小鼠早期胚胎肢体发育中的视黄酸诱导的视黄酸代谢

给怀孕10 d的小鼠胃灌流视黄酸(100 mgRA/kg体重)6和24 h后,对视黄酸合成酶基因Raldh2和代谢酶基因Cyp26a1,Cyp26b1在胚胎肢体的表达进行了分析.Cyp26a1和Cyp26b1在灌流6 h,表达增加;灌流24 h,表达恢复到正常水平.Raldh2在此时间段表达降低.这些结果提示:在小鼠早期胚胎肢体发育中,存在视黄酸诱导的视黄酸代谢.     

视黄酸合成酶基因Raldh2敲除鼠肢体发育起始的挽救

视黄酸合成酶基因Raldh2敲除鼠胚胎心脏膨大,没有肢体发育的起始.肌细胞增强子基因Mef2C敲除鼠胚胎心脏较小,但肢体的发育起始正常.Raldh2/Mef2C双基因敲除鼠与Raldh2敲除鼠形态相似.Tbx5在Raldh2/Mef2C基因敲除鼠第9天的胚胎表达表明,双基因敲除鼠胚胎没有肢体的发育.这一结果表明Mef2C敲除鼠没有挽救Raldh2敲除鼠肢体发育的起始.     

Nitrogen Adsorption Studies of PAN-Based Activated Carbon Fibers Prepared by Different Activation Methods

Polyacrylonitrile (PAN)-based activated carbon fibers (ACFs) prepared by various activation methods were characterized using low-temperature nitrogen adsorption over a wide relative pressure from 10⁻⁶ to 1. Nitrogen adsorption is a standard tool for determination of porous structure parameters. In the present work, we carried out extensive adsorption studies of a series of PAN-ACFs activated by different methods. It was shown that the high-resolution α_S plot provided valuable information about structural properties of samples under study. The pore size distributions of samples under study were calculated by employing the regularization method according to density functional theory. By these analyses, the pore development and the dominant pores of samples prepared by different methods can be clearly observed. Moreover, the adsorption measurement could provide profound insight into the structural heterogeneity of the ACFs.     

Effect of mobile phase composition, pH and buffer type on the retention of ionizable compounds in reversed-phase liquid chromatography: application to method development

Optimizing separation of ionizable compounds in order to find robust conditions has become an important part of method development in liquid chromatography. This work is an attempt to explain the observed variations of retention of acid and basic compounds with the organic modifier content in the mobile phase, according to various factors: the type of modifier, the type of buffer, the temperature and of course the type of solute. This is done by considering the variation of the so-called chromatographic pKa which refers to the pH measured in the aqueous medium and is determined from retention data. A procedure is described that accurately relates, from nine experiments, retention to solvent composition and pH. The limits of such a procedure are evaluated and two examples of optimized separations of basic compounds are given.     

Morphology, morphology development and mechanical properties of polystyrene/polybutadiene blends

Polystyrene/polybutadiene (PS/PB) blends with different plastic/rubber ratios were prepared by melt mixing. A detailed investigation on phase morphology development of 30/70 wt.% PS/PB blends as a function of processing conditions was quantitatively analyzed. Morphology is developed at the initial stages of mixing. Suitable blending conditions resulting in optimum phase morphology were obtained at 180 °C, 60 rpm and at 8 min mixing time. Phase morphologies of the blends were also studied as a function of composition. Mechanical properties of the blends were measured. Attempts were made to correlate the morphologies with the properties. Parallel-Voids model has been applied to characterize phase morphology of these blends.     

