Control of electron beam current,charge,and energy spread using density downramp injection in laser wakefield accelerators

Density downramp injection has been demonstrated to be an elegant and efficient approach for generating high-quality electron beams in laser wakefield accelerators.Recent studies have demonstrated the possibilities of generating electron beams with charges ranging from tens to hundreds of picocoulombs while maintaining good beam quality.However,the plasma and laser parameters in these studies have been limited to specific ranges or attention has been focused on separate physical processes such as beam loading,which affects the uniformity of the accelerating field and thus the energy spread of the trapped electrons,the repulsive force from the rear spike of the bubble,which reduces the transverse momentum P⊥of the trapped electrons and results in small beam emittance,and the laser evolution when traveling in the plasma.In this work,we present a comprehensive numerical study of downramp injection in the laser wakefield,and we demonstrate that the current profile of the injected electron beam is directly correlated with the density transition parameters,which further affects the beam charge and energy evolution.By fine-tuning the plasma density parameters,electron beams with high charge(up to several hundreds of picocoulombs)and low energy spread(around 1%FWHM)can be obtained.All these results are supported by large-scale quasi-threedimensional particle-in-cell simulations.We anticipate that the electron beams with tunable beam properties generated using this approach will be suitable for a wide range of applications.

One-dimensional chain of quantum molecule motors as a mathematical physics model for muscle fibers

A quantum chain model of multiple molecule motors is proposed as a mathematical physics theory for the microscopic modeling of classical force-velocity relation and tension transients in muscle fibers. The proposed model was a quantum many-particle Hamiltonian to predict the force-velocity relation for the slow release of muscle fibers, which has not yet been empirically defined and was much more complicated than the hyperbolic relationships. Using the same Hamiltonian model, a mathematical force-velocity relationship was proposed to explain the tension observed when the muscle was stimulated with an alternative electric current. The discrepancy between input electric frequency and the muscle oscillation frequency could be explained physically by the Doppler effect in this quantum chain model. Further more, quantum physics phenomena were applied to explore the tension time course of cardiac muscle and insect flight muscle. Most of the experimental tension transient curves were found to correspond to the theoretical output of quantum two- and three-level models. Mathematical modeling electric stimulus as photons exciting a quantum three-level particle reproduced most of the tension transient curves of water bug Lethocerus maximus.

Comparison of tunneling currents in graphene nanoribbon tunnel field effect transistors calculated using Dirac-like equation and Schrodinger’s equation

The tunneling current in a graphene nanoribbon tunnel field effect transistor(GNR-TFET) has been quantum mechanically modeled. The tunneling current in the GNR-TFET was compared based on calculations of the Dirac-like equation and Schrodinger’s equation. To calculate the electron transmittance, a numerical approach-namely the transfer matrix method(TMM)-was employed and the Launder formula was used to compute the tunneling current. The results suggest that the tunneling currents that were calculated using both equations have similar characteristics for the same parameters, even though they have different values. The tunneling currents that were calculated by applying the Dirac-like equation were lower than those calculated using Schrodinger’s equation.

Role of phase fluctuation and dephasing in the enhancing continuous variable entanglement of a two-photon coherent beat laser

A steady state analysis of the nonclassical features and statistical properties of the cavity radiation of a two- photon coherent beat laser is presented. Results show that the degree of two-mode squeezing, detectable entanglement and intensity of the cavity radiation can increase with the deviation of the phase fluctuations of the laser employed in preparing the atoms, but decrease with the increasing rate at which the induced coherence superposition decays. Although it is found that varying the phase fluctuations and dephasing can lead to modification in the quantum features and statistical properties of the radiation, it does not alter the similarity in the nature of the degree of entanglement detectable by the criteria following from Duan-Giedke-Cirac Zoller and logarithmic negativity in a perceivable manner. Since the intensity and quantum features can be readily enhanced, this system is expected to be a viable source of a strong robust entangled （squeezed） light under various conditions. Moreover, comparison of the mean number of photon pairs with intensity difference shows that the chance of inciting a two-photon process can be enhanced by changing the rate of dephasing and phase fluctuations.

