Quantum Faraday Effect in Double-Dot Aharonov-Bohm Ring

We investigate Faraday's law of induction manifested in the quantum state of Aharonov-Bohm loops. In particular, we propose a flux-switching experiment for a double-dot AB ring to verify the phase shift induced by Faraday's law. We show that the induced {\em Faraday phase} is geometric and nontopological. Our study demonstrates that the relation between the local phases of a ring at different fluxes is not arbitrary but is instead determined by Faraday's inductive law, which is in strong contrast to the arbitrary local phase of an Aharonov-Bohm ring for a given flux.Comment: Submitted to Phys. Rev. Let

Novel form of adaptation in mouse retinal rods speeds recovery of phototransduction

Photoreceptors of the retina adapt to ambient light in a manner that allows them to detect changes in illumination over an enormous range of intensities. We have discovered a novel form of adaptation in mouse rods that persists long after the light has been extinguished and the rod's circulating dark current has returned. Electrophysiological recordings from individual rods showed that the time that a bright flash response remained in saturation was significantly shorter if the rod had been previously exposed to bright light. This persistent adaptation did not decrease the rate of rise of the response and therefore cannot be attributed to a decrease in the gain of transduction. Instead, this adaptation was accompanied by a marked speeding of the recovery of the response, suggesting that the step that rate-limits recovery had been accelerated. Experiments on knockout rods in which the identity of the rate-limiting step is known suggest that this adaptive acceleration results from a speeding of G protein/effector deactivation

Correlation Assisted Phonon Softenings and the Mott-Peierls Transition in VO2_{2}

To explore the driving mechanisms of the metal-insulator transition (MIT) and the structural transition in VO2, we have investigated phonon dispersions of rutile VO2 (R-VO2) in the DFT and the DFT+U (U : Coulomb correlation) band calculations. We have found that the phonon softening instabilities occur in both cases, but the softened phonon mode only in the DFT+U describes properly both the MIT and the structural transition from R-VO2 to monoclinic VO2 (M1-VO2). This feature demonstrates that the Coulomb correlation effect plays an essential role of assisting the Peierls transition in R-VO2. We have also found from the phonon dispersion of M1-VO2 that M1 structure becomes unstable under high pressure. We have predicted a new phase of VO2 at high pressure that has a monoclinic CaCl2-type structure with metallic nature

Spin Fluctuation Induced Dephasing in a Mesoscopic Ring

We investigate the persistent current in a hybrid Aharonov-Bohm ring - quantum dot system coupled to a reservoir which provides spin fluctuations. It is shown that the spin exchange interaction between the quantum dot and the reservoir induces dephasing in the absence of direct charge transfer. We demonstrate an anomalous nature of this spin-fluctuation induced dephasing which tends to enhance the persistent current. We explain our result in terms of the separation of the spin from the charge degree of freedom. The nature of the spin fluctuation induced dephasing is analyzed in detail.Comment: 4 pages, 4 figure

Kondo Effect and Josephson Current through a Quantum Dot between Two Superconductors

We investigate the supercurrent through a quantum dot for the whole range of couplings using the numerical renormalization group method. We find that the Josephson current switches abruptly from a $\pi$- to a 0-phase as the coupling increases. At intermediate couplings the total spin in the ground state depends on the phase difference between the two superconductors. Our numerical results can explain the crossover in the conductance observed experimentally by Buitelaar \textit{et al.} [Phys. Rev. Lett. \textbf{89}, 256 801 (2002)].Comment: Fig.2 and corresponding text have been changed; Several other small change

The influence of the knowledge-sharing process on technology business incubator performance in Saudi Arabia

In the competitive global market, technology business incubators are considered to be the backbone of the economic development of a country. Technology business incubators are involved in the creation of employment opportunities, boosting the local economy, and commercializing innovative technologies. This research-in-progress will propose a framework for technology business incubators to examine the impact of the knowledge-sharing practices of incubatees on technology business incubator performance both in general and in Saudi Arabia in particular. The key findings of this study will allow technology business incubators to better formulate the incubation process

Effect of Charge Fluctuations on the Persistent Current through a Quantum Dot

We study coherent charge transfer between an Aharonov-Bohm ring and a side-attached quantum dot. The charge fluctuation between the two sub-structures is shown to give rise to algebraic suppression of the persistent current circulating the ring as the size of the ring becomes relatively large. The charge fluctuation at resonance provides transition between the diamagnetic and the paramagnetic states. Universal scaling, crossover behavior of the persistent current from a continuous to a discrete energy limit in the ring is also discussed.Comment: 5 pages, 4 figure

Temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high temperature and high pressure condition

We report the temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high temperature and high pressure condition. The superconducting transition width for the resistivity measurement was about 0.4 K, and the low-field magnetization showed a sharp superconducting transition with a transition width of about 1 K. The resistivity in the normal state roughly followed T^2 behavior with smaller residual resistivity ratio (RRR) of 3 over broad temperature region above 100 K rather than reported T^3 behavior with larger RRR value of ~ 20 in the samples made at lower pressures. Also, the resistivity did not change appreciably with the applied magnetic field, which was different from previous report. These differences were discussed with the microscopic and structural change due to the high-pressure sintering.Comment: 2 pages, 3 figures. Accepted by Physica