检索结果-南通市图书馆

基于波长转换RP-HPLC法的茯苓皮多成分含量测定及特征图谱方法研究

在线全文

学校读者我要写书评

暂无评论

药物分析杂志 2024年第2期44卷 214-223页

作者：徐凡袁杰蒲婧哲胡冲张亚中刘守金安徽中医药大学药学院合肥230012 安徽省食品药品检验研究院合肥230051 国家药品监督管理局中药质量研究与评价重点实验室合肥230051 中药饮片制造新技术安徽省重点实验室合肥230012

目的:本文通过建立茯苓皮的双波长切换HPLC特征图谱方法,同时建立茯苓皮中11个三萜类成分含量的测定方法,旨在为茯苓皮全面的质量评价提供定性和定量方法。方法:采用Agilent 5 HC-C_(18)(2)色谱柱(250 mm×4.6 mm, 5μm),流动相为乙腈(... 详细信息

目的:本文通过建立茯苓皮的双波长切换HPLC特征图谱方法,同时建立茯苓皮中11个三萜类成分含量的测定方法,旨在为茯苓皮全面的质量评价提供定性和定量方法。方法:采用Agilent 5 HC-C_(18)(2)色谱柱(250 mm×4.6 mm, 5μm),流动相为乙腈(含3%四氢呋喃)(A)和0.1%磷酸水溶液(B),梯度洗脱,流速1 mL·min^(-1),柱温35℃,进样体积20μL,检测波长210、243 nm。结果:所建立的特征图谱能有效的识别18个共有峰,精密度、重复性、稳定性(48 h)试验的RSD均﹤3.7%(n=6);11个待测化学成分能够达到良好分离,在考察质量范围内线性关系良好(r均≥0.999 6),平均回收率95.4%~105.5%,RSD 1.0%~3.1%,精密度、重复性、稳定性(48 h)试验的RSD均≤3.0%(n=6);相似度分析结果显示,大部分产地的茯苓皮药材的相似度很高;含量测定结果表明,11个三萜类成分中茯苓酸A在所有批次茯苓皮中占比最高,另外茯苓酸A、松苓新酸、茯苓酸B、去氢齿孔酸、栓菌酸5个成分的含量波动相对较大,其他成分波动较平缓;不同产地茯苓皮样品无明显地域上的差异。结论:建立了茯苓皮特征图谱和多成分含量测定方法,为茯苓皮的质量控制奠定了基础。

关键词：茯苓皮三萜特征图谱含量测定波长转换

Melatonin relieves heat-induced spermatocyte apoptosis in mouse testes by inhibition of ATF6 and PERK signaling pathways

在线全文

学校读者我要写书评

暂无评论

Zoological Research 2021年第4期42卷 514-524页

作者： De-zhe Qin Hui Cai Cen he Dong-Hui Yang jing Sun Wen-Lai he Ba-Lun Li Jin-Lian Hua Sha Peng College of Veterinary Medicine Shaanxi Centre of Stem Cells Engineering&TechnologyNorthwest A&F UniversityYanglingShaanxi 712100China

Normal spermatogenic processes require the scrotal temperature to be lower than that of the body as excessive heat affects spermatogenesis in the testes,reduces sperm quality and quantity,and even causes *** reticulum stress(ERS)is a crucial factor in many *** several studies have linked ERS to heat stress,researchers have not yet determined which ERS signaling pathways contribute to heat-induced testicular *** activates antioxidant enzymes,scavenges free radicals,and protects the testes from inflammation;however,few studies have reported on the influence of melatonin on heat-induced testicular *** a murine model of testicular hyperthermia,we observed that heat stress causes both ERS and apoptosis in the testes,especially in the *** observations were confirmed using the mouse spermatocyte cell line GC2,where the Atf6 and Perk signaling pathways were activated during heat *** of the above genes effectively reduced spermatocyte damage caused by heat *** with melatonin alleviated heat-induced apoptosis by inhibiting the Atf6 and Perk signaling *** mitigation was dependent on the melatonin *** vivo experiments verified that melatonin treatment relieved heat-induced testicular *** conclusion,our results demonstrated that ATF6 and PERK are important mediators for heat-induced apoptosis,which can be prevented by melatonin ***,our study highlights melatonin as a potential therapeutic agent in mammals for subfertility/infertility induced by testicular hyperthermia.

