To understand the gene-based biological processes in-depth,the single-molecule real-time sequencing has drawn increasing attention with promoted by the Human Genome Project.Herein,a set of newly designed canonical flu...To understand the gene-based biological processes in-depth,the single-molecule real-time sequencing has drawn increasing attention with promoted by the Human Genome Project.Herein,a set of newly designed canonical fluorescent bases(A_(y),tC,G_(b),T_(p))are proposed for four-color DNA sequencing.These quasi-intrinsic probes are derived from the fluorophore replacement and ring expansion on natural bases,which still keep the pyrimidine or purine underlying skeleton and Watson–Crick hydrogen bonding face to allow minimal perturbation to the native DNA duplex.More importantly,these nucleobase analogues possess red-shifted absorption and efficient photoluminescence due to the enhancedπ-conjugation in character.Meanwhile,the four analogues could generate distinct emission wavelength(Δλ~50 nm)for real-time sequencing.To assess the biological employment of the proposed biosensors,the effects of base pairing and linking deoxyribose are also considered.展开更多
Rheumatoid arthritis(RA)is a systemic autoimmune disease that is primarily manifested as synovitis and polyarticular opacity and typically leads to serious joint damage and irreversible disability,thus adversely affec...Rheumatoid arthritis(RA)is a systemic autoimmune disease that is primarily manifested as synovitis and polyarticular opacity and typically leads to serious joint damage and irreversible disability,thus adversely affecting locomotion ability and life quality.Consequently,good prognosis heavily relies on the early diagnosis and effective therapeutic monitoring of RA.Activatable fluorescent probes play vital roles in the detection and imaging of biomarkers for disease diagnosis and in vivo imaging.Herein,we review the fluorescent probes developed for the detection and imaging of RA biomarkers,namely reactive oxygen/nitrogen species(hypochlorous acid,peroxynitrite,hydroxyl radical,nitroxyl),pH,and cysteine,and address the related challenges and prospects to inspire the design of novel fluorescent probes and the improvement of their performance in RA studies.展开更多
Parameters of hydrogen plasma in a miniature Penning discharge ion source, including the electron temperature and the electron density, were measured by using double probes. The results indicate that the electron dens...Parameters of hydrogen plasma in a miniature Penning discharge ion source, including the electron temperature and the electron density, were measured by using double probes. The results indicate that the electron density increases and the electron temperature decreases with the increase in gas pressure and the discharge current. The electron temperature is about 5 - 9 eV and the electron density is 6.0× 10^13 ～ 1.2 × 10^14 m^-3 while the discharge current is in a range of 50 - 120 μA.展开更多
Generalized ptychography is established with diverse probes,which not only extend the core spirit of ptychography that is the overlapping of neighboring probes,but also enhance the imaging quality.We find that in one ...Generalized ptychography is established with diverse probes,which not only extend the core spirit of ptychography that is the overlapping of neighboring probes,but also enhance the imaging quality.We find that in one of suggested configurations with visible light,the performances of two types of diversified probes are improved in comparison with the traditional circular probes.This may open up some new possibilities of ptychographic imaging.展开更多
We develop superconducting quantum interference device(SQUID)probes based on 3D nano-bridge junctions for the scanning SQUID microscopy.The use of these nano-bridge junctions enables imaging in the presence of a high ...We develop superconducting quantum interference device(SQUID)probes based on 3D nano-bridge junctions for the scanning SQUID microscopy.The use of these nano-bridge junctions enables imaging in the presence of a high magnetic field.Conventionally,a superconducting ground layer has been employed for better magnetic shielding.In our study,we prepare a number of scanning SQUID probes with and without a ground layer to evaluate their performance in external magnetic fields.The devices show the improved magnetic modulation up to 1.4 T.It is found that the ground layer reduces the inductance,and increases the modulation depth and symmetricity of the gradiometer design in the absence of the field.However,the layer is not compatible with the use of the scanning SQUID probe in the field because it decreases its working field range.Moreover,by adding the layer,the mutual inductance between the feedback coil and the SQUID also decreases linearly as a function of the field.展开更多
This study presents the Langmuir and Faraday probe measurements conducted to determine the plume characteristics of the BUSTLab microwave electrothermal thruster(MET).The thruster,designed to operate at 2.45 GHz frequ...This study presents the Langmuir and Faraday probe measurements conducted to determine the plume characteristics of the BUSTLab microwave electrothermal thruster(MET).The thruster,designed to operate at 2.45 GHz frequency,is run with helium,argon and nitrogen gases as the propellant.For the measurements,the propellant volume flow rate and the delivered microwave power levels are varied.Experiments with nitrogen gas revealed certain operation regimes where a very luminous plume is observed.With the use of in-house-built Langmuir probes and a Faraday probe with guard ring,thruster plume electron temperature,plasma density and ion current density values are measured,and the results are presented.The measurements show that MET thruster plume effects on spacecraft will likely be similar to those of the arcjet plume.It is observed that the measured plume ion flux levels are very low for the high volume flow rates used for the operation of this thruster.展开更多
