High selectively oxidative bromination of toluene derivatives by the H_2O_2-HBr system

An aqueous solution of hydrogen peroxide and hydrogen bromide illuminated by a 60 W incandescent light bulb serves as a source of bromine radicals.Various substituted toluenes（NO₂,Cl,Br,H,CH₃） were high selectively brominated at the benzyl position for monobromination in CH₂C1₂ at ice water with catalyst free.This simple but effective bromination of toluene derivatives with an aqueous H₂O₂-HBr system is characterized with the use of inexpensive reagents and a lower impact on the environment, which make it a good alternative to the existing bromination methods.     

A facile and efficient synthetic method for 4-phenylethynylphthalic anhydride

A novel approach to the synthesis of 4-phenylethynylphthalic anhydride has been described.The target compound was synthesized by Pd/Cu catalyzed Sonogashira coupling reaction between phenylacetylene and 4-bromophthalic acid which was for the first time employed as start material,followed by dehydration of 4-phenylethynylphthalic acid.Compared with traditional synthetic routes,this method provides several advantages such as readily available raw materials,convenient manipulation and high yield.The product...     

Structure and magnetic properties of Nb-doped FeZrB soft magnetic alloys

Structure and magnetic properties of Nb-doped (FeZrB)_100−xNb_x alloy are investigated by X-ray diffraction (XRD), differential scanning calorimetry and vibrating sample magnetometer. The fully amorphous structure of the as-quenched ribbons is confirmed by the XRD pattern. With increasing Nb, the glass transition temperature and the onset crystallization temperature are increased, indicating increased stability of the amorphous structure. For x=1, the saturation magnetization of the ribbons is 125.7 emu/g and the optimized annealing temperature increases from 550 to 630 °C. The morphology of the crystallized phases is observed by scanning electron microscopy. The results show that nanocrystalline α-Fe grains are dispersed in the amorphous matrix.     

Experimental study of infrared nanosecond laser ablation of silicon: The multi-pulse enhancement effect

Experimental study has been performed on nanosecond (ns) laser ablation of silicon at 1064 nm, through which a so-called “multi-pulse enhancement effect” has been revealed, which has been rarely reported in literature. The major features of this effect are: (1) for multi-pulse laser ablation at the same spatial location, the ablation efficiency increases as the pulse number increases and the pulse-to-pulse temporal distance decreases; (2) for multi-pulse ablation performed sequentially at a group of locations, the ablation quality and efficiency starting from the second location can be significantly enhanced if the distance between adjacent locations is sufficiently small. Further study is needed to confirm and understand the underlying physical mechanism for the multi-pulse enhancement effect, which can be utilized to significantly improve the quality and efficiency of laser silicon micromachining using the low-cost and low-energy-consumption infrared ns lasers. This may decrease the cost and energy consumption of many relevant areas, such as the solar cell industry.     

Discontinuous transition from free flow to synchronized flow induced by short-range interaction between vehicles in a three-phase traffic flow model

In this paper, we incorporate a limitation on the interaction range between neighboring vehicles into the cellular automaton model proposed by Gao and Jiang et al. [K. Gao, R. Jiang, S. X. Hu, B. H. Wang and Q. S. Wu, Phys. Rev. E 76 (2007) 026105], which was established within the framework of Kerner’s three-phase traffic theory and has been shown to be able to reproduce the three-phase traffic flow. This modification eliminates an unrealistic phenomenon found in the previous model, where the velocity-adaptation effect between neighboring vehicles can exist even if those vehicles are infinitely far away from each other. Therefore, in the improved model, we regulate that such interactions can only occur within a finite distance. For simplicity, we suppose a constant value to describe this distance in this paper. As a result, when compared to the previous model, the improved model mainly simulates the following results which are believed to be an improvement. (1) The improved model successfully reproduces the expected discontinuous transition from free flow to synchronized flow and the related “moving synchronized flow pattern”, which are both absent in the original model but have been observed in real traffic. (2) The improved model simulates the correlation functions, time headway distributions and optimal velocity functions which are all more consistent with the empirical data than the previous model and most of the other models published before. (3) Together with the previous two models considering the velocity-difference effect, this model finally accomplishes a significative process of developing traffic flow models from the traditional “fundamental diagram approach” to the three-phase traffic theory. This process should be helpful for us to understand the traffic dynamics and mechanics further and deeper.     

Solving the 100 Swiss Francs Problem

Sturmfels offered 100 Swiss Francs in 2005 to a conjecture, which deals with a special case of the maximum likelihood estimation for a latent class model. This paper confirms the conjecture positively.     

Surfactant-assisted preparation of nanohybrid for simultaneously improving enzyme-immobilization and electron-transfer in biosensor and biofuel cell

Journal of Solid State Electrochemistry - As enzyme-immobilization and electron-transfer are the key factors for fabricating an enzymatic bioelectrode and its devices, we investigated a strategy to...     

Global convergence property of modified Levenberg-Marquardt methods for nonsmooth equations

In this paper, we discuss the globalization of some kind of modified Levenberg-Marquardt methods for nonsmooth equations and their applications to nonlinear complementarity problems. In these modified Levenberg-Marquardt methods, only an approximate solution of a linear system at each iteration is required. Under some mild assumptions, the global convergence is shown. Finally, numerical results show that the present methods are promising.