We report the successful growth and characterization of Li_9Cr_3(P_2O_7)_3(PO_4)_2single crystal,and investigate its magnetic properties under external magnetic fields via magnetization and heat capacity measurements....We report the successful growth and characterization of Li_9Cr_3(P_2O_7)_3(PO_4)_2single crystal,and investigate its magnetic properties under external magnetic fields via magnetization and heat capacity measurements.Our study reveals that Li_9Cr_3(P_2O_7)_3(PO_4)_2 is an easy-plane kagome ferromagnet with S=3/2,as evidenced by the Curie–Weiss temperature of 6 K which implies a ferromagnetic exchange coupling in the material.Under zero magnetic field,Li_9Cr_3(P_2O_7)_3(PO_4)_2 undergoes a magnetic transition at TC=2.7 K from a paramagnetic state to a ferromagnetically ordered state with the magnetic moment lying in the kagome plane.By applying a c-axis directional magnetic field to rotate the spin alignment from the kagome plane to the c-axis,we observe a reduction in the magnetic transition temperature as the field is increased.We construct a magnetic phase diagram as a function of temperature and magnetic field applied parallel to the c-axis of Li_9Cr_3(P_2O_7)_3(PO_4)_2 and find that the phase boundary is linear over a certain temperature range.Regarding that theoretically,the field-induced phase transition of the spin reorientation in the easy-plane ferromagnet can be viewed as the ferromagnetic magnon Bose–Einstein condensation(BEC),the phase boundary scaling of field-induced(B c)magnetic transition in Li_9Cr_3(P_2O_7)_3(PO_4)_2 can be described as the quasi-2D magnon BEC,which has been observed in other ferromagnetic materials such as K_2CuF_4.展开更多
In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it ...In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it is predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral“Dirac-like” fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Such an unconventional chiral fermion, protected by a hidden SU(2) symmetry in the hierarchy of an enhanced crystallographic group, namely spin space group, is not experimentally verified yet. Here, by angle-resolved photoemission spectroscopy measurements, we reveal the surface origin of the electron pocket at the Fermi surface in collinear antiferromagnet CoNb3S6. Combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear antiferromagnetic configuration, rendering the the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions.Our work provides spectral evidence of the chiral Dirac-like fermion caused by particular spin symmetry in CoNb_(3)S_(6), paving an avenue for exploring new emergent phenomena in antiferromagnets with unconventional quasiparticle excitations.展开更多
The spontaneous emission rate of a two-level quantum emitter(QE)near a gold nanorod is numerically investigated.Three different optical response models for the free-electron gas are adopted,including the classical Dru...The spontaneous emission rate of a two-level quantum emitter(QE)near a gold nanorod is numerically investigated.Three different optical response models for the free-electron gas are adopted,including the classical Drude local response approximation,the nonlocal hydrodynamic model,and the generalized nonlocal optical response model.Nonlocal optical response leads to a blueshift and a reduction in the enhancement of the spontaneous emission rate.Within all the three models,the resonance frequency is largely determined by the aspect ratio(the ratio of the nanorod length to the radius)and increases sharply with decreasing aspect ratio.For nanorod with a fixed length,it is found that the larger the radius is,the higher the resonance frequency is,and the smaller the enhancement is.However,if the length of the nanorod increases,the peak frequency falls sharply,while the spontaneous emission enhancement grows rapidly.For nanorod with a fixed aspect ratio,the peak frequency decreases slowly with increasing nanorod size.Larger nanorod shows smaller nonlocal effect.At a certain frequency,there is an optimal size to maximize the enhancement of the spontaneous emission rate.Higher order modes are more affected by the nonlocal smearing of the induced charges,leading to larger blueshift and greater reduction in the enhancement.These results should be significant for investigating the spontaneous emission rate of a QE around a gold nanorod.展开更多
Tritium concentrations in precipitation can be used as a criterion to evaluate the tritium baseline of the environment. The tritium concentration in precipitation in Shanghai during 2014-2015 was determined. Values ra...Tritium concentrations in precipitation can be used as a criterion to evaluate the tritium baseline of the environment. The tritium concentration in precipitation in Shanghai during 2014-2015 was determined. Values ranged from 0.68 ± 0.04 to 4.11 ± 0.39 Bq/L, and it showed a decreasing trend compared with historical data; however,the values were slightly higher than the natural background tritium level. Additionally, the tritium concentration shows a seasonal variation: It was higher in autumn and winter and lower in summer and spring. A comparison of concentrations in precipitation in Shanghai and around the Qinshan Nuclear Power Plant reveals no correlation,implying that the nuclear power plant operations may not affect the environment of Shanghai. Thus, the raised tritium concentrations in Shanghai might be due to the effects of monsoons, spring leak, raindrop, or other activities that generate tritium there. Those activities may include chemistry research that uses tritium as a tracer.展开更多
Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacan...Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacancy were investigated. Several new stable structures were found, along with their corresponding energy barriers. In double-vacancy graphene, the preferred sites of H atoms were identified, and H2 molecule desorption and adsorption of from/on were calculated from the energy barriers. This work provides a systematic and comprehensive understanding of hydrogen behavior on defected graphene.展开更多
We report construction of an iodine-stabilized laser frequency standard at 532 nm based on modulation transfer spectroscopy(MTS)technology with good reproducibility.A frequency stability of 2.5×10^(-14)at 1 s ave...We report construction of an iodine-stabilized laser frequency standard at 532 nm based on modulation transfer spectroscopy(MTS)technology with good reproducibility.A frequency stability of 2.5×10^(-14)at 1 s averaging time is achieved,and the frequency reproducibility has a relative uncertainty of 3.5×10^(-13),demonstrating the great stability of our setup.The systematic uncertainty of the iodine-stabilized laser frequency standard is evaluated,especially the contribution of the residual amplitude modulation(RAM).The contribution of the RAM in MTS cannot be evaluated directly.To solve this problem,we theoretically deduce the MTS signal with RAM under large modulation depth,and prove that the non-symmetric shape of the MTS signal is directly related to the MTS effect.The non-symmetric shape factor can be calibrated with a frequency comb,and in real experiments,this value can be obtained by least-squares fitting of the MTS signal,from which we can infer the RAMinduced frequency shift.The full frequency uncertainty is evaluated to be 5.3 kHz(corresponding to a relative frequency uncertainty of 9.4×10^(-12)).The corrected transition frequency has a difference from the BIPM-recommended value of 2 kHz,which is within 1σ uncertainty,proving the validity of our evaluation.展开更多
In this study, concentrations of tritiated water(HTO) and non-exchangeable organically bound tritium(NE-OBT) and the NE-OBT/HTO ratios were determined in soil around Qinshan Nuclear Power Plant(NPP), Zhejiang, China, ...In this study, concentrations of tritiated water(HTO) and non-exchangeable organically bound tritium(NE-OBT) and the NE-OBT/HTO ratios were determined in soil around Qinshan Nuclear Power Plant(NPP), Zhejiang, China, and their vertical profile and spatial distribution were investigated. Results showed variations in both the HTO and NE-OBT concentrations in the vertical profile. The HTO concentrations generally decreased firstly and then increased with the increasing depths, but the trend was not significant. The NE-OBT concentrations in the surface soils(0–5 cm) were considerably lower than those in the deep soils(5–25 cm) at all the sites. The NE-OBT/HTO ratios also show a variable vertical profile, initially increasing and then decreasing with increasing soil depth.Both the HTO and NE-OBT concentrations decreased with the increasing distance to the HWRs in deep soil layers(5–25 cm), revealing that the released tritium from the NPP affected the spatial distribution.展开更多
Spatial modulation(SM) is a class of novel multiple-input multiple-output(MIMO) techniques toward future wireless communications,which activates only one transmit antenna in each time slot,so as to reduce the number o...Spatial modulation(SM) is a class of novel multiple-input multiple-output(MIMO) techniques toward future wireless communications,which activates only one transmit antenna in each time slot,so as to reduce the number of RF chains for saving the implement cost.Meanwhile,considering its application in 5G systems with multiple users,the detection of multi-user spatial modulation has drawn greater attention.In this paper,a pair of efficient detectors are proposed for multi-user spatial modulation.Specially,a threshold-aided approximate message passing(T-AMP) detector is proposed with the purpose of reducing the computational complexity of traditional structured approximate message passing(Str-AMP) detector.In addition,a novel probability sorting aided approximate message passing detector,called probability-ranking-aided AMP detector(P-AMP),is also proposed with the purpose of improving the performance.Simulation results show that the proposed T-AMP detector is able to achieve similar performance as traditional StrAMP with lower complexity,while the proposed P-AMP detector exhibits a better symbol error rate(SER) performance with similar complexity.展开更多
Macadamia from the family Proteaceae is a plant native to Australia and has long been favoured by people for its crispy and high nutritional and medicinal value.Here,the genome of GUIRE 1(GR1),a highly heterozygous su...Macadamia from the family Proteaceae is a plant native to Australia and has long been favoured by people for its crispy and high nutritional and medicinal value.Here,the genome of GUIRE 1(GR1),a highly heterozygous superior cultivar of macadamia nut,was sequenced and assembled using nanopore sequencing,and a 807-Mb genome(contig N50,1.9 Mb;scaffold N50,54.70 Mb)and 14 chromosomes were obtained.A total of 453 Mb(about 55.95%)repetitive sequences and 37,657 protein-coding genes were obtained by gene annotation and homologous protein comparison.Proteaceae diverged from Nelumbonaceae nearly 115.37 million years ago and from Rubiaceae about 140 million years ago.A genome-wide duplication(WGD)event occurred in macadamia 41 million years ago based on the WGD analysis.The functional enrichment analysis of M.integrifolia-specific gene families revealed their roles in signal transduction,protein phosphorylation,protein binding,and defense response.Here,a highly heterozygous genome of M.integrifolia was unlocked to provide a database for breeding and molecular mechanism research.展开更多
