Gauge Fixing for Logarithmic Connections Over Curves and the Riemann-Hilbert Problem

Let be a compact Riemann surface of genus g, X={x₁, ..., x_n} a finite set of points, and ¹(log X) be the sheaf of 1-forms,holomorphic over \X and generated near x_j by dz_j/z_j for a coordinatez_j centred at x_j.     

Einige Versuche mit Silicium als Reduktionsmittel in der organischen Chemie

Ohne Zusammenfassung     

Electron-energy bands in single-crystalline La-intercalated graphite

A graphite-intercalation compound (GIC) of La was prepared by a thermally induced surface reaction of a metallic La film on a graphite (0001) substrate. The LEED pattern shows a characteristic (√3 × √3) R30° reconstruction pointing to the formation of LaC₆. Angleresolved photoemission combined with Fermi-surfaces mapping reveals a strongly anisotropic electronic bandstructure of La-GIC. The unfolded π-symmetry graphitederived bands in the La intercalation compound may be described in good approximation within a simple rigidband model by charge transfer from La to graphite. Despite the presence of filled La-5d states large photoemission intensities close to the Fermi level around the K-points of the nonreconstructed Brillouin zone are related to carbon-derived p_π*-bands, which become partly occupied in the GIC.     

Ipsilateral masking between acoustic and electric stimulations

Residual acoustic hearing can be preserved in the same ear following cochlear implantation with minimally traumatic surgical techniques and short-electrode arrays. The combined electric-acoustic stimulation significantly improves cochlear implant performance, particularly speech recognition in noise. The present study measures simultaneous masking by electric pulses on acoustic pure tones, or vice versa, to investigate electric-acoustic interactions and their underlying psychophysical mechanisms. Six subjects, with acoustic hearing preserved at low frequencies in their implanted ear, participated in the study. One subject had a fully inserted 24 mm Nucleus Freedom array and five subjects had Iowa/Nucleus hybrid implants that were only 10 mm in length. Electric masking data of the long-electrode subject showed that stimulation from the most apical electrodes produced threshold elevations over 10 dB for 500, 625, and 750 Hz probe tones, but no elevation for 125 and 250 Hz tones. On the contrary, electric stimulation did not produce any electric masking in the short-electrode subjects. In the acoustic masking experiment, 125-750 Hz pure tones were used to acoustically mask electric stimulation. The acoustic masking results showed that, independent of pure tone frequency, both long- and short-electrode subjects showed threshold elevations at apical and basal electrodes. The present results can be interpreted in terms of underlying physiological mechanisms related to either place-dependent peripheral masking or place-independent central masking.     

Speech recognition in noise for cochlear implant listeners: benefits of residual acoustic hearing

The purpose of this study was to explore the potential advantages, both theoretical and applied, of preserving low-frequency acoustic hearing in cochlear implant patients. Several hypotheses are presented that predict that residual low-frequency acoustic hearing along with electric stimulation for high frequencies will provide an advantage over traditional long-electrode cochlear implants for the recognition of speech in competing backgrounds. A simulation experiment in normal-hearing subjects demonstrated a clear advantage for preserving low-frequency residual acoustic hearing for speech recognition in a background of other talkers, but not in steady noise. Three subjects with an implanted "short-electrode" cochlear implant and preserved low-frequency acoustic hearing were also tested on speech recognition in the same competing backgrounds and compared to a larger group of traditional cochlear implant users. Each of the three short-electrode subjects performed better than any of the traditional long-electrode implant subjects for speech recognition in a background of other talkers, but not in steady noise, in general agreement with the simulation studies. When compared to a subgroup of traditional implant users matched according to speech recognition ability in quiet, the short-electrode patients showed a 9-dB advantage in the multitalker background. These experiments provide strong preliminary support for retaining residual low-frequency acoustic hearing in cochlear implant patients. The results are consistent with the idea that better perception of voice pitch, which can aid in separating voices in a background of other talkers, was responsible for this advantage.     

The Epitaxial Orientation of Al on Si

It is shown that the epitaxial growth of Al on Si {111} favours the epitaxial relation {111} Si ‖ {100} Al; 〈110〉 Si ‖ 〈110〉 Al instead of the more expected relation {111} Si ‖ {111} Al; 〈110〉 Si ‖ 〈110〉 Al. The elastic energy density of the epitaxial layer in the first case mounts to about 40% of that belonging to the second relation. The calculation of the elastic energy density in both cases is based on the assumption of pseudomorphical epitaxial film overgrowth between deposit and substrate supercells.