Exact thermodynamic behavior of a generalized spin-isospin ising system on the Bethe lattice

We study a generalized Ising system consisting of a Bethe lattice on every site of which two spin-1/2 and two isospin-1/2 (or atomic species A) states can be realized, the spin-species interacting with appropriate nearest neighbor couplings. The system is equivalent to that of four states per site and we obtain its exact thermodynamic behavior. The case of a fixed concentration of species is the annealed or liquid magnetic binary alloy. The temperature dependence of the short-range-order (SRO) parameter of such systems is obtained as an application of the theory and discussed in connection with relevant material from the literature. When fixing both the concentration and the nearest neighbor spatial correlation of the species, we obtain Eggarter's formulas for the frozen-in species problem, which therefore are only approximately valid even on the Bethe lattice.     

Hydrogel nanonetworks with functional core-shell structure

Nanohydrogel particles of poly(acrylonitrile-co-N-isopropylacrylamide (p(AN-c-NIPAM)) were synthesized using a microemulsion polymerization technique. Highly monodisperse nanohydrogel particles e.g. 50-150 nm, and various morphology such as core-shell and connected beads were obtained. It was shown that the shell thickness and the size of particles can be tuned by the monomer concentrations and their ratios as well as by the utilization of different crosslinkers. The hydrophobic core monomer, AN was converted to amidoxime groups to increase the hydrophilicity of the nanogels which provide more hydrophilic character and impart new functionality to the nanonetwork. Transmission electron microscopy (TEM), and dynamic light scattering (DLS) techniques were employed for the particle size characterizations. The amidoximation reaction was confirmed by FT-IR spectroscopy.     

介孔材料在烯烃环氧化中的催化应用

本文综述了介孔材料在烯烃环氧化反应中的应用,包括材料的制备方法、催化性能以及活性中心的表征。通过硅钛原子的合理匹配可以达到四配位钛的高度分散,从而提高催化活性。硅烷化处理增加材料表面的疏水性,能够大幅度提高活性和选择性。通过多种谱学和分子模拟等手段可表征骨架钛及其配位情况。     

晶化温度对中孔分子筛（M41S）结构转变的影响

在低表面活性剂浓度及低表面活性剂与氧化硅比的条件下，研究了十六烷基三甲基溴化铵－硅酸钠体系中晶化温度对中孔分子筛Ｍ４１Ｓ材料结构转变的影响。结果有，晶化温度提高至１３５℃改变了原六方晶相ＭＣＭ－４１的结构，晶化温度提高到１５０℃后，中孔结构六方ＭＣＭ－４１晶格转变为变不稳定的层状相，     

镧对含锡、锑残余元素的34CrNi3Mo钢热塑性的改善作用

采用Gleeble-1500热模拟机测定了不同含量的残余元素锡、锑及稀土镧对低氧、低硫的34CrNi3Mo钢热塑性的影响;采用SEM及EDS手段研究了稀土镧对不同锡、锑含量的钢断裂方式的影响及在其中形成夹杂物的情况。结果表明,用稀土金属可以改善低氧、低硫钢中残余元素对钢性能的危害;镧可以和钢中较低含量的锑作用生成镧锑金属间化合物,并且发现了少量的镧锡金属间化合物。     

Synthesis of novel mesoporous silica spheres with starburst pore canal structure

Novel spherical mesoporous silica materials with uniform diameters and starburst mesopore structures were synthesized by a simple one-step procedure with ethanol as the co-solvent in dilute aqueous solution and their formation mechanism was proposed. The arrangement of the pore canal and the diameter of the sphere could be tailored by altering the concentration of ethanol.     

Synthesis, X-ray crystal structures, and gas sorption properties of pillared square grid nets based on paddle-wheel motifs: implications for hydrogen storage in porous materials

A systematic modulation of organic ligands connecting dinuclear paddle-wheel motifs leads to a series of isomorphous metal-organic porous materials that have a three-dimensional connectivity and interconnected pores. Aromatic dicarboxylates such as 1,4-benzenedicarboxylate (1,4-bdc), tetramethylterephthalate (tmbdc), 1,4-naphthalenedicarboxylate (1,4-ndc), tetrafluoroterephthalate (tfbdc), or 2,6-naphthalenedicarboxylate (2,6-ndc) are linear linkers that form two-dimensional layers, and diamine ligands, 4-diazabicyclo[2.2.2]octane (dabco) or 4,4'-dipyridyl (bpy), coordinate at both sides of Zn(2) paddle-wheel units to bridge the layers vertically. The resulting open frameworks [Zn(2)(1,4-bdc)(2)(dabco)] (1), [Zn(2)(1,4-bdc)(tmbdc)(dabco)] (2), [Zn(2)(tmbdc)(2)(dabco)] (3), [Zn(2)(1,4-ndc)(2)(dabco)] (4), [Zn(2)(tfbdc)(2)(dabco)] (5), and [Zn(2)(tmbdc)(2)(bpy)] (8) possess varying size of pores and free apertures originating from the side groups of the 1,4-bdc derivatives. [Zn(2)(1,4-bdc)(2)(bpy)] (6) and [Zn(2)(2,6-ndc)(2)(bpy)] (7) have two- and threefold interpenetrating structures, respectively. The non-interpenetrating frameworks (1-5 and 8) possess surface areas in the range of 1450-2090 m(2)g(-1) and hydrogen sorption capacities of 1.7-2.1 wt % at 78 K and 1 atm. A detailed analysis of the sorption data in conjunction with structural similarities and differences concludes that porous materials with straight channels and large openings do not perform better than those with wavy channels and small openings in terms of hydrogen storage through physisorption.     

无机层状复合氢氧化物中顺铂-DNA模型分子的选择性插入

药物分子的选择性包裹和控制释放是药物研究领域中具有挑战性的研究方向。本文研究表明:顺铂-DNA模型分子cis-[Pt(NH₃)₂(5′-GMP)₂](5′-GMP 5′-单磷酸鸟苷)可插入无机层状复合氢氧化物[Zn_0.68Al_0.32(OH)₂](NO₃)_0.32·mH₂O。但另一种层状复合氢氧化物[LiAl₂(OH)₆]Cl·H₂O由于其阳离子层中正电荷密度较高、阳离子层与层间阴离子之间静电作用较强,因而顺铂-DNA模型分子不能通过离子交换方式插入其层间。光谱数据证实插入层间的顺铂-DNA模型分子结构不变。这可能为铂-DNA分子的传递提供新的方法。