Organic compounds are widely used in both industry and daily life,and composite bilayer films with organic compound-triggered bending properties are promising for applications of transducers,soft robotics,and so on.He...Organic compounds are widely used in both industry and daily life,and composite bilayer films with organic compound-triggered bending properties are promising for applications of transducers,soft robotics,and so on.Here,a universal and straightforward strategy to generate composite bilayer films with organic compoundtriggered bending properties is demonstrated.The composite bilayer films with organic compound-triggered bending properties are designed with bilayer structures,in which one layer is a porous polymeric membrane with appropriate solubility parameter that matches the value of organic solvents in order to produce prominent affinity to the solvent molecules,and the other layer is reduced graphene oxide membrane stacked on the porous polymeric membrane as an inert layer for restraining the swelling of the polymeric membrane on one side.Guided by matching the solubility parameters between solvent and polymer,a significant bending curvature of 27.3 cm-1 is obtained in acetone vapor.The results in this study will provide valuable guidance for designing and developing functional composite materials with significant organic compound-triggered bending properties.展开更多
Individual’s phenotypic traits are the results of adaptation to ecological conditions.Therefore,different selection pressures caused by heterogeneous environments may result in phenotypic difference,especially for in...Individual’s phenotypic traits are the results of adaptation to ecological conditions.Therefore,different selection pressures caused by heterogeneous environments may result in phenotypic difference,especially for individuals in different geographical populations.Here,we illustrated for the first time to use social network analysis(SNA)for examining whether geographical proximity predicts the similarity patterns in call characteristics among populations of an anuran species.We recorded calls from 150 male dorsal-striped opposite-fingered treefrogs(Chiromantis doriae)at 11 populations in Hainan Province and one population in Guangdong Province in China's Mainland,and we measured eight acoustic variables for each male.Mantel test didn’t show a correlation between geographical proximity and the similarity in call characteristics among populations.In addition,we failed to find correlations between a population’s eigenvector centrality and the distance to its nearest neighbor,nor between the coefficient of variation of similarity in call characteristics of a population and the average distance to all other populations.Nevertheless,three acoustic clusters were identified by the Girvan-Newman algorithm,and clustering was partially associated with geography.Furthermore,the most central populations were included in the same cluster,but the top betweenness populations were located within different clusters,suggesting that centrality populations are not necessary bridging between clusters.These results demonstrate the potential usefulness of the SNA toolbox and indicate that SNA helps to uncover the patterns that often overlooked in other analytical methods.By using SNA in frog’s call studies,researchers could further uncover the potential relationship in call characteristics between geographical populations,further reveal the effects of ecological factors on call characteristics,and probably enhance our understanding of the adaptive evolution of acoustic signals.展开更多
Vocal communication plays an important role in survival,reproduction,and animal social association.Birds and mammals produce com-plex vocal sequence to convey context-dependent information.Vocalizations are conspicuou...Vocal communication plays an important role in survival,reproduction,and animal social association.Birds and mammals produce com-plex vocal sequence to convey context-dependent information.Vocalizations are conspicuous features of the behavior of most anuran species(frogs and toads),and males usually alter their calling strategies according to ecological context to improve the attractiveness/competitiveness.However,very few studies have focused on the variation of vocal sequence in anurans.In the present study,we used both conventional method and network analysis to investigate the context-dependent vocal repertoire,vocal sequence,and call network structure in serrate-legged small treefrogs Kurixalus odontotarsus.We found that male K.odontotarsus modified their vocal sequence by switching to different call types and increasing repertoire size in the presence of a competitive rival.Specifically,compared with before and after the playback of advertisement calls,males emited fewer advertisement calls,but more aggressive calls,encounter calls,and compound calls during the playback period.Network analysis revealed that the mean degree,mean closeness,and mean betweenness of the call networks significantly decreased during the playback period,which resulted in lower connectivity.in addition,the increased proportion of one-way motifs and average path length also indicated that the connectivity of the call network decreased in competitive context.However,the vocal sequence of K.odontotarsus did not display a clear small-world network structure,regardless of context.Our study presents a paradigm to apply network analysis to vocal sequence in anurans and has important implications for understanding the evolution and function of sequence patterns.展开更多