To improve two-photon absorption(TPA)response of a newly synthesized probe,a series of ratiometric two-photon fluorescent Zn^(2+) sensors based on quinoline and DPA moieties have been designed.The one-photon absorptio...To improve two-photon absorption(TPA)response of a newly synthesized probe,a series of ratiometric two-photon fluorescent Zn^(2+) sensors based on quinoline and DPA moieties have been designed.The one-photon absorption,TPA,and emission properties of the experimental and designed probes before and after coordination with Zn^(2+) are investigated employing the density functional theory in combination with response functions.The design consists of two levels.In the first level of design,five probes are constructed through using several electron acceptors or donors to increase accepting or donating ability of the fluorophores.It shows that all the designed probes have stronger TPA intensities at longer wavelengths with respect to the experimental probe because of the increased intra-molecular charge transfer.Moreover,it is found that the probe 4 built by adding an acyl unit has the largest TPA cross section among the designed structures due to the form of longer conjugated length and more linear backbone.One dimethylamino terminal attached along the skeleton can improve TPA intensity more efficiently than two side amino groups.Therefore,in the second level of design,a new probe 7 is formed by both an acyl unit and a dimethylamino terminal.It exhibits that the TPA cross sections of probe 7 and its zinc complex increase dramatically.Furthermore,the fluorescence quantum yields of the designed probes4 and 7 are calculated in a new way,which makes use of the relation between the computed difference of dipole moment and the measured fluorescence quantum yield.The result shows that our design also improves the fluorescence quantum yield considerably.All in all,the designed probes 4 and 7 not only possess enhanced TPA intensities but also have large differences of emission wavelength upon Zn^(2+) coordination and strong fluorescence intensity,which demonstrates that they are potential ratiometric two-photon fluorescent probes.展开更多
Limited particle transit time is one of several limiting factors which determine the maximum temporal resolution of a Langmuir probe.In this work,we have revisited the known fast sweep Langmuir probe techniques in a u...Limited particle transit time is one of several limiting factors which determine the maximum temporal resolution of a Langmuir probe.In this work,we have revisited the known fast sweep Langmuir probe techniques in a uniform,quiescent multi-dipole confined hot cathode discharge with two operation scenarios:one in which the probe sweeping frequency fsweepis much lower than the ion plasma frequency fpi,another one where fsweepis much greater than fpi,respectively.This allows investigation into the effect of limited ion-motion on I–V traces.Serious distortions of I–V traces at high frequencies,previously claimed to be an ion-motion limitation effect,were not found unless shunt resistance is sufficiently high,despite a f;/f;ratio of~3.On the other hand,evidences of sheath capacitance on the I–V traces have been observed.Distortions of I–V traces qualitatively agree with predictions of sheath capacitance response to the sweeping voltage.Additionally,techniques in fast sweep Langmuir probe are briefly discussed.The comparison between the high-speed dual Langmuir probe(HDLP)and the single probe setup shows that the capacitive response can be removed via subtracting a leakage current for the single probe setup almost as effectively as using the HDLP setup,but the HDLP setup does remain advantageous in its facilitation of better recovery of weak current signal commonly in low density plasma.展开更多
Response theory is used to investigate one- and two-photon absorption（TPA） as well as the emission properties of a series of potential zinc ion and pH sensitive materials containing 2-（2＇-hydroxyphenyl）benzoxazol...Response theory is used to investigate one- and two-photon absorption（TPA） as well as the emission properties of a series of potential zinc ion and pH sensitive materials containing 2-（2＇-hydroxyphenyl）benzoxazole（HPBO） end groups.Special emphasis is placed on the evolution of their optical properties upon combining with zinc ions or deprotonation.Our calculated results indicate that upon combining with zinc ions or deprotonation,these HPBO derivatives show drastic changes in their one-photon absorption（OPA）,emission,and TPA properties.Moreover,the mechanisms of the probes are analyzed and found to be an intramolecular charge transfer.These compounds are thus proved to be excellent candidates for two-photon fluorescent zinc and pH probes.展开更多
An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a te...An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.展开更多
