Preparative enantioseparation of propafenone by counter‐current chromatography using di‐n‐butyl l‐tartrate combined with boric acid as the chiral selector

This paper extends the research of the utilization of borate coordination complexes in chiral separation by counter‐current chromatography (CCC). Racemic propafenone was successfully enantioseparated by CCC with di‐n‐butyl l ‐tartrate combined with boric acid as the chiral selector. The two‐phase solvent system was composed of chloroform/ 0.05 mol/L acetate buffer pH 3.4 containing 0.10 mol/L boric acid (1:1, v/v), in which 0.10 mol/L di‐n‐butyl l ‐tartrate was added in the organic phase. The influence of factors in the enantioseparation of propafenone were investigated and optimized. A total of 92 mg of racemic propafenone was completely enantioseparated using high‐speed CCC in a single run, yielding 40–42 mg of (R)‐ and (S)‐propafenone enantiomers with an HPLC purity over 90–95%. The recovery for propafenone enantiomers from fractions of CCC was in the range of 85–90%.     

基于芯片的静电分束器

提出一个基于分子芯片, 由六个黄金电极构成的静电分束器。分束器的总长度大约10 mm。用经典的蒙特卡罗方法模拟极性分子被装载和分束的动力学过程。用此分束器, 可以得到固定的分束比为0.5:0.5。如果将两个电极杆切断, 通过改变电极电压就可以很容易地操控分束比。     

Bifurcations of travelling wave solutions for the Gilson–Pickering equation

In this paper, the qualitative behavior and exact travelling wave solutions of the Gilson–Pickering equation are studied by using the qualitative theory of polynomial differential system. The phase portraits of the system are given under different parametric conditions. Some exact travelling wave solutions of the Gilson–Pickering equation are obtained. Under different parametric conditions, various sufficient conditions to guarantee the existence of smooth and non-smooth travelling wave solutions are given.     

Surface energy as a barrier to creasing of elastomer films: an elastic analogy to classical nucleation

In a soft elastic film compressed on a stiff substrate, creases nucleate at preexisting defects and grow across the surface of the film like channels. Both nucleation and growth are resisted by the surface energy, which we demonstrate by studying creases for elastomers immersed in several environments-air, water, and an aqueous surfactant solution. Measurement of the position where crease channeling is arrested on a gradient thickness film provides a uniquely characterized strain that quantitatively reveals the influence of surface energy, unlike the strain for nucleation, which is highly variable due to the sensitivity to defects. We find that these experimental data agree well with the prediction of a scaling analysis.     

Profitless delays for extinction in nonautonomous Lotka-Volterra system

IntroductionCOnsider the folbeing 8ystem of differentiaJ equations'This system models competition among n species. Here xi(t) denotes the concentration of theith specthe at thoe t, and bi(t) is it5 growth rate at this time, a,j(t) denote the competitivecoefficient between the ith species and the jth species, and when i = j, aij(t) denotes thedensity-dependent rate of the ith species; n(t) is the time deviating argUments at time t(i,j = l,2,',n). As n(t) - 0 for j = l,',n, system (1) is k…     

Cavitation dynamics in a vitrimer

Acta Mechanica Sinica - Vitrimer is a polymer network with dynamic covalent bonds, which can be dynamically broken and reformed. Thanks to the dynamic covalent bonds, vitrimer behaves like an...