Simultaneous quantitation of 23 bioactive compounds in Tanreqing capsule by high‐performance liquid chromatography electrospray ionization tandem mass spectrometry

Tanreqing capsule (TRQC) is a formulation frequently used in traditional Chinese medicine to treat pyrexia, cough, expectoration and pharyngalgia. Since the pharmacological action of traditional Chinese medicines is closely related to their complex and diverse constituents, understanding the exact composition of TRQC is important to elucidate its clinical effectiveness and mechanism of action as well as to establish quality control methods and resolve safety issues. Herein, we employed high‐performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry for the simultaneous quantitation of 23 bioactive compounds in five batches of TRQC; the analytes could be categorized into five types: organic acids (seven compounds), flavonoids (10 compounds), iridoids (two compounds), phenylethanoid glycosides (two compounds) and bile acids (two compounds). The calibration curves for all analytes showed good linearity (r > 0.9953), and the inter‐ and intra‐day precisions did not exceed 4.94 and 4.97%, respectively. The recoveries varied from 90.47% to 109.80%; the corresponding relative standard deviations (RSDs) did not exceed 4.94%; and the repeatability (RSD < 4.72%) and stability (RSD < 4.88%) were also within acceptable limits. Thus, this study can be viewed as a fundamental reference for setting comprehensive TRQC quality standards.     

Finite-time stabilization of nonlinear systems using an event-triggered controller with exponential gains

Nonlinear Dynamics - This paper investigates the finite-time stabilization for a class of nonlinear systems by proposing a new event-triggered controller. The novelty lies in that, by introducing...     

MECHANICAL ANALYSIS OF TOROFLUX

流动环是一款魔术玩具,具有丰富的力学行为。制作流动环时应用了预应力储存技术,使得环内部储存了弹性弯曲变形能。一经外界扰动,流动环会迅速张开,进入一种新的稳定平衡状态;若给张开的流体环输入某种形式的能量,环会合拢,恢复原有的稳定平衡状态。本文从能量的角度对流动环张开与合拢等现象进行力学分析。     

保温层结构对感应加热制备太阳能级多晶硅影响的数值模拟研究

定向凝固技术是制备太阳能级多晶硅的主要制备技术.在该技术路线之中,优化多晶铸锭炉的热场结构和控制硅熔体的对流形态是获得高品质多晶硅的有效途径之一.本文设计了三种热场保温层,通过分析不同保温层下坩埚内硅熔体的热场、流场、固液界面、氧含量等的变化,确定了优化的保温层结构.研究发现,在传统固化碳毡保温层中引入石墨层可以使多晶炉内形成两个“热源”,提高多晶炉的热效率,使其能耗降低了38.5;;在洛伦兹力的作用下硅熔体中仅存在一个上下贯通的涡流,有利于硅中杂质原子的挥发.同时,添加石墨保温层后固液界面的形状由“W”状转变为凹状,其上的氧含量有所降低,并且V/Gn值在整个固液界面范围内均大于临界值,可以有效抑制氧沉淀.可见,在感应加热多晶硅生长系统中,采用固化碳毡+石墨保温层时,有利于降低多晶硅的生产成本并提高多晶硅的品质.     

无人机视角下的林木爆燃火特性研究

森林火灾“爆燃”现象的特征是突然发生的高强度、高蔓延速度的燃烧。目前为止，关于“爆燃火”的原因还没有达成共识。以无人机视角下对林木爆燃火特性研究，以四川木里特大森林火灾为研究对象，通过分析凉山州某森林扑火部队3月31日木里森林火灾当天KWT（科卫泰）无人机航拍火场画面，结合无人机实时影像及实地调研数据，分析了峡谷地形林火蔓延时空特征，探讨了峡谷中风向风速变化时空分布规律，研究了地形变化条件下，不同海拔高度风速特征，建立了无人机倾角测量风速模型（其中为风速m·s-1，为无人机倾角°）。结果表明，高山峻岭特殊地形环境下每天4:00—12:00时间段为静风期，为峡谷林火扑救最佳时期；午后15:00—17:00和晚上20:00—22:00为山谷地形风速活跃期；仿真软件数据显示山顶、谷底与山腰不同海拔位置的风速风向不统一，谷底会产生乱流现象，且风速与海拔不存在正相关关系，小气候在复杂地形中占主导影响地位；在谷口至山谷深处的中间位置会出现气流速度的波峰状态，并易形成乱流，为爆燃火发生提供了客观必要条件。该研究可为复杂地形环境下，森林草原火灾扑救安全提供数据和技术支撑。     

