Aerobic Asymmetric Dehydrogenative Cross‐Coupling between Two C?H Groups Catalyzed by a Chiral‐at‐Metal Rhodium Complex

A sustainable C C bond formation is merged with the catalytic asymmetric generation of one or two stereocenters. The introduced catalytic asymmetric cross‐coupling of two C H groups with molecular oxygen as the oxidant profits from the oxidative robustness of a chiral‐at‐metal rhodium(III) catalyst and exploits an autoxidation mechanism or visible‐light photosensitized oxidation. In the latter case, the catalyst serves a dual function, namely as a chiral Lewis acid for catalyzing enantioselective enolate chemistry and at the same time as a visible‐light‐driven photoredox catalyst.     

Cysteine‐Mediated Intracellular Building of Luciferin to Enhance Probe Retention and Fluorescence Turn‐On

The development of sensitive and selective small molecular probes that enable real‐time detection of endogenous cysteine (Cys) has become an attractive topic because of the essential roles played by Cys in controlling the cellular nitrogen balance and in maintaining biological redox homeostasis. Herein, we report a Cys‐specific probe, 2‐cyanobenzothiazol‐6‐yl acrylate (CBTOA), that shows not only fluorescence turn‐on for sensitive detection of endogenous Cys but also enhanced probe retention inside cells for real‐time monitoring of Cys levels upon external stimulation. Cys‐mediated intracellular formation of luciferin from CBTOA was the key strategy leading to this new type of fluorogenic probe. CBTOA showed fast response to Cys in living cells and liver tissue slices with high sensitivity and selectivity. By using CBTOA as a real‐time probe, we were able to monitor the change in Cys levels in living HeLa cells under ROS‐induced oxidative stress as well as in human mesenchymal stem cells during adipogenic differentiation.     

板材冲压成形有限元数值模拟界面摩擦约束处理方法

基于弹塑性大变形板材冲压成形增量有限元法,采用线性弹簧单元提出一种空间三维板材冲压成形等效界面摩擦力的处理方法.这种方法的优点是可以反映界面摩擦力的同步、被动产生效果,同时它还可以保证约束后刚度矩阵的对称性.将提出的摩擦约束处理算法引入自主开发的板材成形模拟软件FASTAMP,计算了汽车油底壳的成形过程,计算结果的厚度分布与实际冲压件吻合比较好,验证了等效界面摩擦力约束处理方法的有效性.     

A finite element analysis of the flange earrings of strong anisotropic sheet metals in deep-drawing processes

Flange earrings of strong anisotropic sheet metals in deep-drawing process are numerically analyzed by the elastic-plastic large deformation finite element formulation based on a discrete Kirchhoff triangle plate shell element model. A Barlat-Lian anisotropic yield function and a quasi-flow corner theory are used in the present formulation. The numerical results are compared with the experimental ones of cylindrical cup drawing process. The focus of the present researches is on the numerical analysis and the constraining scheme of the flange earring of circular sheets with strong anisotropy in square cup drawing process. The project supported by the National Natural Science Foundation of China (19832020) and Provincial Natural Science Foundation of Jilin, China (200000519)     

基于石墨烯的样品制备技术研究亮点

自2004年被首次制备出来,石墨烯就受到了全世界科学家的普遍关注。石墨烯是由单层碳原子组成的六方蜂巢状结构的二维物质,如果以每平方纳米石墨烯片层结构上容纳的碳原子个数为38来计算,石墨烯具有很大的比表面积（2630 m2/g）,再加上其生产成本低,使其成为样品预处理中理想的富集材料之一。     

Electronic structure of a low-spin heme/Cu peroxide complex: spin-state and spin-topology contributions to reactivity

This study details the electronic structure of the heme–peroxo–copper adduct {[(F8)Fe(DCHIm)]-O2-[Cu(AN)]}+ (LS(AN)) in which O2(2–) bridges the metals in a μ-1,2 or “end-on” configuration. LS(AN) is generated by addition of coordinating base to the parent complex {[(F8)Fe]-O2-[Cu(AN)]}+ (HS(AN)) in which the O2(2–) bridges the metals in an μ-η2:η2 or “side-on” mode. In addition to the structural change of the O2(2–) bridging geometry, coordination of the base changes the spin state of the heme fragment (from S = 5/2 in HS(AN) to S = 1/2 in LS(AN)) that results in an antiferromagnetically coupled diamagnetic ground state in LS(AN). The strong ligand field of the porphyrin modulates the high-spin to low-spin effect on Fe–peroxo bonding relative to nonheme complexes, which is important in the O–O bond cleavage process. On the basis of DFT calculations, the ground state of LS(AN) is dependent on the Fe–O–O–Cu dihedral angle, wherein acute angles (<~150°) yield an antiferromagnetically coupled electronic structure while more obtuse angles yield a ferromagnetic ground state. LS(AN) is diamagnetic and thus has an antiferromagnetically coupled ground state with a calculated Fe–O–O–Cu dihedral angle of 137°. The nature of the bonding in LS(AN) and the frontier molecular orbitals which lead to this magneto-structural correlation provide insight into possible spin topology contributions to O–O bond cleavage by cytochrome c oxidase.     

The structure of left C-rpp semigroups

This paper studies the class of left Clifford-rpp semigroups and investigates the structure of their semi-spined products and semilattice decompositions. These semigroups are generalizations of left Clifford semigroups and Clifford-rpp semigroups. We also discuss some special cases such as when a semilattice decomposition becomes a strong semilattice decomposition and a semi-spined product becomes a spined product. Communicated by Boris Schein This research is jointly supported by a grant of National Natural Science Foundation of China and a small project grant #200.600.380 of CUHK.     

左C─半群的又一结构

作为Ｃｌｉｆｆｏｒｄ半群的推广的左Ｃｌｉｆｆｏｒｄ半群（左Ｃ─半群）已有一ξ─积结构。本文给出了左Ｃ─半群的另一结构，所谓△─积结构，它的一个特殊情形恰好为左群的强半格。这一新结构为半群的Ｃｌｉｆｆｏｒｄ层次的研究伸展到拟正则半群领域奠定了基础。     

镀膜玻璃的色差分析与测定方法探讨

影响镀膜玻璃外观的关键质量指标是其颜色的均匀性，本文结合实际情况，详细论述和探讨镀膜玻璃的色差分析和测定，提出了一种镀膜玻璃色差指标的表征方法。