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The interaction and interpenetration of two counter-propagating plasma shocks are investigated via hybrid fluid-PIC (particle-in-cell) simulations. This study seeks to probe the kinetic effects and ion collisions on the structure of colliding plasma shocks in complex multi-ion-species plasma, in particular, the presence of the expansion of high- Z plasma bubbles against the low- Z filled gas inside an ICF hohlraum. The superposition of shock wave results in a wave-like electric field in the downstream region. The electric field can further reduce the kinetic energy of the incoming particles, and modulate the ion density profile. It finally generates a new downstream platform of high temperature and high density. However, on the hundred-ps time scale, cumulative ion collisions can still significantly alter the structure of the shock wave and the reflection of ions by the shock front. This study will help to improve the predictions of hohlraum plasma states and the understanding of the shock wave interactions.

M-type stars are the ones that flare most frequently, but how big their maximum flare energy can reach is still unknown. We present 163 flares from 162 individual M2 through L1-type stars that triggered the GWAC, with flare energies ranging from 10 ^32.2 to 10 ^36.4 erg. The flare amplitudes range from △ G = 0.84 to ∼10 mag. Flare energy increases with stellar surface temperature ( T _eff ) but both △ G and equivalent duration ${\mathrm{log}}_{10}(\mathrm{ED})$ seem to be independent of T _eff . Combining periods detected from light curves of TESS and K2, spectra from LAMOST, the Sloan Digital Sky Survey, the 2.16 m telescope, and the Gaia DR3 data, we found that these GWAC flare stars are young. For the stars that have spectra, we found that these stars are in or very near the saturation region, and ${\mathrm{log}}_{10}({L}_{{\rm{H}}\alpha }/{L}_{\mathrm{bol}})$ is lower for M7–L1 stars than for M2–M6 stars. We also studied the relation between GWAC flare bolometric energy E _bol and stellar hemispherical area S , and found that ${\mathrm{log}}_{10}{E}_{\mathrm{bol}}$ (in erg) increases with increasing S (in square centimeters), and the maximum flare energy ${\mathrm{log}}_{10}{E}_{\mathrm{bol},\ \max }\geqslant {\mathrm{log}}_{10}S+14.25$ . For M7–L1 stars, there seem to be other factors limiting their maximum flare energies in addition to the stellar hemispherical area.

The impact of capsule imperfections is one of the challenges in achieving reproducible, high-gain ignition of inertial confinement fusion (ICF). The nonuniformities of capsule imperfections, which create instability seeds during the shock propagation, may cause significant performance degradation. A systematic study of the propagation of collisional shock wave in highly nonuniform plasmas is carried out using a hybrid fluid-PIC code, which enables the analysis of electromagnetic fields, ion mixing, and plasma viscosity self-consistently. During shock propagation, it interacts with multiple bubbles and significant material mixing in the nonuniform plasmas are observed. Consequently, the average viscosity of the post-shock plasma in the nonuniform case increases to $1\sim 2$ times that of the uniform case. These results provide a better understanding of the possible influence of capsule imperfections in ICF implosions.

Stellar white-light flares are believed to play an essential role in the physical and chemical properties of the atmosphere of the surrounding exoplanets. Here we report an optical monitoring campaign on the nearby flaring system EI Cnc carried out by the Ground-based Wide Angle Camera (GWAC) and its dedicated follow-up telescope. A superflare, coming from the brighter component EI CncA, was detected and observed, in which four components are required to properly model the complex decay light curve. The lower limit of flare energy in the R − band is estimated to be 3.3 × 10 ^32 erg. A total of 27 flares are additionally detected from the GWAC archive data with a total duration of 290 hr. The inferred cumulative flare frequency distribution follows a quite shallow power-law function with a slope of β = − 0.50 ± 0.03 over the energy range between 10 ^30 and 10 ^33 erg, which reinforces the trend that stars cooler than M4 show enhanced superflare activity. The flares identified in EI Cnc enable us to extend the τ – E relationship previously established in the white-light superflares of solar-type stars down to an energy as low as ∼10 ^30 erg (i.e., by 3 orders): τ ∝ E ^0.42±0.02 , which suggests a common flare mechanism for stars with a type from M to solar-like and implies an invariant of B ^1/3 υ _A in the white-light flares.

