用于矢量水听器的低频高灵敏度层合梁加速度传感器

压电加速度传感器是同振型矢量水听器的核心部件。为了满足低频高灵敏度矢量水听器的应用需求,提出并研究一种具有层合梁结构的低频高灵敏度加速度传感器。结合弹性力学和压电方程推导层合梁加速度传感器的加速度灵敏度解析解表达式,通过有限元仿真对层合梁加速度传感器尺寸进行优化,给出优化后的尺寸范围。从优化的尺寸范围中选取两种不同尺寸进行加速度传感器振动特性的仿真分析及实物制作(其中压电材料为PZT-5)与性能测试。仿真与测试结果均表明,相比已有的同尺寸金属梁加速度传感器,层合梁加速度传感器可以有效降低谐振频率并提升加速度灵敏度。当压电层厚度为0.5 mm时,加速度灵敏度最大提升3.9 dB,谐振频率下降23%。测试结果与理论分析相符。     

光谱技术分析尿素对BSA糖基化反应的影响

以牛血清白蛋白(BSA)和葡萄糖为原料,采用光谱技术从分子水平上研究不同浓度尿素(0～7 mol·L-1)对BSA糖基化反应的影响.结果表明:BSA经过尿素处理后,其糖基化产物的自由氨基含量和内源荧光强度均显著下降;同步荧光光谱表明BSA与尿素的结合点更接近于色氨酸(Trp)残基;紫外光谱分析表明经尿素处理后BSA的糖...     

Combined use of ionic liquid and β‐CD for enantioseparation of 12 pharmaceuticals using CE

In this study, the enantioseparation of zopiclone, repaglinide, chlorphenamine maleate, brompheniramine maleate, dioxopromethazine hydrochloride, promethazine hydrochloride, liarozole, carvedilol, homatropine hydrobromide, homatropine methylbromide, venlafaxine, and sibutramine hydrochloride has been investigated using β‐CD in combination with a chiral ionic liquid (IL), 1‐ethyl‐3‐methylimidazolium‐L‐lactate. The influence of the type of IL and its concentration, BGE pH, and chain length of the IL cations on the resolution are discussed. Finally, the proposed method was successfully applied for the chiral impurity determination of eszopiclone in pharmaceutical tablets after validation with respect to accuracy and precision, linearity range, selectivity, repeatability, LOD and LOQ. It is assessed that the chiral impurity determination in the commercial tables is fewer than 0.1%.     

Preservation of entanglement in a two-qubit-spin coupled system

A theoretical scheme for preserving the entanglement in a two-qubit-spin coupled system in the presence of Dzyaloshinskii–Moriya (DM) anisotropic antisymmetric interaction is proposed. On the basis of a sequence of operations performed periodically on the system, the scheme can preserve the entanglement of the system starting from any initial state with any desired high precision for any desired long duration.     

About macroscopic models of instability pattern formation

Various macroscopic models to describe instability pattern formation are discussed in this paper. They are similar to the Ginzburg–Landau envelope equation, but they can remain valid away from the bifurcation and are based on the technique of Fourier series with slowly varying coefficients. We focus on two questions: the need to take phase changes into account and the boundary conditions to be associated with macroscopic models. The analysis is carried out on the basis of numerical simulations for the problem of a compressed beam on a nonlinear foundation that is quite similar to the well known Swift–Hohenberg equation. The first macroscopic model involves a real envelope so that the phase is assumed to be constant. The second model is also macroscopic and it is a sort of Ginzburg–Landau equation with a complex envelope. The third one follows from a multi-scaled approach with a numerical bridging between the full model near the boundary and a macroscopic model in the bulk.     

Nanoscale-confined crystallization in epoxy resin and polyethylene-block-poly(ethylene oxide) diblock copolymer blends

In this paper, the nanoscale-confined crystallization behavior and crystallization kinetics in blends of double-crystalline polyethylene-block-poly(ethylene oxide) (PE-b-PEO) diblock copolymer with diglycidyl ether of bisphenol A epoxy resin were investigated. The results showed that there appeared three crystallization regimes related to the crystallization of the PE block within three different microenvironments in the epoxy resin/PE-b-PEO blends. The Avrami index n is around 1.8–2.4, suggesting PE block of the copolymer in the blends exhibited nanoscale-confined crystallization behavior by homogeneous nucleation. The PE block nanoscale-confined crystallization is ascribed to the formation of the strong intermolecular hydrogen bonding interaction between hydroxyl groups of amine-cured epoxy and ether oxygen atoms of PEO, as seen from Fourier transform infrared spectroscopy spectra.     

