Intrinsic topological superconductors have garnered significant attention for their potential to harbor novel quantum phenomena.However,the limited availability of suitable material systems has hindered progress in th...Intrinsic topological superconductors have garnered significant attention for their potential to harbor novel quantum phenomena.However,the limited availability of suitable material systems has hindered progress in this field.Here,we present the synthesis and characterization of high-quality self-assembled SnS/TaS_(2)(SnTaS_(3))superlattice,which exhibits superconductivity alongside non-trivial band topology.Temperature-dependent magnetization susceptibility and electrical transport results confirm SnTaS_(3) as a type-Ⅱ superconductor with a critical transition temperature Tc of 3 K.Interestingly,this superconductivity can be turned off via an innovative solid proton gate technique,and a new superconducting state with a Tc of~2.3 K emerges when the gating voltage reaches-9.47 V.Heat capacity measurements reveal strong electronic correlations within this material,which is further supported by angle-resolved photoemission spectroscopy and first-principles calculations,underscoring the effect of topological flat bands and Van Hove singularity.Our research introduces a promising self-assembled material platform,adeptly positioned to delve into the quest for topological superconductors.展开更多
The design of a novel photonic crystal waveguide power splitter is presented.The proposed power splitter has three output ports,the coupling among three parallel photonic crystal waveguides can be considered as a mult...The design of a novel photonic crystal waveguide power splitter is presented.The proposed power splitter has three output ports,the coupling among three parallel photonic crystal waveguides can be considered as a multimode interference(MMI),and the positions of output waveguides are determined by those of twofold images which are formed by the self-imaging effect of multimode interference.The transmission characteristics of the splitter are investigated by using the finite-difference time domain(FDTD) and the plane wave expansion method.The output optical power in each port can be controlled by adjusting the radius of the dielectric rods in the coupling region,and the coupling effect among output ports is decreased by using the T-shaped output port.The results indicate that 1 × 1,1 × 2 and 1 × 3 type power splitters can be realized when the normalized radius of dielectric rods in the coupling region is 0.130,0.180,0.152 or 0.221,respectively.展开更多
We numerically investigate the population dynamics in a single photon resonant three-level cascade and non-cascade energy level molecules at 532-nm wavelength. The time-dependent population in the energy levels in the...We numerically investigate the population dynamics in a single photon resonant three-level cascade and non-cascade energy level molecules at 532-nm wavelength. The time-dependent population in the energy levels in the presence of 100 ps(pico-second) and 100 ns(nano-second) laser pulses is described in the form of rate equations. We provide a brief idea of how the optical energy transfer takes place in the light-matter interaction and we also discuss the absorption as a function of pulse width and repetition rate. We also plot the z-scan transmittance curve as a function of number of excitation pulses participating in the absorption.展开更多
Two-photon photopolymerization （TPP） of femtosecond laser is a promising method to fabricate three-dimensional woodpile photonic crystals （PCs）. We build micro-fabricatlon system based on the principle of TPP. Thr...Two-photon photopolymerization （TPP） of femtosecond laser is a promising method to fabricate three-dimensional woodpile photonic crystals （PCs）. We build micro-fabricatlon system based on the principle of TPP. Three- dimensional woodpile PCs consisting of in-plane rod distances ranging from 1000nm to 2000nm are fabricated by focusing femtosecond laser in photosensitive liquid resin ORMOCER. The properties of the PCs are also discussed, and fundamental photonic band gaps in middle-infrared range are measured, whose in-plane rod distances are 1500nm and 2000 nm. Three-dimenslonal woodpile PC devices with desired defects, such as cross-waveguide and micro-laser structures, are introduced easily by TPP. We fabricate the three-dimensional woodpile PCs in the liquid resin at the fast scanning speed of 120μm/s.展开更多
We identified the antimony species present in a wide variety of plastic samples by X ray absorption spectroscopy(XAS)at the Sb L_(3)-edge.The samples contained different concentrations of antimony(Sb),ranging from PET...We identified the antimony species present in a wide variety of plastic samples by X ray absorption spectroscopy(XAS)at the Sb L_(3)-edge.The samples contained different concentrations of antimony(Sb),ranging from PET bottles in which Sb compounds are used as catalysts,with concentrations around 300 mg/kg,to electrical equipment in which the element is used as a flame retardant,with concentrations of several tens of thousands of mg/kg.Although the shape of the spectra at the L_(3)-edge is quite similar for all Sb reference materials,we were able to identify antimony glycolate or acetate in PET bottles,bound organic Sb in c-PET trays and senarmontite in electrical materials as themain Sb components.In samples with high Ca content(e.g.,electrical objects,some c-PET food trays and textiles)the Ca Ka emission line interferes with the Sb La line by introducing a high background which reduces the signal-to-noise ratio in the Sb XAS spectrum,resulting in noisy and distorted spectra.The element-resolved map on a PET bottle sample revealed both Sb and Ca hot spots of around 10-20 microns in size,with no correlation.展开更多
We present a systematic experimental investigation of temporal contrast enhancement techniques for petawatt(PW)-class Ti:sapphire lasers utilizing a double chirped-pulse amplification(CPA)architecture.Particular atten...We present a systematic experimental investigation of temporal contrast enhancement techniques for petawatt(PW)-class Ti:sapphire lasers utilizing a double chirped-pulse amplification(CPA)architecture.Particular attention is given to pre-pulses induced by post-pulses originating in the first CPA stage.One conventional and two advanced pulse-cleaning strategies are quantitatively evaluated:(i)a saturable absorber(SA),(ii)a femtosecond optical parametric amplifier(OPA)employing the idler pulse in a two-stage configuration,and(iii)sum-frequency generation(SFG)combining the signal and idler pulses from the OPA.All techniques are implemented and evaluated using the J-KAREN-P laser system with an output energy of about 20 J.To the best of our knowledge,this is the first report to directly and systematically compare the contrast of pre-pulses originating from the first CPA stage under identical experimental conditions in a high-energy PW-class laser facility.The results offer crucial insights into contrast optimization for future high-field applications.展开更多