Two pairs of high-frequency magnetic probes were installed in the Large Helical Device （LHD）. During the injection of a perpendicular neutral beam, ion cyclotron emissions （ICEs） with the fundamental frequency cor...Two pairs of high-frequency magnetic probes were installed in the Large Helical Device （LHD）. During the injection of a perpendicular neutral beam, ion cyclotron emissions （ICEs） with the fundamental frequency corresponding to the ion cyclotron frequency at the plasma edge were detected, which are the same type of ICE as measured with the former spare ion cyclotron range of frequencies （ICRF） heating antennas. This type of ICE was further investigated with regard to the phase and intensity of signals. Another type of ICE was found in the LHD, and these ICEs were synchronized with bursts of toroidicity induced Alfv^n eigenmodes （TAE） and the rise of intensity of lost ion flux. Therefore the source of these ICEs was thought to be the particles transferred from the core to the outer region of plasma by the TAE bursts. The frequency of ICEs induced by the TAE bursts increases linearly with the magnetic field strength, since the ion cyclotron frequency increases with the magnetic field strength.展开更多
The plasma shape and other paremeters such as /3P, li is important for the tokamak deveice where the plasma has a non-circular cross-section of sufficient elongation. The measuered signals of magnetic probes and flux ...The plasma shape and other paremeters such as /3P, li is important for the tokamak deveice where the plasma has a non-circular cross-section of sufficient elongation. The measuered signals of magnetic probes and flux loops are used to reconstruct the plasma shape and the current profile in device operation and plasma shape feed back control system. So the number and positions of magnetic probes and flux loops provides the basis of the plasma reconstruction. This paper instroduce how to use EFIT code (equilibrium fitting code) to determine the number and positions of the magnetic probes and flux loops. The simulation result is given also.展开更多
Mercury is a threatening pollutant in food,herein,we developed a Tb^(3+)-nucleic acid probe-based label-free assay for mix-and-read,rapid detection of mercury pollution.The assay utilized the feature of light-up fluor...Mercury is a threatening pollutant in food,herein,we developed a Tb^(3+)-nucleic acid probe-based label-free assay for mix-and-read,rapid detection of mercury pollution.The assay utilized the feature of light-up fluorescence of terbium ions(Tb^(3+))via binding with single-strand DNA.Mercury ion,Hg^(2+)induced thymine(T)-rich DNA strand to form a double-strand structure(T-Hg^(2+)-T),thus leading to fluorescence reduction.Based on the principle,Hg^(2+)can be quantified based on the fluorescence of Tb^(3+),the limit of detection was 0.0689μmol/L and the linear range was 0.1-6.0μmol/L.Due to the specificity of T-Hg^(2+)-T artificial base pair,the assay could distinguish Hg^(2+)from other metal ions.The recovery rate was ranged in 98.71%-101.34%for detecting mercury pollution in three food samples.The assay is low-cost,separation-free and mix-to-read,thus was a competitive tool for detection of mercury pollution to ensure food safety.展开更多
The double-coupled microwave resonance probe(DMRP)based on the hairpin probe is proposed for diagnosing atmospheric plasma jet(ne<1017 m-3).In this work,the resonance characteristics of DMRP are investigated by num...The double-coupled microwave resonance probe(DMRP)based on the hairpin probe is proposed for diagnosing atmospheric plasma jet(ne<1017 m-3).In this work,the resonance characteristics of DMRP are investigated by numerical simulation.It shows that two resonance peaks on the reflectance spectrum can be observed,and influenced significantly by some parameters,such as the probe separation,the distance to the handheld radio frequency atmospheric pressure glow discharge plasma jet(RF-APGDPJ)and the plasma electron density less than 1017 m-3.Based on two resonance modes of DMRP,the electron densities in the afterglow of RF-APGDPJ at the different rf powers and helium flow rates are diagnosed experimentally by matching the change of FWHM(Df1-Df1,airand Df2-Df2,air)measured by vector network analyzer with the simulated relation between the FWHM changes and the plasma density.展开更多
The properties of one-photon absorption（OPA）, emission and two-photon absorption（TPA） of a di-2-picolylaminebased zinc ion sensor are investigated by employing the density functional theory in combination with res...The properties of one-photon absorption（OPA）, emission and two-photon absorption（TPA） of a di-2-picolylaminebased zinc ion sensor are investigated by employing the density functional theory in combination with response functions.The responsive mechanism is explored. It is found that the calculated OPA and TPA properties are quite consistent with experimental data. Because the intra-molecular charge transfer（ICT） increases upon zinc ion binding, the TPA intensity is enhanced dramatically. According to the model sensor, we design a series of zinc ion probes which differ by conjugation center, acceptor and donor moieties. The properties of OPA, emission and TPA of the designed molecules are calculated at the same computational level. Our results demonstrate that the OPA and emission wavelengths of the designed probes have large red-shifts after zinc ions have been bound. Comparing with the model sensor, the TPA intensities of the designed probes are enhanced significantly and the absorption positions are red-shifted to longer wavelength range. Furthermore, the TPA intensity can be improved greatly upon zinc ion binding due to the increased ICT mechanism. These compounds are potential excellent candidates for two-photon fluorescent zinc ion probes.展开更多
