Comparative X-ray photoelectron spectroscopic study on the desulfurization of thiophene by Raney nickel and rapidly quenched skeletal nickel

The desulfurization of thiophene on Raney Ni and rapidly quenched skeletal Ni (RQ Ni) has been studied in ultrahigh vacuum (UHV) by X-ray photoelectron spectroscopy (XPS). The Raney Ni or RQ Ni can be approximated as a hydrogen-preadsorbed polycrystalline Ni-alumina composite. It is found that thiophene molecularly adsorbs on Raney Ni or RQ Ni at 103 K. At 173 K, thiophene on alumina is desorbed, while thiophene in direct contact with the metallic Ni in Raney Ni undergoes C-S bond scission, leading to carbonaceous species most probably in the metallocycle-like configuration and atomic sulfur. On RQ Ni, the temperature for thiophene dissociation is about 100 K higher than that on Raney Ni. The lower reactivity of RQ Ni toward thiophene is tentatively attributed to lattice expansion of Ni crystallites in RQ Ni due to rapid quenching. The existence of alumina and hydrogen may block the further cracking of the metallocycle-like species on Raney Ni and RQ Ni at higher temperatures, which has been the dominant reaction pathway on Ni single crystals. By 473 K, the C 1s peak has disappeared, leaving nickel sulfide on the surface.     

整体柱在线净化-液相色谱-高分辨质谱法快速测定牛奶中15种糖皮质激素

将自制的在线固相萃取柱与液相色谱串联四极杆静电轨道离子阱质谱技术相结合,建立了快速测定牛奶中15种糖皮质激素类药物的新方法.样品采用乙腈均质提取2 min,经自制在线固相萃取小柱富集净化,在Waters CORTECS T3(150 mm ×2.1 mm,5μm)分析柱上实现良好分离,外标法定量.15种目标物质量浓度在...     

Three-dimensional porous photo-thermal fiber felt with salt-resistant property for high efficient solar distillation

The urgent need for fresh water resource is a public issue facing the world. Solar distillation for seawater desalination is a promising freshwater production m...     

壳层厚度对骨架Fe@HZSM-5核壳催化剂费托合成催化性能的影响

在不同的水热合成时间下,以铁铝合金为铁源和铝源,四丙基氢氧化铵为分子筛的模板剂和抽提合金中的铝的碱,一步制得了以骨架铁为核、不同厚度的HZSM-5分子筛为壳的Raney Fe@HZSM-5催化剂.采用元素分析、氮物理吸附、X射线粉末衍射、氨脱附、扫描电子显微镜等手段,考察了水热时间对催化剂基本物化性质的影响.随着水热时...     

Characterization of Volatile Compounds of Rosa roxburghii Tratt by Gas Chromatography-Olfactometry,Quantitative Measurements,Odor Activity Value,and Aroma Intensity

Rosa roxburghii tratt (RRT), widely distributed in the southwest of China, is favored by consumers for its good taste and healthy functions. In this study, thirty-seven compounds of Rosa roxburghii Tratt (RRT) were identified and quantified by gas chromatography–olfactometry (G–O) and gas chromatography–mass spectrometry (GC–MS) analysis. Furthermore, ethyl 2-methylpropanoate, ethyl butanoate, ethyl 2-methylbutyrate, and ethyl hexanoate were present with much higher odor activity values (OAVs) than other compounds. The key notes were confirmed by omission tests. Possible interaction among key notes was investigated through odor intensity determination and sensory analysis. It showed fruity and woody notes had synergistic effects. Full factorial design was used to evaluate the notes contribution to the whole odor. One important finding is the major effect of order interactions, fruity note (X1) and woody note (X4) especially, emphasizing the existence of complex interactions occurring between odor notes. The interaction X1X4 was further investigated. The woody note has a positive effect when the fruity note is also in the mixture but tends to show a negative effect otherwise.     

低浓度含铅细颗粒物暴露大鼠体内生物转运研究

食品接触性塑料制品、可再生资源、汽车尾气中含有低浓度铅.铅等重金属体内蓄积严重影响机体健康,但机体长期暴露于铅环境的代谢依然未知.以低剂量含铅细颗粒物暴露为场景,探讨其在大鼠体内的生物转运及体内分布.通过比较每日吸入染毒(7.05±0.83)μg/m3及经口染毒0.42μg/d,连续染毒28 d.结果显示含铅细颗粒物入...     

Chaos control and synchronization for a special generalized Lorenz canonical system – The SM system

This paper presents some simple feedback control laws to study global stabilization and global synchronization for a special chaotic system described in the generalized Lorenz canonical form (GLCF) when τ = −1 (which, for convenience, we call Shimizu–Morioka system, or simply SM system). For an arbitrarily given equilibrium point, a simple feedback controller is designed to globally, exponentially stabilize the system, and reach globally exponent synchronization for two such systems. Based on the system’s coefficients and the structure of the system, simple feedback control laws and corresponding Lyapunov functions are constructed. Because all conditions are obtained explicitly in terms of algebraic expressions, they are easy to be implemented and applied to real problems. Numerical simulation results are presented to verify the theoretical predictions.     

PERMANENCE AND PERSISTENCE OF TIME VARYING LOTKA-VOLTERRA SYSTEMS

In this article, the permanence and persistence for three classes time varying Lotka-Volterra ecological system are investigated by using Lyapunov stability analysis and constructing the compact set of attraction. Some examples are given to illustrate the theorems.     

ROBUST GLOBAL EXPONENTIAL STABILITY OF UNCERTAIN IMPULSIVE SYSTEMS

By using the quasi-Lyapunov function, some sufficient conditions of global exponential stability for impulsive systems are established, which is the basis for the following discussion. Then, by employing Riccati inequality and Hamilton-Jacobi inequality approach, some sufficient conditions of robust exponential stability for uncertain linear/nonlinear impulsive systems are derived, respectively. Finally, some examples are given to illustrate the applications of the theory.     

复射影空间的拟共形平坦Kaehler完备子流形

研究复射影空间的拟共形平坦Kaehler完备子流形得到局部结构与关于数量曲率的拼挤常数．