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971.
Shuang-Jing Zhou Xiao Cheng Chun-Xia Hu Guo-Yong Xu Wen-Jing Xiao Jun Xuan 《中国科学:化学(英文版)》2021,(1):61-65
A formal[4+3]-cycloaddition reaction of ortho-hydroxyphenyl-substituted para-quinone methides(p-QMs)with in-situ generated azaoxyallyl cations is reported.The reaction occurs under very mild reaction conditions(transition-metal free,room temperature,cheap inorganic base)and provides a very efficient route to a series of biologically important 1,4-benzoxazepine derivatives in good to excellent yields. 相似文献
972.
运用半连续反应装置对山西吴家坪煤和四川华蓥山煤中氯在亚临界水条件下的脱除规律及形态变化进行了研究。考察了反应温度和压力对氯脱除率的影响;同时还运用化学提取法对原煤及残渣中氯的形态进行了研究。研究结果表明,随着反应温度的升高,煤中氯的脱除率也增加,在410℃、15MPa、60min、水流量为580mL/h时,吴家坪煤中氯的脱除率为84.6%,华蓥山煤中氯的脱除率为72.4%。吴家坪煤中氯在15MPa时的脱除率最大。华蓥山煤中氯主要以有机氯的形态存在,而吴家坪煤中氯有8%为离子可交换态的无机氯,其余为有机结合的氯;在亚临界水萃取煤的过程中,离子交换态结合的有机氯比共价键结合的有机氯更容易挥发,有机氯要首先转化为无机氯然后再逸出。 相似文献
973.
Xiaochun Li Xiaoxiao Chen Yuanxing Fang Wei Lin Yidong Hou Masakazu Anpo Xianzhi Fu Xinchen Wang 《Chemical science》2022,13(25):7541
Photoelectrochemical (PEC) water splitting is an appealing approach by which to convert solar energy into hydrogen fuel. Polymeric semiconductors have recently attracted intense interest of many scientists for PEC water splitting. The crystallinity of polymer films is regarded as the main factor that determines the conversion efficiency. Herein, potassium poly(heptazine) imide (K-PHI) films with improved crystallinity were in situ prepared on a conductive substrate as a photoanode for solar-driven water splitting. A remarkable photocurrent density of ca. 0.80 mA cm−2 was achieved under air mass 1.5 global illumination without the use of any sacrificial agent, a performance that is ca. 20 times higher than that of the photoanode in an amorphous state, and higher than those of other related polymeric photoanodes. The boosted performance can be attributed to improved charge transfer, which has been investigated using steady state and operando approaches. This work elucidates the pivotal importance of the crystallinity of conjugated polymer semiconductors for PEC water splitting and other advanced photocatalytic applications.Potassium poly(heptazine imide) photoanode is synthesized, and owing to the improved crystallinity, it has presented a remarkable performance for solar-driven water splitting. 相似文献
974.
Nada Basheir Ali Ahmad Faizal Abdull Razis Der Jiun Ooi Kim Wei Chan Norsharina Ismail Jhi Biau Foo 《Molecules (Basel, Switzerland)》2022,27(12)
The way cells communicate is not fully understood. However, it is well-known that extracellular vesicles (EVs) are involved. Researchers initially thought that EVs were used by cells to remove cellular waste. It is now clear that EVs function as signaling molecules released by cells to communicate with one another, carrying a cargo representing the mother cell. Furthermore, these EVs can be found in all biological fluids, making them the perfect non-invasive diagnostic tool, as their cargo causes functional changes in the cells upon receiving, unlike synthetic drug carriers. EVs last longer in circulation and instigate minor immune responses, making them the perfect drug carrier. This review sheds light on the latest development in EVs isolation, characterization and, application as therapeutic cargo, novel drug loading techniques, and diagnostic tools. We also address the advancement in plant-derived EVs, their characteristics, and applications; since plant-derived EVs only recently gained focus, we listed the latest findings. Although there is much more to learn about, EV is a wide field of research; what scientists have discovered so far is fascinating. This paper is suitable for those new to the field seeking to understand EVs and those already familiar with it but wanting to review the latest findings. 相似文献
975.
976.
977.
Ying-Shi Li Bao-Chen Yang Shu-Min Zheng Yong-Xian Cheng Hong-Hua Cui 《Molecules (Basel, Switzerland)》2022,27(12)
Ferulasinkins A–D (1–4), four new norlignans, were isolated from the resins of Ferula sinkiangensis, a medicinal plant of the Apiaceae family. All of them were obtained as racemic mixtures, chiral HPLC was used to produce their (+)- and (−)-antipodes. The structures of these new compounds, including their absolute configurations, were elucidated by spectroscopic and computational methods. This isolation provides new insight into the chemical profiling of F. sinkiangensis resins beyond the well-investigated structure types such as sesquiterpene coumarins and disulfides. Compounds 2a and 3a were found to significantly inhibit the invasion and migration of triple-negative breast cancer (TNBC) cell lines via CCK-8 assay. On the other hand, the wound-healing assay also demonstrated that compounds 4a and 4b could promote the proliferation of human umbilical vein endothelial cells (HUVECs). Notably, the promoting effects of 4a and 4b were observed as more significant versus a positive control using basic fibroblast growth factor (bFGF). 相似文献
978.
Monte Carlo (MC) methods are important computational tools for molecular structure optimizations and predictions. When solvent effects are explicitly considered, MC methods become very expensive due to the large degree of freedom associated with the water molecules and mobile ions. Alternatively implicit-solvent MC can largely reduce the computational cost by applying a mean field approximation to solvent effects and meanwhile maintains the atomic detail of the target molecule. The two most popular implicit-solvent models are the Poisson-Boltzmann (PB) model and the Generalized Born (GB) model in a way such that the GB model is an approximation to the PB model but is much faster in simulation time. In this work, we develop a machine learning-based implicit-solvent Monte Carlo (MLIMC) method by combining the advantages of both implicit solvent models in accuracy and efficiency. Specifically, the MLIMC method uses a fast and accurate PB-based machine learning (PBML) scheme to compute the electrostatic solvation free energy at each step. We validate our MLIMC method by using a benzene-water system and a protein-water system. We show that the proposed MLIMC method has great advantages in speed and accuracy for molecular structure optimization and prediction. 相似文献
979.
980.
基于高次余弦散射分布的空间卫星可见光特性 总被引:6,自引:4,他引:2
基于几何光学和辐射理论,研究了空间卫星的可见光散射特性.空间卫星的背景辐射主要包括太阳的直接辐射和地球及大气的散射辐射,根据目标的结构特性与背景特性建立了空间卫星的几何模型和光照模型.分析目标表面状况,入射到目标表面的光线近似服从高次余弦散射分布,根据能量守恒定理及表面材料的高次余弦散射分布特性建立了目标散射特性的数学模型.通过矢量坐标变换确定太阳、地球、观测卫星在目标本体坐标系下的相对位置关系.根据给定的几何尺寸和表面物性参量仿真获得了目标在探测器入瞳处的能量分布及星等特征,目标本体与太阳帆板在探测器入瞳处的辐照度最大量级均为10-12 W/m2.仿真结果表明太阳帆板在目标特性分析时不可忽略,为空间目标的可见光探测提供参考数据. 相似文献