Quantum Interference of Coulomb Interaction and Disorder: Phase Shift of Friedel Oscillations and an Instability of the Fermi Sea

We investigate the influence of interference between Coulomb interaction and impurity scattering on the static electronic response $\chi (0,q)$ in disordered metals to leading order in the effective Coulomb interaction. When the transport relaxation time $\tau _{tr}$ is much shorter than the quasiparticle life time, we find a \mbox{sgn}(2p_F-q)/\sqrt{|2p_F-q|} divergence of the polarization function at the Fermi surface ($q=2p_F$). It causes a phase shift of the Friedel oscillations as well as an enhancement of their amplitude. Our results are consistent with experiments and may be relevant for understanding the stability of the amorphous state of certain alloys against crystallization.Comment: 11 pages, 4 PostScript figures appended as a self-extracting tar archive; includes output instruction

Two tone response of radiofrequency signals using the voltage output of a Superconducting Quantum Interference Filter

In the presence of weak time harmonic electromagnetic fields, Superconducting Quantum Interference Filters (SQIFs) show the typical behavior of non linear mixers. The SQIFs are manufactured from high-T_c grain boundary Josephson junctions and operated in active microcooler. The dependence of dc voltage output V_dc vs. static external magnetic field B is non-periodic and consists of a well pronounced unique dip at zero field, with marginal side modulations at higher fields. We have successfully exploited the parabolic shape of the voltage dip around B=0 to mix quadratically two external time harmonic rf-signals, at frequencies f_1 and f_2 below the Josephson frequency f_J, and detect the corresponding mixing signal at f_1-f_2. When the mixing takes place on the SQIF current-voltage characteristics the component at 2f_2 - f_1 is present. The experiments suggest potential applications of a SQIF as a non-linear mixing device, capable to operate at frequencies from dc to few GHz with a large dynamic range.Comment: 10 pages, 3 Figures, submitted to J. Supercond. (as proceeding of the HTSHFF Symposium, June 2006, Cardiff

Cochlear Implantation of Bilaterally Deafened Patients with Tinnitus Induces Sustained Decrease of Tinnitus-Related Distress

Objective: Tinnitus is a common symptom of hearing impairment. Patients who are bilaterally hard of hearing are often affected by tinnitus. However, they cannot undergo any of the standard tinnitus therapies, since they rely on hearing. Cochlear implantation (CI) used to treat severe hearing disabilities, such as bilateral hearing loss, was also shown to reduce tinnitus. Our goal was to determine if CI induces sustained reduction of tinnitus. We performed prospective, longitudinal analyses of tinnitus-related distress in a uniform group of bilaterally deafened patients after CI. Patients and Methods: The homogenous sample consisted of 41 patients who met the inclusion criteria and were consecutively included in this study. The impact of unilateral CI on tinnitus-related distress, health-related quality of life (HRQoL), and hearing abilities was studied with validated instruments. The follow-up appointments were scheduled at 6, 12, and 24 months after CI surgery. During the appointments, hearing abilities were estimated with monosyllabic Freiburg test, whereas the tinnitus-related distress, the HRQoL, and the subjective hearing were measured with standard questionnaires [Tinnitus Questionnaire (TQ), Nijmegen Cochlear Implantation Questionnaire, and Oldenburg Inventory, respectively]. Results: Tinnitus-related distress decreased significantly from the mean TQ score of 35.0 (SD = 19.6) prior to surgery to the mean TQ = 27.54 (SD = 20.0) 6 months after surgery and remained sustained low until the end of follow-up period. In addition, CI significantly improved the hearing abilities and the HRQoL of all patients. Conclusion: The results from our prospective study suggest that in a homogenous sample of bilaterally deafened, implanted patients who report having tinnitus prior to surgery, CI alone not only improves the hearing abilities but also significantly reduces the tinnitus- related distress and improves the HRQoL in a sustained way

Nonequilibrium coupled Brownian phase oscillators

A model of globally coupled phase oscillators under equilibrium (driven by Gaussian white noise) and nonequilibrium (driven by symmetric dichotomic fluctuations) is studied. For the equilibrium system, the mean-field state equation takes a simple form and the stability of its solution is examined in the full space of order parameters. For the nonequilbrium system, various asymptotic regimes are obtained in a closed analytical form. In a general case, the corresponding master equations are solved numerically. Moreover, the Monte-Carlo simulations of the coupled set of Langevin equations of motion is performed. The phase diagram of the nonequilibrium system is presented. For the long time limit, we have found four regimes. Three of them can be obtained from the mean-field theory. One of them, the oscillating regime, cannot be predicted by the mean-field method and has been detected in the Monte-Carlo numerical experiments.Comment: 9 pages 8 figure

Hybrid administrative interfaces : authority delegation and reversion in strategic alliances

Steering committees are pivotal for governing complex collaborations by consensus to facilitate coordination and knowledge sharing. Although consensus-based governance promotes mutuality, it can also cause deadlocks, stalling expeditious decision making. We examine the conditions under which alliance partners delegate decision-making authority to steering committees as well as the conditions under which authority over discordant matters can be relocated to one of the alliance partners. We argue that joint coordination concerns increase the likelihood of authority delegation, whereas the higher costs and stakes associated with decision stalemates provide grounds for authority reversion. Empirical analyses of strategic alliances in the biopharmaceutical industry support our arguments. Our paper demonstrates the versatility of contractually defined administrative interfaces in alliance governance, allowing partners to coordinate bilaterally and adapt hierarchically as and when required

Disorder Effects in Superconducting Multiple Loop Quantum Interferometers

A theoretical study is presented on a number N of resistively shunted Josephson junctions connected in parallel as a disordered 1D array by superconducting wiring in such a manner that there are N-1 individual SQUID loops with arbitrary shape formed.Comment: 4 pages, 2 figure