光电振荡器是一种能够稳定产生自激振荡的微波光子共振系统,近年来得到了广泛的研究,工作频率达到数百GHz,相位噪声性能达到-163 dBc/Hz at 6 kHz,调谐范围达到数十千兆赫兹。文章回顾了光电振荡器问世以来的部分研究进展和重要应用,重...光电振荡器是一种能够稳定产生自激振荡的微波光子共振系统,近年来得到了广泛的研究,工作频率达到数百GHz,相位噪声性能达到-163 dBc/Hz at 6 kHz,调谐范围达到数十千兆赫兹。文章回顾了光电振荡器问世以来的部分研究进展和重要应用,重点介绍了近年来集成化光电振荡器的研究现状,并提出了一种可应用于集成化光电振荡器的新型电光晶体材料。展开更多
The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling....The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling.Scanning electron microscopy with electron-backscatter diffraction was used to monitor the development of the microstructure in the differently deformed and additionally annealed samples.Details of the formations and transformations of individual texture components occurring during the rolling processes were observed and discussed.The average grain sizes,textures and mechanical properties were correlated and explained for the symmetric and asymmetric cold-rolled samples.The asymmetric rolling is beneficial in terms of deep drawability because it reduces the planar anisotropy of the annealed material due to the decrease of the Cube,Goss,rotated-Cube and η-fibre texture components and at the same time strengthens X1-and X2-fibre texture components which are shear texture components and improve deep drawability.During the asymmetric cold rolling,the temperature increases due to friction,triggering recrystallisation processes and leading to larger grains.It is also confirmed that asymmetric cold rolling uses less rolling force and consequently less energy to produce a final material with better formability,particularly earing.展开更多
In a typical sintered multi-component Sm_(2)Co_(17)-type magnet with strong fiber texture,we show that the distributions of grain boundary precipitates(GBPs)are heavily dependent on the grain boundary(GB)geometry with...In a typical sintered multi-component Sm_(2)Co_(17)-type magnet with strong fiber texture,we show that the distributions of grain boundary precipitates(GBPs)are heavily dependent on the grain boundary(GB)geometry with respect to the texture direction,which has significant effects on domain wall pinning.Re-sults demonstrate that the continuous GBPs turn into discrete upon the angle between{0001}planes and GB increases from 0°to 90°,meanwhile the GBPs thickness and precipitation free zones(PFZs)width both increase linearly by a factor of 2.5-4.Transmission electron microscopy(TEM)reveals that the GBPs are alternatively stacked Cu-rich SmCo_(5)and Zr-rich Sm_(n+1)Co_(5n-1)(n=2,3,4)compounds,while the PFZs are composed of 2:17R and intermediate 2:17R’phases.Atomic-level elemental mappings and first-principles calculations indicate that Cu exists at the Co-2c site in the SmCo_(5)forming SmCo_(3)Cu_(2)and Zr locates at the dumbbell Sm-6c sites in the Sm_(n+1)Co_(5n-1).The symbiotic GBPs have orientation relationships of[0001]GBPs//[0001]2:17R and[1010]GBPs//[2110]2:17R.The formation of anisotropic GBPs is owing to the strong fiber texture,i.e.,the larger angle between{0001}planes and GBs,the more{0001}diffusion channels for atoms to GBs,resulting in discrete and thick GBPs.In-situ Lorentz TEM shows that the domain walls interrupted by GBPs migrate easily under applied magnetic fields.Possible approaches to enhance the magnetic hardness via tuning the GBs are proposed.展开更多
Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past decade.To understand their emergent quantum phenomena,high-quality single crystals of substantial size are ess...Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past decade.To understand their emergent quantum phenomena,high-quality single crystals of substantial size are essential.Here,we report the synthesis of single crystals of the Kitaev quantum spin liquid candidate RuBr_(3),achieving millimeter-sized crystals through a self-flux method under high pressure and high temperature conditions.The crystals exhibit well-defined cleavage planes with a lustrous appearance.Transport characterizations exhibit a narrow band-gap semiconducting behavior with 0.13 eV and 0.11 eV band-gap in ab plane and along𝑐axis,respectively.Magnetic measurement shows a transition to antiferromagnetic(AFM)state at approximately 29K both in ab plane and along the c axis.Notably,the N′eel temperature increases to 34K with an applied magnetic field of up to 7T in the ab plane,but without any change along𝑐axis.The large size and high quality of RuBr3 single crystals provide a valuable platform for investigating various interactions,particularly the Kitaev interaction,and for elucidating the intrinsic physical properties of Kitaev quantum spin liquids.展开更多
