Strain-induced energy band gap opening in two-dimensional bilayered silicon film

This work presents a theoretical study of the structural and electronic properties of bilayered silicon films under in-plane biaxial strain/stress using density functional theory. Atomic structures of the two-dimensional silicon films are optimized by using both the local-density approximation and generalized gradient approximation. In the absence of strain/stress, five buckled hexagonal honeycomb structures of the bilayered silicon film have been obtained as local energy minima and their structural stability has been verified. These structures present a Dirac-cone shaped energy band diagram with zero energy band gaps. Applying tensile biaxial strain leads to a reduction of the buckling height. Atomically flat structures with zero bucking height have been observed when the AA-stacking structures are under a critical biaxial strain. Increase of the strain between 10.7% ~ 15.4% results in a band-gap opening with a maximum energy band gap opening of ~168.0 meV obtained when 14.3% strain is applied. Energy band diagram, electron transmission efficiency, and the charge transport property are calculated.Comment: 18 pages, 5 figures, 1 tabl

Study on the composition optimization method for improving the fluidity of cast Ti2_2AlNb alloy and its mechanism

In this paper, the effects of Al, Nb main elements, Fe, Mo, W, Co, B, Si and their contents on the fluidity of Ti-22Al-25Nb alloy were investigated. The composition that was beneficial to improve the fluidity was screened through the thermodynamic software calculating thermophysical parameters affecting the fluidity of Ti$_2$AlNb alloy, the numerical simulation test of its fluidity and the verification test of the fluidity of optimized alloys. Finally, the improvement mechanism of the alloy fluidity was discussed. Results showed that the appropriate reduction of Nb element was better than Al element for the improvement of fluidity. The addition of trace Fe, B and Si elements were beneficial to the improvement of fluidity, the improvement effect of B element was best, while the addition of trace Mo, W, Co were not conducive to the improvement of fluidity. The cessation mechanism of Ti$_2$AlNb alloy is the cessation mechanism of the alloy with a wide crystallization temperature range. The composition which was most beneficial to improve the fluidity was Ti-22Al-24Nb-0.1B. The main reasons for the improvement of the fluidity had two sides: on the one hand, the reduction of 1at% Nb and the addition of 0.1at% B not only increased the superheat and crystallization latent heat of the alloy, but also reduced the melt viscosity and thermal conductivity, thus improving the fluidity. On the other hand, the TiB phase refined the grains, the fine grains prevented the dendrite from growing into developed dendrite networks, inhibited the adverse effect of the increase in the width of the solidification zone on the fluidity, reduced the flow resistance of the molten metal, and further improved the fluidity of the alloy.Comment: 23 pages, 14 figures, research pape

Stress-Activated Kinase MKK7 Governs Epigenetics of Cardiac Repolarization for Arrhythmia Prevention

BACKGROUND: Ventricular arrhythmia is a leading cause of cardiac mortality. Most antiarrhythmics present paradoxical proarrhythmic side effects, culminating in a greater risk of sudden death. METHODS: We describe a new regulatory mechanism linking mitogen-activated kinase kinase-7 deficiency with increased arrhythmia vulnerability in hypertrophied and failing hearts using mouse models harboring mitogen-activated kinase kinase-7 knockout or overexpression. The human relevance of this arrhythmogenic mechanism is evaluated in human-induced pluripotent stem cell-derived cardiomyocytes. Therapeutic potentials by targeting this mechanism are explored in the mouse models and human-induced pluripotent stem cell-derived cardiomyocytes. RESULTS: Mechanistically, hypertrophic stress dampens expression and phosphorylation of mitogen-activated kinase kinase-7. Such mitogen-activated kinase kinase-7 deficiency leaves histone deacetylase-2 unphosphorylated and filamin-A accumulated in the nucleus to form a complex with Kruppel-like factor-4. This complex leads to Kruppel-like factor-4 disassociation from the promoter regions of multiple key potassium channel genes (Kv4.2, KChIP2, Kv1.5, ERG1, and Kir6.2) and reduction of their transcript levels. Consequent repolarization delays result in ventricular arrhythmias. Therapeutically, targeting the repressive function of the Kruppel-like factor-4/histone deacetylase-2/filamin-A complex with the histone deacetylase-2 inhibitor valproic acid restores K+ channel expression and alleviates ventricular arrhythmias in pathologically remodeled hearts. CONCLUSIONS: Our findings unveil this new gene regulatory avenue as a new antiarrhythmic target where repurposing of the antiepileptic drug valproic acid as an antiarrhythmic is supported.British Heart Foundation [PG/09/052/27833, PG/14/71/31063, PG/12/76/29852, FS/15/16/31477]; Medical Research Council [G1002082, MC_PC_13070]; American Heart Association National Scientist Development Grants [12SDG12070077]; National Basic Research Program of China [2012CB518000]SCI(E)ARTICLE7683-69913

Erratum to: Ventricular assist device implantation improves skeletal muscle function, oxidative capacity, and growth hormone/insulin-like growth factor-1 axis signaling in patients with advanced heart failure

