基于层状过渡金属氧族化合物原位插层结构的研究进展

利用客体插层剂原位插层到二维层状材料, 不仅能够在原子尺度上实现对材料电子结构和本征物理性质的调控, 提高材料的载流子浓度、迁移率、磁学、光学和热学等物理性质, 而且还有望拓展其在光电子器件、能源存储与转化以及光电催化等方面的应用. 近年来, 探索合适的方法制备具有不同类型和功能的二维插层新结构已逐渐成为材料科学、物理、化学等领域的研究热点. 由于独特的电子结构和优异的性能, 二维层状过渡金属氧族化合物材料作为插层主体的插层结构受到了研究人员的广泛关注. 本文选取过渡金属氧族化合物为对象, 综述了不同种类插层剂原位插层合成方法(如碱金属插层、非碱金属原子插层、聚合物插层、有机小分子插层、还原氧化石墨烯插层), 提出了通过系列方法影响层间作用力以及利用晶体各向异性等工艺来实现新型插层结构的原位合成策略, 并展望了新型插层材料在电、磁、光、热、锂电、催化等众多领域的潜在应用前景.     

A FeCl3-promoted highly atropodiastereoselective cascade reaction: synthetic utility of radical cations in indolostilbene construction

The FeCl₃-promoted oxidative cyclization/coupling of acetamidostilbenes possessing 3-methoxy, 4-methoxy and 3,5-methoxy substitutions (21), (22) and (23) is described. Only 3,5-substitution gave rise to novel indolostilbenes, each possessing two stereogenic axes (axially chiral but racemic dimers (39) and (40)). The 4-methoxy substituted acetamidostilbenes, by contrast, yielded the bisindoline dimer (36).     

Enantioselective determination of modafinil in pharmaceutical formulations by capillary electrophoresis, and computational calculation of their inclusion complexes

A fast capillary electrophoretic method is described for the separation and determination of the enantiomers of the novel wake-promoting agent, modafinil. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, buffer concentration, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 5 min with resolution factor Rs?=?2.51, using a bare fused-silica capillary and a background electrolyte (BGE) of 25 mM H₃PO₄?1 M tris solution; pH 8.0; containing 30 mg mL^?1 of sulfated-β-cyclodextrin (S-β-CD). The separation was carried out in normal polarity mode at 25 ^?C, 18 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy were included. The developed method was successfully applied to the assay of enantiomers of modafinil in pharmaceutical formulations. The computational calculations for the enantiomeric inclusion complexes rationalized the reasons for the different migration times between the modafinil enantiomers.     

Study of the Degradation Kinetics of Carvedilol by Use of a Validated Stability-Indicating LC Method

The objectives of this investigation were to establish a validated stability-indicating LC method for assay of carvedilol and to study the degradation behaviour of the drug under different ICH-recommended stress conditions. Chromatographic separation was achieved on a C₁₈ column with 55:45 (%, v/v) acetonitrile–0.02 m phosphate buffer, pH 3.5, as mobile phase at a flow rate of 1.0 mL min^?1; detection was by UV absorbance at 242 nm. The method was validated for linearity, precision, accuracy, robustness, specificity, and sensitivity, with the bulk drug. The drug was subjected to forced degradation and peaks of all the degradation products were well resolved from that of the pure drug, with significantly different retention times, which indicates the specificity and stability-indicating properties of the method. First-order degradation kinetics of carvedilol were observed under acidic and alkaline conditions. When the utility of the method was verified by analysis of the drug in marketed tablets and a nano-emulsion formulation, the assay was found to be 98.60–99.61 and 99.52–99.87, respectively. These results indicate the method can be successfully used for routine analysis of carvedilol in the bulk drug and in pharmaceutical dosage forms.     

A simple method for quantitative analysis of elements by WD‐XRF using variable dilution factors in fusion bead technique for geologic specimens

A common approach in the quantitative analysis of geological samples by X‐ray fluorescence is to establish calibration lines for elements of interest by using several reference materials (RMs) and/or the combination of RMs and pure chemicals. Herein, we introduce an alternative to use only two RMs, to establish a calibration application. Variation of the dilution factor is employed to generate a dynamic range of concentrations for each RM and to evenly furnish the calibration lines to analyze certain matrices. A wide range of dilution factors were employed from 2–54 times dilution (with respect to the flux to sample ratios). Calibration lines for the major elements including: Si, Al, Ca, Fe, Mg, Na, Mn, and Ti show an extremely high level of linearity with all elements. R² values greater than 0.9990 were obtained for each analyzed element. The calibration application was validated by checking against a variety of geological RMs including petroleum and carbonate rich shale (SGR‐1), Muscovite rich marine shale (SBC‐1), metamorphic rock (SDC‐1), carbonatite (COQ‐1), and types of igneous rocks (GSP‐2, BCR‐2, AGV‐2, QLO‐1, and W‐2). Mixtures of Alumina and Silica (ARG‐1 and ARG‐2) and pure SiO₂ beads were also analyzed to further check the application. Rigorous statistical analysis on the RMs confirms the reliability of the calibration application for the employed matrices. Copyright © 2016 John Wiley & Sons, Ltd.     

