in planar multi-layer elastic structures using impedance signatures

In this letter, a low frequency ultrasonic resonance technique that operates in the 20-80-kHz regime is presented that demonstrates detection of thickness changes on the order of +/-10 mum. This measurement capability is a result of the direct correlation between the electrical impedance of an electro-acoustic transducer and the mechanical loading it experiences when placed in contact with a layered elastic structure. The relative frequency shifts of the resonances peaks can be estimated through a simple one-dimensional transmission model. Separate experimental measurements confirm this technique to be sensitive to subtle changes in the underlying layered elastic structure.     

Fluctuations and Correlations of Pure Quantum Turbulence in Superfluid 3He-B

We describe the first measurements of line-density fluctuations and spatial correlations of quantum turbulence in superfluid 3He-B. All of the measurements are performed in the low-temperature regime, where the normal-fluid density is negligible. The quantum turbulence is generated by a vibrating grid. The vortex-line density is found to have large length-scale correlations, indicating large-scale collective motion of vortices. Furthermore, we find that the power spectrum of fluctuations versus frequency obeys a -5/3 power law which verifies recent speculations that this behavior is a generic feature of fully developed quantum turbulence, reminiscent of the Kolmogorov spectrum for velocity fluctuations in classical turbulence.