Shock-driven hydrodynamic instabilities in a plasma usually lead to interfacial mixing and the generation of electromagnetic fields, which are nonequilibrium processes coupling kinetics with meso- and macroscopic dynamics. The understanding and modeling of these physical processes are very challenging tasks for single-fluid hydrodynamic codes. This work presents a new framework that incorporates both kinetics and hydrodynamics to simulate shock waves and hydrodynamic instabilities in high-density plasmas. In this hybrid code, ions are modeled using the standard particle-in-cell method together with a Monte Carlo description of collisions while electrons are modeled as a massless fluid, with the electron heat flux and fluid–particle energy exchange being considered in the electron pressure equation. In high-density plasmas, Maxwell’s equations are solved using Ohm’s law instead of Ampère’s law. This hybrid algorithm retains ion kinetic effects and their consequences for plasma interpenetration, shock wave propagation, and hydrodynamic instability. Furthermore, we investigate the shock-induced (or gravity-induced) turbulent mixing between a light and a heavy plasma, where hydrodynamic instabilities are initiated by a shock wave (or gravity). This study reveals that self-generated electromagnetic fields play a role in the formation of baroclinic vorticity along the interface and in late-time mixing of the plasmas. Our results confirm the ability of the proposed method to describe shock-driven hydrodynamic instabilities in a plasma, in particular, nonequilibrium processes that involve mixing and electromagnetic fields at the interface.

In proton radiography, degeneracy of electric and magnetic fields in deflecting the probe protons can prevent full interpretation of proton flux perturbations in the detection plane. In this paper, theoretical analyses and numerical simulations suggest that the contributions of the electric and magnetic fields can be separately obtained by analyzing the difference between the flux distributions of two discriminated proton energies in a single shot of proton radiography. To eliminate the influence of field evolution on the separation, a strategy is proposed in which slow field evolution is assumed or an approximate estimate of field growth is made. This could help achieve a clearer understanding of the radiographic process and allow further quantitative analysis.

The effect of an externally applied magnetic field on the ion acceleration by laser-driven collisionless shocks is examined by means of multi-dimensional particle-in-cell simulations. For the interaction of ultra-intense sub-picosecond laser pulses with the near-relativistic critical-density plasma, the longitudinal transport of the laser generated fast electrons are significantly inhibited by the kilo-Tesla (kT) level transverse magnetic field, resulting in a thermal pressure which significantly exceeds the laser radiation pressure in the hot electron accumulation region. As a result, the accumulated plasma expands into the vacuum and leads to acceleration of a supersonic plasma flow in the opposite direction through the rocket effect, which streams into the target and drives a supercritical magnetized collisionless shock. In comparison with the case without the external magnetic field, where an electrostatic collisionless shock can be driven, the energy flux of the shock accelerated quasi-monoenergetic ion beam is considerably increased by an order of magnitude due to the strength enhancement of the magnetized shock.

Objective: To summarize Professor Xie's clinical experience in treating the deficiency cold of spleen and stomach type of complex peptic ulcer. Methods: through the observation of the curative effect of the patients with the deficiency cold of spleen and stomach type of complex peptic ulcer in the outpatient department of liver, spleen and stomach department of our hospital, the dialectical application and clinical experience of Professor Xie Jingri's self-made prescription in clinical practice were summarized. Results: Professor Xie Jingri's self-made prescription can effectively improve the clinical symptoms of patients with the deficiency cold of spleen and stomach type of complex peptic ulcer, and through individual syndrome differentiation and treatment, make the self-made prescription vary from person to person, clinical addition and subtraction, so as to further improve the clinical efficacy of patients. Conclusion: Professor Xie Jingri's self-made prescription is effective in treating complex peptic ulcer of spleen stomach deficiency cold type, which is worthy of further clinical application and promotion. [ABSTRACT FROM AUTHOR]

