Robust method for the analysis of phytochelatins in rice by high‐performance liquid chromatography coupled with electrospray tandem mass spectrometry based on polymeric column materials

A sensitive and robust high‐performance liquid chromatography coupled with electrospray tandem mass spectrometry method for the identification and quantification of glutathione and phytochelatins from rice was developed. Homogenized samples were extracted with water containing 100 mM dithiothreitol, and solid‐phase extraction using polymer anion exchange resin was employed for sample purification. Chromatography was performed on a polymeric column with acetonitrile and water containing 0.1% formic acid as the mobile phase at the flow rate of 300 μL/min. The limit of quantitation was 6–100 nM. This assay showed excellent linearity for both glutathione and phytochelatins over physiological normal ranges, with correlation coefficients (r) > 0.9976. Recoveries for four biothiols were within the range of 76–118%, within relative standard deviations less than 15%. The intraday precision (n = 7) was 2.1–13.3%, and the interday precision over 15 days was 4.3–15.2%. The optimized method was applied to analyze tissue samples from rice grown using nutrient solutions with three different cadmium concentrations (0, 50, and 100 μM). With increasing cadmium concentrations, the content of phytochelatin 2 and phytochelatin 3 in rice roots increased, in contrast to most phytochelatins, and the content of glutathione in rice stems and roots decreased significantly.     

Influence of nano-alumina on curing kinetics and corrosion resistance of alumina based ceramic coatings

With thermal chemical reaction, the nano-alumina ceramic coatings were prepared on A3 steel. Influence of nano-alumina on curing kinetics was investigated by differential scanning calorimetry (DSC) analysis and thermogravimetric analysis (TGA). It was found that all samples show the outstanding heat resistance. However the temperature and the enthalpy of curing decreased with the increase in a nano-alumina content. A model was established to explain the decrease. The physical combination and the decrease in activation energy are the major reason for the decrease. Also electrochemical tests were conducted to investigate the corrosion behavior of the nano-alumina coatings. Corrosion current densities (i _corr) decreased with the increase in the nano-alumina content. This indicated that nano-alumina improved the corrosion resistance of the ceramic coatings. Because the uniformity of ceramic coatings is improved due to the fact that nano-alumina particles fill the pores and spaces of coatings, and nano-alumina particles provide the high physical combination between particles.

     

超静定桁架变形协调方程 的新方法

在三角形桁架变形协调的基础上，提出了建立超静定桁架的变形协调方程的新方法，此法简便易行，更利于数值计算。     

可调谐半导体激光吸收光谱技术的调制参量影响及优化选择

为获得较好的谐波信号,完成不同测量目的,以DFB-760.77nm波长处氧气监测为例,通过改变扫描锯齿信号和调制正弦信号的频率和幅值,讨论了调制参量对二次谐波信号峰-峰值、对称性、谐波信号展宽和信号完整性等判别依据的影响和变化.结果表明:Sinmulink模拟值和实验值相关性较高,当正弦调制信号和锯齿扫描信号频率比值为1 000倍时,可以获得较好的二次谐波信号.该研究为实验系统中调制参量的选取和调制度及系统准确度、稳定性、重复性等性能的优化提供了一定帮助.     

Synthesis and formation mechanism of pinnoite in sulfated-type boron concentrated brine by dilution method

The synthesis of pinnoite (MgB₂O(OH)₆) in boron-containing brine was established with a novel dilution method. Effects of temperature, precipitation time, boron concentration and mass dilution ratio on the formation of pinnoite were investigated. The products obtained were characterized by X-ray diffraction (XRD), Raman, thermogravimetric and differential scanning calorimeter (TG-DSC), and scanning electron microscopy. The transformation mechanism of pinnoite with different dilution ratios was assumed by studying the crystal growth of pinnoite. The results showed that pinnoite was synthesized above 60 °C in the diluted brine. There were two reaction steps – precipitation of amorphous solid and the formation of pinnoite crystals – during the whole reaction process of pinnoite when the dilution ratio is more than 1.0 at 80 °C. While in the 0.5 diluted brine, only one reaction step of pinnoite crystal formation was observed and its transformation mechanism was discussed based on dissociation of polyborates in brine. Besides, the origin of pinnoite mineral deposited on salt lake bottom was proposed.     

Rhodium/zinc co-catalyzed asymmetric ring opening reactions of oxabenzonorbornadienes with carboxylic acids

The asymmetric ring opening reactions of oxabenzonorbornadienes with carboxylic acids are described. By using the complex of [Rh(COD)Cl]₂ and (S,S)-BDPP, with ZnI₂ as the co-catalyst, a range of aromatic acids and alkyl acids were utilized as nucleophiles to afford the corresponding chiral hydronaphthalene products with high enantioselectivities (84–94% ee). Thus, the present methodology has provides an effective synthetic method for the preparation of enantioenriched hydronaphthalenes.     

On toughness and (g, f)-factors in bipartite graphs

Let G be a bipartite graph andg and f be two positive integer-valued functions defined on vertex setV(G) ofG such thatg(x) ≤ f(x) for anyx ? V(G). In this paper, a new isolated toughness ofG is defined and some sufficient conditions related to the new toughness forG to have (g,f )-factors are obtained. Furthermore, these results are proved to be sharp in some sense.