In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited be...In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited beam quality using a master oscillation power amplifier. The RFL based on a half-opened cavity, which is composed of a linearly polarized narrow-linewidth fiber Bragg grating and a 500 m piece of polarization-maintained Ge-doped fiber, generates a 0.71 W seed laser with an 88 pm full width at half-maximum(FWHM) linewidth and a 22.5 dB polarization extinction ratio(PER) for power scaling. A two-stage fiber amplifier enhances the seed laser to the maximal 1.01 k W with a PER value of 17 dB and a beam quality of M_x^2=1.15 and M_y^2=1.13. No stimulated Brillouin scattering effect is observed at the ultimate power level, and the FWHM linewidth of the amplified random laser broadens linearly as a function of the output power with a coefficient of about 0.1237 pm∕W.To the best of our knowledge, this is the first demonstration of a linearly polarized narrow-linewidth RFL with even kilowatt-level near-diffraction-limited output, and further performance scaling is ongoing.展开更多
Two series of Mn/beta and Mn/ZSM‐5catalysts were prepared to study the influence of how different Mn precursors,introduced to the respective parent zeolites by wet impregnation,affected the selective catalytic reduct...Two series of Mn/beta and Mn/ZSM‐5catalysts were prepared to study the influence of how different Mn precursors,introduced to the respective parent zeolites by wet impregnation,affected the selective catalytic reduction(SCR)of NO by NH3across a low reaction temperature window of50–350°C.In this study,the catalysts were characterized using N2adsorption/desorption,X‐ray diffraction,X‐ray fluorescence,H2temperature‐programmed reduction,NH3temperature‐programmed desorption and X‐ray photoelectron spectroscopy.As the manganese chloride precursor only partially decomposed this primarily resulted in the formation of MnCl2in addition to the presence of low levels of crystalline Mn3O4,which resulted in poor catalytic performance.However,the manganese nitrate precursor formed crystalline MnO2as the major phase in addition to a minor presence of unconverted Mn‐nitrate.Furthermore,manganese acetate resulted principally in a mixture of amorphous Mn2O3and MnO2,and crystalline Mn3O4.From all the catalysts screened,the test performance data showed Mn/beta‐Ac to exhibit the highest NO conversion(97.5%)at240°C,which remained>90%across a temperature window of220–350°C.The excellent catalytic performance was ascribed to the enrichment of highly dispersed MnOx(Mn2O3and MnO2)species that act as the active phase in the NH3‐SCR process.Furthermore,together with a suitable amount of weakly acidic centers,higher concentration of surface manganese and a greater presence of surface labile oxygen groups,SCR performance was collectively enhanced at low temperature.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
In this paper,an all-fiberized and narrow-linewidth 5 kW power-level fiber amplifier is presented.The laser is achieved based on the master oscillator power amplification configuration,in which the phase-modulated sin...In this paper,an all-fiberized and narrow-linewidth 5 kW power-level fiber amplifier is presented.The laser is achieved based on the master oscillator power amplification configuration,in which the phase-modulated single-frequency laser is applied as the seed laser and a bidirectional pumping configuration is applied in the power amplifier.The stimulated Brillouin scattering,stimulated Raman scattering,and transverse mode instability effects are all effectively suppressed in the experiment.Consequently,the output power is scaled up to 4.92 kW with a slope efficiency of as high as approximately 80%.The 3-dB spectral width is about 0.59 nm,and the beam quality is measured to be M^(2)~1.22 at maximum output power.Furthermore,we have also conducted a detailed spectral analysis on the spectral width of the signal laser,which reveals that the spectral wing broadening phenomenon could lead to the obvious decrease of the spectral purity at certain output power.Overall,this work could provide a reference for obtaining and optimizing high-power narrow-linewidth fiber lasers.展开更多
With the increasing output power of the monolithic fiber laser oscillators,the stimulated Raman scattering(SRS)effect becomes one of the main limitations of power scaling.Employing fiber with a larger mode area is an ...With the increasing output power of the monolithic fiber laser oscillators,the stimulated Raman scattering(SRS)effect becomes one of the main limitations of power scaling.Employing fiber with a larger mode area is an effective technique to mitigate the SRS,but,for the monolithic fiber laser oscillators,the difficulty of the inscription of the high-reflection fiber Bragg gratings(FBGs)increases with the fiber mode area.In this work,we demonstrated a high-power monolithic fiber laser oscillator based on the home-made large mode area FBGs and ytterbium-doped fiber(YDF)with 25μm core diameters.A maximum output power of 4.05 kW is achieved at the central wavelength of-1080?nm with a total 915 nm pump power of-6.7 kW.At the operation of 4.05 kW,the intensity of the Raman Stokes light is-25 dB below the signal laser,and the beam quality(M^(2)-factor)is-2.2.To the best of our knowledge,this is the first detailed report of the monolithic fiber laser oscillator with an output power beyond 4 kW.展开更多
Global warming poses a serious threat to crops.Calcium-dependent protein kinases(CDPKs)/CPKs play vital roles in plant stress responses,but their exact roles in plant thermotolerance remains elusive.Here,we explored t...Global warming poses a serious threat to crops.Calcium-dependent protein kinases(CDPKs)/CPKs play vital roles in plant stress responses,but their exact roles in plant thermotolerance remains elusive.Here,we explored the roles of heat-induced ZmCDPK7 in thermotolerance in maize.ZmCDPK7-overexpressing maize plants displayed higher thermotolerance,photosynthetic rates,and antioxidant enzyme activity but lower H2 O2 and malondialdehyde(MDA)contents than wild-type plants under heat stress.ZmCDPK7-knockdown plants displayed the opposite patterns.ZmCDPK7 is attached to the plasma membrane but can translocate to the cytosol under heat stress.ZmCDPK7 interacts with the small heat shock protein sHSP17.4,phosphorylates sHSP17.4 at Ser-44 and the respiratory burst oxidase homolog RBOHB at Ser-99,and up regulates their expression.Site-directed mutagenesis of sHSP17.4 to generate a Ser-44-Ala substitution reduced ZmCDPK7’s enhancement of catalase activity but enhanced ZmCDPK7’s suppression of MDA accumulation in heat-stressed maize protoplasts.sHSP17.4,ZmCDPK7,and RBOHB were less strongly upregulated in response to heat stress in the abscisic acid-deficient mutant vp5 versus the wild type.Pretreatment with an RBOH inhibitor suppressed sHSP17.4 and ZmCDPK7 expression.Therefore,abscisic acid-induced ZmCDPK7 functions both upstream and downstream of RBOH and participates in thermotolerance in maize by mediating the phosphorylation of sHSP17.4,which might be essential for its chaperone function.展开更多
