研究报告(191~196)基于微波技术的翻白草多糖提取工艺研究

采用醇沉水提工艺,使用微波技术提取翻白草中多糖.先通过单因素分析法对提取工艺进行优选,并选取4个因素进行正交实验.得到翻白草中多糖的最优提取工艺为:先使用料液比为1∶30的乙醇进行醇沉20 min,再以液固比为70∶1的水(p H为7.0)作为提取剂,在60℃下微波提取10 min.在最优提取工艺下对翻白草不同部位(根、茎、叶)的多糖含量进行分析,发现翻白草的茎部多糖的含量最高,其次为根部和叶部.     

Long-chain double SO3H-functionalized Brønsted acidic ionic liquids catalyzed selective alkylation of phenol and p-cresol with tert-butanol

A simple, efficient, and selective approach for the tert-butylation of phenol and p-cresol using two double SO₃H-functionalized long-chain Brønsted acidic ionic liquids as recyclable catalysts is reported. Under optimum reaction conditions, 89.4% conversion of the phenol and 73.7% selectivity of 2,4-tert-butyl-phenol and 93.2% conversion of the p-cresol and 89.2% selectivity of 2-tert-butyl-p-cresol were obtained. Two ionic liquids could be recovered readily and their catalytic activity almost completely retained after five recycles.     

Hydrothermal synthesis and structural characterization of organically-templated copper vanadium phosphates: the two-dimensional [{Cu2(bisterpy)}V3O5(HPO4)2(PO4)] (1) and the three-dimensional [{Cu2(bisterpy)}V2O5(HPO4)2] (2) (bisterpy=2,2′:4′,4″:2″,2‴-quarterpyridyl, 6′,6″-dipyridine)

The hydrothermal reactions of appropriate vanadium oxides and copper(II) salts with bisterpy in the presence of phosphoric acid or fluorophosphoric acid yield the Cu(II)-bisterpy/oxovanadium phosphate materials [{Cu₂(bisterpy)}V₃O₅(HPO₄)₂(PO₄)] (1) and [{Cu₂(bisterpy)}V₂O₅(HPO₄)₂] (2). Compound 1 is layered material, consisting of inorganic {V₃O₅(HPO₄)₂(PO₄)}_n⁴ⁿ⁻ chains propagating parallel to the crystallographic a-axis, linked in the second dimension through binuclear {Cu₂(bisterpy)}⁴⁺ units. The chain is constructed from corner-sharing {V₄O₁₀(PO₄)₂}⁶⁻ and {V₂O₂(PO₄)₄}⁶⁻ cluster building blocks. There are two distinct vanadium sites: a tetrahedral {V(V)O₄} site and a square pyramidal {V(IV)O₅} center. The Cu(II)-bisterpy subunits are linked to the vanadophosphate chains through phosphate oxygen atoms exclusively. In contrast, the structure of 2 is three-dimensional, exhibiting inorganic {Cu₂V₂O₅(HPO₄)₂}_n networks linked through bisterpy bridges to provide the overall three-dimensional connectivity. The oxovanadium subunit consists of the well-documented {V₂O₇} binuclear unit of corner-sharing tetrahedral.     

The preparation and characterization of nanoparticle TiO2/Ti films and their photocatalytic activity

Nanoparticle TiO₂/Ti films were prepared by a sol–gel process using Ti(OBu)₄ as raw material, the as-prepared film samples were also characterized by TG-DTA, XRD, TEM, SEM, XPS, DRS, PL, SPS and EFISPS testing techniques. TiO₂ nanoparticles experienced two processes of phase transition, i.e. amorphous to anatase and anatase to rutile at the calcining temperature range from 450 to 700 °C. TiO₂ nanoparticles calcined at 600 °C had similar composition, structure, morphology and particle size with the internationally commercial P-25 TiO₂ particles. Thus, the conclusion that 600 °C might be the most appropriate calcining temperature during the preparation process of nanoparticle TiO₂/Ti film photocatalysts could be made by considering the main factors such as the properties of TiO₂ nanoparticles, the adhesion of nanoparticle TiO₂ film to Ti substrate, the effects of calcining temperature on Ti substrate and the surface characteristics and morphology of nanoparticle TiO₂/Ti film for the practice view. The Ti element mainly existed on the nanoparticle TiO₂/Ti(3) film calcined at 600 °C as the chemical state of Ti⁴⁺, while O element mainly existed as three kinds of chemical states, i.e. crystal lattice oxygen, hydroxyl oxygen and adsorbed oxygen with increasing band energy. Its photoluminescence (PL) spectra with a peak at about 380 nm could be observed using 260 nm excitation, possibly resulting from the electron transition from the bottom of conduction band to the top of valence band. The PL peak position was nearly the same as the onset of its diffuse reflection spectra (DRS) and surface photovoltage spectroscopy (SPS), demonstrating that the effects of the quantum size on optical property were greater than that of the Coulomb and surface polarization. The PL spectra with two peaks related to the anatase and rutile, respectively, could be observed using the excited wavelength of 310 nm. Weak PL spectra could be observed using the excited wavelength of 450 nm, resulting from surface states. In addition, during the experimental process of the photocatalytic degradation phenol, the photocatalytic activity of nanoparticle TiO₂/Ti film with three layers calcined at 600 °C was the highest.     

二阶常微初值问题的时间间断最小二乘有限元法

采用时间间断最小二乘线性有限元方法求解二阶常微分方程初值问题.利用回收技巧及离散Gronwall引理证明了方法的稳定性.通过引入有限元空间上的范数,给出了方法在该范数意义下丰满的误差估计.数值实验验证了理论分析结果.     

Convergence of discrete time waveform relaxation methods

Numerical Algorithms - This paper concerns the discrete time waveform relaxation (DWR) methods for ordinary differential equations (ODEs). We present a general algorithm of constructing the DWR...     

3-取代-4(3H)-喹唑啉酮在酸性离子液体中的一锅法、微波辅助合成

研究以二种基于磺酸基官能团的Brфnsted酸性功能化离子液体:1-(4-磺酸基)苄基-3-甲基咪唑硫酸氢盐(a),N-(4-磺酸基)苄基吡啶硫酸氢根盐(b)作为反应介质与催化剂,2-氨基苯甲酸、原甲酸酯或甲酸、芳香胺或脂肪胺三组分为原料,在微波辐射下实现了3-取代-4(3H)-喹唑啉酮的一锅法快速合成.离子液体加入量10 mo1%,反应时间4～6min,目标化合物产率74%～94%.离子液体可循环使用3次,催化活性基本保持不变.此合成方法通用性强,3-位可引入芳基或烷基取代基,取代基电性效应小,拉电子取代基底物也可顺利反应.另外,反应可直接以85%甲酸作为C-2引入单元,目标化合物产率72%～91%.     

匀质悬链几何形状的力学研究

本文研究了匀质悬链的几何形状为悬链线和抛物线的力学条件;探讨了悬链形状与外力作用分布的一般关系;得到了一系列与悬链线有关的参数计算公式.     

拉脱法测量液体表面张力系数α实验误差分析

在液膜拉脱过程中,对吊环的受力以及受力的变化情况进行分析,以便正确测量求得液体表面张力,减少α的实验测量误差。