Despite the rapid efficiency increase,tin halide perovskite solar cells are significantly behind their lead-based counterpart,with the highest reported efficiency of 15.38%.The main reason for this large difference is...Despite the rapid efficiency increase,tin halide perovskite solar cells are significantly behind their lead-based counterpart,with the highest reported efficiency of 15.38%.The main reason for this large difference is attributed to the instability of Sn^(2+),which easily oxidizes to Sn^(4+),creating Sn vacancies and increasing the open-circuit voltage loss.In this work,we implemented tin thiocyanate(Sn(SCN)_(2))as an additive for passivating the bulk defects of a germanium-doped tin halide perovskite film.Adding Sn^(2+)and SCN-ions reduces the Sn and iodine vacancies,limiting non-radiative recombination and favoring longer charge-carrier dynamics.Moreover,the addition of Sn(SCN)_(2) induces a higher film crystallinity and preferential orientation of the(l00)planes parallel to the substrate.The passivated devices showed improved photovoltaic parameters with the best open-circuit voltage of 0.716 V and the best efficiency of 12.22%,compared to 0.647 V and 10.2%for the reference device.In addition,the passivated solar cell retains 88.7%of its initial efficiency after 80 min of illumination under 100 mW cm^(-2) and is substantially better than the control device,which reaches 82.6%of its initial power conversion efficiency only after 30 min.This work demonstrates the passivation potential of tin-based additives,which combined with different counterions give a relatively large space of choices for passivation of Sn-based perovskites.展开更多
We used fast chlorophyll fluorescence transients(OJIP) to study provenance-related differences in photosynthetic performance and the magnitude of day-to-day chlorophyll fluorescence(ChlF) variation in northern(67°...We used fast chlorophyll fluorescence transients(OJIP) to study provenance-related differences in photosynthetic performance and the magnitude of day-to-day chlorophyll fluorescence(ChlF) variation in northern(67°N)and southern(62°N) silver birches in a common garden at62°N.ChlF transients were measured five times during two weeks in the middle of summer to avoid seasonal variation.Differences in growth and leaf morphological traits between the provenances were also examined.The northern trees had higher chlorophyll content,larger leaf areas,and higher leaf fresh and dry mass than the southern trees,but the leaf mass per area did not differ between the provenances.The southern trees were taller and showed higher annual shoot growth than the northern trees.For all the ChlF parameters,day-to-day variation was significant and followed the same pattern for both provenances with no significant provenance ×day interaction,suggesting a similar response to environmental variation.The northern provenance had higher values in parameters related to the reduction of end electron acceptors at the Photosystem I(PSI) acceptor side as probed by ChlF.This and higher values for performance indices PI_(abs) and PI_(tot) in northern than in southern trees suggest higher photosynthetic performance of northern trees in line with the latitudinal compensation strategy.Provenance differences in these parameters increased towards the end of the measurement period,suggesting preparation for earlier growth cessation in northern trees triggered by the shortening day length.The study shows that provenance differences in ChlF can be relatively stable regardless of environmental variation but might be influenced by physiological alterations in preparation for future changes in environmental conditions.展开更多
We present a 3+1 formulation of the light modes in nonlinear electrodynamics described by Plebanski-type Lagrangians,which include post-Maxwellian,Born-Infeld,ModMax,and Heisenberg-Euler-Schwinger QED Lagrangians.In n...We present a 3+1 formulation of the light modes in nonlinear electrodynamics described by Plebanski-type Lagrangians,which include post-Maxwellian,Born-Infeld,ModMax,and Heisenberg-Euler-Schwinger QED Lagrangians.In nonlinear electrodynamics,strong electromagnetic fields modify the vacuum such that it acquires optical properties.Such a field-modified vacuum can possess electric permittivity,magnetic permeability,and a magneto-electric response,inducing novel phenomena such as vacuum birefringence.By exploiting the mathematical structures of Plebanski-type Lagrangians,we establish a streamlined procedure and explicit formulas to determine light modes,i.e.,refractive indices and polarization vectors for a given propagation direction.We also work out the light modes of the various Lagrangians for an arbitrarily strong magnetic field.The 3+1 formulation advanced in this paper has direct applications to the current vacuum birefringence research:terrestrial experiments using permanent magnets/ultra-intense lasers for the subcritical regime and astrophysical observation of X-rays from highly magnetized neutron stars for the near-critical and supercritical regimes.展开更多
Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates h...Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.展开更多
Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison betwee...Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous research.In the present study,a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system,respectively.The quality of the micro-holes,e.g.,recast layer,micro-crack,circularity,and conicity,etc,is evaluated by employing an optical microscope,an optical interferometer,and a scanning electron microscope.Additionally,the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching treatment.The researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled micro-holes.The formation of a recast layer with a thickness of;5μm is detected on the side walls,associated with initiation of micro-cracks.Tapering phenomenon is also observed and the circularity of the micro-holes is rather poor.With regard to the micro-holes drilled by picosecond laser,the entrance ends,the exit ends,and the side walls are quite smooth without accumulation of spattering material,formation of recast layer and micro-cracks.The circularity of the micro-holes is fairly good without observation of tapering phenomenon.Furthermore,there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent material.This study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.展开更多