Astronomical detection at infrared wavelengths is crucial in astrophysics due to the critical information in this wavelength range.Blocked impurity band(BIB) infrared detectors are desirable for space-based astronomic...Astronomical detection at infrared wavelengths is crucial in astrophysics due to the critical information in this wavelength range.Blocked impurity band(BIB) infrared detectors are desirable for space-based astronomical observation due to their broad response range, low dark currents, high quantum efficiencies, and excellent radiation resistance. In this review, typical BIB device structures and device physics development are first introduced. Subsequently, we discuss progress in Si-based BIB detectors with different doping types and emphasize their applications in space-based infrared detection. Additionally, we discuss recent efforts on pixel performance optimization, response extension, and higher operating temperature devices. Finally,we conclude by proposing the challenges and perspectives of BIB detectors with improved detection performances.展开更多
Background:Keloids are benign fibrous growths that are caused by excessive tissue build-up.Severe keloids exert more significant effects on patients’quality of life than do mild keloids.We aimed to identify factors a...Background:Keloids are benign fibrous growths that are caused by excessive tissue build-up.Severe keloids exert more significant effects on patients’quality of life than do mild keloids.We aimed to identify factors associated with the progression from mild keloids to severe keloids,as distinct from those associated with the formation of keloids.Methods:In this retrospective case-control study,251 patients diagnosed with keloids at West China Hospital between November 2018 and April 2021 were grouped according to the severity of lesions(mild[n=162]or severe[n=89]).We collected their basic characteristics,living habits,incomes,comorbidities,and keloid characteristics from Electronic Medical Records in the hospital and the patients’interviews.Conditional multivariable regression was performed to identify the independent risk factors for the progression of keloids.Results:Eighty-nine patients(35.5%)were classified as having severe keloids.We found the distribution of severe keloids varied with sex,age,excessive scrubbing of keloids,family income,the comorbidity of rheumatism,disease duration,characteristics of the location,location in sites of high-stretch tension,the severity and frequency of pain,the severity of pruritus,and infection.Multivariable analysis revealed significant associations between severe keloids and infection(odds ratio[OR],3.55;P=0.005),excessive scrubbing of keloids(OR,8.65;P=0.001),low or middle family income(OR,13.44;P=0.021),comorbidity of rheumatism(OR,18.97;P=0.021),multiple keloids located at multiple sites(OR,3.18;P=0.033),and disease duration>15 years(OR,2.98;P=0.046).Conclusion:Doctors should implement more active and thorough measures to minimize the progression of mild keloids in patients who have any of the following risk factors:infection,excessive scrubbing of keloids,low or middle family income,comorbidity of rheumatism,multiple keloids located at multiple sites,and disease duration>15 years.展开更多
To the Editor:Keloids are a specific type of scar that exceeds the original wound boundary and unlikely to shrink spontaneously.Numerous methods for treating keloids have been reported,including surgical resection,rad...To the Editor:Keloids are a specific type of scar that exceeds the original wound boundary and unlikely to shrink spontaneously.Numerous methods for treating keloids have been reported,including surgical resection,radiation,injection,laser therapy,and cryotherapy.However,no single method can ensure a complete cure.Among the reported methods,the intralesional injection of steroids is widely used.A large number of studies have shown that the injection of glucocorticoids combined with 5-fluorouracil(5-FU)into the keloid can soften the texture,reduce the volume,and relieve the associated symptoms.[1]The conventional intralesional injection was routinely performed by directly injecting the drug into the parenchyma through the surface of the keloid in a multipoint manner.展开更多
The assembling behavior and electronic properties of asymmetric tris(phthalocyaninato)lutetium triple-decker sandwich complex molecules(Lu2Pc3)on highly oriented pyrolytic graphite(HOPG)surfaces have been studied by s...The assembling behavior and electronic properties of asymmetric tris(phthalocyaninato)lutetium triple-decker sandwich complex molecules(Lu2Pc3)on highly oriented pyrolytic graphite(HOPG)surfaces have been studied by scanning tunneling microscopy/spectroscopy(STM/STS)methods.Phase transitions were observed at different bias polarities,involving an ordered packing arrangement with fourfold symmetry at negative bias and an amorphous arrangement at positive bias.Molecular switching behaviour for individual Lu2Pc3 molecules was reported here according to the bias-polarity-induced flipping phenomena and the peak shift in dI/dV versus V curves at different voltage scanning directions.The sensitive response of the strong intrinsic molecular dipole to an external electric field is proposed to be responsible for molecular switching of Lu_(2)Pc_(3)at the solid/liquid interface.展开更多
