For chromatographic separation,the reasonable modulation of stationary phases is the key factor to achieve high separation performance.We proposed that developing MOF stationary phases through precisely modulating the...For chromatographic separation,the reasonable modulation of stationary phases is the key factor to achieve high separation performance.We proposed that developing MOF stationary phases through precisely modulating the thermodynamic interactions between MOFs and analytes is conducive to improving the separation resolution.MIL-125,MIL-125-NH_(2),MIL-143-BTB,and MIL-143-TATB were developed as stationary phases with the careful modulation of organic ligands.MIL-125-NH_(2)and MIL-143-TATB coated columns exhibited much better separation performance than their counterparts,MIL-125 and MIL-143-BTB,respectively.The investigation of the separation mechanism indicated that thermodynamic interaction,rather than kinetic diffusion,was responsible for the separation improvement.MIL-125-NH_(2)and MIL-143-TATB provided stronger and distinguishable interactions with targets than corresponding MIL-125 and MIL-143-BTB,respectively,resulting in enhanced separation performance.This work demonstrates a guide to improving the separation performance of MOF stationary phases by increasing the thermodynamic interactions between MOFs and analytes.展开更多
An ionic liquid assisted hydrogel modified silica was synthesized using a one-pot polymerization and physical coating technique and subsequently applied to mixed-mode liquid chromatography.Analytical techniques,includ...An ionic liquid assisted hydrogel modified silica was synthesized using a one-pot polymerization and physical coating technique and subsequently applied to mixed-mode liquid chromatography.Analytical techniques,including Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),and elemental analysis,etc.,confirmed the successful prepared of this innovative stationary phase.The unique combination of amide,long alkyl chain,and imidazole ring in the hydrogel coating enables the stationary phase to function effectively in hydrophilic/reversed-phase/ion exchange liquid chromatography.Notably,the stationary phase exhibited superior separation performance owing to the synergistic effect of the ionic liquid and hydrogel.This was particularly evident when analyzing various analytes such as organic acids,nucleosides/bases,polycyclic aromatic hydrocarbons(PAHs)and anions.Furthermore,under our operating conditions,an excellent column efficiency of 53,642.9 plates/m was achieved for theobromine.In summary,we have proposed a straightforward strategy to enhance the separation performance of hydrogel coatings in liquid chromatography,thereby broadening the potential applications of hydrogels in the field of separation.展开更多
A series of optically active copolymers with various feed ratios have been synthesized through helix-sense-selective copolymerization catalyzed by[Rh(norbornadiene)Cl]2-triethylamine.This process involves two proline-...A series of optically active copolymers with various feed ratios have been synthesized through helix-sense-selective copolymerization catalyzed by[Rh(norbornadiene)Cl]2-triethylamine.This process involves two proline-derived acetylene monomers,(S)-N-(4-chlorophenyl)carbamoyl-2-ethynyl pyrrolidine(MCl)and(S)-N-(tert-butoxycarbonyl)-2-ethynyl pyrrolidine,followed by acidic deprotection and neutralization.These copolymers adopt helical conformations with a preferred handedness,as demonstrated by nuclear magnetic resonance spectroscopy and a series of spectroscopic analyses.The chiroptical activity intensity of copolymer has been found to increase with MCl content.Consequently,the enantioseparation capabilities of copolymers containing 95 mol%,90 mol%,and 85 mol%MCl units have been assessed as chiral stationary phases in high-performance liquid chromatography because of their good chiroptical activities.These chiral stationary phases effectively enantioseparate racemic alcohols,sulfoxides,amides,and metal complexes.Notably,the copolymer with 90 mol%MCl shows superior chiral recognition ability,especially for 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethanol(α=1.19)and 4-methylbenzenesulfinamide(α=1.47).Insights from molecular dynamic simulation and autodock analysis indicate that hydrogen bonding andπ-πstacking interactions between the chiral stationary phases and enantiomers play a key role for successful chiral separation.Our contribution not only demonstrates the importance of hydrogen bonding donor and copolymer chiroptical activity of chiral stationary phases for chiral resolution,but will also provide valuable insights for the future development of novel stationary phases.展开更多
Covalent organic frameworks(COFs)have demonstrated great potential in chromatographic separation because of unique structure and superior performance.Herein,single-crystal three-dimensional(3D)COFs with regular morpho...Covalent organic frameworks(COFs)have demonstrated great potential in chromatographic separation because of unique structure and superior performance.Herein,single-crystal three-dimensional(3D)COFs with regular morphology,good monodispersity and high specific surface area,were used as a stationary phase for high-performance liquid chromatography(HPLC).The single-crystal 3D COFs packed column not only exhibits high efficiency in separating hydrophobic molecules involving substituted benzenes,halogenated benzenes,halogenated nitrobenzenes,aromatic amines,aromatic hydrocarbons(PAHs)and phthalate esters(PAEs),but also achieves baseline separation of acenaphthene and acenaphthylene with similar physical and chemical properties as well as environmental pollutants,which cannot be quickly separated on commercial C18 column and a polycrystalline 3D COFs packed column.Especially,the column efficiency of 17303-24255 plates/m was obtained for PAEs,and the resolution values for acenaphthene and acenaphthylene,and carbamazepine(CBZ)and carbamazepine-10,11-epoxide(CBZEP)were 1.7and 2.2,respectively.This successful application not only confirmed the great potential of the singlecrystal 3D COFs in HPLC separation of the organic molecules,but also facilitates the application of COFs in separation science.展开更多
