Cyclic water clusters in tape-like and cage-like structures

Controlling the ratio of 2,2'-bpy to benzene-1,3,5-tricarboxylic acid produces two interesting complexes, namely [Co(2,2'-bpy)?]?(SO?)?8.5H?O (1) and [Cu?(BTCA) (2,2'-bpy)?] (OH)?(2,2'-bpy)?.??14H?O (2) (H?BTCA = benzene-1,3,5-tricarboxylic acid, 2,2'-bpy = 2,2'-bipyridine). We report the structural evidence in the solid state of discrete lamellar water cluster conformations. These units are found to act as supramolecular glue in the aggregation of cobalt (II) or copper (II) complexes to give three dimensional cage-like networks through hydrogen-bonding. It is interesting that the structure of complex 1 contains a 3D negatively charged cage.     

Surface design for controlled crystallization: the role of surface chemistry and nanoscale pores in heterogeneous nucleation

Current industrial practice for control of primary nucleation (nucleation from a system without pre-existing crystalline matter) during crystallization from solution involves control of supersaturation generation, impurity levels, and solvent composition. Nucleation behavior remains largely unpredictable, however, due to the presence of container surfaces, dust, dirt, and other impurities that can provide heterogeneous nucleation sites, thus making the control and scale-up of processes that depend on primary nucleation difficult. To develop a basis for the rational design of surfaces to control nucleation during crystallization from solution, we studied the role of surface chemistry and morphology of various polymeric substrates on heterogeneous nucleation using aspirin as a model compound. Nucleation induction time statistics were utilized to investigate and quantify systematically the effectiveness of polymer substrates in inducing nucleation. The nucleation induction time study revealed that poly(4-acryloylmorpholine) and poly(2-carboxyethyl acrylate), each cross-linked by divinylbenzene, significantly lowered the nucleation induction time of aspirin while the other polymers were essentially inactive. In addition, we found the presence of nanoscopic pores on certain polymer surfaces led to order-of-magnitude faster aspirin nucleation rates when compared with surfaces without pores. We studied the preferred orientation of aspirin crystals on polymer films and found the nucleation-active polymer surfaces preferentially nucleated the polar facets of aspirin, guided by hydrogen bonds. A model based on interfacial free energies was also developed which predicted the same trend of polymer surface nucleation activities as indicated by the nucleation induction times.     

毛细管离子色谱分析系统研究进展

离子色谱是目前分析离子型样品的成熟技术,其水相工作介质的特点相对于液相色谱更适合于生物样品的分析。毛细管离子色谱(CIC)由于其节省样品的特点在生物分析方面的优势更为明显。CIC大体上可分为开管型、填充柱型和整体柱型3种类型。本文以填充型CIC几大关键部件技术发展为主线,综述了近年来CIC的研究进展。     

A separation mechanism of photogenerated charges and magnetic properties for BiFeO3 microspheres synthesized by a facile hydrothermal method

BiFeO(3) (BFO) microspheres were synthesized by a facile hydrothermal method. The optical absorption spectrum indicates that on site Fe(3+) crystal-field transitions and the charge transfer excitations can be observed. Magnetic measurements show a spin-glass behavior and room temperature weak ferromagnetism. The surface photovoltage spectroscopy of the BFO shows two response peaks centered at about 370 and 400 nm, respectively. Under an ambient atmosphere, the maximum surface photovoltage of the BFO reaches 180 μV with the bias (+2 V) and is three times larger than that with zero bias. It is found that the surface photovoltage response intensity increases with an increase in applied bias, regardless of positive or negative bias. It is suggested that the surface photovoltaic properties are related to both the depolarization field owing to ferroelectric polarization and the build-in electric field due to the Schottky barrier. The micro-process and the physical mechanism of the separation of photogenerated charges for BFO are fully explained.     

Selective light-triggered chemiluminescence between fluorescent dyes and luminol, and its analytical application

We report herein a novel chemiluminescence (CL) phenomenon triggered by light irradiation when a fluorescent dye, for example hematoporphyrin, fluorescein, eosin, or methylene blue is present in the luminol solution. A possible mechanism is proposed for the photoinduced chemiluminescence (PICL) reaction. Compared with reported methods for CL triggering, for example flow-injection, static reagent injection, and the electrochemical technique, the proposed in-situ PICL method presented has three advantages. First, the method is more selective, because the PICL signal of the target fluorescent dyes is initiated by excitation at a selective wavelength only. Second, the space and time resolution of the PICL method are better. Last, and most important, compared with injecting a reagent or inserting a electrode into the CL system to initiate the CL reaction, with the in-situ PICL method there is no physical interference with the target detecting system. All these advantages of the PICL method indicate it has many potential applications in the analytical sciences. The proposed method was applied to analysis of urine containing adrenaline. The linear range for adrenaline is 2.0?×?10^?10–1.0?×?10^?7 g mL^?1 and the detection limit is 6.0?×?10^?11 g mL^?1.