Impact of Quantum Fluctuations on the Modulational Instability of a Modified Gross-Pitaevskii Equation with Two-Body Interaction

Modulational instability conditions for the generation of localized structures in the context of matter waves in Bose-Einstein condensates are investigated analytically and numerically. The model is based on a modified Gross-Pitaevskii equation, which account for the energy dependence of the two-body scattering amplitude. It is shown that the modified term due to the quantum fluctuations modify significantly the modulational instability gain. Direct numerical simulations of the full modified Gross-Pitaevskii equation are performed, and it is found that the modulated plane wave evolves into a train of pulses, which is destroyed at longer times due to the effects of quantum fluctuations.

Gene Expression Profiles Predict Sensitivity of Prostate Cancer to Radiotherapy

Ionizing radiation (IR) is the most common treatment used to control localized primary prostate cancer (PC). However, for a significant number of patients, radiotherapy fails to adequately control the tumor. Thus, a main clinical problem today is the lack of a specific marker that may be used to predict the treatment outcome and to identify prostate cancer patients who are unlikely to respond to radiation therapy. In this study, we used human PC xenografts with predetermined radioresistant/sensitive phenotypes, and gene expression microarrays, correlated their specific transcripttional profiles with response to radiation. Employing unsupervised two-way hierarchical clustering, we identified four gene clusters displaying different expression patterns. Two clusters showed higher expression levels in the resistant xenografts and the other two clusters showed higher expression levels in the sensitive xenografts. Expression levels of 113 genes differed by at least 3 fold between sensitive and resistant xenografts. These genes represent members of several cellular pathways, some of which are known to be associated with response to radiation. All or several of these genes could serve as predictive tools to determine at biopsy the expected response of a particular tumor to radiotherapy. Indeed, the profiles we identified enabled us to predict the degree of radiosensitivity of a panel of established PC cell lines. Importantly, irradiation of the PC xenografts did not induce any significant changes in gene expression, regardless of their susceptibility phenotype. These data strongly support the first of two models: a: a random effect of irradiation on a homogeneous population of cells, rather than b: of a tumor comprised of a mixture of radioresistant and radiosensitive cell subpopulations. Our findings imply that each of the radio-phenotypes represents different intrinsic characteristics that affect the ability of a tumor to survive radiotherapy.

Ⅱ-Ⅵ族稀磁半导体微纳结构中的激子磁极化子及其发光

自旋是基本粒子(电子、光子)角动量的内在形式.固体中体现自旋特征的集体电子行为如拓扑绝缘体等是当前凝聚态物理领域关注的焦点,是基态行为.激子作为电子空穴对的激发态且寿命很短,可复合发光,它是否能体现自旋极化主导的行为?对此人们的认识远不如针对基态的电子.激子磁极化子(exciton magnetic polaron, EMP)是由磁性半导体微结构中铁磁自旋耦合态与自由激子相互作用形成的复合元激发,但其研究很有限.本文概述了我们在稀磁半导体微纳米结构中的EMP及其发光动态学光谱、自旋极化激子凝聚态的形成方面取得的一些进展,展望了未来可能在自旋光电子器件、磁控激光、光致磁性等量子技术方面的潜在应用.

Ghost images reconstructed from fractional-order moments with thermal light

We present the joint probability density function(PDF) between the bucket signals and reference signals in thermal light ghost imaging, by regarding these signals as stochastic variables. The joint PDF allows us to examine the fractional-order moments of the bucket and the reference signals, in which the correlation orders are fractional numbers,other than positive integers in previous studies. The experimental results show that various images can be reconstructed from fractional-order moments. Negative(positive) ghost images are obtained with negative(positive) orders of the bucket signals. The visibility and peak signal-to-noise ratios of the diverse ghost images depend greatly on the fractional orders.