By combining multiscale stationary wavelet analysis with fuzzy c-means, a robust edge detection algorithm is presented. Based on the translation invafiance built in multiscale stationary wavelet transform, components ...By combining multiscale stationary wavelet analysis with fuzzy c-means, a robust edge detection algorithm is presented. Based on the translation invafiance built in multiscale stationary wavelet transform, components in different transformed sub-images corresponding to a pixel are employed to form a feature vector of the pixel. All the feature vectors are classified with unsupervised fuzzy c-means to segment the image, and then the edge pixels are checked out by the Canny detector. A series of images contaminated with different intensive Gaussian noises are used to test the novel algorithm. Experiments show that fairly precise edges can be checked out robustly from those images with fairly intensive noise by the proposed algorithm.展开更多
A new capillary gas chromatography stationary phase, monokis (2,6 di O benzyl 3 O propyl (3’)) hexakis(2,6 di O benzyl 3 O methyl) β CD bonded polysiloxane, was synthesized. It ex...A new capillary gas chromatography stationary phase, monokis (2,6 di O benzyl 3 O propyl (3’)) hexakis(2,6 di O benzyl 3 O methyl) β CD bonded polysiloxane, was synthesized. It exhibited separation abilities to disubstituted benzene isomers and some chiral solutes. It was also found that the polarity of CD derivatives can be lowered both by chemically bonding it to polysiloxane and by diluting it in polysiloxane. The separation abilities of the polysiloxane anchored CDs (SP CD) are higher than that of the unbonded CDs (S CD) and the diluted S CD at lower column temperature. Hydrosilylation reaction is one of the best methods to lower the operating temperature of CDs.展开更多
In the literature,stationary phase analysis of Kirchhoff-type demigrated fields is carried out mainly under the following two conditions：（1） The considered isochrone and the target reflector are tangential to each ...In the literature,stationary phase analysis of Kirchhoff-type demigrated fields is carried out mainly under the following two conditions：（1） The considered isochrone and the target reflector are tangential to each other;（2） The spatial duration of the wavelet of the depthmigrated image is short.For the isochrones that are not tangential to the target reflector and for the depth-migrated images that have a large spatial duration,the published stationary phase equation for the demigrated field will become invalid.For performing the stationary phase analysis of the Kirchhoff-type demigrated field under the conditions that the considered isochrone and the target reflector are not tangential to each other and that the spatial duration of the wavelet of the depth-migrated image is not short（the general conditions）,I derive the formulas for the factors appearing in the stationary phase formula in two dimensions,from which I find that for different isochrones the horizontal coordinates of the stationary point of the depth difference function are different.Also,the equation for the Kirchhoff-type demigrated field consists of two parts.One is the true-amplitude demigrated signal and the other is the amplitude distortion factor.From these facts the following two conclusions can be drawn：（1） A demigrated signal is composed of many depth-migrated images and one depth-migrated image trace provides only one sample to the demigrated signal;and（2） The amplitude distortion effect is an effect inherent in the Kirchhoff-type demigration and cannot be eliminated during demigration.If this effect should be eliminated,one should do an amplitude correction after demigration.展开更多
Effective enantioseparation of Naftopidil and its derivatives by HPLC was accomplished using several different polysaccharide-based chiral stationary phases（CSPs）.In normal-phase mode,the compounds were eluted on fo...Effective enantioseparation of Naftopidil and its derivatives by HPLC was accomplished using several different polysaccharide-based chiral stationary phases（CSPs）.In normal-phase mode,the compounds were eluted on four coated-and two immobilized-columns with the mixture of n-hexane,isopropanol and diethylamine（DEA）.Polysaccharide tris（3,5- dimethylphenyl carbamate） was shown to be the best enantiomer selector.In addition,the immobilized column packed with Chiralpak IA or IB was applied under polar-organic and reversed-phase conditions,both of which exhibited excellent enantioselectivity for Naftopidil and its derivatives.Furthermore,the underlying possible chiral recognition mechanisms were discussed.展开更多
