Selective Propene Epoxidation on Immobilized Au6–10 Clusters: The Effect of Hydrogen and Water on Activity and Selectivity

Epoxidation made easy : Subnanometer gold clusters immobilized on amorphous alumina result in a highly active and selective catalyst for propene epoxidation. The highest selectivity is found for gas mixtures involving oxygen and water, thus avoiding the use of hydrogen. Ab initio DFT calculations are used to identify key reaction intermediates and reaction pathways. The results confirm the high catalyst activity owing to the formation of propene oxide metallacycles. Al green, Au yellow, O red, and C gray.

     

Synthesis of nanoporous activated iridium oxide films by anodized aluminum oxide templated atomic layer deposition

Iridium oxide (IrOx) has been widely studied due to its applications in electrochromic devices, pH sensing, and neural stimulation. Previous work has demonstrated that both Ir and IrOx films with porous morphologies prepared by sputtering exhibit significantly enhanced charge storage capacities. However, sputtering provides only limited control over film porosity. In this work, we demonstrate an alternative scheme for synthesizing nanoporous Ir and activated IrOx films (AIROFs). This scheme utilizes atomic layer deposition to deposit a thin conformal Ir film within a nanoporous anodized aluminum oxide template. The Ir film is then activated by potential cycling in 0.1 M H₂SO₄ to form a nanoporous AIROF. The morphologies and electrochemical properties of the films are characterized by scanning electron microscopy and cyclic voltammetry, respectively. The resulting nanoporous AIROFs exhibit a nanoporous morphology and enhanced cathodal charge storage capacities as large as 311 mC/cm².     

Stabilization of Copper Catalysts for Liquid‐Phase Reactions by Atomic Layer Deposition

Atomic layer deposition (ALD) of an alumina overcoat can stabilize a base metal catalyst (e.g., copper) for liquid‐phase catalytic reactions (e.g., hydrogenation of biomass‐derived furfural in alcoholic solvents or water), thereby eliminating the deactivation of conventional catalysts by sintering and leaching. This method of catalyst stabilization alleviates the need to employ precious metals (e.g., platinum) in liquid‐phase catalytic processing. The alumina overcoat initially covers the catalyst surface completely. By using solid state NMR spectroscopy, X‐ray diffraction, and electron microscopy, it was shown that high temperature treatment opens porosity in the overcoat by forming crystallites of γ‐Al₂O₃. Infrared spectroscopic measurements and scanning tunneling microscopy studies of trimethylaluminum ALD on copper show that the remarkable stability imparted to the nanoparticles arises from selective armoring of under‐coordinated copper atoms on the nanoparticle surface.     

Enhanced nucleation, smoothness and conformality of ultrananocrystalline diamond (UNCD) ultrathin films via tungsten interlayers

Extremely smooth (6 nm RMS roughness over 4 μm²), thin (100 nm), and continuous ultrananocrystalline diamond (UNCD) films were synthesized by microwave plasma chemical vapor deposition using a 10 nm tungsten (W) interlayer between the silicon substrate and the diamond film. These UNCD films possess a high content of sp³-bonded carbon. The W interlayer significantly increased the initial diamond nucleation density, thereby lowering the surface roughness, eliminating interfacial voids, and allowing thinner UNCD films to be grown. This structural optimization enhances the films’ properties and enables its integration with a wide variety of substrate materials.     

教师教学水平的时齐马尔可夫链评估方法

采用时齐马尔可夫链方法给出了一种评估教师教学水平的方法,对文［１］所给方法做了适当的改进,拓宽了该方法的应用范围,在多民族院校,使用本法可以克服由于学生基础不同等多方面的原因造成难以比较教师教学水平的难题．     

A survey of knowledge-based systems research in decision sciences (1980–1995)

Research in knowledge-based systems (KBS) has become an important area of inquiry within decision sciences. In this paper, we present the results of an extensive survey of research papers published on this topic. We determined frequency counts of papers and we also performed a content analysis of the papers we surveyed. The results indicate that there are a large number of studies informing us of the design and development issues relating to KBS. However, there seems to be less research examining issues relating to the management and impact of KBS on individuals and organisations. We summarise our key findings and identify avenues for future research.