具有记忆的污染物两维分散的描述

在污染物释放后的前期它的扩散过程受出口速度的影响而具有明显的记忆特性，本文将Ｒ．Ｓｍｉｔｈ［８］（１９８１）污染物纵向记忆描述理论推广到两维情况并给出了的解析表达式。     

Asymptotic solutions of the flow of a Johnson-Segalman fluid through a slowly varying pipe using double perturbation strategy

A double perturbation strategy is presented to solve the asymptotic solutions of a Johnson-Segalman (J-S) fluid through a slowly varying pipe. First, a small parameter of the slowly varying angle is taken as the small perturbation parameter, and then the second-order asymptotic solution of the flow of a Newtonian fluid through a slowly varying pipe is obtained in the first perturbation strategy. Second, the viscoelastic parameter is selected as the small perturbation parameter in the second perturbation strategy to solve the asymptotic solution of the flow of a J-S fluid through a slowly varying pipe. Finally, the parameter effects, including the axial distance, the slowly varying angle, and the Reynolds number, on the velocity distributions are analyzed. The results show that the increases in both the axial distance and the slowly varying angle make the axial velocity slow down. However, the radial velocity increases with the slowly varying angle, and decreases with the axial distance. There are two special positions in the distribution curves of the axial velocity and the radial velocity with different Reynolds numbers, and there are different trends on both sides of the special positions. The double perturbation strategy is applicable to such problems with the flow of a non-Newtonian fluid through a slowly varying pipe.     

Enhancement of saccharothriolide production and discovery of a new metabolite,saccharothriolide C2, by combined-culture of Saccharothrix sp. and Tsukamurella pulmonis

A combined-culture method was applied to saccharothriolide-producing strain Saccharothrix sp. A1506 with the mycolic acid-containing bacterium (MACB) Tsukamurella pulmonis TP-B0596. The combined-culture not only enhanced saccharothriolide production, but also produced saccharothriolide C₂, a new C-2 epimer of saccharothriolide C, thereby indicating its potential for increasing the chemical diversity of microbial metabolites.     

In-situ surface self-reconstruction in ternary transition metal dichalcogenide nanorod arrays enables efficient electrocatalytic oxygen evolution

Water splitting has received more and more attention because of its huge potential to generate clean and renewable energy.The highly active and durable oxygen evolution reaction(OER)catalysts play a decisive factor in achieving efficient water splitting.The identification of authentic active origin under the service conditions can prompt a more reasonable design of catalysts together with well-confined micro-/nano-structures to boost the efficiency of water splitting.Herein,Fe,Co,and Ni ternary transition metal dichalcogenide(FCND)nanorod arrays on Ni foam are purposely designed as an active and stable low-cost OER pre-catalyst for the electrolysis of water in alkaline media.The optimized FCND catalyst demonstrated a lower overpotential than the binary and unary counterparts,and a 27-fold rise in kinetic current density at the overpotential of 300 m V compared to the nickel dichalcogenide counterpart.Raman spectra and other structural characterizations at different potentials reveal that the in-situ surface self-reconstruction from FCND to ternary transition metal oxyhydroxides(FCNOH)on catalyst surfaces initiated at about 1.5 V,which is identified as the origin of OER activity.The surface selfreconstruction towards FCNOH also enables excellent stability,without fading upon the test for 50 h.     

A SIMPLE,EFFICIENT AND NEW METHOD FOR PREPARING AZO UREAS

Azo compounds are widely utilized as dyes and analytical reagents.They can also be used as materials for non-linear optics and for storage optical information in laser dish^[1]. Recently, many noteworthy studies have shown that azobenzene derivatives possess excellent optical memory and photoelectric properties^[2]. The preparation of ordinary azo compounds has been described in many references. However, those compounds generally bear alkyl or aryl groups on both sides of the azo linkage (-N=N-).     

Grafting modification and structural degradation of multi-walled carbon nanotubes under the effect of ultrasonics sonochemistry

Polyvinyl pyrrolidone (PVP) grafted multi-walled carbon nanotubes (MWCNTs) were prepared by the degradation effect of ultrasonics sonochemistry. PVP macroradicals formed by sonochemical degradation of a PVP solution were trapped by MWCNTs and grafted onto the surface of MWCNTs. It was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis that the PVP was covalently bonded on the MWCNTs. Transmission electron microscopy showed nanotubes in the grafted samples were shorter than the original MWCNTs due to the crushing effect of ultrasonics sonochemistry. Both the decrease in length of the MWCNTs and the PVP grafted onto them are beneficial for their dispersion in solvents.     

Two-Phase Dehydrogenation of Aryl Substituted Carbazide Compounds

Two-phase dehydrogenation, which is a new reaction of aryl substituted carbazide compounds, is described in this paper. Ten new azo compounds were synthesized by the reaction of aryl substituted carbazide compounds with a phenoxyl radical between two phases in good yields.     

Reduction of Azides to Amines With SmI2 or Cp2TiCl2-Sm System

Azides can be rapidly reduced to corresponding amines with SmI₂ (Method A) or Cp₂TiCl₂-Sm system (Method B) in good yields under mild conditions.     

非定常圆柱绕流的实验研究

本文采用流场显示方法研究单圆柱在非定常流动中的涡旋脱落规律。实验结果表明：在不同的ＫＣ数（ＫＣ＝Ｕ∞Ｔ／Ｄ）下，非常圆柱绕流的涡旋脱落特性是不相同的，一般随ＫＣ数值的增加，其涡旋脱落对数也增加，但有明显的阶梯性，同时圆柱分离点的周期变化后于流场的变化。