In this article,the effect of the finite conductive surface area of a satellite on the use of satellite-based Langmuir probes is reviewed in light of the basic theory of asymmetric double Langmuir probes(ADLPs).Recent...In this article,the effect of the finite conductive surface area of a satellite on the use of satellite-based Langmuir probes is reviewed in light of the basic theory of asymmetric double Langmuir probes(ADLPs).Recent theoretical and experimental studies have discussed electron sheath/presheath formation and the electron Bohm criterion along with their implications for satellite-based Langmuir probes.The effects predicted by the latest theory of the electron Bohm criterion were not experimentally observed and the experimental results remain supportive of a critical area ratio(A_(L)/A_(S))_(crit)=(m_(i)/(2.3m_(e)))^(1/2)between the probe area A_(S)and the satellite area A_L as conventionally believed.A satellite-based Langmuir probe must satisfy this criterion to physically act as a single Langmuir probe.However,experimental investigations also found that high-energy electrons adversely affect(A_(L)/A_(S))_(crit)and a Langmuir probe's signal quality by giving additional electron current to A_(L).Based on these results,a number of limitations of the maximum probe area are derived when designing satellite-based Langmuir probes,with consideration of both the aim of the satellite and the plasma where the satellite-based probe works.These proposed measures are expected to only partially alleviate the effect of the inadequate satellite surface area on the application of satellite-based Langmuir probes.Using a larger satellite to carry a Langmuir probe remains the most viable means to obtain precise space plasma parameters.展开更多
The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experi...The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.展开更多
Uniaxial strain is a powerful tuning parameter that can control symmetry and anisotropic electronic properties in iron-based superconductors.However,accurately characterizing anisotropic strain can be challenging and ...Uniaxial strain is a powerful tuning parameter that can control symmetry and anisotropic electronic properties in iron-based superconductors.However,accurately characterizing anisotropic strain can be challenging and complex.Here,we utilize a cryogenic optical system equipped with a high-spatial-resolution microscope to characterize surface strains in iron-based superconductors using the digital image correlation method.Compared with other methods such as high-resolution x-ray diffraction,strain gauge,and capacitive sensor,digital image correlation offers a non-contact full-field measurement approach,acting as an optical virtual strain gauge that provides high spatial resolution.The results measured on detwinned BaFe_(2)As_(2)are quantitatively consistent with the distortion measured by x-ray diffraction and neutron Larmor diffraction.These findings highlight the potential of cryogenic digital image correlation as an effective and accessible tool for probing the isotropic and anisotropic strains,facilitating applications of uniaxial strain tuning in research of quantum materials.展开更多
A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparis...A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.展开更多
An integrated quantum probe for magnetic field imaging is proposed,where the nitrogen–vacancy(NV)center fixed at the fiber tip is located on the periphery of flexible ring resonator.Using flexible polyimide(PI)as the...An integrated quantum probe for magnetic field imaging is proposed,where the nitrogen–vacancy(NV)center fixed at the fiber tip is located on the periphery of flexible ring resonator.Using flexible polyimide(PI)as the substrate medium,we design a circular microstrip antenna,which can achieve a bandwidth of 140 MHz at Zeeman splitting frequency of 2.87 GHz,specifically suitable for NV center experiments.Subsequently,this antenna is seamlessly fixed at a three-dimensional-printed cylindrical support,allowing the optical fiber tip to extend out of a dedicated aperture.To mitigate errors originating from processing,precise tuning within a narrow range can be achieved by adjusting the conformal amplitude.Finally,we image the microwave magnetic field around the integrated probe with high resolution,and determine the suitable area for placing the fiber tip(SAP).展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11804195,11847224,11674198,and 12274265)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2018BA034 and ZR2022MA006)。
文摘To understand the gene-based biological processes in-depth,the single-molecule real-time sequencing has drawn increasing attention with promoted by the Human Genome Project.Herein,a set of newly designed canonical fluorescent bases(A_(y),tC,G_(b),T_(p))are proposed for four-color DNA sequencing.These quasi-intrinsic probes are derived from the fluorophore replacement and ring expansion on natural bases,which still keep the pyrimidine or purine underlying skeleton and Watson–Crick hydrogen bonding face to allow minimal perturbation to the native DNA duplex.More importantly,these nucleobase analogues possess red-shifted absorption and efficient photoluminescence due to the enhancedπ-conjugation in character.Meanwhile,the four analogues could generate distinct emission wavelength(Δλ~50 nm)for real-time sequencing.To assess the biological employment of the proposed biosensors,the effects of base pairing and linking deoxyribose are also considered.
