废旧橡胶改性沥青的老化研究现状

废旧橡胶改性沥青可显著延长路面寿命。本文综述了国内外废旧橡胶改性沥青的热氧老化、紫外老化和水老化行为,使用宏观性能和微观结构变化分析了橡胶改性沥青老化特点。橡胶改性沥青在热、氧、紫外、水的作用下发生老化,软化点升高,针入度降低,羰基含量增加。特别是光、氧老化对经过水老化后的橡胶改性沥青老化作用尤为明显,水溶解了部分老化产物促进了沥青的老化。目前对于橡胶改性沥青老化过程中胶粉、沥青的结构性能变化和其环境耦合因素对橡胶改性沥青的老化研究及分析手段还很少,在今后的研究中须引起重视。     

Development of a method using high‐performance liquid chromatographic fingerprint and multi‐ingredients quantitative analysis for the quality control of Yangxinshi Pian

A simple and reliable method of high‐performance liquid chromatography with diode array detection method was developed for fingerprint analysis and simultaneous determination of six compounds including puerarin, salvianolic acid B, berberine hydrochloride, palmatine chloride, dehydrocorydaline, and icariin in the Chinese medicine preparation Yangxinshi Pian. The separation was performed on an Agilent Eclipse XDB‐C₁₈ reserved‐phase column (250 mm × 4.6mm I.D., 5 μm) using gradient elution with 50 mmol/L monopotassium phosphate aqueous solution and methanol as mobile phase at a flow rate of 1.0 mL/min. The column operating temperature was set at 30°C, and the detection wavelength was 280 nm. The method was validated by linearity, precision, accuracy, stability, and recovery. For fingerprint analysis, 25 peaks were selected as the common peaks, and four kinds of similarities including cosine similarity (S), ratio of similarity (S′), projection content similarity (C), and content similarity (P) were applied to evaluate the quality consistency of different batches of Yangxinshi Pian. The results showed that the developed method was an efficient tool for quality evaluation of Yangxinshi Pian.     

Cytotoxic cassane diterpenoids from the seeds of Caesalpinia sappan

Phytochemical investigation on the seeds of Caesalpinia sappan led to the isolation of five new cassanetype diterpenoids, named 11-oxo-phanginin A(1), caesalsappanins O–Q(2–4) and phanginin U(5),together with five known compounds. The structures of the new compounds were elucidated by extensive analysis of mass spectrometric and 1D and 2D NMR spectroscopic data. All the new compounds showed moderate cytotoxic effects on human breast cancer MCF-7 and human colon cancer HCT116 cell lines.     

Shape change of calcite single crystals to accommodate interfacial curvature: Crystallization in presence of Mg2+ ions and agarose gel-networks

Synthetic calcite single crystals,due to their strong crystal habit,tend to grow into characteristic rhombohedra.In the nature,biogenic calcite crystals form composites together with biomacromolecular materials,spurring investigations of how the growing calcite single crystals change their habit to satisfy the curvature of the organic phase.In this work,we examine calcite crystallization on a flat surface of glass slide and a curved surface of polystyrene(PS)sphere.The crystals exhibit tiny contact area onto the glass substrate that is averagely only 15% of their projected area on the substrate.In sharp contrast,the contact area greatly increase to above 75% of the projected area,once magnesium ions or agarose gel networks are introduced into the crystallization media.Furthermore,the calcite crystals form rough and step-like interfaces with a curved surface.However,the interfaces become smooth and curved as the crystals grow in presence of magnesium ions or agarose gel networks.The discrepancy between the interfacial structures implies kinetic effects of the additives on the crystallization around the surfaces. This work may provide implications for understanding the formation mechanisms of single-crystal composite materials.     

Isomorphism in ternary complex: Poly(ethylene oxide), urea and thiourea

Herein,we demonstrated that poly(ethylene oxide)(PEO),urea and thiourea can crystallize into novel ternary complex with the molar ratio of guest polymer and host small molecule as 3:2,and proved that the ternary complex behaves isomorphism phenomenon by varying the ratio between urea and thiourea for the first time.This observation gives a boost to prepare co-crystals of different small molecules that cannot be obtained by direct mixing without the aid of polymer chains.     

