电催化CO_(2)还原耦合HCHO氧化反应系统促进污染物同步经济高效资源化转化

传统电化学CO_(2)还原(CO_(2)RR)系统中阳极发生的水氧化半反应(WOR)具有动力学缓慢、过电位大、能耗高等缺点,限制了CO_(2)RR系统的经济效益和应用。因此,本研究引入MnO_(2)阳极进行甲醛氧化半反应(FOR)以代替WOR,构建了一种新型CO_(2)RR/FOR耦合系统。与传统的CO_(2)RR/WOR系统相比,在相同的施加电势下,CO_(2)RR/FOR耦合系统的CO_(2)RR电流密度和CO_(2)RR产物的生成速率通常更具有优势。此外,在CO_(2)RR/FOR耦合系统中,在合适的施加电势下,HCHO可以选择性地转化为HCOOH。具体来说,两电极CO_(2)RR/FOR耦合系统中,在3.5V的槽电压下,近90%的HCHO可以被去除,且HCHO会选择性转化为HCOOH,其转化率约为48%。更重要的是,在不同的工作电流下,FOR所需的电势比WOR所需的电势要小。在-10 mA·cm^(-2)时,CO_(2)RR/FOR耦合系统能降低约210 mV的槽电压,并且其能耗比单独的CO_(2)RR系统和FOR系统的能耗之和降低45.13%。值得注意的是,当使用商业多晶硅太阳能电池作为电源时,在CO_(2)RR/FOR耦合系统中的CO_(2)RR电流密度、CO_(2)RR产物的生成速率和HCHO到HCOOH的选择性仍然可以实现相当的改善。目前的工作将进一步推动研究开发新型的CO_(2)RR耦合系统,以经济有效地将CO_(2)和有机污染物同时转化为有价值的化学品。

Phase sensitivity with a coherent beam and twin beams via intensity difference detection

We focus on the Mach–Zehnder interferometer(MZI) with the input of a coherent beam and one of the bright entangled twin beams with an external power reference beam employed for measurement. The results show that the phase sensitivity can reach sub-Heisenberg limit and approach quantum Cramer–Rao bound by changing the squeezing parameters and the photon number of the coherent beam, under the phase-matching condition. The absence of the external power reference beam will degrade the performance of the phase sensitivity. Meanwhile, this scheme shows good robustness against the losses of the photon detectors. We present a detailed discussion about the phase sensitivities when the inputs are two coherent beams, or a coherent beam plus a single-mode squeezed vacuum beam based on the MZI. This scenario can be applied in the field of phase precision measurements and other optical sensors.

Sustainable Ammonia Synthesis from Nitrogen and Water by One-Step Plasma Catalysis

Sustainable ammonia synthesis at ambient conditions that relies on renewable sources of energy and feedstocks is globally sought to replace the Haber-Bosch process.Here,using nitrogen and water as raw materials,a nonthermal plasma catalysis approach is demonstrated as an effective powerto-chemicals conversion strategy for ammonia production.By sustaining a highly reactive environment,successful plasma-catalytic production of NH_(3) was achieved from the dissociation of N_(2) and H_(2)O under mild conditions.Plasma-induced vibrational excitation is found to decrease the N_(2) and H_(2)O dissociation barriers,with the presence of matched catalysts in the nonthermal plasma discharge reactor contributing significantly to molecular dissociation on the catalyst surface.Density functional theory calculations for the activation energy barrier for the dissociation suggest that ruthenium catalysts supported on magnesium oxide exhibit superior performance over other catalysts in NH_(3) production by lowering the activation energy for the dissociative adsorption of N_(2) down to 1.07 eV.The highest production rate,2.67 mmol gcat.^(-1) h^(-1),was obtained using ruthenium catalyst supported on magnesium oxide.This work highlights the potential of nonthermal plasma catalysis for the activation of renewable sources to serve as a new platform for sustainable ammonia production.

A novelα-ketoamide reactivity-based two-photon fluorogenic probe for visualizing peroxynitrite in Parkinson's disease models

Peroxynitrite(ONOO^(-))contributes to oxidative stress and neurodegeneration in Parkinson's disease(PD).Developing a peroxynitrite probe would enable in situ visualization of the overwhelming ONOO^(-)flux and understanding of the ONOO^(-)stress-induced neuropathology of PD.Herein,a novelα-ketoamide-based fluorogenic probe(DFlu)was designed for ONOO^(-)
monitoring in multiple PD models.The results demonstrated that DFlu exhibits a fluorescence turn-on response to ONOO^(-)with high specificity and sensitivity.The efficacy of DFlu for intracellular ONOO^(-)
imaging was demonstrated systematically.The results showed that DFlu can successfully visualize endogenous and exogenous ONOO^(-)in cells derived from chemical and biochemical routes.More importantly,the two-photon excitation ability of DFlu has been well demonstrated by monitoring exogenous/endogenous ONOO^(-)production and scavenging in live zebraflsh PD models.This work provides a reliable and promising
α-ketoamide-based optical tool for identifying variations of ONOO^(-)in PD models.

