REE bound polysaccharides in leaves of Dicranopteris dichotoma by MAA

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Acoustic scattering from fluid-filled finite cylindrical shell in water:Ⅱ.Experiment

Acoustic scattering from the submerged fluid-filled finite cylindrical shell insonified by an incident plane wave is studied experimentally and theoretically.A monostic broadband transducer with the sharp directivity is used in the experiment.The broadband LFM signal and the single-frequency narrow pulse are used to measure the backscattering field of the cylindrical shell.The measured results have a good agreement with the theory both in time and frequency domain.The theoretical and experimental results show that the resonances of several additional waves which are caused by the internal fluid are presented in the frequency domain.And a series of ’whispering gallery’ waves produced by the waves reflected back and forth in the internal fluid filled in the cylindrical shell are added.The reason for the clustering of the bowl-shape resonance curves in the frequency-angle spectrum is explained as the superposition of the first several modes of ’whispering gallery’ waves.     

Cu~(2+)-Cu~(2+)离子对的电子顺磁共振谱

本文利用晶场理论中的点电荷-电偶极模型,从“孤立络离子”近似下Cu~(5+)的光学性质和磁学性质的研究出发,探讨了晶体中Cu~(2+)-Cu~(2+)离子间相互作用对电子顺磁共振谱(EPR)的影响。以Cu(detc)_2晶体为例,首次用SCF-d轨道理论,解释了前人没法定量解释的零场分裂现象,建立了考虑Cu~(2+)-Cu~(2+)间相互作用后自旋哈密顿参量和晶格参数间的关系,从而首次从理论上给出了从孤立络离子近似到存在离子间相互作用时晶体的EPR谱的统一解释。计算结果表明:对于Cu(detc)_2,考虑Cu~(2+)-Cu~(2+)对的影响后,g-因子不变(这与实验结果符合),而零场分裂主要是旋轨耦合、晶场对称性以及Cu~(2+)-Cu~(2+)对间交换作用联合作用的结果。并对所得结果进行了讨论。     

Co-Intercalation of Dual Charge Carriers in Metal-Ion-Confining Layered Vanadium Oxide Nanobelts for Aqueous Zinc-Ion Batteries

Vanadium-based oxides with high theoretical specific capacities and open crystal structures are promising cathodes for aqueous zinc-ion batteries (AZIBs). In this work, the confined synthesis can insert metal ions into the interlayer spacing of layered vanadium oxide nanobelts without changing the original morphology. Furthermore, we obtain a series of nanomaterials based on metal-confined nanobelts, and describe the effect of interlayer spacing on the electrochemical performance. The electrochemical properties of the obtained Al_2.65V₆O₁₃ ⋅ 2.07H₂O as cathodes for AZIBs are remarkably improved with a high initial capacity of 571.7 mAh ⋅ g⁻¹ at 1.0 A g⁻¹. Even at a high current density of 5.0 A g⁻¹, the initial capacity can still reach 205.7 mAh g⁻¹, with a high capacity retention of 89.2 % after 2000 cycles. This study demonstrates that nanobelts confined with metal ions can significantly improve energy storage applications, revealing new avenues for enhancing the electrochemical performance of AZIBs.     

超高效液相色谱-四极杆-飞行时间质谱定性研究茶叶籽中的酚类化合物

采用超高效液相色谱(UHPLC)-四极杆-飞行时间质谱(Q-TOF/MS)技术定性分析茶叶籽中的酚类化合物。茶叶籽样品经乙醇水溶液提取后经反相色谱分离,通过Q-TOF/MS进行化合物的鉴定。基于山茶属及相关植物化学组成的文献,建立了一个含有106种酚类化合物的数据库。对UHPLC-Q-TOF/MS采集得到的一级质谱数据进行数据库检索,然后对检索到的化合物色谱峰进行二级质谱扫描,根据得到的碎片离子推断化合物的结构。初步推断出茶叶籽提取物中的24种酚类化合物,包括13种酚酸类、4种儿茶素类和7种黄酮类化合物,并通过与标准品比对,进一步确证了这些化合物。结果表明UHPLC-Q-TOF/MS技术可以用于对茶叶籽中酚类化合物进行快速、准确、可靠的定性分析,促进新化合物的发现与鉴别。     

Regularized Lagrangian duality for linearly constrained quadratic optimization and trust-region problems

In this paper we first establish a Lagrange multiplier condition characterizing a regularized Lagrangian duality for quadratic minimization problems with finitely many linear equality and quadratic inequality constraints, where the linear constraints are not relaxed in the regularized Lagrangian dual. In particular, in the case of a quadratic optimization problem with a single quadratic inequality constraint such as the linearly constrained trust-region problems, we show that the Slater constraint qualification (SCQ) is necessary and sufficient for the regularized Lagrangian duality in the sense that the regularized duality holds for each quadratic objective function over the constraints if and only if (SCQ) holds. A new theorem of the alternative for systems involving both equality constraints and two quadratic inequality constraints plays a key role. We also provide classes of quadratic programs, including a class of CDT-subproblems with linear equality constraints, where (SCQ) ensures regularized Lagrangian duality.     

Nickel‐Catalyzed 1,1‐Alkylboration of Electronically Unbiased Terminal Alkenes

An unprecedented nickel‐catalyzed 1,1‐alkylboration of electronically unbiased alkenes has been developed, providing straightforward access to secondary aliphatic boronic esters from readily available materials under very mild reaction conditions. The regioselectivity of this reaction is governed by a unique pyridyl carboxamide ligated catalyst, rather than the substrates. Moreover, this transformation shows excellent chemo‐ and regio‐selectivity and remarkably good functional‐group tolerance. We also demonstrate that under balloon pressure, ethylene can also be utilized as a substrate. Additionally, competence experiments indicate that selective bond formation is favored at the α‐position of boron and preliminary mechanistic studies indicate that the key step in this three‐component reaction involves a 1,2‐nickel migration.     

含Ni~(2+)离子晶体的光吸收谱分析

本文利用C_i点群对称下的晶场势表达式,推算出C_i对称下的晶场微扰矩阵元;并利用点荷模型对(NH_4)_2Ni(BeF_4)_2·6H_2O晶体的光谱进行计算。计算结果与实验较为符合。对在解释这类物质的光吸收谱分裂方面所流行的观点,即用简化的O_h点群对称晶场上加上自旋—轨道耦合的观点进行了讨论,提出了不同的看法。     

一株α－乙酰乳酸脱羧酶产生菌株的筛选及初步鉴定

α－乙酰乳脱酸羧酶在促进啤酒的风味成熟方面有广阔的应用前景．本文介绍一株纯培养的α－乙酸乳酸脱羧酶产生菌ＡＤ６的分离及筛选过程；并对该菌的特征及部分生理生化指标作了初步描述．