Propagation of the surface waves along a two-dimensional plasma column and the far-field radiation patterns are studied in thin column approximation. Wave phase and attenuation coefficients are calculated for various ...Propagation of the surface waves along a two-dimensional plasma column and the far-field radiation patterns are studied in thin column approximation. Wave phase and attenuation coefficients are calculated for various plasma parameters. The radiation patterns are shown. Results show that the radiation patterns are controllable by flexibly changing the plasma length and other parameters in comparison to the metal monopole antenna. It is meaningful and instructional for the optimization of the plasma antenna design.展开更多
In the present paper, based on the conservation law of mass and momentum for ion and electron, the distribution of velocity, density of ions and electrons along radial direction are solved numerically. Furthermore, th...In the present paper, based on the conservation law of mass and momentum for ion and electron, the distribution of velocity, density of ions and electrons along radial direction are solved numerically. Furthermore, the comparison between MHD properties of ambipolar and qua- si- ambipolar diffusion is made. The numerical calculation is carried out for argon plasma. The results show that the ion density, ratio of ion and electron velocity at the cathode sheath boundary surface in- crease with the intensity of magnetic induction, meanwhile, the distance between sheaths decreases as well as the radial velocity of ion and electron at the anode sheath boundary. The ion density varies in accord with experiment qualitatively. All parameters mentioned above are not sensitive to magnetic field in ambipolar diffusion.展开更多
We present a study of magnetic transport and radiation properties during compression of a magnetized laboratory plasma.A theta pinch is used to produce a magnetized plasma column undergoing radial implosion,with plasm...We present a study of magnetic transport and radiation properties during compression of a magnetized laboratory plasma.A theta pinch is used to produce a magnetized plasma column undergoing radial implosion,with plasma parameters comprehensively measured through diverse diagnostic techniques.High-resolution observations show the implosion progressing through three stages:compression,expansion,and recompression.An anomalous demagnetization phenomenon is observed during the first compression stage,wherein the magnetic field at the plasma center is depleted as the density increases.We reveal the demagnetization mechanism and formulate a straightforward criterion for determining its occurrence,through analysis based on extended-magnetohydrodynamics theory and a generalized Ohm’s law.Additionally,we quantitatively evaluate the radiation losses and magnetic field variations during the two compression stages,providing experimental evidence that magnetic transport can influence the radiation properties by altering the plasma hydrodynamics.Furthermore,extrapolated results using our findings reveal direct relevance to magnetized inertial confinement fusion,space,and astrophysical plasma scenarios.展开更多
A plasma column excited by a surface wave can act as a plasma antenna. Experiments are carried out to study the current and conductivity distributions, field, power patterns, directivity and efficiency of such a plasm...A plasma column excited by a surface wave can act as a plasma antenna. Experiments are carried out to study the current and conductivity distributions, field, power patterns, directivity and efficiency of such a plasma antenna. In addition, an equivalent metallic copper antenna is built up and its antenna parameters are compared with that of the plasma antenna. Our findings indicate that the power content in the harmonics of the plasma antenna is more prominent as compared to the copper antenna （which only generates a fundamental frequency）. However, the power patterns for both antennae are quite similar. To provide a more qualitative understanding regarding the generation of harmonics in the field of the plasma antenna, a bi-spectral analysis is performed to study the nonlinear interactions in the current fluctuations. Some specific features of the plasma antenna are investigated in our study, which may enhance the application prospect of the plasma antenna with respect to the conventional metallic antenna.展开更多
Egg white protein bonded columns were developed for HPLC. These columns can be used under aqueous mobile phase and separate various kinds of drug enantiomers. Hyphenated techniques using protein bonded columns with LC...Egg white protein bonded columns were developed for HPLC. These columns can be used under aqueous mobile phase and separate various kinds of drug enantiomers. Hyphenated techniques using protein bonded columns with LC/MS and/or column switching have been recognized as integral methods in pharmaceutical research to analyze drug enantiomers. Therefore, these methods are very useful for research fields of pharmacokinetics and pharmacology.展开更多