高效液相色谱法同时测定纺织品中10种酚类化合物

建立了高效液相色谱法同时测定纺织品中五氯苯酚、2,3,4,5-四氯苯酚、2,3,4,6-四氯苯酚、2,3,5,6-四氯苯酚、2,4,5-三氯苯酚、2,4,6-三氯苯酚、邻苯基苯酚、间羟基联苯、2-萘酚、对硝基苯酚10种酚类化合物的检测方法。纺织品中的酚类化合物经甲醇超声提取、浓缩后,以ZORBAX SB-C18柱(4.6 mm×150 mm,5μm)为分析柱,乙腈和0.01 mol/L磷酸溶液为流动相梯度洗脱,采用二极管阵列检测器,在220 nm和310 nm波长下进行高效液相色谱检测,紫外光谱库确证,外标法定量。10种酚类化合物在0.3～37 mg/L浓度范围内与其峰面积呈良好的线性关系,相关系数为0.999 1～0.999 5;以不低于3倍的信噪比计算10种酚类化合物的检出限(LOD)为0.003 0～0.041 1 mg/kg;定量下限(LOQ,S/N≥10)为0.010 0～0.1370 mg/kg。棉、麻、毛3种纺织品基质在3个不同加标水平的回收率为81%～105%,相对标准偏差(RSDs)为1.7%～8.5%。该方法能同时完成10种酚类化合物的确证和分析,可用于纺织品中酚类化合物残留的检测分析。     

合成2-丁基-1,3-二氮杂螺[4.4]壬-1-烯-4-酮的工艺改进

以1-氨基环戊腈草酸盐为起始原料,经双氧水水解、戊酰氯酰化、环合制得厄贝沙坦的关键中间体——2-丁基-1,3-二氮杂螺[4.4]壬-1-烯-4-酮,总产率80.9%,其结构经1H NMR,13C NMR和MS确证。     

Synthesis,isolation and characterization of methyl levulinate from cellulose catalyzed by extremely low concentration acid

A direct synthesis of methyl levulinate from cellulose alcoholysis in methanol medium under mild condition (180–210 °C) catalyzed by extremely low concentration sulfuric acid (≤0.01 mol/L) and the product isolation were developed in this study. Effects of different process variables towards the catalytic performance were performed as a function of reaction time. The results indicated that sulfuric acid concentration, temperature and initial cellulose concentration had significant effects on the synthesis of methyl levulinate. An optimized yield of around 50% was achieved at 210 °C for 120 min with sulfuric acid concentration of 0.01 mol/L and initial cellulose concentration below 100 g/L. The resulting product mixture was isolated by a distillation technique that combines an atmospheric distillation with a vacuum distillation where n-dodecane was added to help distill the heavy fraction. The light fraction including mainly methanol could be reused as the reaction medium without any substantial change in the yield of methyl levulinate. The chemical composition and structural of lower heavy fraction were characterized by GC/MS, FTIR, ¹H-NMR and ¹³C-NMR techniques. Methyl levulinate was found to be a major ingredient of lower heavy fraction with the content over 96%. This pathway is efficient, environmentally benign and economical for the production of pure levulinate esters from cellulose.     

A simple microextraction and preconcentration approach based on a mixed matrix membrane

A simple adsorption/desorption procedure using a mixed matrix membrane (MMM) as extraction medium is demonstrated as a new miniaturized sample pretreatment and preconcentration technique. Reversed-phase particles namely polymeric bonded octadecyl (C₁₈) was incorporated through dispersion in a cellulose triacetate (CTA) polymer matrix to form a C₁₈-MMM. Non-steroidal anti-inflammatory drugs (NSAIDs) namely diclofenac, mefenamic acid and ibuprofen present in the environmental water samples were selected as targeted model analytes. The extraction setup is simple by dipping a small piece of C₁₈-MMM (7 mm × 7 mm) in a stirred 10 mL sample solution for analyte adsorption process. The entrapped analyte within the membrane was then desorbed into 100 μL of methanol by ultrasonication prior to high performance liquid chromatography (HPLC) analysis. Each membrane was discarded after single use to avoid any analyte carry-over effect. Several important parameters, such as effect of sample pH, salting-out effect, sample volume, extraction time, desorption solvent and desorption time were comprehensively optimized. The C₁₈-MMM demonstrated high affinity for NSAIDs spiked in tap and river water with relative recoveries ranging from 92 to 100% and good reproducibility with relative standard deviations between 1.1 and 5.5% (n = 9). The overall results obtained were found comparable against conventional solid phase extraction (SPE) using cartridge packed with identical C₁₈ adsorbent.