Evolution of ionization waves in a multi-pulsed plasma jet:the role of memory charges

In this paper,we discuss the properties of ionization waves(IWs)in a multi-pulsed plasma jet while using the two-dimensional computational approach.The IWs are generated by application of three short negative pulses with a repetition frequency 12.5 MHz.The simulations are performed continuously during a single run while accounting for charges accumulated inside(surface charges)and outside(space charges)the tube.The plasma forming gas mixture(He/O2=99.8%/0.2%)is injected through the discharge tube into the surrounding humid air.We show that an IW can emerge from the tube exit at a pulse rising edge(as a negative IW)and at a falling edge of the same pulse(as a positive IW).It is demonstrated that remnants of the negative and positive charges play an essential role in the discharge evolution.The first pulse travels the shortest distance as it propagates through the initially non-ionized environment.The IWs developing during the second pulse essentially enlarge the plasma plume length.At the same time,the IWs generated by the third pulse eventually decay due to the remnants of charges accumulated during the previous pulses.Accumulated memory charges can lead to the IW extinction.

Trap distribution of polymeric materials and its effect on surface flashover in vacuum

The surface trap parameter can significantly affect the development of surface flashover in vacuum,but the effective mode and mechanism are not very clear yet.The trap parameters of three polymeric materials were tested and calculated by means of isothermal surface potential decay.The flashover experiment was developed under different applied voltages.The results show a positive correlation between the withstand voltage and the deep trap,i.e.,the deeper trap energy level is,the higher flashover voltage is.The dynamics process of charge trapping and detrapping was analyzed based on the charge transport model in dielectrics with a single trap level and two discrete trap levels.The time of charge trapping was compared with that of the discharge development.The results show that the charge trapping time is longer than the flashover development time.The way to influence flashover for a trap is not to decrease the secondary electrons in single discharge development,but to change the electric field distribution on the dielectric surface by charge capture.

Review of supershort avalanche electron beam during nanosecond-pulse discharges in some gases

Supershort avalanche electron beam(SAEB)plays an important role in nanosecond-pulse discharges.This paper aims at reviewing ex-periments results on characteritics of SAEB and its spectra in different gases in nanosecond-pulse discharges.All the joint experiments were carried in the Institute of High Current Electronics of the Russian Academy of Sciences and the Institute of Electrical Engineering of the Chinese Academy of Sciences.In these experiments,the generation of a SAEB in SF 6 in an inhomogeneous electric field was studied on three generators with pulse rise times of 0.3,0.5 and~2 ns.Firstly,the comparison of SAEB parameters in SF 6 with those obtained in other gases(air,nitrogen,argon,and krypton)is introduced.Secondly,the SAEB spectra in SF 6 and air at pressures of 10 kPa(75 torr),and 0.1 MPa(750 torr)are reviewed and discussed.Finally,1.5-D theoretical simulation of the supershort pulse of the fast electron beam in a coaxial diode filled with SF 6 at atmospheric pressure is described.The simulation was carried out in the framework of hybrid model for discharge and runaway electron kinetics.The above research progress can provide better understanding of the investigation into the mechanism of nanosecond-pulse discharges.

Effect of Frequency on Degradation in BOPP Films Under Repetitively Pulsed Voltage

Operating conditions of film capacitors are complex,and the problem of film insulation failure caused by repetitively pulsed voltage is becoming ever serious.Degradation of the film under repetitively pulsed voltage cannot be accurately evaluated by the average breakdown electric field.In this paper,the effects of pulsed electric field and pulse repetition frequency on the breakdown in biaxially oriented polypropylene(BOPP)films are investigated.Three phases of BOPP degradation are proposed based on the voltage amplitude,i.e.,maintenance(M),decline(D),and near-zero(N).Evolution of the BOPP film from degradation to breakdown at different frequencies is presented.Meanwhile,transition of discharge mode and elemental composition of the film are analyzed.Experimental results show continuous heat generation under repetitive microsecond pulses is the dominant factor for degradation of BOPP film.The number of applied pulses and the repetitive stressing time decrease exponentially with increase of frequency.This research can be contributed to the safe and reliable operation of capacitors.

