On the Energy Budget of Starquake-induced Repeating Fast Radio Bursts

With a growing sample of fast radio bursts(FRBs),we investigate the energy budget of different power sources within the framework of magnetar starquake triggering mechanism.During a starquake,the energy can be released in any form through strain,magnetic,rotational,and gravitational energies.The strain energy can be converted from three other kinds of energy during starquakes.The following findings are revealed:(1)The crust can store free magnetic energy of~10^(46)erg by existing toroidal fields,sustaining 10^(6)bursts with frequent starquakes occurring due to crustal instability.(2)The strain energy develops as a rigid object spins down,which can be released during a global starquake accompanied by a glitch.However,it takes a long time to accumulate enough strain energy via spindown.(3)The rotational energy of a magnetar with P■0.1 s can match the energy and luminosity budget of FRBs.(4)The budget of the total gravitational energy is high,but the mechanism and efficiency of converting this energy to radiation deserve further exploration.

Exploration of the “Four-Three-Four” Internship and Training Mode in Higher Vocational Colleges Under the Modern Vocational Education System

This article mainly introduces the innovative internship and training model of vocational colleges,including five aspects such as“four-party collaboration,three-stage progression,four-way integration,value-added evaluation,and double selection and promotion.”The model aims to improve students’practical skills and professional quality to better adapt to market demand and social development.The article also presents the prospects of the future internship and training model,including strengthening cooperation and communication with industry enterprises,focusing on students’personalized development and practical skill cultivation,and establishing a scientific and objective evaluation and feedback mechanism.

Hydro-Chemical Processes in Lake Qinghai throughout Climate Warming: In Situ Investigations of the Largest Lake in China

In the wake of climate warming, the water level of Lake Qinghai has been continuously and rapidly declining during the past decades, causing the regional government and citizens to worry about its future as a water resource. To understand the lake evolution process, the hydro-chemical characteristics of Lake Qinghai were investigated in August of 2008. The results show that Na+ and Cl- are the dominant cations and anions in the lake water, respectively, and hydrochemistry type is Cl-- Na+ with an obvious characteristic of a saline lake. The Gibbs plot illuminates that evaporation/crystallization is responsible for the chemical composition of the lake water. The variation in hydro-chemical regime might be attributed to the reduced lake levels between 1960s and 2000s. The lake level significantly correlated with the precipitation and evaporation in the Lake Qinghai catchment. In addition, changes of the lake level in the future are simulated according to climate warming scenarios from the IPCC report. The simulated results suggest that the lake level could rise again in the following decades due to the increased precipitation under the climate warming conditions, which is already a trend in the lake level observation data.

The Tianlin Mission:A 6m UV/Opt/IR Space Telescope to Explore Habitable Worlds and the Universe

It is expected that ongoing and future space-borne planet survey missions including Transiting Exoplanet Survey Satellite(TESS),PLATO and Earth 2.0 will detect thousands of small to medium-sized planets via the transit technique,including over a hundred habitable terrestrial rocky planets.To conduct a detailed study of these terrestrial planets,particularly the cool ones with wide orbits,the exoplanet community has proposed various follow-up missions.The currently proposed European Space Agency mission Ariel is the first step for this purpose,and it is capable of characterization of planets down to warm super-Earths mainly using transmission spectroscopy.The NASA Large Ultraviolet/Optical/Infrared Surveyor mission proposed in the Astro2020 Decadal Survey white paper will endeavor to further identify habitable rocky planets,and is expected to launch around 2045.In the meanwhile,China is funding a concept study of a 6 m class space telescope named Tianlin(a UV/Opt/NIR large aperture space telescope)that aims to start its operation within the next 10–15 yr and last for 5+yr.Tianlin will be primarily aimed at the discovery and characterization of rocky planets in the habitable zones around nearby stars and to search for potential biosignatures mainly using the direct imaging method.Transmission and emission spectroscopy at moderate to high resolution will be carried out as well on a population of exoplanets to strengthen the understanding of the formation and evolution of exoplanets.It will also be utilized to perform in-depth studies of the cosmic web and early galaxies,and constrain the nature of dark matter and dark energy.We describe briefly the primary scientific motivations and main technical considerations based on our preliminary simulation results.We find that a monolithic off-axis space telescope with primary mirror diameter larger than 6 m equipped with a high contrast coronagraph can identify water in the atmosphere of a habitable-zone Earth-like planet around a Sunlike star.More simulations for the detectability of other key biosignatures including O_(3),O_(2),CH_(4)and chlorophyll are coming.