The Weibel instability, a subject of relevance to many fields of physics ranging from inertial confinement fusion to some astrophysical scenarios, is usually probed with side-on proton radiography. In order to diagnose the strength and wavelength of the spontaneous fields, two concerns that must be settled are how to distinguish the coexisting electric and magnetic fields, and how to overcome the counteracting of deflections in radiographing the filamentary structured fields. In this paper, proton radiography of the Weibel instability in two counterstreaming plasma flows is studied by simulation. It suggests that the electric field dominates the deflection of probe protons, whereas the contribution from the magnetic field is negligible. To resolve the deflectioncounteracting problem, the spatial spectrum of the electric field energy is found to be related to the deflection velocity of the probe beam by theoretical analyses. The strength and wavelength of the electric field are then obtainable from the proton flux on the detection plane, whereas the strength and wavelength of the magnetic field can be deduced through the equilibrium between the electric field and the magnetic field pressure gradient after the linear growth stage of the instability. Both numerical and experimental verifications suggest that our method performs well in extracting the strength and wavelength of the spontaneous electric and magnetic fields of the Weibel instability from proton radiography. [ABSTRACT FROM AUTHOR]

A scheme for neutron production is investigated in which an ultra-intense laser is irradiated into a two-layer (deuterium and aurum) spherical shell target through the cone shaped entrance hole. It is found that the energy conversion efficiency from laser to target can reach as high as 71%, and deuterium ions are heated to a maximum energy of several MeV from the inner layer surface. These ions are accelerated towards the center of the cavity and accumulated finally with a high density up to tens of critical density in several picoseconds. Two different mechanisms account for the efficient yield of the neutrons in the cavity: (1) At the early stage, the neutrons are generated by the high energy deuterium ions based on the "beam-target" approach. (2) At the later stage, the neutrons are generated by the thermonuclear fusion when the most of the deuterium ions reach equilibrium in the cavity. It is also found that a large number of deuterium ions accelerated inward can pass through the target center and the outer Au layer and finally stopped in the CD2 layer. This also causes efficient yield of neutrons inside the CD2 layer due to "beam-target" approach. A postprocessor has been designed to evaluate the neutron yield and the neutron spectrum is obtained. [ABSTRACT FROM AUTHOR]

A novel double cone funnel target design aiming at efficiently guiding and focusing fast electron beams produced in high intensity (>1019W/cm2) laser-solid interactions is investigated via two-dimensional particle-in-cell simulations. The forward-going fast electron beams are shown to be directed and focused to a smaller size in comparison with the incident laser spot size. This plasma funnel attached on the cone target guides and focuses electrons in a manner akin to the control of liquid by a plastic funnel. Such device has the potential to add substantial design flexibility and prevent inefficiencies for important applications such as fast ignition. Two reasons account for the collimation of fast electron beams. First, the sheath electric fields and quasistatic magnetic fields inside the vacuum gap of the double cone provide confinement of the fast electrons in the laser-plasma interaction region. Second, the interface magnetic fields inside the beam collimator further guide and focus the fast electrons during the transport. The application of this technique to cone-guided fast ignition is considered, and it is shown that it can enhance the laser energy deposition in the compressed fuel plasma by a factor of 2 in comparison with the single cone target case. [ABSTRACT FROM AUTHOR]