动物社会网络分析法(animal social network analysis,ASNA)是一套用于研究动物社会性、量化个体间各种社会关系、揭示个体行为与社会结构动态之间联系的工具,被广泛应用于多种动物类群的行为学研究。该分析方法所提供的一系列指标也非...动物社会网络分析法(animal social network analysis,ASNA)是一套用于研究动物社会性、量化个体间各种社会关系、揭示个体行为与社会结构动态之间联系的工具,被广泛应用于多种动物类群的行为学研究。该分析方法所提供的一系列指标也非常适用于探究动物的声音交流及鸣声结构。在此,本文首先简要介绍了网络分析法的基本概念及一些常用的指标;然后基于野外和室内研究实例,阐述了如何利用ASNA建立声音通讯网络、量化声音交流,以及将ASNA与被动声学监测技术相结合的应用前景;随后探讨了ASNA在分析鸣声相似性及鸣声地理变异中的优势;最后概述了ASNA在解析鸣声结构和句法规则中的应用。ASNA为研究动物通讯网络以及声音信号的适应性进化提供了新的视角和新的思路。展开更多
Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems.In this work,the assembly structure and microscale superlubricity of a h...Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems.In this work,the assembly structure and microscale superlubricity of a host–guest assembly are effectively controlled by the electric field.With the help of the scanning tunneling microscopy(STM)technique,the host–guest assembly structures constructed by the co-assembly of fullerene derivative(Fluorene-C60)with macrocycles(4B2A and 3B2A)are explicitly characterized.Combined with density functional theory(DFT),the distinct different assembly behaviors of fullerene derivatives are revealed at different probe biases,which is attributed to the molecular polarity of the fullerene derivative.Through the control on the adsorption behavior,the friction coefficient of host–guest assembly is demonstrated to be controllable in the electric field by using atomic force microscopy(AFM).At positive probe bias,the friction coefficient of the host–guest assembly is significantly reduced and achieves superlubricity(μmin=0.0049).The efforts not only help us gain insight into the host–guest assembly mechanism controlled by the electric field,but also promote the further application of fullerene in micro-electro-mechanical systems(MEMS).展开更多
基金Shenzhen Fundamental Research Program(Grant No.JCYJ20220818100405013)。
文摘We report the successful growth and characterization of Li_9Cr_3(P_2O_7)_3(PO_4)_2single crystal,and investigate its magnetic properties under external magnetic fields via magnetization and heat capacity measurements.Our study reveals that Li_9Cr_3(P_2O_7)_3(PO_4)_2 is an easy-plane kagome ferromagnet with S=3/2,as evidenced by the Curie–Weiss temperature of 6 K which implies a ferromagnetic exchange coupling in the material.Under zero magnetic field,Li_9Cr_3(P_2O_7)_3(PO_4)_2 undergoes a magnetic transition at TC=2.7 K from a paramagnetic state to a ferromagnetically ordered state with the magnetic moment lying in the kagome plane.By applying a c-axis directional magnetic field to rotate the spin alignment from the kagome plane to the c-axis,we observe a reduction in the magnetic transition temperature as the field is increased.We construct a magnetic phase diagram as a function of temperature and magnetic field applied parallel to the c-axis of Li_9Cr_3(P_2O_7)_3(PO_4)_2 and find that the phase boundary is linear over a certain temperature range.Regarding that theoretically,the field-induced phase transition of the spin reorientation in the easy-plane ferromagnet can be viewed as the ferromagnetic magnon Bose–Einstein condensation(BEC),the phase boundary scaling of field-induced(B c)magnetic transition in Li_9Cr_3(P_2O_7)_3(PO_4)_2 can be described as the quasi-2D magnon BEC,which has been observed in other ferromagnetic materials such as K_2CuF_4.
基金supported by the National Key R&D Program of China (Grant Nos. 2020YFA0308900 and 2022YFA1403700)the National Natural Science Foundation of China (Grant Nos. 12074163, 12134020, 11974157, 12104255, 12004159, and 12374146)+8 种基金Guangdong Provincial Key Laboratory for Computational Science and Material Design (Grant No. 2019B030301001)the Science, Technology and Innovation Commission of Shenzhen Municipality (Grant Nos. ZDSYS20190902092905285 and KQTD20190929173815000)Guangdong Basic and Applied Basic Research Foundation (Grant Nos. 2022B1515020046, 2021B1515130007, 2022A1515011915, 2019A1515110712, and 2022B1515130005)Shenzhen Science and Technology Program (Grant Nos. RCJC20221008092722009 and RCBS20210706092218039)the Guangdong Innovative and Entrepreneurial Research Team Program (Grant No. 2019ZT08C044)the beam time awarded by Australia’s Nuclear Science and Technology Organisation (ANSTO) (Grant No. P8130)the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex (J-PARC) was performed under a user program (Proposal No. 2019B0140)performed at the Hiroshima Synchrotron Radiation Center (HiSOR) of Japan (Grant Nos. 22BG023 and 22BG029)Shanghai Synchrotron Radiation Facility (SSRF) BL03U (Grant No. 2022-SSRF-PT-020848)。
