Results 1 - 10 of 43492
Results 1 - 10 of 43492. Search took: 0.052 seconds
|Sort by: date | relevance|
[en] We explore how the biochemical substance exchange through tunneling nanotubes (TNTs) affects the functional stability of a multicellular system. We focus on two questions: whether TNTs can either stabilize or destabilize intercellular communication governed by gap junctions (GJs)? and how to determine the threshold at which influence of TNTs destabilize GJ-mediated communication? The goal of this article is to introduce the way in which the concept of pseudospectra can be used to provide the answers.
[en] The coupling effects of quantum wells on band structure are numerically investigated by using the Matlab programming language. In a one dimensional finite quantum well with the potential barrier V_0, the calculation is performed by increasing the number of inserted barriers with the same height V_b, and by, respectively, varying the thickness ratio of separated wells to inserted barriers and the height ratio of V_b to V_0. Our calculations show that coupling is strongly influenced by the above parameters of the inserted barriers and wells. When these variables change, the width of the energy bands and gaps can be tuned. Our investigation shows that it is possible for quantum wells to achieve the desired width of the bands and gaps. (paper)
[en] Achievements in roll-up technique make it possible to fabricate cylindrical tubes of superconducting materials (e. g., Nb) of radius about 500 nm from a planar film of thickness about 50 nm, where the quasi-2-dimensionality of the film is combined with a curvature. The vortex dynamics in open tubes are significantly determined by the curvature of the superconductor at the nano- or microscale as well as by the impact of single and multiple pinning centers. The presence of the pinning centers allows for an efficient control over the threshold value of the transport current (for emergence of vortex dynamics) and the transition magnetic field (separating sparse- and many-vortex regimes). The detection of the tube curvature effects on vortex dynamics stays feasible in the presence of pinning centers.
[en] We study theoretically the dynamical response of a set of solid-state quantum emitters arbitrarily coupled to a single-mode microcavity system. Ramping the matter-field coupling strength in round trips, we quantify the hysteresis or irreversible quantum dynamics. The matter-field system is modeled as a finite-size Dicke model which has previously been used to describe equilibrium (including quantum phase transition) properties of systems such as quantum dots in a microcavity. Here we extend this model to address non-equilibrium situations. Analyzing the system’s quantum fidelity, we find that the near-adiabatic regime exhibits the richest phenomena, with a strong asymmetry in the internal collective dynamics depending on which phase is chosen as the starting point. We also explore signatures of the crossing of the critical points on the radiation subsystem by monitoring its Wigner function; then, the subsystem can exhibit the emergence of non-classicality and complexity
[en] Quantum well (QW) population effects are compared in III-nitride light emitters with different levels of polarity. We show that wider nonpolar active QWs are characterized by increased QW transparency current and a reduced differential optical gain which consequently increases the laser threshold. We also show that high intra-QW recombination rates in nonpolar/semipolar structures make the QW populations strongly non-equilibrium and vulnerable to inhomogeneous QW injection. In the LED regime, structures with a different polarity level reveal different mechanisms of the efficiency droop. In polar structures, the droop is dominated by the electron leakage and is notably affected by the active region ballistic overshoot. The efficiency droop in semipolar/nonpolar structures is dominated by the combined effect of radiative time saturation and non-radiative Auger recombination
[en] This book includes more than 200 abstracts on various aspects of: materials processing and characterization, crystal growth methods, solid-state and crystal technology, development of condensed matter theory and modeling of materials properties, solid-state device physics, nano science and nano technology, heterostructures, superlattices, quantum wells and wires, advanced quantum physics for nano systems
[en] We calculate the non-symmetrized finite-frequency NS-FF noise for a single-level quantum dot connected to reservoirs in the spinless non-interacting case. The calculations are performed within the framework of the Keldysh Green’s function formalism in the wide band approximation limit. We establish the general formula for NS-FF noise for any values of temperature, frequency and bias voltage. The electron transfer processes from one to the other reservoir act via the transmission amplitude and transmission coefficient depending on the energy. By taking the symmetrized version of this expression, we show that our result coincides with the expression of the finite frequency noise obtained by Büttiker using the scattering theory. We also give the explicit analytical expression for the NS-FF noise in the zero temperature limit. Finally, by performing numerical calculations, we discuss the evolution of the NS-FF noise spectrum with varying temperature, dot energy level, and coupling strength to the reservoirs, revealing a large variety of behaviors such as different symmetry properties and changes of sign in the excess noise. (special issue on unsolved problems of noise in physics, biology and technology)