An active galactic nucleus(AGN)plays a crucial role in the evolution of its host galaxy,but the detailed mechanism remains ambiguous.The radiation from the AGN heats and ionizes the surrounding gas in the host galaxy,...An active galactic nucleus(AGN)plays a crucial role in the evolution of its host galaxy,but the detailed mechanism remains ambiguous.The radiation from the AGN heats and ionizes the surrounding gas in the host galaxy,creating a spatially extended narrow line region(NLR).Theoretically,the size of the NLR depends on the ionizing power of the AGN,making it a powerful tool to quantify the influence of the AGN on the host galaxy.To verify the relation between NLR and the central AGN,we collect a large sample of AGNs from the Mapping Nearby Galaxies at Apache Point Observatory,using the BPT diagnostic diagram of[OⅢ]λ5007/Hβand[NⅡ]λ6584/Hα.We have measured the sizes of NLRs with the surface brightness threshold of10^(-16)erg s^(-1)cm^(-2)arcsec^(-2),and find a log-linear relation between their sizes and[OⅢ]λ5007 luminosity with a slope of 0.470±0.025.This result is consistent with the predictions of the standard photoionization model.展开更多
Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming inter...Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming interstellar medium(ISM)has relied on heuristic sub-grid models.However,recent high-resolution simulations of the ISM that directly resolve the regulation of star formation suggest different mean relations for the dependences of pressure and star formation rate on the average gas density.In this study,we adopt such a modern,physically grounded parameterization inspired by the TIGRESS small-scale simulations.We dub this model TEQS and use it for a detailed comparative analysis of the formation and evolution of a Milky Way-sized galaxy when compared with the widely used TNG model.By employing high-resolution simulations in tall box setups,we first investigate the structural differences expected for these two models when applied to different self-gravitating gas surface densities.Our results indicate that TEQS produces considerably thinner gaseous layers and can be expected to form stellar distributions with smaller scale-height than TNG,especially at higher surface density.To test whether this induces systematic structural differences in cosmological galaxy formation simulations,we carry out zoom-in simulations of 12 galaxies taken from the set of Milky Way-sized galaxies that have been studied in the Auriga project.Comparing results for these galaxies shows that disk galaxies formed with the TEQS model have on average very similar stellar mass but are more concentrated in their central regions and exhibit smaller stellar radii compared to those formed with the TNG model.The differences in the scale-heights of the formed stellar disks are only marginal,however,suggesting that other factors for setting the thickness of the disk are more important than the applied ISM equation-of-state model.Overall,the predicted galaxy structure is quite similar for TNG and TEQS despite significant differences in the employed star formation law,demonstrating that feedback processes are more important in regulating the stellar mass than the precise star formation law itself.展开更多
We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Puls...We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Pulsar Timing Array project.We focus on circular orbits in theμHz GW frequency band between 10^(−7)and 3×10^(−6)Hz.This frequency band is higher than the traditional pulsar timing array band and is less explored.We used the data of the millisecond pulsar PSR J1713+5307 observed between 2019 August and 2021 April.A dense observation campaign was carried out in 2020 September to allow for theμHz band coverage.Our sky-averaged continuous source upper limit at the 95%confidence level at 1μHz is 1.26×10^(−12),while the same limit in the direction of the pulsar is 4.77×10^(−13).展开更多
We present the most comprehensive catalog of 12.2 GHz methanol maser sources within the Milky Way to date,consisting of 45712.2 GHz methanol masers associated with 10856.7 GHz methanol masers,resulting in a detection ...We present the most comprehensive catalog of 12.2 GHz methanol maser sources within the Milky Way to date,consisting of 45712.2 GHz methanol masers associated with 10856.7 GHz methanol masers,resulting in a detection rate of 42%.Distances to these sources are derived from the Bar and Spiral Structure Legacy Survey project Distance Calculator.Our analysis shows that both 6.7 and 12.2 GHz methanol masers are more likely to be excited near galactocentric distances of 5–6 kpc,with the detection rate of 12.2 GHz methanol masers decreasing as the galactocentric distance increases.There are no significant differences in the detection rates of 12.2 GHz masers across the four spiral arms,which consistently range between 40%and 50%.However,the detection rate of12.2 GHz methanol masers tends to be higher in the heads of the spiral arms compared to the tails.Analysis of data from the APEX Telescope Large Area Survey of the Galaxy(ATLASGAL)indicates that the luminosity of6.7 GHz masers peaks at a clump dust temperature of about 30 K,while that of 12.2 GHz masers grows with increasing dust temperature.Clumps associated with 12.2 GHz methanol masers generally have higher dust temperatures,bolometric luminosities,and hydrogen densities than those associated only with 6.7 GHz methanol masers or without either maser.Furthermore,clumps in the HⅡregion stage exhibit a higher detection rate of12.2 GHz masers compared to those in other stages,as indicated by the evolutionary stages derived from the ATLASGAL survey results.展开更多
