Redox functionality mediated by adsorbed oxygen on a Pd-oxide film over a Pd(100) thin structure: A first-principles study

Stable oxygen sites on a PdO film over a Pd(100) thin structures with a (sqrt{5} times sqrt{5}) R27^circ surface-unit cell are determined using the first-principles electronic structure calculations with the generalized gradient approximation. The adsorbed monatomic oxygen goes to a site bridging two 2-fold-coordinated Pd atoms or to a site bridging a 2-fold-coordinated Pd atom and a 4-fold-coordinated Pd atom. Estimated reaction energies of CO oxidation by reduction of the oxidized PdO film and N_2O reduction mediated by oxidation of the PdO film are exothermic. Motion of the adsorbed oxygen atom between the two stable sites is evaluated using the nudged elastic band method, where an energy barrier for a translational motion of the adsorbed oxygen may become sim 0.45 eV, which is low enough to allow fluxionality of the surface oxygen at high temperatures. The oxygen fluxionality is allowed by existence of 2-fold-coordinated Pd atoms on the PdO film, whose local structure has similarity to that of Pd catalysts for the Suzuki-Miyaura cross coupling. Although NO_x (including NO_2 and NO) reduction is not always catalyzed only by the PdO film, we conclude that there may happen continual redox reactions mediated by oxygen-adsorbed PdO films over a Pd surface structure, when the influx of NO_x and CO continues, and when the reaction cycle is kept on a well-designed oxygen surface.Comment: 15 pages, 6 figures, submitted to J. Phys. Condens. Matte

Lateral Flow Deformation Evaluation of Ground-Structure System under Various Cyclic Loading Conditions

In order to clarify the mechanical behaviors of sand grounds induced by various loadings including sea wave forces, traffic vibrations and earthquake etc., a series of model tests were carried out on model structure-ground system by using, the two-dimensional plane strain soil box apparatus. It was found that; (1) the lateral flow behavior of ground depends strongly on settlement performance of a structure, (2) the bearing capacity of ground may be evaluated by a failure envelope which is depicted in M-V-H plane irrespective of the difference in loading conditions and (3) the stability of sand ground-structure system can be assessed on the basis of a parameter Vσ/ Vρ which quantifies the lateral flow deformation

A before and after comparison of the effects of forest walking on the sleep of a community-based sample of people with sleep complaints

<p>Abstract</p> <p>Background</p> <p>Sleep disturbance is a major health issue in Japan. This before-after study aimed to evaluate the immediate effects of forest walking in a community-based population with sleep complaints.</p> <p>Methods</p> <p>Participants were 71 healthy volunteers (43 men and 28 women). Two-hour forest-walking sessions were conducted on 8 different weekend days from September through December 2005. Sleep conditions were compared between the nights before and after walking in a forest by self-administered questionnaire and actigraphy data.</p> <p>Results</p> <p>Two hours of forest walking improved sleep characteristics; impacting actual sleep time, immobile minutes, self-rated depth of sleep, and sleep quality. Mean actual sleep time estimated by actigraphy on the night after forest walking was 419.8 ± 128.7 (S.D.) minutes whereas that the night before was 365.9 ± 89.4 minutes (n = 42). Forest walking in the afternoon improved actual sleep time and immobile minutes compared with forest walking in the forenoon. Mean actual sleep times did not increase after forenoon walks (n = 26) (the night before and after forenoon walks, 380.0 ± 99.6 and 385.6 ± 101.7 minutes, respectively), whereas afternoon walks (n = 16) increased mean actual sleep times from 342.9 ± 66.2 to 475.4 ± 150.5 minutes. The trend of mean immobile minutes was similar to the abovementioned trend of mean actual sleep times.</p> <p>Conclusions</p> <p>Forest walking improved nocturnal sleep conditions for individuals with sleep complaints, possibly as a result of exercise and emotional improvement. Furthermore, extension of sleep duration was greater after an afternoon walk compared to a forenoon walk. Further study of a forest-walking program in a randomized controlled trial is warranted to clarify its effect on people with insomnia.</p

Palladium nanoparticles on carbon nanotubes as catalysts of cross-coupling reactions

