For unveiling the pathological evolution of breast cancer, nonlinear multiphoton microscopic(MPM) and confocal Raman microspectral imaging(CRMI) techniques were both utilized to address the structural and constitution...For unveiling the pathological evolution of breast cancer, nonlinear multiphoton microscopic(MPM) and confocal Raman microspectral imaging(CRMI) techniques were both utilized to address the structural and constitutional characteristics of healthy(H), ductal carcinoma in situ(DCIS), and invasive ductal carcinoma(IDC) tissues. MPM-based techniques,including two-photon excited fluorescence(TPEF) and second harmonic generation(SHG), visualized label-free and the fine structure of breast tissue. Meanwhile, CRMI not only presented the chemical images of investigated samples with the K-mean cluster analysis method(KCA), but also pictured the distribution of components in the scanned area through univariate imaging. MPM images illustrated that the cancer cells first arranged around the basement membrane of the duct,then proliferated to fill the lumens of the duct, and finally broke through the basement membrane to infiltrate into the stroma.Although the Raman imaging failed to visualize the cell structure with high resolution, it explained spectroscopically the gradual increase of nucleic acid and protein components inside the ducts as cancer cells proliferated, and displayed the distribution pattern of each biological component during the evolution of breast cancer. Thus, the combination of MPM and CRMI provided new insights into the on-site pathological diagnosis of malignant breast cancer, also ensured technical support for the development of multimodal optical imaging techniques for precise histopathological analysis.展开更多
Deep learning is capable of greatly promoting the progress of super-resolution imaging technology in terms of imaging and reconstruction speed,imaging resolution,and imagingflux.This paper proposes a deep neural netwo...Deep learning is capable of greatly promoting the progress of super-resolution imaging technology in terms of imaging and reconstruction speed,imaging resolution,and imagingflux.This paper proposes a deep neural network based on a generative adversarial network(GAN).The generator employs a U-Net-based network,which integrates Dense Net for the downsampling component.The proposed method has excellent properties,for example,the network model is trained with several different datasets of biological structures;the trained model can improve the imaging resolution of different microscopy imaging modalities such as confocal imaging and wide-field imaging;and the model demonstrates a generalized ability to improve the resolution of different biological structures even out of the datasets.In addition,experimental results showed that the method improved the resolution of caveolin-coated pits(CCPs)structures from 264 nm to 138 nm,a 1.91-fold increase,and nearly doubled the resolution of DNA molecules imaged while being transported through microfluidic channels.展开更多
We demonstrate a multi-branch all polarization-maintaining Er:fiber frequency comb with five application ports for precise measurement of atomic/molecular transition frequencies in the near-infrared region.A fully sta...We demonstrate a multi-branch all polarization-maintaining Er:fiber frequency comb with five application ports for precise measurement of atomic/molecular transition frequencies in the near-infrared region.A fully stabilized Er:fiber frequency comb with a nonlinear amplifying loop mirror is achieved.The in-loop relative instability of stabilized carrier-envelope-offset frequency is 5.6×10-18 at 1 s integration time,while that of the repetition rate is well below 1.8×10-12 limited by the measurement noise floor of the commercial frequency counter.Five application ports are individually optimized for applications with different wavelengths(1064 nm,1083 nm,1380 nm,1637 nm and 1750 nm).The beat note between the optical frequency comb and continuous laser exhibits the signal-to-noise ratio of at least 30 dB at a resolution bandwidth of 100 kHz.The in-loop frequency instability of the comb is evaluated to be good enough for measurement of rotation-resolved transitions of molecules below 1 kHz resolution.展开更多
By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm i...By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.展开更多
An efficient narrow=linewidth single-frequency （SF） Yb-doped all-fiber master oscillator power amplifier （MOPA） laser operating at 1064.3 nm is demonstrated experimentally. A ring cavity SF fiber laser is used as ...An efficient narrow=linewidth single-frequency （SF） Yb-doped all-fiber master oscillator power amplifier （MOPA） laser operating at 1064.3 nm is demonstrated experimentally. A ring cavity SF fiber laser is used as the seed source for the MOPA system and the Yb-doped fibers are employed as the gain medium or the saturable absorber. The SF operation is observed to be stable without mode hopping. The highest output power of 266 mW is obtained under the 400row pump power with the corresponding slope efficiency of 66.2-. The Hnewidth of the amplified output laser is approximately I kHz and its optical signal-to-noise ratio is over 45 dB.展开更多
In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the move...In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.展开更多
The effects of La and Sb doping on the electronic structure and optical properties of SrTiO3 are investigated by first-principles calculation of the plane wave ultra-soft pseudo-potential based on density functional t...The effects of La and Sb doping on the electronic structure and optical properties of SrTiO3 are investigated by first-principles calculation of the plane wave ultra-soft pseudo-potential based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of SrTiO3, and its structural stability can be improved by La doping. The La^3＋ ion fnlly acts as an electron donor in Sr0.875La0.125TiO3 and the Fermi level shifts into the conduction bands （CBs） after La doping. As for SrSb0.125Ti0.87503, there is a distortion near the bottom of the CBs for SrSb0.125Ti0.87503 after Sb doping and an incipient localization of some of the doped electrons trapped in the Ti site, making it impossible to describe the evolution of the density of states （DOS） within the rigid band model. At the same time, the DOSs of the two electron-doped systems shift towards low energies and the optical band gaps are broadened by about 0.4 and 0.6 eV for Sr0.875La0.125TiO3 and SrSb0.125Ti0.87503, respectively. Moreover, the transmittance of SrSb0.125Ti0.87503 is as high as 95% in most of the visible region, which is higher than that of Sr0.875La0.125TiO3（85%）. The wide band gap, the small transition probability and the weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the significant optical transparency of SrSb0.125Ti0.875O3.展开更多