Six newly synthesized racemic 1-（substituted phenyl）-4-[3-（indole-4-yl-oxy）-2-hydroxypropyl]-piperazine 1-6 were successfully resolved by carbon dioxide supercritical fluid chromatography （SFC） on an analytical ...Six newly synthesized racemic 1-（substituted phenyl）-4-[3-（indole-4-yl-oxy）-2-hydroxypropyl]-piperazine 1-6 were successfully resolved by carbon dioxide supercritical fluid chromatography （SFC） on an analytical scale column packed with immobilized polysaccharide-based chiral stationary phases （CSPs）. We found that separation on the Chiralpak IA CSP was superior to the other two immobilized CSPs （Chiralpak IB and Chiralpak IC）, and isopropanol （IPA） was a superior modifier compared to the other five solvents including ethanol, methanol, tetrahydrofuran, acetonitrile and dichloromethane. The effects of organic modifier composition, back pressure, and column temperature for enantioseparation of all six compounds were studied. Of the physical parameters studied, modifier composition had the greatest impact on retention. Changing temperature generally had less impact on retention but produced the greatest selectivity changes. The optimum condition was found as follows： Chiralpak IA column, column temperature 35 ~C, back pressure 120 bar, 35% IPA containing 0.1% diethylamine （v/v） in mobile phase, flow rate of mobile phase 3.0 mL/min, UV detection 283 nm. Separation of all six racemic compounds was completed within 10 rain and excellent resolution was obtained. Thus, SFC was found to be the methodology of choice for resolving the enantiomers of this class of compounds.展开更多
This paper investigates the dynamical properties of nonstationary solutions in one-dimensional two-component Bose-Einstein condensates. It gives three kinds of stationary solutions to this model and develops a general...This paper investigates the dynamical properties of nonstationary solutions in one-dimensional two-component Bose-Einstein condensates. It gives three kinds of stationary solutions to this model and develops a general method of constructing nonstationary solutions. It obtains the unique features about general evolution and soliton evolution of nonstationary solutions in this model.展开更多
During the past research, Direct Sequence (DS) Spread Spectrum (SS) signal is modeled as stationary in most cases. Cyclostationary model for SS signal is introduced in this letter. Compared with stationary model, cycl...During the past research, Direct Sequence (DS) Spread Spectrum (SS) signal is modeled as stationary in most cases. Cyclostationary model for SS signal is introduced in this letter. Compared with stationary model, cyclostationary model can preserve more information,and its advantages are shown through example.展开更多
This study aims at establishing if climate change exists in the Niger Delta environment using non-stationary rainfall Intensity-Duration-Frequency (IDF) modelling incorporating time-variant parameters. To compute the ...This study aims at establishing if climate change exists in the Niger Delta environment using non-stationary rainfall Intensity-Duration-Frequency (IDF) modelling incorporating time-variant parameters. To compute the intensity levels, the open-access R-studio software was used based on the General Extreme Value (GEV) distribution function. Among the four linear parameter models adopted for integrating time as a covariate, the fourth linear model incorporating scale and location with the shape function constant produced the least corrected Akaike Information Criteria (AICc), varying between 306.191 to 101.497 for 15 and 1440 minutes, respectively, selected for calibration of the GEV distribution equation. The non-stationary intensities yielded higher values above those of stationary models, proving that the assumption of stationary IDF models underestimated extreme events. The difference of 13.71 mm/hr (22.71%) to 14.26 mm/hr (17.0%) intensities implies an underestimation of the peak flood from a stationary IDF curve. The statistical difference at a 95% confidence level between stationary and non-stationary models was significant, confirming evidence of climatic change influenced by time-variant parameters. Consequently, emphasis should be on applying shorter-duration storms for design purposes occurring with higher intensities to help reduce the flood risk and resultant infrastructural failures.展开更多
It is a new strategy to immobilize cells on the inner wall of a capillary column and use affinity capillary electrophoresis（ACE） to study receptor-ligand interactions or to screen natural products and compounds synt...It is a new strategy to immobilize cells on the inner wall of a capillary column and use affinity capillary electrophoresis（ACE） to study receptor-ligand interactions or to screen natural products and compounds synthesized by combinatorial chemistry. In this paper, we developed a new method of immobilizing HEK293 cells on the inner wall of a capillary column. Four important experimental conditions were optimized, including cell injection density, PLL concentration, cell culturing time and sterile processing method. Immobilized cell-coated capillary columns prepared under the optimized experimental conditions exhibited good uniformity, stability and durability, which were suitable for capillary electrophoresis. The method could also be used to immobilize HEK293 cells over-expressing certain membrane receptors on the inner wall of a capillary. In this way, cell-coated capillary columns could be applied to ACE drug screening targeting certain membrane proteins.展开更多
Aim To study the chromatographis beheviors of three new cinnamyl cyclodextrin derivative stationary phases. Mehtods Three new cinnamyl β-cyclodextrins, heptakis-(2, 6-di-O-cinnamyl-3-O-methyl)-β-CD, heptakis-(2, 6-...Aim To study the chromatographis beheviors of three new cinnamyl cyclodextrin derivative stationary phases. Mehtods Three new cinnamyl β-cyclodextrins, heptakis-(2, 6-di-O-cinnamyl-3-O-methyl)-β-CD, heptakis-(2, 6-di-O-cinnamyl-3-O-acetyl-)-β-CD and heptakis-2, 6-di-O-cirinamyl-3-O-trifluoroacetyl)-β-CD were synthesized and coatal on fused-silica capillary columns . Results The new stationary phases have better thermal stability, good column efficiency and excellent mpaxation power for some sutstituted benzene positional isomers. It was found that the introduction of cinnamyl groups has a significant effect on these stationary phases. Conclusion There new subetituted β-CD compounds are very suitable to be ed as gas chromatographic stationary phases.展开更多