Atomically thin MoSe_(2) layers,as a core member of the transition metal dichalcogenides(TMDs)family,benefit from their appealing properties,including tunable band gaps,high exciton binding energies,and giant oscillat...Atomically thin MoSe_(2) layers,as a core member of the transition metal dichalcogenides(TMDs)family,benefit from their appealing properties,including tunable band gaps,high exciton binding energies,and giant oscillator strengths,thus pro-viding an intriguing platform for optoelectronic applications of light-emitting diodes(LEDs),field-effect transistors(FETs),sin-gle-photon emitters(SPEs),and coherent light sources(CLSs).Moreover,these MoSe_(2) layers can realize strong excitonic emis-sion in the near-infrared wavelengths,which can be combined with the silicon-based integration technologies and further encourage the development of the new generation technologies of on-chip optical interconnection,quantum computing,and quantum information processing.Herein,we overview the state-of-the-art applications of light-emitting devices based on two-dimensional MoSe_(2) layers.Firstly,we introduce recent developments in excitonic emission features from atomically thin MoSe_(2) and their dependences on typical physical fields.Next,we focus on the exciton-polaritons and plasmon-exciton polaritons in MoSe_(2) coupled to the diverse forms of optical microcavities.Then,we highlight the promising applications of LEDs,SPEs,and CLSs based on MoSe_(2) and their heterostructures.Finally,we summarize the challenges and opportunities for high-quality emis-sion of MoSe_(2) and high-performance light-emitting devices.展开更多
Light-induced recognition,assemblies,and materials are intensive areas of research due to their high spatiotemporal resolution.Herein,we demonstrated photoswitchable molecular recognition via dithienylethene-triggered...Light-induced recognition,assemblies,and materials are intensive areas of research due to their high spatiotemporal resolution.Herein,we demonstrated photoswitchable molecular recognition via dithienylethene-triggeredreversible structural regulation of dynamic covalent hydrazone bonds.By combining dithienylethenes and cyclic hemiacetals,the photochemical open-ring and closed-ring forms enabled turningoff and on the creation of awide range of hydrazones when desired.Light-induced bidirectional switching between hydrazones and their cyclization structures promoted by a neighboring carboxyl group was further achieved.By taking advantage of reversible structural changes totoggleon andoff the binding pocket,photoswitchable recognitionofmetal ionswas realized.Finally,the construction of an acylhydrazone polymer offered a facile way for light-mediated selective extraction/release.The strategies and results reported here should find applications in many contexts,such asdynamicassemblies,molecular switches,and smart materials.展开更多
Traditional multicolor fluorescent hydrogels are generated through the assembly of discrete fluorescent hydrogels,which is not a complete integration much distinct from living organisms.On the basis of aggregation-ind...Traditional multicolor fluorescent hydrogels are generated through the assembly of discrete fluorescent hydrogels,which is not a complete integration much distinct from living organisms.On the basis of aggregation-induced emission(AIE),a special solvent polar-responsive AIE molecule possessing a twisted intramolecular charge transfer(TICT)effect was noticed.By incorporating it into the gel network,an AIE gel that displays continuous gradient fluorescence was fabricated.First,hydrogel A containing the solvent polar-responsive AIE-gen was prepared to show orange fluorescence.After soaking in the organic solvents,the fluorescence color transition of hydrogel A ranging from orange to green occurred when being immersed in high-polarity organic solvents ascribed to the embedded AIE-gen owning TICT effect.Then,hydrogel A was successively lifted up from organic solvents.Due to the different immersion time of each section for the hydrogel,the polarity difference occurred.Then,the produced gel B showed continuous gradient fluorescence ranging from orange to green under the irradiation of UV light.展开更多
This study presents the development of an ultrasonic transducer with a radius horn for an ultrasonic milling spindle(UMS)system.The ultrasonic transducer was intended to have a working frequency of approximately 30 kH...This study presents the development of an ultrasonic transducer with a radius horn for an ultrasonic milling spindle(UMS)system.The ultrasonic transducer was intended to have a working frequency of approximately 30 kHz.Two different materials were considered in the study:stainless steel(SS 316L)and titanium alloy(Ti-6Al-4V).Titanium alloy gave a higher resonance frequency(33 kHz)than stainless steel(30 kHz)under the same preload compression stress.An electromechanical impedance simulation was carried out to predict the impedance resonance frequency for both materials,and the effect of the overhanging toolbar was investigated.According to the electromechanical impedance simulation,the overhanging toolbar length affected the resonance frequency,and the error was less than 3%.Harmonic analysis confirmed that the damping ratio helps determine the resonance amplitude.Therefore,damping ratios of 0.015-0.020 and 0.005-0.020 were selected for stainless steel and titanium alloy,respectively,with an error of less than 1.5%.Experimental machining was also performed to assess the feasibility of ultrasonic-assisted milling;the result was a lesser cutting force and better surface topography of Al 6061.展开更多