Electrokinetic(EK)micromixers have been widely studied in the past decade for biochemical applications,biological and chemical analysis,etc.Unfortunately,almost all EK mixers require different electrical conductivity ...Electrokinetic(EK)micromixers have been widely studied in the past decade for biochemical applications,biological and chemical analysis,etc.Unfortunately,almost all EK mixers require different electrical conductivity between the two fluids to be mixed,which has greatly limited their wide applications,in cases where the two streams to be mixed have equivalent electrical conductivity.Here we show that mixing enhancement between two fluids with identical conductivity can be achieved in an EK micromixer with conductive sidewalls,where the electric field is in transverse direction of the flow.The results revealed that the mixing became stronger with increased conductivity value.This mixing method provides a novel and convenient strategy for mixing two liquids with the same or similar electrical conductivity in microfluidic systems,and could potentially serves as a powerful tool for sample preparation in applications such as liquid biopsy,and environmental monitoring,etc.展开更多
Efficient cell migration is crucial for the functioning of biological processes, e.g., morphogenesis, wound healing, and cancer metastasis. In this study, we monitor the migratory behavior of the 3D fibroblast cluster...Efficient cell migration is crucial for the functioning of biological processes, e.g., morphogenesis, wound healing, and cancer metastasis. In this study, we monitor the migratory behavior of the 3D fibroblast clusters using live cell microscopy,and find that crowded environment affects cell migration, i.e., crowding leads to directional migration at the cluster’s periphery. The number of cell layers being stacked during seeding determines the directional-to-random transition. Intriguingly,the migratory behavior of cell clusters resembles the dispersion dynamics of clouds of passive particles, indicating that the biological process is driven by physical effects(e.g., entropy) rather than cell communication. Our findings highlight the role of intrinsic physical characteristics, such as crowding, in regulating biological behavior, and suggest new therapeutic approaches targeting at cancer metastasis.展开更多
Interactions between deoxyribonucleic acid(DNA) and metal ions are vital for maintaining life functions, however,there are still unsolved questions about its mechanisms. It is of great practical significance to study ...Interactions between deoxyribonucleic acid(DNA) and metal ions are vital for maintaining life functions, however,there are still unsolved questions about its mechanisms. It is of great practical significance to study these issues for medical chip design, drug development, health care, etc. In this investigation, the conductivity properties of λ-DNA solutions with mono-/divalent metal ions(Na+, K^(+), Mg^(2+), and Ca^(2+)) are experimentally studied as they are electrically driven through a 5 μm microfluidic channel. Experimental data indicate that the conductivities of λ-DNA solutions with metal ions(M+/M2+) basically tend to reduce firstly and then increase as the voltage increases, of which the turning points varied with the metal ions. When the voltage surpasses turning points, the conductivity of λ-DNA-M+solutions increases with the concentration of metal ions, while that of λ-DNA-M^(2+)solutions decrease. Moreover, the conductivity of λ-DNA-M^(2+)solutions is always smaller than that of λ-DNA-M+solutions, and with high-concentration M^(2+), it is even smaller than that of the λ-DNA solution. The main reasons for the above findings could be attributed to the polarization of electrodes and different mechanisms of interactions between metal ions and λ-DNA molecules. This investigation is helpful for the precise manipulation of single DNA molecules in micro-/nanofluidic space and the design of new biomedical micro-/nanofluidic sensors.展开更多
As one of the most important realizations of stimulated emission depletion(STED)microscopy,the continuous-wave(CW)STED system,constructed by using CW lasers as the excitation and STED beams,has been investigated and d...As one of the most important realizations of stimulated emission depletion(STED)microscopy,the continuous-wave(CW)STED system,constructed by using CW lasers as the excitation and STED beams,has been investigated and developed for nearly a decade.However,a theoretical model of the suppression factors in CW STED has not been well established.In this investigation,the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied.The full-width-at-half-maximum(FWHM)of a CW STED with a doughnut-shaped STED beam is also reanalyzed.It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities.In addition,the FWHM is highly sensitive to both the fluorescence rate(inverse of fluoresce lifetime)and the quenching rate,but insensitive to the rate of vibrational relaxation.For comparison,the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity.Our model is highly consistent with published experimental data for evaluating the spatial resolution.This investigation is important in guiding the development of new CW STED systems.展开更多
