关键词： HMG box proteins   Fluorescence polarization   Free energy simulation  

摘要： High mobility group box (HMGB) members are DNA binding proteins with varied functions present across kingdoms. The mechanism by which HMGBs with varying number of HMG boxes are able to carry out similar functions, are poorly understood. Moreover, how non-canonical DNAs are recognized by HMGB proteins is not clear. To address these, we carried out detailed biochemical and computational studies to characterize two HMGB members-Kinetoplast associated protein (KAP6) of Trypanosoma and High mobility group protein (HMO1) from yeast. Here, we report that KAP6 binds non-canonical DNAs tighter than B-form DNA. Among non-canonical DNAs, KAP6 has the highest affinity for splayed and flap structures, but least for Holliday Junction (HJ). In contrast, HMO1 binds tighter to HJ. Computational analysis show that the secondary structural elements involved in DNA interaction are conserved in HMGB members KAP6 and mitochondrial transcription factor A. Simulation analyses revealed that the similar to 90 degrees bend in DNA induced by KAP6 HMG box is a result of two similar to 45 degrees bends, by Helix 1 and Helix 2 of the protein. Our data also suggests that the orthologs of HMO1 and KAP6 are oligomers in solution, which could be necessary for their functioning such as DNA bending and looping. (C) 2020 Elsevier B.V. All rights reserved.

关键词： CF3CBrCH2   OH   reaction mechanisms   RRKM  

摘要： Quantum chemical method (CCSD(T)/cc‐pVTZ//M06‐2X/6‐311++G(d,p)) is employed to research the CF3CBrCH2 + OH reaction. The results indicate that the reaction takes place through the interaction of the oxygen atom of the OH radical with the middle C and terminal C atom of CF3CBrCH2 generating adduct IM1 (CF3CBrCH2OH) and IM2 (CF3CBrOHCH2), respectively, and then further dissociation or rearrangement to many products. The rate constants have been computed at 10−10 to 1010 Torr and 200–3000 K by RRKM theory for various product pathways. The results show that at 200–800 K, the rate constant for the production of IM1 (CF3CBrCH2OH) by collisional deactivation is dominant; at high temperatures, the production of P1 (CF3CBrCHOH + H) becomes predominate. The predicted data for CF3CBrCH2 + OH agree closely with available experimental value. The total rate constants are independent on pressure and dependent on temperature. The rate equation can be fitted as k(T) = 1.77 × 10 −7T−0.65exp(−4518.77/T) at 200–300 K, 30 Torr of Ar. The atmospheric lifetime of CF3CBrCH2 in OH is around 2.77 days. TD‐DFT computations imply that IM1, IM2, IM3, IM4, IM5, and IM6 will photolyze under the sunlight.

关键词： 工程机械行业   混凝土机械   工期压缩   量价齐升   动力源   超预期   挖掘机   龙头企业  

摘要： 1不断创新高的工程机械销量2020年5月工程机械销量再超预期。受疫情影响,旺季延后,叠加下游施工工期压缩,旺季自2020年3月开始,挖掘机、混凝土机械、起重机等多种工程机械销量增加,市场温度一度上升。另外,龙头企业陆续发布涨价通知,中国工程机械行业迎来了量价齐升的态势。

关键词： NdMg12 alloy   Hydrogen storage dynamics   Activation energy   Mechanical milling   Ni addition  

摘要： To improve the hydrogenation and dehydrogenation dynamics of NdMg12-type alloy,we replaced part of Mg with Ni in thesamples and used the ball milling method to prepare NdMg11Ni+x wt.%Ni(x=100,200)*** infuences of millingduration and Ni content on the electrochemical and gascous dynamics of the samples were studied in ***-tion activation cnergies of samples were calculated by using Kissinger and Arrhenius *** conclusions show thatthe dynamic properties of samples are significantly enhanced with the increase in Ni *** the change of the miling duration,the gaseous hydrogenation rate and high rate discharging capability reach the maximal ***,thedehydrogenation dynamics of sample alloys are always enhanced with the prolonging of milling *** concretely,prolonging milling duration from 5 to 60 h improves the dehydrogenation ratio of NdMgNi+100 wt.%Ni alloy from58.03%to 64.81%and that of NdMgNi+200 wt.%Ni alloy from 62.20%to 71.59%.Besides,the enhancement of gaseoushydrogen storage dynamics of the samples is believed to be the result of the declined dehydrogenation activation energyresulted from the increase in milling duration and Ni content.

关键词： Quantum correlation   Entanglement   Spin bath   Open systems   (Non-)Markovian dynamics  

摘要： In line with an experimentally feasible protocol was proposed by A. Asadian et al. [ PRL 112, 190402 (2014)],we introduce a pure dephasing model where the interaction of the central qubit with a nano-mechanical resonator is affected by a spin-bath to study the dynamics of resonator-qubit entangled states. We show that how system-bath coupling as well as the coupling among the bath's spins, initial semi-classical states of the phonon as well as the initial states of the bath, modify the entanglement of the system using measures like concurrence. To gain insight into the effect of these correlations, we study the dynamics of the mentioned setup both with and without initial correlations for arbitrary system-environment coupling strengths. It is also shown that stable entanglement, which is dependent on correlated initial states of the system-bath, their coupling strength, and bath temperature, occurs even in the presence of decoherence.