An analytical fluid model is proposed for artificially collimating fast electron beams produced in the interaction of ultraintense laser pulses with specially engineered low-density-core-high-density-cladding structure targets. Since this theory clearly predicts the characteristics of the spontaneously generated magnetic field and its dependence on the plasma parameters of the targets transporting fast electrons, it is of substantial relevance to the target design for fast ignition. The theory also reveals that the rapid changing of the flow velocity of the background electrons in a transverse direction (perpendicular to the flow velocity) caused by the density jump dominates the generation of a spontaneous interface magnetic field for these kinds of targets. It is found that the spontaneously generated magnetic field reaches as high as 100 MG, which is large enough to collimate fast electron transport in overdense plasmas. This theory is also supported by numerical simulations performed using a two-dimensional particle-in-cell code. It is found that the simulation results agree well with the theoretical analysis. [ABSTRACT FROM AUTHOR]

The energy distribution of the produced high energy electrons in the interaction of ultraintense picosecond laser pulses with high-Z solid targets is shown to be sensitive to the preformed plasma created by the prepulse and the amplified spontaneous emission pedestal. The created preformed plasmas, which are obtained by radiation hydrodynamic simulations for the present heating laser system at ILE, Osaka University, are seen to extend up to 30–100 μm just before the arrival of the main pulse. The dependences of the coupling efficiency of the laser energy to high energy electrons, and the energy spectra of these accelerated electrons, on this preformed plasma, are studied via a two-dimensional particle-in-cell simulation code. It is found that in a small preformed plasma case, J×B heating is dominant and the produced electron temperature agrees well with Haines’ scaling law [Haines et al., Phys. Rev. Lett., 102, 045008 (2009)]. While in a large preformed plasma case, in addition to J×B heating and/or vacuum heating, other acceleration mechanisms, such as stochastic heating, can accelerate electrons to very high energies, carrying a significant fraction of input laser energy. Even after several picoseconds, the number of high energy electrons (0.5 MeV

1. The present study was designed to determine the effects of ginkgolide A, ginkgolide B and quercetin on CYP3A protein expression and enzyme activity in primary cultures of human hepatocytes. 2. Hepatocytes were pretreated with ginkgolide A, ginkgolide B and quercetin (at 1, 3, 10 and 30 µmol/L) for 48 h and then exposed to testosterone (250 µmol/L) for 30 min. Rifampin (10 µmol/L) and phenobarbital (2 mmol/L) were used as positive controls. The CYP3A activity was measured by the amount of 6β-hydroxytestosterone in the culture medium and CYP3A protein in hepatocyte lysate was semiquantified by immunoblotting. 3. Compared with the vehicle control, ginkgolides A and B, at 30 µmol/L, significantly induced CYP3A protein expression (2.1- and 2-fold, respectively; both P < 0.01) and markedly induced CYP3A-mediated testosterone 6β-hydroxylation (2.5-fold each; P < 0.05 for ginkgolide A; P > 0.05 for ginkgolide B). Quercetin had no apparent induction. 4. Ginkgolide A and ginkgolide B can induce CYP3A protein expression and enzyme activity in primary cultures of human hepatocytes at higher doses. [ABSTRACT FROM AUTHOR]

An analytical fluid model for vacuum heating during the oblique incidence by an ultrashort ultraintense p-polarized laser on a solid-density plasma is proposed. The steepening of an originally smooth electron density profile as the electrons are pushed inward by the laser is included self-consistently. It is shown that the electrons being pulled out and then returned to the plasma at the interface layer by the wave field can lead to a phenomenon like wave breaking since the front part of the returning electrons always move slower than the trailing part. This can lead to heating of the plasma at the expense of the wave energy. An estimate for the efficiency of laser energy absorption by the vacuum heating is given. It is also found that for the incident laser intensity parameter, aL>0.5, the absorption rate peaks at an incident angle 45°-52° and it reaches a maximum of 30% at aL≈1.5. [ABSTRACT FROM AUTHOR]

