Computational, 1H NMR,and X‐ray structural studies on 1‐arylurazole tetrazane dimers

Nitrogen‐centered urazole radicals exist in equilibrium with tetrazane dimers in solution. The equilibrium established typically favors the free‐radical form. However, 1‐arylurazole radicals bearing substituents at the ortho position favor the dimeric form. We were able to determine the structure of one of the dimers (substituted at both ortho positions with methyl groups), namely 1,2‐(2,4‐dimethylphenyl)‐2‐[2‐(2,4‐dimethylphenyl)‐4‐methyl‐3,5‐dioxo‐1,2,4‐triazolidin‐1‐yl]‐4‐methyl‐1,2,4‐triazolidine‐3,5‐dione, C₂₄H₂₈N₆O₄, via X‐ray crystallography. The experimentally determined structure agreed well with the computationally obtained geometry at the B3LYP/6‐311G(d,p) level of theory. The preferred syn conformation of these 1‐arylurazole dimers results in the two aromatic rings being proximate and nearly parallel, which leads to some interesting shielding effects of certain signals in the ¹H NMR spectrum. Armed with this information, we were able to decipher the more complicated ¹H NMR spectrum obtained from a dimer that was monosubstituted at the ortho position with a methyl group.     

Y修饰CuO/ZrO_2催化剂高效催化水煤气变换反应制氢

采用水热法制备了具有不同Y掺杂量的单分散ZrO_2纳米粒子(n(Y)/n(Y+Zr)=0-5%),并以其为载体采用沉积-沉淀法制得CuO/ZrO_2催化剂;考察了富氢气氛下上述催化剂的水煤气变换反应(WGS)催化性能。结果表明,掺杂Y后催化剂的活性明显提高,其中,载体掺杂2%Y的催化剂具有最佳的催化活性,在270℃时的CO转化率高达91.4%,明显高于研究较多的CuO/ZnO和CuO/CeO_2催化剂。X射线粉末衍射、N_2物理吸附-脱附、N_2O滴定、扫描电镜和CO程序升温还原等表征结果表明,Y~(3+)掺入了ZrO_2的晶格并对催化剂的结构和还原性能产生直接影响。Y助剂的引入一方面促进了CuO在ZrO_2表面的分散,提高了催化剂表面活性Cu-[O]-Zr物种的含量;另一方面,改善了催化剂的颗粒单分散性和织构性能。载体掺杂2%Y助剂的样品具有较高的Cu-[O]-Zr物种含量、较佳的颗粒单分散性和织构性能,且其表面的Cu-[O]-Zr物种和活性羟基具有较佳的还原性能,因而表现出较高的催化活性     

Banach空间中一类二阶具阻尼项的积分-微分包含的可控性

本文讨论了一类二阶具阻尼项的积分-微分包含问题.利用集值不动点定理将问题转化为求不动点问题,进而得到系统可控性的充分条件.     

具有势函数的弱f-稳态映射的若干结果

本文研究了与拉回度量有关广义泛函Φ_f,H.利用应力能量张量的方法,得到具有势函数的弱f-稳态映射的一些刘维尔型定理.     

Calderón problem for connections

In this paper, we consider the problem of identifying a connection ? on a vector bundle up to gauge equivalence from the Dirichlet-to-Neumann map of the connection Laplacian ?*? over conformally transversally anisotropic (CTA) manifolds. This was proved in [9 Dos Santos Ferreira, D., Kenig, C., Salo, M., Uhlmann, G. (2009). Limiting Carleman weights and anisotropic inverse problems. Invent. Math. 178:119–171.[Crossref], [Web of Science ®] , [Google Scholar]] for line bundles in the case of the transversal manifold being simple—we generalize this result to the case where the transversal manifold only has an injective ray transform. Moreover, the construction of suitable Gaussian beam solutions on vector bundles is given for the case of the connection Laplacian and a potential, following the works of [11 Dos Santos Ferreira, D., Kurylev, Y., Lassas, M., Salo, M. (2016). The Calderón problem in transversally anisotropic geometries. J. Eur. Math. Soc., 18:2579–2626.[Crossref], [Web of Science ®] , [Google Scholar]]. This in turn enables us to construct the Complex Geometrical Optics (CGO) solutions and prove our main uniqueness result. We also reduce the problem to a new non-abelian X-ray transform for the case of simple transversal manifolds and higher rank vector bundles. Finally, we prove the recovery of a flat connection in general from the DN map, up to gauge equivalence, using an argument relating the Cauchy data of the connection Laplacian and the holonomy.     

Stability,periodicity, and symmetries of certain second‐order fractional difference equation with quadratic terms via KAM theory

By using the Kolmogorov–Arnold–Moser theory, we investigate the stability of the equilibrium solution of the difference equation where A ,B ,D > 0,u _?1,u ₀>0. We also use the symmetries to find effectively the periodic solutions with feasible periods. Copyright © 2016 John Wiley & Sons, Ltd.