基金supported by the National Natural Science Foundation of China(82072432)the China-Japan Friendship Hospital Horizontal Project/Spontaneous Research Funding(2022-HX-JC-7)+1 种基金the National High Level Hospital Clinical Research Funding(2022-NHLHCRF-PY-20)the Elite Medical Professionals project of China-Japan Friendship Hospital(ZRJY2021-GG12).
文摘Rheumatoid arthritis(RA)is a systemic autoimmune disease that is primarily manifested as synovitis and polyarticular opacity and typically leads to serious joint damage and irreversible disability,thus adversely affecting locomotion ability and life quality.Consequently,good prognosis heavily relies on the early diagnosis and effective therapeutic monitoring of RA.Activatable fluorescent probes play vital roles in the detection and imaging of biomarkers for disease diagnosis and in vivo imaging.Herein,we review the fluorescent probes developed for the detection and imaging of RA biomarkers,namely reactive oxygen/nitrogen species(hypochlorous acid,peroxynitrite,hydroxyl radical,nitroxyl),pH,and cysteine,and address the related challenges and prospects to inspire the design of novel fluorescent probes and the improvement of their performance in RA studies.
文摘Parameters of hydrogen plasma in a miniature Penning discharge ion source, including the electron temperature and the electron density, were measured by using double probes. The results indicate that the electron density increases and the electron temperature decreases with the increase in gas pressure and the discharge current. The electron temperature is about 5 - 9 eV and the electron density is 6.0× 10^13 ～ 1.2 × 10^14 m^-3 while the discharge current is in a range of 50 - 120 μA.
基金the National Natural Science Foundation of China under Grant No 60907004the K.C.Wong Education Foundation of Hong Kong+1 种基金the Scientific Research Funds for Excellent Doctoral Dissertation of CASthe President Fund of UCAS,and the Fusion Foundation of Research and Education,CAS。
文摘Generalized ptychography is established with diverse probes,which not only extend the core spirit of ptychography that is the overlapping of neighboring probes,but also enhance the imaging quality.We find that in one of suggested configurations with visible light,the performances of two types of diversified probes are improved in comparison with the traditional circular probes.This may open up some new possibilities of ptychographic imaging.
基金Supported by the National Key R&D Program of China(Grant Nos.2017YFF0206105,2016YFA0301002 and 2017YFA0303000)the Young Investigator Program of CAS(Grant No.2016217)+3 种基金the Frontier Science Key Programs of the CAS(Grant No.QYZDY-SSW-JSC033)the Strategic Priority Research Program of CAS(Grant No.XDA18000000)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the National Natural Science Foundation of China(Grant No.11827805).
文摘We develop superconducting quantum interference device(SQUID)probes based on 3D nano-bridge junctions for the scanning SQUID microscopy.The use of these nano-bridge junctions enables imaging in the presence of a high magnetic field.Conventionally,a superconducting ground layer has been employed for better magnetic shielding.In our study,we prepare a number of scanning SQUID probes with and without a ground layer to evaluate their performance in external magnetic fields.The devices show the improved magnetic modulation up to 1.4 T.It is found that the ground layer reduces the inductance,and increases the modulation depth and symmetricity of the gradiometer design in the absence of the field.However,the layer is not compatible with the use of the scanning SQUID probe in the field because it decreases its working field range.Moreover,by adding the layer,the mutual inductance between the feedback coil and the SQUID also decreases linearly as a function of the field.
