【导读】中国现代天文学摇篮

中国科学院紫金山天文台前身是成立于1928年的国立中央研究院天文研究所,1950年更为现名,是我国自主建立的第一个现代天文学研究机构。紫金山天文台的建成标志着中国现代天文学研究的开始,被誉为“中国现代天文学摇篮”。从1913年高鲁先生下决心建造一座中国人自己的现代化天文台,到1934年余青松先生在紫金山上的天堡峰实现高鲁先生的宏愿,再到新中国成立后张钰哲先生站在中国天文事业全局发展的高度制定规划并推动形成了当前中国科学院和部分高校天文研究机构以及部分天文科普教育基地的分布格局,一代又一代紫金山天文台科技工作者严谨求实,勤奋开拓,不辱使命,为我国天文学事业的发展,为国家经济建设和航天事业的腾飞做出了重要的积极贡献。

An Intermediate-field Fast Radio Burst Model and the Quasi-periodic Oscillation

Quasi-periodic oscillation(QPO)signals are discovered in some fast radio bursts(FRBs)such as FRB 20191221A,as well as in the X-ray burst associated with the galactic FRB from SGR 1935+2154.We revisit the intermediatefield FRB model where the radio waves are generated as fast-magnetosonic waves through magnetic reconnection near the light cylinder.The current sheet in the magnetar wind is compressed by a low frequency pulse emitted from the inner magnetosphere to trigger magnetic reconnection.By incorporating the wave dynamics of the magnetosphere,we demonstrate how the FRB frequency,the single pulse width,and luminosity are determined by the period,magnetic field,QPO frequency and quake energetics of the magnetar.We find that this model can naturally and self-consistently interpret the X-ray/radio event from SGR 1935+2154 and the QPO in FRB20191221A.It can also explain the observed wide energy range of repeating FRBs in a narrow bandwidth.

Surface Cu^(+) modified ZnIn_(2)S_(4) for promoted visible-light photocatalytic hydrogen evolution

Surface modification by metal ion has been considered a promising strategy to enhance the photocatalytic activity by extending optical response and improving charge separation and transportation.Here,univalent copper species were modified on ZnIn_(2)S_(4)photocatalyst via an in-situ photodeposition method,exhibiting a much higher H2evolution rate of 41.10±3.43 mmol g^(-1)h^(-1)and an impressive apparent quantum efficiency(AQE)of 20.81%at 420±15 nm.Our characterizations indicate that the surface modification by copper species can broaden light utilization as well as promote charge separation and transportation.Besides,the density functional theory(DFT)results further exhibit that the energy levels(LUMO and HOMO)for copper-surface modified ZnIn_(2)S_(4)present spatial separation,locating on the Zn-S and In-S layers,respectively,which can suppress the recombination of electron and hole and thus achieves higher photocatalytic H2evolution efficiency.

Science with the 2.5-meter Wide Field Survey Telescope(WFST)

The Wide Field Survey Telescope(WFST) is a dedicated photometric surveying facility being built jointly by University of Science and Technology of China(USTC) and the Purple Mountain Observatory(PMO). It is equipped with a 2.5-meter diameter primary mirror, an active optics system, and a mosaic CCD camera with 0.73 gigapixels on the primary focal plane for highquality image capture over a 6.5-square-degree field of view. The installation of WFST near the summit of Saishiteng mountain in the Lenghu region is scheduled in summer of 2023, and the operation is planned to start three months later. WFST will scan the northern sky in four optical bands(u, g, r and i) at cadences from hourly/daily in the deep high-cadence survey(DHS) program, to semi-weekly in the wide field survey(WFS) program. During a photometric night, a nominal 30 s exposure in the WFS program will reach a depth of 22.27, 23.32, 22.84, and 22.31(AB magnitudes) in these four bands, respectively, allowing for the detection of a tremendous amount of transients in the low-z universe and a systematic investigation of the variability of Galactic and extragalactic objects. In the DHS program, intranight 90 s exposures as deep as 23(u) and 24 mag(g), in combination with target of opportunity follow-ups, will provide a unique opportunity to explore energetic transients in demand for high sensitivities, including the electromagnetic counterparts of gravitational wave events, supernovae within a few hours of their explosions,tidal disruption events and fast, luminous optical transients even beyond redshift of unity. In addition, the final 6-year co-added images, anticipated to reach g■25.8 mag in WFS or 1.5 mags deeper in DHS, will be of fundamental importance to general Galactic and extragalactic science. The highly uniform legacy surveys of WFST will serve as an indispensable complement to those of the Vera C. Rubin Observatory's Legacy Survey of Space and Time(LSST) that monitors the southern sky.