Stationary shoulder friction stir lap welding(SSFSLW) was employed to weld 2024 aluminum alloy. A coupled Eulerian-Lagrangian(CEL) model was developed to investigate the lap interface behavior during SSFSLW. Numerical...Stationary shoulder friction stir lap welding(SSFSLW) was employed to weld 2024 aluminum alloy. A coupled Eulerian-Lagrangian(CEL) model was developed to investigate the lap interface behavior during SSFSLW. Numerical results of material movement and equivalent plastic strain were in good agreement with the experimental work. With increasing welding speed, the distances from the hook tip to the top surface of the upper workpiece on the retreating side(RS) and the advancing side(AS) increase, while the distance between two wave-shaped alclads decreases. A symmetric interface bending is observed on the AS and the RS during plunging, while the interface bending on the AS is bigger than that on the RS during welding. The peak temperature of the interface on the AS is higher than that on the RS. The equivalent plastic strain gradually increases as the distance to the weld center decreases, and its peak value is obtained near the bottom of the weld.展开更多
Aim To study the chromatographic behaviors of two dipentyl cyclodextrin derivative stationary phases. Methods Two new β-cyclodextrin derivatives, heptakis-[2, 6-di-O-pentyl-3-O-(4-nitrobenzyl)] -β-CD and heptakis-[...Aim To study the chromatographic behaviors of two dipentyl cyclodextrin derivative stationary phases. Methods Two new β-cyclodextrin derivatives, heptakis-[2, 6-di-O-pentyl-3-O-(4-nitrobenzyl)] -β-CD and heptakis-[2, 6-di-O-pentyl-3 -O-(5 -hexenyl)]-β-CD, were synthesized and coatal on fed-silica capillary columns. The chromatographic behaviors of the columns were characterized . Results It was found that the she, polarity, and aromatic property of the substituted group at the 3-position of heptakis-(2, 6 - di - O - pentyl) - β - cyclodextrins greatly influenced their chromatographic properties and separation ability. The introduction of aromatic group or a group containing a double-bond may bring π-π interactions between the host and vip molecules, and therefore increases the separation ability of the β-CDs for substituted benzene isomers. Conclusion The new substituted β-CD compounds are very suitable for being used as gas chromatogaphic stationary phases.展开更多
Single-walled carbon nanotubes（SWNTs） have a high adsorption ability and nanoscale interactions. Cellulose trisphenylcarbamates possess high enantioseparation ability in high-performance liquid chromatography（HPLC...Single-walled carbon nanotubes（SWNTs） have a high adsorption ability and nanoscale interactions. Cellulose trisphenylcarbamates possess high enantioseparation ability in high-performance liquid chromatography（HPLC）. Single-walled carbon nanotubes mixed with cellulose trisphenylcarbamate are coated on the silica gel as chiral stationary phases and higher enantioseparation factors are obtained. After a single-walled carbon nanotube is linked to the 6-pesition of cellulose 2,3-bisphenylcarbamate, its enantioseparation resolution increases compared to that of the cellulose trisphenylcarbamate. It is the first time that SWNTs have been applied to enantioseparation. The results indicate that the single-walled carbon nanotubes are good promoters of chiral recognition. This method can be used to improve the enantioseparation efficiency of the polysaccharide chiral stationary phases.展开更多
A class of stationary models of singular stochastic control has been studied, in which the state is extended to solution of a class of S.D.E. from Wiener process. The existence of optimal control has been proved in al...A class of stationary models of singular stochastic control has been studied, in which the state is extended to solution of a class of S.D.E. from Wiener process. The existence of optimal control has been proved in all cases under some weaker conditions, and the structure of optimal control may be characterized.展开更多
The current development of precision plastic injection molding machines mainly focuses on how to save material and improve precision, but the two aims contradict each other. For a clamp unit, clamping precision improv...The current development of precision plastic injection molding machines mainly focuses on how to save material and improve precision, but the two aims contradict each other. For a clamp unit, clamping precision improving depends on the design quality of the stationary platen. Compared with the parametric design of stationary platen, structural scheme design could obtain the optimization model with double objectives and multi-constraints. In this paper, a SE-160 precision plastic injection molding machine with 1600 kN clamping force is selected as the subject in the case study. During the motion of mold closing and opening, the stationary platen of SE-160 is subjected to a cyclic loading, which would cause the fatigue rupture of the tie bars in periodically long term operations. In order to reduce the deflection of the stationary platen, the FEA method is introduced to optimize the structure of the stationary platen. Firstly, an optimal topology model is established by variable density method. Then, structural topology optimizations of the stationary platen are done with the removable material from 50%, 60% to 70%. Secondly, the other two recommended optimization schemes are given and compared with the original structure. The result of performances comparison shows that the scheme II of the platen is the best one. By choosing the best alternative, the volume and the local maximal stress of the platen could be decreased, corresponding to cost-saving material and better mechanical properties. This paper proposes a structural optimization design scheme, which can save the material as well as improve the clamping precision of the precision plastic injection molding machine.展开更多