Compared with traditional uniform fibers, tapered fiber has numerous unique advantages, such as larger mode area,higher pump absorption, suppression to nonlinear effects, and maintaining good beam quality. In this man...Compared with traditional uniform fibers, tapered fiber has numerous unique advantages, such as larger mode area,higher pump absorption, suppression to nonlinear effects, and maintaining good beam quality. In this manuscript, we have constructed an all-fiberized fiber amplifier which is based on a piece of ytterbium-doped tapered double-clad fiber(T-DCF). The fiber amplifier is operated under continuous wave(CW) regime at 1080 nm wavelength. The M2 factor of the amplifier at 1.39 k W output power is ～1.8. The maximum output power of the system reached 1.47 k W, which, to the best of our knowledge, is the highest output power of long tapered fiber based fiber laser system. Our result successfully verifies the potential of power scalability and all-fiberized capability of long tapered fiber, and the performance of our system can be further enhanced by fiber design optimization.展开更多
In recent years,humanized immune system(HIS)mice have been gradually used as models for preclinical research in pharmacotherapies and cell therapies with major breakthroughs in tumor and other fields,better mimicking ...In recent years,humanized immune system(HIS)mice have been gradually used as models for preclinical research in pharmacotherapies and cell therapies with major breakthroughs in tumor and other fields,better mimicking the human immune system and the tumor immune microenvironment,compared to traditional immunodeficient mice.To better promote the application of HIS mice in preclinical research,we se-lectively summarize the current prevalent and breakthrough research and evaluation of chimeric antigen receptor(CAR)-T cells in various antiviral and antitumor treat-ments.By exploring its application in preclinical research,we find that it can better reflect the actual clinical patient condition,with the advantages of providing high-efficiency detection indicators,even for progressive research and development.We believe that it has better clinical patient simulation and promotion for the updated design of CAR-T cell therapy than directly transplanted immunodeficient mice.The characteristics of the main models are proposed to improve the use defects of the existing models by reducing the limitation of antihost reaction,combining multiple models,and unifying sources and organoid substitution.Strategy study of relapse and toxicity after CAR-T treatment also provides more possibilities for application and development.展开更多
A 2×3 kW-level bidirectional output fiber oscillator is realized by combining the specially designed spindle-shaped ytterbium-doped fiber,non-wavelength-stabilized 976-nm LDs,and grating bandwidth optimization to...A 2×3 kW-level bidirectional output fiber oscillator is realized by combining the specially designed spindle-shaped ytterbium-doped fiber,non-wavelength-stabilized 976-nm LDs,and grating bandwidth optimization to balance transverse mode instability and stimulated Raman scattering.The maximum output powers at both ends are 3265 and 2840 W,respectively,with a total efficiency of 73.2%.The M^(2) factors of the lasers at both ends are about 1.98 and 2.38,respectively.The beam profile at both ends shows that a bidirectional output annular beam fiber oscillator has been realized,which has great potential in practical applications.展开更多
The safety issues of lithium-ion batteries have received attention because flammable organic electrolytes are used.Also,the commercial polyolefin separator will undergo severe thermal shrinkage when the internal tempe...The safety issues of lithium-ion batteries have received attention because flammable organic electrolytes are used.Also,the commercial polyolefin separator will undergo severe thermal shrinkage when the internal temperature of the battery increases to 130-160°C,which increases the risk.Therefore,the development of a high thermal stability and high-safety separator is an effective strategy to improve battery safety.Herein,we design a green,cellulose-based separator(Cel@DBDPE)with a unique encapsulation structure for lithium-ion batteries,in which functional flame retardants(DBDPE)are wrapped in microscrolls formed by the self-rolling of 2D cellulose nanosheets upon freeze-drying.This structure can firmly anchor DBDPE particles in the separator to prevent them from undergoing exfoliation and does not affect the properties of the separator,such as the thickness and the pore structure.Compared with commercial polypropylene,Cel@DBDPE has excellent thermal stability and flame retardancy.The former makes it less prone to thermal shrinkage and the latter can effectively prevent the combustion of the electrolyte,showing an efficient self-extinguishing ability.Moreover,the Cel@DBDPE is only 15μm in size and has competitive properties comparable to polypropylene.Thus,there is no sacrifice in the electrochemical performance of battery when the Cel@DBDPE is used as separator.This study provides a new structural design for the construction of a high-safety separator.展开更多
Temporal intensity fluctuation is one of the inherent features of fiber lasers.When utilizing the fiber lasers to pump a random Raman fiber laser(RRFL),the intensity fluctuation transfer from the pump to the random la...Temporal intensity fluctuation is one of the inherent features of fiber lasers.When utilizing the fiber lasers to pump a random Raman fiber laser(RRFL),the intensity fluctuation transfer from the pump to the random lasing could affect the output performance significantly.In this paper,we comprehensively compared the spectral,temporal,and power characteristics of an RRFL pumped by two different fiber lasers—a temporally unstable fiber oscillator and a temporally stable amplified spontaneous emission(ASE)source.Owing to less impact of the intensity fluctuation transfer,the ASE source-pumped RRFL shows∼45.3%higher maximum output power,higher spectral purity(>99.9%)and optical signal-to-noise ratio(>40dB),weaker spectral broadening,and more stable temporal behavior compared to the fiber oscillator-pumped RRFL.Furthermore,based on the temporal-spatial-coupled Raman equations and the generalized nonlinear Schrödinger equations,we numerically revealed the impact of the pump intensity fluctuations on the output characteristics of RRFLs,and found that the temporal walk-off effect played an important role in the dynamics of intensity fluctuation transfer.This work may provide a reference for designing and implementing high-performance RRFLs and promote their practicability in sensing,telecommunications,and high-power applications.展开更多
