A strong inorganic acid‐initiated methacrylate polymerization strategy for room temperature preparation of monolithic columns for capillary electrochromatography

A facile strong inorganic acid‐initiated methacrylate polymerization strategy was developed for fabricating monolithic columns at room temperature. The prepared monoliths were characterized by FTIR spectrometry, mercury intrusion porosimeter and SEM, while their performance was evaluated by CEC for the separation of various types of compounds including alkyl benzenes, polycyclic aromatic hydrocarbons, nonsteroidal anti‐inflammatory drugs, anilines, and nitrophenol isomers. The column‐to‐column and batch‐to‐batch reproducibility for the prepared monoliths in terms of the RSD of EOF flow velocity, retention factor, and the minimum plate height of naphthalene ranged from 3.4 to 12.4%. The fabricated monoliths gave excellent performance for the separation of the test neutral compounds with the theoretical plates of 170 000–232 000 plates per meter for thiourea, and 77 400–112 300 plates per meter for naphthalene. The proposed strong inorganic acid‐initiated methacrylate polymerization strategy is a promising alternative for fabricating organic polymer‐based monoliths.     

An iterative approximation method for solving a general system of variational inequality problems and mixed equilibrium problems

In this paper, we introduce an iterative algorithm for finding a common element of the set of solutions of a mixed equilibrium problem, the set of fixed points of an infinite family of nonexpansive mappings and the set of solutions of a general system of variational inequalities for a cocoercive mapping in a real Hilbert space. Furthermore, we prove that the proposed iterative algorithm converges strongly to a common element of the above three sets. Our results extend and improve the corresponding results of Ceng, Wang, and Yao [L.C. Ceng, C.Y. Wang, J.C. Yao, Strong convergence theorems by a relaxed extragradient method for a general system of variational inequalities, Math. Methods Oper. Res. 67 (2008) 375–390], Ceng and Yao [L.C. Ceng, J.C. Yao, A hybrid iterative scheme for mixed equilibrium problems and fixed point problems, J. Comput. Appl. Math. doi:10.1016/j.cam.2007.02.022], Takahashi and Takahashi [S. Takahashi, W. Takahashi, Viscosity approximation methods for equilibrium problems and fixed point problems in Hilbert spaces, J. Math. Anal. Appl. 331 (2007) 506–515] and many others.     

Asplund Spaces, Stegall Variational Principle and the RNP

Given a pair of Banach spaces X and Y such that one is the dual of the other, we study the relationships between generic Fréchet differentiability of convex continuous functions on Y (Asplund property), generic existence of linear perturbations for lower semicontinuous functions on X to have a strong minimum (Stegall variational principle), and dentability of bounded subsets of X (Radon-Nikodym Property).      

强定向图的k-强距离

对强连通有向图D的一个非空顶点子集S,D中包含S的具有最少弧数的强连通有向子图称为S的Steiner子图,S的强Steiner距离d(S)等于S的Steiner子图的弧数. 如果|S|=k, 那么d(S)称为S的k-强距离. 对整数k≥2和强有向图D的顶点v,v的k-强离心率sek(v)为D中所有包含v的k个顶点的子集的k-强距离的最大值. D中顶点的最小k-强离心率称为D的k-强半径,记为sradk(D),最大k-强离心率称为D的k-强直径,记为sdiamk(D). 本文证明了,对于满足k+1≤r,d≤n的任意整数r,d,存在顶点数为n的强竞赛图T′和T″,使得sradk(T′)=r和sdiamk(T″)=d;进而给出了强定向图的k-强直径的一个上界.     

Reprint of : Kondo effect in a carbon nanotube with spin–orbit interaction and valley mixing: A DM-NRG study

We investigate the effects of spin–orbit interaction (SOI) and valley mixing on the transport and dynamical properties of a carbon nanotube (CNT) quantum dot in the Kondo regime. As these perturbations break the pseudo-spin symmetry in the CNT spectrum but preserve time-reversal symmetry, they induce a finite splitting $\Delta$ between formerly degenerate Kramers pairs. Correspondingly, a crossover from the SU(4) to the SU(2)-Kondo effect occurs as the strength of these symmetry breaking parameters is varied. Clear signatures of the crossover are discussed both at the level of the spectral function as well as of the conductance. In particular, we demonstrate numerically and support with scaling arguments that the Kondo temperature scales inversely with the splitting $\Delta$ in the crossover regime. In presence of a finite magnetic field, time reversal symmetry is also broken. We investigate the effects of both parallel and perpendicular fields (with respect to the tube's axis) and discuss the conditions under which Kondo revivals may be achieved.     

