Binary Lead Fluoride Pb3F8

The binary lead fluoride Pb₃F₈ was synthesized by the reaction of anhydrous HF with Pb₃O₄ or by the reaction of BrF₃ with PbF₂. The compound was characterized by single-crystal and powder X-ray diffraction, IR, Raman, and solid-state MAS ¹⁹F NMR spectroscopy, as well as thermogravimetric analysis, XP and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Solid-state quantum-chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound.     

Investigation of the noncovalent interactions between anti-amyloid agents and amyloid β peptides by ESI-MS

This paper describes an efficient and reproducible screening method for identifying low molecular weight compounds that bind to amyloid β peptides (Aβ) peptides using electrospray ionization mass spectrometry (ESI-MS). Low molecular weight compounds capable of interacting with soluble Aβ may be able to modulate/inhibit the Aβ aggregation process and serve as potential disease-modifying agents for AD. The present approach was used to rank the binding affinity of a library of compounds to Aβ1-40 peptide. The results obtained show that low molecular weight compounds bind similarly to Aβ1-42, Aβ1-40, as well as Aβ1-28 peptides and they underline the critical role of Aβ peptide charge motif in binding at physiological pH. Finally, some elements of structure-activity relationship (SAR) involved in the binding affinity of homotaurine to soluble Aβ peptides are discussed.     

Synthesis and characterization of novel pyridyl/naphthyl/(diphenyl)methylseleno substituted alkanoic acids: X-ray structure of 2-pyridylselenoethanoic acid, 2-naphthylselenoethanoic acid and 2-(diphenyl)methylselenoethanoic acid

A number of novel and synthetically important pyridyl/naphthyl/(diphenyl)methylseleno substituted alkanoic acids (20-25) have been synthesized using an efficient and operationally simple strategy. Starting substrates, ethyl pyridyl/naphthyl/(diphenyl)methylseleno substituted alkanoates (8-13) were easily prepared by treatment of ethyl chloroalkanoates 7(a-c) with nucleophilic selenium reagent RSeNa⁺, generated from the cleavage of dipyridyl/dinaphthyl/bis(diphenylmethyl) diselenide (1-6) with sodium borohydride in ethanol. The ethyl pyridyl/naphthyl/(diphenyl)methylseleno substituted alkanoates (8-13) on basic hydrolysis and subsequent acidification afford pyridyl/naphthyl/(diphenyl) methylseleno substituted alkanoic acids (20-25) in excellent yields. These selenoalkanoates (8-13) and selenoalkanoic acids (20-25) have been characterized by elemental analysis and various spectroscopic techniques viz. NMR (¹H, ¹³C and ⁷⁷Se), IR and mass spectrometry. The molecular structure of 2-pyridylselenoethanoic acid (20a), 2-naphthylselenoethanoic acid (23a) and 2-(diphenyl)methylselenoethanoic acid (24a) has also been established with the help of single crystal X-ray analysis.     

多介质流体界面的守恒型跟踪法

本文中,我们对茅德康在【D.K.Mao,Towards front-tracking based on conservation in two space dimensionsⅡ,tracking discontinuities in capturing fashion,J.Comput.Phys.,226,(2007),pp 1550-1588】一文中所建立的守恒型跟踪法进行了改进,成功将算法运用到多介质流体界面的计算中.最后,我们使用改进后的算法计算了两个数值算例,验证了算法的有效性.     

Chemically and Electrochemically Triggered Assembly of Viologen Radicals: Towards Multiaddressable Molecular Switches

We have established that bipyridinium radicals can be reversibly π‐dimerized under the combined effects of chemical (proton transfer) and electrochemical (electron transfer) stimuli. Our investigations also led to the discovery that a bis‐pyridinyl appended calixarene intermediate is involved in a fully reversible redox‐triggered σ‐dimerization process. The structure of the most stable intramolecular σ‐dimer was provided by computational chemistry and its complete conversion into a noncovalent π‐dimer could be triggered chemically by addition of protons, leading to the formation of protonated cation radicals. Theoretical data collected with the N‐methylated and N‐protonated π‐dimers also support the existence of multivariant orientations in π‐bonded dimers of viologen cation‐radicals.     

