Nonlinear transport theory for hybrid normal-superconducting devices

We report a theory for analyzing nonlinear DC transport properties of mesoscopic or nanoscopic normal-superconducting (N-S) systems. Special attention was paid such that our theory satisfies gauge invariance. At the linear transport regime and the sub-gap region where the familiar scattering matrix theory has been developed, we provide confirmation that our theory and the scattering matrix theory are equivalent. At the nonlinear regime, however, our theory allows the investigation of a number of important problems: for N-S hybrid systems we have derived the general nonlinear current-voltage characteristics in terms of the scattering Green's function, the second order nonlinear conductance at the weakly nonlinear regime, and nonequilibrium charge pile-up in the device which defines the electrochemical capacitance coefficients

Anomalous Thermal Transport of SrTiO3_3 Driven by Anharmonic Phonon Renormalization

SrTiO$_3$ has been extensively investigated owing to its abundant degrees of freedom for modulation. However, the microscopic mechanism of thermal transport especially the relationship between phonon scattering and lattice distortion during the phase transition are missing and unclear. Based on deep-potential molecular dynamics and self-consistent \textit{ab initio} lattice dynamics, we explore the lattice anharmonicity-induced tetragonal-to-cubic phase transition and explain this anomalous behavior during the phase transition. Our results indicate the significant role of the renormalization of third-order interatomic force constants to second-order terms. Our work provides a robust framework for evaluating the thermal transport properties during structural transformation, benefitting the future design of promising thermal and phononic materials and devices

Detection of small single-cycle signals by stochastic resonance using a bistable superconducting quantum interference device

We propose and experimentally demonstrate detecting small single-cycle and few-cycle signals by using the symmetric double-well potential of a radio frequency superconducting quantum interference device (rf-SQUID). We show that the response of this bistable system to single- and few-cycle signals has a non-monotonic dependence on the noise strength. The response, measured by the probability of transition from initial potential well to the opposite one, becomes maximum when the noise-induced transition rate between the two stable states of the rf-SQUID is comparable to the signal frequency. Comparison to numerical simulations shows that the phenomenon is a manifestation of stochastic resonance.Comment: 5 pages 3 figure

Detection and toxicity evaluation of pyrrolizidine alkaloids in medicinal plants Gynura bicolor and Gynura divaricata collected from different Chinese locations

Two edible plants in Southeast Asia, Gynura bicolor and G.divaricata, are not only known to be nutritive but also useful as medicinal herbs. Previous phytochemical investigation of Gynura species showed the presence of hepatotoxic pyrrolizidine alkaloids (PAs), indicating the toxic risk of using these two plants. The present study was designed to analyze the distribution of PA components and tried to evaluate the preliminary toxicity of these two Gynura species. Eight samples of G.bicolor and G.divaricata from five different Chinese locations were collected and their specific PAs were qualitatively characterized by applying an UPLC/MS/MS spectrometry method. Using a pre-column derivatization HPLC method, the total retronecine ester-type PAs in their alkaloids extracts were quantitatively estimated as well. Finally, their genotoxicity was investigated with an effective high-throughput screening method referred to as Vitotox test and their potential cytotoxicity was tested on HepG2 cells. It was found that different types of PAs were widely present in Gynura species collected from south of China. Among them, no significant genotoxic effects were detected with serial concentrations through the present invitro assay. However, the cytotoxicity assay of Gynura plants collected from Jiangsu displayed weak activity at the concentration of 100mg/ml. It is important to note that this research validates in part the indication that the use of Gynura species requires caution

Advances in the application of action learning in nursing practice

AbstractIn this paper, we elucidate the concept and characteristics of action learning as well as summarize the reflexivity, cooperativeness, and subjectivity of this approach. Furthermore, we describe the effects and limitations of action learning when applied in nursing management, nursing education, and clinical practice, among various fields

Landau-Zener-St\"{u}ckelberg Interference of Microwave Dressed States of a Superconducting Phase Qubit

We present the first observation of Landau-Zener-St\"{u}ckelberg (LZS) interference of the dressed states arising from an artificial atom, a superconducting phase qubit, interacting with a microwave field. The dependence of LZS interference fringes on various external parameters and the initial state of the qubit agrees quantitatively very well with the theoretical prediction. Such LZS interferometry between the dressed states enables us to control the quantum states of a tetrapartite solid-state system with ease, demonstrating the feasibility of implementing efficient multipartite quantum logic gates with this unique approach.Comment: 6 pages, 3 figures To appear in Physical Review B(R