Development of modified force field for cation–amino acid interactions: Ab initio-derived empirical correction terms with comments on cation–π interactions

The modeling of voltage-gated ion-channel proteins is a continuing challenge for force-field calculations because of the diverse range of interactions involved. In particular, current force fields are not parameterized for either ion–amino acid or amino acid–electric field interactions. To address the parameterization of ion–amino acid interactions, we have tested the use of empirical correction terms, derived from ab initio calculations of single amino acids (representing the peptide backbone) interacting with K⁺ ions. Having demonstrated the utility of such an approach, we then extended the application to the amino acid side chains. The calculation of the interaction of K⁺ with serine, cysteine, methionine, lysine, arginine, aspartate, histidine (uncharged), tyrosine, tryptophan, and phenylalanine, both completes the parameterization of the molecular environments contained in the amino acids, and allows specific comment on these ion–functional group interactions. The cation–π interactions were of particular interest, given recent proposals in the literature and the fear that force fields would not be able to treat such interactions. We present a comprehensive comparison of the ab initio (DFT [BLYP], 6-311 G**) and force field (CHARMm22.0) assessments of these interactions. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1515–1525, 1998     

A Fully Synthetic Globo H Carbohydrate Vaccine Induces a Focused Humoral Response in Prostate Cancer Patients: A Proof of Principle

Human trials on the globo H carbohydrate vaccine (see picture, KLH=the carrier protein keyhole limpet hemocyanin) show that it produces strong IgM, and in some cases IgG, responses in patients with progressive and recurrent prostate cancer. Furthermore, these antibodies not only recognize synthetic antigens, but also globo H‐positive tumors in biopsy extracts and tumor tissues.     

天然气水合物开发多物理场特征及耦合渗流研究进展与建议

天然气水合物作为一种非常规的清洁能源, 在全球分布广、资源量大. 自20世纪90年代以来, 加拿大、美国、日本、中国已经先后进行了陆域及海域的水合物试采, 但发现出砂、单井日产气量低、稳产时间短等问题, 试采产量远不能满足商业化开发的需求, 其中核心问题是对水合物开发过程中的相变、多相多组分多场耦合渗流特征的认识不够明晰. 本文根据天然气水合物开发过程中涉及的渗流场、温度场、化学场、力学场等多场耦合特征, 重点综述水合物生成/分解对各物理场主要特征参数的影响, 包括水合物储层的孔隙度、水合物饱和度、渗透率、相对渗透率等基础物性参数及其动态演变, 天然气水合物的导热系数、比热容、热扩散系数以及水合物生成/分解热等热力学参数, 天然气水合物生成、分解动力学特征, 纯水合物以及含水合物沉积物的力学性质等, 最后阐述了天然气水合物开发渗流中的多场耦合关系及相互作用, 提出了今后水合物开发多物理场特征及耦合渗流的科学研究、技术开发的有关建议.      

基于WRF数值模式的SDAE-SVR风速预测模型研究

风速预测是风力预报中的核心与基础, 采用天气研究和预报(Weather Research and Forecasting, WRF)模式进行风力预报往往存在风速预测误差较大的问题. 为了提高风速预测精度, 提出了一种基于深度学习和支持向量回归(Support Vector Regression, SVR)相结合的风速预测模型. 该模型以WRF模式预报输出的多种气象变量为基础, 结合气象自动观测站传感器的实测风速, 引入堆栈降噪自动编码(Stacked De-noising Auto-Encoder, SDAE)深度网络来学习样本数据中隐含的深度特征, 然后将该深度网络最后一层输出的深度特征置入回归器SVR中, 利用SVR良好的回归预测性能对WRF模式预报的未来1h风速进行预测订正. 结果表明: 所建立的SDAE-SVR风速预测模型具有较高的风速预测精度, 在对典型日的WRF模式预报未来1h风速的预测订正中, 其平均百分比误差与均方根误差仅为8.28％与0.8 066 m·     

长三角地区旅游发展效率空间分异及空间自相关研究—基于面板数据的解释

通过对2005~2015年长三角地区26个城市旅游发展效率的DEA测度, 再运用空间自相关及面板数据回归分析, 结果发现: (1)2005~2015年长三角地区城市旅游发展综合效率呈上升趋 势; (2)长三角地区城市旅游效率空间分异为规模效率主导型、纯技术效率主导型和规模技术双作用型, 城市旅游效率具有显著空间自相关性; (3)长三角旅游发展效率影响因素排序为政府宏观调控、经济发展水平及城市居民消费水平, 影响程度在浙、苏、皖具有差异性.