The motion of the self-gravitational gaseous stars can be described by the Euler-Poisson equations. The main purpose of this paper is concerned with the existence of stationary solutions of Euler-Poisson equations for...The motion of the self-gravitational gaseous stars can be described by the Euler-Poisson equations. The main purpose of this paper is concerned with the existence of stationary solutions of Euler-Poisson equations for some velocity fields and entropy functions that solve the conservation of mass and energy. Under different restriction to the strength of velocity field, we get the existence and multiplicity of the stationary solutions of Euler-Poisson system.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22174067,22204078,22374077,and 22474059)the Natural Science Foundation of Jiangsu Province of China(No.BK20220370)+2 种基金Jiangsu Provincial Department of Education(No.22KJB150009)Jiangsu Association for Science and Technology(No.TJ-2023-076)the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘For chromatographic separation,the reasonable modulation of stationary phases is the key factor to achieve high separation performance.We proposed that developing MOF stationary phases through precisely modulating the thermodynamic interactions between MOFs and analytes is conducive to improving the separation resolution.MIL-125,MIL-125-NH_(2),MIL-143-BTB,and MIL-143-TATB were developed as stationary phases with the careful modulation of organic ligands.MIL-125-NH_(2)and MIL-143-TATB coated columns exhibited much better separation performance than their counterparts,MIL-125 and MIL-143-BTB,respectively.The investigation of the separation mechanism indicated that thermodynamic interaction,rather than kinetic diffusion,was responsible for the separation improvement.MIL-125-NH_(2)and MIL-143-TATB provided stronger and distinguishable interactions with targets than corresponding MIL-125 and MIL-143-BTB,respectively,resulting in enhanced separation performance.This work demonstrates a guide to improving the separation performance of MOF stationary phases by increasing the thermodynamic interactions between MOFs and analytes.
基金Innovation Groups of Basic Research in Gansu Province(No.23JRRA570)。
文摘An ionic liquid assisted hydrogel modified silica was synthesized using a one-pot polymerization and physical coating technique and subsequently applied to mixed-mode liquid chromatography.Analytical techniques,including Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),and elemental analysis,etc.,confirmed the successful prepared of this innovative stationary phase.The unique combination of amide,long alkyl chain,and imidazole ring in the hydrogel coating enables the stationary phase to function effectively in hydrophilic/reversed-phase/ion exchange liquid chromatography.Notably,the stationary phase exhibited superior separation performance owing to the synergistic effect of the ionic liquid and hydrogel.This was particularly evident when analyzing various analytes such as organic acids,nucleosides/bases,polycyclic aromatic hydrocarbons(PAHs)and anions.Furthermore,under our operating conditions,an excellent column efficiency of 53,642.9 plates/m was achieved for theobromine.In summary,we have proposed a straightforward strategy to enhance the separation performance of hydrogel coatings in liquid chromatography,thereby broadening the potential applications of hydrogels in the field of separation.
基金supported by the National Natural Science Foundation of China(Nos.52273002 and 52333008)the funding of Boya Postdoctoral Fellowship at Peking University,BMS Junior Fellow Program and the National Funding Program for Postdoctoral Researchers(No.GZC20230031).
文摘A series of optically active copolymers with various feed ratios have been synthesized through helix-sense-selective copolymerization catalyzed by[Rh(norbornadiene)Cl]2-triethylamine.This process involves two proline-derived acetylene monomers,(S)-N-(4-chlorophenyl)carbamoyl-2-ethynyl pyrrolidine(MCl)and(S)-N-(tert-butoxycarbonyl)-2-ethynyl pyrrolidine,followed by acidic deprotection and neutralization.These copolymers adopt helical conformations with a preferred handedness,as demonstrated by nuclear magnetic resonance spectroscopy and a series of spectroscopic analyses.The chiroptical activity intensity of copolymer has been found to increase with MCl content.Consequently,the enantioseparation capabilities of copolymers containing 95 mol%,90 mol%,and 85 mol%MCl units have been assessed as chiral stationary phases in high-performance liquid chromatography because of their good chiroptical activities.These chiral stationary phases effectively enantioseparate racemic alcohols,sulfoxides,amides,and metal complexes.Notably,the copolymer with 90 mol%MCl shows superior chiral recognition ability,especially for 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethanol(α=1.19)and 4-methylbenzenesulfinamide(α=1.47).Insights from molecular dynamic simulation and autodock analysis indicate that hydrogen bonding andπ-πstacking interactions between the chiral stationary phases and enantiomers play a key role for successful chiral separation.Our contribution not only demonstrates the importance of hydrogen bonding donor and copolymer chiroptical activity of chiral stationary phases for chiral resolution,but will also provide valuable insights for the future development of novel stationary phases.