Simultaneously Enhanced Thermal and Mechanical Properties of ZK60 Alloy Reinforced by Oriented Graphene Nanoplatelets

The lamellar and orientational characteristics of graphene nanoplatelets(GNPs)are crucial for reinforcing metal matrix composites,particularly in terms of their thermal properties.Two kinds of GNPs with plane sizes of 6µm and 80µm were respectively used as reinforcements in ZK60 alloy by powder metallurgy.The oriented distribution of GNPs in the matrix was obtained using a double-pass hot extrusion process,i.e.,a stepped extrusion with two consecutive extrusion ratios(10:1 and 16:1).Reinforced with 0.05 wt%oriented GNPs(80µm),the composite exhibited a tensile yield strength of 257 MPa,ultimate tensile strength of 342 MPa,elongation of 24.7%,and notably enhanced thermal conductivity of 128.3 W(mK)−1 even with refined grain size compared to the ZK60 alloy.The oriented GNPs in the matrix create a favorable path for efficient load and heat transfer,leading to the simultaneously enhancement of mechanical and thermal properties of the GNPs/ZK60 composites.This work is expected to broaden the application potential of GNPs as highly efficient reinforcements and provide a practical method for fabricating metal matrix composites.

Optical observations of LIGO source GW 170817 by the Antarctic Survey Telescopes at Dome A,Antarctica

The LIGO detection of gravitational waves(GW) from merging black holes in 2015 marked the beginning of a new era in observational astronomy. The detection of an electromagnetic signal from a GW source is the critical next step to explore in detail the physics involved. The Antarctic Survey Telescopes(AST3),located at Dome A, Antarctica, is uniquely situated for rapid response time-domain astronomy with its continuous night-time coverage during the austral winter. We report optical observations of the GW source(GW 170817) in the nearby galaxy NGC 4993 using AST3. The data show a rapidly fading transient at around 1 day after the GW trigger, with the i-band magnitude declining from 17:23 ± 0:13 magnitude to 17:72 ± 0:09 magnitude in ~1:8 h. The brightness and time evolution of the optical transient associated with GW 170817 are broadly consistent with the predictions of models involving merging binary neutron stars. We infer from our data that the merging process ejected about ~10^(-2) solar mass of radioactive material at a speed of up to 30% the speed of light.

Loss of hnRNP A1 in murine skeletal muscle exacerbates high-fat diet-induced onset of insulin resistance and hepatic steatosis

Impairment of glucose(Glu)uptake and storage by skeletal muscle is a prime risk factor for the development of metabolic diseases.Heterogeneous nuclear ribonucleoprotein A1(hnRNP Al)is a highly abundant RNA-binding protein that has been implicated in diverse cellular functions.The aim of this study was to investigate the function of hnRNP A1 on muscle tissue insulin sensitivity and systemic Glu homeostasis.Our results showed that conditional deletion of hnRNP Al in the muscle gave rise to a severe insulin resistance phenotype in mice fed a high-fat diet(HFD).Conditional knockout mice fed a HFD showed exacerbated obesity,insulin resistance,and hepatic steatosis.In vitro interference of hnRNP Al in C2C12 myotubes impaired insulin signal transduction and inhibited Glu uptake,whereas hnRNP Al overexpression in C2C12 myotubes protected against insulin resistance induced by supraphysiological concentrations of insulin.The expression and stability of glycogen synthase(gysl)mRNA were also decreased in the absence of hnRNP A l.Mechanistically,hnRNP Al interacted with gys l and stabilized its mRNA,thereby promoting glycogen synthesis and maintaining the insulin sensitivity in muscle tissue.Taken together,our findings are the first to show that reduced expression of hnRNP Al in skeletal muscle affects the metabolic properties and systemic insulin sensitivity by inhibiting glycogen synthesis.

Observatory science with eXTP

In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.

Hydrophobic 1-octadecanethiol functionalized copper catalyst promotes robust high-current CO_(2) gas-diffusion electrolysis

The electrocatalytic reduction of CO_(2) presents a promising strategy in addressing environmental and energy crisis.Significant progress has been achieved via CO_(2) gas diffusion electrolysis,to react at high selectivity and high rate.However,the gas diffusion layer(GDL)of the gas diffusion electrode(GDE)still suffers from low tolerance and limited active sites.Here,the hydrophobic 1-octadecanethiol molecular was functionalized over the Cu catalyst layer of the GDE,which simultaneously stabilizes the GDL and exposes abundant active solid-liquid-gas three-phase interfaces.The resultant GDE exhibits multi-carbon(C_(2+))product selectivity over faradaic efficiency(FE)of 70.0%in the range of 100 to 800 mA·cm^(-2),with the peak FE^(c2+)of 85.2%at 800 mA·cm^(-2).Notably,the strengthened GDE could continuously drive high-current electrolysis for more than 100 h without flooding.This work opens a new way to improve CO_(2) gas diffusion electrolysis via surface molecular engineering.