As one type of spatially offset Raman spectroscopy(SORS), inverse SORS is particularly suited to in vivo biomedical measurements due to its ring-shaped illumination scheme. To explain inhomogeneous Raman scattering du...As one type of spatially offset Raman spectroscopy(SORS), inverse SORS is particularly suited to in vivo biomedical measurements due to its ring-shaped illumination scheme. To explain inhomogeneous Raman scattering during in vivo inverse SORS measurements, the light–tissue interactions when excitation and regenerated Raman photons propagate in skin tissue were studied using Monte Carlo simulation. An eight-layered skin model was first built based on the latest transmission parameters. Then, an open-source platform, Monte Carlo e Xtreme(MCX), was adapted to study the distribution of 785 nm excitation photons inside the model with an inverse spatially shifted annular beam. The excitation photons were converted to emission photons by an inverse distribution method based on excitation flux with spatial offsets Δs of 1 mm, 2 mm, 3 mm and 5 mm. The intrinsic Raman spectra from separated skin layers were measured by continuous linear scanning to improve the simulation accuracy. The obtained results explain why the spectral detection depth gradually increases with increasing spatial offset, and address how the intrinsic Raman spectrum from deep skin layers is distorted by the reabsorption and scattering of the superficial tissue constituents. Meanwhile, it is demonstrated that the spectral contribution from subcutaneous fat will be improved when the offset increases to 5 mm, and the highest detection efficiency for dermal layer spectral detection could be achieved when Δs = 2 mm. Reasonably good matching between the calculated spectrum and the measured in vivo inverse SORS was achieved, thus demonstrating great utility of our modeling method and an approach to help understand the clinical measurements.展开更多
Interpreting the biochemical specifcity of spinal cord tissue is the essential requirement for underst.anding the biochemical mechanisms during spinal-cord-related pathological course.In this work,a longitudinal study...Interpreting the biochemical specifcity of spinal cord tissue is the essential requirement for underst.anding the biochemical mechanisms during spinal-cord-related pathological course.In this work,a longitudinal study was implemented to reveal a precise linkage betwoen the spectral features and the molecular composition in er vivo mouse spinal cord tissue by microspectral Raman imaging.It was testified that lipid-rich white matter could be distinguished from gray matter not only by the lipid Raman peaks at 1064,1300,1445 and 1660 cm^(-1),but also by protein(1250 and 1328 cm^(-1))and saccharides(913 and 1137 cm^(-1))distributions.K-means cluster analysis was further applied to visualize the morphological basis of spinal cord tissue by chemical components and their dist ribution patterns.T wo-dimensional chemical images were then generated to visualize the contrast between two different tissue types by integrating the intensitics of the featured Raman bands.All the obtained results ilustrated the biochemical characteristics of spinal cord tssue,as well as some specific substance variances bet ween different tssue types,which formed a solid basis for the molecular investigation of spinal cord pathologi cal alterations.展开更多
We show the possibility to generate Kuznetsov-Ma solitons based on bound-to-bound intersubband transitions in an asymmetric two-coupled well structure. By presenting the modulation instability of the nonlinear system ...We show the possibility to generate Kuznetsov-Ma solitons based on bound-to-bound intersubband transitions in an asymmetric two-coupled well structure. By presenting the modulation instability of the nonlinear system provided by the interaction between light fields and quantum wells, we show that the plane wave with small perturbation can evolve into periodic trains of pulses at high while controllable repetition rates. It is found that the formation of Kuznetsov-Ma solitons as well as their period is determined by the combination of group velocity dispersion, Kerr nonlinearity and the initial amplitude of the background wave. The present research may be useful for generating subpicosecond and femtosecond pulses.展开更多
The adsorption and reaction of CO on SrTiO3 （100） surface with and without surface oxygen vacancy are investigated by the first-principles calculation based on the density functional theory. The calculated results r...The adsorption and reaction of CO on SrTiO3 （100） surface with and without surface oxygen vacancy are investigated by the first-principles calculation based on the density functional theory. The calculated results reveal that the oxygen vacancy site prefers to the activation of the C-O bond. The adsorption energies increase to 1.0855 and 0.3245eV for defect-CO and defect-OC orientations, respectively. Particularly the C-O bond is elongated by about 0.1285 ？ in the defect-OC orientation compared with that in the Ti-OC one without surface oxygen vacancies. There is predominantly a chemisorption mechanism between the CO molecule and the surface in the defect-CO orientation.展开更多
We introduce polar substituents such as F, C1, Br into pentacene to enhance the dissolubility in common organic solvents while retaining the high charge-carrier mobilities of pentacene. Geometric structures, dipole mo...We introduce polar substituents such as F, C1, Br into pentacene to enhance the dissolubility in common organic solvents while retaining the high charge-carrier mobilities of pentacene. Geometric structures, dipole moments, frontier molecule orbits, ionization potentials and electron affinities, as well as reorganization energies of those molecules, and of pentacene for comparison, are successively calculated by density functional theory. The results indicate that haiopentacenes have rather small reorganization energies （〈 0.2 eV）, and when the substituents are in position 2 or positions 2 and 9, they are polarity molecules. Thus we conjecture that they can easily be dissolved in common organic solvents, and are promising candidates for organic semiconductors.展开更多