关键词： heat stress ATF6 PERK Melatonin Spermatocyte

在线全文

学校读者我要写书评

暂无评论

双酚G对斑马鱼神经行为的影响及机制研究

中国环境科学 2024年第5期44卷 2733-2741页

作者：刘再腾罗麟洁王天彩汪星宇邱静穆希岩姜敬哲上海海洋大学海洋科学与生态环境学院上海201306 中国水产科学研究院南海水产研究所农业农村部南海渔业资源开发利用重点实验室广东广州510300 中国农业科学院农业质量标准与检测技术研究所农业农村部农产品质量安全重点实验室北京100081

使用双酚G(BPG)慢性染毒成年斑马鱼,以评估其毒性效应和作用机制.结果表明,50μg/L BPG染毒组显著降低了斑马鱼的移动距离和上下水层切换频率,在底部累积时间增加了22.7%,表现出显著的行为异常;5和50μg/L染毒导致社交距离分别增加了126... 详细信息

使用双酚G(BPG)慢性染毒成年斑马鱼,以评估其毒性效应和作用机制.结果表明,50μg/L BPG染毒组显著降低了斑马鱼的移动距离和上下水层切换频率,在底部累积时间增加了22.7%,表现出显著的行为异常;5和50μg/L染毒导致社交距离分别增加了126.8%和151.2%,社交累积时间分别减少了80.1%和73.7%,表现出显著的社交障碍.切片染色显示脑结构和肠道绒毛受损以及肠道杯状细胞数量和粘液分泌增加,表明潜在的肠道炎症以及神经疾病的发生.进一步的靶向代谢组学显示肠脑神经递质水平紊乱,色氨酸、GABA、谷氨酰胺、去甲肾上腺素、胆碱和组胺等水平显著改变;KEGG通路富集分析表明,苯丙氨酸、酪氨酸和色氨酸生物合成,缬氨酸、亮氨酸和异亮氨酸生物合成,精氨酸生物合成及苯丙氨酸代谢是主要受影响通路且存在性别差异,这些通路通过干扰神经递质转运和稳态,调控斑马鱼行为.BPG染毒,斑马鱼表现出显著的神经行为毒性效应和肠脑神经递质代谢紊乱,肠脑调节可能参与介导该效应.

关键词：双酚类污染物双酚G 神经毒性肠道代谢神经行为影响

在线全文

学校读者我要写书评

暂无评论

极端干旱对鄱阳湖碟形湖水生植物群落的影响

生态与农村环境学报 2024年第6期40卷 790-798页

作者：郭敏余定坤李浙刘涛金杰锋王玉玉北京林业大学生态与自然保护学院北京100083 江西鄱阳湖国家级自然保护区管理局江西南昌330038 江西鄱阳湖湿地生态系统国家定位观测研究站江西南昌330038 国际鹤类基金会北京代表处北京100088

水生植物是水生生态系统的重要组成部分,为底栖动物、鱼类和水鸟提供食物来源和栖息场所。近年来鄱阳湖水位变化剧烈,极端水文事件频发,对水生植物生长产生了不利影响。目前,关于极端干旱对鄱阳湖水生植物的影响报道较少。该研究于2022... 详细信息

水生植物是水生生态系统的重要组成部分,为底栖动物、鱼类和水鸟提供食物来源和栖息场所。近年来鄱阳湖水位变化剧烈,极端水文事件频发,对水生植物生长产生了不利影响。目前,关于极端干旱对鄱阳湖水生植物的影响报道较少。该研究于2022年7月和2023年7月对鄱阳湖典型碟形湖大湖池、沙湖及常湖池的水生植物群落进行调查,结果表明,2022和2023年鄱阳湖碟形湖平均水深分别为(160.27±50.70)、(58.00±21.46)cm,透明度分别为(49.10±14.41)、(47.25±10.91)cm。浮叶植物菱(Trapa spp.)优势度最大,沉水植物刺苦草(Vallisneria spinulosa)和轮叶黑藻(Hydrilla verticillata)优势度及生物量在2023年有所增加。湖区干旱导致水位降低,水体透明度发生变化,影响了植物群落的物种数,导致植物多样性增加。不同年份碟形湖水位和水体透明度的变化对水生植物多样性有显著影响,2 a间鄱阳湖碟形湖水生植物群落的物种组成差异显著,表现为2023年干旱后挺水和湿生植物比例增加。该研究通过对比分析2 a的监测数据,探讨了极端干旱对碟形湖水生植物的影响,研究结果可为鄱阳湖水生植物的恢复和越冬水鸟的食物资源补充管理提供科学依据。

