Structure and properties of soda lime silicate glass doped with rare earth

Soda-lime-silicate glasses doped with different rare-earth oxides (La₂O₃, CeO₂, Nd₂O₃, Gd₂O₃ and Y₂O₃) of 1 mol% content were prepared with the traditional melting-quenching methods. In order to reveal the effects of rare-earth elements on the behavior of soda-lime-silicate glass, the structure of soda-lime-silicate glasses doped with different rare-earth oxides were determined with Fourier transform infrared spectrometer using the KBr method, and viscosity of glass melts were measured by the rotating crucible viscometer, the melting temperature of the studied glasses were derived on the basis of Arrhenius Equation, moreover the density, bending strength and molar volume were measured and calculated. The effect of rare-earth dopants on the structure of soda-lime-silicate was analyzed by a shift of peak position and variation in the full-width at half-maximum. The effect of doping rare-earth oxides into glass on the viscosity, density and bending strength was interpreted by changing in structure of soda-lime-silicate glasses doped with rare-earth oxides.     

Co-ion dependence of DNA nuclease activity suggests hydrophobic cavitation as a potential source of activation energy

The source of the activation energy that allows cutting of DNA by restriction enzymes is unclear. A systematic study of the cutting efficiency of the type-II restriction endonuclease EcoRI, with varying background electrolyte ion pair and buffer reported here, shows only a modest dependence of efficiency on cation type. Surprisingly, efficiency does depend strongly on the presumed indifferent anion of the background salt. What emerges is that competition between the background salt anion and the buffer anion for the enzyme and DNA surfaces is crucial. The results are unexpected and counterintuitive from the point of view of conventional electrolyte theory. However, taken together with recent developments in surface chemistry, the results do fall into place and could also suggest a novel mechanism for enzyme activity as an alternative to metal-activated hydrolysis: microscopic cavitation in a hydrophobic pocket might be the source of activation energy. Received 19 June 2000 and Received in final form 17 October 2000     

Crystal structures and luminescent properties of a cadmium(II) metal-organic framework based on tri(4-pyridylphenyl)amine

Abstract

A luminescent cadmium(II) metal-organic framework, [Cd(tppa)₂ (bpdc)₂]_n (1) (tppa?=?tri(4-pyridylphenyl)amine, bpdc =4,4′-biphenyldicarboxylic acid), has been solvothermally synthesized by using Cd(NO₃)₂·4H₂O and a mixture of tppa and bpdc. Single crystal X-ray analysis reveals that 1 crystallizes in the orthorhombic system and Pbcn space group. Its overall structure is a twofold interpenetrated framework, and it shows a porosity of 31.8% based on a calculation by PLATON and a 4-c type topological network with the point symbol of {6^5.8}. In addition, 1 may be exploited as WLED due to its ability to give off yellow light under ultraviolet excitation.     

Relativistic many-body theory with radioactive ion beams: Surface pion condensation

We critically review the present relativistic mean-field theory from the viewpoint of missing pions. We introduce the interesting experimental data on pionic states taken at RCNP. These data seem to suggest the occurrence of pion condensation in the nuclear surface. Qualitative discussion is made on the consequence of surface pion condensation on Gamow-Teller transitions and spin response functions and others. The radioactive ion beams are the tools of studying the unstable nuclei, which have extended nuclear surfaces. We shall start with radioactive ion beams the nuclear surface science, which includes the surface pion condensation as the important ingredient in addition to spin-orbit splitting and surface pairing. Received: 1 May 2001 / Accepted: 4 December 2001     

Ultrasound-assisted extraction and properties of polysaccharide from Ginkgo biloba leaves

Response surface methodology (RSM) was used to optimize the ultrasound-assisted extraction conditions of Ginkgo biloba leaves polysaccharide (GBLP). The optimum extraction conditions for the ultrasound-assisted extraction of GBLP were obtained as liquid to material ratio of 30 mL/g, ultrasonic power of 340 W, and extraction time of 50 min. Under these conditions, the yield of GBLP was 5.37 %. Two chemically modified polysaccharides, CM-GBLP and Ac-GBLP, were obtained by carboxymethylation and acetylation of GBLP. The physicochemical properties of these three polysaccharides were comparatively studied and their in vitro antioxidant activities were evaluated comprehensively. The results showed that the solubility of the chemically modified polysaccharides was significantly enhanced and the in vitro antioxidant activity was somewhat improved. This suggests that carboxymethylation and acetylation are effective methods to enhance polysaccharide properties, but the results exhibited some uncontrollability. At the same time, GBLP has also shown high potential for research and application.     