Gravity-induced drainage is one of the main destabilizing mechanisms for soap bubbles and foams.Here we show that solely through acoustic levitation without introducing any chemical stabilizers,liquid drainage in the ...Gravity-induced drainage is one of the main destabilizing mechanisms for soap bubbles and foams.Here we show that solely through acoustic levitation without introducing any chemical stabilizers,liquid drainage in the bubble film can be completely inhibited,therefore leading to a significant enhancement of bubble lifetime by more than two orders of magnitude and enabling the bubble to survive puncturing by a needle.Based on sound simulation and force analysis,it has been found that acoustic radiation force,exerted on both the inner and outer surfaces of the levitated bubble,acts in opposite directions,thus providing a squeezing effect to the bubble film.The hydrostatic pressure that induces drainage has been balanced by the acoustic radiation pressure exerted on both sides of the film,which is at the origin of the sound stabilization mechanism.This study provides new insights into the interplay between sound and soap bubbles or films,thus stimulating a wide range of fundamental research concerning bubble films and expanding their applications in bio/chemical reactors.展开更多
Layered molybdenum disulfide （MoS2） has received much attention as one of the most promising energy-storage and conversion materials for Li/Na ion batteries. Here, a simple and effective approach is proposed for the...Layered molybdenum disulfide （MoS2） has received much attention as one of the most promising energy-storage and conversion materials for Li/Na ion batteries. Here, a simple and effective approach is proposed for the rational design and preparation of hierarchical three-d imensional （3D） amorphous N-doped carbon nanotube@MoS2 nanosheets （3D-ANCNT@MoS2） via a simple hydrothermal method, followed by an annealing process. With such a unique nanoarchitecture, ultrathin MoS2 nanosheets grown on the external surfaces of polypyrrole-derived ANCNTs are assembled to form a hierarchical 3D nanoarchitecture, where the adopted ANCNTs serve not only as the template and continuous conductive matrix, but can also prevent MoS2 from aggregating and restacking, and help to buffer the volumetric expansion of MoS2 during cycling. More importantly, when evaluated as an anode material for lithium-ion batteries, the 3D-ANCNT@MoS2 composite exhibits excellent cycling stability, superior rate performance, and reversible specific capacity as high as 893.4 mAh·g^-1 at 0.2 A·g^-1 after 200 cycles in a half battery, and 669.4 mAh·g^-1 at 0.2 A·g^-1 after 100 cycles in the 3D-ANCNT@Mo2//LiCoO2 full battery. With respect to sodium-ion batteries, the outstanding reversible capacity, excellent rate behavior, and good cycling performance of 3D-ANCNT@MoS2 composites are also achieved.展开更多
Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bul...Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bulk nonlinear crystals with millimetre thickness,with the bandwidth limited by the phase-matching condition.Here we demonstrate broadband THz emission via surface optical rectification from a simple,commercially available 19nmthick indium tin oxide(ITO)thin film.We show an enhancement of the generated THz signal when the pump laser is tuned around the epsilon-near-zero(ENZ)region of ITO due to the pump laser field enhancement associated with the ENZ effect.The bandwidth of the THz signal generated from the ITO film can be over 3 THz,unrestricted by the phasematching condition.This work offers a new possibility for broadband THz generation in a subwavelength thin film made of an ENZ material,with emerging physics not found in existing nonlinear crystals.展开更多
To improve the atomic utilization of metals and reduce the cost of industrialization,the one-step total monoatomization of macroscopic bulk metals,as opposed to nanoscale metals,is effective.In this study,we used a th...To improve the atomic utilization of metals and reduce the cost of industrialization,the one-step total monoatomization of macroscopic bulk metals,as opposed to nanoscale metals,is effective.In this study,we used a thermal diffusion method to directly convert commercial centimeter-scale Ni foam to porous Ni single-atom-loaded carbon nanotubes(CNTs).As expected,owing to the coating of single-atom on porous,highly conductive CNT carriers,Ni single-atom electrocatalysts(Ni-SACs)exhibit extremely high activity and selectivity in CO_(2)electroreduction(CO_(2)RR),yielding a current density of>350 mA/cm^(2),a selectivity for CO of>91%under a flow cell configuration using a 1 M potassium chloride(KCl)electrolyte.Based on the superior activity of the Ni-SACs electrocatalyst,an integrated gas-phase electrochemical zero-gap reactor was introduced to generate a significant amount of CO current for potential practical applications.The overall current can be increased to 800 mA,while maintaining CO Faradaic efficiencies(FEs)at above 90%per unit cell.Our findings and insights on the active site transformation mechanism for macroscopic bulk Ni foam conversion into single atoms can inform the design of highly active single-atom catalysts used in industrial CO_(2)RR systems.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 61911530695)the Key Research and Development Project of Shaanxi Province of China (Grant No. 2023-YBSF-671)。
文摘For unveiling the pathological evolution of breast cancer, nonlinear multiphoton microscopic(MPM) and confocal Raman microspectral imaging(CRMI) techniques were both utilized to address the structural and constitutional characteristics of healthy(H), ductal carcinoma in situ(DCIS), and invasive ductal carcinoma(IDC) tissues. MPM-based techniques,including two-photon excited fluorescence(TPEF) and second harmonic generation(SHG), visualized label-free and the fine structure of breast tissue. Meanwhile, CRMI not only presented the chemical images of investigated samples with the K-mean cluster analysis method(KCA), but also pictured the distribution of components in the scanned area through univariate imaging. MPM images illustrated that the cancer cells first arranged around the basement membrane of the duct,then proliferated to fill the lumens of the duct, and finally broke through the basement membrane to infiltrate into the stroma.Although the Raman imaging failed to visualize the cell structure with high resolution, it explained spectroscopically the gradual increase of nucleic acid and protein components inside the ducts as cancer cells proliferated, and displayed the distribution pattern of each biological component during the evolution of breast cancer. Thus, the combination of MPM and CRMI provided new insights into the on-site pathological diagnosis of malignant breast cancer, also ensured technical support for the development of multimodal optical imaging techniques for precise histopathological analysis.