Controlling the strong field fragmentation of ClCHO+ using two laser pulses –an ab initio molecular dynamics simulation

For a single, intense 7 μm linearly polarized laser pulse, we found that the branching ratio for the fragmentation of ClCHO⁺ → Cl + HCO⁺, H + ClCO⁺, HCl⁺+CO depended strongly on the orientation of the molecule (J. Phys. Chem. Lett. 2012 , 3 2541). The present study explores the possibility of controlling the branching ratio for fragmentation by using two independent pulses with different frequencies, alignment and delay. Born-Oppenheimer molecular dynamics simulations in the laser field were carried out with the B3LYP/6-311G(d,p) level of theory using combinations of 3.5, 7 and 10.5 μm sine squared pulses with field strengths of 0.03 au (peak intensity of 3.15×10¹³ W/cm²) and lengths of 560 fs. A 3.5 μm pulse aligned with the C-H bond and a 10.5 μm pulse perpendicular to the C-H bond produced a larger branching ratio for HCl⁺+CO than a comparable single 7 μm pulse. When the 10.5 μm pulse was delayed by one quarter of the pulse envelope, the branching ratio for the high energy product, (HCl⁺+CO 73%) was a factor of three larger than the low energy product (Cl + HCO⁺, 25%). By contrast, when the 3.5 μm pulse was delayed by one quarter of the pulse envelope, the branching ratio was reversed (HCl⁺+CO 38%; Cl + HCO⁺, 60%). Continuous wavelet analysis was used to follow the interaction of the laser with the various vibrational modes as a function of time. © 2018 Wiley Periodicals, Inc.     

强磁场下NH4Cl水溶液结构的拉曼光谱研究

迄今为止,国内外存在很多关于强磁场处理对水溶液结构影响的争议,并且关于强磁场对无机盐水溶液结构的研究也相对较少。运用拉曼光谱法,测定了在外加强磁场1.8 T强度下,高纯水与质量分数分别为1%,5%,10%,20%和28%的NH₄Cl水溶液在不同磁化时间下的拉曼散射数据,为拉曼光谱法探究强磁场对水溶液结构的影响提供了一个新的可行方式,丰富了拉曼光谱的研究领域。由实验结果可知,随着磁化时间的增加,水分子中氢键的伸缩振动峰值逐渐升高,经过一定的磁化时间后可以达到饱和。高纯水与不同质量分数的NH₄Cl水溶液的饱和效应时间均不同。高纯水与质量分数为1%,5%,10%,20%和28%的NH₄Cl水溶液峰值饱和时间分别为150,120,120,100,80和80 min。随着NH₄Cl水溶液质量分数的增加,达到磁效应饱和的时间呈现减少的趋势。磁场移除后,测定高纯水与不同质量分数NH₄Cl水溶液的去磁记忆时间。高纯水与质量分数为1%,5%,10%,20%和28%的NH₄Cl水溶液的去磁记忆时间分别为30,40,50,60,80和80 min。随着NH₄Cl水溶液质量分数的增加,去磁记忆时间呈现增加的趋势。利用去卷积拟合的方法对磁化2 h后不同质量分数的NH₄Cl水溶液进行处理。由去卷积拟合结果可知,质量分数为20%的NH₄Cl水溶液比质量分数为10%的NH₄Cl水溶液增加了一个N-H峰,该信号峰随着NH₄Cl水溶液质量分数的增大逐渐增强。DDAA型氢键结构整体上随磁化时间增加而减少,磁化时间的增加对四面体水结构具有破坏作用。当达到饱和磁化时间后,DDAA型氢键不再发生变化。实验结果表明,通过拉曼光谱法可以得到1.8 T强磁场对NH₄Cl水溶液结构的影响规律,为外加强磁场条件下其他无机盐水溶液的研究提供了一定的理论基础。     

有限族严格伪压缩映象具误差的隐迭代序列的强收敛性

在适当的条件下,证明了有限族严格伪压缩映象具误差的隐迭代序列强收敛于其公共不动点. 所得结果改进了Osilike 与 Xu, Ori 的相应结果.     