Are There Magnetars in High-mass X-Ray Binaries?

Magnetars form a special population of neutron stars with strong magnetic fields and long spin periods. About 30 magnetars and magnetar candidates known currently are probably isolated, but the possibility that magnetars are in binaries has not been excluded. In this work, we perform spin evolution of neutron stars with different magnetic fields in wind-fed high-mass X-ray binaries and compare the spin period distribution with observations, aiming to find magnetars in binaries. Our simulation shows that some of the neutron stars, which have long spin periods or are in widely-separated systems, need strong magnetic fields to explain their spin evolution. This implies that there are probably magnetars in high-mass X-ray binaries. Moreover, this can further provide a theoretical basis for some unclear astronomical phenomena, such as the possible origin of periodic fast radio bursts from magnetars in binary systems.

恒星级黑洞的搜寻与研究进展

迄今为止,银河系内发现的约20颗恒星级黑洞都是通过黑洞吸积伴星物质所发出的X射线来识别.若黑洞的X射线辐射低于望远镜探测极限,人们仍可以通过监测伴星的视向运动来发现黑洞.我们利用LAMOST望远镜对银河系的一颗B型恒星进行速度测量,发现它在围绕一颗不可见天体——大质量恒星级黑洞做周期性运动.这是国际上利用视向速度监测发现黑洞的一次成功实践.尽管引力波探测实验已经发现相似质量的恒星级黑洞,但在富金属环境中形成如此大质量的黑洞对目前的恒星演化理论形成了巨大的挑战.本文介绍了恒星级黑洞的几种探测方法,并对近些年国内外搜寻黑洞所做的努力进行了回顾,最后对未来利用视向速度监测方法和天体测量方法寻找黑洞进行了展望.

Emerging technologies in Si active photonics

Silicon photonics for synergistic electronic-photonic integration has achieved remarkable progress in the past two decades. Active photonic devices, including lasers, modulators, and photodetectors, are the key chal- lenges for Si photonics to meet the requirement of high bandwidth and low power consumption in photonic datalinks. Here we review recent efforts and progress in high-performance active photonic devices on Si, focusing on emerging technologies beyond conventional foundry-ready Si photonics devices. For emerging laser sources, we will discuss recent progress towards efficient monolithic Ge lasers, mid-infrared GeSn lasers, and high-per- formance InAs quantum dot lasers on Si for data center applications in the near future. We will then review novel modulator materials and devices beyond the free carrier plasma dispersion effect in Si, including GeSi and graphene electro-absorption modulators and plasmonic-organic electro-optical modulators, to achieve ultralow power and high speed modulation. Finally, we discuss emerging photodetectors beyond epitaxial Ge p-i-n photo- diodes, including GeSn mid-infrared photodetectors, all-Si plasmonic Schottky infrared photodetectors, and Si quanta image sensors for non-avalanche, low noise single photon detection and photon counting. These emerging technologies, though still under development, could make a significant impact on the future of large-scale electron- icSilicon photonics for synergistic electronic-photonic integration has achieved remarkable progress in the past two decades. Active photonic devices, including lasers, modulators, and photodetectors, are the key challenges for Si photonics to meet the requirement of high bandwidth and low power consumption in photonic datalinks. Here we review recent efforts and progress in high-performance active photonic devices on Si, focusing on emerging tech- nologies beyond conventional foundry-ready Si photonics devices. For emerging laser sources, we will discuss re- cent progress towards efficient monolithic Ge lasers, mid-infrared GeSn lasers, and high-performance InAs quantum dot lasers on Si for data center applications in the near future. We will then review novel modulator ma- terials and devices beyond the free carrier plasma dispersion effect in Si, including GeSi and graphene electro-ab- sorption modulators and plasmonic-organic electro-optical modulators, to achieve ultralow power and high speed modulation. Finally, we discuss emerging photodetectors beyond epitaxial Ge p-i-n photodiodes, including GeSn mid-infrared photodetectors, all-Si plasmonic Schottky infrared photodetectors, and Si quanta image sensors for non-avalanche, low noise single photon detection and photon counting. These emerging technologies, though still under development, could make a significant impact on the future of large-scale electronic-photonic integration with performance inaccessible from conventional Si photonics technologies-photonic integration with perform- ance inaccessible from conventional Si photonics technologies.

