相对运动完整系统Appell方程Mei对称性的共形不变性与守恒量

研究相对运动完整系统Appell方程Mei对称性的共形不变性与守恒量. 引入无限小单参数变换群及其生成元向量, 给出相对运动完整系统Appell方程的Mei对称性和共形不变性的定义, 导出系统Mei对称性的共形不变性确定方程, 重点讨论系统共形不变性和Mei对称性的关系, 然后借助规范函数满足的结构方程导出系统Mei对称性导致的Mei守恒量表达式, 最后举例说明结果的应用.     

长程铯里德堡分子的势能曲线

本文介绍了半经典近似下的低能电子-原子散射理论, 引入贋势描述里德堡电子与基态原子的相互作用, 数值计算了铯原子nS (n=30-60)里德堡态与6S基态原子形成的长程里德堡分子的势能曲线. 并对最外层势阱进行分析, 获得长程里德堡分子的势阱深度、平衡距离与主量子数n的关系. 为实验制备里德堡分子并进一步分析其性质提供理论依据. 里德堡分子对外界非常敏感, 可用于微弱信号的检测.     

基于TDC-GP2的时间间隔测量系统设计

精确的时间间隔测量在时间同步系统有着至关重要的作用,为了满足大量程和高精度的需求,介绍了一种直接计数法和时间-数字装换法相结合的时间间隔测量系统;设计中采用两片TDC-GP2时间-数字转换芯片,结合FPGA和上位机,可以实现精度为1 ns时差测量;经过大量的实际测量,系统的分辨率为70 ps,精度为1 ns,最大可以测量1 s的时间间隔;该设计的系统具有可靠性高、功耗低、精度高、使用灵活等优点。     

兼容多波长及多脉宽输出的频率转换系统设计

通过对多种频率转换方案的深入对比分析,设计了一套兼容多波长及多脉宽高效输出的频率转换系统。采用"Ⅱ+Ⅱ"类双晶体级联的方式,可以实现"偏振失配"三倍频和Ⅱ类双晶体正交级联二倍频两种模式间的快速切换。通过数值模拟程序优化了晶体构型,结果表明,当两块晶体厚度均为10mm时,可以兼顾低功率长脉冲和高功率短脉冲对效率和稳定性的需求。     

Sampling 4-chlorophenol in water by DGT technique with molecularly imprinted polymer as binding agent and nylon membrane as diffusive layer

For the first time, a diffusive gradients in thin films (DGT) device using molecularly imprinted polymer (MIP) as the binding agent and nylon membrane (NM) as the diffusive layer (NM-MIP-DGT) has been developed for sampling 4-chlorophenol (4-CP) in water. The MIP was prepared by precipitation polymerization with methacrylic acid as monomer and ethyleneglycoldimethacrylate as cross-linker. The diffusion coefficient of 4-CP through NM was obtained to be 0.788 ± 0.040 μ cm² s⁻¹ by diffusion cell method. The ratio was 1.01 ± 0.05 (mean ± standard deviation) for the concentration of 4-CP sampled by NM-MIP-DGT and analyzed by HPLC method to the total concentration of 4-CP in the synthetic solution where free 4-CP species dominated. The results showed that NM-MIP-DGT could sample 4-CP in synthetic solution accurately. The performance of NM-MIP-DGT for sampling 4-CP was independent of pH in the range of 3–7 and ionic strength in the range of 0.0001–0.1 mol L⁻¹ NaCl solution. The concentration of free form of 4-CP sampled by NM-MIP-DGT decreased with the increasing concentration of dissolved organic carbon in different water samples due to the electrostatic interaction of natural organic compounds with 4-CP. 1.8 mg L⁻¹ of the free form of 4-CP was determined by HPLC which was sampled by NM-MIP-DGT in an intermediate untreated industrial effluent. The NM-MIP-DGT can be a potential passive tool for sampling the free form of 4-CP in water.     

Identification of Metabolites of Epimedin A in Rats Using UPLC/Q–TOF–MS

Herba Epimedii (Epimedium) is a kind of tonic herb, widely used in China. Epimedin A is a major component of Herba Epimedii with bioactivities. Analysis of the metabolic profile in vivo plays a pivotal role in understanding how traditional Chinese medicine works. And the metabolites of epimedin A might influence the effects of Herba Epimedii. Moreover, the metabolic routes of epimedin A provide an important basis for safety evaluation. Until now, little has been known about the metabolism of epimedin A. The current study was designed to characterize the metabolic pathways of epimedin A in vivo. The metabolites in rat plasma, bile, feces, and urine were identified by UPLC/Q–TOF–MS analysis. A total of 27 metabolites from epimedin A were detected or tentatively identified. The major metabolic processes were hydrolysis, hydrogenation, hydroxylation, dehydrogenation, demethylation, and conjugation with glucuronic acid and different sugars. The present study revealed the metabolic pathways of epimedin A in rat for the first time, and epimedin A could undergo extensive phase I and phase II metabolism in rat. These findings would provide an important basis for the further study and clinical application of epimedin A. In addition, the results of this work have shown the feasibility of the UPLC/Q–TOF–MS approach for rapid and reliable characterization of metabolites.     

Tirucallane‐Type Triterpenoids from Celastrus stylosus Wall.

Two new tirucallane‐type triterpenoids, (24Z)‐tirucalla‐7,24‐diene‐3β,11β,26‐triol ( 1 ) and (3S,24R)‐tirucall‐7‐ene‐3,24,25‐triol ( 2 ), along with the known compound celastrol ( 3 ), were isolated from the root barks of Celastrus stylosus Wall . The structures of 1 – 3 were established by spectroscopic methods, including extensive 2D NMR and MS analyses. It is the first report on tirucallane‐type triterpenoids from the genus Celastrus and may be of vital chemotaxonomic significance.     

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond was investigated and a series of N3-ethoxymethylated heterocyclic compounds were synthesized. A mechanism in which diethyl phosphite acts as an efficient surrogate of ethanol was proposed and supported by several evidences.     

Synthesis of C2-functionalized pyrimidines from 3,4-dihydropyrimidin-2(1H)-ones by the Mitsunobu coupling reaction

The Biginelli 3,4-dihydropyrimidin-2(1H)-one was converted to various C2-multifunctionalized pyrimidines via the dehydrogenation and Mitsunobu reaction using amines, alcohols, phenols and carboxylic acids as nucleophiles. A possible mechanism was also proposed to rationalize the formation of products.