基金Subjects funded by the National Natural Science Foundation of China(Nos.62275216 and 61775181)the Natural Science Basic Research Programme of Shaanxi Province-Major Basic Research Special Project(Nos.S2018-ZC-TD-0061 and TZ0393)the Special Project for the Development of National Key Scientific Instruments and Equipment No.(51927804).
文摘Deep learning is capable of greatly promoting the progress of super-resolution imaging technology in terms of imaging and reconstruction speed,imaging resolution,and imagingflux.This paper proposes a deep neural network based on a generative adversarial network(GAN).The generator employs a U-Net-based network,which integrates Dense Net for the downsampling component.The proposed method has excellent properties,for example,the network model is trained with several different datasets of biological structures;the trained model can improve the imaging resolution of different microscopy imaging modalities such as confocal imaging and wide-field imaging;and the model demonstrates a generalized ability to improve the resolution of different biological structures even out of the datasets.In addition,experimental results showed that the method improved the resolution of caveolin-coated pits(CCPs)structures from 264 nm to 138 nm,a 1.91-fold increase,and nearly doubled the resolution of DNA molecules imaged while being transported through microfluidic channels.
基金Supported by the National Natural Science Foundation of China(Grant Nos.61825505 and 91536217)。
文摘We demonstrate a multi-branch all polarization-maintaining Er:fiber frequency comb with five application ports for precise measurement of atomic/molecular transition frequencies in the near-infrared region.A fully stabilized Er:fiber frequency comb with a nonlinear amplifying loop mirror is achieved.The in-loop relative instability of stabilized carrier-envelope-offset frequency is 5.6×10-18 at 1 s integration time,while that of the repetition rate is well below 1.8×10-12 limited by the measurement noise floor of the commercial frequency counter.Five application ports are individually optimized for applications with different wavelengths(1064 nm,1083 nm,1380 nm,1637 nm and 1750 nm).The beat note between the optical frequency comb and continuous laser exhibits the signal-to-noise ratio of at least 30 dB at a resolution bandwidth of 100 kHz.The in-loop frequency instability of the comb is evaluated to be good enough for measurement of rotation-resolved transitions of molecules below 1 kHz resolution.
基金Supported by the International Cooperation Projects of Ministry of Science and Technology under Grant No 2012DFB10120the National Natural Science Foundation of China under Grant No 61177059
文摘By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61475125 and 61505162the Foundation of the Education Committee of Shaanxi Province under Grant Nos 16JK1769 and l4JK1756the Science Foundation of Northwest University under Grant Nos 15NW07 and 13NW14
文摘An efficient narrow=linewidth single-frequency （SF） Yb-doped all-fiber master oscillator power amplifier （MOPA） laser operating at 1064.3 nm is demonstrated experimentally. A ring cavity SF fiber laser is used as the seed source for the MOPA system and the Yb-doped fibers are employed as the gain medium or the saturable absorber. The SF operation is observed to be stable without mode hopping. The highest output power of 266 mW is obtained under the 400row pump power with the corresponding slope efficiency of 66.2-. The Hnewidth of the amplified output laser is approximately I kHz and its optical signal-to-noise ratio is over 45 dB.
基金supported by the National Natural Science Foundation of China(Grant Nos.61378083 and 11672229)the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+2 种基金the Major Research Plan of the National Natural Science Foundation of China(Grant No.91123030)the Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110,14JS106,14JS107,and 2013SZS03-Z01)the Natural Science Basic Research Program of Shaanxi Province-Major Basic Research Project(Grant No.2016ZDJC-15)
文摘In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.
基金Project supported by the Northwest University (NWU) Graduate Innovation and Creativity Funds (Grant No. 08YZZ47)the Natural Science Foundation of Shaanxi Province of China (Grant No. 2009JM8013)
文摘The effects of La and Sb doping on the electronic structure and optical properties of SrTiO3 are investigated by first-principles calculation of the plane wave ultra-soft pseudo-potential based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of SrTiO3, and its structural stability can be improved by La doping. The La^3＋ ion fnlly acts as an electron donor in Sr0.875La0.125TiO3 and the Fermi level shifts into the conduction bands （CBs） after La doping. As for SrSb0.125Ti0.87503, there is a distortion near the bottom of the CBs for SrSb0.125Ti0.87503 after Sb doping and an incipient localization of some of the doped electrons trapped in the Ti site, making it impossible to describe the evolution of the density of states （DOS） within the rigid band model. At the same time, the DOSs of the two electron-doped systems shift towards low energies and the optical band gaps are broadened by about 0.4 and 0.6 eV for Sr0.875La0.125TiO3 and SrSb0.125Ti0.87503, respectively. Moreover, the transmittance of SrSb0.125Ti0.87503 is as high as 95% in most of the visible region, which is higher than that of Sr0.875La0.125TiO3（85%）. The wide band gap, the small transition probability and the weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the significant optical transparency of SrSb0.125Ti0.875O3.