Background: Skeletal muscle dysfunction in patients with heart failure (HF) has been linked to impaired growth hormone (GH)/insulin-like growth factor (IGF)-1 signaling. We hypothesized that ventricular assist device (VAD) implantation reverses GH/IGF-1 axis dysfunction and improves muscle metabolism in HF. Methods: Blood and rectus abdominis muscle samples were collected during VAD implantation and explantation from patients with HF and controls. Clinical data were obtained from medical records, biomarkers measured by enzyme-linked immunosorbent assay (ELISA), and gene expression analyzed by reverse transcription and real-time polymerase chain reaction (RT-PCR). Grip strength was assessed by dynamometry. Oxidative capacity was measured using oleate oxidation rates. Muscle fiber type and size were assessed by histology. Results: Elevated GH (0.27 ± 0.27 versus 3.6 ± 7.7 ng/ml in HF; p = 0.0002) and lower IGF-1 and insulin-like growth factor binding protein (IGFBP)-3 were found in HF (IGF-1, 144 ± 41 versus 74 ± 45 ng/ml in HF, p < 0.05; and IGFBP-3, 3,880 ± 934 versus 1,935 ± 862 ng/ml in HF, p = 0.05). The GH/IGF-1 ratio, a marker of GH resistance, was elevated in HF (0.002 ± 0.002 versus 0.048 ± 0.1 pre-VAD; p < 0.0039). After VAD support, skeletal muscle expression of IGF-1 and IGFBP-3 increased (10-fold and 5-fold, respectively; p < 0.05) accompanied by enhanced oxidative gene expression (CD36, CPT1, and PGC1α) and increased oxidation rates (+1.37-fold; p < 0.05). Further, VAD implantation increased the oxidative muscle fiber proportion (38 versus 54 %, p = 0.031), fiber cross-sectional area (CSA) (1,005 ± 668 versus 1,240 ± 670 μm2, p < 0.001), and Akt phosphorylation state in skeletal muscle. Finally, hand grip strength increased 26.5 ± 27.5 % at 180 days on-VAD (p < 0.05 versus baseline). Conclusion: Our data demonstrate that VAD implantation corrects GH/IGF-1 signaling, improves muscle structure and function, and enhances oxidative muscle metabolism in patients with advanced HF

Investigation on thermal performance of high temperature multilayer insulations for hypersonic vehicles under aerodynamic heating condition

Hypersonic vehicles have to withstand extremely high aerodynamic heating and pressure loads during the ascent and reentry stages. Multilayer thermal insulations have been widely designed in thermal protection systems to keep the temperature of underlying structure within an acceptable limit. In this study, a theoretical model is built combining radiation and conduction heat transfer in high temperature multilayer insulations under aerodynamic heating conditions. After a reliable validation with previous references, the effects of the layout, the number and the location of the foils, the density of insulation materials and the emissivity of the surface of foils on the insulation performance of multilayer thermal insulations are investigated, respectively. It is found that there exists an optimal number of insulation layers for best thermal performance and the layout of radiation foils has no evident effect. In addition, the insulation performance is much better when the foils are near the cold boundary, and when the density of insulation material and the emissivity of the surface of foils are higher, the temperature of bottom surface is lower. (C) 2014 Elsevier Ltd. All rights reserved

Heterologous expression of mlrA gene originated from Novosphingobium sp THN1 to degrade microcystin-RR and identify the first step involved in degradation pathway

Information on the catalytic role of mlrA gene-encoded enzyme (MlrA) in microcystin-RR (MC-RR) biodegradation was limited. This study succeeded in expressing mlrA homolog of Novosphingobium sp. THN1 in heterologous host for the first time, by constructing a recombinant bacterium. Mass spectrometric analysis showed that the recombinant MlrA hydrolyzed MC-RR into linear intermediate product by cleaving the peptide bond between Adda and arginine residue, greatly detoxifying MC-RR. This finding clearly manifested that the MlrA homolog of THN1 strain possesses its original catalytic function, and ring-opening constituted the first step in MC-RR biodegradation pathway of THN1 strain. Moreover, MC-RR degradation by intact recombinant cells and cell-free crude enzyme (CE) from recombinant was compared. Results exhibited that intact recombinant was able to degrade 20 mu g mL(-1) MC-RR more quickly than CE, with the maximum rate of 9.22 mu g mL(-1) h(-1) in the first 8 h. Thus, this study provided new insights on the catalytic activity and roles of MIrA originated from THN1 strain in MC-RR biodegradation process, which lay a foundation for efficiently removing and detoxifying MC-RR, and exploring downstream steps in MC-RR biodegradation pathway of THN1 strain. (C) 2017 Elsevier Ltd. All rights reserved.</p

Research and development of anticancer agents under the guidance of biomarkers

At present, cancer ranks first as the cause of death in the world, necessitating the need to develop new anticancer agents. As a probe, biomarkers can indicate the biological and pharmacological activity of anticancer agents and are thus valuable in predicting their effectiveness during the research and development phase. This paper reviews the research on the biomarker-guided prediction of the efficacy of anticancer agents. We infer that, in the process of the development of anticancer agents, reasonable selection of biomarkers can improve the accuracy of the development of anticancer agents