Observation of the Holstein shift in high TcT_c superconductors with thermal modulation reflectometry

We use the experimental technique of thermal modulation reflectometry to study the relatively small temperature dependence of the optical conductivity of superconductors. Due to a large cancellation of systematic errors, this technique is shown to a be very sensitive probe of small changes in reflectivity. We analyze thermal modulation reflection spectra of single crystals and epitaxially grown thin films of YBa$_2$Cu$_3$O$_{7-\delta}$ and obtain the ${\alpha_tr}^2F(\omega)$ function in the normal state, as well as the superconductivity induced changes in reflectivity. We present detailed model calculations, based on the Eliashberg-Migdal extension of the BCS model, which show good qualitative and quantitative agreement with the experimental spectra. VSGD.93.12.thComment: 6 pages, figures on request. Revtex, version 2, Materials Science Center Internal Report Number VSGD.93.12.t

Comparison of s- and d-wave gap symmetry in nonequilibrium superconductivity

Recent application of ultrafast pump/probe optical techniques to superconductors has renewed interest in nonequilibrium superconductivity and the predictions that would be available for novel superconductors, such as the high-Tc cuprates. We have reexamined two of the classical models which have been used in the past to interpret nonequilibrium experiments with some success: the mu* model of Owen and Scalapino and the T* model of Parker. Predictions depend on pairing symmetry. For instance, the gap suppression due to excess quasiparticle density n in the mu* model, varies as n^{3/2} in d-wave as opposed to n for s-wave. Finally, we consider these models in the context of S-I-N tunneling and optical excitation experiments. While we confirm that recent pump/probe experiments in YBCO, as presently interpreted, are in conflict with d-wave pairing, we refute the further claim that they agree with s-wave.Comment: 14 pages, 11 figure

Rare and Common Variants Conferring Risk of Tooth Agenesis

We present association results from a large genome-wide association study of tooth agenesis (TA) as well as selective TA, including 1,944 subjects with congenitally missing teeth, excluding third molars, and 338,554 controls, all of European ancestry. We also tested the association of previously identified risk variants, for timing of tooth eruption and orofacial clefts, with TA. We report associations between TA and 9 novel risk variants. Five of these variants associate with selective TA, including a variant conferring risk of orofacial clefts. These results contribute to a deeper understanding of the genetic architecture of tooth development and disease. The few variants previously associated with TA were uncovered through candidate gene studies guided by mouse knockouts. Knowing the etiology and clinical features of TA is important for planning oral rehabilitation that often involves an interdisciplinary approach

The Effect of Simulator Motion Cueing on Steering Control Performance – a Driving Simulator Study

The goal of the presented study was to explore how simulator motion cueing affects the driver’s control performance of a car. We looked at steering behavior as a measure of control performance. The experimental task was a slalom maneuver where the car velocity was limited to 70 km/h. Subjective and objective variables were measured. This paper describes the objective steering behavior. The slalom task was driven in four conditions: a lateral motion scale factor of 1 (one-to-one lateral motion), 0.7, 0.4 and 0 (no-motion), respectively. In total 16 participants completed the experiment. The study showed that the motion condition affects the steering-wheel behavior. The general tendency is that less steering correction took place when the magnitude of the motion cues was increased, which was quantified by two performance indicators. Firstly, the number of steering wheel reversals reduced when the motion-cue magnitude was increased. Secondly, the amount of relative high-frequency correction was reduced with increasing motion cue magnitude. It is concluded that motion feedback can improve the driver’s control performance in an extreme scenario like a slalom maneuver

Differential effects of muscle fibre length and insulin on muscle-specific mRNA content in isolated mature muscle fibres during long-term culture

The aims of this study were (1) to determine the relationship between muscle fibre cross-sectional area and cytoplasmic density of myonuclei in high- and low-oxidative Xenopus muscle fibres and (2) to test whether insulin and long-term high fibre length caused an increase in the number of myonuclei and in the expression of α-skeletal actin and of myogenic regulatory factors (myogenin and MyoD) in these muscle fibres. In high- and low-oxidative muscle fibres from freshly frozen iliofibularis muscles, the number of myonuclei per millimetre fibre length was proportional to muscle fibre cross-sectional area. The in vivo myonuclear density thus seemed to be strictly regulated, suggesting that the induction of hypertrophy required the activation of satellite cells. The effects of muscle fibre length and insulin on myonuclear density and myonuclear mRNA content were investigated on high-oxidative single muscle fibres cultured for 4-5 days. Muscle fibres were kept at a low length (∼15% below passive slack length) in culture medium with a high insulin concentration (∼6 nmol/l: "high insulin medium") or without insulin, and at a high length (∼5% above passive slack length) in high insulin medium. High fibre length and high insulin medium did not change the myonuclear density of isolated muscle fibres during culture. High insulin increased the myonuclear α-skeletal actin mRNA content, whereas fibre length had no effect on α-skeletal actin mRNA content. After culture at high fibre length in high insulin medium, the myonuclear myogenin mRNA content was 2.5-fold higher than that of fibres cultured at low length in high insulin medium or in medium without insulin. Myonuclear MyoD mRNA content was not affected by fibre length or insulin. These in vitro experiments indicate that high muscle fibre length and insulin enhance muscle gene expression but that other critical factors are required to induce adaptation of muscle fibre size and performance. © 2006 Springer-Verlag