Influence of Li^(+)/Al^(3+) on the corrosion behavior of Li-Al layered double hydroxides(LDHs) film on LA51 magnesium alloys

A hierarchical superhydrophobic Al-Li layered double hydroxide(LDH)films with different Li^(+)/Al^(3+)molar ratios of 1:1,1:2,2:1,p H value of 11.5 and reaction temperature of 125°C,have been fabricated on the surface of Mg-5Li-1Al(LA51)alloys by hydrothermal method following the characteristics of controllable cation structure and exchangeable anion between layers.The properties of the films were investigated by X-ray diffractometer(XRD),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).XRD and SEM results indicate that the Al-Li LDH films are successfully prepared on LA51 alloys.The contact angle(CA)was measured to be about100.7°,indicating that the surface wettability of the film converted from hydrophilic to hydrophobic by surface modification.The corrosion resistance of Al-Li LDH films was evaluated by Tafel polarization curve and electrochemical impedance spectroscopy(EIS).Surprisingly,Tafel polarization curve and EIS test reveal that the Al-Li LDH films prepared at the molar ratio of Li^(+)/Al^(3+)1:2,p H 11.5 and temperature125°C have better corrosion resistance in 0.1 M Na Cl neutral solution.In addition,the formation mechanism and corrosion mechanism of the films on the surface of LA51 alloy are also proposed.It provides innovative synthetic materials and novel design ideas for the preparation of high-efficiency anti-corrosion coatings on LA51 alloys,whose application can be extended in industrial fields.

IMPULSIVE EXPONENTIAL SYNCHRONIZATION OF FRACTIONAL-ORDER COMPLEX DYNAMICAL NETWORKS WITH DERIVATIVE COUPLINGS VIA FEEDBACK CONTROL BASED ON DISCRETE TIME STATE OBSERVATIONS

This article aims to address the global exponential synchronization problem for fractional-order complex dynamical networks(FCDNs)with derivative couplings and impulse effects via designing an appropriate feedback control based on discrete time state observations.In contrast to the existing works on integer-order derivative couplings,fractional derivative couplings are introduced into FCDNs.First,a useful lemma with respect to the relationship between the discrete time observations term and a continuous term is developed.Second,by utilizing an inequality technique and auxiliary functions,the rigorous global exponential synchronization analysis is given and synchronization criterions are achieved in terms of linear matrix inequalities(LMIs).Finally,two examples are provided to illustrate the correctness of the obtained results.

药物肝毒性评价体外细胞模型的相关研究进展

药物的生物安全性是决定新药研发成败的第一要素,肝脏是药物毒性的主要靶点,开发高效、可靠、便捷、安全的药物肝毒性预测模型是制药领域重点关注的难点和热点。良好的体外毒性预测模型需要选择适宜的细胞种类及完善的培养体系,以维持细胞的肝脏特异性功能。随着技术的革新,各种药物肝毒性评价模型应运而生,然而,受限于离体与在体环境的固有差异,任何模型都有其优势和局限性,只能通过不断优化模型体系,或针对性的选择特定的模型,才能获得更为准确的评价结果。本文综述了体外药物肝毒性预测模型的研究现状,涉及主流的体外模型的构建方法、特点属性、改良方案及应用前景,希望能为肝毒性研究提供一些新的思路。

The stationary solution of a random dynamical model

This paper studies the stationary probability density function（PDF） solution of a nonlinear business cycle model subjected to random shocks of Gaussian white-noise type. The PDF solution is controlled by a Fokker–Planck– Kolmogorov（FPK） equation, and we use exponential polynomial closure（EPC） method to derive an approximate solution for the FPK equation. Numerical results obtained from EPC method, better than those from Gaussian closure method, show good agreement with the probability distribution obtained with Monte Carlo simulation including the tail regions.

Microstructure and mechanical properties of Mg-14Li-1Al-0.3La alloys produced by two-pass extrusion

The microstructure of as-cast and extruded Mg-14 Li-1 Al-（0, 0.3） La alloys was examined with XRD,OM, SEM, and EDS. The mechanical properties of the extruded specimens with and without La were compared. The results show that La addition has an obvious effect on the microstructure of the as-cast LA141 alloy by reducing the average grain size from 600 to 220 μm. β-Li and LiMgAl2 phases are observed in both alloys, and long-rod-shaped Al2 La phase is also observed in the La containing alloy. After extrusion, Al2 La phases are short-rod-shaped and distribute evenly in the alloy. LAl41-0.3 La alloy has higher elongation（34%）, which is attributed to refined microstructure and weak texture due to shortrod-like Al2 La phase.

Seasonal variation characteristics of hydroxyl radical pollution and its potential formation mechanism during the daytime in Lanzhou

Hydroxyl free radicals(OH radicals) play the main role in atmospheric chemistry and their involving reactions are the dominant rate determining step in the formation of secondary fine particulate matter and in the removal of air pollutants from the atmosphere.In this paper,we studied the seasonal variation characteristics of OH radicals during the daytime in Lanzhou and explored the potential formation mechanism of high concentration OH radicals.We found that the OH radicals in four seasons was 2.7×106,2.6×106,3.1×106, and2.2×106 cm-3,respectively.Since the rainfall was concentrated in summer,the wet deposition had a significant effect on removing OH radicals.Among the four pollutants(including ozone(O3),volatile organic compounds(VOCs),nitrogen dioxide(NO2) and fine particulate matter(PM2.5)),the variation of OH radicals were closely related to ozone concentration especially in spring and summer.In autumn,the correlation between PM2.5 and OH radicals were the closest among the observing pollutants and its formation mechanism was different conventional regeneration pathway.In Event 1,high concentration of ozone was the main source of OH radicals;under the high humidity condition,except for ozone,the multiple factors including VOCs,NO2 and PM2.5 interplayed and leaded to the Event 2.