UV–visible absorption spectrum determination of optical energy gaps of α and β lithium nitrides

It is well known that a high pressure can induce α–β phase transformation of lithium nitride (Li₃N). However, this work demonstrated that a reverse phase transformation of Li₃N from β to α could occur when it was subjected to heat-treatment at 500 °C in vacuum. Furthermore, the optical properties of α and β lithium nitrides were evaluated by UV–visible spectra. The optical energy gaps (E_g) of α and β lithium nitrides, which were determined from the derivative UV–visible spectra, are 1.81±0.01 and 2.14±0.01 eV, respectively.     

Synthesis, Characterization and Thermal Properties of Energetic Compounds Derived from 3-Amino-4-(tetrazol-5-yl)furazan

Five energetic compounds, 3,3‐bis(tetrazol‐5‐yl)‐4,4‐azofurazan (DTZAF), 3‐nitro‐4‐(tetrazol‐5‐yl)furazan (NTZF), hydrazinium 3‐amino‐4‐(tetrazol‐5‐yl)furazan (HATZF), triaminoguanidinium 3‐amino‐4‐(tetrazol‐ 5‐yl)furazan (TAGATZF) and guanylureaium 3‐amino‐4‐(tetrazol‐5‐yl)furazan (MATZF), were prepared using 3‐amino‐4‐(tetrazol‐5‐yl)furazan (ATZF) as starting material and their structures were characterized by FT‐IR, ¹H NMR, ¹³C NMR and elemental analysis. The properties of NTZF were estimated:density is 1.67 g/cm³, enthalpy of formation +415.41 kJ/mol and detonation velocity 8257.83 m/s. The main thermal properties of four compounds, DTZAF, HATZF, TAGATZF and MATZF, were analyzed by TG and DSC techniques and the results showed that their melting points are 251.9, 159.7, 205.4 and 211.4°C, respectively, and their first decomposition temperatures are 256.7, 258.6, 231.7 and 268.6°C, respectively. The fact that their decomposition temperatures were over 230°C showed that they exhibit better thermal stability.     

Dispersion RAFT polymerization of 4‐vinylpyridine in toluene mediated with the macro‐RAFT agent of polystyrene dithiobenzoate: Effect of the macro‐RAFT agent chain length and growth of the block copolymer nano‐objects

The dispersion reversible addition‐fragmentation chain transfer (RAFT) polymerization of 4‐vinylpyridine in toluene in the presence of the polystyrene dithiobenzoate (PS‐CTA) macro‐RAFT agent with different chain length is discussed. The RAFT polymerization undergoes an initial slow homogeneous polymerization and a subsequent fast heterogeneous one. The RAFT polymerization rate is dependent on the PS‐CTA chain length, and short PS‐CTA generally leads to fast RAFT polymerization. The dispersion RAFT polymerization induces the self‐assembly of the in situ synthesized polystyrene‐b‐poly(4‐vinylpyridine) block copolymer into highly concentrated block copolymer nano‐objects. The PS‐CTA chain length exerts great influence on the particle nucleation and the size and morphology of the block copolymer nano‐objects. It is found, short PS‐CTA leads to fast particle nucleation and tends to produce large‐sized vesicles or large‐compound micelles, and long PS‐CTA leads to formation of small‐sized nanospheres. Comparison between the polymerization‐induced self‐assembly and self‐assembly of block copolymer in the block‐selective solvent is made, and the great difference between the two methods is demonstrated. The present study is anticipated to be useful to reveal the chain extension and the particle growth of block copolymer during the RAFT polymerization under dispersion condition. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Energetics of Carbon deposition on Fe(100) and Fe(110) surfaces and subsurfaces

Spin-polarized density functional theory calculations have been performed to investigate carbon deposition and carbide formation on Fe(100) and Fe(110) at different carbon coverage. On Fe(100) with increasing carbon coverage, the most stable carbon adsorption configuration changes from surface carbon adsorption to surface carbon diffusion into subsurface, and surface carbon clustering is not favored thermodynamically. However, surface carbon clustering is more favored kinetically than carbon diffusion; and carbon diffusion into subsurface and surface carbon clustering become competitive. On Fe(110) with increasing surface carbon coverage, the most stable adsorption configuration changes from surface carbon adsorption to surface carbon diffusion into subsurface, and this process is favored both kinetically and thermodynamically, and surface carbon clustering is neither favored nor competitive. Surface carbon deposition might form on Fe(100), while carbide formation might be found on Fe(110).     

一类由从属关系定义的m-折对称双单叶函数的系数估计及Fekte-Szego不等式

本文研究了一类由从属关系定义的$m$-折对称双单叶函数的系数估计及Fekte-Szego不等式,所得结果改进或推广了已有部分作者的结论.     

A sequential separation strategy for facile isolation and comprehensive analysis of human urine N-glycoproteome

Analytical and Bioanalytical Chemistry - Urine is an attractive and non-invasive alternative source to tissue, blood or other biofluids for biomarker screening in clinical research. In normal human...