新型双β-二酮配体的合成

没食子酸甲酯与乙酰丙酮反应合成了一种新型双β-二酮配体--1,5-二(3,4,5-三羟基)苯甲酰基乙酰丙酮(L),收率84.3%,其结构经1H NMR,FT-IR,TG-DTA和元素分析表征.L具有较好的热稳定性,分解温度高于200 ℃.     

光致噻吨酮与胺类、酚类、醇类的电子转移和氢转移反应

利用激光闪光光解方法研究了一系列胺类、酚类、醇类在脱氧乙腈中猝灭噻吨酮(TX)三重态的反应,得到了相应的瞬态吸收光谱和猝灭速率常数(kq).通过对光谱演变特性的分析,推断出三重态噻吨酮与不含有活泼氢的胺发生了电子转移反应,与含有活泼氢的胺发生了电子-质子转移反应.三重态噻吨酮与酚类、醇类反应中观察到噻吨酮加氢自由基的生成,据此推断出三重态噻吨酮与酚类、醇类发生了氢转移反应.胺类的猝灭速率常数随着反应自由能变(ΔG)的增大而减小,说明电子转移影响了噻吨酮三重态的猝灭.酚类的猝灭速率常数先随ΔG增大而减小,后随酚阳离子的酸性增强逐渐增大,可能是猝灭过程中电子转移影响减弱的同时氢转移影响逐渐增强.醇类的猝灭速率常数随着醇的α-C—H键能的增大而减小,说明α-C—H键能是影响噻吨酮三重态猝灭的关键因素.比较以前研究的胺类、酚类、醇类与三重态呫吨酮(XT)、芴酮(FL)反应的结果可知,由于分子结构差异性的影响,相关的猝灭速率常数按照呫吨酮、噻吨酮、芴酮的顺序逐渐减小.     

Global regularity for modified critical dissipative quasi-geostrophic equations

We consider the n-dimensional modified quasi-geostrophic (SQG) equations

t_∂θ + u . ∇θ + κΛαθ = 0,${\partial }_t\theta \hspace{0.17em}+\hspace{0.17em}u\hspace{0.17em}.\hspace{0.17em}\nabla \theta \hspace{0.17em}+\hspace{0.17em}\kappa {\Lambda }^{\alpha }\theta \hspace{0.17em}=\hspace{0.17em}0,$

u = Λα-1 R^⊥θ$u\hspace{0.17em}=\hspace{0.17em}{\Lambda }^{\alpha -1}\hspace{0.17em}{R}^{\perp }\theta$

with κ > 0, α ∈ (0,1] and θ₀ ∈ W1, ∞ (?ⁿ). In this paper, we establish a different proof for the global regularity of this system. The original proof was given by Constantin, Iyer, and Wu [5], who employed the approach of Besov space techniques to study the global existence and regularity of strong solutions to modified critical SQG equations for two dimensional case. The proof provided in this paper is based on the nonlinear maximum principle as well as the approach in Constantin and Vicol [2].     

三维Boussinesq方程组大解的全局L~2稳定性

对三维有界及无界区域上的Boussinesq方程的全局L~2稳定性进行了讨论.在解满足适当的条件下,证明了此解为稳定的,并得出此稳定性条件的等价性条件,最后得出了二维Boussinesq方程组在三维扰动下的解的全局存在性和稳定性.     

Gd~(3+)掺杂浓度对NaErF_4∶Yb纳米晶上转换荧光性能的影响

采用温和的溶剂热法制备较强红光发射的NaErF4∶Yb,Gd上转换纳米晶,控制Gd~(3+)的掺杂浓度实现了晶相和尺寸可控以及上转换荧光的增强。X射线衍射谱(XRD)、透射电子显微镜图像(TEM)和上转换发射光谱结果分析表明,Gd~(3+)掺杂可以有效地促进NaErF_4纳米晶的晶相由立方相向六角相转变,并且减小纳米粒子的尺寸。随着Gd~(3+)掺杂浓度的上升,上转换荧光强度明显增大。当Gd~(3+)摩尔分数为25%时,样品的上转换荧光强度达到最大。同时,研究了在980 nm近红外激光激发下,Yb~(3+)与Er~(3+)间有效的能量传递以及上转换发光机制。     

Reflection and Transmission of Plane Waves at a Water–Porous Sediment Interface with a Double-Porosity Substrate

This paper investigates the wave propagation at the interface between the ocean and the ocean floor. The ocean floor is assumed to be composed of covered porous sediment with an underlying double-porosity substrate. For this purpose, plane wave reflection and transmission in the coupled water–porous sediment–double-porosity substrate system are analytically solved in terms of displacement potentials. Using numerical examples, the effects of the material properties of the underlying double-porosity substrate on the reflection coefficients are discussed in detail. Variations in pore and fracture fluid, fracture volume fraction, and permeability coefficients are considered. In addition, two cases of boundary conditions at the porous sediment–double-porosity substrate interface, i.e., sealed-pore boundary and open-pore boundary, are compared in the numerical calculations. Results show that material property variations in the double-porosity substrate may significantly affect the reflected wave in the overlying water if the sandwiched sediment depth is less than the critical value.     

Existence of Weak Solutions of Two-dimensional Euler Equations with Initial Vorticity in Lorentz Space L （2,1） （ R^2）

Some estimates on 2-D Euler equations are given when initial vorticity ω0 belongs to a Lorentz space L(2, 1). Then based on these estimates, it is proved that there exist global weak solutions of two dimensional Euler equations when ωo ∈ L(2, 1).     

土槿皮酸类化合物的质谱研究

本文系统地研究了土槿皮甲酸、乙酸和丙酸及其衍生物的质谱.通过质谱-结构关系的分析、高分辨质谱及亚稳数据的测定,阐明了它们在电子轰击下的裂解反应机制.     

丙烯酰胺与4-乙烯基吡啶共聚物的季胺化及其若干性能

将丙烯酰胺 (AM)与 4 乙烯基吡啶 (4VP)的共聚物 (P(AM co 4VP) )用硫酸二甲酯季铵化 ,制备了系列吡啶季铵盐型阳离子丙烯酰胺共聚物 ,用FTIR、1 H NMR和紫外分光光度法表征了其分子结构与组成 ,并重点研究了其絮凝与缓蚀性 ,考察了阳离子度与分子量对其各种功能的影响 .研究结果表明 ,吡啶季铵盐型阳离子丙烯酰胺共聚物具有优良的絮凝 缓蚀等功能 ,且阳离子度越高 ,性能越好 ,而分子量对其性能亦有显著的影响 .     

Global Weak Solutions to One-Dimensional Compressible Navier-Stokes Equations with Density-Dependent Viscosity Coefficients

We prove the global existence of weak solutions of the one-dimensional compressible Navier-stokes equations with density-dependent viscosity. In particular, we assume that the initial density belongs to L^1 and L^∞, module constant states at x = -∞ and x = ＋∞, which may be different. The initial vacuum is permitted in this paper and the results may apply to the one-dimensional Saint-Venant model for shallow water.