Significant progress has been made in magnetic and inertial confinement fusion(MCF and ICF)energy development since the achievement of world record parameters on the T3 tokamak in 1968.In MCF,the triple product nτT h...Significant progress has been made in magnetic and inertial confinement fusion(MCF and ICF)energy development since the achievement of world record parameters on the T3 tokamak in 1968.In MCF,the triple product nτT has been elevated from 5×10^(17)m^(-3)·s·keV to 1×10^(21)m^(-3)·s·keV.At the same time,Q=Pfusion/Pheating,has increased from 1×10^(-9)to 0.67,with expectations to exceed 10 in the ITER experiment.In ICF,a Q value of approximately 2.4 was attained with a fusion energy output of around 5.2 MJ.展开更多
We analyze the absorption features in the public 73 ks XMM-Newton spectra of the Seyfert 1 galaxy PG 0052+251.Our analysis reveals the presence of a warm absorber(WA)intrinsic to the source and the hot circumgalactic ...We analyze the absorption features in the public 73 ks XMM-Newton spectra of the Seyfert 1 galaxy PG 0052+251.Our analysis reveals the presence of a warm absorber(WA)intrinsic to the source and the hot circumgalactic medium at zero redshift.The identified WA is inflowing toward the central black hole,with a velocity shift of■.The ionization parameter of the WA is■,showing strong O II and O III absorption lines,along with a significant absorption of the spectral continuum at?10?.The line of sight toward PG 0052+251 intersects the halo of M31 at an impact parameter of approximately 218 kpc.Several local(z~0)absorption lines,like O VII,O VIII,and Ne IX,were detected.The derived hydrogen column density of the local hot gas is 2.2–2.6σhigher than those estimated by several models of the Galactic hot halo,suggesting a likely contribution from the M31 halo.We also find two absorption features at24.305?and 21.410?,which are unlikely to be associated with the hot halos or the warm-hot intergalactic medium but imply the presence of an additional WA component with an outflow velocity of approximately-7000 km s^(-1).展开更多
Fast Radio Bursts(FRBs) are enigmatic millisecond-duration radio transients of extra-galactic origin, whose underlying mechanisms and progenitors remain poorly understood. FRBs are broadly classified into two categori...Fast Radio Bursts(FRBs) are enigmatic millisecond-duration radio transients of extra-galactic origin, whose underlying mechanisms and progenitors remain poorly understood. FRBs are broadly classified into two categories: repeating FRBs, which emit multiple bursts over time, and one-off FRBs, which are detected as single events. A central question in FRB research is whether these two classes share a common origin. In this study, we present observations of FRB 20240114A, a repeating FRB that entered a hyperactive phase in 2024 January. We conducted a 318 hr monitoring campaign using the Kunming 40-Meter Radio Telescope(KM40M) in the S-band(2.187–2.311 GHz), during which we detected eight radio bursts. We analyzed their properties, including dispersion measure, bandwidth, pulse width, flux, fluence, and energy. Additionally, we searched for counterparts in overlapping data from the Five-hundred-meter Aperture Spherical Telescope(FAST) in the L-band(1.0–1.5 GHz). While no bursts were temporally aligned between the two telescopes, we identified one FAST burst that arrived approximately 6 ms after one of the KM40M bursts. The absence of FAST counterparts for the KM40M bursts suggests that individual bursts from FRB 20240114A are likely narrow-band, with fractional bandwidths less than 10%. By comparing the cumulative event rates from KM40M and FAST observations, we found that the two measurements are compatible, indicating a possible flattening of the event rate at higher energies. This feature aligns with observations of one-off FRBs, supporting the hypothesis that repeating and oneoff FRBs may share a common origin.展开更多