The identification of the decay pathway of the nucleobase uracil after being photoexcited by ultraviolet light has been a long-standing problem.Various theoretical models have been proposed but yet to be verified.Here...The identification of the decay pathway of the nucleobase uracil after being photoexcited by ultraviolet light has been a long-standing problem.Various theoretical models have been proposed but yet to be verified.Here,we propose an experimental scheme to test the theoretical models of gas phase uracil decay mechanism by a combination of ultrafast x-ray spectroscopy,x-ray diffraction,and electron diffraction methods.Incorporating the signatures of multiple probing methods,we demonstrate an approach that can identify the dominant mechanism of the geometric and electronic relaxation of the photoexcited uracil molecule among several candidate models.展开更多
Power scaling based on traditional ytterbium-doped fibers(YDFs)is limited by optical nonlinear effects and transverse mode instability(TMI)in high-power fiber lasers.Here,we propose a novel long tapered fiber with a c...Power scaling based on traditional ytterbium-doped fibers(YDFs)is limited by optical nonlinear effects and transverse mode instability(TMI)in high-power fiber lasers.Here,we propose a novel long tapered fiber with a constant cladding and tapered core(CCTC)along its axis direction.The tapered-core region of the fiber is designed to enhance the stimulated Raman scattering(SRS)threshold and suppress higher-order mode resonance in the laser cavity.The CCTC YDF was fabricated successfully with a modified chemical vapor deposition(MCVD)method combined with solution doping technology,which has a cladding diameter of 400µm and a varying core with a diameter of~24μm at both ends and~31μm in the middle.To test the performance of the CCTC fiber during high-power operation,an all-fiber laser oscillator based on a CCTC YDF was investigated experimentally.As a result,a maximum output power of 3.42 kW was achieved with an optical-to-optical efficiency of 55.2%,although the TMI effect was observed at an output power of~3.12 kW.The measured beam quality(M^(2)factor)was~1.7,and no sign of the Raman component was observed in the spectrum.We believe that CCTC YDF has great potential to simultaneously mitigate the SRS and TMI effects,and further power scaling is promising by optimizing the structure of the YDF.展开更多
Unlike a traditional fiber laser with a defined resonant cavity, a random fiber laser(RFL), whose operation is based on distributed feedback and gain via Rayleigh scattering(RS) and stimulated Raman scattering in a lo...Unlike a traditional fiber laser with a defined resonant cavity, a random fiber laser(RFL), whose operation is based on distributed feedback and gain via Rayleigh scattering(RS) and stimulated Raman scattering in a long passive fiber, has fundamental scientific challenges in pulsing operation for its remarkable cavity-free feature. For the time being, stable pulsed RFL utilizing a passive method has not been reported. Here, we propose and experimentally realize the passive spatiotemporal gain-modulation-induced stable pulsing operation of counterpumped RFL. Thanks to the good temporal stability of an employed pumping amplified spontaneous emission source and the superiority of this pulse generation scheme, a stable and regular pulse train can be obtained.Furthermore, the pump hysteresis and bistability phenomena with the generation of high-order Stokes light is presented, and the dynamics of pulsing operation is discussed after the theoretical investigation of the counterpumped RFL. This work extends our comprehension of temporal property of RFL and paves an effective novel avenue for the exploration of pulsed RFL with structural simplicity, low cost, and stable output.展开更多
Strongly bound excitons in atomically thin transition metal dichalcogenides offer many opportunities to reveal the underlying physics of basic quasiparticles and many-body effects in the two-dimensional(2D)limit.Compr...Strongly bound excitons in atomically thin transition metal dichalcogenides offer many opportunities to reveal the underlying physics of basic quasiparticles and many-body effects in the two-dimensional(2D)limit.Comprehensive reflection investigation on band-edge exciton transitions is essential to exploring wealthy light–matter interactions in the emerging 2D semiconductors,whereas angle-resolved reflection(ARR)characteristics of intralayer and interlayer excitons in 2D MoS_(2)layers remain unclear.Herein,we report ARR spectroscopic features of A,B,interlayer excitons in monolayer(ML)and bilayer(BL)MoS_(2)on three kinds of photonic substrates,involving distinct exciton–photon interactions.In a BL MoS_(2)on a protected silver mirror,the interlayer exciton with one-third amplitude of A exciton appears at 0.05 eV above the A exciton energy,exhibiting an angleinsensitive energy dispersion.When ML and BL MoS_(2)lie on a SiO_(2)-covered silicon,the broad trapped-photon mode weakly couples with the reflection bands of A and B excitons by the Fano resonance effect,causing the asymmetric lineshapes and the redshifted energies.After transferring MoS_(2)layers onto a one-dimensional photonic crystal,two high-lying branches of B-exciton polaritons are formed by the interactions between B excitons and Bragg photons,beyond the weak-coupling regime.This work provides ARR spectral benchmarks of A,B,interlayer excitons in ML and BL MoS_(2),gaining insights into the interpretation of light–matter interactions in 2D semiconductors and the design of their devices for practical photonic applications.展开更多
基金National Natural Science Foundation of China(NSFC)(61322505,61635005)
文摘In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited beam quality using a master oscillation power amplifier. The RFL based on a half-opened cavity, which is composed of a linearly polarized narrow-linewidth fiber Bragg grating and a 500 m piece of polarization-maintained Ge-doped fiber, generates a 0.71 W seed laser with an 88 pm full width at half-maximum(FWHM) linewidth and a 22.5 dB polarization extinction ratio(PER) for power scaling. A two-stage fiber amplifier enhances the seed laser to the maximal 1.01 k W with a PER value of 17 dB and a beam quality of M_x^2=1.15 and M_y^2=1.13. No stimulated Brillouin scattering effect is observed at the ultimate power level, and the FWHM linewidth of the amplified random laser broadens linearly as a function of the output power with a coefficient of about 0.1237 pm∕W.To the best of our knowledge, this is the first demonstration of a linearly polarized narrow-linewidth RFL with even kilowatt-level near-diffraction-limited output, and further performance scaling is ongoing.