The dynamic process of arc pressure and corresponding arc column expansion, which is the main feature after arc ignition and has a significant effect on the breaking behaviour of low -voltage circuit breakers, is stud...The dynamic process of arc pressure and corresponding arc column expansion, which is the main feature after arc ignition and has a significant effect on the breaking behaviour of low -voltage circuit breakers, is studied. By constructing a three dimensional mathematical model of air arc plasma and adopting the Control Volume Method, the parameters of arc plasma including temperature and pressure are obtained. The variations of pressure field and temperature field with time are simulated. The result indicates that there are six stages for the process of arc column expansion according to the variation of pressure in arc chamber. In the first stage, the maximal pressure locates in the region close to cathode, and in the second stage the maximal pressure shifts to the region close to the anode. In the third stage, the pressure difference between the middle of arc column and the ambient gas is very large, so the arc column begins to expand apparently. In the fourth stage, the pressure wave propagates towards both ends and the maximal pressure appears at the two ends when the pressure wave reaches both sidewalls. In the fifth stage, the pressure wave is reflected and collides in the middle of the arc chamber. In the last stage, the propagation and reflection of pressure wave will repeat several times until a steady burning state is reached. In addition, the experimental results of arc column expansion, corresponding to the arc pressure variation, are presented to verify the simulation results.展开更多
A selective, sensitive and high throughput liquid chromatography-tandem mass spectro-metry （LC-ESI-MS/MS） method has been developed for separation and quantification of metoprolol enantiomers on a chiral Lux Amylose...A selective, sensitive and high throughput liquid chromatography-tandem mass spectro-metry （LC-ESI-MS/MS） method has been developed for separation and quantification of metoprolol enantiomers on a chiral Lux Amylose-2 （250 mm＆#215;4.6 mm, 5 mm） column. Solid phase extraction of （S）-（-）- and （R）-（t）-metoprolol and rac-metoprolol-d6 as an internal standard （IS） was achieved on Lichrosep DVB HL cartridges employing 200 mL human plasma. Both the analytes were chromatographically separated with a resolution factor of 2.24 using 15 mM ammonium acetate in water, pH 5.0 and 0.1% （v/v） diethyl amine in acetonitrile （50：50, v/v） as the mobile phase within 7.0 min. The precursor-product ion transitions for the enantiomers and IS were monitored in the multiple reaction monitoring and positive ionization mode. The method was validated over the concentration range of 0.500-500 ng/mL for both the enantiomers. Matrix effect was assessed by post-column analyte infusion experiment and the mean extraction recovery was greater than 94.0% for both the enantiomers at all quality control levels. The stability of analytes was evaluated in plasma and whole blood under different storage conditions. The method was successfully applied to a clinical study in 14 healthy volunteers after oral administration of 200 mg metoprolol tablet under fasting conditions. The assay reproducibility is shown by reanalysis of 68 incurred samples. The suitability of the developed method was assessed in comparison with＆amp;nbsp;different chromatographic methods developed for stereoselective analysis of metoprolol in biological matrices.展开更多
目的采用一步吸附及分步解吸的柱层析技术——扩张床吸附(expanded bed adsorption,EBA)技术,从原料血浆中分离多个有效组分,从而提高血浆的综合利用率。方法以琼脂糖(碳化钨)-DEAE为吸附介质,将原料血浆按一定流速流经层析柱,并使待分...目的采用一步吸附及分步解吸的柱层析技术——扩张床吸附(expanded bed adsorption,EBA)技术,从原料血浆中分离多个有效组分,从而提高血浆的综合利用率。方法以琼脂糖(碳化钨)-DEAE为吸附介质,将原料血浆按一定流速流经层析柱,并使待分离组分吸附于介质上,通过不同的缓冲液组成、洗脱流速、洗脱体积分步分离有效组分,并初步探讨工艺放大过程中的关键因素。结果 EBA技术可从原料血浆中依次分离出白蛋白、免疫球蛋白、纤维蛋白原、α-1蛋白酶抑制剂4种蛋白;该技术在工艺放大过程中,柱高及洗脱流速是影响分离效果的关键因素;该技术可去除部分病毒,使病毒滴度降低约一个数量级。结论一步柱层析技术具有血浆综合利用度高、易操作、操作周期短、成本低、可去除病毒等优势,其有望成为传统低温乙醇工艺的有效替代技术,应用于工业化生产。展开更多
文摘Propagation of the surface waves along a two-dimensional plasma column and the far-field radiation patterns are studied in thin column approximation. Wave phase and attenuation coefficients are calculated for various plasma parameters. The radiation patterns are shown. Results show that the radiation patterns are controllable by flexibly changing the plasma length and other parameters in comparison to the metal monopole antenna. It is meaningful and instructional for the optimization of the plasma antenna design.
