微波作用下卤素交换氟化制备氟代苯甲醛及二苯甲酮类化合物

在微波作用下,采用高效催化剂体系,于中等极性非质子溶剂中经卤素交换氟化高效制备了系列含氟芳香醛(酮)类化合物,产品收率53·3%~92·6%,反应时间较常规加热最多可缩短80%以上。采用中等极性反应溶剂,还可突出表现出微波对反应促进的“非热效应”,从而大大拓宽了氟化反应溶剂的选择范围。     

(S)-2-氨基-1,1-二苯基-1-丙醇的合成和外消旋Droxidopa前体的拆分

(S)-2-氨基-1,1-二苯基-1-丙醇是一种合成多种手性助剂的重要中间体,也用于外消旋屈昔多巴前体化合物的拆分。从价廉易得的L-丙氨酸出发,通过四步反应制得,总收率55.6%L-丙氨酸经甲酯化,苄氧羰基保护制得的L-2-苄羰基氨基丙酸甲酯与苯基溴化镁反应制得(S)-2-苄氧羰基氨基-1,1-二苯基-1-丙醇。是在5%Pd/C催化加氢下脱除苄氧羰基得到标题化合物。该制备方法涉及的中间体及目标化合物易于纯化,总收率高且重现性好。我们用制得的氨基醇能成功地拆分外消旋苏式屈昔多巴前体化合物3-3,4-二苄氧苯基)-N-苄氧羰基丙氨酸。     

Plasma assisted synthesis of LiNi0.6Co0.2Mn0.2O2 cathode materials with good cyclic stability at subzero temperatures

Layered Ni-rich cathode materials,LiNi_0.6Co_0.2Mn_0.2O₂(NCM622),are synthesized via solid reaction assisted with a plasma milling pretreatment,which is resulted in lowering sintering temperatures for solid precursors.The plasma milling pretreated NCM622 cathode material sintered at 780℃(named as PM-780)demonstrates good cycling stability at both room and subzero temperatures.Specifically,the PM-780 cathode delivers an initial discharge capacity of 171.2 mAh g^-1 and a high capacity retention of 99.7%after 300 cycles with current rate of 90 mA g^-1 at 30℃,while stable capacities of 120.3 and 94.0 m Ah g^-1 can be remained at-10℃and-20℃in propylene carbonate contained electrolyte,respectively.In-situ XRD together with XPS and SEM reveal that the NCM622 cycled at-10℃presented better structural stability and more intact interface than that of cathodes cycled at 30℃.It is also found that subzero temperatures only limit the discharge potential of NCM622 without destroying its structure during cycling since it still exhibits high discharge capacity at 30℃after cycled at subzero temperatures.This work may expand the knowledge about the low-temperature characteristics of layered cathode materials for Li-ion batteries and lay the foundation for its further applications.     

带有双X型铁心框架的超导MRI磁体的设计

文中对带有双X型铁心框架的MR I用高温和低温超导磁体的设计进行了介绍,包括项目的市场需求、磁体的基本参数和系统热负荷的预设计结果等。     

基于小波包分析的心磁信号消噪

心磁图(Magnetocardiography)是一种无创性记录和分析心脏电磁场的方法.由于心磁场强度极其弱小,必须使用超导量子干涉仪(SQUID)才能检测,其中心磁信号消噪处理十分重要.本文对心磁测量中的消噪进行了研究,在小波分析的基础上,提出使用小波包分析方法消噪,通过实验发现小波包分析消噪能获得很好的效果.     

Comparative Phosphoproteomic Analysis of Sporulated Oocysts and Tachyzoites of Toxoplasma gondii Reveals Stage-Specific Patterns

