反铁磁晶体表面上的非线性电磁波

研究了反铁磁晶体与电介质交界面上非线性TM电磁波的传播特性 .给出了Ex Hy 和Ez Hy 的相图 ,描述了表面波电磁场三分量之间的制约变化关系 .分析了导波的色散特性和磁场峰值位置随传播功率变化的特点 .分析表明 ,反铁磁晶体表面上的TM电磁波存在频率通带和禁带 ,其带宽是功率的函数 ,通过调节导波的功率可以有效地实现通带和禁带之间的转换 .揭示了在一定条件下 ,反铁磁晶体表面支持的非线性TM波是反向表面波 ,其群速度与相速度反向 .     

The qualitative behavior for approximate Dirac-harmonic maps into stationary Lorentzian manifolds

For a sequence of approximate Dirac-harmonic maps from a closed spin Riemann surface into a stationary Lorentzian manifold with uniformly bounded energy, we study the blow-up analysis and show that the Lorentzian energy identity holds. Moreover, when the targets are static Lorentzian manifolds, we prove the positive energy identity and the no neck property.

     

Syntheses,Structure, and Luminescent Property of a New 2D Nd(III) Coordination Polymer Based on 4′-(4-Carboxyphenyl)-4,2′:6′,4″-Terpyridine

Russian Journal of Coordination Chemistry - A new lanthanide coordination polymer (Ln-CP) based on Nd(III), [Nd2(Cptpy)2(Glu)2(H2O)2]n · 5n(H2O) (Ι) (HCptpy =...     

Aggregation and Tunable Color Emission Behaviors of l-Glutamine-Derived Platinum(II) Bipyridine Complexes by Hydrogen-Bonding, π–π Stacking and Metal–Metal Interactions

A n l -glutamine-derived functional group was introduced to the bis(arylalkynyl)platinum(II) bipyridine complexes 1 – 4 . The emission could be switched between the ³MLCT excited state and the triplet excimeric state through solvent or temperature changes, which is attributed to the formation and disruption of hydrogen-bonding, π–π stacking, and metal–metal interactions. Different architectures with various morphologies, such as honeycomb nanostructures and nanospheres, were formed upon solvent variations, and these changes were accompanied by ¹H NMR and distinct emission changes. Additionally, yellow and red emissive metallogels were formed at room temperature due to the different aggregation behaviors introduced by the substituent groups on bipyridine. The thermoresponsive metallogel showed emission behavior with tunable colors by controlling the temperature. The negative Gibbs free-energy change (ΔG) and the large association constant for excimer formation have suggested that the molecules undergo aggregation through hydrogen-bonding, π–π, and metal–metal interactions, resulting in triplet excimeric emission.     

One-pot synthesis,characterization and properties of acid-catalyzed resorcinol/formaldehyde cross-linked silica aerogels and their conversion to hierarchical porous carbon monoliths

A rapid and facile synthesis of resorcinol/formaldehyde cross-linked silica (RF/SiO₂) aerogels was carried out in one pot based on an acid-catalyzed route, instead of the previously reported base-catalyzed ones. The gelation time was reduced to several hours at room temperature while it took several days even under heating conditions in the base-catalyzed ones. The interpenetrating network of RF/SiO₂ aerogels showed similar porous structures with those of silica aerogels or RF aerogels. Their thermal conductivity was as low as that of the typical glass wool materials. The mechanical properties are characterized by dynamic mechanical analysis and compression testing. At room temperature, the results of compression testing show that the compressive Young’s modulus or ultimate failure strength of RF/SiO₂ aerogel specimen is higher than that of native SiO₂ aerogels with a similar density. The one-pot method improves the efficiency and reduces the cost of RF/SiO₂ aerogels. The hierarchical porous carbon monoliths are also converted from carbonized RF/SiO₂ aerogels by an additional HF treatment. Hence, they could be further explored as multifunctional candidate materials for thermal, mechanical, and electrochemical applications.     

Synthesis and Hierarchical Self‐Assembly of Diphenylalanine‐Based Homopolymer and Copolymers By RAFT Polymerization

Dipeptide diphenylalanine has attracted significant research interests because of its ability to self‐assemble into various nanostructures such as nanotubes, nanowires, and nanoribbons. In this article, we present the synthesis and self‐assembly of a novel diphenylalanine‐based homopolymer and block/random copolymers by the reversible addition–fragmentation chain transfer (RAFT) polymerization of an acrylamide having a dipeptide moiety. The RAFT polymerization of N‐acryloyl‐l ,l ‐diphenylalanine (A‐Phe‐Phe‐OH) afforded novel amino acid‐based polymers with predetermined molecular weights and relatively narrow‐molecular weight distributions. The hierarchical self‐assembled structures of poly(A‐Phe‐Phe‐OH), which involve nanorods, larger nanofiber‐like microcrystals, and fiber bundles, were characterized by atomic force microscopy (AFM), transmission electron microscopy, scanning electron microscopy, and dynamic light scattering measurements. The circular dichroic measurements of poly(A‐Phe‐Phe‐OH) revealed its characteristic chiroptical property, which is affected by the nature of the solvents and the addition of urea and salts via hydrophobic, hydrogen bonding, and electrostatic interactions. Thermo‐ and pH‐responsive block and random copolymers composed of A‐Phe‐Phe‐OH and N‐isopropylacrylamide were synthesized by RAFT polymerization, and the thermoresponsive properties and assembled structures of the resulting copolymers were investigated by AFM and turbidity measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2562–2574     