关键词：刺苦草沉水植物物种多样性生物量极端水位

在线全文

学校读者我要写书评

暂无评论

面向防振锤更换的无人机-机器人协同控制

机械与电子 2024年第5期42卷 64-68页

作者：张静孙喆王丹阳西安电力高等专科学校陕西西安710032

防振锤更换现场变动因素较多、存在多种信号干扰,抓取力与防振锤重力间的平衡难度大,稳定性较差,由此,提出一种无人机-机器人协同控制算法。明确防振锤内部结构,考虑线路重量和抗振力需求,计算抓取力和防振锤重力,分析不平衡因素,根据... 详细信息

防振锤更换现场变动因素较多、存在多种信号干扰,抓取力与防振锤重力间的平衡难度大,稳定性较差,由此,提出一种无人机-机器人协同控制算法。明确防振锤内部结构,考虑线路重量和抗振力需求,计算抓取力和防振锤重力,分析不平衡因素,根据构建的无人机-刚柔耦合系统动力学模型,计算不同时间点的最佳的旋转中心值,用于约束机器人运行的最大偏离范围。根据无人机的非线性动态反演关系,以内环控制求得机器人运动轨线与目标轨迹之间的贴合能力,以外环控制获得无人机出现转弯、上升、下降以及停滞状态下的一阶和二阶导数输出数值,采用二阶求导的控制阈值,完成无人机-机器人协同控制。实验结果表明,关节柔性变化轨迹控制稳定性强,无人机姿态角和位置偏差较小,实用价值高。

关键词：防振锤更换协同控制最大偏离函数控制阈值二阶求导

Dynamic interactions of an integrated vehicle–electromagnetic energy harvester–tire system subject to uneven road excitations

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2017年第2期33卷 440-456页

作者： jing Tang Xing zhe Sun Sulian Zhou Mingyi Tan Fluid Structure Interactions Group FEEUniversity of Southampton College of Shipbuilding Engineering Harbin Engineering University

An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electromagnetic energy harvesters and four tires subject to uneven road excitations in order to improve the passengers' riding comfort and harvest the lost engine energy due to uneven roads. Following the derived mathematical formulations and the proposed solution approaches, the numerical simulations of this interaction system subject to a continuous sinusoidal road excitation and a single ramp impact are completed. The simulation results are presented as the dynamic response curves in the forms of the frequency spectrum and the time history, which reveals the complex interaction characteristics of the system for vibration reductions and energy harvesting performance. It has addressed the coupling effects on the dynamic characteristics of the integrated system caused by: (1) the natural modes and frequencies of the vehicle; (2) the vehicle rolling and pitching motions; (3) different road excitations on four wheels; (4) the time delay of a road ramp to impact both the front and rear wheels, etc., which cannot be tackled by an often used quarter vehicle model. The guidelines for engineering applications are given. The developed coupling model and the revealed concept provide a means with analysis idea to investigate the details of four energy harvester motions for electromagnetic suspension designs in order to replace the current passive vehicle isolators and to harvest the lost engine energy. Potential further research directions are suggested for readers to consider in the future.

关键词： Vibration-energy-harvesters Electromagnetic suspensions Mechanical electromagnetic interactions Vehicle dynamics Vibration isolations

基于广义基尼指数和脉冲神经网络的航空交流串联电弧故障检测

在线全文

学校读者我要写书评

暂无评论

国外电子测量技术 2024年第3期43卷 154-161页

作者：刘晓琳米哲荆涛中国民航大学电子信息与自动化学院天津300300

航空电缆在振动作用下很容易产生电连接器松动、线束断裂等情况,从而引起交流电弧故障。针对交流串联电弧故障时频域特征不明显而引起的故障检测问题,提出了一种基于广义基尼指数(generalized Gini indices,GGI)和脉冲神经网络(spiking ... 详细信息