Comparison-embedded evidence-CNN model for fuzzy assessment of wear severity using multi-dimensional surface images

Wear topography is a significant indicator of tribological behavior for the inspection of machine health conditions.An intelligent in-suit wear assessment method for random topography is here proposed.Three-dimension(3D)topography is employed to address the uncertainties in wear evaluation.Initially,3D topography reconstruction from a worn surface is accomplished with photometric stereo vision(PSV).Then,the wear features are identified by a contrastive learning-based extraction network(WSFE-Net)including the relative and temporal prior knowledge of wear mechanisms.Furthermore,the typical wear degrees including mild,moderate,and severe are evaluated by a wear severity assessment network(WSA-Net)for the probability and its associated uncertainty based on subjective logic.By integrating the evidence information from 2D and 3D-damage surfaces with Dempster–Shafer(D–S)evidence,the uncertainty of severity assessment results is further reduced.The proposed model could constrain the uncertainty below 0.066 in the wear degree evaluation of a continuous wear experiment,which reflects the high credibility of the evaluation result.

Acceptor Engineering Produces Ultrafast Nonradiative Decay in NIR-Ⅱ Aza-BODIPY Nanoparticles for Efficient Osteosarcoma Photothermal Therapy via Concurrent Apoptosis and Pyroptosis

Small-molecule photothermal agents(PTAs)with intense second near-infrared(NIR-Ⅱ,1,000 to 1,700 nm)absorption and high photothermal conversion efficiencies(PCEs)are promising candidates for treating deep-seated tumors such as osteosarcoma.To date,the development of small-molecule NIR-Ⅱ PTAs has largely relied on fabricating donor–acceptor–donor(D–A–D/D′)structures and limited success has been achieved.Herein,through acceptor engineering,a donor–acceptor–acceptor(D–A–A′)-structured NIR-Ⅱ aza-boron-dipyrromethene(aza-BODIPY)PTA(SW8)was readily developed for the 1,064-nm laser-mediated phototheranostic treatment of osteosarcoma.Changing the donor groups to acceptor groups produced remarkable red-shifts of absorption maximums from first near-infrared(NIR-Ⅰ)regions(~808 nm)to NIR-Ⅱ ones(~1,064 nm)for aza-BODIPYs(SW1 to SW8).Furthermore,SW8 self-assembled into nanoparticles(SW8@NPs)with intense NIR-Ⅱ absorption and an ultrahigh PCE(75%,1,064 nm).This ultrahigh PCE primarily originated from an additional nonradiative decay pathway,which showed a 100-fold enhanced decay rate compared to that shown by conventional pathways such as internal conversion and vibrational relaxation.Eventually,SW8@NPs performed highly efficient 1,064-nm laser-mediated NIR-Ⅱ photothermal therapy of osteosarcoma via concurrent apoptosis and pyroptosis.This work not only illustrates a remote approach for treating deep-seated tumors with high spatiotemporal control but also provides a new strategy for building high-performance small-molecule NIR-Ⅱ PTAs.

Positive and negative streamers in air and nitrogen in a sharply inhomogeneous electric field under conditions of runaway electron generation

The development of positive and negative streamers in a point-to-plane gap filled with air and nitrogen at various pressures(50-200 kPa)and voltages(8-25 kV)was studied.A four-channel intensified charge-coupled device(ICCD)and a streak-camera were used.Electrical parameters were measured with high resolution(10 GHz).An original method of measuring a displacement current caused by a streamer was applied.As was expected,positive streamer branches in nitrogen at low voltages and/or elevated pressures while a large-diameter streamer is formed in air.However,at high voltages or negative polarity,the large-diameter streamer is formed both in nitrogen and air in the entire pressure range.It was found that runaway electrons(REs)are generated in the very first picoseconds of gas ionisation near the pointed cathode.It was assumed that REs can be generated near the pointed anode and produce bremsstrahlung radiation due to a sharply inhomogeneous distribution of electrical potential.It was found that in the final stage of negative streamer development in air and nitrogen,the gas between the streamer front and the opposite electrode is ionised almost simultaneously in the entire volume when the streamer diameter is almost equal to the interelectrode gap.

Guest Editorial: Understanding low temperature plasmas for device reliability, modulation and application to green energy strategy

Low temperature plasma stands at the forefront of green and clean energy technologies,showcasing remarkable versatility across a wide array of applications including material processing,water splitting,methane conversion,and plasma medicine.To fully harness the potential of this technology,it is imperative to deepen our understanding of the physics underlying various discharge structures.