Multi-walled carbon nanotubes （MWCNTs） are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 t...Multi-walled carbon nanotubes （MWCNTs） are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 torr, and 500 torr. Arc plasma parameters such as temperature and density are estimated to investigate the influences of the ambient pressure and the contributions of the ambient pressure to the growth and the structure of the nanotubes. The plasma temperature and density are observed to increase with the increase in the methane ambient pressure. The samples of MWCNT synthesized at different ambient pressures are analyzed using transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. An increase in the growth of MWCNT and a decrease in the inner tube diameter are observed with the increase in the methane ambient pressure.展开更多
Twelve samples with periodic array square pillars microstructure were prepared on the silicon wafer by plasma etching techniques, on which space b of the square pillars increased from 5 to 60 μm. In order to study th...Twelve samples with periodic array square pillars microstructure were prepared on the silicon wafer by plasma etching techniques, on which space b of the square pillars increased from 5 to 60 μm. In order to study the effect ofb on the wettability of the rough surface, the effects of apparent contact angle （CA） and sliding angle （a） of the droplet on the rough surface were measured with the contact angle meter. The results show that the experimental values of CA well agree with the classical wetting theory and a decreases with the increase of b. Two drop shapes exist on the samples＇ surface, corresponding to the Cassie state and the Wenzel state respectively. The contact state in which a drop would settle depends typically on the size of b. On the role of gravitation, the irreversible transition of a drop from Cassie state to Wenzel state should occur at a certain space of the square pillars. Since the transition has implications on the application of super-hydrophobic rough surfaces, theoretically, the prediction of wetting state transition on square pillar array micro-structured surfaces provides an intuitionistic guidance for the design of steady superhydrophobic surfaces.展开更多
Organic–inorganic hybrid perovskite materials demonstrate promising applications in high-efficiency perovskite solar cells (PSCs) with a certified power conversion efficiency(PCE) of 25.5%(https://www.nrel.gov/pv/cel...Organic–inorganic hybrid perovskite materials demonstrate promising applications in high-efficiency perovskite solar cells (PSCs) with a certified power conversion efficiency(PCE) of 25.5%(https://www.nrel.gov/pv/cell-efficiency.html).展开更多
This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power...This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power besides work piece scanning speed. For approximate cutting depth, a theoretical study is conducted in terms of material property and cutting speed. Results show a nonlinear relation between the cutting depth and input energy. There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s. An extra energy is utilized in the deep cutting. It is inferred that as the laser power increases, cutting depth increases. The experimental outcomes are in good agreement with theoretical results. This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting, scribing, trimming, engraving, and marking nonmetallic materials.展开更多
Biodegradable implants are taking an increasingly important role in the area of orthopedic implants with the aim to replace permanent implants for temporary bone healing applications.During the implant preparation pro...Biodegradable implants are taking an increasingly important role in the area of orthopedic implants with the aim to replace permanent implants for temporary bone healing applications.During the implant preparation process,the material’s surface and microstructure are being changed by stresses induced by machining.Hence degradable metal implants need to be fully characterized in terms of the influence of machining on the resulting microstructure and corrosion performance.In this study,micro-computed tomography(μCT)is used for the quantification of the degradation rate of biodegradable implants.To our best knowledge,for the first time quantitative measures are introduced to describe the degradation homogeneity in 3D.This information enables a prediction in terms of implant stability during the degradation in the body.Two magnesium gadolinium alloys,Mg-5Gd and Mg-10 Gd(all alloy compositions are given in weight%unless otherwise stated),in the shape of M2 headless screws have been investigated for their microstructure and their degradation performance up to 56 days.During the microstructure investigations particular attention was paid to the localized deformation of the alloys,due to the machining process.In vitro immersion testing was performed to assess the degradation performance quantified by subsequent weight loss and volume loss(usingμCT)measurements.Although differences were observed in the degree of screw’s near surface microstructure being influenced from machining,the degradation rates of both materials appeared to be suitable for application in orthopedic implants.From the degradation homogeneity point of view no obvious contrast was detected between both alloys.However,the higher degradation depth ratios between the crests and roots of Mg-5Gd ratios may indicated a less homogeneous degradation of the screws of these alloys on contract to the ones made of Mg-10Gd alloys.Due to its lower degradation rates,its more homogeneous microstructure,its weaker texture and better degradation performance extruded Mg-10Gd emerged more suitable as implant material than Mg-5Gd.展开更多
