Effect of Different Processing Methods on the Chemical Constituents of Scrophulariae Radix as Revealed by 2D NMR-Based Metabolomics

Scrophulariae Radix (SR) is one of the oldest and most frequently used Chinese herbs for oriental medicine in China. Before clinical use, the SR should be processed using different methods after harvest, such as steaming, “sweating”, and traditional fire-drying. In order to investigate the difference in chemical constituents using different processing methods, the two-dimensional (2D) ¹H-¹³C heteronuclear single quantum correlation (¹H-¹³C HSQC)-based metabolomics approach was applied to extensively characterize the difference in the chemical components in the extracts of SR processed using different processing methods. In total, 20 compounds were identified as potential chemical markers that changed significantly with different steaming durations. Seven compounds can be used as potential chemical markers to differentiate processing by sweating, hot-air drying, and steaming for 4 h. These findings could elucidate the change of chemical constituents of the processed SR and provide a guide for the processing. In addition, our protocol may represent a general approach to characterizing chemical compounds of traditional Chinese medicine (TCM) and therefore might be considered as a promising approach to exploring the scientific basis of traditional processing of TCM.     

Torsionally broken symmetry assists infrared excitation of biomimetic charge-coupled nuclear motions in the electronic ground state

The concerted interplay between reactive nuclear and electronic motions in molecules actuates chemistry. Here, we demonstrate that out-of-plane torsional deformation and vibrational excitation of stretching motions in the electronic ground state modulate the charge-density distribution in a donor-bridge-acceptor molecule in solution. The vibrationally-induced change, visualised by transient absorption spectroscopy with a mid-infrared pump and a visible probe, is mechanistically resolved by ab initio molecular dynamics simulations. Mapping the potential energy landscape attributes the observed charge-coupled coherent nuclear motions to the population of the initial segment of a double-bond isomerization channel, also seen in biological molecules. Our results illustrate the pivotal role of pre-twisted molecular geometries in enhancing the transfer of vibrational energy to specific molecular modes, prior to thermal redistribution. This motivates the search for synthetic strategies towards achieving potentially new infrared-mediated chemistry.

Channelling vibrational excitation energy to achieve ground-state charge-transfer (CT)-assisted isomerization in a donor-bridge-acceptor molecule in solution.     

石墨烯裂纹扩展行为研究

基于分子动力学方法对含预制裂纹石墨烯进行扶手椅向拉伸断裂模拟.使用连续介质理论结合分子动力学计算石墨烯能量释放率,确定石墨烯能量释放率GIC为10.25 J/m2;应力强度因子K,c为3.33 MPa√m.进一步对影响石墨烯裂纹扩展速率的因素-初始裂纹长度与加载速率进行讨论.结果表明:裂纹初始长度与加载率会在一定程度上影响石墨烯中裂纹扩展速率.裂纹扩展速率会随着初始裂纹长度的增加而降低;但随着初始裂纹长度的增加,裂纹扩展速率对其敏感度降低.裂纹扩展速率会随着加载率的升高而增大.初始裂纹长度与加载率对裂纹扩展速率的影响有一定的关联性,加载率的升高会降低裂纹扩展速率对初始裂纹长度变化的敏感度.在此基础上确定了石墨烯中裂纹扩展极限速率为8350 m/s.     

实践十号卫星项目——热毛细对流振荡特征的地面研究

上部开口环形液池在水平径向温度梯度作用下会出现内部温度和自由面的振荡,本文研究了二者发生的临界条件.环形液池内柱加热外壁制冷,以0.5℃/min的速率线性升温得到水平径向温差,T型热电偶测量液层内部单点温度,高精度激光位移传感器测量液层自由面某点形变.随两端温差增加,当超过某一临界温度ΔTct时,开始出现振荡.实验结果表明,对同一种硅油,两种振荡的临界条件随液层厚度具有相同的变化趋势.对不同普朗特(Prandtl)数(Pr)的硅油,振荡临界条件临界马兰哥尼数(Macr)随着邦德数(Bo)的增加而变大.本文工作是中国科学院科学先导专项SJ-10返回式科学实验卫星项目-热毛细对流表面波空间实验研究的地面研究结果,该工作为空间实验提供前期的基础科学研究数据和实验保障.     