Global crop productivity faces a significant threat from climate change-induced drought stress(DS),which is vital for sustainable agriculture and global food security.Uncovering DS adaptation and tolerance mechanisms ...Global crop productivity faces a significant threat from climate change-induced drought stress(DS),which is vital for sustainable agriculture and global food security.Uncovering DS adaptation and tolerance mechanisms in crops is necessary to alleviate climate challenges.Innovative plant breeding demands revolutionary approaches to develop stress-smart plants.Metabolomics,a promising field in plant breeding,offers a predictive tool to identify metabolic markers associated with plant performance under DS,enabling accelerated crop improvement.Central to DS adaptation is metabolomics-driven metabolic regulation,which is critical for maintaining cell osmotic potential in crops.Recent innovations allow rapid mapping of specific metabolites to their genetic pathways,providing a valuable resource for plant scientists.Metabolomics-driven molecular breeding,integrating techniques such as mQTL and mGWAS,enhances our ability to discover key genetic elements linked to stress-responsive metabolites.This integration offers a beneficial platform for plant scientists,yielding significant insights into the complex metabolic networks underlying DS tolerance.Therefore,this review discusses(1)insights into metabolic regulation for DS adaptation,(2)the multifaceted role of metabolites in DS tolerance and nutritional/yield trait improvement,(3)the potential of single-cell metabolomics and imaging,(4)metabolomics-driven molecular breeding,and(5)the application of metabolic and genetic engineering for DS-tolerant crops.We finally propose that the metabolomics-driven approach positions drought-smart crops as key contributors to future food production,supporting the vital goal of achieving“zero hunger”.展开更多
Compared to traditional superhard materials with high electron density and short,strong covalent bonds,alloy materials mainly composed of metallic bonding structures typically have great toughness and lower hardness.B...Compared to traditional superhard materials with high electron density and short,strong covalent bonds,alloy materials mainly composed of metallic bonding structures typically have great toughness and lower hardness.Breaking through the limits of alloy materials is a preface and long-term topic,which is of great significance and value for improving the comprehensive mechanical properties of alloy materials.Here,we report on the discovery of a cubic alloy semiconducting material Ti_(2)Co with a large Vickers of hardness K_(v)^(exp)∼6.7GPa and low fracture toughness of K_(IC)^(exp)∼1.51MPa·m^(1/2).Unexpectedly,the K_(v)^(exp)∼6.7GPa is nearly triple of the K_(v)^(cal)∼2.66GPa predicted by density functional theory(DFT)calculations and theK_(IC)^(exp)∼1.51MPa·m^(1/2)is about one or two orders of magnitude smaller than that of ordinary titanium alloy materials(K_(IC)^(exp)∼30-120MPa·m^(1/2)).These specifications place Ti_(2)Co far from the phase space of the known alloy materials.Upon incorporation of oxygen into structural void positions,both values were simultaneously improved for Ti_(4)Co_(2)O to∼9.7GPa and∼2.19MPa·m^(1/2),respectively.Further DFT calculations on the electron localization function of Ti_(4)Co_(2)X(X=B,C,N,O)vs.the interstitial elements indicate that these simultaneous improvements originate from the coexistence of Ti-Co metallic bonds,the emergence of newly oriented Ti-X covalent bonds,and the increase of electron concentration.Moreover,the large difference between K_(v)^(exp)and K_(v)^(cal)of Ti_(2)Co suggests underlying mechanism concerning the absence of the O(16d)or Ti_(2)-O bonds in the O-(Ti_(2))_(6) octahedron.This discovery proposes a new pathway to simultaneously improve the comprehensive mechanical performances and illuminates the path of exploring superconducting materials with excellent mechanical performances.展开更多
文摘光电振荡器是一种能够稳定产生自激振荡的微波光子共振系统,近年来得到了广泛的研究,工作频率达到数百GHz,相位噪声性能达到-163 dBc/Hz at 6 kHz,调谐范围达到数十千兆赫兹。文章回顾了光电振荡器问世以来的部分研究进展和重要应用,重点介绍了近年来集成化光电振荡器的研究现状,并提出了一种可应用于集成化光电振荡器的新型电光晶体材料。
文摘The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling.Scanning electron microscopy with electron-backscatter diffraction was used to monitor the development of the microstructure in the differently deformed and additionally annealed samples.Details of the formations and transformations of individual texture components occurring during the rolling processes were observed and discussed.The average grain sizes,textures and mechanical properties were correlated and explained for the symmetric and asymmetric cold-rolled samples.The asymmetric rolling is beneficial in terms of deep drawability because it reduces the planar anisotropy of the annealed material due to the decrease of the Cube,Goss,rotated-Cube and η-fibre texture components and at the same time strengthens X1-and X2-fibre texture components which are shear texture components and improve deep drawability.During the asymmetric cold rolling,the temperature increases due to friction,triggering recrystallisation processes and leading to larger grains.It is also confirmed that asymmetric cold rolling uses less rolling force and consequently less energy to produce a final material with better formability,particularly earing.