Revealing the topological phase diagram of ZrTe_(5) using the complex strain fields of microbubbles

Topological materials host robust properties,unaffected by microscopic perturbations,owing to the global topological properties of the bulk electron system.Materials in which the topological invariant can be changed by easily tuning external parameters are especially sought after.Zirconium pentatelluride(ZrTe_(5))is one of a few experimentally available materials that reside close to the boundary of a topological phase transition,allowing the switching of its invariant by mechanical strain.Here,we unambiguously identify a topological insulator–metal transition as a function of strain,by a combination of ab initio calculations and direct measurements of the local charge density.Our model quantitatively describes the response to complex strain patterns found in bubbles of few layer ZrTe_(5) without fitting parameters,reproducing the mechanical deformation-dependent closing of the band gap observed using scanning tunneling microscopy.We calculate the topological phase diagram of ZrTe_(5) and identify the phase at equilibrium,enabling the design of device architectures,which exploit the topological switching characteristics of the system.

Femtosecond electron microscopy of relativistic electron bunches

The development of plasma-based accelerators has enabled the generation of very high brightness electron bunches of femtosecond duration,micrometer size and ultralow emittance,crucial for emerging applications including ultrafast detection in material science,laboratory-scale free-electron lasers and compact colliders for high-energy physics.The precise characterization of the initial bunch parameters is critical to the ability to manipulate the beam properties for downstream applications.Proper diagnostic of such ultra-short and high charge density laser-plasma accelerated bunches,however,remains very challenging.Here we address this challenge with a novel technique we name as femtosecond ultrarelativistic electron microscopy,which utilizes an electron bunch from another laser-plasma accelerator as a probe.In contrast to conventional microscopy of using very low-energy electrons,the femtosecond duration and high electron energy of such a probe beam enable it to capture the ultra-intense space-charge fields of the investigated bunch and to reconstruct the charge distribution with very high spatiotemporal resolution,all in a single shot.In the experiment presented here we have used this technique to study the shape of a laser-plasma accelerated electron beam,its asymmetry due to the drive laser polarization,and its beam evolution as it exits the plasma.We anticipate that this method will significantly advance the understanding of complex beam-plasma dynamics and will also provide a powerful new tool for real-time optimization of plasma accelerators.

Replica higher-order topology of Hofstadter butterflies in twisted bilayer graphene

The Hofstadter energy spectrum of twisted bilayer graphene(TBG)is found to have recursive higher-order topological properties.We demonstrate that higher-order topological insulator(HOTI)phases,characterized by localized corner states,occur as replicas of the original HOTIs to fulfill the self-similarity of the Hofstadter spectrum.We show the existence of exact flux translational symmetry in TBG at all commensurate angles.Based on this result,we identify that the original HOTI phase at zero flux is re-entrant at a half-flux periodicity,where the effective twofold rotation is preserved.In addition,numerous replicas of the original HOTIs are found for fluxes without protecting symmetries.Like the original HOTIs,replica HOTIs feature both localized corner states and edge-localized real-space topological markers.The replica HOTIs originate from the different interaction scales,namely,intralayer and interlayer couplings,in TBG.The topological aspect of Hofstadter butterflies revealed in our results highlights symmetry-protected topology in quantum fractals.

Risk and mechanism of metabolic syndrome associated with radiation exposure

Obesity, hyperglycemia, hypertension, hypertriglyceridemia and low high-density lipoprotein cholesterol are the typical features of Metabolic syndrome (MetS). Exploring the risk factors would benefit for prevention control. Several studies have revealed an association between ionizing radiation (IR) exposure and MetS, likely attributable to production of reactive oxygen species (ROS), oxidative stress, DNA damage. Understanding the health effects of IR exposure, which have long been overlooked, would improve knowledge on MetS and help identify effective strategies for targeted prevention of MetS. In this review, we first highlight the importance of IR and MetS, providing information on the wide use of IR in the field, IR-induced damage, and the prevalence and burden of MetS. Then, we summarize the findings association between IR and various components of MetS addressing the dual effects of IR on MetS in a dose-response manner. Although there remain unresolved challenges, study on the association of radiation and MetS could open new perspectives in the future.