Solvothermal Syntheses,Crystal Structures,and Luminescent Properties of Two New Cadmium(II) Coordination Polymers Based on Rigid / Flexible Dicarboxylate and N,N′‐Bis(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxydiimide

In order to investigate the effect of the organic ligands on the structures of coordination polymers, two new cadmium(II) coordination polymers based on the different dicarboxylate ligands, namely [Cd₂(bpdc)₂(DPNDI)₂] · 3H₂O · NMF ( 1 ) and [Cd(obb)(DPNDI)] ( 2 ) [H₂bpdc = biphenyl‐4,4′‐dicarboxylate, H₂obb = 4,4′‐oxybis(benzoic acid), DPNDI = N,N′‐bis(4‐pyridyl)‐1,4,5,8‐naphthalene tetracarboxydiimide, and NMF = N‐methylformamide), were synthesized under solvothermal condition and further characterized. Complex 1 shows a twofold interpenetrated pcu topology. Complex 2 possesses a two‐dimensional (2D) layer structure with –ABCD– stacking sequence. Furthermore, the luminescent properties of complexes 1 and 2 are investigated.     

新型低共熔溶剂的制备、表征及物性研究

以氯化1-丁基-3-甲基咪唑鎓([Bmim]Cl)和二元羧酸为原料,由不同摩尔比混合制备了一类新型低共熔溶剂,采用红外光谱对[Bmim]Cl和二元羧酸之间的作用进行了分析。分别测定了其粘度、电导率、密度、折射率等物理性质,并研究了温度、二元羧酸结构和摩尔比对这些物理性质的影响。结果表明,新型低共熔溶剂的粘度随温度的升高而降低,电导率随温度的升高而增加。温度对两者的影响可以采用VTF方程进行精确地拟合。新型低共熔溶剂的密度随温度的升高而呈线性下降。对新型低共熔溶剂的过量摩尔体积进行计算的结果表明,过量摩尔体积均为正值,二元羧酸对过量摩尔体积的贡献远大于[BMIM]Cl,而结构特性的贡献多于物理作用。折射率和密度随二元羧酸碳数的变化趋势基本相似。     

呋喃基聚酯的结构与性能关系研究进展

呋喃基聚酯是指以2,5-呋喃二甲酸(FDCA)为主要单体合成的生物基或部分生物基高分子,其主链含有刚性的呋喃环,因而在结构、性能上与大规模使用的传统石油基芳香族聚酯(如PET、PBT)相似,有望在瓶、片、薄膜、化纤等领域部分替代后者。本文综述了呋喃基聚酯的分子结构、聚集态结构以及力学、气体阻隔、降解等性能方面的最新研究进展,讨论了结构与性能之间的关系。重点关注呋喃基聚酯突出的阻隔性能及其对应的影响因素,主要从分子结构(呋喃环的非对称性和极性)和聚集态结构(结晶等)两方面加以阐明。简介了呋喃基聚酯的发展现状及其在包装、纺织等领域的潜在应用,并展望其主要研究趋势。     

Microbial synthesis of gold nanoparticles: Current status and future prospects

Gold nanoparticles have been employed in biomedicine since the last decade because of their unique optical, electrical and photothermal properties. Present review discusses the microbial synthesis, properties and biomedical applications of gold nanoparticles. Different microbial synthesis strategies used so far for obtaining better yield and stability have been described. It also includes different methods used for the characterization and analysis of gold nanoparticles, viz. UV–visible spectroscopy, Fourier transform infrared spectroscopy, X ray diffraction spectroscopy, scanning electron microscopy, ransmission electron microscopy, atomic force microscopy, electron dispersive X ray, X ray photoelectron spectroscopy and cyclic voltametry. The different mechanisms involved in microbial synthesis of gold nanoparticles have been discussed. The information related to applications of microbially synthesized gold nanoparticles and patents on microbial synthesis of gold nanoparticles has been summarized.     

Preparation and characterization of modified graphite oxide/poly(propylene carbonate) composites by solution intercalation

Modified graphite oxide (MGO)/Poly (propylene carbonate) (PPC) composites with excellent thermal and mechanical properties have been prepared via a facile solution intercalation method. An intercalated structure of MGO/PPC composites was confirmed by X-ray diffraction and scanning electron microscope. The thermal and mechanical properties of MGO/PPC composites were investigated by thermal gravimetric analysis, differential scanning calorimetric, dynamic mechanical analysis, and electronic tensile tester. Due to the nanometer-sized dispersion of layered graphite in PPC matrix and the strong interfacial interaction between MGO and PPC, the prepared MGO/PPC composites exhibit improved thermal and mechanical properties in comparison with pure PPC. Compared with pure PPC, the MGO/PPC composites show the highest thermal stability and the T_g is 13.8 °C higher than that of pure PPC, while the tensile strength (29.51 MPa) shows about 2 times higher than that of pure PPC when only 3.0 wt.% MGO is incorporated. These results indicate that this approach is an efficient method to improve the properties of PPC.