基金the financial support by the National Nat-ural Science Foundation of China(No.52201032)the Science and Technology Innovation Program of Hunan Province(No.2023RC1013)+2 种基金supported by the Advanced Research Center(for FIB and Talos F200X usages)the State Key Laboratory of Powder Metallurgy(for Spectra 300 usage)the High Performance Computing Center(for supercomputing usage)of Central South University.
文摘In a typical sintered multi-component Sm_(2)Co_(17)-type magnet with strong fiber texture,we show that the distributions of grain boundary precipitates(GBPs)are heavily dependent on the grain boundary(GB)geometry with respect to the texture direction,which has significant effects on domain wall pinning.Re-sults demonstrate that the continuous GBPs turn into discrete upon the angle between{0001}planes and GB increases from 0°to 90°,meanwhile the GBPs thickness and precipitation free zones(PFZs)width both increase linearly by a factor of 2.5-4.Transmission electron microscopy(TEM)reveals that the GBPs are alternatively stacked Cu-rich SmCo_(5)and Zr-rich Sm_(n+1)Co_(5n-1)(n=2,3,4)compounds,while the PFZs are composed of 2:17R and intermediate 2:17R’phases.Atomic-level elemental mappings and first-principles calculations indicate that Cu exists at the Co-2c site in the SmCo_(5)forming SmCo_(3)Cu_(2)and Zr locates at the dumbbell Sm-6c sites in the Sm_(n+1)Co_(5n-1).The symbiotic GBPs have orientation relationships of[0001]GBPs//[0001]2:17R and[1010]GBPs//[2110]2:17R.The formation of anisotropic GBPs is owing to the strong fiber texture,i.e.,the larger angle between{0001}planes and GBs,the more{0001}diffusion channels for atoms to GBs,resulting in discrete and thick GBPs.In-situ Lorentz TEM shows that the domain walls interrupted by GBPs migrate easily under applied magnetic fields.Possible approaches to enhance the magnetic hardness via tuning the GBs are proposed.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFA1406000 and 2022YFA1403800)the National Natural Science Foundation of China(Grant Nos.12474002,22171283,22203031,12434005,12204515,and 12074175)support of the Young Elite Scientists Sponsorship Program by CAST(Grant No.2022QNRC001)。
文摘Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past decade.To understand their emergent quantum phenomena,high-quality single crystals of substantial size are essential.Here,we report the synthesis of single crystals of the Kitaev quantum spin liquid candidate RuBr_(3),achieving millimeter-sized crystals through a self-flux method under high pressure and high temperature conditions.The crystals exhibit well-defined cleavage planes with a lustrous appearance.Transport characterizations exhibit a narrow band-gap semiconducting behavior with 0.13 eV and 0.11 eV band-gap in ab plane and along𝑐axis,respectively.Magnetic measurement shows a transition to antiferromagnetic(AFM)state at approximately 29K both in ab plane and along the c axis.Notably,the N′eel temperature increases to 34K with an applied magnetic field of up to 7T in the ab plane,but without any change along𝑐axis.The large size and high quality of RuBr3 single crystals provide a valuable platform for investigating various interactions,particularly the Kitaev interaction,and for elucidating the intrinsic physical properties of Kitaev quantum spin liquids.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.12192222,12192220 and 12121003)。
文摘An active galactic nucleus(AGN)plays a crucial role in the evolution of its host galaxy,but the detailed mechanism remains ambiguous.The radiation from the AGN heats and ionizes the surrounding gas in the host galaxy,creating a spatially extended narrow line region(NLR).Theoretically,the size of the NLR depends on the ionizing power of the AGN,making it a powerful tool to quantify the influence of the AGN on the host galaxy.To verify the relation between NLR and the central AGN,we collect a large sample of AGNs from the Mapping Nearby Galaxies at Apache Point Observatory,using the BPT diagnostic diagram of[OⅢ]λ5007/Hβand[NⅡ]λ6584/Hα.We have measured the sizes of NLRs with the surface brightness threshold of10^(-16)erg s^(-1)cm^(-2)arcsec^(-2),and find a log-linear relation between their sizes and[OⅢ]λ5007 luminosity with a slope of 0.470±0.025.This result is consistent with the predictions of the standard photoionization model.