Lead sulfate used as the positive active material of lead acid batteries

Lead sulfate is produced when a lead acid battery discharges, and it is also known that big PbSO₄ crystals are less active than the smaller ones because they dissolve slower, thus result in failure of the battery. However, little is known if chemically prepared PbSO₄ can be used as active material of lead acid batteries. Here, we report the preparation of PbSO₄ by facile chemical precipitation of aqueous lead acetate with sodium sulfate and its utilization as the positive active material. The results show that the PbSO₄ alone is not good enough for the purpose, but its mixtures with Pb₃O₄ are as excellent as the industrial leady oxide. For example, the mixtures containing 5, 10, 20, and 30 wt.% of Pb₃O₄ discharge 78.2, 92.9, 88.0, and 91.5 mAh g^?1 at a current density of 100 mA g^?1, respectively. Also, the one with 10 % Pb₃O₄ remains 93 % capacity in 150, 100 % DOD cycles.     

Pressure anisotropy effects on nonlinear electrostatic excitations in magnetized electron-positron-ion plasmas

The propagation of linear and nonlinear electrostatic waves is investigated in a magnetized anisotropic electron-positron-ion (e-p-i) plasma with superthermal electrons and positrons. A two-dimensional plasma geometry is assumed. The ions are assumed to be warm and anisotropic due to an external magnetic field. The anisotropic ion pressure is defined using the double adiabatic Chew-Golberger-Low (CGL) theory. In the linear regime, two normal modes are predicted, whose characteristics are investigated parametrically, focusing on the effect of superthermality of electrons and positrons, ion pressure anisotropy, positron concentration and magnetic field strength. A Zakharov-Kuznetsov (ZK) type equation is derived for the electrostatic potential (disturbance) via a reductive perturbation method. The parametric role of superthermality, positron content, ion pressure anisotropy and magnetic field strength on the characteristics of solitary wave structures is investigated. Following Allen and Rowlands [J. Plasma Phys. 53, 63 (1995)], we have shown that the pulse soliton solution of the ZK equation is unstable to oblique perturbations, and have analytically traced the dependence of the instability growth rate on superthermality and ion pressure anisotropy.     

Heat transfer augmentation of a car radiator using nanofluids

The car radiator heat transfer enhancement by using TiO₂ and SiO₂ nanoparticles dispersed in water as a base fluid was studied experimentally. The test rig is setup as a car radiator with tubes and container. The range of Reynolds number and volume fraction are (250–1,750) and (1.0–2.5 %) respectively. Results showed that the heat transfer increases with increasing of nanofluid volume fraction. The experimental data is agreed with other investigator.     

Low-cost low-threshold diode end-pumped Tm:YAG laser at 2.016?μm

We report a low-threshold continuous-wave Tm:YAG laser that can be excited near 785?nm with low-cost, single-mode AlGaAs laser diodes. Low-threshold operation was achieved using a tightly focused, astigmatically compensated x-cavity containing a 2-mm-thick Tm:YAG crystal with 5?% Tm³⁺ concentration. Two linearly polarized single-mode diodes operating at 785.8?nm were polarization coupled to end pump the resonator. With a 6?% output coupler, as high as 32?mW of output power could be obtained at 2016?nm with 184?mW of incident pump power. The output could be further tuned in the 1935?C2035?nm range. Slope efficiency measurements indicated that cross-relaxation was very effective at this doping level. With a 2?% output coupler, lasing could be obtained with as low as 32.3?mW of pump power. In the limit of vanishing output coupling, the incident threshold pump power could be reduced to as low as 25?mW. To our knowledge, this is among the lowest lasing thresholds reported to date for continuous-wave, room-temperature thulium lasers.     

新型二氧代氮杂茂并[3’,4’-d]N-甲基异噁唑四氯化铁酸盐衍生物的合成及其生物活性

硫酸二甲酯作为N-甲基化试剂,与相应的异噁唑啉反应,并在盐酸中三氯化铁作为阴离子交换试剂,合成了15个未见文献报道的2-甲基-3-(1’,2’-二-O-环亚己基二氧乙基)-5-芳基-3a,6a-二氢-4,6-二氧代氮杂茂并[3’,4’-d]异噁唑四氯化铁酸盐衍生物4a～4o.化合物4a～4o结构结构经1H NMR,IR和元素分析确证,并进行了初步药物活性筛选,大部分化合物显示了不同程度的抗癌和抗炎症性及免疫性疾病活性.体外抗癌活性试验表明,当样品浓度为20μg/mL时,除了4h无活性外,其余化合物对细胞分裂周期磷酸酯酶Cdc25B的抑制率为≥97.55%.此外,体外白细胞共同抗原活性试验表明,当样品浓度为20μg/mL时,所有化合物4a～4o对白细胞共同抗原CD45蛋白酪氨酸磷酸酶A具有良好的抑制活性,其抑制率为68.41%～93.38%.在此基础上,初步讨论了该类化合物的构效关系.