Molecular recognition properties of salicylic acid-imprinted polymers

Summary Two molecularly imprinted polymers (MIP) have been prepared using the acidic drug salicylic acid, which can form intramolecular hydrogen bond, as the template and acrylamide or 4-vinylpyridine as the functional monomer. HPLC was used to evaluate the binding performance of the MIP for the template and for several analogues. The results showed that the MIP (P₂) prepared using acrylamide as the functional monomer had no molecular imprinting effect whereas that (P₁) prepared using 4-vinylpyridine as the functional monomer had a significant molecular imprinting effect. The reason the molecular imprinting effect was different for the two MIP was elucidated and the molecular recognition properties of P₁ were studied in detail. It was confirmed that electrostatic interaction played an important role in the molecular recognition of P₁. Scatchard analysis showed that two types of binding site with distinctly different affinity were formed in P₁. Their dissociation constants were estimated to be 7.6×10⁻⁵ mol L⁻¹ and 3.2×10⁻³ mol L⁻¹, respectively. Because P₁ has high affinity and selectivity for salicylic acid not only in organic systems but also in water-containing systems, it gives P₁ the potential for use in the enrichment, separation, and detection of salicylic acid in biological fluids.     

Pitzer model parameters for sparingly soluble salts from solubility measurements. The systems TlCl+SrCl2+H2O and TlCl+BaCl2+H2O at 25°C

The solubility of thallium(I) chloride has been determined in aqueous solutions of strontium chloride and barium chloride at concentrations up to 1.5 mol kg^–1. The data were analyzed using Pitzer's equations without making explicit assumption of association to ion pairs by assuming =3 instead of =2, with the ⁽¹⁾ term for TlCl being equivalent to the ⁽²⁾ term for 2-2 electrolytes. Best values of ⁽⁰⁾ and ⁽¹⁾ for TlCl are recommended together with K _s , the activity solubility product. These were used to fit the present solubility data and derive the Pitzer model mixture parameters relevant to the systems, _fTIN and _fTINCl (N=Sr, Ba). Mixture parameters for TlCl+MCl+H₂O systems are also derived to complete the parameter base. The fit of the experimental data was found to be worse when higher-order terms for asymmetrical mixing were included in the analysis. Activity coefficients for thallium(I) chloride in the mixtures are derived.     

Photomechanical Actuation of Ligand Geometry in Enantioselective Catalysis

A catalyst that couples a photoswitch to the biaryl backbone of a chiral bis(phosphine) ligand, thus allowing photochemical manipulation of ligand geometry without perturbing the electronic structure is reported. The changes in catalyst activity and selectivity upon switching can be attributed to intramolecular mechanical forces, thus laying the foundation for a new class of catalysts whose selectivity can be varied smoothly and in situ over a useful range by controlling molecular stress experienced by the catalyst during turnover. Forces on the order of 100 pN are generated, thus leading to measurable changes in the enantioselectivities of asymmetric Heck arylations and Trost allylic alkylations. The differential coupling between applied force and competing stereochemical pathways is quantified and found to be more efficient for the Heck arylations.     

非PLL相位平均型参考线原型验证

射频相位参考线是粒子加速器的重要组成部分之一,为射频低电平控制系统(LLRF)、束流诊断系统、定时系统等提供稳定的相位锁定参考信号。为减少远距离传输过程中由环境温度变化导致的射频传输线中的射频相位漂移,多个加速器装置中已经采用射频相位参考线提供射频相位参考,这些相位参考的实现方案主要是基于恒温控制和基于光纤锁相。与这些方案相比,采用相位平均方法不仅可以保持长距离节点之间的相位稳定,而且更易于现场安装与维护。现有的带有锁相环(PLL)的终端短路方式实现相位平均参考线的方案仍有一些节点数量限制等方面的不足,本文对相位平均参考线结构进行了去除PLL的简化设计并进行了验证,以期增加更多的相位分配节点以及降低对射频器件参数的要求。对非PLL的单端输入终端短路相位平均方案与两端输入各节点间互为参考的相位平均方案分别进行了实验测试,结果表明两者的相位RMS精度可以达到0.1°~0.3°。并对不同的相位平均实现方案中相位不稳定的产生原因进行了分析,结果表明,除环境温度外,同轴线缆材质、合成相位与幅度的不平衡合成等也是重要影响因素。     