基金the National Natural Science Foundation of China(No.22274021)Natural Science Foundation of Fujian Province(No.2022J01535)for financial support。
文摘Covalent organic frameworks(COFs)have demonstrated great potential in chromatographic separation because of unique structure and superior performance.Herein,single-crystal three-dimensional(3D)COFs with regular morphology,good monodispersity and high specific surface area,were used as a stationary phase for high-performance liquid chromatography(HPLC).The single-crystal 3D COFs packed column not only exhibits high efficiency in separating hydrophobic molecules involving substituted benzenes,halogenated benzenes,halogenated nitrobenzenes,aromatic amines,aromatic hydrocarbons(PAHs)and phthalate esters(PAEs),but also achieves baseline separation of acenaphthene and acenaphthylene with similar physical and chemical properties as well as environmental pollutants,which cannot be quickly separated on commercial C18 column and a polycrystalline 3D COFs packed column.Especially,the column efficiency of 17303-24255 plates/m was obtained for PAEs,and the resolution values for acenaphthene and acenaphthylene,and carbamazepine(CBZ)and carbamazepine-10,11-epoxide(CBZEP)were 1.7and 2.2,respectively.This successful application not only confirmed the great potential of the singlecrystal 3D COFs in HPLC separation of the organic molecules,but also facilitates the application of COFs in separation science.
文摘By combining multiscale stationary wavelet analysis with fuzzy c-means, a robust edge detection algorithm is presented. Based on the translation invafiance built in multiscale stationary wavelet transform, components in different transformed sub-images corresponding to a pixel are employed to form a feature vector of the pixel. All the feature vectors are classified with unsupervised fuzzy c-means to segment the image, and then the edge pixels are checked out by the Canny detector. A series of images contaminated with different intensive Gaussian noises are used to test the novel algorithm. Experiments show that fairly precise edges can be checked out robustly from those images with fairly intensive noise by the proposed algorithm.
文摘A new capillary gas chromatography stationary phase, monokis (2,6 di O benzyl 3 O propyl (3’)) hexakis(2,6 di O benzyl 3 O methyl) β CD bonded polysiloxane, was synthesized. It exhibited separation abilities to disubstituted benzene isomers and some chiral solutes. It was also found that the polarity of CD derivatives can be lowered both by chemically bonding it to polysiloxane and by diluting it in polysiloxane. The separation abilities of the polysiloxane anchored CDs (SP CD) are higher than that of the unbonded CDs (S CD) and the diluted S CD at lower column temperature. Hydrosilylation reaction is one of the best methods to lower the operating temperature of CDs.
基金supported by the National Natural Science Foundation of China (Grant No.40574052)
文摘In the literature,stationary phase analysis of Kirchhoff-type demigrated fields is carried out mainly under the following two conditions：（1） The considered isochrone and the target reflector are tangential to each other;（2） The spatial duration of the wavelet of the depthmigrated image is short.For the isochrones that are not tangential to the target reflector and for the depth-migrated images that have a large spatial duration,the published stationary phase equation for the demigrated field will become invalid.For performing the stationary phase analysis of the Kirchhoff-type demigrated field under the conditions that the considered isochrone and the target reflector are not tangential to each other and that the spatial duration of the wavelet of the depth-migrated image is not short（the general conditions）,I derive the formulas for the factors appearing in the stationary phase formula in two dimensions,from which I find that for different isochrones the horizontal coordinates of the stationary point of the depth difference function are different.Also,the equation for the Kirchhoff-type demigrated field consists of two parts.One is the true-amplitude demigrated signal and the other is the amplitude distortion factor.From these facts the following two conclusions can be drawn：（1） A demigrated signal is composed of many depth-migrated images and one depth-migrated image trace provides only one sample to the demigrated signal;and（2） The amplitude distortion effect is an effect inherent in the Kirchhoff-type demigration and cannot be eliminated during demigration.If this effect should be eliminated,one should do an amplitude correction after demigration.
基金Guangzhou mega Projects of Science Research in 2009(Grant No.2009A1-E011-7)
文摘Effective enantioseparation of Naftopidil and its derivatives by HPLC was accomplished using several different polysaccharide-based chiral stationary phases（CSPs）.In normal-phase mode,the compounds were eluted on four coated-and two immobilized-columns with the mixture of n-hexane,isopropanol and diethylamine（DEA）.Polysaccharide tris（3,5- dimethylphenyl carbamate） was shown to be the best enantiomer selector.In addition,the immobilized column packed with Chiralpak IA or IB was applied under polar-organic and reversed-phase conditions,both of which exhibited excellent enantioselectivity for Naftopidil and its derivatives.Furthermore,the underlying possible chiral recognition mechanisms were discussed.