基金partially supported by the North American Mixing Forum (NAMF), NSF CAREER (CBET-0954977)the National Natural Science Foundation of China(21705055)+1 种基金Science and Technology Development Planning Program of Jilin Province(20190201178JC)Jilin Province Industrial Technology Research and Development Project(2019C048-5)
文摘Electrokinetic(EK)micromixers have been widely studied in the past decade for biochemical applications,biological and chemical analysis,etc.Unfortunately,almost all EK mixers require different electrical conductivity between the two fluids to be mixed,which has greatly limited their wide applications,in cases where the two streams to be mixed have equivalent electrical conductivity.Here we show that mixing enhancement between two fluids with identical conductivity can be achieved in an EK micromixer with conductive sidewalls,where the electric field is in transverse direction of the flow.The results revealed that the mixing became stronger with increased conductivity value.This mixing method provides a novel and convenient strategy for mixing two liquids with the same or similar electrical conductivity in microfluidic systems,and could potentially serves as a powerful tool for sample preparation in applications such as liquid biopsy,and environmental monitoring,etc.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51927804 and 12174306)the Natural Science Basic Research Program of Shaanxi Province of China (Grant No. 2023-JC-JQ-02)。
文摘Efficient cell migration is crucial for the functioning of biological processes, e.g., morphogenesis, wound healing, and cancer metastasis. In this study, we monitor the migratory behavior of the 3D fibroblast clusters using live cell microscopy,and find that crowded environment affects cell migration, i.e., crowding leads to directional migration at the cluster’s periphery. The number of cell layers being stacked during seeding determines the directional-to-random transition. Intriguingly,the migratory behavior of cell clusters resembles the dispersion dynamics of clouds of passive particles, indicating that the biological process is driven by physical effects(e.g., entropy) rather than cell communication. Our findings highlight the role of intrinsic physical characteristics, such as crowding, in regulating biological behavior, and suggest new therapeutic approaches targeting at cancer metastasis.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62275216 and 61775181)the Innovation Capability Support Program of Shaanxi Province of China (Grant Nos. S2018-ZC-TD-0061 and TZ0393)the National Key Scientific Instrument and Equipment Development Projects of China (Grant No. 51927804)。
文摘Interactions between deoxyribonucleic acid(DNA) and metal ions are vital for maintaining life functions, however,there are still unsolved questions about its mechanisms. It is of great practical significance to study these issues for medical chip design, drug development, health care, etc. In this investigation, the conductivity properties of λ-DNA solutions with mono-/divalent metal ions(Na+, K^(+), Mg^(2+), and Ca^(2+)) are experimentally studied as they are electrically driven through a 5 μm microfluidic channel. Experimental data indicate that the conductivities of λ-DNA solutions with metal ions(M+/M2+) basically tend to reduce firstly and then increase as the voltage increases, of which the turning points varied with the metal ions. When the voltage surpasses turning points, the conductivity of λ-DNA-M+solutions increases with the concentration of metal ions, while that of λ-DNA-M^(2+)solutions decrease. Moreover, the conductivity of λ-DNA-M^(2+)solutions is always smaller than that of λ-DNA-M+solutions, and with high-concentration M^(2+), it is even smaller than that of the λ-DNA solution. The main reasons for the above findings could be attributed to the polarization of electrodes and different mechanisms of interactions between metal ions and λ-DNA molecules. This investigation is helpful for the precise manipulation of single DNA molecules in micro-/nanofluidic space and the design of new biomedical micro-/nanofluidic sensors.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11672229 and 61378083)International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+4 种基金Major Research Plan of the National Natural Science Foundation of China(Grant No.91123030)Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110and 2013SZS03-Z01)Natural Science Basic Research Program of Shaanxi Province-Major Basic Research Project,China(Grant No.2016ZDJC-15)Young Scientist Fund of the National Natural Science Foundation of China(Grant No.11504294)the Youth Talent Plan of the Natural Science Foundation of Shaanxi Province of China(Grant No.2016JQ103)
文摘As one of the most important realizations of stimulated emission depletion(STED)microscopy,the continuous-wave(CW)STED system,constructed by using CW lasers as the excitation and STED beams,has been investigated and developed for nearly a decade.However,a theoretical model of the suppression factors in CW STED has not been well established.In this investigation,the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied.The full-width-at-half-maximum(FWHM)of a CW STED with a doughnut-shaped STED beam is also reanalyzed.It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities.In addition,the FWHM is highly sensitive to both the fluorescence rate(inverse of fluoresce lifetime)and the quenching rate,but insensitive to the rate of vibrational relaxation.For comparison,the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity.Our model is highly consistent with published experimental data for evaluating the spatial resolution.This investigation is important in guiding the development of new CW STED systems.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61911530695)the Key Research and Development Project of Shaanxi Province, China (Grant No. 2023-YBSF-671)。