Synthesis of pH‐responsive photocrosslinked hyaluronic acid‐based hydrogels for drug delivery

Photocrosslinked hyaluronic acid/poly(vinyl alcohol)‐styrylpyridinium (HA/PVA‐SbQ) hydrogels were synthesized for controlled antitumor drug delivery. The photocrosslinking reaction was rapid, and the time required for completely converting into the insoluble hydrogels was less than 500 s on exposure to 5 mW/cm² UV light irradiation. The resulting hydrogels exhibited sensitivity to the pH value of the surrounding environment. Scanning electron microscopic analysis revealed that the morphology and the pore size of the hydrogels could be controlled by changing the ratio of HA and PVA‐SbQ in the formulations. Paclitaxel (PTX)‐loaded hydrogel could also be formed rapidly by UV irradiation of a mixed solution of HA/PVA‐SbQ and PTX. Release profiles of PTX from the hydrogels showed pH‐dependent and sustained manner. Moreover, our data revealed that PTX released from the HA hydrogels remained biologically active and had the capability to kill cancer cells. In contrast, control groups of HA hydrogels without PTX did not exhibit any cytotoxicity. This study demonstrates the feasibility of using HA‐based hydrogels as a potential carrier for chemotherapeutic drugs for cancer treatments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Pt-Like Oxygen Reduction Activity Induced by Cost-Effective MnFeO2/N-Carbon

The development of effective and affordable electrocatalysts for the oxygen reduction reaction (ORR) is critical for the renewable-energy technologies. Here, we present a new manganese iron oxide (MnFeO₂) as a cost-effective material for the ORR with Pt-like electrochemical properties. Pyrolysis of hybrid agar hydrogel on NaCl nanocrystals furnishes a unique structure in which the active MnFeO₂ particles are uniformly immobilized in the nitrogen-doped porous carbon aerogels (MnFeO₂/NPC). Nitrogen-doped carbon is introduced to construct porous mass-transfer channels and reduce self-aggregation of the MnFeO₂ particles. It is found that the formation of the MnFeO₂ phase greatly depends on the pyrolysis temperature. Benefiting from the synergy of MnFeO₂ and NPC, the MnFeO₂/NPC can actually be as good as the Pt/C catalyst for the ORR, with an onset-potential of 0.98 V and a half-wave potential of 0.86 V, combined with demonstrating a superior stability and tolerance to methanol.     

Magnetic carbon nanotubes: synthesis by a simple solvothermal process and application in magnetic targeted drug delivery system

A poly(vinyl chloride) (PVC) main chain was grafted with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) containing a quaternary amine group using atom transfer radical polymerization. The successful synthesis of a PVC-g-PDMAEMA graft copolymer was confirmed by Fourier transform infrared, nuclear magnetic resonance, thermogravimetric analysis, and transmission electron microscopy. The PVC-g-PDMAEMA graft copolymer was used as a structure-directing agent (SDA) for the fabrication of a mesoporous thin film containing a titanium dioxide (TiO₂) layer. To control the porosity of the resultant inorganic layer, the ratio of SDA to TTIP as well as the concentration of the sol?Cgel was varied. The structure and porosity of the mesoporous film were characterized by XRD and SEM analysis. The mesoporous TiO₂ film fabricated on the FTO surface was used as a photoanode for the dye-sensitized solar cell (DSSC). DSSC performance was the greatest when using TiO₂ film with a higher porosity and lower interfacial resistance. The highest energy conversion efficiency reached 3.2?% at 100?mW/cm², which was one of the highest reported values for a quasi-solid-state DSSC with 600-nm-thick TiO₂ film.     

中国古代热力发展简史

在漫长的历史岁月中,人类的每一次跨越,每一次进步,都有一只强劲的命运之手——热力,在不断引导着人类前进的轨迹,在启迪、激荡着人类参悟科技的玄机。中国古代的热力技术曾长时间处于世界领先地位。中国人对热力的探索有着世界其他国家无法比拟的悠久历史,创造了灿烂辉煌的成就,为中华文明和世界文明做出了重要的贡献,值得我们骄傲。但由于封建社会的封闭性和人们思维方式的保守性,排斥外来科学文化的冲击,再加上研究方法的不科学性,使得中国的热力技术与科学在近现代开始落后于西方,这是一件非常遗憾的事。本文回溯了中华文明在茫茫历史长河中不断与热力的探索、交锋的历史,梳理了中国热力发展的脉络。