The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the under...The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the underlying physics and regular procedure of such a measurement through the radioactivation of a stack composed of aluminum,copper,and CR-39 plates as well as radiochromic films(RCFs).After being radioactivated,the copper plates are placed on imaging plates(IPs)to detect the positrons emitted by the reaction products through contact imaging.The spectrum and energy-dependent spatial profile of the protons are then obtained from the IPs and confirmed by the measured ones from the RCFs and CR-39 plates.We also discuss the detection range,influence of electrons,radiation safety,and spatial resolution of this measurement.Finally,insights regarding the extension of the current method to online measurements and dynamic proton imaging are also provided.展开更多
Solid-state cooling based on caloric effects is considered a viable alternative to replace the conventional vapor-compression refrigeration systems.Regarding barocaloric materials,recent results show that elastomers a...Solid-state cooling based on caloric effects is considered a viable alternative to replace the conventional vapor-compression refrigeration systems.Regarding barocaloric materials,recent results show that elastomers are promising candidates for cooling applications around room-temperature.In the present paper,we report supergiant barocaloric effects observed in acetoxy silicone rubber—a very popular,low-cost and environmentally friendly elastomer.Huge values of adiabatic temperature change and reversible isothermal entropy change were obtained upon moderate applied pressures and relatively low strains.These huge barocaloric changes are associated both to the polymer chain rearrangements induced by confined compression and to the first-order structural transition.The results are comparable to the best barocaloric materials reported so far,opening encouraging prospects for the application of elastomers in near future solid-state cooling devices.展开更多
Liberty State Park in New Jersey,USA,is a ＂brownfield＂ site containing various levels of contaminants.To investigate metal uptake and distributions in plants on the brownfield site,Phragmites australis and Typha lat...Liberty State Park in New Jersey,USA,is a ＂brownfield＂ site containing various levels of contaminants.To investigate metal uptake and distributions in plants on the brownfield site,Phragmites australis and Typha latifolia were collected in Liberty State Park during the growing season（May–September）in 2011 at two sites with the high and low metal loads,respectively.The objective of this study was to understand the metal（Fe,Mn,Cu,Pb and Zn）concentration and spatial distributions in P.australis and T.latifolia root systems with micro-meter scale resolution using synchrotron X-ray microfluorescence（μXRF）and synchrotron X-ray computed microtomography（μCMT）techniques.The root structure measurement by synchrotron μCMT showed that high X-ray attenuation substance appeared in the epidermis.Synchrotron μXRF measurement showed that metal concentrations and distributions in the root cross-section between epidermis and vascular tissue were statistically different.Significant correlations were found between metals（Cu,Mn,Pb and Zn）and Fe in the epidermis,implying that metals were scavenged by Fe oxides.The results from this study suggest that the expression of metal transport and accumulation within the root systems may be element specific.The information derived from this study can improve our current knowledge of the wetland plant ecological function in brownfield remediation.展开更多
Two-dimensional(2D)/quasi-2D perovskite solar cells(PSCs)incorporating organic spacer cations exhibit appealing ambient stability in comparison with their 3D analogs.Most reported organic spacer cations are based on a...Two-dimensional(2D)/quasi-2D perovskite solar cells(PSCs)incorporating organic spacer cations exhibit appealing ambient stability in comparison with their 3D analogs.Most reported organic spacer cations are based on ammonium,whereas formamidinium(FA^(+))has been seldom applied despite that FA has been extensively used in high-efficiency 3D PSCs.Herein,a novel FA-based organic spacer cation,4-chloro-phenylformamidinium(CPFA^(+)),is applied in quasi-2D Ruddlesden-Popper(RP)PSCs for the first time,and methylammonium chloride(MACl)is employed to promote crystal growth and orientation of perovskite film,resulting in high power conversion efficiency(PCE)with improved stability.Upon incorporating CPFA+organic spacer cation and MACl additive,high-quality quasi-2D CPFA_(2)MA_(n-1)Pb_(n)(I_(0.857)Cl_(0.143))_(3n+1)(n=9)perovskite film forms,exhibiting improved crystal orientation,reduced trap state density,prolonged carrier lifetime and optimized energy level alignment.Consequently,the CPFA_(2)MA_(n-1)Pb_(n)(I_(0.857)Cl_(0.143))_(3n+1)(n=9)quasi-2D RP PSC devices deliver a highest PCE of 14.78%.Moreover,the un-encapsulated CPFA-based quasi-2D RP PSC devices maintain~80%of its original PCE after exceeding 2000 h storage under ambient condition,whereas the 3D MAPb I3counterparts retain only~45%of its original PCE.Thus,the ambient stability of quasi-2D RP PSC devices is improved obviously relative to its 3D MAPb I3counterpart.展开更多
基金supported by Innovation Program for Quantum Science and Technology(No.2021ZD0302800)the National Natural Science Foundation of China(Nos.52373309 and 12004357)+2 种基金the National Key R&D Program of China(No.2023YFA1610100)the financial support from U.S.Department of Energy Office of Science-The Basic Energy Sciences program(DOE-BES)(No.DE-FG02-04ER46148)the financial support from the National Natural Science Foundation of China(No.12574210).
文摘Intrinsic topological superconductors have garnered significant attention for their potential to harbor novel quantum phenomena.However,the limited availability of suitable material systems has hindered progress in this field.Here,we present the synthesis and characterization of high-quality self-assembled SnS/TaS_(2)(SnTaS_(3))superlattice,which exhibits superconductivity alongside non-trivial band topology.Temperature-dependent magnetization susceptibility and electrical transport results confirm SnTaS_(3) as a type-Ⅱ superconductor with a critical transition temperature Tc of 3 K.Interestingly,this superconductivity can be turned off via an innovative solid proton gate technique,and a new superconducting state with a Tc of~2.3 K emerges when the gating voltage reaches-9.47 V.Heat capacity measurements reveal strong electronic correlations within this material,which is further supported by angle-resolved photoemission spectroscopy and first-principles calculations,underscoring the effect of topological flat bands and Van Hove singularity.Our research introduces a promising self-assembled material platform,adeptly positioned to delve into the quest for topological superconductors.
