Effect of sharp vacuum-plasma boundary on the electron injection and acceleration in a few-cycle laser driven wakefield

The electron injection and acceleration driven by a few-cycle laser with a sharp vacuum-plasma boundary have been investigated through three-dimensional(3D)particle-in-cell simulations.It is found that an isotropic boundary impact injection(BII)first occurs at the vacuum-plasma boundary,and then carrier-envelope-phase(CEP)shift causes the transverse oscillation of the plasma bubble,resulting in a periodic electron self-injection(SI)in the laser polarization direction.It shows that the electron charge of the BII only accounts for a small part of the total charge,and the CEP can effectively tune the quality of the injected electron beam.The dependences of laser intensity and electron density on the total charge and the ratio of BII charge to the total charge are studied.The results are beneficial to electron acceleration and its applications,such as betatron radiation source.

Radiation effects of electrons on multilayer FePS3studied with laser plasma accelerator

Space radiation with inherently broadband spectral flux poses a huge danger to astronauts and electronics on aircraft,but it is hard to simulate such feature with conventional radiation sources. Using a tabletop laser-plasma accelerator, we can reproduce exponential energy particle beams as similar as possible to these in space radiation. We used such an electron beam to study the electron radiation effects on the surface structure and performance of two-dimensional material(Fe PS3).Energetic electron beam led to bulk sample cleavage and damage between areas of uneven thickness. For the Fe PS3sheet sample, electron radiation transformed it from crystalline state to amorphous state, causing the sample surface to rough.The full widths at the half maximum of characteristic Raman peaks became larger, and the intensities of characteristic Raman peaks became weak or even disappeared dramatically under electron radiation. This trend became more obvious for thinner samples, and this phenomenon was attributed to the cleavage of P–P and P–S bonds, destabilizing the bipyramid structure of [P2S6]4-unit. The results are of great significance for testing the maximum allowable radiation dose for the two-dimensional material, implying that Fe PS3cannot withstand such energetic electron radiation without an essential shield.

Simulations on the multi-shell target ignition driven by radiation pulse in Z-pinch dynamic hohlraum

We present the first simulation results of a multi-shell target ignition driven by Z-pinch dynamic hohlraum radiation pulse.The radiation pulse is produced with a special Z-pinch dynamic hohlraum configuration,where the hohlraum is composed of a single metal liner,a low-Z plastic foam,and a high-Z metallic foam.The implosion dynamics of a hohlraum and a multi-shell target are investigated separately by the one-dimensional code MULTI-IFE.When the peak drive current is 50 MA,simulations suggest that an x-ray pulse with nearly constant radiation temperature(-310 eV)and a duration about 9 ns can be obtained.A small multi-shell target with a radius of 1.35 mm driven by this radiation pulse is able to achieve volumetric ignition with an energy gain(G)about 6.19,where G is the ratio of the yield to the absorbed radiation.Through this research,we better understand the effects of non-uniformities and hydrodynamics instabilities in Z-pinch dynamic hohlraum.

Optimization of the beam quality in ionization injection by a tailoring gas profile

A new scheme is proposed to improve the electron beam quality of ionization-induced injection by tailoring gas profile in laser wakefield acceleration.Two-dimensional particle-in-cell simulations show that the ionization-induced injection mainly occurs in high-density stage and automatically truncates in low-density stage due to the decrease of the wakefield potential difference.The beam loading can be compensated by the elongated beam resulting from the density transition stage.The beam quality can be improved by shorter injection distance and beam loading effect.A quasi-monoenergetic electron beam with a central energy of 258 MeV and an energy spread of 5.1%is obtained under certain laser-plasma conditions.

MOF-derived Cu embedded into N-doped mesoporous carbon as a robust support of PdAu nanocatalysts for ethanol electrooxidation

Metal-organic frameworks(MOFs)h ave attracted widespread attention due to their large surface area and porous structure.Rationally designing the nanostructures of MOFs to promote their application in ethanol electrooxidation is still a challenge.Here,a novel Cu-NCNs(Cu-nitrogen-doped carbon nanotubes)support was synthesized by pyrolysis of melamine(MEL)and Cu-ZIF-8 together,and then,Pd-Au nanoalloys were loaded by sodium borohydride reduction method to prepare PdAu@Cu-NCNs catalysts.The generating mesoporous carbon with high specific surface area and favorable electron and mass transport can be used as a potential excellent carrier for PdAu nanoparticles.In addition,the balance of catalyst composition and surface structure was tuned by controlling the content of Pd and Au.Thus,the best-performed Pd_(2)Au_(2)@Cu-NCN-1000-2(where 1000 means the carrier calcination temperature,and 2 means the calcination constant temperature time)catalyst exhibits better long-term stability and electrochemical activity for ethanol oxidation in alkaline media(4.80 A·mg^(-1)),which is 5.05 times higher than that of commercial Pd/C(0.95 A·mg^(-1)).Therefore,this work is beneficial to further promoting the application of MOFs in direct ethanol fuel cells(DEFCs)and can be used as inspiration for the design of more efficient catalyst support structures.

