An equivalent expression of Z2 Topological Invariant for band insulators using Non-Abelian Berry's connection

We introduce a new expression for the Z2 topological invariant of band insulators using non- Abelian Berry's connection. Our expression can identify the topological nature of a general band insulator without any of the gauge fixing problems that plague the concrete implementation of previous invariants. The new expression can be derived from the "partner switching" of the Wannier function center during time reversal pumping and is thus equivalent to the Z2 topological invariant proposed by Kane and Mele.Comment: 14 pages, 8 figure

First-principles design of ferromagnetic monolayer MnO2_2 at the complex interface

Rapidly increasing interest in low-dimensional materials is driven by the emerging requirement to develop nanoscale solid-state devices with novel functional properties that are not available in three-dimensional bulk phases. Among the well-known low-dimensional systems, complex transition metal oxide interface holds promise for broad applications in electronic and spintronics devices. Herein, intriguing metal-insulator and ferromagnetic-antiferromagnetic transitions are achieved in monolayer MnO$_2$ that is sandwiched into SrTiO$_3$-based heterointerface systems through interface engineering. By using first-principles calculations, we modeled three types of SrTiO$_3$-based heterointerface systems with different interface terminations and performed a comparative study on the spin-dependent magnetic and electronic properties that are established in the confined MnO$_2$ monolayer. First-principles study predicts that metal-insulator transition and magnetic transition in the monolayer MnO$_2$ are independent on the thickness of capping layers. Moreover, 100$\%$ spin-polarized two-dimensional electron gases accompanied by robust room temperature magnetism are uncovered in the monolayer MnO$_2$. Not only is the buried MnO$_2$ monolayer a new interface phase of fundamental physical interest, but it is also a promising candidate material for nanoscale spintronics applications. Our study suggests interface engineering at complex oxide interfaces is an alternative approach to designing high-performance two-dimensional materials.Comment: 24 pages, 7 figure

Bis­(chloro­acetato-κO)bis(trimethyl­silylmethyl)tin(IV)

In the title complex, [Sn(C2H2ClO2)2(C4H11Si)2], the SnIV ion is coordinated in a distorted tetra­hedral environment formed by two O atoms from two monodenate chloro­acetato ligands and two C atoms from two trimethyl silyl ligands. Two further weak intra­molecular Sn⋯O contacts [2.744 (2) and 2.655 (2) Å] are formed by the chloro­acetato ligands

An optimal scaling scheme for DCO-OFDM based visible light communications

DC-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) is widely used in visible light communication (VLC) systems to provide high data rate transmission. As intensity modulation with direct detection (IM/DD) is employed to modulate the OFDM signal, scale up the amplitude of the signal can increase the effective transmitted electrical power whereas more signals are likely to be clipped due to the limited dynamic range of LEDs, resulting in severe clipping distortion. Thus, it is crucial to scale the signal to find a tradeoff between the effective electrical power and the clipping distortion. In this paper, an optimal scaling scheme is proposed to maximize the received signal-to-noise-plus-distortion ratio (SNDR) with the constraint of the radiated optical power in a practical scenario where DC bias is fixed for a desired dimming level. Simulation results show that the system with the optimal scaling factor outperforms that with fixed scaling factor under different equivalent noise power in terms of the bit error ratio (BER) performance

The Mediating Effects of Tolerance on Residents’ Support Toward Tourism Events

The classic social exchange theory associates residents’ level of support toward tourism events with their perceived positive and negative tourism impacts directly. However, the contradictory results reported in the literature suggest that such conceptualization may not fully capture the dynamics of the underlying relationships because the linkages between perceived costs and support are often vague. The purpose of this study is to introduce and investigate the role of tolerance in the formation of residents’ support toward tourism events. Results based on data collected from 296 residents at 6 different tourism events in a southeast capital city indicated that tolerance significantly mediated the relationship between perceived benefits and support, as well as perceived costs and support. Our study provides strong theoretical support and empirical findings for the inclusion of tolerance in evaluating residents’ support toward tourism events

6,6′-Di-tert-butyl-4,4′-dimethyl-2,2′-[1,2-phenyl­enebis(nitrilo­methanylyl­idene)]diphenol

In the title mol­ecule, C30H36N2O2, the dihedral angles between the central benzene ring and the two benzene rings of the butyl­salicylaldimine groups are 14.3 (2) and 40.6 (2)°. There are two strong intra­molecular O—H⋯N hydrogen bonds which form S(6) rings. The crystal studied was a non-merohedral twin with refined components of 0.270 (4) and 0.730 (4)

1,3-Bis[5-(2-pyrid­yl)-1H-tetra­zol-1-yl]propane

The title compound, C15H14N10, is a multidentate ligand obtained by the reaction of 5-(2-pyrid­yl)tetra­zole with 1,3-dibromo­propane. The mol­ecule consists of two 5-(2-pyrid­yl)-1H-tetra­zol-1-yl units connected by a propyl­ene bridge in a U-like conformation. A twofold rotation axis passes through the central C atom

The effects of online game addiction on reduced academic achievement motivation among Chinese college students: the mediating role of learning engagement

IntroductionThe present study aimed to examine the effects of online game addiction on reduced academic achievement motivation, and the mediating role of learning engagement among Chinese college students to investigate the relationships between the three variables.MethodsThe study used convenience sampling to recruit Chinese university students to participate voluntarily. A total of 443 valid questionnaires were collected through the Questionnaire Star application. The average age of the participants was 18.77 years old, with 157 males and 286 females. Statistical analysis was conducted using SPSS and AMOS.Results(1) Chinese college students’ online game addiction negatively affected their behavioral, emotional, and cognitive engagement (the three dimensions of learning engagement); (2) behavioral, emotional, and cognitive engagement negatively affected their reduced academic achievement motivation; (3) learning engagement mediated the relationship between online game addiction and reduced academic achievement motivation

Shuang-Huang-Lian Attenuates Lipopolysaccharide-Induced Acute Lung Injury in Mice Involving Anti-Inflammatory and Antioxidative Activities

Shuang-Huang-Lian (SHL) is a common traditional Chinese preparation extracted from Lonicerae Japonicae Flos, Scutellariae Radix, and Fructus Forsythiae. In this study, we demonstrate the anti-inflammatory and antioxidative effects of SHL on lipopolysaccharide- (LPS-) induced acute lung injury (ALI) in mice. SHL reduced the lung wet/dry weight ratio, lowered the number of total cells in the bronchoalveolar lavage fluid, and decreased the myeloperoxidase activity in lung tissues 6 h after LPS treatment. It also inhibited the overproduction of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) in the bronchoalveolar lavage fluid. Histological studies demonstrated that SHL attenuated LPS-induced interstitial edema, hemorrhage, and the infiltration of neutrophils into the lung tissue. Moreover, SHL could also enhance the superoxide dismutase and catalase activities, increase the reduced glutathione content, and decrease the malondialdehyde content. The present results suggest that SHL possesses anti-inflammatory and antioxidative properties that may protect mice against LPS-induced ALI