The macroscopic properties of composite nanotube-nanoparticle superstructures are determined by a complex interplay of structural parameters at the nanoscale. The catalytic performance of different carbon nanotube-palladium nanoparticle catalysts, where nanoparticles were formed either directly onto nanotubes or preformed prior to deposition on nanotubes using different types of surfactants, were tested 10 in cross-coupling reactions. The decoration of multi-walled carbon nanotubes with preformed thiolate-stabilised palladium nanoparticles yielded the optimum catalyst, exhibiting high activity and stability towards carbon-carbon bond formation and excellent recyclability, retaining high activity from cycle to cycle. The type of carbon nanotube support has pronounced effects on the density of deposited nanoparticles, with more polarisable MWNT able to uptake the highest number of nanoparticles per unit 15 surface area as compared to other carbon nanostructures (MWNT>DWNT>SWNT~GNF). Microscopic investigation of the nanoscale morphology found that nanoparticles increase in size during catalysis. The extent of growth is dependent on the type of nanocarbon support, with wider MWNT possessing lower curvature and thus retarding the growth and coalescence of nanoparticles to a greater extent than other carbon nanostructures (SWNT>>DWNT>MWNT~GNF). The type of halogen X in the C-X bond 20 activated by palladium appears to influence the evolution of nanoparticles during catalysis, with X=Br having the greatest effect as compared to X=Cl or I. Overall, preformed thiolate-stabilised palladium nanoparticles deposited on MWNT from solution was found to possess the most functional catalytic properties, with optimum activity, stability and recyclability in a range of cross-coupling reactions

Residual stress effect on crack propagation in friction stir welded joints

Orientador: Renato PavanelloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: Inúmeros trabalhos de pesquisa tem sido feitos em torno de um processo de soldagem por atrito conhecido por FSW, ou Friction Stir Welding. A proposta deste trabalho é determinar o efeito das tensões residuais resultantes de tal processo sobre a propagação de trincas na região próxima à junta soldada. Este efeito é considerado calculando-se fatores de intensidade de tensão residual pelo uso de funções ponderadoras e pelo método de elementos finitos. Técnicas numéricas e equações de taxa de propagação modificadas são empregadas para determinar a vida residual em fadiga de sólidos com trincas que atravessam transversalmente a região da solda. É abordado e aplicado um meio de determinar uma curva de tensão residual longitudinal a partir de uma curva de fatores de intensidade de tensão residual. Finalmente, o ensaio cut compliance é apresentado como uma técnica experimental eficaz na determinação de uma curva de fatores de intensidade de tensão residual. A aplicação de tal método exige o conhecimento prévio ou o cálculo de funções de influência. Demonstra-se que o método de elementos finitos é eficaz na determinação de tais funçõesAbstract: Numerous research papers have been published on a process known as friction stir welding or FSW. The purpose of this work is to determine the effect of residual stresses resulting from such process on the propagation of a crack near the weld. This effect is taken into account by calculating residual stress intensity factors using weight functions and finite elements. Numerical techniques and crack propagation rate equations are employed to determine residual fatigue life of solids with cracks that traverse across the weld region. A way to determine a longitudinal residual stress curve from a residual stress intensity factor curve is discussed and applied in this work. Finally, the cut compliance method is presented as an effective experimental technique to determine residual stress intensity factor curves. The application of such method requires calculation of influence functions. It is shown that the finite element method is effective in determining those functionsMestradoMecanica dos Sólidos e Projeto MecanicoMestre em Engenharia Mecânic

Recombinant human interleukin 6 (B-cell stimulatory factor 2) is a potent inducer of differentiation of mouse myeloid leukemia cells (M1)

AbstractRecombinant human interleukin 6 (IL-6), a lymphokine involved in the final differentiation of activated B-cells into antibody-forming cells, greatly suppressed proliferation and induced differentiation of murine myeloid leukemia cells (M1) into mature macrophage-like cells. When M1 cells were treated with IL-6, their growth was completely arrested as early as on day 2, and they were induced to differentiate morphologically into macrophage-like cells. Differentiation-associated properties such as phagocytic activity, adherence to the dish surface, Fc and C3 receptors, were also induced within 24 h by IL-6, and they reached their respective maximal levels on day 2 or 3. The potency of IL-6 in suppressing proliferation and inducing differentiation was much greater than that of 1α,25-dihydroxyvitamin D3 one of the most potent inducers of M1 cells. The present report indicates that IL-6 is involved in the differentiation of not only B-cells but also myeloid leukemia cells

2-Bromo-p-terphen­yl

In the title compound, C18H13Br, the dihedral angles between the mean planes of the central benzene ring and the mean planes of the outer phenyl and bromo­phenyl rings are 33.47 (8) and 66.35 (8)°, respectively. In the crystal, weak C—H⋯π and inter­molecular Br⋯Br [3.5503 (15) Å] inter­actions contribute to the stabilization of the packing