E-inversive semigroups with a completely simple kernel

We show that an E-inversive semigroup S has a completely simple kernel K_S if and only if it contains a primitive idempotent (in that case, K_S is the set-theoretic union of the groups eSe, where e is a primitive idempotent of S). Along the way, some equivalent conditions for a semigroup to be E-inversive are given. Moreover, some applications of the above theorem will be pointed out.     

Rational Design of Single Molybdenum Atoms Anchored on N‐Doped Carbon for Effective Hydrogen Evolution Reaction

The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo‐SAs) supported on N‐doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration‐corrected scanning transmission electron microscopy (AC‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo‐SAs anchored with one nitrogen atom and two carbon atoms (Mo₁N₁C₂). Importantly, the Mo₁N₁C₂ catalyst displayed much more excellent activity compared with Mo₂C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo₁N₁C₂ moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo‐based HER catalysts.     

Acid‐Labile Acyclic Cucurbit[n]uril Molecular Containers for Controlled Release

Stimuli‐responsive molecular containers are of great importance for controlled drug delivery and other biomedical applications. A new type of acid labile acyclic cucurbit[n ]uril (CB[n ]) molecular containers is presented that can degrade and release the encapsulated cargo at accelerated rates under mildly acidic conditions (pH 5.5–6.5). These containers retain the excellent recognition properties of CB[n ]‐type hosts. A cell culture study demonstrated that the cellular uptake of cargos could be fine‐tuned by complexation with different containers. The release and cell uptake of cargo dye was promoted by acidic pH.     

Comprehensive study of the correlations that exist among the members of the [n]cyclacene series and the Möbius[n]cyclacene series

Cyclacenes are the smallest substructures of carbon nanotubes used in modelling studies. The systematics that exists between Hückel molecular orbital eigenvalues and eigenvectors of cyclacenes are delineated. This study of cyclacenes combines the interconnection of concepts of complementarity theorem, characteristic and matching polynomial recursion equations, embedding, greater than twofold symmetry and doubly degenerate eigenvalues, open-shell singlet character, and pairing theorem. Proof that cyclacenes have more open-shell (diradical) character than do polyacenes is also provided by the sum total of this work. Mirror-plane scission of even-ring cyclacenes gives linear polyacene fragments. This shows that the properties of the successor linear polyacene must be contained in the precursor cyclacene. Corresponding Möbius[n]cyclacene isomers display contrasting and unusual comparative properties. A partial list of contrasting properties include alternant (cyclacenes) versus nonalternant (Möbius[n]cyclacene) polyenes, presence of Hamiltonian circuits in Möbius[n]cyclacene and presence of oscillatory electronic properties in cyclacenes.     

THE ESTABLISHMENT PROCESS OF INTERNATIONAL UNION OF THEORETICAL AND APPLIED MECHANICS

本文依据历史资料,简述了国际理论与应用力学联合会(International Union of Theoretical and Applied Mechanics,IUTAM)的建立过程,以及中国力学学会 (Chinese Society of Theoretical and Applied Mechanics,CSTAM) 1980年加入国际理论与应用力学联合会的一些情况,供大家研究力学史时参考。     

Inertia Effects in High-Rate Flow Through Heterogeneous Porous Media

The paper deals with the effects of large scale permeability–heterogeneity on flows at high velocities through porous media. The media is made of a large number of homogeneous blocks where the flow is assumed to be governed by the Forchheimer equation with a constant inertial coefficient. By assuming the validity of the Forchheimer equation at the large scale, an effective inertial coefficient is deduced from numerical simulations. Different media are investigated: serial-layers, parallel-layers and correlated media. The numerical results show that: (i) for the serial-layers, the effective inertial coefficient is independent of the Reynolds number and decreases when the variance and the mean permeability ratio increases; (ii) for the parallel-layers and the correlated media, the effective inertial coefficient is function of the Reynolds number and increases when the variance and the mean permeability ratio increases. Theoretical relationships are proposed for the inertial coefficient as function of the Reynolds number and the characteristics of the media.     

Transient thermal gratings at surfaces for thermal characterization of bulk materials and thin films

Transient Thermal Gratings (TTGs) at surfaces of absorbing materials have been utilized for investigating heat diffusion in bulk materials and thin films. In this report, we describe the theoretical background of the technique and present experimental data. TTGs were excited in the surface plane by interference of two pulsed laser beams and monitored by a cw probe beam, either via temperature dependence of the reflectivity or by deflection from the displacement pattern. A theoretical model describing the thermal and thermoelastic surface response was developed, both for a homogeneous material and a multilayer structure. The potential of the technique will be demonstrated by experimental results on (i) thermal diffusivities of bulk materials, (ii) anisotropic lateral heat transport, and (iii) thermal diffusivities of metal and diamond films. Furthermore, we will show that TTGs allow thermal depth profiling of inhomogeneous materials whenever there is a vertical gradient in thermal conductivity.     

Influence of the isomeric structures of butyl acrylate on its single‐electron transfer‐degenerative chain transfer living radical polymerization in water Catalyzed by Na2S2O4

The aim of this work is to the study the influence of the isomer structures of butyl acrylate monomer on the single‐electron transfer/degenerative chain transfer mediated living radical polymerization (SET‐DTLRP). The kinetic of isobutyl acrylate is determined for the first time by SET‐DTLRP in water catalyzed by sodium dithionite. The plots of number‐average molecular weight versus conversion and ln([M]₀/[M]) versus time are linear, demonstrating a controlled polymerization. The influence of the isomer t‐butyl, i‐butyl, and n‐butyl on the kinetics, properties, and stereochemistry of the reactions was assessed. To the best of our knowledge, there is no previous report dealing with the synthesis of PiBA by any LRP approach in aqueous medium. The results presented in this work suggest that the stability provided by the acrylate side group has an important influence in the polymerization process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6542–6551, 2008