Toxoplasma gondii is an obligate intracellular protozoan of severe threat to humans and livestock, whose life history harbors both gamic and apogamic stages. Chinese 1 (ToxoDB#9) was a preponderant genotype epidemic in food-derived animals and humans in China, with a different pathogenesis from the strains from the other nations of the world. Posttranslational modifications (PTMs) of proteins were critical mediators of the biology, developmental transforms, and pathogenesis of protozoan parasites. The phosphoprotein profiling and the difference between the developmental phases of T. gondii, contributing to development and infectivity, remain unknown. A quantitative phosphoproteomic approach using IBT integrated with TiO₂ affinity chromatography was applied to identify and analyze the difference in the phosphoproteomes between the sporulated oocysts and the tachyzoites of the virulent ToxoDB#9 (PYS) strain of T. gondii. A total of 4058 differential phosphopeptides, consisting of 2597 upregulated and 1461 downregulated phosphopeptides, were characterized between sporulated the oocysts and tachyzoites. Twenty-one motifs extracted from the upregulated phosphopeptides contained 19 serine motifs and 2 threonine motifs (GxxTP and TP), whereas 16 motifs identified from downregulated phosphopeptides included 13 serine motifs and 3 threonine motifs (KxxT, RxxT, and TP). Beyond the traditional kinases, some infrequent classes of kinases, including Ab1, EGFR, INSR, Jak, Src and Syk, were found to be corresponding to motifs from the upregulated and downregulated phosphopeptides. Remarkable functional properties of the differentially expressed phosphoproteins were discovered by GO analysis, KEGG pathway analysis, and STRING analysis. S8GFS8 (DNMT1-RFD domain-containing protein) and S8F5G5 (Histone kinase SNF1) were the two most connected peptides in the kinase-associated network. Out of these, phosphorylated modifications in histone kinase SNF1 have functioned in mitosis and interphase of T. gondii, as well as in the regulation of gene expression relevant to differentiation. Our study discovered a remarkable difference in the abundance of phosphopeptides between the sporulated oocysts and tachyzoites of the virulent ToxoDB#9 (PYS) strain of T. gondii, which may provide a new resource for understanding stage-specific differences in PTMs and may enhance the illustration of the regulatory mechanisms contributing to the development and infectivity of T. gondii.     

p-Adic函数空间上Hardy型算子的多线性交换子估计

在p-adic域上研究分数次Hardy型算子与CMO(Qnp)函数生成的多线性交换子,建立了交换子在Lebesgue空间和Herz空间上的有界性.对Hardy算子的多线性交换子也得到了相应的结果.     

Development of Optogenetic Dual-Switch System for Rewiring Metabolic Flux for Polyhydroxybutyrate Production

Several strategies, including inducer addition and biosensor use, have been developed for dynamical regulation. However, the toxicity, cost, and inflexibility of existing strategies have created a demand for superior technology. In this study, we designed an optogenetic dual-switch system and applied it to increase polyhydroxybutyrate (PHB) production. First, an optimized chromatic acclimation sensor/regulator (RBS10–CcaS#10–CcaR) system (comprising an optimized ribosomal binding site (RBS), light sensory protein CcaS, and response regulator CcaR) was selected for a wide sensing range of approximately 10-fold between green-light activation and red-light repression. The RBS10–CcaS#10–CcaR system was combined with a blue light-activated YF1–FixJ–PhlF system (containing histidine kinase YF1, response regulator FixJ, and repressor PhlF) engineered with reduced crosstalk. Finally, the optogenetic dual-switch system was used to rewire the metabolic flux for PHB production by regulating the sequences and intervals of the citrate synthase gene (gltA) and PHB synthesis gene (phbCAB) expression. Consequently, the strain RBS34, which has high gltA expression and a time lag of 3 h, achieved the highest PHB content of 16.6 wt%, which was approximately 3-fold that of F34 (expressed at 0 h). The results indicate that the optogenetic dual-switch system was verified as a practical and convenient tool for increasing PHB production.     

Dimerization of Acetylene to Monovinylacetylene (MVA) by Bimetallic Zr/Cu Catalyst in Nieuwland Catalytic System

Nieuwland catalyst is a key step in the dimerization of acetylene. Various zirconium metal additives incorporating Nieuwland catalysts were prepared, and their catalytic performances were assessed in acetylene dimerization. Different characterization techniques (i.e., thermogravimetric analysis, temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen ion concentration measurement and transmission electron microscopy) were employed in this study. The best catalytic performance was obtained over zirconium-acetylacetonate-incorporated Nieuwland catalysts, with an acetylene conversion of 53.3% and a monovinylacetylene selectivity of 87.4%. Based on these results, the zirconium acetylacetonate additive could reduce the types of transition state complexes, and it could also change the morphology of the catalyst. In addition, the additives could significantly inhibit the occurrence of trimerization products and polymers. Hence, the conversion of acetylene, monovinylacetylene selectivity, and stability of the Nieuwland catalysts were enhanced.     

Drop-Activation:Implicit Parameter Reduction and Harmonious Regularization

Overfitting frequently occurs in deep learning.In this paper,we propose a novel regu-larization method called drop-activation to reduce overfitting and improve ...