Capillary Coated with Layer-by-Layer Assembly of γ-Zirconium Phosphate/ Lysozyme Nanocomposite Film for Open Tubular Capillary Electrochromatography Chiral Separation

A new capillary coating of alternate -zirconium phosphate lysozyme fabricated for open-tubular electrochromatography enantioseparation. The chiral compounds D, L-tryptophan tested were enantiomerically resolved. The influences brought by experimental parameters, such as organic modifier, temperature, applied voltage and pH of running buffer on the performance of the column, were investigated.     

Electrical and electrochemical characteristics of La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>CoO<Subscript>3-δ</Subscript> cathode materials synthesized by a modified citrate-EDTA sol-gel method assisted with activated carbon for proton-conducting solid oxide fuel cell application

The electrical conductivity and electrochemical performance of a La_0.6Sr_0.4CoO_3-δ (LSC) cathode produced by a modified citrate-EDTA sol-gel method assisted with activated carbon are characterized for a proton-conducting solid oxide fuel cell (H⁺??SOFC) application at intermediate temperature. Thermogravimetric analysis revealed that the decomposition of the unrequired intermediate compounds in the precalcined powder was completed at 800?°C. A single LSC perovskite phase was formed at a calcination temperature of 900?°C, as confirmed by X-ray diffraction analysis. The particle size, crystallite size, and BET-specific surface area of the powder are 219–221?nm, 18?nm, and 9.87?m²?g^?1, respectively. The high index value of the extent of agglomeration (5.53) showed that the powder was barely agglomerated. Bulk LSC sintered at 1200?°C for 2?h showed the highest direct-current electrical conductivity (σ_d.c) compared to that of bulk LSC sintered at 1000?°C and 1100?°C. The value of σ_d.c was affected by the density and porosity of the sintered samples. The area specific resistance (ASR) of screen-printed LSC working on a proton conductor of BaCe_0.54Zr_0.36Y_0.1O_2.95 (BCZY) decreased from 5.0?Ω?cm²–0.06?Ω?cm² as the temperature increased from 500?°C to 800?°C with an activation energy of 1.079?eV. Overall, in this work, the LSC material produced with the aid of activated carbon meet the requirements for the application as a cathode in an intermediate temperature H⁺-SOFC.

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Thermodynamics of electrolyte solutions. The system HCl + CaCl2 + H2O at 298.15°K

Activity coefficients of hydrochloric acid have been determined from electromotive-force measurements of cells containing mixtures of hydrochloric acid and calcium chloride at constant total ionic strengthsI=0.1, 0.5, 1.0, 2.0, and 3.0 mole-kg^–1 at 298.15°K. Interpretations based on Scatchard's and Pitzer's equations indicate that Pitzer's equations probably provide a more convenient guide to the thermodynamic properties of the mixed-electrolyte solutions. Activity coefficients for calcium chloride were derived from these equations.     

加筋板材料辨识的导纳特征表达与冲击声特征提取

以表征物理属性的导纳特征为中间量,提取与加筋板材料属性有关的冲击声特征。先用相关分析方法获得金属加筋板物理属性的导纳特征表达以及导纳特征与冲击声特征之间的联系,间接得到表征声源物理属性的冲击声特征,然后通过支持向量机分类器验证不同特征在金属加筋板材料分类辨识中的性能。结果表明,所得的4组冲击声特征能准确识别出不同的材料,单个特征的识别率与对应材料属性的可分程度有关,理想冲击声声特征比音色特征的平均识别率更高。由此可见,利用导纳特征提取与材料属性相关冲击声特征的方法是有效的,且所提的特征能够很好的反映声源材料属性。