Platinum(II) complex-catalyzed enantioselective aldol reaction with ketene silyl acetals in DMF at room temperature

[{(R)-binap}Pt(μ-OH)]₂2X is a weak Lewis acid, which can catalyze the enantioselective aldol reaction of aldehydes with ketene silyl acetals in DMF at room temperature. The platinum(II) complex-catalyzed the enantioselective aldol reaction of aldehydes with 1-methoxy-2-methyl-(1-trimethylsilyloxy)propene gave the corresponding aldols in high yields with enantioselectivity up to 92%. With 5 mol % loading of the complexes, the enantioselective aldol reaction of aldehydes with 1-benzyloxy-1-(trimethylsilyloxy)propene smoothly proceeded in DMF containing 10% HMPA as to predominantly give anti-propionates with enantioselectivity up to 89%, irrespective of the silyl nucleophile geometry.     

Electrowetting — From statics to dynamics

More than one century ago, Lippmann found that capillary forces can be effectively controlled by external electrostatic forces. As a simple example, by applying a voltage between a conducting liquid droplet and the surface it is sitting on we are able to adjust the wetting angle of the drop. Since Lippmann's findings, electrocapillary phenomena – or electrowetting – have developed into a series of tools for manipulating microdroplets on solid surfaces, or small amounts of liquids in capillaries for microfluidic applications. In this article, we briefly review some recent progress of fundamental understanding of electrowetting and address some still unsolved issues. Specifically, we focus on static and dynamic electrowetting. In static electrowetting, we discuss some basic phenomena found in DC and AC electrowetting, and some theories about the origin of contact angle saturation. In dynamic electrowetting, we introduce some studies about this rather recent area. At last, we address some other capillary phenomena governed by electrostatics and we give an outlook that might stimulate further investigations on electrowetting.     

Design and performance of a composite Tm:YAG laser pumped by VBG-stabilized narrow-band laser diode

A 2-μm composite Tm:YAG laser pumped with a narrow-band laser diode was presented. The temperature distribution and thermal lens in the Tm:YAG were numerically simulated by a finite element method and the results were used to design the special cavity, in order to achieve a high efficiency and stable output. With a 25-W incident pump power, we obtained a maximum output power of 11 W at 2018.5 nm, corresponding to a slope efficiency of 51.3% and an optical-to-optical efficiency of 44.5%, respectively. The beam quality was measured to be M_x~2= 1.8 and M_y~2= 1.6.     

微流蒸发光散射检测器与加压毛细管电色谱联用测定川贝枇杷糖浆中6种有效成分的含量

建立了同时测定川贝枇杷糖浆中6种有效成分(桔梗皂苷D、贝母辛、齐墩果酸、西贝素、贝母甲素和贝母乙素)含量的微流蒸发光散射检测器(μELSD)与加压毛细管电色谱(p CEC)联用检测方法。搭建p CEC-μELSD联用平台,采用C18毛细管色谱柱(EP-150-15-3-C18),流动相为乙腈(A)-10 mmol·L-1甲酸-三乙胺水溶液(p H 11.0)(B),梯度洗脱,柱流速为1.02μL·min-1,施加电压为+10 k V,雾化载气流速为0.4 L·min-1,蒸发温度为40℃。川贝枇杷糖浆中6种有效成分可在10 min内得到分离检测,6种有效成分的线性范围可达4个数量级,检出限均在pg水平,加标回收率为97.9%~103.0%。所建立的p CEC-μELSD联用方法精密度、重复性和稳定性良好,且简便、快速、可靠,可用于川贝枇杷糖浆中6种有效成分的含量测定。     

微束X射线荧光光谱仪测定射击残留物特征元素分布图的应用研究

通过优化定距射击样本采集条件,考察了六四手枪在不同距离(0,2,5,10,15,20,25,30,35,40,45,50,60,80,100,120,140,170,200,300,500,1 000 cm)垂直射击PU布块靶体时相关元素(氯、钾、硫、锑、锡、钡、铅、汞、砷、铁、铜、锌、钛、钙、铑)的区域扫描图,建立了微束X射线荧光光谱(μ-XRF)面扫描技术分析射击样本的方法,并建立了六四手枪射击残留物特征元素分布图形随射击距离而变化的数据模型,同时对所得数据进行了归一化处理。本方法可协助推断射击距离,为涉枪案件的侦查与诉讼提供科学证据。     