马来西亚诗巫市华人的历史文化记忆与日常文化实践

20世纪80年代以来,马来西亚诗巫华人致力创建回忆空间,兴建纪念场所、经营文化团体、庆祝各类节日,让回忆成为日常文化实践。他们以此方式来阐释自己的历史,丰富族群记忆,传承华人文化。华社整体性历史叙述的形成,伴随着乡属群体间的竞争,背后是华社内部不均衡的权力关系。在这个过程中,华人的祖籍地意识得到强化,与祖籍地的联系得以加强。华社在叙述先辈筚路蓝缕的经历时,并不只是突出移民历史,同样强调已扎根当地的华族意识。他们积极描绘与原住民的合作交流,其目的不仅是竭力营造和谐共处的族群关系,更是强调华族与原住民一样,应得到国家的公平对待。通过兼顾这两个方面,当地华人重塑了早期移民历史,强化了作为马来西亚族群之一的华族意识。

Overview of the LAMOST survey in the first decade

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST),also known as the Guoshoujing Telescope,is a major national scientific facility for astronomical research located in Xinglong,China.Beginning with a pilot survey in 2011,LAMOST has been surveying the night sky for more than 10 years.The LAMOST survey covers various objects in the Universe,from normal stars to peculiar ones.

Sesquiterpenoids of Ilficiumjiadifengpi and Their Effects on NGF-induced Neurite Outgrowth in PC12 Cells

Two new compounds, jiadifenlactone acid monomethyl ester （1） and jiadifenin （3）, and five known compounds were isolated from the fruits of I. jiadifengpi. Their structures were determined using spectroscopic techniques, in- cluding 1D, 2D NMR and HR-ESI-MS experiments. The relative stereochemistry ofjiadifenlactone acid monome- theyl ester （1） was further confirmed by X-ray crystallographic data. All isolates were evaluated for their effects on nerve growth factor （NGF）-mediated neurite outgrowth in pheochromocytoma （PC12） cells and two compounds showed promoting effects.

Repeating fast radio bursts: Coherent circular polarization by bunches

Fast radio bursts(FRBs) are millisecond-duration signals that are highly dispersed at distant galaxies. However, the physical origin of FRBs is still unknown. Coherent curvature emission by bunches, e.g., powered by starquakes, has already been proposed for repeating FRBs. It has the nature of understanding narrowband radiation exhibiting time-frequency drifting. Recently, a highly active FRB source, i.e., FRB 20201124A, was reported to enter a newly active episode and emit at least some highly circular-polarized bursts. In this study, we revisit the polarized FRB emission, particularly investigating the production mechanisms of a highly circular polarization(CP) by deriving the intrinsic mechanism and propagative effect. The intrinsic mechanisms of invoking charged bunches are approached with radiative coherence. Consequently, a highly CP could naturally be explained by the coherent summation of outcome waves, generated or scattered by bunches, with different phases and electric vectors. Different kinds of evolutionary trajectories are found on the Poincaré sphere for the bunch-coherent polarization, and this behavior could be tested through future observations. Cyclotron resonance can result in the absorption of R-mode photons at a low altitude region of the magnetosphere, and an FRB should then be emitted from a high-altitude region if the waves have strong linear polarization. Circularly polarized components could be produced from Faraday conversion exhibiting a λ-oscillation, but the average CP fraction depends only on the income wave, indicating a possibility of a highly circular-polarized income wave. The analysis could be welcome if extremely high(e.g., almost 100%) CP from repeating FRBs is detected in the future. Finally, the production of a bulk of energetic bunches in the pulsar-like magnetosphere is discussed, which is relevant to the nature of the FRB central engine.