The anomalous mix at the high-Z and low-Z plasma interfaces in an inertial confinement fusion hohlraum is a current topic of interest. The mechanism for such an anomalous mix in the interpenetration layer at the high-Z and low-Z plasma interface and its effects on the laser plasma instabilities have been investigated by particle-in-cell simulations. It is found that a diffusion-driven collisionless shock wave can be generated from an initially sharp high-Z and low-Z plasma interface with total pressure balance and constant temperature in the laser propagation channel. This purely electrostatic shock wave propagates into the high-Z plasma and leads to mix of different species of ions which is significantly faster than a classical mix in the presence of the large electric field. The mix layer width, measured as a separation distance affected by the shock, grows as , where . The effect of the anomalous mix on the linear growth rate of laser plasma instabilities is evaluated. [ABSTRACT FROM AUTHOR]

The role of ion–ion acoustic instabilities in the formation and dissipation of collisionless electrostatic shock waves driven by counter-streaming supersonic plasma flows has been investigated via two-dimensional particle-in-cell simulations. The nonlinear evolution of unstable waves and ion velocity distributions has been analyzed in detail. It is found that for electrostatic shocks driven by moderate-velocity flows, longitudinal and oblique ion–ion acoustic instabilities can be excited in the downstream and upstream regions, which lead to thermalization of the transmitted and reflected ions, respectively. For high-velocity flows, oblique ion–ion acoustic instabilities can develop in the overlap layer during the shock formation process and impede the shock formation. [ABSTRACT FROM AUTHOR]

Observations of anomalous neutron yield in the indirect-drive inertial confinement fusion implosion experiments conducted at SG-III prototype and SG-II upgrade laser facilities are interpreted. The anomalous mechanism results in a neutron yield which is 100-times higher than that predicted by 1D radiation-hydrodynamic simulations. 2D radiation-hydrodynamic simulations show that the supersonic, radially directed gold (Au) plasma jets arising from the laser-hohlraum interactions can collide with the carbon-deuterium (CD) corona plasma of the compressed pellet. It is found that in the interaction front of the high-Z jet with the low-Z corona, with low density  ∼ and high temperature  ∼keV, kinetic effects become important. Particle-in-cell simulations indicate that an electrostatic shock wave can be driven when the high-temperature Au jet expands into the low-temperature CD corona. Deuterium ions with an amount of  ∼1015 can be accelerated to  ∼25 keV by the collisionless shock wave, thus causing efficient neutron productions though the beam-target method by stopping these energetic ions in the corona. The evaluated neutron yield is consistent with the experiments conducted at SG laser facilities. [ABSTRACT FROM AUTHOR]

Fast ignition approach to inertial confinement fusion is one of the important goals today, in addition to central hot spot ignition in China. The SG-IIU and PW laser facilities are coupled to investigate the hot spot formation for fast ignition. The SG-III laser facility is almost completed and will be coupled with tens kJ PW lasers for the demonstration of fast ignition. In recent years, for physical studies of fast ignition, we have been focusing on the experimental study of implosion symmetry, M-band radiation preheating and mixing, advanced fast ignition target design, and so on. In addition, the modeling capabilities and code developments enhanced our ability to perform the hydro-simulation of the compression implosion, and the particle-in-cell (PIC) and hybrid-PIC simulation of the generation, transport and deposition of relativistic electron beams. Considerable progress has been achieved in understanding the critical issues of fast ignition. [ABSTRACT FROM AUTHOR]

A self-generation mechanism of magnetic dipoles and the anomalous energy dissipation of fast electrons in a magnetized beam-plasma system are presented. Based on two-dimensional particle-in-cell simulations, it is found that the magnetic dipoles are self-organized and play important roles in the beam electron energy dissipation. These dipoles drift slowly in the direction of the return flow with a quasisteady velocity, which depends upon the magnetic amplitude of the dipole and the imposed external magnetic field. This dipole formation provides a mechanism for the anomalous energy dissipation of a relativistic electron beam, which would play an important role in collisionless shock and ion shock acceleration. [ABSTRACT FROM AUTHOR]