基金Science and Technology Program of Guangzhou City(Grant No.2010U1-E0531-2)
文摘Six newly synthesized racemic 1-（substituted phenyl）-4-[3-（indole-4-yl-oxy）-2-hydroxypropyl]-piperazine 1-6 were successfully resolved by carbon dioxide supercritical fluid chromatography （SFC） on an analytical scale column packed with immobilized polysaccharide-based chiral stationary phases （CSPs）. We found that separation on the Chiralpak IA CSP was superior to the other two immobilized CSPs （Chiralpak IB and Chiralpak IC）, and isopropanol （IPA） was a superior modifier compared to the other five solvents including ethanol, methanol, tetrahydrofuran, acetonitrile and dichloromethane. The effects of organic modifier composition, back pressure, and column temperature for enantioseparation of all six compounds were studied. Of the physical parameters studied, modifier composition had the greatest impact on retention. Changing temperature generally had less impact on retention but produced the greatest selectivity changes. The optimum condition was found as follows： Chiralpak IA column, column temperature 35 ~C, back pressure 120 bar, 35% IPA containing 0.1% diethylamine （v/v） in mobile phase, flow rate of mobile phase 3.0 mL/min, UV detection 283 nm. Separation of all six racemic compounds was completed within 10 rain and excellent resolution was obtained. Thus, SFC was found to be the methodology of choice for resolving the enantiomers of this class of compounds.
基金supported by the National Natural Science Foundation of China (Grant No. 1057411)the Foundation for Researching Group by Beijing Normal Universitythe Foundation for Outstanding Doctoral Dissertation by Beijing Normal University
文摘This paper investigates the dynamical properties of nonstationary solutions in one-dimensional two-component Bose-Einstein condensates. It gives three kinds of stationary solutions to this model and develops a general method of constructing nonstationary solutions. It obtains the unique features about general evolution and soliton evolution of nonstationary solutions in this model.
文摘During the past research, Direct Sequence (DS) Spread Spectrum (SS) signal is modeled as stationary in most cases. Cyclostationary model for SS signal is introduced in this letter. Compared with stationary model, cyclostationary model can preserve more information,and its advantages are shown through example.
文摘This study aims at establishing if climate change exists in the Niger Delta environment using non-stationary rainfall Intensity-Duration-Frequency (IDF) modelling incorporating time-variant parameters. To compute the intensity levels, the open-access R-studio software was used based on the General Extreme Value (GEV) distribution function. Among the four linear parameter models adopted for integrating time as a covariate, the fourth linear model incorporating scale and location with the shape function constant produced the least corrected Akaike Information Criteria (AICc), varying between 306.191 to 101.497 for 15 and 1440 minutes, respectively, selected for calibration of the GEV distribution equation. The non-stationary intensities yielded higher values above those of stationary models, proving that the assumption of stationary IDF models underestimated extreme events. The difference of 13.71 mm/hr (22.71%) to 14.26 mm/hr (17.0%) intensities implies an underestimation of the peak flood from a stationary IDF curve. The statistical difference at a 95% confidence level between stationary and non-stationary models was significant, confirming evidence of climatic change influenced by time-variant parameters. Consequently, emphasis should be on applying shorter-duration storms for design purposes occurring with higher intensities to help reduce the flood risk and resultant infrastructural failures.
基金The National Natural Science Foundation(Grant No.81373372)Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130001110059)
文摘It is a new strategy to immobilize cells on the inner wall of a capillary column and use affinity capillary electrophoresis（ACE） to study receptor-ligand interactions or to screen natural products and compounds synthesized by combinatorial chemistry. In this paper, we developed a new method of immobilizing HEK293 cells on the inner wall of a capillary column. Four important experimental conditions were optimized, including cell injection density, PLL concentration, cell culturing time and sterile processing method. Immobilized cell-coated capillary columns prepared under the optimized experimental conditions exhibited good uniformity, stability and durability, which were suitable for capillary electrophoresis. The method could also be used to immobilize HEK293 cells over-expressing certain membrane receptors on the inner wall of a capillary. In this way, cell-coated capillary columns could be applied to ACE drug screening targeting certain membrane proteins.
文摘Aim To study the chromatographis beheviors of three new cinnamyl cyclodextrin derivative stationary phases. Mehtods Three new cinnamyl β-cyclodextrins, heptakis-(2, 6-di-O-cinnamyl-3-O-methyl)-β-CD, heptakis-(2, 6-di-O-cinnamyl-3-O-acetyl-)-β-CD and heptakis-2, 6-di-O-cirinamyl-3-O-trifluoroacetyl)-β-CD were synthesized and coatal on fused-silica capillary columns . Results The new stationary phases have better thermal stability, good column efficiency and excellent mpaxation power for some sutstituted benzene positional isomers. It was found that the introduction of cinnamyl groups has a significant effect on these stationary phases. Conclusion There new subetituted β-CD compounds are very suitable to be ed as gas chromatographic stationary phases.
