Femtosecond vibrational dynamics of self-trapping in a quasi-one-dimensional system

We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system [Pt(en)(2)] [Pt(en)2Br2];(PF6)(4) ( en = ethylene-diamine, C2H8N2), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at approximately 110 cm(-1) accompanies the formation of the self-trapped exciton on a approximately 200 fs time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.     

Gap detection for similar and dissimilar gap markers

Detection thresholds for temporal gaps between markers of dissimilar frequency are usually elevated with respect to thresholds for gaps between markers of similar frequency. Because gaps between markers of dissimilar frequency represent both a spectrally based perceptual discontinuity as well as a temporal discontinuity, it is not clear what factors underlie the threshold elevation. This study sought to examine the effects of perceptual dissimilarities on gap detection. The first experiment measured gap detection for configurations of narrow-band gap markers comprised of pure tones, frequency-modulated tones, and amplitude-modulated tones. The results showed that gap thresholds for frequency-disparate pure-tone markers were elevated with respect to isofrequency tonal markers, but that perceptual discontinuities between markers restricted to the same frequency region did not uniformly elevate threshold. The second experiment measured gap detection for configurations of markers where the leading and trailing markers could differ along the dimensions of bandwidth, duration, and pitch. The results showed that, in most cases, gap detection deteriorated when the bandwidth of the two markers differed, even when the spectral content of the narrower-band marker was completely subsumed by the spectral content of the wider-band marker. This finding suggests that gap detection is sensitive to spectral dissimilarity between markers in addition to spectral discontinuity. The effects of marker duration depended on the marker bandwidth. Pitch differences across spectrally similar markers had no effect.     

Miniaturized reference electrodes with stainless steel internal reference elements

Stable reference electrodes have previously been obtained by immersion of a stainless steel internal reference element (SSIRE) in a solution of steady pH, e.g., a stainless steel wire maintained in 2 mol/l HCl. Here, we report the miniaturization of this regular size reference half-cell by embedding thermally activated SSIREs in a copolymer matrix of a fixed and constant pH value. The resulting electrode is based on a polymer volume of 1-5 μl, while its contact area at the polymer/analyte solution interface is 0.4 mm². Photopolymerized acrylic type hydrogel is used as the copolymer which contains a quaternary ammonium salt as the supporting electrolyte. These miniaturized reference electrodes show potential stability over the pH range of 1-13, maintain a constant potential value over the time, and are suitable for potentiometric and voltammetric measurements in both aqueous and organic media. Furthermore, they do not exhibit leakage problems. Hence, they do not contaminate the analytical sample, even when the reference electrodes (REs) are used in very small volumes and over extended period.     

Spectral Asymptotics for Higher-Order Ordinary Differential Equations

This paper gives one-term componentwise asymptotics for theM and spectral matrices of a self-adjoint realisation of aneven-order ordinary differential expression. The underlyinginterval is assumed to have at least one regular endpoint, andthe boundary conditions are supposed to be separated. Furthermore,the weight function and the reciprocal of the highest-ordercoefficient are supposed to be of regular variation at the regularendpoint, in the sense of Bingham, Goldie and Teugels. 1991Mathematics Subject Classification: 34B24, 34E05.