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21.
A new modular slit die with optical windows in two different positions and three pressure transducers flush-mounted along the wall was built and coupled to the exit of a twin-screw extruder. Thus, the birefringence and the pressure drop of polystyrene were monitored inline during extrusion. Two experimental procedures were tested: steady-state and cessation of extruder feeding. The latter proved to be very useful in the case of polystyrene since the ratio between the birefringence and the pressure drop can be quantified for a wide range of steady-state conditions with a single experiment. In fact, down to relatively lower values of pressure drop, the birefringence proved to be a function of shear stress at the wall only, depending neither on the initial feeding rate nor on the aspect ratio of the slit die, for W/h down to 5, at least. 相似文献
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Quantitative determination of isoquinoline alkaloids and chlorogenic acid in Berberis species using ultra high performance liquid chromatography with hybrid triple quadrupole linear ion trap mass spectrometry 下载免费PDF全文
Awantika Singh Vikas Bajpai Sunil Kumar Kamal Ram Arya Kulwant Rai Sharma Brijesh Kumar 《Journal of separation science》2015,38(12):2007-2013
Berberis species are well known and used extensively as medicinal plants in traditional medicine. They have many medicinal values attributable to the presence of alkaloids having different pharmacological activities. In this study, a method was developed and validated as per international conference on harmonization guidelines using ultra high performance liquid chromatography with hybrid triple quadrupole‐linear ion trap mass spectrometry operated in the multiple reaction monitoring mode for nine bioactive compounds, including protoberberine alkaloids, aporphine alkaloids and chlorogenic acid. This method was applied in different plant parts of eight Berberis species to determine variations in content of nine bioactive compounds. The separation was achieved on an ACQUITY UPLC CSH? C18 column using a gradient mobile phase at flow rate 0.3 mL/min. Calibration curves for all the nine analytes provided optimum linear detector response (with R2 ≥0.9989) over the concentration range of 0.5–1000 ng/mL. The precision and accuracy were within RSDs ≤2.4 and ≤2.3%, respectively. The results indicated significant variation in the total contents of the nine compounds in Berberis species. 相似文献
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Optical performance monitoring (OPM) is essential to guarantee the robust and reliable operation of few-mode fiber (FMF)-based transmission. The available OPM methods including the analytical models such as the enhanced Gaussian noise model provide high accuracy along with high computational complexity which makes them improper for real-time implementations. As an alternative approach, machine learning (ML)-based OPM removes this barrier at the cost of leveraging a large training dataset. However, generating a field or synthetic dataset for FMF-based transmission is very hard and time-consuming. As a specific ML deployment, active learning (AL) is designed to work with a small training dataset, therefore, in this paper, we employ AL for OPM in FMF-based transmission. Results indicate that the proposed AL-based OPM can properly estimate the generalized signal-to-noise ratio by using a very small training dataset and achieve the root mean squared error similar to that obtained by working on large training datasets. 相似文献
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利用柱切换液相色谱,建立了参附注射液中苯甲酰新乌头原碱、苯甲酰乌头原碱、苯甲酰次乌头原碱、新乌头碱、次乌头碱和乌头碱6种乌头碱类生物碱,以及Rg1、Re、Rf、Rb1、Rc、Ro、Rb2、Rb3、Rd 9种人参皂苷的分析方法。首先利用强阳离子交换的在线固相小柱选择性富集和净化样品中生物碱类成分,优化了色谱条件;并采用EC-C18柱作为人参皂苷的分析柱,通过优化实验条件,结合柱切换方式,去除了样品中辅料等大极性基质成分对色谱柱的污染,实现了生物碱分析和人参皂苷分析的自动切换。结果显示,样品中的生物碱和人参皂苷分离良好,线性相关系数(r2)均大于0.999,连续进样精密度的相对标准偏差(RSD) < 2.0%,重复性的RSD < 2.0%;其中6种生物碱的平均回收率为95.1%~98.6%,检出限为4.0~8.2 ng/mL;9种人参皂苷的平均回收率为91.7%~104%。所构建的基于柱切换液相色谱技术的在线固相萃取方法能够有效去除样品中的基质干扰,快速完成参附注射液中3种单酯型生物碱和9种人参皂苷的快速定量,同时也可对3种双酯型生物碱进行限量检测,可应用于药物的质量评价。 相似文献
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Candle soot (CS) is a desirable carbon nanomaterial for sensors owing to its highly porous nanostructure and large specific surface area. CS is advantageous in its low-cost and facile preparation compared to graphene and carbon nanotubes, but its pristine nanostructure is susceptible to collapse, hampering its application in electronic devices. This article reports conformal coating of nanoscale crosslinked hydrophilic polymer on CS film using initiated chemical vapor deposition, which well preserved the CS nanostructure and obtained nanoporous CS@polymer composites. Tuning coating thickness enabled composites with different morphologies and specific surface areas. Surprisingly, the humidity sensor made from composite with the lowest filling degree, thus largest specific surface area, showed relatively low sensitivity, which is likely due to its discontinuous structure, thus insufficient conductive channels. Composite sensor with optimum filling degree shows excellent sensing response of more than 103 with the linearity of R2 = 0.9400 within a broad relative humidity range from 11% to 96%. The composite sensor also exhibits outstanding sensing performance compared to literature with low hysteresis (3.00%), a satisfactory response time (28.69 s), and a fast recovery time (0.19 s). The composite sensor is fairly stable and durable even after 24 h soaking in water. Furthermore, embedding a humidity sensor into a face mask realizes real-time monitoring of human breath and cough, suggesting promising applications in respiratory monitoring. 相似文献
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