中国大陆西部强震前超低频磁场时空变化特征

对2015年至2019年期间中国大陆西部的磁通门磁力仪秒采样观测资料开展了5—100 s频段的地磁垂直强度极化分析，并运用一些数学方法对分析结果进行了处理。结果显示，极化高值在经向和纬向均无明显的形态和幅值变化，且极化高值与地磁外源场扰动无关。在此基础上筛选出18次极化高值异常事件，利用插值方法得到了极化高值异常的空间分布图，并分析了18次高值异常与中国大陆西部及周边15次强震的时空关系。分析结果表明：地磁场出现多台同步极化高值现象后的半年内，高值区可能发生M6.0以上强震；高值现象出现后，多个高值区均有可能发生强震；后续强震的震级与高值区面积呈正相关。     

清管载荷作用下输气管道安全落差研究

山地天然气管道局部落差和坡度大,在清管过程中易在清管器冲击载荷作用下发生屈曲和应力超限。基于有限元方法研究了考虑管-土耦合作用的大落差管段清管过程非线性动力学特征,分析了清管器运行速度、管道坡度、清管器-管内壁间摩擦系数对管道受力和位移的影响,得到了不同坡度、摩擦系数条件下极限清管运行速度和最大高程差。结果表明:清管器运行速度、管道坡度的增加会引起管道应力、位移的增加,运行速度的影响效果更为显著;随着清管器-管内壁间摩擦系数的增加,清管冲击载荷先减小后增加;针对Φ813mm×11mm的X70输气管道,在管道坡度为30°~70°、落差不超过340m~691m范围内的清管作业是安全的。     

Surface Modulation of Iron-doped MoS2 Nanosheets by Phytic Acid for Enhanced Water Oxidation

Surface modulation and heteroatom doping are important approaches for boosting the electrocatalytic performances of MoS₂ nanosheets. As a molecular electrocatalyst, the natural organic phytic acid (PA) offer attractive intermediate for oxygen evolution reaction (OER). Here, a surface modulation strategy is demonstrated through the decoration of PA onto the basal plane of iron (Fe)-doped MoS₂ nanosheets supported on nickel foam (NF) for boosted OER activity. Experimental results indicate that the PA modification and Fe doping could effectively boost the charge transfer and mass transport during the OER process. Specially, PA2-Fe−MoS₂ grown on NF (PA2-Fe−MoS₂/NF) exhibits excellent OER activity (218 mV@20 mA cm⁻²) and durability, even superior to RuO₂ and many other previously reported OER catalysts. This natural organic molecule modification provides a facile strategy to designing low-cost and efficient electrocatalytic materials.     

Solubility and Mixing Thermodynamic Properties of Capecitabine in Five Acetic Acid Esters at Various Temperatures

Russian Journal of Physical Chemistry A - In pharmaceutical industry, capecitabine is often purified by crystallization from acetic esters. In this work, by using laser dynamic isothermal method,...     

Hofmeister Effect on Thermo-responsive Poly(N-isopropylacrylamide)Hydrogels Grafted on Macroporous Poly(vinyl alcohol) Formaldehyde Sponges

In this work,the Hofmeister effects of nine kinds of anions at different concentrations on the lower critical solution temperature(LCST)of the macroporous thermo-responsive poly(N-isopropylacrylamide)grafted poly(vinyl alcohol)formaldehyde(PVF-g-PNIPAM)hydrogels are investigated with differential scanning calorimetry(DSC).Four kinds of anions with strong hydration,including CO3^2–,SO4^2–,S2 O3^2–,and F^–,and four kinds of anions with weak hydration,including Br^–,NO3^–,I^–,and ClO4^–,and Cl^–as a medium anion are systematically studied and found to demonstrate the effects of the residual hydroxyl groups and network structure of PVF on the LCST values of PVF-g-PNIPAM hydrogels in comparison with that of neat PNIPAM.On the one hand,the existence of hydroxyl groups on PVF backbone promotes the solubility of grafted PNIPAM due to their hydrophilicity and hydrogen-bond interactions with water.On the other hand,the network structure of as-prepared samples restricts free movements of grafted PNIPAM chains,which results in the increase of LCST values.In addition,the difference of grafting percentage also influences the variation of LCST values of PVF-g-PNIPAM hydrogels under salt concentration.     

