Asymmetric synthesis of chromanone lactones via vinylogous conjugate addition of butenolide to 2-ester chromones

Chiral chromanone lactones are a class of natural products with important biological activity. We report a direct diastereo- and enantioselective vinylogous conjugate addition of butenolide to 2-ester substituted chromones. The transformation proceeded well in the presence of as low as 1 mol% of a chiral N,N′-dioxide/Sc^III complex, 3 Å MS and a catalytic amount of hexafluoroisopropanol (HFIP). The scope of Michael acceptors includes a variety of substituted chromones at different positions, and the desired chromanone lactones upon reduction are afforded in good yield and diastereoselectivity, and excellent enantioselectivity (up to 99% ee). The strategy could be used in the concise synthesis of blennolide C and gonytolide A, C and G.

We report a direct, diastero- and enantioselective vinylogous 1,4-addition of butanolide to 2-ester chromones. A chiral Sc^III complex enabled the reaction to proceed smoothly to give a variety of chraomanone lactones.     

火焰原子吸收光谱法测定高血压患者头发中锌铜钙镁

用火焰原子吸收光谱法测定高血压患者45例及健康对照者34例头发中锌、铜、钙、镁的含量。结果表明,高血压患者头发中锌、铜、钙含量显著低于健康对照组（p〈0．05）,镁含量极显著低于健康对照组,揭示体内锌、铜、钙、镁元素含量与高血压发病存在一定关系。     

Self-organized Criticality in an Earthquake Model on Random Network

A simplified Olami-Feder-Christensen model on a random network has been studied. We propose a new toppling rule — when there is an unstable site toppling, the energy of the site is redistributed to its nearest neighbors randomly not averagely. The simulation results indicate that the model displays self-organized criticality when the system is conservative, and the avalanche size probability distribution of the system obeys finite size scaling. When the system is nonconservative, the model does not display scaling behavior. Simulation results of our model with different nearest neighbors q is also compared, which indicates that the spatial topology does not alter the critical behavior of the system.     

基于永磁体间的磁性负刚度的分析与优化

为了有效地降低磁性负刚度结构的非线性程度,从简单三磁体结构出发,引入新型负刚度结构模型——五磁体对称结构,运用MATLAB建立新型负刚度结构的磁力学模型并应用Ansoft Maxwell进行仿真验证.研究永磁体间的相对位置参数对五磁体对称结构的负刚度曲线走势的影响,在微幅振动下对基于磁引力的负刚度曲线拟合后使用谐波平衡...     

多点侧面泵浦双包层光纤激光器的对称夹层结构

 利用基于亚波长衍射光栅理论的介质-金属-介质的对称夹层结构,对掺杂的双包层光纤进行多点泵浦,根据严格的电磁场衍射理论和光栅方程,分析了多点泵浦时,这种耦合结构的泵浦光泄露的问题,证明了多点泵浦时泵浦光的泄露率仅为15.52%,而对信号光则不存在泄露。这种对称夹层结构可以用于多个大功率激光二极管阵列的多点侧面泵浦双包层掺杂光纤中,以制作各种大功率(数kW级)稀土光纤激光器,其最大耦合效率可以达到80%以上。     

Optimization of Naringenin Nanoparticles to Improve the Antitussive Effects on Post-Infectious Cough

Naringenin (NRG) is a natural compound with several biological activities; however, its bioavailability is limited owing to poor aqueous solubility. In this study, NRG nanoparticles (NPs) were prepared using the wet media milling method. To obtain NRG NPs with a small particle size and high drug-loading content, the preparation conditions, including stirring time, temperature, stirring speed, and milling media amount, were optimized. The NRG (30 mg) and D-α-tocopherol polyethylene glycol succinate (10 mg) were wet-milled in deionized water (2 mL) with 10 g of zirconia beads via stirring at 50 °C for 2 h at a stirring speed of 300 rpm. As a result, the NRG NPs, with sheet-like morphology and a diameter of approximately 182.2 nm, were successfully prepared. The NRG NPs were stable in the gastrointestinal system and were released effectively after entering the blood circulation. In vivo experiments indicated that the NRG NPs have good antitussive effects. The cough inhibition rate after the administration of the NRG NPs was 66.7%, cough frequency was three times lower, and the potential period was 1.8 times longer than that in the blank model group. In addition, the enzyme biomarkers and histological analysis results revealed that the NRG NPs can effectively regulate the inflammatory and oxidative stress response. In conclusion, the NRG NPs exhibited good oral bioavailability and promoted antitussive and anti-inflammatory effects.     

A MXene-derived redox homeostasis regulator perturbs the Nrf2 antioxidant program for reinforced sonodynamic therapy

Ultrasound (US)-mediated sonodynamic therapy (SDT) has emerged as a spatiotemporally controllable therapeutic modality in combating cancer because of its high tissue-penetration depth and minimal invasiveness. However, the elevated nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant program in cancer cells can serve as a chief reactive oxygen species (ROS) detoxification system to alleviate oxidative injury and promote tumorigenesis, and thus greatly antagonize the therapeutic efficacy of ROS-mediated anticancer therapies. Herein, we report that vanadium carbide MXene-derived carbon dots (PMQDs) can act as high-efficacy sonosensitizers to efficiently generate ROS upon US irradiation and simultaneously hinder the Nrf2 antioxidant program for enhanced sonodynamic therapy of cancer. These PMQDs show superior US-triggered ROS generating ability because of their efficient migration/separation of electron–hole pairs and narrow bandgap. Importantly, these PMQDs can serve as efficient redox homeostasis regulators to perturb the Nrf2 antioxidant mechanism and thus reduce its effects on ROS neutralization for enhanced SDT efficacy. Overall, the present study will not only provide a new paradigm to augment SDT by perturbing the Nrf2 antioxidant program, but also give valuable insights into developing high-efficacy MXene-derived nanoagents for cancer therapy.

A redox homeostasis regulator has been developed as a high-efficacy sonosensitizer to efficiently generate reactive oxygen species upon ultrasound irradiation and simultaneously hinder the Nrf2 antioxidant program for enhanced sonodynamic therapy.     

ZnO纳米钉的制备和光学性质研究

通过化学气相沉积(CVD)方法在Si(100)衬底上制备出新型的ZnO纳米钉结构.X射线衍射(XRD)结果表明纳米钉是六角纤锌矿结构.纳米钉顶部对角线在450～750 nm之间,纳米钉长度为几个微米.研究了不同气氛下退火样品的可见发光性质,认为绿光发射来自于导带电子和反位氧中空穴的辐射复合.     

碳辅助金属配合物热解法制备高含量Fe-N4单原子催化剂用于氧还原反应

单原子催化剂凭借其超高的原子利用率及在某些反应中表现出的出色催化效果,被认为是最有前途的电催化剂之一,引起了研究人员的极大热情和兴趣.制备高金属含量的单原子催化剂是基础研究和实际应用的前提和关键.然而,由于原子表面自由能随着尺寸的减小而急剧增加,在制备和催化过程中,单原子催化剂的金属原子很容易聚集成团簇甚至颗粒,因此如...