浅谈"双棱镜干涉实验"的距离参数

针对学生普遍反映双棱镜干涉实验调节难度大的问题,分析了产生问题的原因,对此实验的距离参数(狭缝与双棱镜、测微目镜的距离)进行探索,给出了具体方法。     

固相微萃取-高效液相色谱-荧光检测法测定番茄中的多菌灵和噻菌灵

建立了应用固相微萃取(SPME)-高效液相色谱(HPLC)-荧光检测法测定番茄中多菌灵(MBC)和噻菌灵(TBZ)的分析方法。考察了萃取纤维、萃取时间、萃取温度、解吸时间、解吸液组成、解吸模式、pH值、有机溶剂和离子强度对MBC和TBZ萃取效率的影响,对SPME条件和色谱条件进行了优化。SPME在室温下进行,采用65 μm聚二甲基硅氧烷/二乙烯苯（PDMS/DVB）萃取纤维,萃取溶液中加入100 g/L NaCl,搅拌速度为1100 r/min,萃取时间为50 min。将该法用于番茄中MBC和TBZ的测定,MBC和TBZ的定量线性范围均为0.01~1.0 mg/kg;线性相关系数分别为0.9958和0.9967;检出限分别为0.003和0.001 mg/kg;回收率分别为83.5%和85.6%(n=5),相对标准偏差(RSDs)分别为6.5%和3.8%。该方法操作简单,无需使用有机溶剂,适于分析番茄样品中的MBC和TBZ。     

A 13CO isotopic study on the CO promotion effect in methane dehydroaromatization reaction over a Mo/HMCM-49 catalyst

The promotion effect of CO in methane dehydroaromatization was investigated using 13CO probe molecules. By alternative injection of 13CO to the methane feed,the distribution of 13CxC6-xH6(x=0-3)products changed significantly,confirming the participation of13CO in the reaction network.The addition of 13CO did not change the conversion of CH4 but improved slightly the durability of the methane dehydroaromatization(MDA)reaction,which might be caused by the interaction of the dissociated oxygen species and the ...     

Synthesis and characterization of a novel molecularly imprinted polymer for simultaneous extraction and determination of water-soluble and fat-soluble synthetic colorants in chilli products by solid phase extraction and high performance liquid chromatography

A sorbent was synthesized and investigated for molecularly imprinted solid phase extraction (MISPE). Molecularly imprinted polymers (MIP) were synthesized via precipitation polymerization procedure, where 4-vinyl pyridine (4-VP) was used as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The imprinting effect of the MISPE was evaluated by elution experiments. The resulting MISPE showed high extraction selectivity to water-soluble and fat-soluble synthetic colorants. The determination of multi-residue for three kinds of water-soluble and six kinds of fat-soluble synthetic colorants in chilli products was also investigated by HPLC coupled with MISPE. The mean recoveries calculated by solvent calibration curve for water-soluble and fat-soluble synthetic colorants were from 72.1% to 95.6% for chilli spice and 72.1% to 92.3% for chilli powder. The decision limit (CCα) and the detection capability (CCβ) obtained for water-soluble and fat-soluble synthetic colorants were in the range of 1.2–1.6 and 1.9–2.4 μg kg⁻¹ in chilli spice and chilli powder. The resulting MISPE was successfully used off-line for the determination of nine kinds of synthetic colorants in chilli products.     

Focusing properties of Gaussian beam with mixed screw and conical phase fronts

Vector diffraction theory is employed to investigate the focusing properties of the Gaussian beams with mixed screw and conical phase fronts. Numerical simulations show that the Gaussian beams with screw-conical phase fronts are different from both the ordinary Laguerre-Gaussian beams and the higher-order Bessel beams. Rather than forming the ring-shaped intensity distributions characteristic of optical vortices, focusing the Gaussian beams with screw-conical phase fronts produce non-symmetric spiral intensity distributions at the focal plane. The intensity distribution forms a counter-clockwise non-symmetric screw path around the focus. The rotation of intensity distributions was observed in the focal plane. The gradient force patterns of these beams focused with high NA are also investigated. The results show that the gradient force pattern shape depends principally on parameter topological charge n of the phase distribution. The gradient force pattern expands with increase in the parameter m of the phase distribution. Therefore, one can change the topological charge n or the parameter m of the phase mask to construct the tunable optical trap to meet different requirements. Its potential application might include rotational positioning of particles and accumulation of smaller non-symmetric particles towards the focus.     

Knoevenagel Condensation Catalyzed by 1,1,3,3‐Tetramethylguanidium Lactate

Knoevenagel condensation between malononitrile or ethyl cyanoacetate and carbonyl compounds could be effectively promoted by 1,1,3,3‐tetramethylguanidium lactate, a basic ionic liquid, under mild conditions. Good to high isolated yields could be obtained. The ionic liquid can enhance the reaction rates significantly even though it was used in catalytic amount. The ionic liquid could be prepared simply and reused efficiently.     

Prediction of gaseous products from Dachengzi oil shale pyrolysis through combined kinetic and thermodynamic simulations

Journal of Thermal Analysis and Calorimetry - This paper presents thermodynamic results of Ag–Sn alloys mixing at 1150 °C. The need for binary data on mixing enthalpy ΔH...     

New lanthanide-based complexes constructed from cucurbit[6]uril: Synthesis,structures and properties

Three lanthanide-based complexes, {Gd₂(H₂O)₁₀(CB[6])₂}·CB[6]·6Cl·12H₂O (1), {[Gd₂(H₂O)₈CB[6]₂]·(CuCl₄)·4Cl·46H₂O}_n (2), and {Dy₂(NO₃)₂(H₂O)₁₀(CB[6])}·4NO₃·14H₂O (3) (CB[6] = cucurbit[6]uril), were prepared with cucurbit[6]uril (CB[6]). These complexes were characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR spectroscopy, UV–Vis spectroscopy, thermogravimetric analysis and magnetization measurements. Crystallographic results showed that 1 and 3 are dinuclear and crystallize in the triclinic space group Pī, whereas 2 is a 1-D zigzag supramolecular chain that crystallizes in the monoclinic system in C2/c. The results indicated that temperature has a big effect on the supramolecular assemblies and a different structure inducer also leads to the formation of different coordination polymers. Frequency dependence in the ac susceptibility signals was observed in 3.