文摘In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it is predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral“Dirac-like” fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Such an unconventional chiral fermion, protected by a hidden SU(2) symmetry in the hierarchy of an enhanced crystallographic group, namely spin space group, is not experimentally verified yet. Here, by angle-resolved photoemission spectroscopy measurements, we reveal the surface origin of the electron pocket at the Fermi surface in collinear antiferromagnet CoNb3S6. Combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear antiferromagnetic configuration, rendering the the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions.Our work provides spectral evidence of the chiral Dirac-like fermion caused by particular spin symmetry in CoNb_(3)S_(6), paving an avenue for exploring new emergent phenomena in antiferromagnets with unconventional quasiparticle excitations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11964010,11564013 and 11464014)the Natural Science Foundation of Hunan Province(Grant No.2020JJ4495)+1 种基金the Scientific Research Fund of Hunan Provincial Education Department,China(Grant No.18C0558)the Hunan Provincial Innovation Foundation for Postgraduate,China(Grant Nos.CX2018B706 and CX20190876)。
文摘The spontaneous emission rate of a two-level quantum emitter(QE)near a gold nanorod is numerically investigated.Three different optical response models for the free-electron gas are adopted,including the classical Drude local response approximation,the nonlocal hydrodynamic model,and the generalized nonlocal optical response model.Nonlocal optical response leads to a blueshift and a reduction in the enhancement of the spontaneous emission rate.Within all the three models,the resonance frequency is largely determined by the aspect ratio(the ratio of the nanorod length to the radius)and increases sharply with decreasing aspect ratio.For nanorod with a fixed length,it is found that the larger the radius is,the higher the resonance frequency is,and the smaller the enhancement is.However,if the length of the nanorod increases,the peak frequency falls sharply,while the spontaneous emission enhancement grows rapidly.For nanorod with a fixed aspect ratio,the peak frequency decreases slowly with increasing nanorod size.Larger nanorod shows smaller nonlocal effect.At a certain frequency,there is an optimal size to maximize the enhancement of the spontaneous emission rate.Higher order modes are more affected by the nonlocal smearing of the induced charges,leading to larger blueshift and greater reduction in the enhancement.These results should be significant for investigating the spontaneous emission rate of a QE around a gold nanorod.
文摘Tritium concentrations in precipitation can be used as a criterion to evaluate the tritium baseline of the environment. The tritium concentration in precipitation in Shanghai during 2014-2015 was determined. Values ranged from 0.68 ± 0.04 to 4.11 ± 0.39 Bq/L, and it showed a decreasing trend compared with historical data; however,the values were slightly higher than the natural background tritium level. Additionally, the tritium concentration shows a seasonal variation: It was higher in autumn and winter and lower in summer and spring. A comparison of concentrations in precipitation in Shanghai and around the Qinshan Nuclear Power Plant reveals no correlation,implying that the nuclear power plant operations may not affect the environment of Shanghai. Thus, the raised tritium concentrations in Shanghai might be due to the effects of monsoons, spring leak, raindrop, or other activities that generate tritium there. Those activities may include chemistry research that uses tritium as a tracer.
基金supported by the National Natural Science Foundation of China(Grant No.5160121211475082)‘‘Strategic Priority Research Program of Chinese Academy of Sciences’’ Thorium Molten Salts Reactor Fund
文摘Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacancy were investigated. Several new stable structures were found, along with their corresponding energy barriers. In double-vacancy graphene, the preferred sites of H atoms were identified, and H2 molecule desorption and adsorption of from/on were calculated from the energy barriers. This work provides a systematic and comprehensive understanding of hydrogen behavior on defected graphene.
基金the National Key Research and Development Program of China(Grant No.2017YFA0304401)Key-Area Research and Development Program of GuangDong Province,China(Grant No.2019B030330001)the National Natural Science Foundation of China(Grant Nos.11174095,61875065,91536116,and 11804108).
文摘We report construction of an iodine-stabilized laser frequency standard at 532 nm based on modulation transfer spectroscopy(MTS)technology with good reproducibility.A frequency stability of 2.5×10^(-14)at 1 s averaging time is achieved,and the frequency reproducibility has a relative uncertainty of 3.5×10^(-13),demonstrating the great stability of our setup.The systematic uncertainty of the iodine-stabilized laser frequency standard is evaluated,especially the contribution of the residual amplitude modulation(RAM).The contribution of the RAM in MTS cannot be evaluated directly.To solve this problem,we theoretically deduce the MTS signal with RAM under large modulation depth,and prove that the non-symmetric shape of the MTS signal is directly related to the MTS effect.The non-symmetric shape factor can be calibrated with a frequency comb,and in real experiments,this value can be obtained by least-squares fitting of the MTS signal,from which we can infer the RAMinduced frequency shift.The full frequency uncertainty is evaluated to be 5.3 kHz(corresponding to a relative frequency uncertainty of 9.4×10^(-12)).The corrected transition frequency has a difference from the BIPM-recommended value of 2 kHz,which is within 1σ uncertainty,proving the validity of our evaluation.