基金supported by the National Science and Technology Program of China(CDGC01-KT16)~~
文摘Two series of Mn/beta and Mn/ZSM‐5catalysts were prepared to study the influence of how different Mn precursors,introduced to the respective parent zeolites by wet impregnation,affected the selective catalytic reduction(SCR)of NO by NH3across a low reaction temperature window of50–350°C.In this study,the catalysts were characterized using N2adsorption/desorption,X‐ray diffraction,X‐ray fluorescence,H2temperature‐programmed reduction,NH3temperature‐programmed desorption and X‐ray photoelectron spectroscopy.As the manganese chloride precursor only partially decomposed this primarily resulted in the formation of MnCl2in addition to the presence of low levels of crystalline Mn3O4,which resulted in poor catalytic performance.However,the manganese nitrate precursor formed crystalline MnO2as the major phase in addition to a minor presence of unconverted Mn‐nitrate.Furthermore,manganese acetate resulted principally in a mixture of amorphous Mn2O3and MnO2,and crystalline Mn3O4.From all the catalysts screened,the test performance data showed Mn/beta‐Ac to exhibit the highest NO conversion(97.5%)at240°C,which remained>90%across a temperature window of220–350°C.The excellent catalytic performance was ascribed to the enrichment of highly dispersed MnOx(Mn2O3and MnO2)species that act as the active phase in the NH3‐SCR process.Furthermore,together with a suitable amount of weakly acidic centers,higher concentration of surface manganese and a greater presence of surface labile oxygen groups,SCR performance was collectively enhanced at low temperature.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
基金supported by the Guangdong Key Research and Development Program(No.2018B090904001)the National Natural Science Foundations of China(Nos.62005313 and 61705264)+1 种基金the Innovative Research Team in Natural Science Foundation of Hunan Province(No.2019JJ10005)the Hunan Provincial Innovation Construct Project(No.2019RS3017)。
文摘In this paper,an all-fiberized and narrow-linewidth 5 kW power-level fiber amplifier is presented.The laser is achieved based on the master oscillator power amplification configuration,in which the phase-modulated single-frequency laser is applied as the seed laser and a bidirectional pumping configuration is applied in the power amplifier.The stimulated Brillouin scattering,stimulated Raman scattering,and transverse mode instability effects are all effectively suppressed in the experiment.Consequently,the output power is scaled up to 4.92 kW with a slope efficiency of as high as approximately 80%.The 3-dB spectral width is about 0.59 nm,and the beam quality is measured to be M^(2)~1.22 at maximum output power.Furthermore,we have also conducted a detailed spectral analysis on the spectral width of the signal laser,which reveals that the spectral wing broadening phenomenon could lead to the obvious decrease of the spectral purity at certain output power.Overall,this work could provide a reference for obtaining and optimizing high-power narrow-linewidth fiber lasers.
基金supported by the National Key R&D Program of China(No.2016YFB0402204)the National Natural Science Foundation of China(Nos.61735007,61377062,and 61505260)
文摘With the increasing output power of the monolithic fiber laser oscillators,the stimulated Raman scattering(SRS)effect becomes one of the main limitations of power scaling.Employing fiber with a larger mode area is an effective technique to mitigate the SRS,but,for the monolithic fiber laser oscillators,the difficulty of the inscription of the high-reflection fiber Bragg gratings(FBGs)increases with the fiber mode area.In this work,we demonstrated a high-power monolithic fiber laser oscillator based on the home-made large mode area FBGs and ytterbium-doped fiber(YDF)with 25μm core diameters.A maximum output power of 4.05 kW is achieved at the central wavelength of-1080?nm with a total 915 nm pump power of-6.7 kW.At the operation of 4.05 kW,the intensity of the Raman Stokes light is-25 dB below the signal laser,and the beam quality(M^(2)-factor)is-2.2.To the best of our knowledge,this is the first detailed report of the monolithic fiber laser oscillator with an output power beyond 4 kW.
基金supported by the National Natural Science Foundation of Henan Joint Fund(U1604101 to XLH)the Key R&D and Promotion Projects of Henan Province(192102110009 to XLH,192102110004 to HY)。
文摘Global warming poses a serious threat to crops.Calcium-dependent protein kinases(CDPKs)/CPKs play vital roles in plant stress responses,but their exact roles in plant thermotolerance remains elusive.Here,we explored the roles of heat-induced ZmCDPK7 in thermotolerance in maize.ZmCDPK7-overexpressing maize plants displayed higher thermotolerance,photosynthetic rates,and antioxidant enzyme activity but lower H2 O2 and malondialdehyde(MDA)contents than wild-type plants under heat stress.ZmCDPK7-knockdown plants displayed the opposite patterns.ZmCDPK7 is attached to the plasma membrane but can translocate to the cytosol under heat stress.ZmCDPK7 interacts with the small heat shock protein sHSP17.4,phosphorylates sHSP17.4 at Ser-44 and the respiratory burst oxidase homolog RBOHB at Ser-99,and up regulates their expression.Site-directed mutagenesis of sHSP17.4 to generate a Ser-44-Ala substitution reduced ZmCDPK7’s enhancement of catalase activity but enhanced ZmCDPK7’s suppression of MDA accumulation in heat-stressed maize protoplasts.sHSP17.4,ZmCDPK7,and RBOHB were less strongly upregulated in response to heat stress in the abscisic acid-deficient mutant vp5 versus the wild type.Pretreatment with an RBOH inhibitor suppressed sHSP17.4 and ZmCDPK7 expression.Therefore,abscisic acid-induced ZmCDPK7 functions both upstream and downstream of RBOH and participates in thermotolerance in maize by mediating the phosphorylation of sHSP17.4,which might be essential for its chaperone function.