Simultaneous creation of multiple vortex-antivortex pairs in momentum space in photonic lattices

Engineering of the orbital angular momentum(OAM)of light due to interaction with photonic lattices reveals rich physics and motivates potential applications.We report the experimental creation of regularly distributed quantized vortex arrays in momentum space by probing the honeycomb and hexagonal photonic lattices with a single focused Gaussian beam.For the honeycomb lattice,the vortices are associated with Dirac points.However,we show that the resulting spatial patterns of vortices are strongly defined by the symmetry of the wave packet evolving in the photonic lattices and not by their topological properties.Our findings reveal the underlying physics by connecting the symmetry and OAM conversion and provide a simple and efficient method to create regularly distributed multiple vortices from unstructured light.

MEP pathway products allosterically promote monomerization of deoxy-D-xylulose-5-phosphate synthase to feedback-regulate their supply

Isoprenoids are a very large and diverse family of metabolites required by all living organisms.All isoprenoids derive fromthe double-bond isomers isopentenyl diphosphate(IPP)and dimethylallyl diphosphate(DMAPP),which are produced by the methylerythritol 4-phosphate(MEP)pathway in bacteria and plant plastids.It has been reported that IPP and DMAPP feedback-regulate the activity of deoxyxylulose 5-phosphate synthase(DXS),a dimeric enzyme that catalyzes the main flux-controlling step of the MEP pathway.Here we provide experimental insights intotheunderlyingmechanism.Isothermal titration calorimetry and dynamic light scattering approaches showed that IPP and DMAPP can allosterically bind to DXS in vitro,causing a size shift.In silico ligand binding site analysis and docking calculations identified a potential allosteric site in the contact region between the two monomers of the active DXS dimer.Modulation of IPP and DMAPP contents in vivo followed by immunoblot analyses confirmed that high IPP/DMAPP levels resulted in monomerization and eventual aggregation of the enzyme in bacterial and plant cells.Loss of the enzymatically active dimeric conformation allows a fast and reversible reduction of DXS activity in response to a sudden increase or decrease in IPP/DMAPP supply,whereas aggregation and subsequent removal of monomers that would otherwise be available for dimerization appears to be a more drastic response in the case of persistent IPP/DMAPP overabundance(e.g.,by a blockage in their conversion to downstream isoprenoids).Our results represent an important step toward understanding the regulation of the MEP pathway and rational design of biotechnological endeavors aimed at increasing isoprenoid contents in microbial and plant systems.

Nontrivial coupling of light into a defect:the interplay of nonlinearity and topology

The flourishing of topological photonics in the last decade was achieved mainly due to developments in linear topological photonic structures.However,when nonlinearity is introduced,many intriguing questions arise.For example,are there universal fingerprints of the underlying topology when modes are coupled by nonlinearity,and what can happen to topological invariants during nonlinear propagation?To explore these questions,we experimentally demonstrate nonlinearity-induced coupling of light into topologically protected edge states using a photonic platform and develop a general theoretical framework for interpreting the mode-coupling dynamics in nonlinear topological systems.Performed on laser-written photonic Su-Schrieffer-Heeger lattices,our experiments show the nonlinear coupling of light into a nontrivial edge or interface defect channel that is otherwise not permissible due to topological protection.Our theory explains all the observations well.Furthermore,we introduce the concepts of inherited and emergent nonlinear topological phenomena as well as a protocol capable of revealing the interplay of nonlinearity and topology.These concepts are applicable to other nonlinear topological systems,both in higher dimensions and beyond our photonic platform.

Conversion of out-of-phase to in-phase order in coupled laser arrays with second harmonics

A novel method for converting an array of out-of-phase lasers into one of in-phase lasers that can be tightly focused is presented.The method exploits second-harmonic generation and can be adapted for different laser arrays geometries.Experimental and calculated results,presented for negatively coupled lasers formed in a square,honeycomb,and triangular geometries are in good agreement.