Structural variation of solid core and thickness of porous shell of 1.7 μm core-shell silica particles on chromatographic performance: narrow bore columns

Chromatographic and mass transfer kinetic properties of three narrow bore columns (2.1 × 50 mm) packed with new core–shell 1.7 μm EIROSHELL™-C₁₈ (EiS-C₁₈) particles have been studied. The particles in each column varied in the solid-core to shell particle size ratio (ρ), of 0.59, 0.71 and 0.82, with a porous silica shell thickness of 350, 250 and 150 nm respectively. Scanning and transmission electron microscopy (SEM and TEM), Coulter counter analysis, gas pycnometry, nitrogen sorption analysis and inverse size exclusion chromatography (ISEC) elucidated the physical properties of these materials. The porosity measurement of the packed HILIC and C₁₈ modified phases provided the means to estimate the phase ratios of the three different shell columns (EiS-150-C₁₈, EiS-250-C₁₈ and EiS-350-C₁₈). The dependence of the chromatographic performance to the volume fraction of the porous shell was observed for all three columns. The naphtho[2,3-a]pyrene retention factor of k′ ∼ 10 on the three EiS-C_18s employed to obtain the height equivalents to theoretical plates (HETPs) data were achieved by varying the mobile phase compositions and applying the Wilke and Chang relationship to obtain a parallel reduced linear velocity. The Knox fit model gave the coefficient of the reduce HETPs for the three EiS-C_18s. The reduced plate height minimum h_min = 1.9 was achieved for the EiS-150-C₁₈ column, and generated an efficiency of over 350,000 N/m and h_min = 2.5 equivalent to an efficiency of 200,000 N/m for the EiS-350-C₁₈ column. The efficiency loss of the EiS-C18 column emanating from the system extra-column volume was discussed with respect to the porous shell thickness.     

An antiferromagnetically coupled hexanuclear copper(II) Schiff base complex containing phenoxo and dicyanamido bridges: Structural aspects and magnetic properties

A novel hexanuclear complex [{(CuL)₂Cu}₂(μ-dca)₂](ClO₄)₂·2L′(1) (where H₂L = (OH)C₆H₄C(CH₃)N(CH₂)₃NC(CH₃)C₆H₄(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)₂⁻ and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV-Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ₂-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)₂Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ_1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)₂Cu}₂(μ-dca)₂]²⁺. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm⁻¹) between the copper(II) centers.     

Synthesis,crystal structure and antibacterial activity of a new binuclear copper(II) complex with N,N ′- bis ( N -hydroxyethylaminopropyl)oxamido as a bridging ligand

A new μ-oxamido-bridged dicopper(II) complex, [Cu₂(heap)](ClO₄)₂?·?2H₂O [H₂heap?=?N,N′-bis(N- hydroxyethylaminopropyl)oxamido], has been synthesized and structurally characterized by elemental analyses, molar conductance, IR and single-crystal X-ray diffraction. The single crystal X-ray analysis reveals that the asymmetric unit of the complex is composed of half a binuclear cation [Cu₂(heap)]²⁺, one perchlorate anion, and one lattice water molecule. Each copper(II) atom is tetracoordinate in a distorted square-planar geometry and the bridging ligand (H₂heap) adopts the trans conformation with an inversion centre at the middle of the C2–C2ⁱ bond. The structure cohesion is ensured by hydrogen bonding interactions, which form a two-dimensional supramolecular framework. The antibacterial assay indicates that the complex showed better activity than the ligand.     

A Computer Program for Identifying Anomalous Peaks in Automated Amino Acid Analyses

Abstract

In automated ion-exchange chromatography of amino acids utilizing spectrophotometric measurement., the ratio of the areas under the 40 mμ; and 570 mμ; absorption peak tracings has been shown to be specific for each amino acid. Symmetrical, but impure peaks have ratios deviating from these norms. A simple computer program for the rapid identification of these anomalous peaks has been designed. It is proposed as an addendum to any computer program now in use with amino-acid analyzers.