基金supported by the National SKA Program of China(grant No.2020SKA0110100)the CAS Project for Young Scientists in Basic Research (No.YSBR-092)the science research grants from the China Manned Space Project with Nos.CMS-CSST-2021-A02 and GHfund C(202407031909)
文摘Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming interstellar medium(ISM)has relied on heuristic sub-grid models.However,recent high-resolution simulations of the ISM that directly resolve the regulation of star formation suggest different mean relations for the dependences of pressure and star formation rate on the average gas density.In this study,we adopt such a modern,physically grounded parameterization inspired by the TIGRESS small-scale simulations.We dub this model TEQS and use it for a detailed comparative analysis of the formation and evolution of a Milky Way-sized galaxy when compared with the widely used TNG model.By employing high-resolution simulations in tall box setups,we first investigate the structural differences expected for these two models when applied to different self-gravitating gas surface densities.Our results indicate that TEQS produces considerably thinner gaseous layers and can be expected to form stellar distributions with smaller scale-height than TNG,especially at higher surface density.To test whether this induces systematic structural differences in cosmological galaxy formation simulations,we carry out zoom-in simulations of 12 galaxies taken from the set of Milky Way-sized galaxies that have been studied in the Auriga project.Comparing results for these galaxies shows that disk galaxies formed with the TEQS model have on average very similar stellar mass but are more concentrated in their central regions and exhibit smaller stellar radii compared to those formed with the TNG model.The differences in the scale-heights of the formed stellar disks are only marginal,however,suggesting that other factors for setting the thickness of the disk are more important than the applied ISM equation-of-state model.Overall,the predicted galaxy structure is quite similar for TNG and TEQS despite significant differences in the employed star formation law,demonstrating that feedback processes are more important in regulating the stellar mass than the precise star formation law itself.
基金supported by the FAST Key projectsupported by the National SKA Program of China (2020SKA0120100)+4 种基金the National Natural Science Foundation of China (NSFC, Grant Nos. 12041303 and 12250410246)the CAS-MPG LEGACY projectfunding from the Max-Planck Partner Groupsupport from the XPLORER PRIZE and 20 yr long-term support from Dr. Guojun Qiaosupported by Major Science and Technology Program of Xinjiang Uygur Autonomous Region No. 2022A03013-4
文摘We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Pulsar Timing Array project.We focus on circular orbits in theμHz GW frequency band between 10^(−7)and 3×10^(−6)Hz.This frequency band is higher than the traditional pulsar timing array band and is less explored.We used the data of the millisecond pulsar PSR J1713+5307 observed between 2019 August and 2021 April.A dense observation campaign was carried out in 2020 September to allow for theμHz band coverage.Our sky-averaged continuous source upper limit at the 95%confidence level at 1μHz is 1.26×10^(−12),while the same limit in the direction of the pulsar is 4.77×10^(−13).
基金supported by the National Key R&D Program of China(2022YFA1603102)the National Natural Science Foundation of China(11873002,12011530065,and 11590781)China Postdoctoral Science Foundation(2023M740803)。
文摘We present the most comprehensive catalog of 12.2 GHz methanol maser sources within the Milky Way to date,consisting of 45712.2 GHz methanol masers associated with 10856.7 GHz methanol masers,resulting in a detection rate of 42%.Distances to these sources are derived from the Bar and Spiral Structure Legacy Survey project Distance Calculator.Our analysis shows that both 6.7 and 12.2 GHz methanol masers are more likely to be excited near galactocentric distances of 5–6 kpc,with the detection rate of 12.2 GHz methanol masers decreasing as the galactocentric distance increases.There are no significant differences in the detection rates of 12.2 GHz masers across the four spiral arms,which consistently range between 40%and 50%.However,the detection rate of12.2 GHz methanol masers tends to be higher in the heads of the spiral arms compared to the tails.Analysis of data from the APEX Telescope Large Area Survey of the Galaxy(ATLASGAL)indicates that the luminosity of6.7 GHz masers peaks at a clump dust temperature of about 30 K,while that of 12.2 GHz masers grows with increasing dust temperature.Clumps associated with 12.2 GHz methanol masers generally have higher dust temperatures,bolometric luminosities,and hydrogen densities than those associated only with 6.7 GHz methanol masers or without either maser.Furthermore,clumps in the HⅡregion stage exhibit a higher detection rate of12.2 GHz masers compared to those in other stages,as indicated by the evolutionary stages derived from the ATLASGAL survey results.
