Density matrix of chaotic quantum systems

The nonequilibrium dynamics in chaotic quantum systems denies a fully understanding up to now, even if thermalization in the long-time asymptotic state has been explained by the eigenstate thermalization hypothesis which assumes a universal form of the observable matrix elements in the eigenbasis of Hamiltonian. It was recently proposed that the density matrix elements have also a universal form, which can be used to understand the nonequilibrium dynamics at the whole time scale, from the transient regime to the long-time steady limit. In this paper, we numerically test these assumptions for density matrix in the models of spins.Comment: 6 pages, 5 figure

Characterization of Al2O3 gate dielectric for graphene electronics on flexible substrates

In this work, we have fabricated parallel-plate capacitor test structures consisting of 35 nm thick Al2O3 dielectric film and graphene as bottom electrode on polyethylene terephthalate (PET) to characterize the electrical properties of the dielectric film for graphene electronics on flexible substrates.It was found out that leakage current density in the Al2O3 film is less than 0.1 mA/cm2 at 5 V, which allows for applying it as a gate dielectric in graphene-based field effect transistors (GFETs) on flexible substrates. Dielectric constant of the Al2O3 film is approx. 7.6, which is close to the bulk value and confirms good quality of the Al2O3 film. Analysis indicates that the measured loss tangent, which is up to 0.2, is governed mainly by the dielectric loss in the Al2O3 and can be associated with defects in Al2O3 and Al2O3/graphene interface. Our results will be used in further development of GFETs on flexible substrates

Superconductivity induced by La doping in Sr1-xLaxFBiS2 system

Through a combination of X-ray diffraction, electrical transport, magnetic susceptibility, and heat capacity measurements, we report the effect of La doping on Sr in the newly discovered SrFBiS2 system. Superconducting transition with critical temperature Tc of 2.8 K, developed from a semiconducting-like normal state, was found in Sr0.5La0.5FBiS2. A strong diamagnetic signal and a clear specific heat anomaly associated with this transition were observed, confirming bulk superconductivity. The upper critical field Hc2(0) was estimated to be 1 Tesla by using the Ginzburg-Landau approach. Our experiments therefore demonstrate that bulk superconductivity can be achieved by electron doping in the SrFBiS2 system.Comment: 4 pages,5 figure

Potential biomarkers of Parkinson’s disease revealed by plasma metabolic profiling

The plasma of Parkinson's disease (PD) patients may contain various altered metabolites associated with the risk or progression of the disease. Characterization of the abnormal metabolic pattern in PD plasma is therefore critical for the search for potential PD biomarkers. We collected blood plasma samples from PD patients and used an LC-MS based metabolomics approach to identify 17 metabolites with significantly altered levels. Metabolic network analysis was performed to place the metabolites linked to different pathways. The metabolic pathways involved were associated with tyrosine biosynthesis, glycerol phospholipid metabolism, carnitine metabolism and bile acid biosynthesis, within which carnitine and bile acid metabolites as potential biomarkers are first time reported. These abnormal metabolic changes in the plasma of patients with PD were mainly related to lipid metabolism and mitochondrial function

A mechanism of glucose tolerance and stimulation of GH1 β-glucosidases

β-Glucosidases are enzymes that hydrolyze β-glycosidic bonds to release non-reducing terminal glucosyl residues from glycosides and oligosaccharides, and thus have significant application potential in industries. However, most β-glucosidases are feedback inhibited by the glucose product, which restricts their application. Remarkably, some β-glucosidases of the glycoside hydrolase (GH) 1 family are tolerant to or even stimulated by glucose. Elucidation of the mechanisms of glucose tolerance and stimulation of the GH1 β-glucosidases will be crucial to improve their application through enzyme engineering. In this study, by comparing the primary and tertiary structures of two GH1 β-glucosidases with distinct glucose dependence, some putative glucose-dependence relevant sites were mutated to investigate their exact roles. Both biochemical and structural characterization of the mutants suggested that some sites at the entrance and middle of the substrate channel regulate the effects of glucose, and the relative binding affinity/preference of these sites to glucose modulates the glucose dependence. A mechanism was therefore proposed to interpret the glucose dependence of GH1 β-glucosidases. This research provides fresh insight into our current understanding of the properties and mechanisms of GH1 β-glycosidases and related enzymes that modulate their activity via feedback control mechanism