Nonlinear branched flow of intense laser light in randomly uneven media

Branched flow is an interesting phenomenon that can occur in diverse systems.It is usually linear in the sense that the flow does not alter the properties of the medium.Branched flow of light on thin films has recently been discovered.It is therefore of interest to know whether nonlinear light branching can also occur.Here,using particle-in-cell simulations,we find that in the case of an intense laser propagating through a randomly uneven medium,cascading local photoionization by the incident laser,together with the response of freed electrons in the strong laser fields,triggers space–time-dependent optical unevenness.The resulting branching pattern depends dramatically on the laser intensity.That is,the branching here is distinct from the existing linear ones.The observed branching properties agree well with theoretical analyses based on the Helmholtz equation.Nonlinear branched propagation of intense lasers potentially opens up a new area for laser–matter interaction and may be relevant to other branching phenomena of a nonlinear nature.

sp^(3)-like defect structure of hetero graphene-carbon nanotubes for promoting carrier transfer and stability

Three-dimensional(3 D) hybrid of nanocarbons is a very promising way to the high-performance design of electrocatalysis materials.However,sp^(3)-like defect structure,a combination of high strength and conduction of graphene and carbon nanotubes(CNTs) is rarely reported.Herein,3 D neural-like hybrids of graphene(from reduced graphene oxide) and carbon nanotubes(CNTs) have been integrated via sp^(3)-like defect structure by a hydrothermal approach.The sp^(3)-like defect structure endows 3 D nanocarbon hybrids with an enhanced carrier transfer,high structural stability,and electrocatalytic durability.The neural-like structure is shown to demonstrate a cascade effect of charges and significant performances regarding bio-electrocatalysis and lithium-sulfur energy storage.The concept and mechanism of "sp^(3)-like defect structure" are proposed at an atomic/nanoscale to clarify the generation of rational structure as well as the cascade electron transfer.

Reflection and transmission properties of a finite-length electron plasma grating

Considered here is a plasma grating generated by two counterpropagating short laser pulses. Because of the shortness of the laser pulses, theplasma dynamics are determined by only electrons, which respond to the ponderomotive pressure generated by the interacting laser fields.An electron grating cannot exist for longer than the inverse ion plasma frequency, and so because of the limited time of the ponderomotivepressure, both the life time and spatial extent of an electron grating are finite. When one of the short laser pulses is circularly polarized(propagating in the x direction with electric field vectors in the yz plane) and the other is linearly y-polarized, the electron grating is producedby the y components. Meanwhile, the z component is partially reflected, and only a fraction of it is transmitted. Thus, the finite plasmagrating can either alter the polarization of the yz-polarized pulse or act as a pulse splitter. The present paper is focused on the reflection andtransmission rates. The action of the density grating on the z component cannot be explained by the Bloch wave theory for infinite crystals,and instead a theory is developed based on four-wave mixing, which explains the transmission and reflection of the z component wheninteracting with a grating of finite extent.

Generation of polarized electron beams through self-injection in the interaction of a laser with a pre-polarized plasma

Polarized electron beam production via laser wakefield acceleration in pre-polarized plasma is investigated by particlein-cell simulations.The evolution of the electron beam polarization is studied based on the Thomas±Bargmann±Michel±Telegdi equation for the transverse and longitudinal self-injection,and the depolarization process is found to be influenced by the injection schemes.In the case of transverse self-injection,as found typically in the bubble regime,the spin precession of the accelerated electrons is mainly influenced by the wakefield.However,in the case of longitudinal injection in the quasi-1D regime(for example,F.Y.Li et al.,Phys.Rev.Lett.110,135002(2013)),the direction of electron spin oscillates in the laser field.Since the electrons move around the laser axis,the net influence of the laser field is nearly zero and the contribution of the wakefield can be ignored.Finally,an ultra-short electron beam with polarization of 99%can be obtained using longitudinal self-injection.

Mangrove derived fungal endophytes–a chemical and biological perception

The potential of mangrove-derived endophytic fungi as a promising source of diverse and structurally unprecedented bioactive natural products is unquestionable and continues to attract considerable attention.This review highlights new bioactive mangrove fungal metabolites and known compounds with hitherto unreported biological activities described during the last 10 years.The compounds are categorized according to their reported biological activities,including cytotoxic,anti-infective,in addition to a wide range of miscellaneous activities such as protein kinase,αglucosidase,acetylcholinesterase and tyrosinase inhibitory activities,as well as antiangiogenic and neovascularisation effects,radical scavenging,DNA-binding affinity,and calcium and potassium channel blocking activity.

Endophytes and associated marine derived fungi—ecological and chemical perspectives

The potential of endophytes and algal or invertebrate associated marine derived fungi as promising sources of structurally unprecedented bioactive natural products is undeniable and continues to attract broad attention.This review highlights new bioactive fungal metabolites reported in 2011 until April 2012,as well as known compounds for which novel biological activities have been disclosed.All compounds are grouped according to their reported biological activities which include cytotoxic,anti-infective,as well as radical scavenging,enzyme inhibition,anti-fouling and anti-parasitic activities.Overall,178 fungal metabolites,including 138 new natural products are presented.Furthermore,new insights into fungal-host interaction,chemical communication,and chemo-ecological roles of fungal metabolites,as well as new strategies for bioprospecting are presented.

Relativistic electron acceleration by surface plasma waves excited with high intensity laser pulses

The process of high energy electron acceleration along the surface of grating targets(GTs)that were irradiated by a relativistic,high-contrast laser pulse at an intensity I=2.5×10^20 W/cm^2 was studied.Our experimental results demonstrate that for a GT with a periodicity twice the laser wavelength,the surface electron flux is more intense for a laser incidence angle that is larger compared to the resonance angle predicted by the linear model.An electron beam with a peak charge of∼2.7 nC/sr,for electrons with energies>1.5 MeV,was measured.Numerical simulations carried out with parameters similar to the experimental conditions also show an enhanced electron flux at higher incidence angles depending on the preplasma scale length.A theoretical model that includes ponderomotive effects with more realistic initial preplasma conditions suggests that the laser-driven intensity and preformed plasma scale length are important for the acceleration process.The predictions closely match the experimental and computational results.