文摘Significant progress has been made in magnetic and inertial confinement fusion(MCF and ICF)energy development since the achievement of world record parameters on the T3 tokamak in 1968.In MCF,the triple product nτT has been elevated from 5×10^(17)m^(-3)·s·keV to 1×10^(21)m^(-3)·s·keV.At the same time,Q=Pfusion/Pheating,has increased from 1×10^(-9)to 0.67,with expectations to exceed 10 in the ITER experiment.In ICF,a Q value of approximately 2.4 was attained with a fusion energy output of around 5.2 MJ.
基金supported by the National Natural Science Foundation of China under Nos.11890692,12133008 and 12221003We acknowledge the science research grant from the China Manned Space Project with No.CMS-CSST-2021-A04.
文摘We analyze the absorption features in the public 73 ks XMM-Newton spectra of the Seyfert 1 galaxy PG 0052+251.Our analysis reveals the presence of a warm absorber(WA)intrinsic to the source and the hot circumgalactic medium at zero redshift.The identified WA is inflowing toward the central black hole,with a velocity shift of■.The ionization parameter of the WA is■,showing strong O II and O III absorption lines,along with a significant absorption of the spectral continuum at?10?.The line of sight toward PG 0052+251 intersects the halo of M31 at an impact parameter of approximately 218 kpc.Several local(z~0)absorption lines,like O VII,O VIII,and Ne IX,were detected.The derived hydrogen column density of the local hot gas is 2.2–2.6σhigher than those estimated by several models of the Galactic hot halo,suggesting a likely contribution from the M31 halo.We also find two absorption features at24.305?and 21.410?,which are unlikely to be associated with the hot halos or the warm-hot intergalactic medium but imply the presence of an additional WA component with an outflow velocity of approximately-7000 km s^(-1).
基金supported by the National SKA Program of China (grant No. 2020SKA0120100)the Special Project of Foreign Science and Technology Cooperation, Yunnan Provincial Science and Technology Department (grant No. 202003AD150010)+4 种基金the National Key R&D Program of China (grant No. 2022YFC2205203)the National Natural Science Foundation of China (NSFC, grant Nos. 12073076, 12173087, 12041303, and 12063003)the CAS “Western Light Youth Project,” Yunnan Fundamental Research Projects (grant Nos. 202401AT070144 and 202505AO120021)funding from the Max-Planck Partner Groupsupport from the XPLORER PRIZE
文摘Fast Radio Bursts(FRBs) are enigmatic millisecond-duration radio transients of extra-galactic origin, whose underlying mechanisms and progenitors remain poorly understood. FRBs are broadly classified into two categories: repeating FRBs, which emit multiple bursts over time, and one-off FRBs, which are detected as single events. A central question in FRB research is whether these two classes share a common origin. In this study, we present observations of FRB 20240114A, a repeating FRB that entered a hyperactive phase in 2024 January. We conducted a 318 hr monitoring campaign using the Kunming 40-Meter Radio Telescope(KM40M) in the S-band(2.187–2.311 GHz), during which we detected eight radio bursts. We analyzed their properties, including dispersion measure, bandwidth, pulse width, flux, fluence, and energy. Additionally, we searched for counterparts in overlapping data from the Five-hundred-meter Aperture Spherical Telescope(FAST) in the L-band(1.0–1.5 GHz). While no bursts were temporally aligned between the two telescopes, we identified one FAST burst that arrived approximately 6 ms after one of the KM40M bursts. The absence of FAST counterparts for the KM40M bursts suggests that individual bursts from FRB 20240114A are likely narrow-band, with fractional bandwidths less than 10%. By comparing the cumulative event rates from KM40M and FAST observations, we found that the two measurements are compatible, indicating a possible flattening of the event rate at higher energies. This feature aligns with observations of one-off FRBs, supporting the hypothesis that repeating and oneoff FRBs may share a common origin.