铌酸锂晶体及其应用概述

铌酸锂晶体历史悠久,物理效应最为齐全,被用于制备声学滤波器、谐振器、延迟线、电光调制器、电光调Q开关、相位调制器等器件,在电子技术、光通信技术、激光技术等领域得到了广泛应用,并且在第五代无线通信技术、微纳光子学、集成光子学及量子光学等近期快速发展的领域中展示了重要的应用前景。本文简要综述了铌酸锂晶体的基本性质、晶体制备以及应用情况,对铌酸锂晶体未来的应用发展进行了简要分析。     

基于Visco-SCRAM模型的侵彻装药点火研究

针对弹体侵彻过程中装药的安全性,基于黏弹性统计裂纹力学(visco-statistical crack mechanics, Visco-SCRAM)模型计算装药整体温升、装药裂纹摩擦生热以及弹体装药与壳体摩擦生热,考察这3种机制对装药温升的贡献以及侵彻装药的点火机制,得到了装药点火对应的弹体侵彻临界初始速度。结果表明：(1)装药与弹体内壁摩擦生热对装药温升有一定贡献,随着弹体初始撞击速度的提高,摩擦生热对温升的贡献逐渐增大;(2)黏性、损伤和绝热体积变化导致的装药整体温升对装药点火的作用有限; (3)裂纹摩擦形成热点是侵彻装药点火的物理机制;(4)采用Visco-SCRAM模型可预测低强度、长脉冲载荷作用下的装药点火响应。

     

高功率盒形窗内次级电子倍增效应

以S波段高功率盒型窗为对象,采用Monte Carlo模拟方法对盒型窗内的次级电子倍增效应进行研究,探索次级电子的倍增规律。模拟得到了盒型窗内TE11模和TM11模共同作用下,两种陶瓷窗片表面次级电子倍增活跃的区域随传输功率的变化特点。在低传输功率下,次级电子仅在未镀膜窗片表面被激励,并以双面倍增的方式在金属法兰与镀膜窗片相对应的区域增长;在较高的传输功率下,窗片表面的次级电子将以单面倍增的方式活跃在窗片表面与波导口相对的区域。传输功率的升高使得镀膜窗片表面的次级电子倍增活跃区域转移到矩形波导窄边对应的区域,并加剧了未镀膜窗片表面的局部倍增效应。     

破片撞击装药点火实验和数值模拟

实验中采用升 降法得到了破片撞击装药点火的临界速度范围,数值模拟中采用节点约束 分离方法、热弹塑性材料本构方程和化学动力学方程描述了炸药的破坏行为和点火反应。实验结果与数值模拟结果吻合较好。研究结果表明,采用节点约束 分离方法、热弹塑性材料本构方程和化学动力学方程可以有效地描述装药在破片撞击作用下的破坏行为和点火反应。     

基于工业CT图像重构的网格模型的保特征简化方法

对基于工业CT图像重构的网格模型进行网格简化时,大多数现有网格模型简化算法会丢失特征,出现网格质量不好的问题。因此提出一种网格模型保特征简化方法,该方法用三角形折叠法对原始模型进行简化,当简化后模型的平均二面角角度误差达到允许误差后,再使用边折叠法对模型进行简化。在三角形折叠法中提出了利用被折叠三角形的法向量、各个顶点的高斯曲率及其在周边三角形上的投影确定该三角形的折叠点,利用局部体积误差与二面角角度误差的无因次化和确定折叠代价的方法;在边折叠法中提出了将二面角角度误差引入到二次误差测度（QEM）法的折叠代价中的改进QEM法。实验结果表明：与其他算法相比,该方法能够生成保特征、高质量、低几何误差的网格模型。