Synthesis,spectroscopic and thermal investigation of Schiff-base complexes of Cu(II) derived from heterocyclic β-diketone with various primary amines

The mononuclear complex [Cu(PMFP)(bipy)]ClO₄ was prepared by reaction of Cu(NO₃)₂·5H₂O with ligand PMFP and 2,2′-bipyridine. The corresponding Schiff bases were prepared by condensation of [Cu(PMFP)(bipy)]ClO₄ with ethylenediamine, ethanolamine and glycine with general formula [Cu(PMFP-SB)(bipy)]ClO₄ (where PMFP?=?1-phenyl-3-methyl-4-formyl-2-pyrazolin-5one; bipy?=?2,2′-bipyridine). All the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and ¹H-NMR, FT-IR, ESR, electronic spectra and mass spectrometry. Electronic spectra and magnetic susceptibility measurements indicate square planar stereochemistry. Thermal stability, order of kinetics, heat capacity and activation energy of thermal degradation for these complexes were determined by TGA and DSC. Hamiltonian and bonding parameters from ESR spectra indicate the metal ligand bonding is partially covalent.     

Structure-dependent photophysics studied in single molecules of polythiophene derivatives.

We report on the photophysical characterization at the single-molecule level of a graft copolymer consisting of a polythiophene backbone and long polystyrene branches. The presence of the branches prevents the polymer chain from forming a collapsed conformational state. The photophysical properties of the resulting solution-like conformation are studied by measuring single-molecule photobleaching dynamics, emission polarization anisotropy and emission spectra. The results are compared with those obtained on the same polythiophene derivative without the branches. It is found that the presence of the branches is a decisive factor in determining the photophysical properties of the polymers on the single-molecule level.     

Evaluation of alternatives to warfarin as probes for Sudlow site I of human serum albumin: characterization by high-performance affinity chromatography

Warfarin is often used as a site-specific probe for examining the binding of drugs and other solutes to Sudlow site I of human serum albumin (HSA). However, warfarin has strong binding to HSA and the two chiral forms of warfarin have slightly different binding affinities for this protein. Warfarin also undergoes a slow change in structure when present in common buffers used for binding studies. This report examined the use of four related, achiral compounds (i.e., coumarin, 7-hydroxycoumarin, 7-hydroxy-4-methylcoumarin, and 4-hydroxycoumarin) as possible alternative probes for Sudlow site I in drug binding studies. High-performance affinity chromatography and immobilized HSA columns were used to compare and evaluate the binding properties of these probe candidates. Binding for each of the tested probe candidates to HSA was found to give a good fit to a two-site model. The first group of sites had moderate-to-high affinities for the probe candidates with association equilibrium constants that ranged from 6.4 x 10(3)M(-1) (coumarin) to 5.5 x 10(4)M(-1) (4-hydroxycoumarin) at pH 7.4 and 37 degrees C. The second group of weaker, and probably non-specific, binding regions, had association equilibrium constants that ranged from 3.8 x 10(1)M(-1) (7-hydroxy-4-methylcoumarin) to 7.3 x 10(2)M(-1) (coumarin). Competition experiments based on zonal elution indicated that all of these probe candidates competed with warfarin at their high affinity regions. Warfarin also showed competition with coumarin, 7-hydroxycoumarin and 7-hydroxy-4-methycoumarin for their weak affinity sites but appeared to not bind and/or compete for all of the weak sites of 4-hydroxycoumarin. It was found from this group that 4-hydroxycoumarin was the best alternative to warfarin for examining the interactions of drugs at Sudlow site I on HSA. These results also provided information on how the major structural components of warfarin contribute to the binding of this drug at Sudlow site I.     

Design,synthesis and evaluation of PPAR gamma binding activity of 2-thioxo-4-thiazolidinone derivatives

We designed and synthesized a series of 2-thioxo-4-thiazolidinone derivatives and evaluated them on peroxisome proliferator activated receptor γ(PPARγ) binding activities.Through the biological assays,compounds 18 and 38 were highlighted with K_i values of 12.15 nmol/Land 14.46 nmol/L,respectively.Then structure-activity relationship(SAR) was analyzed to screen privileged structural modifications.Moreover,molecular fitting of these compounds onto the approved drug Rosightazone in the PPARγligand binding domain was performed to elucidate the SAR and explore potential receptor-ligand interactions.These results demonstrate that the 2-thioxo-4-thiazolidinones can be considered as new promising molecular probes with excellent binding activities to PPARγ.     

