7502B光电直读光谱仪计算机升级

对国产７５０２Ｂ型ＩＣＰ光电直读光谱光谱仪的计算机控制系统的软硬件结构及其基本运行原理进行了分析，叙述了将其原有主控制计算机从长城０５２０ＣＨ－Ⅱ型微机升级为ＩＢＭＰＣ兼容奔腾机所存在的软件，硬件方面的问题及其解决办法。     

基于最小可分辨对比度的CCD成像系统最佳角放大率研究

光电成像系统存在一个最佳角放大率,使人眼与成像系统达到最佳匹配状态,系统获得最佳性能.基于MRC物理意义,提出MRC信道宽度CCD成像系统综合性能评价方法,通过实际CCD成像系统的观察实验确定了评价模型的表达式,分析了各种系统参数变化对该方法的影响.结果表明,利用MRC信道宽度评价方法描述的最佳角放大率变化与实际情况一致.在最佳角放大率情况下,系统与人眼视觉得到最佳匹配.     

NMR Backbone Assignment of Large Proteins by Using 13Cα‐Only Triple‐Resonance Experiments

Nuclear magnetic resonance (NMR) is a powerful tool to interrogate protein structure and dynamics residue by residue. However, the prerequisite chemical‐shift assignment remains a bottleneck for large proteins due to the fast relaxation and the frequency degeneracy of the ¹³C_α nuclei. Herein, we present a covariance NMR strategy to assign the backbone chemical shifts by using only HN(CO)CA and HNCA spectra that has a high sensitivity even for large proteins. By using the peak linear correlation coefficient (LCC), which is a sensitive probe even for tiny chemical‐shift displacements, we correctly identify the fidelity of approximately 92 % cross‐peaks in the covariance spectrum, which is thus a significant improvement on the approach developed by Snyder and Brüschweiler (66 %) and the use of spectral derivatives (50 %). Thus, we calculate the 4D covariance spectrum from HN(CO)CA and HNCA experiments, in which cross‐peaks with LCCs above a universal threshold are considered as true correlations. This 4D covariance spectrum enables the sequential assignment of a 42 kDa maltose binding protein (MBP), in which about 95 % residues are successfully assigned with a high accuracy of 98 %. Our LCC approach, therefore, paves the way for a residue‐by‐residue study of the backbone structure and dynamics of large proteins.     

Optical Angle Barcodes Enabled by a Pixelated Metasurface for Absolute Micro-Angle Measurement

Efficient and ultra-sensitive measurements of micro-angle are critical technological requirements in various fields. Traditional measurement approaches have disadvantages in terms of accuracy and system complexity. Here, a micro-angle measurement scheme based on the pixelated metasurface is reported. By utilizing the interaction between a C-band optical frequency comb (OFC) laser source and the plasmonic metasurface, precise angle encoding is achieved, enabling each meta-pixel within the pixelated metasurface to exhibit ultra-sensitive responses to angular changes. Experimental results demonstrate a resolution as low as 2.8 μrad for angle sensing. Furthermore, by controlling the dimensions of the meta-atom structural dimensions and designing specific combinations of meta-pixels, the unique angle response of individual pixels is manipulated, effectively creating an angle barcode. This technique allows for highly efficient acquisition of angle information, and based on this, it demonstrates absolute angle measurement with an average error at 7 μrad. The robustness and stability of the proposed scheme is also evaluated.     

Design and performance simulation of a molecular Doppler wind lidar

A mobile molecular Doppler wind lidar at an eye-safe wavelength of 355 nm based on double-edge technique is being built in Hefei （China） for wind measurement from 10-to 40-km altitude. The structure of this lidar system is described. A triple Fabry-Perot etalon is employed as a frequency discriminator whose parameters are optimized. The receiver system is designed to achieve compactness and stability by putting in a standard 19-inch socket bench. Simulation results show that within the wind speed dynamic range of ±100 m/s, the horizontal wind errors due to noise are less than 1 m/s bdow 20-km altitude for 100-m vertical resolution, and less than 5.5 m/s from 20 km up to 40 km for 500-m vertical resolution with 400-mJ laser energy, 30-min temporal resolution, and a 45-cm aperture telescooe.     

Synthesis of ZnO films in different solvents and their photocatalytic activities

ZnO thin films have been successfully synthesized via the chemical bath deposition (CBD) method without using any catalysts or templates. The effects of solvents (such as water, ethanol and n‐propanol) on structure and morphology of ZnO thin films have been studied. XRD analysis showed that all ZnO thin films with wurtzite crystal structure were obtained via various solvents. SEM images showed that ZnO thin films prepared in different solvents have different sizes and morphologies. TEM images showed that crystalline ZnO samples prepared in different solvents have different growth habits. Photoluminescence and photocatalysis properties have been investigated at room temperature. ZnO thin films prepared in water showed superior photocatalytic activity in the degradation of rhodamine B (RhB) compared to other samples.     

Extraction of Pectin from Satsuma Mandarin Peel: A Comparison of High Hydrostatic Pressure and Conventional Extractions in Different Acids

Satsuma mandarin peel pectin was extracted by high hydrostatic pressure-assisted citric acid (HHPCP) or hydrochloric acid (HHPHP), and the physiochemical, structural, rheological and emulsifying characteristics were compared to those from conventional citric acid (CCP) and hydrochloric acid (CHP). Results showed that HHP and citric acid could both increase the pectin yield, and HHPCP had the highest yield (18.99%). Structural characterization, including NMR and FTIR, demonstrated that HHPHP showed higher Mw than the other pectins. The viscosity of the pectin treated with HHP was higher than that obtained with the conventional method, with HHPHP exhibiting significantly higher viscosity. Interestingly, all the pectin emulsions showed small particle mean diameters (D_4,3 being 0.2–1.3 μm) and extremely good emulsifying stability with centrifugation and 30-day storage assays, all being 100%. Satsuma mandarin peel could become a highly promising pectin source with good emulsifying properties, and HHP-assisted acid could be a more efficient method for pectin extraction.     

Effect of Degree of Deacetylation of Chitosan/Chitin on Human Neural Stem Cell Culture

Stem cell therapy and research for neural diseases depends on reliable reproduction of neural stem cells. Chitosan-based materials have been proposed as a substrate for culturing human neural stem cells (hNSCs) in the pursuit of clinically compatible culture conditions that are chemically defined and compliant with good manufacturing practices. The physical and biochemical properties of chitosan and chitin are strongly regulated by the degree of deacetylation (DD). However, the effect of DD on hNSC behavior has not been systematically investigated. In this study, films with DD ranging from 93% to 14% are fabricated with chitosan and chitin. Under xeno-free conditions, hNSCs proliferate preferentially on films with a higher DD, exhibiting adherent morphology and retaining multipotency. Lowering the DD leads to formation of neural stem cell spheroids due to unsteady adhesion. The neural spheroids present NSC multipotency protein expression reduction and cytoplasmic translocation. This study provides an insight into the influence of the DD on hNSCs behavior and may serve as a guideline for hNSC research using chitosan-based biomaterials. It demonstrates the capability of controlling hNSC fate by simply tailoring the DD of chitosan.