基金supported by the National Natural Science Foundation of China (Nos.60977048 and 50975129)Qianjiang Talent Project of Zhejiang Province (No.2007R10015)the Senior Talent Foundation of Jiangsu University (No.07JDG074)
文摘The design of a novel photonic crystal waveguide power splitter is presented.The proposed power splitter has three output ports,the coupling among three parallel photonic crystal waveguides can be considered as a multimode interference(MMI),and the positions of output waveguides are determined by those of twofold images which are formed by the self-imaging effect of multimode interference.The transmission characteristics of the splitter are investigated by using the finite-difference time domain(FDTD) and the plane wave expansion method.The output optical power in each port can be controlled by adjusting the radius of the dielectric rods in the coupling region,and the coupling effect among output ports is decreased by using the T-shaped output port.The results indicate that 1 × 1,1 × 2 and 1 × 3 type power splitters can be realized when the normalized radius of dielectric rods in the coupling region is 0.130,0.180,0.152 or 0.221,respectively.
文摘We numerically investigate the population dynamics in a single photon resonant three-level cascade and non-cascade energy level molecules at 532-nm wavelength. The time-dependent population in the energy levels in the presence of 100 ps(pico-second) and 100 ns(nano-second) laser pulses is described in the form of rate equations. We provide a brief idea of how the optical energy transfer takes place in the light-matter interaction and we also discuss the absorption as a function of pulse width and repetition rate. We also plot the z-scan transmittance curve as a function of number of excitation pulses participating in the absorption.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50435030 and 50375068, and the Programme for New Century Excellent Talents in Universities of the Ministry of Education of China.
文摘Two-photon photopolymerization （TPP） of femtosecond laser is a promising method to fabricate three-dimensional woodpile photonic crystals （PCs）. We build micro-fabricatlon system based on the principle of TPP. Three- dimensional woodpile PCs consisting of in-plane rod distances ranging from 1000nm to 2000nm are fabricated by focusing femtosecond laser in photosensitive liquid resin ORMOCER. The properties of the PCs are also discussed, and fundamental photonic band gaps in middle-infrared range are measured, whose in-plane rod distances are 1500nm and 2000 nm. Three-dimenslonal woodpile PC devices with desired defects, such as cross-waveguide and micro-laser structures, are introduced easily by TPP. We fabricate the three-dimensional woodpile PCs in the liquid resin at the fast scanning speed of 120μm/s.
文摘We identified the antimony species present in a wide variety of plastic samples by X ray absorption spectroscopy(XAS)at the Sb L_(3)-edge.The samples contained different concentrations of antimony(Sb),ranging from PET bottles in which Sb compounds are used as catalysts,with concentrations around 300 mg/kg,to electrical equipment in which the element is used as a flame retardant,with concentrations of several tens of thousands of mg/kg.Although the shape of the spectra at the L_(3)-edge is quite similar for all Sb reference materials,we were able to identify antimony glycolate or acetate in PET bottles,bound organic Sb in c-PET trays and senarmontite in electrical materials as themain Sb components.In samples with high Ca content(e.g.,electrical objects,some c-PET food trays and textiles)the Ca Ka emission line interferes with the Sb La line by introducing a high background which reduces the signal-to-noise ratio in the Sb XAS spectrum,resulting in noisy and distorted spectra.The element-resolved map on a PET bottle sample revealed both Sb and Ca hot spots of around 10-20 microns in size,with no correlation.
基金supported by the Japan Society for the Promotion of Science(Grant Nos.JP 15F15772,JP 16H03911,JP 16K05506,JP 19H00669,and JP 25H00621)the Precursory Research for Embryonic Science and Technology(Grant No.JPMJPR16P9)+1 种基金the MEXT Project(Grant No.JPMXS0450300221)the Japan Science and Technology Agency(Grant No.PRESTOJPMJPR16P9).
文摘We present a systematic experimental investigation of temporal contrast enhancement techniques for petawatt(PW)-class Ti:sapphire lasers utilizing a double chirped-pulse amplification(CPA)architecture.Particular attention is given to pre-pulses induced by post-pulses originating in the first CPA stage.One conventional and two advanced pulse-cleaning strategies are quantitatively evaluated:(i)a saturable absorber(SA),(ii)a femtosecond optical parametric amplifier(OPA)employing the idler pulse in a two-stage configuration,and(iii)sum-frequency generation(SFG)combining the signal and idler pulses from the OPA.All techniques are implemented and evaluated using the J-KAREN-P laser system with an output energy of about 20 J.To the best of our knowledge,this is the first report to directly and systematically compare the contrast of pre-pulses originating from the first CPA stage under identical experimental conditions in a high-energy PW-class laser facility.The results offer crucial insights into contrast optimization for future high-field applications.
基金support from the Focus Group‘Next Generation Organic Photovoltaics’participating with the Dutch Institute for Fundamental Energy Research(DIFFER)(FOM130)Advanced Materials research program of the Zernike National Research Centre under the Bonus Incentive Scheme(BIS)of the Dutch Ministry for Education,Culture and Science.