Effect of LiBOB as additive on electrochemical properties of lithium–sulfur batteries

The effect of varying amounts (in the range 1–10 wt.%) of LiBOB (lithium bis(oxalato) borate) as additive in mixed liquid electrolyte on the electrochemical performance of lithium–sulfur batteries is investigated at room temperature. The electrochemical impedance spectroscopy (EIS) of lithium anode with LiBOB has two semicircles, corresponding to charge transfer impedance and ion migration impedance, respectively. The lithium anode with LiBOB shows a higher ion migration impedance, which could reduce the ionic diffusion rate in the anode. Scanning electron microscopy (SEM) observations shows that lithium anode with LiBOB has a smoother and denser surface morphology than the anode without LiBOB. The lithium–sulfur batteries with LiBOB shows the improvement of both the discharge capacity and cycle performance, a maximum discharge capacity of 1,191 mA h g⁻¹ is obtained with 4 wt.% LiBOB. The lithium–sulfur batteries with 4 wt.% LiBOB can maintain a reversible capacity of 756 mA h g⁻¹ after 50 cycles.     

基于高光谱的膜下滴灌小麦氮素营养评价研究

通过小麦氮素和品种对比试验,分析不同氮素和品种处理小麦生育期氮肥偏生产力与光谱参数的相关关系,建立小麦氮肥偏生产力的光谱参数估算模型,结果表明绿度植被指数(GREENNDVI)在拔节期与小麦氮肥偏生产力呈极显著相关,相关系数0.640 4。用GREENNDVI在拔节期建立小麦氮肥偏生产力的估算模型,均方根误差0.459 7。研究表明利用光谱参数可以有效地估算小麦氮肥偏生产力。     

Mixed,componentwise condition numbers and small sample statistical condition estimation of Sylvester equations

We present a componentwise perturbation analysis for the continuous‐time Sylvester equations. Componentwise, mixed condition numbers and new perturbation bounds are derived for the matrix equations. The small sample statistical method can also be applied for the condition estimation. These condition numbers and perturbation bounds are tested on numerical examples and compared with the normwise condition number. The numerical examples illustrate that the mixed condition number gives sharper bounds than the normwise one. Copyright © 2011 John Wiley & Sons, Ltd.     

Specificity and affinity of phenosafranine protein adduct: Insights from biophysical aspects

Phenosafranine is a toxic and recalcitrant compound, whose capacity to intercalate with double stranded DNA has been shown. In this contribution, a biophysical discuss on the conjugation of phenosafranine with two model proteins human serum albumin (HSA) and lysozyme (Lys) has been identified utilizing a combination of molecular modeling, steady state and time-resolved fluorescence and circular dichroism (CD) approaches. The accurate binding domain of phenosafranine in protein has been characterized from molecular modeling, subdomain IIIA of HSA and Trp-62, Trp-63 and Trp-108 residues of Lys was designated to possess high-affinity for this compound, the dominant forces in the protein–phenosafranine adduct are hydrogen bonds and π–π interactions, but hydrophobic interactions between dye and Lys are also not exclude. The data of fluorescence displayed that the complex of phenosafranine with protein produces quenching through static property, this corroborates the time-resolved fluorescence results that the ground state complex formation with a moderate affinity of 10⁴ M^?1. Moreover, via synchronous fluorescence, CD and three-dimensional fluorescence we indicated some extent of polypeptide chain of protein partially unfolding upon conjugation with phenosafranine. Through this work, we anticipate it can supply salient clues on the toxicological action of phenosafranine and other azines, which have analogous configuration with phenosafranine.     

气隙式热开关传热特性研究

本文介绍了一种新型低温热开关的工作原理.考虑到热开关充人的气体在连续介质区和自由分子状态的传热以及肋片沿轴向的导热对热开关的传热特性进行了详细的理论分析.建立了该种热开关传热的理论模型.给出了肋片的厚度、长度、气隙宽度、外壳壁厚与导通热导之间的关系曲线以及气体压强、外壳厚度与关断热导之间的关系曲线.