Nickel-catalyzed hydrosilylation/cyclization of difluoro-substituted 1,6-enynes

Ni-catalyzed hydrosilylative cyclization of difluoro-substituted 1,6-enynes can be carried out. The presence of a geminal-difluoromethylene group at an alkene terminus in enynes is essential for the reaction to proceed.     

Highly durable Pd metal catalysts for the oxygen reduction reaction in fuel cells; coverage of Pd metal with silica

Pd cathode catalysts for polymer electrolyte fuel cells have been covered with silica layers a few nanometres thick. The silica-coated Pd catalysts showed high activity and excellent durability for the oxygen reduction under the severe cathode conditions of PEFCs, while Pd catalysts without silica-coating were seriously deactivated under the same conditions. The coverage of Pd metal with silica prevents the diffusion of Pd species out of the silica layers.     

Large‐scale SPH simulations of droplet impact onto a liquid surface up to the consequent formation of Worthington jet

In this study, the whole process of liquid droplet impact onto a liquid surface up to the consequent formation of the central column was simulated using the smoothed particle hydrodynamics method (SPH), and compared with an experiment using a high‐speed video camera. The surface tension tensor for the particle‐based expression was adequately included as the gradient of the surface tension and that enabled the simulation leading to the formations of crater and crown as well as the consequent central column. The simulated time series of the crater depth and diameter and crown height corresponded quantitatively well with the experimental result up to the rebound motion while discrepancies remained as a lower central column height in the simulation, and this seemed to be ascribed to the difficulty in realizing the complex surface structure that inevitably appeared in the fast rebound motion. Copyright © 2009 John Wiley & Sons, Ltd.     

Asymptotic distributions of regression and autoregression coefficients with martingale difference disturbances

In this paper a form of the Lindeberg condition appropriate for martingale differences is used to obtain asymptotic normality of statistics for regression and autoregression. The regression model is y_t = Bz_t + v_t. The unobserved error sequence {v_t} is a sequence of martingale differences with conditional covariance matrices {Σ_t} and satisfying sup_{t=1,…, n} {v′_tv_tI(v′_tv_t>a) |z_t, v_t−1, z_t−1, …} 0 as a → ∞. The sample covariance of the independent variables z₁, …, z_n, is assumed to have a probability limit M, constant and nonsingular; max_t=1,…,nz′_tz_t/n 0. If (1/n)Σ_t=1ⁿΣ_t Σ, constant, then √nvec( _n−B) N(0,M⁻¹Σ) and _n Σ. The autoregression model is x_t = Bx_{t − 1} + v_t with the maximum absolute value of the characteristic roots of B less than one, the above conditions on {v_t}, and (1/n)Σ_t=max(r,s)+1(Σ_tv_t−1−rv′_t−1−s) δ_rs(ΣΣ), where δ_rs is the Kronecker delta. Then √nvec( _n−B) N(0,Γ⁻¹Σ), where Γ = Σ_{s = 0}^∞B^sΣ(B′)^s.     

A Small One-Fiber WDM Optical Ethernet PC Card for FTTD

A new generation of network interface card for fiber-to-the-desktop has been fabricated. The fabricated card is PC-card size and suitable for notebook PCs. It could become the key element in the coming optical Ethernet age.     

Novel regular network polyester films from benezenetricarboxylic acids and glycols

Novel regular network polyester films were prepared from benzenetricarboxylic acids of trimesic (Y) and trimellitic (Z) acids, and glycols of ethylene (2G), tetramethylene (4G), and hexamethylene (6G) glycols. Prepolymers prepared by melt polycondensation for a short period within 1 h were cast from a DMF solution and successively post-polymerized at various temperatures and times to form a network. The resultant films were transparent, flexible, and insoluble in any solvents. Distortion temperature measured by a penetration mode of thermomechanical analysis (TMA) increased with increasing post polymerization time and temperature, and leveled out at 222, 168, 125 and 75°C, for the 2GY, 2GZ, 4GY, and 6GY films, respectively. Temperatures close to 400°C at which the probe had completely penetrated corresponded to the thermal decomposition temperature of these films. Two broad but strong peaks in the x-ray diffraction curves appears for the 2GY, 4GY, and 6GY, suggesting the formation of some ordered supramolecular structure owing to the regular network formed by symmetrical trimesic acid moiety, and the intensity of diffraction peaks became higher with increasing length of the methylene chain of the glycol monomer. Densities of the 2GY and 2GZ films decreased with increasing post-polymerization time and temperature. Tensile strength and Young's modulus increased and elongation decreased with increasing network formation. These tensile properties was affected by the chemical structure of the network films.     

Large-time existence of surface waves in incompressible viscous fluids with or without surface tension

Communicated by P.-L. Lions     

Nickel-catalyzed reductive cleavage of aryl alkyl ethers to arenes in absence of external reductant

The reductive cleavage of the C–O bonds of aryl ethers has great potential in organic synthesis. Although several catalysts that can promote the reductive cleavage of aryl ethers have been reported, all such systems require the use of an external reductant, e.g., hydrosilane or hydrogen. Here, we report the development of a new nickel-based catalytic system that can cleave the C–O bonds of ethers in the absence of an external reductant. The hydrogen atom required in this new reductive cleavage reaction is provided by the alkoxy group of the substrate, which serves as an internal reductant. The absence of an external reductant enables the unique chemoselectivity, i.e., the selective reduction of an alkoxy group over alkenes and ketones.