有序介孔三氧化二锰负载PdPt合金:一种高效的甲烷催化燃烧催化剂

甲烷作为一种清洁廉价的碳氢能源,广泛应用于运输业和其它工业领域.但是其本身是一种比二氧化碳导致全球变暖效应更强的温室气体,而且甲烷直接燃烧会产生其它污染物,比如一氧化碳、氮氧化物、未充分燃烧的碳氢化合物等.因此有必要开展有关甲烷催化燃烧的研究工作,以大幅度降低起燃温度,提高燃烧效率,有效地减少污染副产物的产生.由于具有较好的低温催化活性,Pd基催化剂常用于甲烷的催化燃烧.但是Pd基催化剂也存在一些亟需解决的问题,比如在催化燃烧过程中活性相结构不稳定.PdO通常被认为是碳氢化合物催化氧化中的活性相,但是在高温下PdO分解为Pd,导致催化活性下降.PdO遇到含水或硫的化合物时会生成惰性的Pd(OH)2或稳定的硫化物,造成活性物种的流失,从而降低催化剂的性能.如果在材料中添加另一种贵金属Pt,使之与Pd一起形成贵金属合金,则可提高其低温催化燃烧的活性,增加Pd基催化剂的热稳定性以及抗水和抗硫能力.另一方面,过渡金属氧化物价格便宜,热稳定性以及抗硫性较好,也常作为甲烷燃烧的催化剂.其中三氧化二锰由于具有可变的氧化态以及较好的储氧能力受到了广泛关注.本课题组采用KIT-6作为硬模板,先合成具有有序介孔结构的Mn2O3(meso-Mn2O3)纳米催化剂,然后通过聚乙烯醇(PVA)保护的液相共还原法分别制备meso-Mn2O3担载Pd,Pt及PdPt合金的纳米催化剂(x(PdyPt)/meso-Mn2O3;x=(0.10-1.50)wt%;Pd/Pt摩尔比(y)=4.9-5.1).XRD结果表明,合成的meso-Mn2O3具有立方相晶体结构.其BET比表面积为106 m2/g.由TEM照片可观察到粒径范围为2.1?2.8 nm的贵金属纳米颗粒均匀分散在meso-Mn2O3表面.通过XPS分析可知,结合能在529.6和531.2 eV的峰可分别归属于晶格氧(Olat)和表面吸附氧(Oads).Pd0和Pd2+以及Pt0和Pt2+也均可通过曲线拟合后进行分峰确定.XPS定量分析结果表明,样品的Oads/Olat摩尔比有如下顺序:1.41(Pd5.1Pt)/meso-Mn2O3(0.77)>1.40Pd/meso-Mn2O3(0.69)>0.72(Pd5.1Pt)/meso-Mn2O3(0.65)>1.42Pt/meso-Mn2O3(0.63)>0.07(Pd4.9Pt)/meso-Mn2O3(0.53)>0.07(Pd4.9Pt)/bulk-Mn2O3(0.52)>meso-Mn2O3(0.45),这与其催化活性的顺序一相致.该结果表明,高的吸附氧物种浓度有利于甲烷催化燃烧.负载Pd,Pt或PdPt以后的样品的表面吸附氧物种浓度显著提高,催化活性最好的1.41(Pd5.1Pt)/meso-Mn2O3样品具有最高的吸附氧物种浓度.负载PdPt合金可有效提高催化剂对甲烷燃烧的催化活性.1.41(Pd5.1Pt)/meso-Mn2O3催化剂的活性最好:在空速为20000 mL/(g.h)的条件下,甲烷燃烧的T10%,T50%和T90%分别为265,345和425oC.此外,还考察了引入一定量的SO2,CO2,H2O和NO对甲烷在1.41(Pd5.1Pt)/meso-Mn2O3催化剂上氧化反应的影响,发现引入少量的Pt可提高催化剂抗SO2,CO2和H2O的能力,但是NO对甲烷燃烧的还原效应也不可忽视.基于催化剂物化性质的表征结果和活性数据,我们认为1.41(Pd5.1Pt)/meso-Mn2O3优异的催化性能与其拥有高质量的三维有序多孔结构、高的吸附氧物种浓度、优良的低温还原性以及Pd-Pt合金与meso-Mn2O3载体之间的强相互作用有关.     

Convergence of Numerical Approximation for Jump Models Involving Delay and Mean-Reverting Square Root Process

The mean-reverting square root process with jump has been widely used as a model on the financial market. Since the diffusion coefficient in the model does not satisfy the linear growth condition and local Lipschitz condition, we can not examine its properties by traditional techniques. To overcome the difficulties, we develop several new techniques to examine the numerical method of jump models involving delay and mean-reverting square root. We show that the numerical approximate solutions converge to the true solutions. Finally, we apply the convergence to examine a path-dependent option price and a bond in the financial pricing.