Electronic and optical properties of graphane, silicane, MoS 2 homo-bilayers and hetero-bilayers

Abstract(#br)The electronic and optical properties of graphane, silicane and MoS 2 bilayers, as well as the graphane/MoS 2 and silicane/MoS 2 hetero-bilayers, are calculated by the first-principles method. The interlayer interactions of all the bilayer systems are shown to be mainly van der Waals. Both the graphane/MoS 2 and silicane/MoS 2 hetero-bilayers belong to the type-II heterostructure, which can be utilized in photo-voltaic devices due to the efficient spatial separation of electrons and holes. For optical properties, the distinctions for the imaginary parts of the dielectric function ε 2 ( ω ) between the monolayer and bilayer systems for both the graphane and silicane are more evident in electric vector E|| z. However, the differences between ε 2 ( ω ) of the monolayer and bilayer MoS 2 materials are more significant in E|| x. Broader light absorption ranges of the hetero-bilayers are reached, which can also improve the charge separation of the electron-hole pairs

Strain-tunable band gap of hydrogenated bilayer graphene

National Natural Science Foundation of China [10702056, 10774124]; Xiamen University; Academic Award for Doctoral Candidates of ChinaFirst-principles calculations have been utilized to investigate the biaxial strain-dependent electronic properties of fully hydrogenated bilayer graphene. It has been found that after complete hydrogenation, bilayer graphene exhibits semiconducting characteristics with a wide direct band gap. The band gap can be tuned continuously by the biaxial strain. Furthermore, compressive strain can induce the semiconductor-to-metal transition of this hydrogenated system. The origin of the strain-tunable band gap is discussed. The present study suggests the possibility of tuning the band gap of fully hydrogenated bilayer graphene by using mechanical strain and may provide a promising approach for the fabrication of electromechanical devices based on bilayer graphene

A superconducting nanowire photon number resolving four-quadrant detector-based Gigabit deep-space laser communication receiver prototype

Deep space explorations require transferring huge amounts of data quickly from very distant targets. Laser communication is a promising technology that can offer a data rate of magnitude faster than conventional microwave communication due to the fundamentally narrow divergence of light. This study demonstrated a photon-sensitive receiver prototype with over Gigabit data rate, immunity to strong background photon noise, and simultaneous tracking ability. The advantages are inherited from a joint-optimized superconducting nanowire single-photon detector (SNSPD) array, designed into a four-quadrant structure with each quadrant capable of resolving six photons. Installed in a free-space coupled and low-vibration cryostat, the system detection efficiency reached 72.7%, the detector efficiency was 97.5%, and the total photon counting rate was 1.6 Gcps. Additionally, communication performance was tested for pulse position modulation (PPM) format. A series of signal processing methods were introduced to maximize the performance of the forward error correction (FEC) code. Consequently, the receiver exhibits a faster data rate and better sensitivity by about twofold (1.76 photons/bit at 800 Mbps and 3.40 photons/bit at 1.2 Gbps) compared to previously reported results (3.18 photon/bit at 622 Mbps for the Lunar Laser Communication Demonstration). Furthermore, communications in strong background noise and with simultaneous tracking ability were demonstrated aimed at the challenges of daylight operation and accurate tracking of dim beacon light in deep space scenarios

Effects of Na-substitution on structural and electronic properties of Li2CoSiO4 cathode material

Na-substituted dilithium orthosilicate Li2CoSiO4 was investigated by performing density functional theory calculations within the GGA+U framework. The effects of Na-substitution on the electronic structures and structural properties of Li2CoSiO4 were presented. The results show that the Na-substitution on Li sites in Li2CoSiO4 induces a lowering of the conduction bands and a narrowing of the band gap, which could be helpful for enhancing the electronic conductivity. On the other hand, the Na-substitution on the Li ions in Li2CoSiO4 leads to the expansion of interlayer space of the adjacent corrugated layers. This lattice expansion effect would benefit the Li ion diffusion.National Basic Research Program of China [2007CB209702]; National Natural Science Foundation of China [10774124, 20473068

Multimolecular complex of Par-4 and E2F1 binding to Smac promoter contributes to glutamate-induced apoptosis in human- bone mesenchymal stem cells

Neural cells undergo glutamate-induced apoptosis in ischaemic brain tissue, in which prostate apoptosis response-4 gene (Par-4) is involved. Human-bone mesenchymal stem cells can be utilized as an effective therapy for ischemic brain injury. In this study, we found that glutamate could induce apoptosis in human-bone mesenchymal stem cells, accompanied by increased expression of Par-4 gene and Smac release from mitochondria. Repressing Par-4 expression attenuated the glutamate-induced apoptosis. Both Par-4 protein and E2F1 protein could bind to E2F1-binding BS3 site on Smac promoter and participated in the formation of a proteins-DNA complex. Moreover, in the complex, E2F1, not Par-4, was found to be directly bound to the Smac promoter, suggesting that Par-4 exerted indirectly its transcriptional control on the Smac gene though interacting with E2F1. Expression of full-length Par-4 in human-bone mesenchymal cells resulted in increased activity of the Smac promoter. In addition, the indirect transcripional regulation of Par-4 on Smac depended on its COOH terminus-mediated interaction between Par-4 and E2F1. We conclude that the formation of proteins–DNA complex, containing Par-4 protein, E2F1 protein and the Smac promoter, contributes to the pro-apoptotic effect on glutamate-treated human-bone mesenchymal stem cells

How to design high quality acupuncture trials—a consensus informed by evidence

An international panel including patients, clinicians, researchers, acupuncture and surgery trialists, statisticians, and experts in clinical epidemiology and methodology have developed new guidance for randomised controlled trials in acupuncture. It addresses the most prevalent and critical concerns of current acupuncture trials and will help funding agencies, trial registers, and journal editors to evaluate the relevance, importance, and quality of submitted trial proposals and completed trial