Regulation of antiviral innate immunity by deubiquitinase CYLD

An antiviral innate immune response involves induction of type I interferons(IFNs)and their subsequent autocrine and paracrine actions,but the underlying regulatory mechanisms are incompletely understood.Here we report that CYLD,a deubiquitinase that specifically digests lysine 63-linked ubiquitin chains,is required for antiviral host defense.Loss of CYLD renders mice considerably more susceptible to infection by vesicular stomatitis virus(VSV).Consistently,CYLD-deficient dendritic cells are more sensitive to VSV infection.This functional defect was not due to lack of type I IFN production but rather because of attenuated IFN receptor signaling.In the absence of CYLD,IFN-b is ineffective in the induction of antiviral genes and protection of cells from viral infection.These findings establish CYLD as a novel regulator of antiviral innate immunity and suggest a role for CYLD in regulating IFN receptor signaling.

MIL-125(Ti)中引入高价态钨元素以促进光催化产氢性能

金属有机框架(Metal-organic frameworks, MOFs)材料具有高度可调控的多孔结构以及电子结构,在光催化领域非常有前景.本文利用MOFs的上述特性,将高价态的钨元素连接在MIL-125(Ti)中的Ti-oxo团簇上,得到了W-MIL-125.形成的W–O–Ti结构引发了从金属到团簇的电荷传输(Metal-to-cluster charge transfer, MCCT),且W-MIL-125具有更好的吸光性能.结构和谱学表征证明, MCCT过程能优化电荷的传输路径,有效地实现了载流子空间分离. W-MIL-125在光照条件下展现出更高的产氢性能,高达1110.7±63.7μmol g^(-1)h^(-1),是本体样品产氢速率的4.0倍.本工作为MOFs基材料的局域结构改性以提升光催化性能提供了新的思路.

Bandgap opening in MoTe2 thin flakes induced by surface oxidation

Recently,the layered transition metal dichalcogenide 1T′-MoTe2 has generated considerable interest due to their superconducting and non-trivial topological properties.Here,we present a systematic study on 1T′-MoTe2 single-crystal and exfoliated thin-flakes by means of electrical transport,scanning tunnelling microscope(STM)measurements and band structure calculations.For a bulk sample,it exhibits large magneto-resistance(MR)and Shubnikov–de Hass oscillations inρxx and a series of Hall plateaus inρxy at low temperatures.Meanwhile,the MoTe2 thin films were intensively investigated with thickness dependence.For samples,without encapsulation,an apparent transition from the intrinsic metallic to insulating state is observed by reducing thickness.In such thin films,we also observed a suppression of the MR and weak anti-localization(WAL)effects.We attributed these effects to disorders originated from the extrinsic surface chemical reaction,which is consistent with the density functional theory(DFT)calculations and in-situ STM results.In contrast to samples without encapsulated protection,we discovered an interesting superconducting transition for those samples with hexagonal Boron Nitride(h-BN)film protection.Our results indicate that the metallic or superconducting behavior is its intrinsic state,and the insulating behavior is likely caused by surface oxidation in few layer 1T’-MoTe2 flakes.

Ultrathin Hematite Photoanode with Gradient Ti Doping

The poor photoelectrochemical(PEC)performance derived from insufficient charge separation in hematite photoanode crucially limits its application.Gradient doping with band bending in a large region is then considered as a promising strategy,facilitating the charge transfer ability due to the built-in electric field.Herein,we developed a synthetic strategy to prepare gradient Ti-doped ultrathin hematite photoelectrode and systematically investigated its PEC performance.The as-synthesized electrode(1.5-6.0%doping level from the surface to the substrate)delivered a photocurrent of about 1.30mAcm^(-2) at 1.23V versus the reversible hydrogen electrode(RHE),which is nearly 100%higher than that of homogeneously doped hematite electrode.The enhanced charge transfer property,induced by the energy band bending due to the built-in electric field,has been further confirmed by electrochemical measurements.This strategy of gradient doping should be adaptable and can be applied for other functional materials in various fields.