Simultaneous CO concentration and temperature measurements using tunable diode laser absorption spectroscopy near 2.3 μm

Simultaneous measurements of carbon monoxide (CO) mole fraction and temperature using tunable diode laser absorption spectroscopy (TDLAS) near 2.3 μm are reported. The measurement method uses ro-vibrational transitions [R(27): v″ = 1 → v′ = 3] and [R(6): v″ = 0 → v′ = 2] in the first overtone band of CO near 2.3 μm (~4,278 cm^?1). The measurements were performed in the post flame environment of fuel rich premixed ethylene–air flames with a N₂ co-flow, stabilized over a water cooled McKenna burner. Non-uniformity in the temperature and CO mole fraction, along the absorption line of sight, in the mixing layer of the co-flow, was considered during data analysis. The TDLAS based temperature measurements (±80 K) were in good agreement with those obtained using N₂ vibrational coherent anti-Stokes Raman scattering (±20 K), and the CO mole fraction measurements were in good agreement with the equilibrium values, for equivalence ratios lower than 1.8. A signal to noise ratio of 45 was achieved at an equivalence ratio of 1 for a CO concentration of 0.8 % at 1,854 K.     

Comprehensive study towards the desulfonylation/desulfinylation of cis-3-functionalized 3-phenylsulfonyl/sulfinyl-β-lactams to access novel cis-3-monosubstituted-β-lactams

An inclusive study towards the stereospecific synthesis of novel cis-3-monosubstituted-β-lactams from cis-3-functionalized 3-phenylsulfonyl/sulfinyl-β-lactams is described. 3-Sulfinyl-β-lactams 5/5? successfully furnished stereospecific cis-3-monosubstituted-β-lactams 6, however 3-sulfonyl-β-lactams 2 failed to give the desulfurized product 6?. The final stereochemical and structural conformations of novel β-lactams were established by single crystal X-ray crystallographic study (5c). The cis configuration of the β-lactams 5/5? and 6 was assigned in relevance to E and C4-H and C3-H and C4-H respectively.     

Enantiomeric pairs of copper(II) polypyridyl-alanine complex salts: anticancer studies

The anticancer properties of two previously characterized pairs of optically pure chiral complex salts [Cu(phen)(ala)(H₂O)]X·xH₂O (phen?=?1.10-phenanthroline; X?=?NO₃^?; ala: l-alanine (l-ala) 1 and d-alanine (d-ala) 2; and (X?=?Cl^?; ala: l-ala, 3 and d-ala, 4; x?=?number of lattice water molecules) are reported herein, together with the crystal structure of the d-enantiomer 4. Unlike cisplatin which is ineffective against MCF-7 cancer cells with the absence of caspase-3 protein expression, these two pairs of complex salts were effective against this cell line and they were able to induce an increase in intracellular ROS, loss in mitochondrial membrane potential, cell cycle arrest mainly at SubG1 phase , caspase-9 activation, and caspase-3/caspase-7-independent apoptosis. Screening of 1 on the NCI-60 panel of human cancer cell lines showed that it was effective against most of the cell lines. MTT-NCI modified assay screening was also done on other cancer cell lines, viz. A549, CNE1, and HepG2, and two normal cell lines, viz. MCF-10A and CHANG. The effects of chirality of these Cu(II) compounds, especially the greater selectivity of d-enantiomers over the l-counterparts, on their anticancer properties are also reported herein.     

NUMERICAL ANALYSIS ON THE VELOCITY AND PRESSURE FIELDS INDUCED BYMULTI-OSCILLATIONS OF AN UNDERWATER EXPLOSION BUBBLE

假设水下爆炸气泡的内部气体在膨胀收缩过程中满足绝热条件,周围流体无黏无旋不可压缩. 基于势流理论,采用边界元法研究气泡动力学行为,重点关注气泡引起的流场脉动载荷以及滞后流特性,给出了相关的理论推导和数值计算方法. 通过将数值结果与解析解、实验值进行对比,数值模型的收敛性和有效性能够得到保证. 利用编写的程序进行计算和分析,发现在气泡加速膨胀阶段,流场压力在气泡径向不一定是逐渐衰减,还有可能以先增后减的规律变化;气泡射流后,为了能够继续描述环状气泡的运动以及流场特性,将此时的流场分为无旋场和一个布置在气泡内部涡环的叠加,计算过程中采用了一些数值技巧处理气泡的拓扑结构,得以连续模拟多个周期的气泡运动. 环状气泡具有相对较高的上浮迁移速度,而且在其顶部和底部附近分别形成两个高压区,顶部的高压区峰值相对较大,底部的高压区范围相对较大. 环状气泡中心轴上的流场速度会在气泡中心有一个加速过程,在气泡顶部附近又迅速减小.