文摘This study presents the Langmuir and Faraday probe measurements conducted to determine the plume characteristics of the BUSTLab microwave electrothermal thruster(MET).The thruster,designed to operate at 2.45 GHz frequency,is run with helium,argon and nitrogen gases as the propellant.For the measurements,the propellant volume flow rate and the delivered microwave power levels are varied.Experiments with nitrogen gas revealed certain operation regimes where a very luminous plume is observed.With the use of in-house-built Langmuir probes and a Faraday probe with guard ring,thruster plume electron temperature,plasma density and ion current density values are measured,and the results are presented.The measurements show that MET thruster plume effects on spacecraft will likely be similar to those of the arcjet plume.It is observed that the measured plume ion flux levels are very low for the high volume flow rates used for the operation of this thruster.
基金Project supported by the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2020MA078)。
文摘To improve two-photon absorption(TPA)response of a newly synthesized probe,a series of ratiometric two-photon fluorescent Zn^(2+) sensors based on quinoline and DPA moieties have been designed.The one-photon absorption,TPA,and emission properties of the experimental and designed probes before and after coordination with Zn^(2+) are investigated employing the density functional theory in combination with response functions.The design consists of two levels.In the first level of design,five probes are constructed through using several electron acceptors or donors to increase accepting or donating ability of the fluorophores.It shows that all the designed probes have stronger TPA intensities at longer wavelengths with respect to the experimental probe because of the increased intra-molecular charge transfer.Moreover,it is found that the probe 4 built by adding an acyl unit has the largest TPA cross section among the designed structures due to the form of longer conjugated length and more linear backbone.One dimethylamino terminal attached along the skeleton can improve TPA intensity more efficiently than two side amino groups.Therefore,in the second level of design,a new probe 7 is formed by both an acyl unit and a dimethylamino terminal.It exhibits that the TPA cross sections of probe 7 and its zinc complex increase dramatically.Furthermore,the fluorescence quantum yields of the designed probes4 and 7 are calculated in a new way,which makes use of the relation between the computed difference of dipole moment and the measured fluorescence quantum yield.The result shows that our design also improves the fluorescence quantum yield considerably.All in all,the designed probes 4 and 7 not only possess enhanced TPA intensities but also have large differences of emission wavelength upon Zn^(2+) coordination and strong fluorescence intensity,which demonstrates that they are potential ratiometric two-photon fluorescent probes.
基金supported by National Natural Science Foundation of China(No.11875285)the CAS Key Research Program of Frontier Sciences(No.QYZDB-SSWSLH001)the Chinese Academy of Science Hundred Youth Talent Program。
文摘Limited particle transit time is one of several limiting factors which determine the maximum temporal resolution of a Langmuir probe.In this work,we have revisited the known fast sweep Langmuir probe techniques in a uniform,quiescent multi-dipole confined hot cathode discharge with two operation scenarios:one in which the probe sweeping frequency fsweepis much lower than the ion plasma frequency fpi,another one where fsweepis much greater than fpi,respectively.This allows investigation into the effect of limited ion-motion on I–V traces.Serious distortions of I–V traces at high frequencies,previously claimed to be an ion-motion limitation effect,were not found unless shunt resistance is sufficiently high,despite a f;/f;ratio of~3.On the other hand,evidences of sheath capacitance on the I–V traces have been observed.Distortions of I–V traces qualitatively agree with predictions of sheath capacitance response to the sweeping voltage.Additionally,techniques in fast sweep Langmuir probe are briefly discussed.The comparison between the high-speed dual Langmuir probe(HDLP)and the single probe setup shows that the capacitive response can be removed via subtracting a leakage current for the single probe setup almost as effectively as using the HDLP setup,but the HDLP setup does remain advantageous in its facilitation of better recovery of weak current signal commonly in low density plasma.
基金supported by the National Basic Research Program of China(Grant No.2011CB808105)the National Natural Science Foundation of China(Grant No.21303096)
文摘Response theory is used to investigate one- and two-photon absorption（TPA） as well as the emission properties of a series of potential zinc ion and pH sensitive materials containing 2-（2＇-hydroxyphenyl）benzoxazole（HPBO） end groups.Special emphasis is placed on the evolution of their optical properties upon combining with zinc ions or deprotonation.Our calculated results indicate that upon combining with zinc ions or deprotonation,these HPBO derivatives show drastic changes in their one-photon absorption（OPA）,emission,and TPA properties.Moreover,the mechanisms of the probes are analyzed and found to be an intramolecular charge transfer.These compounds are thus proved to be excellent candidates for two-photon fluorescent zinc and pH probes.