Impact of non-Hermitian mode interaction on inter-cavity light transfer

Understanding inter-site mutual mode interaction in coupled physical systems is essential to comprehend large compound systems,as this local interaction determines the successive multiple inter-site energy transfer efficiencies.In the present study,we demonstrate that only the non-Hermitian coupling can correctly account for the light transfer between two coupled optical cavities.We also reveal that the non-Hermitian coupling effect becomes crucial as the system dimension decreases.Our results provide important insight for handling general-coupled devices in the subwavelength regime.

Polarization Flipping of Even-Order Harmonics in Monolayer Transition-Metal Dichalcogenides

We present a systematic study of the crystal-orientation dependence of high-harmonic generation in monolayer transition-metal dichalcogenides,WS2 and MoSe2,subjected to intense linearly polarized midinfrared laser fields.The measured spectra consist of both odd-and even-order harmonics,with a high-energy cutoff extending beyond the 15th order for a laser-field strength around~1 V/nm.In WS2,we find that the polarization direction of the odd-order harmonics smoothly follows that of the laser field irrespective of the crystal orientation,whereas the direction of the even-order harmonics is fixed by the crystal mirror planes.Furthermore,the polarization of the even-order harmonics shows a flip in the course of crystal rotation when the laser field lies between two of the crystal mirror planes.By numerically solving the semiconductor Bloch equations for a gapped-graphene model,we qualitatively reproduce these experimental features and find the polarization flipping to be associated with a significant contribution from interband polarization.In contrast,high-harmonic signals from MoSe2 exhibit deviations from the laser-field following of oddorder harmonics and crystal-mirror-plane following of even-order harmonics.We attribute these differences to the competing roles of the intraband and interband contributions,including the deflection of the electron-hole trajectories by nonparabolic crystal bands.

Bloch theorem dictated wave chaos in microcavity crystals

Universality class of wave chaos emerges in many areas of science,such as molecular dynamics,optics,and network theory.In this work,we generalize the wave chaos theory to cavity lattice systems by discovering the intrinsic coupling of the crystal momentum to the internal cavity dynamics.The cavity-momentum locking substitutes the role of the deformed boundary shape in the ordinary single microcavity problem,providing a new platform for the in situ study of microcavity light dynamics.The transmutation of wave chaos in periodic lattices leads to a phase space reconfiguration that induces a dynamical localization transition.The degenerate scar-mode spinors hybridize and non-trivially localize around regular islands in phase space.In addition,we find that the momentum coupling becomes maximal at the Brillouin zone boundary,so the intercavity chaotic modes coupling and wave confinement are significantly altered.Our work pioneers the study of intertwining wave chaos in periodic systems and provide useful applications in light dynamics control.

Nanostructured biohybrid material with wide-ranging antiviral action

Respiratory pathogens kill more people than any other infectious agent each year worldwide.Development of novel,economically friendly,sustainable,and highly efficient materials against viruses is a major challenge.Herein,we describe a nanostructured material composed of very small crystalline phosphate copper nanoparticles synthesized using a new biohybrid technology that employs a biological agent for its formation at room temperature in aqueous media.The evaluation of different enzymes in the final preparation of the nanomaterial or even in synthetic methods was performed.Biochemical characterization revealed the formation of Cu species in the protein network.The best biomaterial synthesized using a lipase called BioCuNPs showed excellent inhibition capacity against functional proteins of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2);for example,assent 3-chymotrypsin like protease(3CLpro)complete inhibition was achieved by using 5µg/mL,or acetone(ACE)–spike protein interaction was inhibited by more than 80%in the presence of 400µg/mL of BioCuNPs.Taking these in vitro results into account,an efficacy analysis against human coronavirus 229E(HCoV-E229)coronavirus was performed.A virus reduction of 99%was obtained in 5 min.Additionally,SARS-CoV-2 virus was tested to demonstrate high efficiency,with>99%inhibition in 15 min using 500 microgram of material.To determine the wide applicability of this nanohybrid against viruses,an evaluation was carried out against a non-enveloped virus such as Human Rhinovirus(HRV-14),obtaining a virus reduction of 99.9%in 5 min.Finally,the virucidal capacity against different bacteriophages was also evaluated,obtaining an excellent inhibition effect against PhageΦX174(99.999%reduction in 5 min).