基金supported by Chinese National Key R&DProject for Synthetic Biology(2018YFA0902500)National Natural Science Foundation of China(32273118)+3 种基金The Guangdong Key R&D Project(2022B1111070005)Shenzhen Special Fund for Sustainable Development(KCXFZ20211020164013021)Shenzhen University 2035 Program for Excellent Research(2022B010)supported by a startup grant from the Food Futures Institute of Murdoch University,Australia.
文摘Global crop productivity faces a significant threat from climate change-induced drought stress(DS),which is vital for sustainable agriculture and global food security.Uncovering DS adaptation and tolerance mechanisms in crops is necessary to alleviate climate challenges.Innovative plant breeding demands revolutionary approaches to develop stress-smart plants.Metabolomics,a promising field in plant breeding,offers a predictive tool to identify metabolic markers associated with plant performance under DS,enabling accelerated crop improvement.Central to DS adaptation is metabolomics-driven metabolic regulation,which is critical for maintaining cell osmotic potential in crops.Recent innovations allow rapid mapping of specific metabolites to their genetic pathways,providing a valuable resource for plant scientists.Metabolomics-driven molecular breeding,integrating techniques such as mQTL and mGWAS,enhances our ability to discover key genetic elements linked to stress-responsive metabolites.This integration offers a beneficial platform for plant scientists,yielding significant insights into the complex metabolic networks underlying DS tolerance.Therefore,this review discusses(1)insights into metabolic regulation for DS adaptation,(2)the multifaceted role of metabolites in DS tolerance and nutritional/yield trait improvement,(3)the potential of single-cell metabolomics and imaging,(4)metabolomics-driven molecular breeding,and(5)the application of metabolic and genetic engineering for DS-tolerant crops.We finally propose that the metabolomics-driven approach positions drought-smart crops as key contributors to future food production,supporting the vital goal of achieving“zero hunger”.
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1408400,2023YFA1406100,2023YFA1607400,2022YFA1403800,and 2022YFA1403203)the National Natural Science Foundation of China(Grant Nos.12474055,12404067,12025408,52025026,and U23A6003)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33000000)the Chinese Academy of Sciences President’s International Fellowship Initiative(Grant No.2024PG0003)the Outstanding Member of Youth Promotion Association of Chinese Academy of Sciences(Grant No.Y2022004)supported by the CAC station of Synergetic Extreme Condition User Facility(SECUF,https://cstr.cn/31123.02.SECUF)。
文摘Compared to traditional superhard materials with high electron density and short,strong covalent bonds,alloy materials mainly composed of metallic bonding structures typically have great toughness and lower hardness.Breaking through the limits of alloy materials is a preface and long-term topic,which is of great significance and value for improving the comprehensive mechanical properties of alloy materials.Here,we report on the discovery of a cubic alloy semiconducting material Ti_(2)Co with a large Vickers of hardness K_(v)^(exp)∼6.7GPa and low fracture toughness of K_(IC)^(exp)∼1.51MPa·m^(1/2).Unexpectedly,the K_(v)^(exp)∼6.7GPa is nearly triple of the K_(v)^(cal)∼2.66GPa predicted by density functional theory(DFT)calculations and theK_(IC)^(exp)∼1.51MPa·m^(1/2)is about one or two orders of magnitude smaller than that of ordinary titanium alloy materials(K_(IC)^(exp)∼30-120MPa·m^(1/2)).These specifications place Ti_(2)Co far from the phase space of the known alloy materials.Upon incorporation of oxygen into structural void positions,both values were simultaneously improved for Ti_(4)Co_(2)O to∼9.7GPa and∼2.19MPa·m^(1/2),respectively.Further DFT calculations on the electron localization function of Ti_(4)Co_(2)X(X=B,C,N,O)vs.the interstitial elements indicate that these simultaneous improvements originate from the coexistence of Ti-Co metallic bonds,the emergence of newly oriented Ti-X covalent bonds,and the increase of electron concentration.Moreover,the large difference between K_(v)^(exp)and K_(v)^(cal)of Ti_(2)Co suggests underlying mechanism concerning the absence of the O(16d)or Ti_(2)-O bonds in the O-(Ti_(2))_(6) octahedron.This discovery proposes a new pathway to simultaneously improve the comprehensive mechanical performances and illuminates the path of exploring superconducting materials with excellent mechanical performances.
