A type of spectrophotometer with both SCI and SCE measurement structures

In order to measure the color of different samples with different surface texture, multiple measurement and observation conditions are needed from the instrument. Thus, both SCI (specular component included) and SCE (specular component excluded) measurement conditions are included in most color measuring instruments today. In current design, a light trap is established in the integrating sphere, and the instrument uses mechanical control to switch between SCI and SCE measurement modes. However, establishing a light trap inside the integrating sphere will affect the SCI and SCE measurement results. This article discusses the problems in current design, proposes a dual light source structure that includes both SCI and SCE measurement conditions, and then evaluates the structure with experiments. The experiment results show that the improved structure is more suitable for color measuring instruments with both SCI and SCE modes, and it has high practical value.     

Catalytic enantioselective synthesis of optically active α-hydroxyl-β,γ-unsaturated acid esters as novel side chains of cerebrosides

Six optically active α-hydroxyl-β,γ-unsaturated acid esters 1a to 1f were synthesised, and they are significant moieties of the cerebrosides. The chiral intermediate alkynol 4 prepared by catalytic asymmetric addition had 99% ee, and which was converted into the target compounds 1a to 1f with high enantiomeric purity.     

1410 nm波段分布式光纤拉曼增益放大器的研究

讨论了分布式光纤拉曼增益放大器的工作原理,采用1320nm固体激光器作为抽运源,获得了1410nm波段附近的光放大,在单模GI光纤长度为23km时,初步研究了拉曼放大器增益与光纤作用长度的关系,抽运脉冲峰值功率分别为50W、30W时,光纤的有效作用长度分别为15．5km和10.5km;研究了在不同的光纤有效作用长度时,拉曼放大器增益与抽运功率的关系;从光纤拉曼光谱图估算了光纤拉曼放大器的光谱宽度为50nm或250cm^-1。     

Detection of systemic pesticide residues in tea products at trace level based on SERS and verified by GC–MS

Analytical and Bioanalytical Chemistry - Surface-enhanced Raman spectroscopy (SERS) has the potential to detect pesticide residues in agricultural products. However, some systemic pesticides, such...     

Enhancing light extraction from tapered internal reflection microstructure

The internal transmittance characteristics of the taper surface microstructure grating with the feature size in a large dimension range from subwavelength nanostructure to microstructure are investigated to improve the light extraction efficiency of light emitting diodes. It is found that subwavelength taper nanostructure can not overcome the total internal reflection, but it is interesting that the taper microstructure can effectively surmount the total internal reflection at a larger emitted angle over the critical angle also with higher transmittance. Besides, the emission characteristics of light intensity for subwavelength nano-grating and taper micro-grating are demonstrated. Also, the simple approaches of the scalar diffraction theory and the effective medium method can accurately analyze respectively the taper microstructure and subwavelength nanostructure grating. It is expected that the taper microstructure could be integrated into light emitting diodes to tremendously enhance the emission efficiency.     

The use of Raman spectroscopy in food processes: A review

Raman spectroscopy is a novel method of food analysis and inspection. It is highly accurate, quick, and noninvasive. The investigation and monitoring of food processing is important because most of the foods humans eat today are processed in various ways. In this article, the use of Raman spectroscopy in food processes, such as fermentation, cooking, processed food manufacturing, and so on, are explored. The characteristics and difficulties of the Raman inspection of these processes are also discussed. According to the various research reports, Raman spectroscopy is a very powerful tool for monitoring these food processes in lab environments and is likely to see usage in situ in the future.     

Temperature-insensitive 2-D tilt sensor by incorporating fiber Bragg gratings with a hybrid pendulum

A novel two-dimensional (2-D) tilt sensor is demonstrated by incorporating only two fiber Bragg gratings (FBGs) with a hybrid pendulum transducer. The pendulum transducer is specially designed with hollow half at the upper side and solid half at the lower side. Two FBGs were attached on the surface separated by one fourth of the circumference of the rod of pendulum and across the interface of its hollow and solid parts. Reflection peaks of FBGs split by the applied tilt angle. 2-D tilt angle can be determined by monitoring the wavelength separations of the split peak in two FBGs, which is inherently insensitive to temperature. In the experiment, a sensitivity of 0.054 nm/° over a wide range of 20º has been achieved, with the accuracy of 0.27°.     

Efficient soluble polymer-supported tartrate/Ti catalyst for asymmetric oxidation of prochiral sulfides

A group of soluble polymer-supported chiral tartrate ligands was prepared by liquid-phase synthesis with ligand diversity strategy. Moderate to excellent chemical yields and enantiomeric excesses were obtained by using soluble polymer-supported tartrate ester in asymmetric oxidation of prochiral sulfides using Ti(O-i-Pr)₄/cumyl hydroperoxide, and the workup was greatly simplified. The influence of substituent in chiral tartrate ligands on the enantioselectivities of the reaction was disclosed.     

锰(Ⅲ)或铈(Ⅳ)引发下β-二羰基化合物的芳基化反应(Ⅱ)

在Mn(OAc)_3-H_3PO_4作用下,乙酰丙酮和稠环芳烃发生反应,生成3-芳基-2,4-戊二酮。反应可能通过·CH(COCH_3)_2自由基进行的。(NH_4)_2Ce(NO_3)_6也能引起这种反应。乙酰乙酰胺及其N-甲基衍生物在Mn(OAc)_3作用下,也能发生芳基化反应。     

在三乙酸锰引发下芳烃与β-二羰基化合物的反应

在三乙酸锰和磷酸作用下,芳烃和乙酰乙酸乙酯反应,生成芳基乙酰乙酸乙酯和亚芳基二乙酰乙酸乙酯。反应是通过生成CH_3COCHCO_2C_2H_5自由基进行的。丙二酸二乙酯和芳烃在三乙酸锰和磷酸作用下也能发生同样的反应。