文摘An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.
基金supported by NIFS budgets NIFS10ULRR003,NIFS11ULRR703,and NIFS11PLRR302
文摘Two pairs of high-frequency magnetic probes were installed in the Large Helical Device （LHD）. During the injection of a perpendicular neutral beam, ion cyclotron emissions （ICEs） with the fundamental frequency corresponding to the ion cyclotron frequency at the plasma edge were detected, which are the same type of ICE as measured with the former spare ion cyclotron range of frequencies （ICRF） heating antennas. This type of ICE was further investigated with regard to the phase and intensity of signals. Another type of ICE was found in the LHD, and these ICEs were synchronized with bursts of toroidicity induced Alfv^n eigenmodes （TAE） and the rise of intensity of lost ion flux. Therefore the source of these ICEs was thought to be the particles transferred from the core to the outer region of plasma by the TAE bursts. The frequency of ICEs induced by the TAE bursts increases linearly with the magnetic field strength, since the ion cyclotron frequency increases with the magnetic field strength.
基金The project supported by the National Meg-Science Engineering Project of the Chinese Government
文摘The plasma shape and other paremeters such as /3P, li is important for the tokamak deveice where the plasma has a non-circular cross-section of sufficient elongation. The measuered signals of magnetic probes and flux loops are used to reconstruct the plasma shape and the current profile in device operation and plasma shape feed back control system. So the number and positions of magnetic probes and flux loops provides the basis of the plasma reconstruction. This paper instroduce how to use EFIT code (equilibrium fitting code) to determine the number and positions of the magnetic probes and flux loops. The simulation result is given also.
基金financially supported by National Natural Science Foundation of China(22074100)the Young Elite Scientist Sponsorship Program by CAST(YESS20200036)+3 种基金the Researchers Supporting Project Number RSP-2021/138King Saud University,Riyadh,Saudi ArabiaTechnological Innovation R&D Project of Chengdu City(2019-YF05-31702266-SN)Sichuan University-Panzhihua City joint Project(2020CDPZH-5)。
文摘Mercury is a threatening pollutant in food,herein,we developed a Tb^(3+)-nucleic acid probe-based label-free assay for mix-and-read,rapid detection of mercury pollution.The assay utilized the feature of light-up fluorescence of terbium ions(Tb^(3+))via binding with single-strand DNA.Mercury ion,Hg^(2+)induced thymine(T)-rich DNA strand to form a double-strand structure(T-Hg^(2+)-T),thus leading to fluorescence reduction.Based on the principle,Hg^(2+)can be quantified based on the fluorescence of Tb^(3+),the limit of detection was 0.0689μmol/L and the linear range was 0.1-6.0μmol/L.Due to the specificity of T-Hg^(2+)-T artificial base pair,the assay could distinguish Hg^(2+)from other metal ions.The recovery rate was ranged in 98.71%-101.34%for detecting mercury pollution in three food samples.The assay is low-cost,separation-free and mix-to-read,thus was a competitive tool for detection of mercury pollution to ensure food safety.
基金supported by National Natural Science Foundation of China(No.11075033)。
文摘The double-coupled microwave resonance probe(DMRP)based on the hairpin probe is proposed for diagnosing atmospheric plasma jet(ne<1017 m-3).In this work,the resonance characteristics of DMRP are investigated by numerical simulation.It shows that two resonance peaks on the reflectance spectrum can be observed,and influenced significantly by some parameters,such as the probe separation,the distance to the handheld radio frequency atmospheric pressure glow discharge plasma jet(RF-APGDPJ)and the plasma electron density less than 1017 m-3.Based on two resonance modes of DMRP,the electron densities in the afterglow of RF-APGDPJ at the different rf powers and helium flow rates are diagnosed experimentally by matching the change of FWHM(Df1-Df1,airand Df2-Df2,air)measured by vector network analyzer with the simulated relation between the FWHM changes and the plasma density.