关键词： Microwave heating   Diffusion kinetic   Young's modulus   Nanoindentation   316L   Boriding  

摘要： In this study, the effect of microwave heating on boride formation and diffusion kinetics in 316L stainless steel alloys was investigated. Boriding was carried out in microwave furnace with 2.9 kW power and 2.45 GHz frequency. Four different boriding temperatures (800, 850, 900 and 950 degrees C) were used. Boriding was performed for 2, 4 and 6 h for each temperature. Boron layer thicknesses of boride layers were determined by optical microscope. SEM images were taken from the cross sections of the borided samples. Boron activation energy was determined as 244.15 kJ/mol in microwave environment. Two times thicker boride layer was obtained by microwave boriding process compared to the conventional heating process. The mechanical properties of the boride layers formed by microwave boriding (Young's modulus, hardness, yield strength, residual thermal stress) were determined by nanoindentation tests.

关键词： Superhydrophobicity   Reynolds shear stress   Viscous shear stress   Blood damage   Turbulence  

摘要： Objective: The objective of this study is to evaluate the impact of superhydrophobic coating on the hemodynamics and turbulence characteristics of a bileaflet mechanical valve in the context of evaluating blood damage potential. Methods: Two 3D printed bileaflet mechanical valves were hemodynamically tested in a pulse duplicator under physiological pressure and flow conditions. The leaflets of one of the two valves were sprayed with a superhydrophobic coating. Particle Image Velocimetry was performed. Pressure gradients (PG), effective orifice areas (EOA), Reynolds shear stresses (RSS) and instantaneous viscous shear stresses (VSS) were calculated. Results: (a) Without SH coating, the PG was found to be 14.53 +/- 0.7 mmHg and EOA 1.44 +/- 0.06 cm2. With coating, the PG obtained was 15.21 +/- 1.7 mmHg and EOA 1.39 +/- 0.07 cm(2);(b) during peak systole, the magnitude of RSS with SH coating (110Pa) exceeded that obtained without SH coating (40 Pa) with higher probabilities to develop higher RSS in the immediate wake of the leaflet;(c) The magnitudes range of instantaneous VSS obtained with SH coating were slightly larger than those obtained without SH coating (7.0 Pa versus 5.0 Pa). Conclusion: With Reynolds Shear Stresses and instantaneous Viscous Shear Stresses being correlated with platelet damage, SH coating did not lead to their decrease. While SH coating is known to improve surface properties such as reduced platelet or clot adhesion, the relaxation of the slip condition does not necessarily improve overall hemodynamic performance for the bileaflet mechanical valve design.

关键词： Molecular dynamics   Nano-composite   Mechanical properties   Free volume  

摘要： The cross-linked model of SiO2 and polyimide (SiO2-PI) was constructed through molecular dynamics simulation, and the mixture model of SiO2 and PI (SiO2/PI) was also constructed for comparative analysis. The SiO2-PI model was constructed at the atomistic level to simulate the real polymerization procedure. By comparing the radial distribution function and interaction energy of the two models, covalent bonds have been formed and the reliability of the cross-linked model was confirmed. The mechanical properties of the two materials are calculated by the molecular dynamics and the improvement in mechanical properties has shown after the cross-linking. This improvement in the mechanical properties of the materials is analyzed theoretically with the conclusions of morphology and interaction energy. By comparing with similar materials, the results obtained in this paper are convincing. Thus, the cross-linked model can provide theoretical guidance for the improvement in the material properties.

关键词： curing kinetics   MWCNT   nanocomposites   oxidation  

摘要： In this work, multiwalled carbon nanotubes (MWCNT) were oxidized in a mixture of sulfuric and nitric acid (3:1 v/v) using two distinct times (9 and 18 hours). The effects of different oxidation levels and concentrations of MWCNT on curing kinetics, thermal, and mechanical properties of bisphenol A diglycidyl ether nanocomposites were studied. The nanocomposites were produced usingin situpolymerization technique at two different volume fractions (0.15% and 0.50% v/v) without using solvents. X-ray photoelectron spectroscopy results indicated that MWCNT were in fact oxidized and just 9 hours of acid treatment showed a greater amount of oxygen on the MWCNT surfaces. Results of differential scanning calorimetry and dynamic mechanical analysis showed small variations in the glass transition temperatures of the nanocomposites, indicating alterations in the quality of the interphase matrix/carbon nanotubes. Concerning the thermogravimetric analysis results, the most thermally stable samples were those containing 0.15% v/v of pristine and 18 hours of oxidized MWCNT, which also had the highest stiffness of all nanocomposites. Finally, the cure kinetics of nanocomposites is fairly represented by Kamal and Sourour's semiempirical model with an autocatalytic behavior at 100 degrees C and 120 degrees C, but decelerated at 140 degrees C.

关键词： Yttria-stabilized zirconia   Mechanical properties   Molecular dynamics simulations   Chemical reactions  

摘要： Yttria-stabilized zirconia (YSZ) used as the electrolyte in solid oxide fuel cells usually relies on the complicated chemical reactions at an extremely high temperature. In this paper, the impact of the reaction on the mechanical properties of YSZ is investigated with the aid of reactive force-field (ReaxFF) molecular dynamics simulations. The obtained results show that before the reaction, the intrinsic Young's modulus of YSZ is almost independent of the crystal orientation, while different Poisson's ratios are detected in different crystal orientations. After the reaction, both Young's modulus and Poisson's ratio of YSZ are greatly reduced, since the oxygen in the surface can be deboned and thus escapes from YSZ. Specifically, the largest difference of the mechanical properties before and after the reaction is observed in [111]-oriented YSZ, since it has a unique zigzag surface structure. A decrease of Young's modulus and Poisson's ratio is also observed in YSZ with increasing the temperature and the doping concentration, though the reduction in the mechanical properties is different in different crystal orientations. Based on the obtained simulation results, predictive equations were proposed for quickly predicting the Young's modulus and the Poisson's ratio of YSZ at different temperatures and with different doping concentrations.