文摘In the present paper, based on the conservation law of mass and momentum for ion and electron, the distribution of velocity, density of ions and electrons along radial direction are solved numerically. Furthermore, the comparison between MHD properties of ambipolar and qua- si- ambipolar diffusion is made. The numerical calculation is carried out for argon plasma. The results show that the ion density, ratio of ion and electron velocity at the cathode sheath boundary surface in- crease with the intensity of magnetic induction, meanwhile, the distance between sheaths decreases as well as the radial velocity of ion and electron at the anode sheath boundary. The ion density varies in accord with experiment qualitatively. All parameters mentioned above are not sensitive to magnetic field in ambipolar diffusion.
基金the State Key Development Program for Basic Research of China(Grant No.2022YFA1602503)the National Natural Science Foundation of China(Grant Nos.12120101005 and 12205247)
文摘We present a study of magnetic transport and radiation properties during compression of a magnetized laboratory plasma.A theta pinch is used to produce a magnetized plasma column undergoing radial implosion,with plasma parameters comprehensively measured through diverse diagnostic techniques.High-resolution observations show the implosion progressing through three stages:compression,expansion,and recompression.An anomalous demagnetization phenomenon is observed during the first compression stage,wherein the magnetic field at the plasma center is depleted as the density increases.We reveal the demagnetization mechanism and formulate a straightforward criterion for determining its occurrence,through analysis based on extended-magnetohydrodynamics theory and a generalized Ohm’s law.Additionally,we quantitatively evaluate the radiation losses and magnetic field variations during the two compression stages,providing experimental evidence that magnetic transport can influence the radiation properties by altering the plasma hydrodynamics.Furthermore,extrapolated results using our findings reveal direct relevance to magnetized inertial confinement fusion,space,and astrophysical plasma scenarios.
文摘A plasma column excited by a surface wave can act as a plasma antenna. Experiments are carried out to study the current and conductivity distributions, field, power patterns, directivity and efficiency of such a plasma antenna. In addition, an equivalent metallic copper antenna is built up and its antenna parameters are compared with that of the plasma antenna. Our findings indicate that the power content in the harmonics of the plasma antenna is more prominent as compared to the copper antenna （which only generates a fundamental frequency）. However, the power patterns for both antennae are quite similar. To provide a more qualitative understanding regarding the generation of harmonics in the field of the plasma antenna, a bi-spectral analysis is performed to study the nonlinear interactions in the current fluctuations. Some specific features of the plasma antenna are investigated in our study, which may enhance the application prospect of the plasma antenna with respect to the conventional metallic antenna.
文摘Egg white protein bonded columns were developed for HPLC. These columns can be used under aqueous mobile phase and separate various kinds of drug enantiomers. Hyphenated techniques using protein bonded columns with LC/MS and/or column switching have been recognized as integral methods in pharmaceutical research to analyze drug enantiomers. Therefore, these methods are very useful for research fields of pharmacokinetics and pharmacology.
