Duality in topological superconductors and topological ferromagnetic insulators in a honeycomb lattice

The ground state of large Hubbard $U$ limit of a honeycomb lattice near half-filling is known to be a singlet $d+id$-wave superconductor. It is also known that this $d+id$ superconductor exhibits a chiral $p+ip$ pairing locally at the Dirac cone, characterized by a $2\mathbb{Z}$ topological invariant. By constructing a dual transformation, we demonstrate that this $2\mathbb{Z}$ topological superconductor is equivalent to a collection of two topological ferromagnetic insulators. As a result of the duality, the topology of the electronic structures for a $d+id$ superconductor is controllable via the change of the chemical potential by tuning the gate voltage. In particular, instead of being always a chiral superconductor, we find that the $d+id$ superconductor undergoes a topological phase transition from a chiral superconductor to a quasi-helical superconductor as the gap amplitude or the chemical potential decreases. The quasi-helical superconducting phase is found to be characterized by a topological invariant in the pseudo-spin charge sector with vanishing both the Chern number and the spin Chern number. We further elucidate the topological phase transition by analyzing the relationship between the topological invariant and the rotation symmetry. Due to the angular momentum carried by the gap function and spin-orbit interactions, we show that by placing $d+id$ superconductors in proximity to ferromagnets, varieties of chiral superconducting phases characterized by higher Chern numbers can be accessed, providing a new platform for hosting large numbers of Majorana modes at edges.Comment: 12 pages, 6 figure

Phenotype-based and Self-learning Inter-individual Sleep Apnea Screening with a Level IV Monitoring System

Purpose: We propose a phenotype-based artificial intelligence system that can self-learn and is accurate for screening purposes, and test it on a Level IV monitoring system. Methods: Based on the physiological knowledge, we hypothesize that the phenotype information will allow us to find subjects from a well-annotated database that share similar sleep apnea patterns. Therefore, for a new-arriving subject, we can establish a prediction model from the existing database that is adaptive to the subject. We test the proposed algorithm on a database consisting of 62 subjects with the signals recorded from a Level IV wearable device measuring the thoracic and abdominal movements and the SpO2. Results: With the leave-one cross validation, the accuracy of the proposed algorithm to screen subjects with an apnea-hypopnea index greater or equal to 15 is 93.6%, the positive likelihood ratio is 6.8, and the negative likelihood ratio is 0.03. Conclusion: The results confirm the hypothesis and show that the proposed algorithm has great potential to screen patients with SAS

Strong Asymmetric Effect of Lattice Mismatch on Epilayer Structure in Metal Thin Film Deposition

We investigate the hetero-epitaxial growth of thin film deposited on a (001) substrate via molecular dynamics simulations, using six fcc transition metals as our modeling systems. By studying the radial distribution function in the film layers, we demonstrate the importance of the sign of lattice mismatch on the layer structure. For positive lattice mismatches, the film favors pseudomorphic growth, whereas for negative mismatches, a sharp transition happens within the first few monolayers of adatoms and the film layers are transformed into the close-packed (111) structure. We propose a way to quantify the compositional percentage of different planar structures in an epilayer, and demonstrate the strong asymmetric effect between the tensile and compressive cases of deposition. How temperature affects the asymmetry is also discussed.Comment: 12 pages, 5 figures, accepted for publication in PR

A Bayesian measurement error model for two-channel cell-based RNAi data with replicates

RNA interference (RNAi) is an endogenous cellular process in which small double-stranded RNAs lead to the destruction of mRNAs with complementary nucleoside sequence. With the production of RNAi libraries, large-scale RNAi screening in human cells can be conducted to identify unknown genes involved in a biological pathway. One challenge researchers face is how to deal with the multiple testing issue and the related false positive rate (FDR) and false negative rate (FNR). This paper proposes a Bayesian hierarchical measurement error model for the analysis of data from a two-channel RNAi high-throughput experiment with replicates, in which both the activity of a particular biological pathway and cell viability are monitored and the goal is to identify short hair-pin RNAs (shRNAs) that affect the pathway activity without affecting cell activity. Simulation studies demonstrate the flexibility and robustness of the Bayesian method and the benefits of having replicates in the experiment. This method is illustrated through analyzing the data from a RNAi high-throughput screening that searches for cellular factors affecting HCV replication without affecting cell viability; comparisons of the results from this HCV study and some of those reported in the literature are included.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS496 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

A comparison of the in- and out-patient referral patterns of four tertiary rheumatology centres in Beijing, Hong Kong, Kaohsiung and Los Angeles

published_or_final_versio

From insulator to quantum Hall liquid at low magnetic fields

We have performed low-temperature transport measurements on a GaAs two-dimensional electron system at low magnetic fields. Multiple temperature-independent points and accompanying oscillations are observed in the longitudinal resistivity between the low-field insulator and the quantum Hall (QH) liquid. Our results support the existence of an intermediate regime, where the amplitudes of magneto-oscillations can be well described by conventional Shubnikov-de Haas theory, between the low-field insulator and QH liquid.Comment: Magneto-oscillations governed by Shubnikov-de Haas theory are observed between the low-field insulator and quantum Hall liqui

Experimental Studies of Low-field Landau Quantization in Two-dimensional Electron Systems in GaAs/AlGaAs Heterostructures

By applying a magnetic field perpendicular to GaAs/AlGaAs two-dimensional electron systems, we study the low-field Landau quantization when the thermal damping is reduced with decreasing the temperature. Magneto-oscillations following Shubnikov-de Haas (SdH) formula are observed even when their amplitudes are so large that the deviation to such a formula is expected. Our experimental results show the importance of the positive magneto-resistance to the extension of SdH formula under the damping induced by the disorder.Comment: 9 pages, 3 figure

A peroxiredoxin cDNA from Taiwanofungus camphorata: role of Cys31 in dimerization

Peroxiredoxins (Prxs) play important roles in antioxidant defense and redox signaling pathways. A Prx isozyme cDNA (TcPrx2, 745 bp, EF552425) was cloned from Taiwanofungus camphorata and its recombinant protein was overexpressed. The purified protein was shown to exist predominantly as a dimer by sodium dodecyl sulfate-polyacrylamide gel electrolysis in the absence of a reducing agent. The protein in its dimeric form showed no detectable Prx activity. However, the protein showed increased Prx activity with increasing dithiothreitol concentration which correlates with dissociation of the dimer into monomer. The TcPrx2 contains two Cys residues. The Cys(60) located in the conserved active site is the putative active peroxidatic Cys. The role of Cys(31) was investigated by site-directed mutagenesis. The C31S mutant (C(31) → S(31)) exists predominantly as a monomer with noticeable Prx activity. The Prx activity of the mutant was higher than that of the corresponding wild-type protein by nearly twofold at 12 μg/mL. The substrate preference of the mutant was H2O2 > cumene peroxide > t-butyl peroxide. The Michaelis constant (K M) value for H2O2 of the mutant was 0.11 mM. The mutant enzyme was active under a broad pH range from 6 to 10. The results suggest a role of Cys(31) in dimerization of the TcPrx2, a role which, at least in part, may be involved in determining the activity of Prx. The C(31) residue does not function as a resolving Cys and therefore the TcPrx2 must follow the reaction mechanism of 1-Cys Prx. This TcPrx2 represents a new isoform of Prx family