基金This work is supported by the National Natural Science Foundation of China(No.61904151)the National Key Research and Development Program of China(No.2021YFA1200803)the Joint Research Funds of the Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(No.2020GXLH-Z-020).
文摘Atomically thin MoSe_(2) layers,as a core member of the transition metal dichalcogenides(TMDs)family,benefit from their appealing properties,including tunable band gaps,high exciton binding energies,and giant oscillator strengths,thus pro-viding an intriguing platform for optoelectronic applications of light-emitting diodes(LEDs),field-effect transistors(FETs),sin-gle-photon emitters(SPEs),and coherent light sources(CLSs).Moreover,these MoSe_(2) layers can realize strong excitonic emis-sion in the near-infrared wavelengths,which can be combined with the silicon-based integration technologies and further encourage the development of the new generation technologies of on-chip optical interconnection,quantum computing,and quantum information processing.Herein,we overview the state-of-the-art applications of light-emitting devices based on two-dimensional MoSe_(2) layers.Firstly,we introduce recent developments in excitonic emission features from atomically thin MoSe_(2) and their dependences on typical physical fields.Next,we focus on the exciton-polaritons and plasmon-exciton polaritons in MoSe_(2) coupled to the diverse forms of optical microcavities.Then,we highlight the promising applications of LEDs,SPEs,and CLSs based on MoSe_(2) and their heterostructures.Finally,we summarize the challenges and opportunities for high-quality emis-sion of MoSe_(2) and high-performance light-emitting devices.
基金supported by National Natural Science Foundation of China(grant nos.22071247,92156010,22101283,and 22101284)the Strategic Priority Research Program(grant no.XDB20000000)+1 种基金the Key Research Program of Frontier Sciences(grant no.QYZDBSSW-SLH030)of the Chinese Academy of Sciences,Natural Science Foundation of Fujian Province(grant nos.2020J06035 and 2022J05085)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(grant no.2021ZR112).
文摘Light-induced recognition,assemblies,and materials are intensive areas of research due to their high spatiotemporal resolution.Herein,we demonstrated photoswitchable molecular recognition via dithienylethene-triggeredreversible structural regulation of dynamic covalent hydrazone bonds.By combining dithienylethenes and cyclic hemiacetals,the photochemical open-ring and closed-ring forms enabled turningoff and on the creation of awide range of hydrazones when desired.Light-induced bidirectional switching between hydrazones and their cyclization structures promoted by a neighboring carboxyl group was further achieved.By taking advantage of reversible structural changes totoggleon andoff the binding pocket,photoswitchable recognitionofmetal ionswas realized.Finally,the construction of an acylhydrazone polymer offered a facile way for light-mediated selective extraction/release.The strategies and results reported here should find applications in many contexts,such asdynamicassemblies,molecular switches,and smart materials.
基金funding from the National Natural Science Foundation of China (No.22001087)support from the Huazhong University of Science and Technology,where he is being supported by Fundamental Research Funds for the Central Universities (No.2020kfyXJJS013)+2 种基金support from the Open Fund of Hubei Key Laboratory of Material Chemistry and Service Failure,Huazhong University of Science and Technology (No.2020MCF08)the Open Research Fund (No.2021JYBKF01)of Key Laboratory of Material Chemistry for Energy Conversion and Storage,Huazhong University of Science and Technology,Ministry of Educationfunding from Shenzhen Key Laboratory of Functional Aggregate Materials (No.ZDSYS20211021111400001).
文摘Traditional multicolor fluorescent hydrogels are generated through the assembly of discrete fluorescent hydrogels,which is not a complete integration much distinct from living organisms.On the basis of aggregation-induced emission(AIE),a special solvent polar-responsive AIE molecule possessing a twisted intramolecular charge transfer(TICT)effect was noticed.By incorporating it into the gel network,an AIE gel that displays continuous gradient fluorescence was fabricated.First,hydrogel A containing the solvent polar-responsive AIE-gen was prepared to show orange fluorescence.After soaking in the organic solvents,the fluorescence color transition of hydrogel A ranging from orange to green occurred when being immersed in high-polarity organic solvents ascribed to the embedded AIE-gen owning TICT effect.Then,hydrogel A was successively lifted up from organic solvents.Due to the different immersion time of each section for the hydrogel,the polarity difference occurred.Then,the produced gel B showed continuous gradient fluorescence ranging from orange to green under the irradiation of UV light.
基金supported by Korea Electrotechnology Research Institute(KERI)Primary Research Program through the National Research Council of Science&Technology(NST)funded by the Ministry of Science and ICT(MSIT)in 2023(No.23A01021)the National Research Foundation of Korea(NRF)grant funded by the Korean Government(MSIT)(No.RS-2023-00278890).
