Promotional Effects of Au in Pd-Au Catalysts for Vinyl Acetate Synthesis

Silica Supported Pd-Au bimetallic catalysts are highly selective for the acetoxylation of ethylene to vinyl acetate (VA). In this study we have used model catalysts consisting of planer surfaces and supported nanoparticles to investigate the promotional effects of Au in Pd-Au bimetallic catalysts. Low energy ion scattering spectroscopy, low energy electron diffraction, X-ray photoelectron spectroscopy, infrared reflection adsorption spectroscopy, and temperature-programmed desorption et al, were used to characterize the model systems. The catalytic performance for acetoxylation of ethylene to VA was examined for these model surfaces. In this paper, We summarize the Current understanding of the promotional effects of Au in Pd-Au bimetallic catalysts for VA synthesis. The key results are that An atoms break contiguous Pd atom ensembles at the surface into isolated Pd monomers. The absence of contiguous Pd sites significantly reduces the formation of combustion by-products and Suppresses the poison effects of CO, thus enhancing the VA formation selectivity and activity.Department of Energy, Office of Basic Energy, Division of Chemical Science ; Robert A. Welch Foundatio

Evolutionarily missing and conserved tRNA genes in human and avian

Viral infection heavily relies on host transfer RNA (tRNA) for viral RNA decoding. Counterintuitively, not all tRNA species based on anticodon are matched to all 64-triplet codons during evolution. Life solves this problem by cognate tRNA species via wobbling decoding. We found that 14 out of 64 tRNA genes in humans and the main avian species (chicken and duck) were parallelly missing, including 8 tRNA-A34NN and 6 tRNA-G34NN species. By analyzing the conservation of key motifs in tRNA genes, we found that box A and B served as intragenic tRNA promoters were evolutionally conserved among human, chicken, and duck. Thus, decoding viral RNA by similar wobbling strategies and tRNA transcripts may be

Effects of Inorganic Fillers on the Thermal and Mechanical Properties of Poly(lactic acid)

Addition of filler to polylactic acid (PLA) may affect its crystallization behavior and mechanical properties. The effects of talc and hydroxyapatite (HA) on the thermal and mechanical properties of two types of PLA (one amorphous and one semicrystalline) have been investigated. The composites were prepared by melt blending followed by injection molding. The molecular weight, morphology, mechanical properties, and thermal properties have been characterized by gel permeation chromatography (GPC), scanning electron microscope (SEM), instron tensile tester, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). It was found that the melting blending led to homogeneous distribution of the inorganic filler within the PLA matrix but decreased the molecular weight of PLA. Regarding the filler, addition of talc increased the crystallinity of PLA, but HA decreased the crystallinity of PLA. The tensile strength of the composites depended on the crystallinity of PLA and the interfacial properties between PLA and the filler, but both talc and HA filler increased the toughness of PLA

improving software testing process: feature prioritization to make winners of success-critical stakeholders

For a successful software project, acceptable quality must be achieved within an acceptable cost, demonstrating business value to customers and satisfactorily meeting delivery timeliness. Testing serves as the most widely used approaches to determine that the intended functionalities are performed correctly and achieve the desired level of services; however, it is also a labor-intensive and expensive process during the whole software life cycle. Most current testing processes are often technique-centered, rather than organized to maximize business value. In this article, we extend and elaborate the '4+1' theoretical lenses of Value-based Software Engineering (VBSE) framework in the software testing process; propose a multi-objective feature prioritization strategy for testing planning and controlling, which aligns the internal testing process with value objectives coming from customers and markets. Our case study in a real-life business project shows that this method allows reasoning about the software testing process in different dimensions: it helps to manage the testing process effectively and efficiently, provides information for continuous internal software process improvement, and increases customer satisfaction, which makes winners of all success-critical stakeholders (SCSs) in the software testing process. © 2010 John Wiley & Sons, Ltd.National Natural Science Foundation of China 90718042, 60873072, 60903050; National Hi-Tech RD Plan of China 2007AA010303; National Basic Research Program 2007CB310802For a successful software project, acceptable quality must be achieved within an acceptable cost, demonstrating business value to customers and satisfactorily meeting delivery timeliness. Testing serves as the most widely used approaches to determine that the intended functionalities are performed correctly and achieve the desired level of services; however, it is also a labor-intensive and expensive process during the whole software life cycle. Most current testing processes are often technique-centered, rather than organized to maximize business value. In this article, we extend and elaborate the '4+1' theoretical lenses of Value-based Software Engineering (VBSE) framework in the software testing process; propose a multi-objective feature prioritization strategy for testing planning and controlling, which aligns the internal testing process with value objectives coming from customers and markets. Our case study in a real-life business project shows that this method allows reasoning about the software testing process in different dimensions: it helps to manage the testing process effectively and efficiently, provides information for continuous internal software process improvement, and increases customer satisfaction, which makes winners of all success-critical stakeholders (SCSs) in the software testing process. © 2010 John Wiley & Sons, Ltd