文摘In this study, concentrations of tritiated water(HTO) and non-exchangeable organically bound tritium(NE-OBT) and the NE-OBT/HTO ratios were determined in soil around Qinshan Nuclear Power Plant(NPP), Zhejiang, China, and their vertical profile and spatial distribution were investigated. Results showed variations in both the HTO and NE-OBT concentrations in the vertical profile. The HTO concentrations generally decreased firstly and then increased with the increasing depths, but the trend was not significant. The NE-OBT concentrations in the surface soils(0–5 cm) were considerably lower than those in the deep soils(5–25 cm) at all the sites. The NE-OBT/HTO ratios also show a variable vertical profile, initially increasing and then decreasing with increasing soil depth.Both the HTO and NE-OBT concentrations decreased with the increasing distance to the HWRs in deep soil layers(5–25 cm), revealing that the released tritium from the NPP affected the spatial distribution.
基金The financial support is gratefully acknowledged by the National Science Foundation of China under Grant numbers 61471090the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University(No.2015D09)+1 种基金the Foundation Project of Science and Technology on Electronic Information Control Laboratory under Grant JS17041403811(201606071370-004001)the Foundation Project of National Key Lab.of Sci.and Tech.on Comm.under Grant 6142102010702
文摘Spatial modulation(SM) is a class of novel multiple-input multiple-output(MIMO) techniques toward future wireless communications,which activates only one transmit antenna in each time slot,so as to reduce the number of RF chains for saving the implement cost.Meanwhile,considering its application in 5G systems with multiple users,the detection of multi-user spatial modulation has drawn greater attention.In this paper,a pair of efficient detectors are proposed for multi-user spatial modulation.Specially,a threshold-aided approximate message passing(T-AMP) detector is proposed with the purpose of reducing the computational complexity of traditional structured approximate message passing(Str-AMP) detector.In addition,a novel probability sorting aided approximate message passing detector,called probability-ranking-aided AMP detector(P-AMP),is also proposed with the purpose of improving the performance.Simulation results show that the proposed T-AMP detector is able to achieve similar performance as traditional StrAMP with lower complexity,while the proposed P-AMP detector exhibits a better symbol error rate(SER) performance with similar complexity.
基金supported by Guangxi Natural Science Foundation under Grant No.2019GXNSFBA18501.
文摘Macadamia from the family Proteaceae is a plant native to Australia and has long been favoured by people for its crispy and high nutritional and medicinal value.Here,the genome of GUIRE 1(GR1),a highly heterozygous superior cultivar of macadamia nut,was sequenced and assembled using nanopore sequencing,and a 807-Mb genome(contig N50,1.9 Mb;scaffold N50,54.70 Mb)and 14 chromosomes were obtained.A total of 453 Mb(about 55.95%)repetitive sequences and 37,657 protein-coding genes were obtained by gene annotation and homologous protein comparison.Proteaceae diverged from Nelumbonaceae nearly 115.37 million years ago and from Rubiaceae about 140 million years ago.A genome-wide duplication(WGD)event occurred in macadamia 41 million years ago based on the WGD analysis.The functional enrichment analysis of M.integrifolia-specific gene families revealed their roles in signal transduction,protein phosphorylation,protein binding,and defense response.Here,a highly heterozygous genome of M.integrifolia was unlocked to provide a database for breeding and molecular mechanism research.
基金Supported by the National Natural Science Foundation of China(21490582,21622604)the Program for Changjiang Scholars and Innovative Research Team in University(IRT15R48)the State Key Laboratory of Polymer Materials Engineering(sklpme2017-3-03,sklpme2014-1-01).
文摘Organic compounds are widely used in both industry and daily life,and composite bilayer films with organic compound-triggered bending properties are promising for applications of transducers,soft robotics,and so on.Here,a universal and straightforward strategy to generate composite bilayer films with organic compoundtriggered bending properties is demonstrated.The composite bilayer films with organic compound-triggered bending properties are designed with bilayer structures,in which one layer is a porous polymeric membrane with appropriate solubility parameter that matches the value of organic solvents in order to produce prominent affinity to the solvent molecules,and the other layer is reduced graphene oxide membrane stacked on the porous polymeric membrane as an inert layer for restraining the swelling of the polymeric membrane on one side.Guided by matching the solubility parameters between solvent and polymer,a significant bending curvature of 27.3 cm-1 is obtained in acetone vapor.The results in this study will provide valuable guidance for designing and developing functional composite materials with significant organic compound-triggered bending properties.