化学法改性煤沥青脱除苯并芘的研究

在管式反应器中采用苯甲酸、聚乙二醇、固体古马隆树脂（S）、液体古马隆树脂（L）为添加剂来降低煤沥青中有害物质苯并芘的含量，以期使得煤沥青可绿色化应用。采用紫外-可见分光光度计分析煤沥青中苯并芘含量。考察了反应温度、反应时间、添加剂添加量、催化剂等工艺条件对添加剂脱除煤沥青中苯并芘的影响。结果表明，不同工艺条件能降低煤沥青中苯并芘的含量。在优化条件下，不同添加剂对苯并芘脱除率由高到低依次为：液体古马隆树脂、聚乙二醇、苯甲酸和固体古马隆树脂。分析其反应机理，这与催化剂的酸性相关，发生亲电取代反应。结果表明，液体古马隆树脂（L）在催化剂存在下对煤沥青中苯并芘脱除率可达73.0%，显示了良好的应用前景。     

掺锗提高VO2薄膜的相变温度机理研究

二氧化钒(VO₂)作为一种长久以来备受关注的新型可逆相变材料,发展潜力巨大,其相变温度(T_MIT)的调控一直是研究热点。本文主要利用锗离子作为掺杂离子探索其对VO₂薄膜T_MIT的影响,并尝试解释其内部作用机理。在约1 cm²大小抛光的氧化铝薄片上沉积了一系列含不同比例锗离子VO₂薄膜。研究发现锗离子作为掺杂离子确实有利于T_MIT的提高(本课题T_MIT最大可达84.7 ℃)。T_MIT提高的主要原因是锗离子的引入能够强化单斜态V-V二聚体的稳定性,进而增强单斜态的稳定性,使得低温单斜态向四方金红石态转变更加困难。     

Development and validation of a sensitive liquid‐chromatography tandem mass spectrometry assay for mycophenolic acid and metabolites in HepaRG cell culture: Characterization of metabolism interactions between p‐cresol and mycophenolic acid

Mycophenolic acid (MPA), a frequently used immunosuppressant, exhibits large inter‐patient pharmacokinetic variability. This study (a) developed and validated a sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) assay for MPA and metabolites [MPA glucuronide (MPAG) and acyl‐glucuronide (AcMPAG)] in the culture medium of HepaRG cells; and (b) characterized the metabolism interaction between MPA and p‐cresol (a common uremic toxin) in this in vitro model as a potential mechanism of pharmacokinetic variability. Chromatographic separation was achieved with a C₁₈ column (4.6 × 250 mm,5 μm) using a gradient elution with water and methanol (with 0.1% formic acid and 2 mm ammonium acetate). A dual ion source ionization mode with positive multiple reaction monitoring was utilized. Multiple reaction monitoring mass transitions (m/z) were: MPA (320.95 → 207.05), MPAG (514.10 → 303.20) and AcMPAG (514.10 → 207.05). MPA‐d₃ (323.95 → 210.15) and MPAG‐d₃ (517.00 → 306.10) were utilized as internal standards. The calibration curves were linear from 0.00467 to 3.2 μg/mL for MPA/MPAG and from 0.00467 to 0.1 μg/mL for AcMPAG. The assay was validated based on industry standards. p‐Cresol inhibited MPA glucuronidation (IC₅₀ ≈ 55 μm ) and increased MPA concentration (up to >2‐fold) at physiologically relevant substrate‐inhibitor concentrations (n = 3). Our findings suggested that fluctuations in p‐cresol concentrations might be in part responsible for the large pharmacokinetic variability observed for MPA in the clinic.