Recent applications in dielectric barrier discharge and radio frequency plasmas‐engineered transition metal electrocatalysts for water splitting

Hydrogen generated by water electrolysis is considered as one of the most promising protocols to partly replace the roles of traditional fossil fuels.However,high‐performance electrocatalyst satisfied with the industrial requirement still faces significant challenges.Low‐temperature plasma contains numerous high‐energy ions,electrons and other reactive species,which can provide a highly reactive environment for tuning the physio‐chemical structures of catalysts through plasma milling,etching,doping and/or deposi-tion.It is well‐known that high‐temperature micro‐filaments contained in plasmas can cause some special modifications of the catalyst surface,thus effectively adjusting the physio‐chemical structure of latterly engineered compounds.Therefore,low‐temperature plasma technologies,especially the dielectric barrier discharge(DBD)and radio frequency(RF)plasmas,can be considered as a green and sustainable strategy for engineering high‐performance electrocatalysts for water splitting(hydrogen evolution reaction[HER];oxygen evolution reaction[OER]).Herein,recent progress of DBD and RF plasmas for fabricating and modifying transition metal‐based electrocatalysts(e.g.sulphide,phos-phide,selenide,oxide,hydroxide)for hydrogen evolution reaction or OER is compre-hensively reviewed,and the role of plasma is also discussed.

On the chronological understanding of the homogeneous dielectric barrier discharge

Dielectric barrier discharges(DBD)are widely utilised non‐equilibrium atmospheric pressure plasmas with a diverse range of applications,such as material processing,surface treatment,light sources,pollution control,and medicine.Over the course of several decades,extensive research has been dedicated to the generation of homogeneous DBD(H‐DBD),focussing on understanding the transition from H‐DBD to filamentary DBD and exploring strategies to create and sustain H‐DBD.This paper first discusses the in-fluence of various parameters on DBD,including gas flow,dielectric material,surface conductivity,and mesh electrode.Secondly,a chronological literature review is presented,highlighting the development of H‐DBD and the associated understanding of its un-derlying mechanisms.This encompasses the generation of H‐DBD in helium,nitrogen,and air.Lastly,the paper provides a brief overview of multiple‐current‐pulse(MCP)behaviours in H‐DBD.The objective of this article is to provide a chronological un-derstanding of homogeneous dielectric barrier discharge(DBD).This understanding will aid in the design of new experiments aimed at better comprehending the mechanisms behind H‐DBD generation and ultimately assist in achieving large‐volume H‐DBD in an air environment.

A review on plasma-based CO_(2) utilization:process considerations in the development of sustainable chemical production

Plasma-based processes,particularly in carbon capture and utilization,hold great potential for addressing environmental challenges and advancing a circular carbon economy.While significant progress has been made in understanding plasma-induced reactions,plasma-catalyst interactions,and reactor development to enhance energy efficiency and conversion,there remains a notable gap in research concerning overall process development.This review emphasizes the critical need for considerations at the process level,including integration and intensification,to facilitate the industrialization of plasma technology for chemical production.Discussions centered on the development of plasma-based processes are made with a primary focus on CO_(2) conversion,offering insights to guide future work for the transition of the technology from laboratory scale to industrial applications.Identification of current research gaps,especially in upscaling and integrating plasma reactors with other process units,is the key to addressing critical issues.The review further delves into relevant research in process evaluation and assessment,providing methodological insights and highlighting key factors for comprehensive economic and sustainability analyses.Additionally,recent advancements in novel plasma systems are reviewed,presenting unique advantages and innovative concepts that could reshape the future of process development.This review provides essential information for navigating the path forward,ensuring a comprehensive understanding of challenges and opportunities in the development of plasma-based CCU process.

Nonlinear change of ion-induced secondary electron emission in theκ-Al_(2)O_(3) surface charging from first-principle modelling

Secondary electron emission(SEE)induced by the positive ion is an essential physical process to influence the dynamics of gas discharge which relies on the specific surface material.Surface charging has a significant impact on the material properties,thereby affecting the SEE in the plasma-surface interactions.However,it does not attract enough attention in the previous studies.In this paper,SEE dependent on the charged surface of specific materials is described with the computational method combining a density functional theory(DFT)model from the first-principle theory and the theory of Auger neutralization.The effect ofκ-Al2O3 surface charge,as an example,on the ion-induced secondary electron emission coefficient(SEEC)is investigated by analyzing the defect energy level and band structure on the charged surface.Simulation results indicate that,with the surface charge from negative to positive,the SEEC of a part of low ionization energy ions(such as Ei=12.6 eV)increases first and then decreases,exhibiting a nonlinear changing trend.This is quite different from the monotonic decreasing tendency observed in the previous model which simplifies the electronic structure.This irregular increase of the SEEC can be attributed to the lower escaped probability of orbital energy.The results further illustrate that the excessive charge could cause the bottom of the conduction band close to the valence band,thus leading to the decrease of the orbital energy occupied by the excited electrons.The nonlinear change of SEEC demonstrates a more realistic situation of how the electronic structure of material surface influences the SEE process.This work provides an accurate method of calculating SEEC from specific materials,which is urgent in widespread physical scenarios sensitive to surface materials,such as increasingly growing practical applications concerning plasma-surface interactions.