超导薄膜磁场穿透深度的双线圈互感测量

磁场穿透深度是联系超导体宏观电动力学与微观机制的重要物理量,其精确测量对于研究超导机理以及探索超导应用具有重要意义.在众多的磁场穿透深度测量方法中,双线圈互感法具有测量精度高、技术相对成熟、对样品没有破坏等优点,可被用于细致地研究超导薄膜的磁场穿透深度对温度、掺杂、外延应力等参量的依赖关系.本文首先简要介绍了双线圈互感法的基本原理,指出该方法的测量精度主要受系统几何参数及薄膜边缘漏磁的影响;之后对自主设计搭建的透射型双线圈互感装置进行了系统的校验,并详细说明了其测量精度:对于厚度为100 nm,穿透深度为150 nm的典型薄膜样品,穿透深度绝对值的测量误差小于10%;最后通过测量NbN超导薄膜的磁场穿透深度进一步检验了装置的精度,分析表明穿透深度的测量值与文献报道结果符合.     

Hierarchical Porous NiCo2O4 Microboxes Constructed by Low-Dimensional Substructures for Electrochemical Supercapacitor

The design and synthesis of new materials/structures for high-performance electrochemical capacitors (ECs) is an ongoing challenge. Herein, a hierarchical porous NiCo₂O₄ microbox superstructure made of low-dimensional substructures was reported. The as-prepared NiCo₂O₄ microboxes are constructed by 2D nanosheets building units, which are futher woven by 0D nanoparticles and 1D nanowires. Such microbox superstructures combine the merits of all material dimensions in electrochemical capacitors, such as high porosity, sufficient active sites, and fast mass and charge transport. Benefiting from the structural advantages, the resultant NiCo₂O₄ microbox electrode exhibits ultra-high capacitor performance, i.e., the initial capacitance of 1820 F · g^–1 and 96.6 % capacitance retention after 4000 cycles at 5 A · g^–1.     

可见光激发醛还原Minisci反应构筑功能化氮杂环化合物

众所周知,氮杂环类化合物是许多药物、天然产物以及有机光电材料的核心骨架,研究氮杂环类化合物的官能团化反应对化工、医药及材料等领域的发展具有重要意义.鉴于其独特的生理活性和功能,开发新型高效的氮杂环合成策略,构建结构多样的含氮杂环一直是合成化学家追求的目标[1].Minisci反应,即含氮杂环的自由基加成反应,于20世纪60年代被发现.约半个世纪以来,该反应得到了广泛的研究,为构建功能化氮杂芳烃提供了一条重要路径.尽管如此,该反应仍然存在一些问题,比如通常要使用过量的强氧化剂来实现自由基的形成.另外,相比被广泛报道的Minisci烷基化、芳基化和酰基化反应,Minisci苄基化反应鲜有报道,这可能是因为在较高温度的强氧化条件下,苄基自由基很容易被氧化而不能参与反应.在已往报道中,醛参与的Minisci反应主要集中在加热条件下过量氧化剂促进的酰基化和脱羰烷基反应.     

Structural modulation induced by cobalt-based ionic liquids for enhanced thermoelectric transport in PEDOT:PSS

Poly(3,4ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been intensively studied for its thermoelectric applications. Structural modulation to improve crystalline ordering, chain conformation and film morphology is a promising way to decouple the trade-off between conductivity and Seebeck coefficient and thus improve the thermoelectric power factor. Post treatment with ionic liquid ([CoCl₂ ⋅ 6H₂O]:[ChCl]) bearing cobalt-containing anions resulted in a remarkable enhancement of the power factor to 76.8 μW m⁻¹ K⁻². This IL combines the influence of a high-boiling polar organic solvent and diffusing ions. A high σ mainly resulted from the efficient removal of PSS chains, ordering of the structure and delocalization of bipoloran-dominant transport after conformational change. The increase in S was not due to dedoping of PEDOT chains, but rather the sharp feature of the density of states at the Fermi level induced by ion-exchange with unconventional anions.