文摘Despite the rapid efficiency increase,tin halide perovskite solar cells are significantly behind their lead-based counterpart,with the highest reported efficiency of 15.38%.The main reason for this large difference is attributed to the instability of Sn^(2+),which easily oxidizes to Sn^(4+),creating Sn vacancies and increasing the open-circuit voltage loss.In this work,we implemented tin thiocyanate(Sn(SCN)_(2))as an additive for passivating the bulk defects of a germanium-doped tin halide perovskite film.Adding Sn^(2+)and SCN-ions reduces the Sn and iodine vacancies,limiting non-radiative recombination and favoring longer charge-carrier dynamics.Moreover,the addition of Sn(SCN)_(2) induces a higher film crystallinity and preferential orientation of the(l00)planes parallel to the substrate.The passivated devices showed improved photovoltaic parameters with the best open-circuit voltage of 0.716 V and the best efficiency of 12.22%,compared to 0.647 V and 10.2%for the reference device.In addition,the passivated solar cell retains 88.7%of its initial efficiency after 80 min of illumination under 100 mW cm^(-2) and is substantially better than the control device,which reaches 82.6%of its initial power conversion efficiency only after 30 min.This work demonstrates the passivation potential of tin-based additives,which combined with different counterions give a relatively large space of choices for passivation of Sn-based perovskites.
基金supported by the University of Eastern FinlandCzech University of Life Sciences doctoral research funding to O.A+5 种基金North Karelia Regional Fund to O.A (grant number 55232028)University of Eastern Finland(strategic fundingproject 931060)the Academy of Finland(C-NEUT,project number 347862)part of the Academy of Finland Flagship on Photonics Research and Innovation (PREIN) decision (320166)the Finnish National Plant Phenotyping Infrastructure (NaPPI/Biocenter Finland)
文摘We used fast chlorophyll fluorescence transients(OJIP) to study provenance-related differences in photosynthetic performance and the magnitude of day-to-day chlorophyll fluorescence(ChlF) variation in northern(67°N)and southern(62°N) silver birches in a common garden at62°N.ChlF transients were measured five times during two weeks in the middle of summer to avoid seasonal variation.Differences in growth and leaf morphological traits between the provenances were also examined.The northern trees had higher chlorophyll content,larger leaf areas,and higher leaf fresh and dry mass than the southern trees,but the leaf mass per area did not differ between the provenances.The southern trees were taller and showed higher annual shoot growth than the northern trees.For all the ChlF parameters,day-to-day variation was significant and followed the same pattern for both provenances with no significant provenance ×day interaction,suggesting a similar response to environmental variation.The northern provenance had higher values in parameters related to the reduction of end electron acceptors at the Photosystem I(PSI) acceptor side as probed by ChlF.This and higher values for performance indices PI_(abs) and PI_(tot) in northern than in southern trees suggest higher photosynthetic performance of northern trees in line with the latitudinal compensation strategy.Provenance differences in these parameters increased towards the end of the measurement period,suggesting preparation for earlier growth cessation in northern trees triggered by the shortening day length.The study shows that provenance differences in ChlF can be relatively stable regardless of environmental variation but might be influenced by physiological alterations in preparation for future changes in environmental conditions.
基金supported by the Ultrashort Quantum Beam Facility operation program(Grant No.140011)through APRI,GISTalso by the Institute of Basic Science(Grant No.IBSR038-D1).
文摘We present a 3+1 formulation of the light modes in nonlinear electrodynamics described by Plebanski-type Lagrangians,which include post-Maxwellian,Born-Infeld,ModMax,and Heisenberg-Euler-Schwinger QED Lagrangians.In nonlinear electrodynamics,strong electromagnetic fields modify the vacuum such that it acquires optical properties.Such a field-modified vacuum can possess electric permittivity,magnetic permeability,and a magneto-electric response,inducing novel phenomena such as vacuum birefringence.By exploiting the mathematical structures of Plebanski-type Lagrangians,we establish a streamlined procedure and explicit formulas to determine light modes,i.e.,refractive indices and polarization vectors for a given propagation direction.We also work out the light modes of the various Lagrangians for an arbitrarily strong magnetic field.The 3+1 formulation advanced in this paper has direct applications to the current vacuum birefringence research:terrestrial experiments using permanent magnets/ultra-intense lasers for the subcritical regime and astrophysical observation of X-rays from highly magnetized neutron stars for the near-critical and supercritical regimes.
基金supported by the National Natural Science Foundation of China(No.21927814)the National Key Research and Development Program of China(Nos.2019YFA0405600,2019YFA0706900,2021YFA1200104,2022YFC3400500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB0540200,XDB37040201)Plans for Major Provincial Science&Technology Projects(No.202303a07020004)the Youth Innovation Promotion Association,CAS(No.2022455)。
文摘Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.
基金Supported by National Basic Research Program of China(Grant No.2011CB013004)National Natural Science Foundation of China(Grant No.51005130)Research Fund of State Key Laboratory of Tribology,Tsinghua University(Grant no.SKLT12B06)
文摘Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous research.In the present study,a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system,respectively.The quality of the micro-holes,e.g.,recast layer,micro-crack,circularity,and conicity,etc,is evaluated by employing an optical microscope,an optical interferometer,and a scanning electron microscope.Additionally,the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching treatment.The researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled micro-holes.The formation of a recast layer with a thickness of;5μm is detected on the side walls,associated with initiation of micro-cracks.Tapering phenomenon is also observed and the circularity of the micro-holes is rather poor.With regard to the micro-holes drilled by picosecond laser,the entrance ends,the exit ends,and the side walls are quite smooth without accumulation of spattering material,formation of recast layer and micro-cracks.The circularity of the micro-holes is fairly good without observation of tapering phenomenon.Furthermore,there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent material.This study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.
