Kinetics and Modeling of Vinyl Acetate Graft Polymerization from Poly(ethylene glycol)

A kinetic model for the graft polymerization of VAc from PEG was developed using the method of moments. Experiments were carried out to verify the model. The effect of various parameters, such as initiator concentration, temperature, and PEG molecular weight on the polymerization kinetics was examined. Polymerization rate, grafting efficiency, graft copolymer molecular weight, and PEG grafted ratio were measured. The model was in good agreement with the experimental data. No gel effect was observed at the studied PEG/VAc weight ratio of 1:1. The chain transfer constant to PEG was correlated to be . The model was also applied in a semi‐batch reaction and compared with the experimental results.

     

Study of the Natural Product Intermediates of Steviolbioside,Steviol, and Isosteviol; O‐ and N‐Acylated Forms of Benzotriazoyl Esters

Glycosides, steviolside, and rubaudioside A, which are extracted from the leaves of Stevia rebaudiana, can be used as sweetener for food additive. Intermediates of steviolbioside, steviol, and isosteviol are very stable compounds obtained from benzotriazol‐1‐yloxtri(pyrrolidinol)phosphonium hexafluorophosphate. They are suitable to be used in amide and amide dimer synthesis. These nature product intermediates possess special characteristics. The spectra data showed two tautomeric groups: an ester form and an amide form. Their nuclear magnetic resonance, mass and chromatographic/mass/mass spectra were examined.     

简并四波混频信号的饱和效应

本文由光学Bloch方程和密度矩阵方程出发,研究了二能级系统共振型简并四波混频(DFWM)的饱和效应,给出了DFWM信号强度与泵浦光强度的函数关系.饱和泵浦光强的大小取决于纵向弛豫时间T1和横向弛豫时T2.对理论结果与相应实验进行了比较,表明二者符合得很好.     

Visualizing the Dynamics of Temperature‐ and Solvent‐Responsive Soft Crystals

We demonstrate that three flexible MOFs termed FJI‐H11‐R (FJI‐H=Hong's group in Fujian Institute of Research on the Structure of Matter, R=Me, Et, ⁱPr) can reversibly respond to temperature and solvents via structural transformations, which can be visualized by in situ single‐crystal X‐ray snapshot analyses. FJI‐H11‐R exhibit colossal anisotropic thermal expansion, with a record‐high uniaxial positive thermal‐expansion coefficient of 653.2×10^?6 K^?1 observed in FJI‐H11‐Me. Additionally, large c‐axial shrinkage of 32.4 % is also observed during desolvation. The stimuli‐responsive mechanism reveals the structural evolutions are related to the rotations and deformations of the organic linkers.     

阻抑动力学光度法测定痕量邻苯二酚的研究

在硫酸介质中,Ｃｕ（Ⅱ）能催化Ｈ２Ｏ２氧化偶氮胂（Ⅰ）的褪色反应,但加入邻苯二酚后,邻苯二酚能灵敏地阻抑该氧化褪色反应。作者研究了该阻抑褪色反应的动力学条件,从而建立了一种新的测定痕量邻苯二酚的方法。该法的测定范围为０．０～２００ｎｇ／Ｌ,检出限为９０．７ｎｇ／Ｌ。用于实验样品中邻苯二酚的测定,获得了满意的结果。     

离子束技术和薄膜功能材料研究

总结了武汉大学物理系加速器实验室近年来在离子束技术和薄膜功能材料研究方面的主要成果，包括：大型离子束及薄膜研究设备的建造和改进，非晶合金、高温超导、Ｃ６０、β－Ｃ３Ｎ４等多种新型薄膜功能材料的离子束合成和材料改性研究．这是近１０年来薄膜功能材料最前沿的研究课题，这些研究工作具有一定的特色，并取得诸项阶段性成果     

Measuring the astrophysical S factors and the cross sections of the p(d, γ)3He reaction in the ultralow energy region using a zirconium deuteride target

The present paper is dedicated to the study of the p(d, γ)³He reaction mechanism with the use of a zirconium deuteride target at proton energies of 11–19 keV. The experiment has been carried out using a proton beam of a high-current pulsed Hall accelerator at the National Research Tomsk Polytechnic University. The dependences of the astrophysical S factor and the effective cross section of the pd reaction on the proton-deuteron collision energy are measured. The results were compared with the available data. The results detailed in the present work agree with the results of an experiment carried out by the LUNA collaboration with the use of a gaseous deuterium target.     

