Three‐photon absorption properties of a novel symmetrical Carbazole derivative having terminal 1,10‐phenanthroline rings via carbon–nitrogen (C = N) double bond

Three‐photon absorption (3PA) properties of symmetric‐type carbazole derivatives show great potential for application in light‐activated therapy and optical limiting. A novel symmetrical carbazole derivative (abbreviated as POCP) with end‐groups of 1,10‐phenanthroline rings as the donor moieties, chained via carbon–nitrogen (C = N) double bond, has been synthetized and its three photon absorption properties has been also determined by using a Q‐switched Nd: YAG laser pumped with 30 ps pulses at 1064 nm in dimethylformamide. The measurement of 3PA cross‐section of this compound is performed by open aperture Z‐scan and σ_3PA is 481 × 10^–78 cm⁶ ? s²/photon² for the transition S₀ → S₁. The influence of the molecular structure of this compound on three‐photon absorption cross‐sections is discussed micromechanically by Austin model 1 and Zerner's Intermediate Neglect of Differential Overlap/S method. Copyright © 2012 John Wiley & Sons, Ltd.     

Characterization of large‐sized Nd:YAG single crystals grown by horizontal directional solidification

Nd³⁺‐doped Y₃Al₅O₁₂ single crystals have been grown by the horizontal directional solidification (HDS) method in different thermal zone. The Grashof (G_r), Prandtl (P_r), Marangoni (M_a) and Rayleigh (R_a) numbers of melt in HDS system have been discussed for our experimental system to understand the mechanism of melt flow patterns and concentration gradient of dopant. The concentration gradient of Nd³⁺ ions was explained with melt flow processes during crystal growth in different thermal zone, and results indicated that high growth temperature will be helpful for uniformity of dopant in HDS‐grown single crystal. The main microscopic growth defects such as bubbles and irregular inclusions in HDS‐grown Nd:YAG crystals were observed, and the causes were discussed as well. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

双功能WC/HZSM-5催化剂上正己烷芳构化反应性能

以HZSM-5(SiO2/Al2O3=38)为载体,偏钨酸铵为钨源制备了双功能催化剂WC/HZSM-5,考察了其催化正己烷芳构化反应性能,并采用X射线衍射、扫描电子显微镜、X射线能量散射谱和程序升温氨脱附等手段对催化剂进行了表征,探讨了制备方法和WC含量对WC/HZSM-5催化剂性能的影响.结果表明,采用原位还原碳化法制备的WC/HZSM-5(RC)催化剂上正己烷芳构化反应性能优于浸渍法制备的WC/HZSM-5(IP).5%WC/HZSM-5(RC)样品在反应初始阶段芳烃选择性为10.28%,而HZSM-5上的仅为2.56%.WC/HZSM-5(RC)催化剂上反应产物中轻质芳烃(苯、甲苯和二甲苯)含量增加,重质芳烃C9+含量降低,其催化性能优于Pt/HZSM-5催化剂.产物分布的变化可能是由于WC与分子筛间的协同作用所致.     

A Posteriori Error Estimators of Gradient Recovery Type for Elliptic Obstacle Problems

In this paper, we present a posteriori error estimates of gradient recovery type for elliptic obstacle problems. The a posteriori error estimates provide both lower and upper error bounds. It is shown to be equivalent to the discretization error in an energy type norm for general meshes. Furthermore, when the solution is smooth and the mesh is uniform, it is shown to be asymptotically exact. Some numerical results which demonstrate the theoretical results are also reported in this paper.     

Gradient recovery type a posteriori error estimate for finite element approximation on non-uniform meshes

In this paper, we derive gradient recovery type a posteriori error estimate for the finite element approximation of elliptic equations. We show that a posteriori error estimate provide both upper and lower bounds for the discretization error on the non-uniform meshes. Moreover, it is proved that a posteriori error estimate is also asymptotically exact on the uniform meshes if the solution is smooth enough. The numerical results demonstrating the theoretical results are also presented in this paper.     

土壤和沉积物石油污染现状

针对全球石油污染的现状从原油的组成、分类与对环境的潜在影响、原油中有毒有害物质的成分、石油的工业工艺流程等方面进行了论述,并着重分析了中国土壤和沉积物原油污染,对松辽盆地、济阳坳陷、塔里木盆地、渤海油区等区域污染现状作了详细介绍,对石油勘探开发中重要污染源之一——化学助剂造成的污染也作了总括.     

Anisotropic Superconducting Properties of Kagome Metal CsV_3Sb_5

We systematically measure the superconducting(SC) and mixed state properties of high-quality CsV_3 Sb_5 single crystals with T_c～3.5 K.We find that the upper critical field H_(c2)(T) exhibits a large anisotropic ratio of H_(c2)~(ab)/H_(c2)~c～9 at zero temperature and fitting its temperature dependence requires a minimum two-band effective model.Moreover,the ratio of the lower critical field,H_(c1)~(ab)/H_(c1)~c,is also found to be larger than 1,which indicates that the in-plane energy dispersion is strongly renormalized near Fermi energy.Both H_(c1)(T) and SC diamagnetic signal are found to change little initially below T_c～3.5 K and then to increase abruptly upon cooling to a characteristic temperature of ～2.8 K.Furthermore,we identify a two-fold anisotropy of in-plane angular-dependent magnetoresistance in the mixed state.Interestingly,we find that,below the same characteristic T～2.8 K,the orientation of this two-fold anisotropy displays a peculiar twist by an angle of 60° characteristic of the Kagome geometry.Our results suggest an intriguing superconducting state emerging in the complex environment of Kagome lattice,which,at least,is partially driven by electron-electron correlation.     

Heterogeneous Metal–Organic-Framework-Based Biohybrid Catalysts for Cascade Reactions in Organic Solvent

In cooperative catalysis, the combination of chemo- and biocatalysts to perform one-pot reactions is a powerful tool for the improvement of chemical synthesis. Herein, UiO-66-NH₂ was employed to stepwise immobilize Pd nanoparticles (NPs) and Candida antarctica lipase B (CalB) for the fabrication of biohybrid catalysts for cascade reactions. Distinct from traditional materials, UiO-66-NH₂ has a robust but tunable structure that can be utilized with a ligand exchange approach to adjust its hydrophobicity, resulting in excellent catalyst dispersity in diverse reaction media. These attractive properties contribute to the formation of MOF-based biohybrid catalysts with high activity and selectivity in the synthesis of benzyl hexanoate from benzaldehyde and ethyl hexanoate. With this proof-of-concept, we reasonably expect that future tailor-made MOFs can combine other catalysts, ranging from chemical to biological catalysts for applications in industry.     

Nonexistence of coexisting steady‐state solutions of Dirichlet problem for a cross‐diffusion model

We study a special case of Shigesada–Kawasaki–Teramoto (SKT) model for two competing species with the Dirichlet boundary conditions. In our case, one of the species is not influenced by self‐diffusion or cross‐diffusion. We specify the explicit range of parameters by contradiction such that there are no coexisting steady‐state solutions to the model.