文摘Multi-walled carbon nanotubes （MWCNTs） are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 torr, and 500 torr. Arc plasma parameters such as temperature and density are estimated to investigate the influences of the ambient pressure and the contributions of the ambient pressure to the growth and the structure of the nanotubes. The plasma temperature and density are observed to increase with the increase in the methane ambient pressure. The samples of MWCNT synthesized at different ambient pressures are analyzed using transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. An increase in the growth of MWCNT and a decrease in the inner tube diameter are observed with the increase in the methane ambient pressure.
基金Project(50435030) supported by the National Natural Science foundation of ChinaProject supported by the Program for New Century Excellent Talents in Chinese University Project(GZ080010) supported by the Open Research Fund Program of Jiangsu Province Key Laboratory for Photon Manufacturing Science and Technology
文摘Twelve samples with periodic array square pillars microstructure were prepared on the silicon wafer by plasma etching techniques, on which space b of the square pillars increased from 5 to 60 μm. In order to study the effect ofb on the wettability of the rough surface, the effects of apparent contact angle （CA） and sliding angle （a） of the droplet on the rough surface were measured with the contact angle meter. The results show that the experimental values of CA well agree with the classical wetting theory and a decreases with the increase of b. Two drop shapes exist on the samples＇ surface, corresponding to the Cassie state and the Wenzel state respectively. The contact state in which a drop would settle depends typically on the size of b. On the role of gravitation, the irreversible transition of a drop from Cassie state to Wenzel state should occur at a certain space of the square pillars. Since the transition has implications on the application of super-hydrophobic rough surfaces, theoretically, the prediction of wetting state transition on square pillar array micro-structured surfaces provides an intuitionistic guidance for the design of steady superhydrophobic surfaces.
基金supported by the National Key Research and Development Program of China (2017YFA0402800)National Natural Science Foundation of China (51925206,U1932214)+2 种基金Collaborative Innovation Program of Hefei Science Center (2020HSC-CIP004)the National Key Research and Development Program of China(2017YFA0206600)the National Natural Science Foundation of China (51773045, 21772030, 51922032, 21961160720)for financial support。
文摘Organic–inorganic hybrid perovskite materials demonstrate promising applications in high-efficiency perovskite solar cells (PSCs) with a certified power conversion efficiency(PCE) of 25.5%(https://www.nrel.gov/pv/cell-efficiency.html).
基金supported by the Science Foundation of the Ministry of Science and Technology Malaysiathe Islamic Development Bank Jeddahsupport of the Universiti Teknologi Malaysia for this research work
文摘This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power besides work piece scanning speed. For approximate cutting depth, a theoretical study is conducted in terms of material property and cutting speed. Results show a nonlinear relation between the cutting depth and input energy. There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s. An extra energy is utilized in the deep cutting. It is inferred that as the laser power increases, cutting depth increases. The experimental outcomes are in good agreement with theoretical results. This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting, scribing, trimming, engraving, and marking nonmetallic materials.
基金carried out within the Synchro Load project(BMBF project number 05K16CGA)which is funded by the Röntgen-Angström Cluster(RAC),a bilateral research collaboration of the Swedish government and the German Federal Ministry of Education and Research(BMBF)the project Mg Bone(BMBF project number 05K16CGB)
文摘Biodegradable implants are taking an increasingly important role in the area of orthopedic implants with the aim to replace permanent implants for temporary bone healing applications.During the implant preparation process,the material’s surface and microstructure are being changed by stresses induced by machining.Hence degradable metal implants need to be fully characterized in terms of the influence of machining on the resulting microstructure and corrosion performance.In this study,micro-computed tomography(μCT)is used for the quantification of the degradation rate of biodegradable implants.To our best knowledge,for the first time quantitative measures are introduced to describe the degradation homogeneity in 3D.This information enables a prediction in terms of implant stability during the degradation in the body.Two magnesium gadolinium alloys,Mg-5Gd and Mg-10 Gd(all alloy compositions are given in weight%unless otherwise stated),in the shape of M2 headless screws have been investigated for their microstructure and their degradation performance up to 56 days.During the microstructure investigations particular attention was paid to the localized deformation of the alloys,due to the machining process.In vitro immersion testing was performed to assess the degradation performance quantified by subsequent weight loss and volume loss(usingμCT)measurements.Although differences were observed in the degree of screw’s near surface microstructure being influenced from machining,the degradation rates of both materials appeared to be suitable for application in orthopedic implants.From the degradation homogeneity point of view no obvious contrast was detected between both alloys.However,the higher degradation depth ratios between the crests and roots of Mg-5Gd ratios may indicated a less homogeneous degradation of the screws of these alloys on contract to the ones made of Mg-10Gd alloys.Due to its lower degradation rates,its more homogeneous microstructure,its weaker texture and better degradation performance extruded Mg-10Gd emerged more suitable as implant material than Mg-5Gd.