文摘As one type of spatially offset Raman spectroscopy(SORS), inverse SORS is particularly suited to in vivo biomedical measurements due to its ring-shaped illumination scheme. To explain inhomogeneous Raman scattering during in vivo inverse SORS measurements, the light–tissue interactions when excitation and regenerated Raman photons propagate in skin tissue were studied using Monte Carlo simulation. An eight-layered skin model was first built based on the latest transmission parameters. Then, an open-source platform, Monte Carlo e Xtreme(MCX), was adapted to study the distribution of 785 nm excitation photons inside the model with an inverse spatially shifted annular beam. The excitation photons were converted to emission photons by an inverse distribution method based on excitation flux with spatial offsets Δs of 1 mm, 2 mm, 3 mm and 5 mm. The intrinsic Raman spectra from separated skin layers were measured by continuous linear scanning to improve the simulation accuracy. The obtained results explain why the spectral detection depth gradually increases with increasing spatial offset, and address how the intrinsic Raman spectrum from deep skin layers is distorted by the reabsorption and scattering of the superficial tissue constituents. Meanwhile, it is demonstrated that the spectral contribution from subcutaneous fat will be improved when the offset increases to 5 mm, and the highest detection efficiency for dermal layer spectral detection could be achieved when Δs = 2 mm. Reasonably good matching between the calculated spectrum and the measured in vivo inverse SORS was achieved, thus demonstrating great utility of our modeling method and an approach to help understand the clinical measurements.
基金supported by Natural Science Foundation of China (No.11404258)Scientific Research Project of Education Department of Shaanxi,China (No.14JK1743)+2 种基金Key Scientific Research Project of Education Department of Shaanxi,China (No.15JS102)Major Fundamental Research Program of Shaanxi Province,China (No.2016ZDJC-15)supported by the outstanding youth scholar project of Northwest University,Shaanxi,China.
文摘Interpreting the biochemical specifcity of spinal cord tissue is the essential requirement for underst.anding the biochemical mechanisms during spinal-cord-related pathological course.In this work,a longitudinal study was implemented to reveal a precise linkage betwoen the spectral features and the molecular composition in er vivo mouse spinal cord tissue by microspectral Raman imaging.It was testified that lipid-rich white matter could be distinguished from gray matter not only by the lipid Raman peaks at 1064,1300,1445 and 1660 cm^(-1),but also by protein(1250 and 1328 cm^(-1))and saccharides(913 and 1137 cm^(-1))distributions.K-means cluster analysis was further applied to visualize the morphological basis of spinal cord tissue by chemical components and their dist ribution patterns.T wo-dimensional chemical images were then generated to visualize the contrast between two different tissue types by integrating the intensitics of the featured Raman bands.All the obtained results ilustrated the biochemical characteristics of spinal cord tssue,as well as some specific substance variances bet ween different tssue types,which formed a solid basis for the molecular investigation of spinal cord pathologi cal alterations.
基金Supported by the National Basic Research Program of China under Grant No 2010CB434811the National Natural Science Foundation of China under Grant Nos 11047025 and 201180016
文摘We show the possibility to generate Kuznetsov-Ma solitons based on bound-to-bound intersubband transitions in an asymmetric two-coupled well structure. By presenting the modulation instability of the nonlinear system provided by the interaction between light fields and quantum wells, we show that the plane wave with small perturbation can evolve into periodic trains of pulses at high while controllable repetition rates. It is found that the formation of Kuznetsov-Ma solitons as well as their period is determined by the combination of group velocity dispersion, Kerr nonlinearity and the initial amplitude of the background wave. The present research may be useful for generating subpicosecond and femtosecond pulses.
文摘The adsorption and reaction of CO on SrTiO3 （100） surface with and without surface oxygen vacancy are investigated by the first-principles calculation based on the density functional theory. The calculated results reveal that the oxygen vacancy site prefers to the activation of the C-O bond. The adsorption energies increase to 1.0855 and 0.3245eV for defect-CO and defect-OC orientations, respectively. Particularly the C-O bond is elongated by about 0.1285 ？ in the defect-OC orientation compared with that in the Ti-OC one without surface oxygen vacancies. There is predominantly a chemisorption mechanism between the CO molecule and the surface in the defect-CO orientation.
文摘We introduce polar substituents such as F, C1, Br into pentacene to enhance the dissolubility in common organic solvents while retaining the high charge-carrier mobilities of pentacene. Geometric structures, dipole moments, frontier molecule orbits, ionization potentials and electron affinities, as well as reorganization energies of those molecules, and of pentacene for comparison, are successively calculated by density functional theory. The results indicate that haiopentacenes have rather small reorganization energies （〈 0.2 eV）, and when the substituents are in position 2 or positions 2 and 9, they are polarity molecules. Thus we conjecture that they can easily be dissolved in common organic solvents, and are promising candidates for organic semiconductors.