An optical slot-antenna-coupled cavity (SAC) framework towards tunable free-space graphene photonic surfaces

The optical conductivity of single layer graphene (SLG) can be significantly and reversibly modified when the Fermi level is tuned by electrical gating. However, so far this interesting property has rarely been applied to free-space two-dimensional (2D) photonic devices because the surface-incident absolute absorption of SLG is limited to 1%–2%. No significant change in either reflectance or transmittance would be observed even if SLG is made transparent upon gating. To achieve significantly enhanced surface-incident optical absorption in SLG in a device structure that also allows gating, here we embed SLG in an optical slot-antenna-coupled cavity (SAC) framework, simultaneously enhancing SLG absorption by up to 20 times and potentially enabling electrical gating of SLG as a step towards tunable 2D photonic surfaces. This framework synergistically integrates near-field enhancement induced by ultrahigh refractive index semimetal slot-antenna with broadband resonances in visible and infrared regimes, ~ 3 times more effective than a vertical cavity structure alone. An example of this framework consists of self-assembled, close-packed Sn nanodots separated by ~ 10 nm nanogaps on a SLG/SiO2/Al stack, which dramatically increases SLG optical absorption to 10%-25% at λ = 600–1,900 nm. The enhanced SLG absorption spectrum can also be controlled by the insulator thickness. For example, SLG embedded in this framework with a 150 nm-thick SiO2 insulating layer displays a distinctive red color in contrast to its surrounding regions without SLG on the same sample under white light illumination. This opens a potential path towards gate-tunable spectral reflectors. Overall, this work initiates a new approach towards tunable 2D photonic surfaces.

Numerical simulation and experiment of medium flow energy field in vibrating mill

In order to solve to the technical bottleneck that powder is easy to reunite and without refining in the vibration ultrafine grinding(UFG)technology,the energy field of medium flow was studied by analyzing crushing energy and energy transfer.The numerical simulation model of medium flow based on Particle Flow Code(PFC)was established.By setting four kinds of working conditions of amplitude and frequency,the dynamic graphics and curves of the energy field(such as kinetic energy,strain energy,velocity field,force chain and so on)were obtained.In the situation of mid-frequency with large amplitude,the average speed of front medium flow was 1.3–5.03 times that of others and the low-energy region was decreased by 6%to 10%.The largest kinetic energy and strain energy were 3.25 and 2.94 times the average value of others,respectively.The diamond UFG was analyzed in new vibration mills under the conditions of low frequency with large amplitude and mid-frequency with large amplitude.Utilizing a laser particle size analyzer,it was discovered that the particle sizes d(50)in these two models were 3.840µm and 0.260µm and bandwidths were 9.940µm and 3.825µm.This highlights the effect of mid-frequency with large amplitude in particle refining and bandwidth narrowing,which is of great importance in the fields of ultra-hard particle refining research and energy utilization.

Single-cell sequencing and bulk RNA sequencing reveal a cell differentiation-related multigene panel to predict the prognosis and immunotherapy response of hepatocellular carcinoma

To the Editor:Hepatocellular carcinoma(HCC)is the sixth most common tumor and the third leading cause of cancer death globally in 2020.[1]The lack of early diagnosis and high intratumoral heterogeneity in HCC are important reasons for its high mortality.Genetic susceptibility and environmental stimuli lead to a tumor mass consisting of mixed tumor cells with different differentiation characteristics.Thus,intratumoral heterogeneity is the inevitable product of the differentiation of tumor stem cells.[2]

The nearest neutron star candidate in a binary revealed by optical time-domain surveys

The near-Earth(within~100 pc)supernova explosions in the past several million years can cause the global deposition of radioactive elements(e.g.,60Fe)on Earth.The remnants of such supernovae are too old to be easily identified.It is therefore of great interest to search for million-year-old near-Earth neutron stars or black holes,the products of supernovae.However,neutron stars and black holes are challenging to find even in our Solar neighbourhood if they are not radio pulsars or X-ray/γ-ray emitters.Here we report the discovery of one of the nearest(127.7±0.3 pc)neutron star candidates in a detached single-lined spectroscopic binary LAMOST J235456.73+335625.9(hereafter J2354).Utilizing the time-resolved ground-based spectroscopy and space photometry,we find that J2354 hosts an unseen compact object with M_(inv)being 1.4-1.6 M_(⊙).The follow-up Swift ultraviolet(UV)and X-ray observations suggest that the UV and X-ray emission is produced by the visible star rather than the compact object.Hence,J2354 probably harbours a neutron star rather than a hot ultramassive white dwarf.Two-hour exceptionally sensitive radio follow-up observations with Five-hundred-meter Aperture Spherical radio Telescope fail to reveal any pulsating radio signals at the 6σflux upper limit of 12.5μJy.Therefore,the neutron star candidate in J2354 can only be revealed via our time-resolved observations.Interestingly,the distance between J2354 and our Earth can be as close as~50 pc around 2.5 million years(Myrs)ago,as revealed by the Gaia kinematics.Our discovery demonstrates a promising way to unveil the hidden near-Earth neutron stars in binaries by exploring the optical time domain,thereby facilitating understanding of the metal-enrichment history in our Solar neighbourhood.