航空电缆在振动作用下很容易产生电连接器松动、线束断裂等情况,从而引起交流电弧故障。针对交流串联电弧故障时频域特征不明显而引起的故障检测问题,提出了一种基于广义基尼指数(generalized Gini indices,GGI)和脉冲神经网络(spiking neural network,SNN)的电弧故障检测方法。首先,提出用广义基尼指数对试验数据电流波形进行分析;其次判断正常周期和故障周期下的数值差距,然后与时域特征指标裕度、峭度、脉冲因子相比,所提指数对电流波形周期故障判断更准确;最后,将广义基尼指数转变成特征值,代入到积分泄漏发放(leaky integrate-and-fire,LIF)模型进行训练,进一步提高方法的普适性。试验结果表明,该方法能够快速有效地检测航空交流串联电弧故障。

关键词：串联电弧广义基尼指数脉冲神经网络故障检测

Martensitic transformation,magnetocaloric effect and phase transition strain in Ni50Mn36-xGexSn14 heusler alloys

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2022年第12期41卷 4217-4222页

作者： Dong zheng Chao jing Bo Lu zhe Li Kun Xu Department of Physics Shanghai UniversityShanghai 200444China Laboratory for Microstructures Shanghai UniversityShanghai 200444China College of Physics and Electronic Engineering Qujing Normal UniversityQujing 655011China

In present work,the effect of Ge substitution for Mn on crystal structure and martensitic transformation was carefully investigated in magnetic shape memory Ni_(50)Mn _(36-x)Ge_(x)Sn_(14)(x=0,1) *** X-ray diffraction(XRD) patterns,it can be found that each sample possesses cubic austenitic structure(L21) at room temperature and the main peak(220) shifts to higher degree with Ge doping,indicating that the cell volume of austenitic phase *** Ge content increasing,martensitic transformation(MT),temperature shifts to higher temperature region and the difference of magnetization between martensitic and austenitic phases(AM) also *** addition,the magnetocaloric effect(MCE) and phase transition strain(ΔL/L) were investigated in *** maximal magnetic entropy change(ΔSm) associated with martensitic transition is 3.9 J·kg^(-1)-K^(-1)with applied magnetic field change of 5 T and the maximal ΔL/L reaches 0.18% in this alloy.

关键词： heusler alloy Martensitic transformation Magnetocaloric effect Phase transition strain

Enhanced Phase Transition in Poly(ethylene glycol) Grafted Butene-1 Copolymers

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2023年第3期41卷 414-421,I0008页

作者： Ya-Hui Lou Wei Li Chun-jing Qv zhe Ma Tianjin Key Laboratory of Composite and Functional Materials and School of Materials Science and EngineeringTianjin UniversityTianjin 300072China

In the present work,a series of poly(ethylene glycol) grafted polybutene-1 copolymers(PB-g-PEG) were designed and successfully synthesized with reaction intermediate method,of which the branch densities and length could be tuned *** branch density varied from 0.39 mol% to 1.23 mol% and the branch length was tuned by employing PEG number-averaged molecular weight(Mn) from 350 Da to 750 Da and 1000 *** non-isothermal crystallization and phase transition behaviors of these butene-1 copolymers with varying branches were systematically explored by differential scanning *** results first showed that compared with the linear polybutene-1 homopolymer,presence of steric 4-[4-(trimethylsilylalkynyl)-phenyl]-1-butene(TMS) groups suppressed crystallization and phase transition of ***,the introduction of long poly(ethylene glycol)(PEG) branches with M_(n)=350-1000 Da not only elevated the peak temperature of the non-isothermal crystallization but also enhanced the Ⅱ-Ⅰ phase transition,with respect to copolymers with TMS ***,the quantitative correlations between phase transition kinetics with the branch parameters(density and length) were *** was found that the phase transition presents a non-monotonic trend with increasing branch density and branch *** this case,the optimal branch density and length obtained were 0.77 mol% and 750 Da,*** the small angle X-ray scattering and transmission electron microscopy,a direct correlation between the phase transition kinetics and the long periodicity of separated phase was obtained,which may be due to the increased internal stress and facilitated stress transport.

关键词： Polybutene-1 copolymer Crystallization kinetics Phase transition Phase separation