基金National Natural Science Foundation of China(Nos.5047702,50537050 and 50525722)Science and Technology Research Key Project of MOE(10518)
文摘The dynamic process of arc pressure and corresponding arc column expansion, which is the main feature after arc ignition and has a significant effect on the breaking behaviour of low -voltage circuit breakers, is studied. By constructing a three dimensional mathematical model of air arc plasma and adopting the Control Volume Method, the parameters of arc plasma including temperature and pressure are obtained. The variations of pressure field and temperature field with time are simulated. The result indicates that there are six stages for the process of arc column expansion according to the variation of pressure in arc chamber. In the first stage, the maximal pressure locates in the region close to cathode, and in the second stage the maximal pressure shifts to the region close to the anode. In the third stage, the pressure difference between the middle of arc column and the ambient gas is very large, so the arc column begins to expand apparently. In the fourth stage, the pressure wave propagates towards both ends and the maximal pressure appears at the two ends when the pressure wave reaches both sidewalls. In the fifth stage, the pressure wave is reflected and collides in the middle of the arc chamber. In the last stage, the propagation and reflection of pressure wave will repeat several times until a steady burning state is reached. In addition, the experimental results of arc column expansion, corresponding to the arc pressure variation, are presented to verify the simulation results.
文摘A selective, sensitive and high throughput liquid chromatography-tandem mass spectro-metry （LC-ESI-MS/MS） method has been developed for separation and quantification of metoprolol enantiomers on a chiral Lux Amylose-2 （250 mm＆#215;4.6 mm, 5 mm） column. Solid phase extraction of （S）-（-）- and （R）-（t）-metoprolol and rac-metoprolol-d6 as an internal standard （IS） was achieved on Lichrosep DVB HL cartridges employing 200 mL human plasma. Both the analytes were chromatographically separated with a resolution factor of 2.24 using 15 mM ammonium acetate in water, pH 5.0 and 0.1% （v/v） diethyl amine in acetonitrile （50：50, v/v） as the mobile phase within 7.0 min. The precursor-product ion transitions for the enantiomers and IS were monitored in the multiple reaction monitoring and positive ionization mode. The method was validated over the concentration range of 0.500-500 ng/mL for both the enantiomers. Matrix effect was assessed by post-column analyte infusion experiment and the mean extraction recovery was greater than 94.0% for both the enantiomers at all quality control levels. The stability of analytes was evaluated in plasma and whole blood under different storage conditions. The method was successfully applied to a clinical study in 14 healthy volunteers after oral administration of 200 mg metoprolol tablet under fasting conditions. The assay reproducibility is shown by reanalysis of 68 incurred samples. The suitability of the developed method was assessed in comparison with＆amp;nbsp;different chromatographic methods developed for stereoselective analysis of metoprolol in biological matrices.
文摘目的采用一步吸附及分步解吸的柱层析技术——扩张床吸附(expanded bed adsorption,EBA)技术,从原料血浆中分离多个有效组分,从而提高血浆的综合利用率。方法以琼脂糖(碳化钨)-DEAE为吸附介质,将原料血浆按一定流速流经层析柱,并使待分离组分吸附于介质上,通过不同的缓冲液组成、洗脱流速、洗脱体积分步分离有效组分,并初步探讨工艺放大过程中的关键因素。结果 EBA技术可从原料血浆中依次分离出白蛋白、免疫球蛋白、纤维蛋白原、α-1蛋白酶抑制剂4种蛋白;该技术在工艺放大过程中,柱高及洗脱流速是影响分离效果的关键因素;该技术可去除部分病毒,使病毒滴度降低约一个数量级。结论一步柱层析技术具有血浆综合利用度高、易操作、操作周期短、成本低、可去除病毒等优势,其有望成为传统低温乙醇工艺的有效替代技术,应用于工业化生产。