Dynamic numerical simulation on grinding medium flow field for vibration mill under various vibrating amplitude–frequency combination conditions

People gained limited progress on refinement of super-hard powder using the vibration mill for many years.According to various amplitude–frequency combination working conditions of vibration mill prototype,simulation research on dynamic characteristic of grinding medium flow field based on PFC is proposed in the paper,and a dynamics model of grinding medium flow field in barrel is established.Furthermore,trajectory image of medium flow,kinetic energy and strain energy and collision frequency can be obtained.The simulation analysis shows that collision between media as well as between media and the barrel can cause the changes of kinetic energy and strain energy of grinding medium flow under various amplitude–frequency combination conditions,and an energy-lacking region exists in the barrel.Contrast experiments under various working conditions show that kinetic energy and strain energy of grinding medium flow have large increment and energy-lacking regions become smaller,and then energy consumption decreases on working condition of high-amplitude and middle-frequency.The conclusion has practical value to refine powder by high-intensity vibration mill with certain frequency.

Electrically injected GeSn lasers with peak wavelength up to 2.7 μm

GeSn lasers enable the monolithic integration of lasers on the Si platform using all-group-Ⅳ direct-bandgap material.The GeSn laser study recently moved from optical pumping into electrical injection.In this work,we present explorative investigations of GeSn heterostructure laser diodes with various layer thicknesses and material compositions.Cap layer material was studied by using Si_(0.03)Ge_(0.89)Sn_(0.08) and Ge_(0.95)Sn_(0.05),and cap layer total thickness was also compared.The 190 nm SiGeSn-cap device had threshold of 0.6 kA/cm^(2) at 10 K and a maximum operating temperature(T_(max)) of 100 K,compared to 1.4 kA/cm^(2) and 50 K from 150 nm SiGeSn-cap device,respectively.Furthermore,the 220 nm GeSn-cap device had 10 K threshold at 2.4 kA/cm^(2) and T_(max) at 90 K,i.e.,higher threshold and lower maximal operation temperature compared to the SiGeSn cap layer,indicating that enhanced electron confinement using SiGeSn can reduce the threshold considerably.The study of the active region material showed that device gain region using Ge_(0.87)Sn_(0.13) had a higher threshold and lower T_(max),compared to Ge_(0.89)Sn_(0.11).The performance was affected by the metal absorption,free carrier absorption,and possibly defect density level.The maximum peak wavelength was measured as 2682 nm at 90 K by using Ge_(0.87)Sn_(0.13) in gain regions.The investigations provide directions to the future GeSn laser diode designs toward the full integration of group-Ⅳ photonics on a Si platform.

The sequence-dependent morphology of self-assembly peptides after binding with organophosphorus nerve agent VX

VX is a highly toxic organophosphorus nerve agent that the Chemical Weapons Convention classifies as a Schedule 1. In our previous study, we developed a method for detecting organophosphorus compounds using peptide self-assembly. Nevertheless, the self-assembly mechanisms of peptides that bind organophosphorus and the roles of each peptide residue remain elusive, restricting the design and application of peptide materials. Here, we use a multi-scale computational combined with experimental approach to illustrate the self-assembly mechanism of peptide-bound VX and the roles played by residues in different peptide sequences. We calculated that the self-assembly of peptides was accelerated after adding VX, and the final size of assembled nanofibers was larger than the original one, aligning with experimental findings. The atomic scale details offered by our approach enabled us to clarify the connection between the peptide sequences and nanostructures formation, as well as the contribution of various residues in binding VX and assembly process. Our investigation revealed a tight correlation between the number of Tyrosine residues and morphology of the assembly. These results indicate a self-assembly mechanism of peptide and VX, which can be used to design functional peptides for binding and hydrolyzing other organophosphorus nerve agents for detoxification and biomedical applications.