基金the National Natural Science Foundation of China(Grant Nos.12272314,11972303)the Opening Fund of the State Key Laboratory of Nonlinear Mechanics for supporting this research financially.
文摘Gravity-induced drainage is one of the main destabilizing mechanisms for soap bubbles and foams.Here we show that solely through acoustic levitation without introducing any chemical stabilizers,liquid drainage in the bubble film can be completely inhibited,therefore leading to a significant enhancement of bubble lifetime by more than two orders of magnitude and enabling the bubble to survive puncturing by a needle.Based on sound simulation and force analysis,it has been found that acoustic radiation force,exerted on both the inner and outer surfaces of the levitated bubble,acts in opposite directions,thus providing a squeezing effect to the bubble film.The hydrostatic pressure that induces drainage has been balanced by the acoustic radiation pressure exerted on both sides of the film,which is at the origin of the sound stabilization mechanism.This study provides new insights into the interplay between sound and soap bubbles or films,thus stimulating a wide range of fundamental research concerning bubble films and expanding their applications in bio/chemical reactors.
基金This work was supported by the National Natural Science Foundation of China （No. 51672213） and the Natural Science Foundation of Shaanxi Province （Nos. 2017ZDCXL-GY-08-01 and 2017JM2025）.
文摘Layered molybdenum disulfide （MoS2） has received much attention as one of the most promising energy-storage and conversion materials for Li/Na ion batteries. Here, a simple and effective approach is proposed for the rational design and preparation of hierarchical three-d imensional （3D） amorphous N-doped carbon nanotube@MoS2 nanosheets （3D-ANCNT@MoS2） via a simple hydrothermal method, followed by an annealing process. With such a unique nanoarchitecture, ultrathin MoS2 nanosheets grown on the external surfaces of polypyrrole-derived ANCNTs are assembled to form a hierarchical 3D nanoarchitecture, where the adopted ANCNTs serve not only as the template and continuous conductive matrix, but can also prevent MoS2 from aggregating and restacking, and help to buffer the volumetric expansion of MoS2 during cycling. More importantly, when evaluated as an anode material for lithium-ion batteries, the 3D-ANCNT@MoS2 composite exhibits excellent cycling stability, superior rate performance, and reversible specific capacity as high as 893.4 mAh·g^-1 at 0.2 A·g^-1 after 200 cycles in a half battery, and 669.4 mAh·g^-1 at 0.2 A·g^-1 after 100 cycles in the 3D-ANCNT@Mo2//LiCoO2 full battery. With respect to sodium-ion batteries, the outstanding reversible capacity, excellent rate behavior, and good cycling performance of 3D-ANCNT@MoS2 composites are also achieved.
基金This work was supported by the National Key Research and Development Program of China(Grant number 2017YFA0701004)the National Natural Science Foundation of China(Grant numbers 61975251,61875150,61735012,and 11774288).
文摘Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bulk nonlinear crystals with millimetre thickness,with the bandwidth limited by the phase-matching condition.Here we demonstrate broadband THz emission via surface optical rectification from a simple,commercially available 19nmthick indium tin oxide(ITO)thin film.We show an enhancement of the generated THz signal when the pump laser is tuned around the epsilon-near-zero(ENZ)region of ITO due to the pump laser field enhancement associated with the ENZ effect.The bandwidth of the THz signal generated from the ITO film can be over 3 THz,unrestricted by the phasematching condition.This work offers a new possibility for broadband THz generation in a subwavelength thin film made of an ENZ material,with emerging physics not found in existing nonlinear crystals.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(No.22101182)Guangdong Basic and Applied Basic Research Foundation(No.2020A1515110499)+2 种基金Shenzhen Science and Technology Program(No.JCYJ20210324095202006),Shenzhen University Young Teacher Research Project(No.000002110713)the Shccig-Qinling Program(No.2021JLM-27)the Jinchuan Group Co.Ltd.Chemical Environmental Protection Industry Joint Laboratory(No.20-0837).
文摘To improve the atomic utilization of metals and reduce the cost of industrialization,the one-step total monoatomization of macroscopic bulk metals,as opposed to nanoscale metals,is effective.In this study,we used a thermal diffusion method to directly convert commercial centimeter-scale Ni foam to porous Ni single-atom-loaded carbon nanotubes(CNTs).As expected,owing to the coating of single-atom on porous,highly conductive CNT carriers,Ni single-atom electrocatalysts(Ni-SACs)exhibit extremely high activity and selectivity in CO_(2)electroreduction(CO_(2)RR),yielding a current density of>350 mA/cm^(2),a selectivity for CO of>91%under a flow cell configuration using a 1 M potassium chloride(KCl)electrolyte.Based on the superior activity of the Ni-SACs electrocatalyst,an integrated gas-phase electrochemical zero-gap reactor was introduced to generate a significant amount of CO current for potential practical applications.The overall current can be increased to 800 mA,while maintaining CO Faradaic efficiencies(FEs)at above 90%per unit cell.Our findings and insights on the active site transformation mechanism for macroscopic bulk Ni foam conversion into single atoms can inform the design of highly active single-atom catalysts used in industrial CO_(2)RR systems.