基金supported by the Institute for Basic ScienceKorea under the project code IBS-R012-D1by the Ultrashort Quantum Beam Facility(UQBF)operation program(No.140011)through APRI,GIST。
文摘The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the underlying physics and regular procedure of such a measurement through the radioactivation of a stack composed of aluminum,copper,and CR-39 plates as well as radiochromic films(RCFs).After being radioactivated,the copper plates are placed on imaging plates(IPs)to detect the positrons emitted by the reaction products through contact imaging.The spectrum and energy-dependent spatial profile of the protons are then obtained from the IPs and confirmed by the measured ones from the RCFs and CR-39 plates.We also discuss the detection range,influence of electrons,radiation safety,and spatial resolution of this measurement.Finally,insights regarding the extension of the current method to online measurements and dynamic proton imaging are also provided.
文摘Solid-state cooling based on caloric effects is considered a viable alternative to replace the conventional vapor-compression refrigeration systems.Regarding barocaloric materials,recent results show that elastomers are promising candidates for cooling applications around room-temperature.In the present paper,we report supergiant barocaloric effects observed in acetoxy silicone rubber—a very popular,low-cost and environmentally friendly elastomer.Huge values of adiabatic temperature change and reversible isothermal entropy change were obtained upon moderate applied pressures and relatively low strains.These huge barocaloric changes are associated both to the polymer chain rearrangements induced by confined compression and to the first-order structural transition.The results are comparable to the best barocaloric materials reported so far,opening encouraging prospects for the application of elastomers in near future solid-state cooling devices.
基金supported in part by the Margaret and Herman Sokol Foundation(HF)China Scholarship Council(YQ)+6 种基金the State Key Laboratory of Estuarine and Coastal Research Open Research Fund(Ref #:SKLEC-KF201304)(HF,WZ,LY,YQ)supported in part by the U.S.Department of Energy,Office of Science,Office of Workforce Development for Teachers and Scientists(WDTS)under the Visiting Faculty Program(VFP)(HF)Portions of this work were performed at Beamline X27A,National Synchrotron Light Source(NSLS),and Biosciences Department,Brookhaven National LaboratoryWork in Bioscience Department,BNL,was partially supported by the Division of Chemical Sciences,Geosciences,and Biosciences,Office of Basic Energy Sciences of the US Department of Energy through Grant DEAC0298CH10886the National Science Foundation through grant MCB-1051675(CJL)X27A is supported in part by the U.S.Department of Energy--Geosciences(DE-FG02-92ER14244 to The University of Chicago-CARS)Use of the NSLS was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-98CH10886
文摘Liberty State Park in New Jersey,USA,is a ＂brownfield＂ site containing various levels of contaminants.To investigate metal uptake and distributions in plants on the brownfield site,Phragmites australis and Typha latifolia were collected in Liberty State Park during the growing season（May–September）in 2011 at two sites with the high and low metal loads,respectively.The objective of this study was to understand the metal（Fe,Mn,Cu,Pb and Zn）concentration and spatial distributions in P.australis and T.latifolia root systems with micro-meter scale resolution using synchrotron X-ray microfluorescence（μXRF）and synchrotron X-ray computed microtomography（μCMT）techniques.The root structure measurement by synchrotron μCMT showed that high X-ray attenuation substance appeared in the epidermis.Synchrotron μXRF measurement showed that metal concentrations and distributions in the root cross-section between epidermis and vascular tissue were statistically different.Significant correlations were found between metals（Cu,Mn,Pb and Zn）and Fe in the epidermis,implying that metals were scavenged by Fe oxides.The results from this study suggest that the expression of metal transport and accumulation within the root systems may be element specific.The information derived from this study can improve our current knowledge of the wetland plant ecological function in brownfield remediation.
基金supported by the National Key Research and Development Program of China(2017YFA0402800)the National Natural Science Foundation of China(51925206,U1932214)。
文摘Two-dimensional(2D)/quasi-2D perovskite solar cells(PSCs)incorporating organic spacer cations exhibit appealing ambient stability in comparison with their 3D analogs.Most reported organic spacer cations are based on ammonium,whereas formamidinium(FA^(+))has been seldom applied despite that FA has been extensively used in high-efficiency 3D PSCs.Herein,a novel FA-based organic spacer cation,4-chloro-phenylformamidinium(CPFA^(+)),is applied in quasi-2D Ruddlesden-Popper(RP)PSCs for the first time,and methylammonium chloride(MACl)is employed to promote crystal growth and orientation of perovskite film,resulting in high power conversion efficiency(PCE)with improved stability.Upon incorporating CPFA+organic spacer cation and MACl additive,high-quality quasi-2D CPFA_(2)MA_(n-1)Pb_(n)(I_(0.857)Cl_(0.143))_(3n+1)(n=9)perovskite film forms,exhibiting improved crystal orientation,reduced trap state density,prolonged carrier lifetime and optimized energy level alignment.Consequently,the CPFA_(2)MA_(n-1)Pb_(n)(I_(0.857)Cl_(0.143))_(3n+1)(n=9)quasi-2D RP PSC devices deliver a highest PCE of 14.78%.Moreover,the un-encapsulated CPFA-based quasi-2D RP PSC devices maintain~80%of its original PCE after exceeding 2000 h storage under ambient condition,whereas the 3D MAPb I3counterparts retain only~45%of its original PCE.Thus,the ambient stability of quasi-2D RP PSC devices is improved obviously relative to its 3D MAPb I3counterpart.