Electronic structure and indirect spin-spin interactions in bournonite (CuPbSbS3) according to antimony nuclear quadrupole resonance

A complex sulfide CuPbSbS₃ (bournonite) has been studied by the nuclear quadrupole resonance on ^121,123Sb. The temperature dependences of the spectroscopic and relaxation parameters in the temperature range of 10–295 K have been obtained. The crystallochemical features of the environment of the two non-equivalent Sb positions in the unit cell have been revealed from the nuclear quadrupole resonance spectra. The existence of the lattice vibrations with the frequency ω = 110 cm^?1 has been demonstrated on the basis of the temperature dependence of the nuclear quadrupole resonance frequencies. Slow beats have been observed on the decay curve of the spin echo signal. Experimental data have been analyzed in order to reveal the existence of the indirect spin-spin interactions involving Sb atoms. The indirect spin-spin coupling constant has been estimated as J = 2.5 ± 0.5 kHz.     

Molecular dynamic simulation of stress evolution analysis in Cu nanowire under ultra-high strain-rate simple tension

This study analyses the behaviour of atoms associated with the propagation of stress waves in Cu nanowires (NWs) during uniaxial tensile deformation using molecular dynamic simulation. Maximum local stress (MLS) and virial stress (VS) methods are adopted to express dynamic stress in ?100? Cu NWs under tension. Simulation results indicated that the VS method enhances the averaging effect at ultra-high strain rates (above 10¹⁰ s^?1), leading to serious undervaluation of yield stress. However, the MLS method provides superior prediction results for the dynamic mechanical responses of NWs under tension at the ultra-high strain rate than does the VS. At a strain rate of 7 × 10¹⁰ s^?1, the double-peak stress phenomenon was observed in the stress–strain curve using the MLS method. The response time (T_rs) to wave propagation, observed at an ultra-high strain rate, is responsible for the accumulation of the elastic stress that is applied at the beginning of tensile loading in a short period, producing the first stress peak. Following plastic deformation, the encounter of the wavefronts with the reduced tensile stress causes the fully constructive interference effect in the middle of the tensile NWs, producing the second stress peak. The results explain the dynamic mechanical behaviour of NWs, contributing to future applications of subsonic manufacturing.     

Application of 57Fe Mössbauer spectroscopy as a tool for mining exploration of bornite (Cu5FeS4) copper ore

Nuclear resonance methods, including Mössbauer spectroscopy,are considered as unique techniques suitable for remote on-line mineralogical analysis. The employment of these methods provides potentially significant commercial benefits for mining industry. As applied to copper sulfide ores, Mössbauer spectroscopy method is suitable for the analysis noted. Bornite (formally Cu₅FeS₄) is a significant part of copper ore and identification of its properties is important for economic exploitation of commercial copper ore deposits. A series of natural bornite samples was studied by ⁵⁷Fe Mössbauer spectroscopy. Two aspects were considered: reexamination of ⁵⁷Fe Mössbauer properties of natural bornite samples and their stability irrespective of origin and potential use of miniaturized Mössbauer spectrometers MIMOS II for in-situ bornite identification. The results obtained show a number of potential benefits of introducing the available portative Mössbauer equipment into the mining industry for express mineralogical analysis. In addition, results of some preliminary ^63,65Cu nuclear quadrupole resonance (NQR) studies of bornite are reported and their merits with Mössbauer techniques for bornite detection discussed.