Length‐Scale‐Dependent Phase Transformation of LiFePO4: An In situ and Operando Study Using Micro‐Raman Spectroscopy and XRD

The charge and discharge of lithium ion batteries are often accompanied by electrochemically driven phase‐transformation processes. In this work, two in situ and operando methods, that is, micro‐Raman spectroscopy and X‐ray diffraction (XRD), have been combined to study the phase‐transformation process in LiFePO₄ at two distinct length scales, namely, particle‐level scale (～1 μm) and macroscopic scale (～several cm). In situ Raman studies revealed a discrete mode of phase transformation at the particle level. Besides, the preferred electrochemical transport network, particularly the carbon content, was found to govern the sequence of phase transformation among particles. In contrast, at the macroscopic level, studies conducted at four different discharge rates showed a continuous but delayed phase transformation. These findings uncovered the intricate phase transformation in LiFePO₄ and potentially offer valuable insights into optimizing the length‐scale‐dependent properties of battery materials.     

Dynamics of a nearly symmetrical piecewise linear oscillator close to grazing incidence: Modelling and experimental verification

Experimental studies and mathematical modelling have been carried out for a nearly symmetrical piecewise linear oscillator to examine the bifurcation scenarios close to grazing. Higher period responses are found after grazing, although the period adding windows predicted as a generic feature of one-sided impacting systems are not observed. It appears that the presence of the second high stiffness spring stabilises additional periodic orbits. The global solution for a piecewise smooth model is developed by stitching locally valid maps. For the symmetrical case the highest period of response is three, if asymmetry in the gap and/or stiffness is introduced then higher periodic orbits are observed. Only small asymmetries are required to achieve a good correspondence with experiments. Further examination shows that many attractors are not stable to even small changes in the symmetry of the system.     

三峡库区典型塌岸模式研究

三峡库区塌岸地质条件调查结果表明,不同的岸坡结构,蓄水后库岸的变形破坏形式—塌岸模式,往往差别较大。本文根据现场调查成果,结合室内分析,总结归纳出三峡库区几种典型的塌岸模式,即冲蚀磨蚀型、坍塌型、崩塌(落)型、、滑移型和流土型。在此基础上,对不同塌岸模式的发展演进过程、发育分布特征,以及塌岸与岸坡岩土结构、地形地貌等的关系进行了深入系统地研究,提出了三峡库区典型塌岸发育的一般地质条件。     

隧道围岩强度不均地段塌方成因及其处理方法

采用微面模型理论和损伤力学方法,建立了节理岩体的弹塑性损伤耦合微面模型. 在节理岩体的微 面上,将岩体视为由节理面与岩石组成的二元介质,以节理连通率作为岩体沿该方向的面积 损伤变量,考虑微面法向拉应力和压应力下的不同塑性变形和损伤耦合作用机制,基于塑性 理论建立了节理岩体的微面塑性损伤增量本构关系. 采用微面物理量与宏观物理量的几何约 束模型,根据微面方向积分导出了节理岩体的宏观弹塑性增量本构关系. 编制了节理岩体微 面模型的MARC有限元子程序,对节理岩体的单轴拉伸、压缩试验和泥浆压力作用下的井壁稳 定问题进行了数值模拟研究. 数值计算结果表明,该模型能很好地揭示载荷作用下节理岩体 的各向异性非弹性变形和次生节理演化过程.     

针对磁通蠕动效应的超导悬浮动力运动比较研究

针对超导-永磁悬浮系统,分别采用描述超导宏观电磁场本构关系的磁通流动模型和磁通流动与蠕动模型,定量模拟了自由悬浮于超导体上方永磁体的振动。通过比较研究说明磁通蠕动效应对超导悬浮动力运动的影响程度以及这一影响随超导临界电流密度、系统外加激励振幅和频率的变化规律。