Phosphorus modified MoO<Subscript>3</Subscript>–Bi<Subscript>2</Subscript>SiO<Subscript>5</Subscript>/SiO<Subscript>2</Subscript> catalyst for gas-phase epoxidation of propylene by molecular oxygen

The phosphorus (P) modified MoO₃–Bi₂SiO₅/SiO₂ catalyst was prepared by a simple co-impregnation method and investigated in the epoxidation of propylene by molecular oxygen. The catalyst was characterized by X-ray diffraction (XRD), N₂ adsorption–desorption analysis, NH₃-temperature-programmed desorption (NH₃-TPD), transmission electron microscopy, and Raman spectroscopy. It was found that the P-modified MoO₃–Bi₂SiO₅/SiO₂ catalyst with a P/Mo molar ratio of 0.5 exhibits the best catalytic performance for epoxidation of propylene by O₂, the TOFs for propylene oxide (PO) formation was four times higher than that of the unmodified one at 633 K. The modification by P could promote the dispersion of MoO₃ nanoparticles and increase the number of weak and moderate acid sites with respect to the phosphorus-free MoO₃–Bi₂SiO₅/SiO₂ catalyst, which were beneficial to the formation of PO. Moreover, the introduction of P also could protect the mesoporous structure by inhibiting the formation of Bi₂Mo₃O₁₂, which was beneficial to the dispersion of active species. We suppose that the phosphorus, bismuth and molybdenum species of P-modified MoO₃–Bi₂SiO₅/SiO₂ catalyst play important roles for propylene epoxidation by molecular oxygen.     

蒸氨法制备铜硅催化剂的二甲醚水蒸气重整制氢性能

采用蒸氨法制备出不同Cu负载量的xCu/SiO_2-AE催化剂,并将其用于二甲醚水蒸气重整制氢反应。当Cu负载量为30%(w)时,30Cu/SiO_2-AE催化剂表现出最佳的催化性能。结果显示,该方法制备的催化剂表面具有高度分散的CuO和层状硅酸铜物相,经还原后分别形成Cu~0和Cu~+物种。与常规浸渍法制备的30Cu/SiO_2-IM催化剂相比,蒸氨法制备的30Cu/SiO_2-AE催化剂具有优异的催化稳定性和活性,这与其独特的层状结构和表面Cu~0与Cu~+之间的协同作用相关。     

重力场流分离系统用于聚苯乙烯颗粒的分离条件优化

重力场流分离是最简单的场流分离(gravitational flow-field fractionation,GrFFF)技术,常用于分离粒径几微米到几十微米的颗粒及生物样品。利用自组装加工的重力场流分离仪器分离3种不同粒径(3、6、20μm)的聚苯乙烯(PS)颗粒。自制了一种混合表面活性剂,并与商品化的表面活性剂FL-70进行了比较。通过均匀设计优化流速、混合表面活性剂中聚乙二醇辛基苯基醚(Triton X-100)的质量分数、载液黏度、停流时间等分离条件,以分离度(Rs)和保留比(R)为评价指标,发现FL-70的分离效能略优于自制的混合表面活性剂,可实现3种PS颗粒的完全分离(Rs1为1.771,Rs2为2.074)。结果表明该系统具有良好的分离性能。     

Further results on <Emphasis Type="Italic">B</Emphasis>-tensors with application to location of real eigenvalues

We give a further study on B-tensors and introduce doubly B-tensors that contain B-tensors. We show that they have similar properties, including their decompositions and strong relationship with strictly (doubly) diagonally dominated tensors. As an application, the properties of B-tensors are used to localize real eigenvalues of some tensors, which would be very useful in verifying the positive semi-definiteness of a tensor.     

Multi-recurrence and van der Waerden systems

We explore recurrence properties arising from dynamical approach to the van der Waerden theorem and similar combinatorial problems. We describe relations between these properties and study their consequences for dynamics. In particular, we present a measure-theoretical analog of a result of Glasner on multi-transitivity of topologically weakly mixing minimal maps. We also obtain a dynamical proof of the existence of a C-set with zero Banach density.