文摘This study presents the development of an ultrasonic transducer with a radius horn for an ultrasonic milling spindle(UMS)system.The ultrasonic transducer was intended to have a working frequency of approximately 30 kHz.Two different materials were considered in the study:stainless steel(SS 316L)and titanium alloy(Ti-6Al-4V).Titanium alloy gave a higher resonance frequency(33 kHz)than stainless steel(30 kHz)under the same preload compression stress.An electromechanical impedance simulation was carried out to predict the impedance resonance frequency for both materials,and the effect of the overhanging toolbar was investigated.According to the electromechanical impedance simulation,the overhanging toolbar length affected the resonance frequency,and the error was less than 3%.Harmonic analysis confirmed that the damping ratio helps determine the resonance amplitude.Therefore,damping ratios of 0.015-0.020 and 0.005-0.020 were selected for stainless steel and titanium alloy,respectively,with an error of less than 1.5%.Experimental machining was also performed to assess the feasibility of ultrasonic-assisted milling;the result was a lesser cutting force and better surface topography of Al 6061.
基金supported by the National Natural Science Foundation of China(No.61505260)the National Key Research and Development Program of China(No.2016YFB0402204)
文摘Compared with traditional uniform fibers, tapered fiber has numerous unique advantages, such as larger mode area,higher pump absorption, suppression to nonlinear effects, and maintaining good beam quality. In this manuscript, we have constructed an all-fiberized fiber amplifier which is based on a piece of ytterbium-doped tapered double-clad fiber(T-DCF). The fiber amplifier is operated under continuous wave(CW) regime at 1080 nm wavelength. The M2 factor of the amplifier at 1.39 k W output power is ～1.8. The maximum output power of the system reached 1.47 k W, which, to the best of our knowledge, is the highest output power of long tapered fiber based fiber laser system. Our result successfully verifies the potential of power scalability and all-fiberized capability of long tapered fiber, and the performance of our system can be further enhanced by fiber design optimization.
基金CAMS Innovation Fund for Medical Sciences,Grant/Award Number:2021-I2M-1-035National Key Research and Development Project,Grant/Award Number:2022YFA1103803。
文摘In recent years,humanized immune system(HIS)mice have been gradually used as models for preclinical research in pharmacotherapies and cell therapies with major breakthroughs in tumor and other fields,better mimicking the human immune system and the tumor immune microenvironment,compared to traditional immunodeficient mice.To better promote the application of HIS mice in preclinical research,we se-lectively summarize the current prevalent and breakthrough research and evaluation of chimeric antigen receptor(CAR)-T cells in various antiviral and antitumor treat-ments.By exploring its application in preclinical research,we find that it can better reflect the actual clinical patient condition,with the advantages of providing high-efficiency detection indicators,even for progressive research and development.We believe that it has better clinical patient simulation and promotion for the updated design of CAR-T cell therapy than directly transplanted immunodeficient mice.The characteristics of the main models are proposed to improve the use defects of the existing models by reducing the limitation of antihost reaction,combining multiple models,and unifying sources and organoid substitution.Strategy study of relapse and toxicity after CAR-T treatment also provides more possibilities for application and development.
基金supported by the Funding for Distinguished Yong Scholars of Hunan Province(No.2023JJ10057)the Training Program for Excellent Young Innovations of Changsha(No.kq2305038)the Basic Scientific Research Program(No.JCKY2021525B015).
文摘A 2×3 kW-level bidirectional output fiber oscillator is realized by combining the specially designed spindle-shaped ytterbium-doped fiber,non-wavelength-stabilized 976-nm LDs,and grating bandwidth optimization to balance transverse mode instability and stimulated Raman scattering.The maximum output powers at both ends are 3265 and 2840 W,respectively,with a total efficiency of 73.2%.The M^(2) factors of the lasers at both ends are about 1.98 and 2.38,respectively.The beam profile at both ends shows that a bidirectional output annular beam fiber oscillator has been realized,which has great potential in practical applications.
基金supported by the National Natural Science Foundation of China(Nos.U22A20140,52072138)the National Key Research and Development Program of China(No.2018YFE0206900).
文摘The safety issues of lithium-ion batteries have received attention because flammable organic electrolytes are used.Also,the commercial polyolefin separator will undergo severe thermal shrinkage when the internal temperature of the battery increases to 130-160°C,which increases the risk.Therefore,the development of a high thermal stability and high-safety separator is an effective strategy to improve battery safety.Herein,we design a green,cellulose-based separator(Cel@DBDPE)with a unique encapsulation structure for lithium-ion batteries,in which functional flame retardants(DBDPE)are wrapped in microscrolls formed by the self-rolling of 2D cellulose nanosheets upon freeze-drying.This structure can firmly anchor DBDPE particles in the separator to prevent them from undergoing exfoliation and does not affect the properties of the separator,such as the thickness and the pore structure.Compared with commercial polypropylene,Cel@DBDPE has excellent thermal stability and flame retardancy.The former makes it less prone to thermal shrinkage and the latter can effectively prevent the combustion of the electrolyte,showing an efficient self-extinguishing ability.Moreover,the Cel@DBDPE is only 15μm in size and has competitive properties comparable to polypropylene.Thus,there is no sacrifice in the electrochemical performance of battery when the Cel@DBDPE is used as separator.This study provides a new structural design for the construction of a high-safety separator.
基金Hunan Provincial Innovation Construct Project(2019RS3018)National Natural Science Foundation of China(61905284,62061136013).
文摘Temporal intensity fluctuation is one of the inherent features of fiber lasers.When utilizing the fiber lasers to pump a random Raman fiber laser(RRFL),the intensity fluctuation transfer from the pump to the random lasing could affect the output performance significantly.In this paper,we comprehensively compared the spectral,temporal,and power characteristics of an RRFL pumped by two different fiber lasers—a temporally unstable fiber oscillator and a temporally stable amplified spontaneous emission(ASE)source.Owing to less impact of the intensity fluctuation transfer,the ASE source-pumped RRFL shows∼45.3%higher maximum output power,higher spectral purity(>99.9%)and optical signal-to-noise ratio(>40dB),weaker spectral broadening,and more stable temporal behavior compared to the fiber oscillator-pumped RRFL.Furthermore,based on the temporal-spatial-coupled Raman equations and the generalized nonlinear Schrödinger equations,we numerically revealed the impact of the pump intensity fluctuations on the output characteristics of RRFLs,and found that the temporal walk-off effect played an important role in the dynamics of intensity fluctuation transfer.This work may provide a reference for designing and implementing high-performance RRFLs and promote their practicability in sensing,telecommunications,and high-power applications.