基金supported financially by the National Natural Science Foundation of China(No.51574196)the Fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201722)
文摘Stationary shoulder friction stir lap welding(SSFSLW) was employed to weld 2024 aluminum alloy. A coupled Eulerian-Lagrangian(CEL) model was developed to investigate the lap interface behavior during SSFSLW. Numerical results of material movement and equivalent plastic strain were in good agreement with the experimental work. With increasing welding speed, the distances from the hook tip to the top surface of the upper workpiece on the retreating side(RS) and the advancing side(AS) increase, while the distance between two wave-shaped alclads decreases. A symmetric interface bending is observed on the AS and the RS during plunging, while the interface bending on the AS is bigger than that on the RS during welding. The peak temperature of the interface on the AS is higher than that on the RS. The equivalent plastic strain gradually increases as the distance to the weld center decreases, and its peak value is obtained near the bottom of the weld.
文摘Aim To study the chromatographic behaviors of two dipentyl cyclodextrin derivative stationary phases. Methods Two new β-cyclodextrin derivatives, heptakis-[2, 6-di-O-pentyl-3-O-(4-nitrobenzyl)] -β-CD and heptakis-[2, 6-di-O-pentyl-3 -O-(5 -hexenyl)]-β-CD, were synthesized and coatal on fed-silica capillary columns. The chromatographic behaviors of the columns were characterized . Results It was found that the she, polarity, and aromatic property of the substituted group at the 3-position of heptakis-(2, 6 - di - O - pentyl) - β - cyclodextrins greatly influenced their chromatographic properties and separation ability. The introduction of aromatic group or a group containing a double-bond may bring π-π interactions between the host and vip molecules, and therefore increases the separation ability of the β-CDs for substituted benzene isomers. Conclusion The new substituted β-CD compounds are very suitable for being used as gas chromatogaphic stationary phases.
基金Supported by the National Natural Science Foundation of China(No.30160092)the Natural Science Foundation of Yunnan Province,China(No.2005E0006Z).
文摘Single-walled carbon nanotubes（SWNTs） have a high adsorption ability and nanoscale interactions. Cellulose trisphenylcarbamates possess high enantioseparation ability in high-performance liquid chromatography（HPLC）. Single-walled carbon nanotubes mixed with cellulose trisphenylcarbamate are coated on the silica gel as chiral stationary phases and higher enantioseparation factors are obtained. After a single-walled carbon nanotube is linked to the 6-pesition of cellulose 2,3-bisphenylcarbamate, its enantioseparation resolution increases compared to that of the cellulose trisphenylcarbamate. It is the first time that SWNTs have been applied to enantioseparation. The results indicate that the single-walled carbon nanotubes are good promoters of chiral recognition. This method can be used to improve the enantioseparation efficiency of the polysaccharide chiral stationary phases.
基金Supported by the National Science Foundation of China.
文摘A class of stationary models of singular stochastic control has been studied, in which the state is extended to solution of a class of S.D.E. from Wiener process. The existence of optimal control has been proved in all cases under some weaker conditions, and the structure of optimal control may be characterized.
基金Supported by National Natural Science Foundation of China(Grant No.51205350)Hong Kong Scholars Program of China(Grant No.XJ2013015)Zhejiang Provincial Research Program of Public Welfare Technology Application of China(Grant No.2013C31027)
文摘The current development of precision plastic injection molding machines mainly focuses on how to save material and improve precision, but the two aims contradict each other. For a clamp unit, clamping precision improving depends on the design quality of the stationary platen. Compared with the parametric design of stationary platen, structural scheme design could obtain the optimization model with double objectives and multi-constraints. In this paper, a SE-160 precision plastic injection molding machine with 1600 kN clamping force is selected as the subject in the case study. During the motion of mold closing and opening, the stationary platen of SE-160 is subjected to a cyclic loading, which would cause the fatigue rupture of the tie bars in periodically long term operations. In order to reduce the deflection of the stationary platen, the FEA method is introduced to optimize the structure of the stationary platen. Firstly, an optimal topology model is established by variable density method. Then, structural topology optimizations of the stationary platen are done with the removable material from 50%, 60% to 70%. Secondly, the other two recommended optimization schemes are given and compared with the original structure. The result of performances comparison shows that the scheme II of the platen is the best one. By choosing the best alternative, the volume and the local maximal stress of the platen could be decreased, corresponding to cost-saving material and better mechanical properties. This paper proposes a structural optimization design scheme, which can save the material as well as improve the clamping precision of the precision plastic injection molding machine.
基金supported by NSFC (10631030, 11071094)the fund of CCNU for Ph.D students (2009021)
文摘The motion of the self-gravitational gaseous stars can be described by the Euler-Poisson equations. The main purpose of this paper is concerned with the existence of stationary solutions of Euler-Poisson equations for some velocity fields and entropy functions that solve the conservation of mass and energy. Under different restriction to the strength of velocity field, we get the existence and multiplicity of the stationary solutions of Euler-Poisson system.