The importance of Righi-Leduc heat flux to the ablative Rayleigh-Taylor instability during a laser irradiating targets

The Righi±Leduc heat flux generated by the self-generated magnetic field in the ablative Rayleigh±Taylor instability driven by a laser irradiating thin targets is studied through two-dimensional extended-magnetohydrodynamic simulations.The perturbation structure gets into a low magnetization state though the peak strength of the self-generated magnetic field could reach hundreds of teslas.The Righi±Leduc effect plays an essential impact both in the linear and nonlinear stages,and it deflects the total heat flux towards the spike base.Compared to the case without the self-generated magnetic field included,less heat flux is concentrated at the spike tip,finally mitigating the ablative stabilization and leading to an increase in the velocity of the spike tip.It is shown that the linear growth rate is increased by about 10%and the amplitude during the nonlinear stage is increased by even more than 10%due to the feedback of the magnetic field,respectively.Our results reveal the importance of Righi±Leduc heat flux to the growth of the instability and promote deep understanding of the instability evolution together with the self-generated magnetic field,especially during the acceleration stage in inertial confinement fusion.

RASAL2 Deficiency Attenuates Hepatic Steatosis by Promoting Hepatic VLDL Secretion via the AKT/TET1/MTTP Axis

Background and Aims:RAS protein activator like 2(RASAL2)is a newly discovered metabolic regulator involved in energy homeostasis and adipogenesis.However,whether RASAL2 is involved in hepatic lipid metabolism remains undetermined.This study explored the function of RASAL2 and elucidated its potential mechanisms in nonalcoholic fatty liver disease(NAFLD).Methods:NAFLD models were established either by feeding mice a high-fat diet or by incubation of hepatocytes with 1 mM free fatty acids(oleic acid:palmitic acid=2:1).Pathological changes were observed by hematoxylin and eosin staining.Lipid accumulation was assessed by Oil Red O staining,BODIPY493/503 staining,and triglyceride quantification.The in vivo secretion rate of very lowdensity lipoprotein was determined by intravenous injection of tyloxapol.Gene regulation was analyzed by chromatin immunoprecipitation assays and hydroxymethylated DNA immunoprecipitation combined with real-time polymerase chain reaction.Results:RASAL2 deficiency ameliorated hepatic steatosis both in vivo and in vitro.Mechanistically,RASAL2 deficiency upregulated hepatic TET1 expression by activating the AKT signaling pathway and thereby promoted MTTP expression by DNA hydroxymethylation,leading to increased production and secretion of very low-density lipoprotein,which is the major carrier of triglycerides exported from the liver to distal tissues.Conclusions:Our study reports the first evidence that RASAL2 deficiency ameliorates hepatic steatosis by regulating lipid metabolism through the AKT/TET1/MTTP axis.These findings will help understand the pathogenesis of NAFLD and highlight the potency of RASAL2 as a new molecular target for NAFLD.

Enhanced ethanol oxidation over Pd nanoparticles supported porous graphene-doped MXene using polystyrene particles as sacrificial templates

Fabrication of superior catalytic performance palladium-based catalysts with affordable cost is the key to develop direct ethanol fuel cell.Herein,Pd-decorated three-dimensional(3D)porous constructed from graphene oxide(GO)and MXene combining with polystyrene(PS)particles as sacrificial templates(Pd/GO-MXene-PS)to elevate the catalytic performance for ethanol oxidation was proposed.The 3D porous interconnected structure of Pd/GO-MXene-PS was characterized by scanning electron microscope(SEM),transmission electron microscope(TEM)and Brunner−Emmet−Teller(BET).By optimizing the doping ratio of MXene to GO,the mass activity of Pd/GO_(5)-MXene_(5)-PS(2944.0 mA·mg^(−1))was 3.0 times higher than that of commercial Pd/C(950.4 mA·mg^(−1))toward ethanol oxidation in base solution.Meanwhile,the rotating disk electrode(RDE)results demonstrated that Pd/GO5-MXene5-PS had a faster kinetics of ethanol oxidation.The enhanced ethanol oxidation over Pd/GO5-MXene5-PS could attribute to the excellent 3D interconnected porous structure,large surface area,good conductivity and homogeneous Pd distribution.This work provided a new idea for creating 3D porous MXene composite materials in electrocatalysis.