基金supported by the National Natural Science Foundation of China[grant numbers 12174009,11974031,12104082,12234002,and 92250303]Beijing Natural Science Foundation[grant number Z220008]N.M.gratefully acknowledges financial support from the Czech Ministry of Education,Youth,and Sports[grantnumbers LTT17015,LM2018114,and EF16_013/0001552].
文摘The identification of the decay pathway of the nucleobase uracil after being photoexcited by ultraviolet light has been a long-standing problem.Various theoretical models have been proposed but yet to be verified.Here,we propose an experimental scheme to test the theoretical models of gas phase uracil decay mechanism by a combination of ultrafast x-ray spectroscopy,x-ray diffraction,and electron diffraction methods.Incorporating the signatures of multiple probing methods,we demonstrate an approach that can identify the dominant mechanism of the geometric and electronic relaxation of the photoexcited uracil molecule among several candidate models.
基金the National Natural Science Foundation of China(Nos.61735007 and 61705266).
文摘Power scaling based on traditional ytterbium-doped fibers(YDFs)is limited by optical nonlinear effects and transverse mode instability(TMI)in high-power fiber lasers.Here,we propose a novel long tapered fiber with a constant cladding and tapered core(CCTC)along its axis direction.The tapered-core region of the fiber is designed to enhance the stimulated Raman scattering(SRS)threshold and suppress higher-order mode resonance in the laser cavity.The CCTC YDF was fabricated successfully with a modified chemical vapor deposition(MCVD)method combined with solution doping technology,which has a cladding diameter of 400µm and a varying core with a diameter of~24μm at both ends and~31μm in the middle.To test the performance of the CCTC fiber during high-power operation,an all-fiber laser oscillator based on a CCTC YDF was investigated experimentally.As a result,a maximum output power of 3.42 kW was achieved with an optical-to-optical efficiency of 55.2%,although the TMI effect was observed at an output power of~3.12 kW.The measured beam quality(M^(2)factor)was~1.7,and no sign of the Raman component was observed in the spectrum.We believe that CCTC YDF has great potential to simultaneously mitigate the SRS and TMI effects,and further power scaling is promising by optimizing the structure of the YDF.
基金National Natural Science Foundation of China(NSFC)(61322505,61635005)Hunan Provincial Innovation Foundation for Postgraduate Student(CX2017B030)
文摘Unlike a traditional fiber laser with a defined resonant cavity, a random fiber laser(RFL), whose operation is based on distributed feedback and gain via Rayleigh scattering(RS) and stimulated Raman scattering in a long passive fiber, has fundamental scientific challenges in pulsing operation for its remarkable cavity-free feature. For the time being, stable pulsed RFL utilizing a passive method has not been reported. Here, we propose and experimentally realize the passive spatiotemporal gain-modulation-induced stable pulsing operation of counterpumped RFL. Thanks to the good temporal stability of an employed pumping amplified spontaneous emission source and the superiority of this pulse generation scheme, a stable and regular pulse train can be obtained.Furthermore, the pump hysteresis and bistability phenomena with the generation of high-order Stokes light is presented, and the dynamics of pulsing operation is discussed after the theoretical investigation of the counterpumped RFL. This work extends our comprehension of temporal property of RFL and paves an effective novel avenue for the exploration of pulsed RFL with structural simplicity, low cost, and stable output.
基金the National Natural Science Foundation of China(No.61904151)the Joint Research Funds of the Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(No.2020GXLH-Z-020)+1 种基金the Fundamental Research Funds for the Central Universities of China,the National Key R&D Program of China(No.2021YFA1200800)the Start-up Funds of Wuhan University.
文摘Strongly bound excitons in atomically thin transition metal dichalcogenides offer many opportunities to reveal the underlying physics of basic quasiparticles and many-body effects in the two-dimensional(2D)limit.Comprehensive reflection investigation on band-edge exciton transitions is essential to exploring wealthy light–matter interactions in the emerging 2D semiconductors,whereas angle-resolved reflection(ARR)characteristics of intralayer and interlayer excitons in 2D MoS_(2)layers remain unclear.Herein,we report ARR spectroscopic features of A,B,interlayer excitons in monolayer(ML)and bilayer(BL)MoS_(2)on three kinds of photonic substrates,involving distinct exciton–photon interactions.In a BL MoS_(2)on a protected silver mirror,the interlayer exciton with one-third amplitude of A exciton appears at 0.05 eV above the A exciton energy,exhibiting an angleinsensitive energy dispersion.When ML and BL MoS_(2)lie on a SiO_(2)-covered silicon,the broad trapped-photon mode weakly couples with the reflection bands of A and B excitons by the Fano resonance effect,causing the asymmetric lineshapes and the redshifted energies.After transferring MoS_(2)layers onto a one-dimensional photonic crystal,two high-lying branches of B-exciton polaritons are formed by the interactions between B excitons and Bragg photons,beyond the weak-coupling regime.This work provides ARR spectral benchmarks of A,B,interlayer excitons in ML and BL MoS_(2),gaining insights into the interpretation of light–matter interactions in 2D semiconductors and the design of their devices for practical photonic applications.