草产品加工及利用的生物学基础及研究进展

优质饲草是现代草食畜牧业健康、高质量发展的重要基础保障,也是维持优质、安全畜产品持续稳定生产的重要前提。草产品的精细加工、稳定贮存和高效利用是“饲草”向“畜产品”转化的关键步骤。通过系统解析饲草本底的生物学特性,贮存过程中微生物的组成、演替与代谢规律,功能微生物组调控牧草营养转化路径与利用机制,以及“微生物—发酵饲草料—草食家畜—畜产品”全生物链提质增效与安全调控机理,对于提升草产品品质与安全性、提高饲草利用率与转化率,推动我国饲草产业和草食畜牧业高质量发展,实现草食畜牧业提质增效等方面具有重要意义。

Atmospheric-pressure pulsed discharges and plasmas:mechanism,characteristics and applications

Pulsed discharge plasma and its application is one of the promising directions in civilian areas of pulsed power technology.In order to promote the research and development of the theory and application technology for pulsed discharge plasma,in this paper,recent progress on the mechanism of nanosecond-pulse gas discharge and the characteristics and applications of typical pulsed plasma at the Institute of Electrical Engineering,Chinese Academy of Sciences is reviewed.Firstly,progress on mechanism of nanosecond-pulse discharge based on runaway electrons and measurement technology of runaway electrons is introduced.Then,the characteristics of three typical discharges,including direct-driven pulsed discharge,pulsed dielectric barrier discharge and pulsed plasma jet,are reviewed.Furthermore,typical plasma applications of pulsed plasma on surface modification and methane conversion are presented.

Dry reforming of methane by microsecond pulsed dielectric barrier discharge plasma:Optimizing the reactor structures

Dry reforming of CH4 process can convert greenhouse gases into high-value-added fuels and chemicals with its broad application prospects in environmental protection and renewable energy.Non-thermal plasma is considered an effective alternative method because it can activate CH4 and CO_(2)under low temperature and atmospheric pressure.This paper is aimed to optimize the plasma-assisted dry reforming of CH4 process in a unipolar microsecond pulsed coaxial dielectric barrier discharge by inves-tigating the effects of reactor structures.The results show that the conversions of re-actants and the yields of syngas were significantly affected by the reactor structures.Specifically,a multi-stage or foil external electrode and negative polar discharge could promote CH4 and CO_(2)conversions,gas product yields,and energy conversion efficiencies.For different electrodes,the maximal conversions of CH4 and CO_(2)were 20.4%and 14.1%,with an energy conversion efficiency of 4.4%under our experimental conditions.Higher conversions,yields,and energy conversion efficiencies were obtained with lower power input when applying heat insulation measures.CH4 conversion was promoted to 27.9%with a moderate energy conversion efficiency of 3.8%,but the conversion of CO_(2)was only 12%when packing materials into the reactor.The results can provide specific guidance for designing plasma or plasma-catalytic dry reforming reactor.

Ionization waves in nanosecond pulsed atmospheric pressure plasma jets in argon

Typical ionization waves(IWs)are observed during the propagation of nanosecond pulsed atmospheric pressure plasma jets(APPJs)with argon flow,combining both the measurement of the axial electric field(Ez)and the temporal resolved optical imaging.The movement of the luminous APPJ head is recognized as the development of the IW front,accompanied with the propagation of the peak electric field.Especially,the radial distribution of Ez transits from a central peak profile before the IW front arrives to a hollow profile after the pass of the IW front.As for the temporal Ez trend,there is a mode transition from the single-peak feature under a low peak voltage to the double-peak feature under a higher peak voltage,indicating the existence of both primary and secondary IWs.The effect of target conditions on the IWs in APPJs is also explored.With a metal target,no residual electric field is observed before imposing the high-voltage pulses.However,with a dielectric target,the residual surface charges generate a back-ground electric field in the opposite direction to that during IW propagation.In the free APPJ(with no target),on the voltage falling edge,a negative electric field drives the electron flow to compensate the positive ions left over during the forward IW propa-gation on the voltage rising edge.