基金Project supported by the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2014AM026)the National Natural Science Foundation of China(Grant Nos.11374195 and 11404193)the Taishan Scholar Project of Shandong Province,China
文摘The properties of one-photon absorption（OPA）, emission and two-photon absorption（TPA） of a di-2-picolylaminebased zinc ion sensor are investigated by employing the density functional theory in combination with response functions.The responsive mechanism is explored. It is found that the calculated OPA and TPA properties are quite consistent with experimental data. Because the intra-molecular charge transfer（ICT） increases upon zinc ion binding, the TPA intensity is enhanced dramatically. According to the model sensor, we design a series of zinc ion probes which differ by conjugation center, acceptor and donor moieties. The properties of OPA, emission and TPA of the designed molecules are calculated at the same computational level. Our results demonstrate that the OPA and emission wavelengths of the designed probes have large red-shifts after zinc ions have been bound. Comparing with the model sensor, the TPA intensities of the designed probes are enhanced significantly and the absorption positions are red-shifted to longer wavelength range. Furthermore, the TPA intensity can be improved greatly upon zinc ion binding due to the increased ICT mechanism. These compounds are potential excellent candidates for two-photon fluorescent zinc ion probes.
基金supported by National Natural Science Foundation of China(Nos.12275305 and 12205334)the Chinese Academy of Science Hundred Youth Talent Program+1 种基金China Postdoctoral Science Foundation(No.2022M713188)the Director’s Fund of Hefei Institutes of Physical Science,Chinese Academy of Sciences(No.YZJJ2022QN19)。
文摘In this article,the effect of the finite conductive surface area of a satellite on the use of satellite-based Langmuir probes is reviewed in light of the basic theory of asymmetric double Langmuir probes(ADLPs).Recent theoretical and experimental studies have discussed electron sheath/presheath formation and the electron Bohm criterion along with their implications for satellite-based Langmuir probes.The effects predicted by the latest theory of the electron Bohm criterion were not experimentally observed and the experimental results remain supportive of a critical area ratio(A_(L)/A_(S))_(crit)=(m_(i)/(2.3m_(e)))^(1/2)between the probe area A_(S)and the satellite area A_L as conventionally believed.A satellite-based Langmuir probe must satisfy this criterion to physically act as a single Langmuir probe.However,experimental investigations also found that high-energy electrons adversely affect(A_(L)/A_(S))_(crit)and a Langmuir probe's signal quality by giving additional electron current to A_(L).Based on these results,a number of limitations of the maximum probe area are derived when designing satellite-based Langmuir probes,with consideration of both the aim of the satellite and the plasma where the satellite-based probe works.These proposed measures are expected to only partially alleviate the effect of the inadequate satellite surface area on the application of satellite-based Langmuir probes.Using a larger satellite to carry a Langmuir probe remains the most viable means to obtain precise space plasma parameters.
基金supported by National Natural Science Foundation of China(Nos.92066108 and 51277061)。
文摘The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA1400400)the Fundamental Research Funds for the Central Universities,and the National Natural Science Foundation of China(Grant Nos.12174029 and 11922402).
文摘Uniaxial strain is a powerful tuning parameter that can control symmetry and anisotropic electronic properties in iron-based superconductors.However,accurately characterizing anisotropic strain can be challenging and complex.Here,we utilize a cryogenic optical system equipped with a high-spatial-resolution microscope to characterize surface strains in iron-based superconductors using the digital image correlation method.Compared with other methods such as high-resolution x-ray diffraction,strain gauge,and capacitive sensor,digital image correlation offers a non-contact full-field measurement approach,acting as an optical virtual strain gauge that provides high spatial resolution.The results measured on detwinned BaFe_(2)As_(2)are quantitatively consistent with the distortion measured by x-ray diffraction and neutron Larmor diffraction.These findings highlight the potential of cryogenic digital image correlation as an effective and accessible tool for probing the isotropic and anisotropic strains,facilitating applications of uniaxial strain tuning in research of quantum materials.
基金Project supported by the National Natural Science Foundation of China (Grant No.11905076)S&T Program of Hebei (Grant No.SZX2020034)。
文摘A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB2012600)the Science and Technology Plan Project of State Administration of Market Regulation,China(Grant No.2021MK039)。
文摘An integrated quantum probe for magnetic field imaging is proposed,where the nitrogen–vacancy(NV)center fixed at the fiber tip is located on the periphery of flexible ring resonator.Using flexible polyimide(PI)as the substrate medium,we design a circular microstrip antenna,which can achieve a bandwidth of 140 MHz at Zeeman splitting frequency of 2.87 GHz,specifically suitable for NV center experiments.Subsequently,this antenna is seamlessly fixed at a three-dimensional-printed cylindrical support,allowing the optical fiber tip to extend out of a dedicated aperture.To mitigate errors originating from processing,precise tuning within a narrow range can be achieved by adjusting the conformal amplitude.Finally,we image the microwave magnetic field around the integrated probe with high resolution,and determine the suitable area for placing the fiber tip(SAP).