基金National Natural Science Foundation of China(31772464,32000313)CAS“Light of West China”Program(2017XBZGXBQNXZB013)+1 种基金Youth Innovation Promotion Association CAS(2012274)the Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment,China(2019HJ2096001006)。
文摘Individual’s phenotypic traits are the results of adaptation to ecological conditions.Therefore,different selection pressures caused by heterogeneous environments may result in phenotypic difference,especially for individuals in different geographical populations.Here,we illustrated for the first time to use social network analysis(SNA)for examining whether geographical proximity predicts the similarity patterns in call characteristics among populations of an anuran species.We recorded calls from 150 male dorsal-striped opposite-fingered treefrogs(Chiromantis doriae)at 11 populations in Hainan Province and one population in Guangdong Province in China's Mainland,and we measured eight acoustic variables for each male.Mantel test didn’t show a correlation between geographical proximity and the similarity in call characteristics among populations.In addition,we failed to find correlations between a population’s eigenvector centrality and the distance to its nearest neighbor,nor between the coefficient of variation of similarity in call characteristics of a population and the average distance to all other populations.Nevertheless,three acoustic clusters were identified by the Girvan-Newman algorithm,and clustering was partially associated with geography.Furthermore,the most central populations were included in the same cluster,but the top betweenness populations were located within different clusters,suggesting that centrality populations are not necessary bridging between clusters.These results demonstrate the potential usefulness of the SNA toolbox and indicate that SNA helps to uncover the patterns that often overlooked in other analytical methods.By using SNA in frog’s call studies,researchers could further uncover the potential relationship in call characteristics between geographical populations,further reveal the effects of ecological factors on call characteristics,and probably enhance our understanding of the adaptive evolution of acoustic signals.
基金supported by the National Natural Science Foundation of China(31772464,32000313)Youth Innovation Promotion Association CAS(2012274)+2 种基金Sichuan ScienceandTechnology Program1(2022JDTD0026)NaturalScience Foundation of Sichuan Province(2022NSFSC1736)Open Research Program in Ministry of Education Key Laboratory for Ecology of Tropical Islands(HNSF-OP-202002).
文摘Vocal communication plays an important role in survival,reproduction,and animal social association.Birds and mammals produce com-plex vocal sequence to convey context-dependent information.Vocalizations are conspicuous features of the behavior of most anuran species(frogs and toads),and males usually alter their calling strategies according to ecological context to improve the attractiveness/competitiveness.However,very few studies have focused on the variation of vocal sequence in anurans.In the present study,we used both conventional method and network analysis to investigate the context-dependent vocal repertoire,vocal sequence,and call network structure in serrate-legged small treefrogs Kurixalus odontotarsus.We found that male K.odontotarsus modified their vocal sequence by switching to different call types and increasing repertoire size in the presence of a competitive rival.Specifically,compared with before and after the playback of advertisement calls,males emited fewer advertisement calls,but more aggressive calls,encounter calls,and compound calls during the playback period.Network analysis revealed that the mean degree,mean closeness,and mean betweenness of the call networks significantly decreased during the playback period,which resulted in lower connectivity.in addition,the increased proportion of one-way motifs and average path length also indicated that the connectivity of the call network decreased in competitive context.However,the vocal sequence of K.odontotarsus did not display a clear small-world network structure,regardless of context.Our study presents a paradigm to apply network analysis to vocal sequence in anurans and has important implications for understanding the evolution and function of sequence patterns.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFB2009301)the National Natural Science Foundation of China(Grant Nos.11933006,61805060,62175045,62104053,62174063,and U2141240)+2 种基金Zhejiang Provincial Natural Science Foundation of China(Grant No.LGF21F050001)Hangzhou Key Research and Development Program(Grant No.20212013B01)Hangzhou Science and Technology Bureau(Grant No.TD2020002)。
文摘Astronomical detection at infrared wavelengths is crucial in astrophysics due to the critical information in this wavelength range.Blocked impurity band(BIB) infrared detectors are desirable for space-based astronomical observation due to their broad response range, low dark currents, high quantum efficiencies, and excellent radiation resistance. In this review, typical BIB device structures and device physics development are first introduced. Subsequently, we discuss progress in Si-based BIB detectors with different doping types and emphasize their applications in space-based infrared detection. Additionally, we discuss recent efforts on pixel performance optimization, response extension, and higher operating temperature devices. Finally,we conclude by proposing the challenges and perspectives of BIB detectors with improved detection performances.
文摘Background:Keloids are benign fibrous growths that are caused by excessive tissue build-up.Severe keloids exert more significant effects on patients’quality of life than do mild keloids.We aimed to identify factors associated with the progression from mild keloids to severe keloids,as distinct from those associated with the formation of keloids.Methods:In this retrospective case-control study,251 patients diagnosed with keloids at West China Hospital between November 2018 and April 2021 were grouped according to the severity of lesions(mild[n=162]or severe[n=89]).We collected their basic characteristics,living habits,incomes,comorbidities,and keloid characteristics from Electronic Medical Records in the hospital and the patients’interviews.Conditional multivariable regression was performed to identify the independent risk factors for the progression of keloids.Results:Eighty-nine patients(35.5%)were classified as having severe keloids.We found the distribution of severe keloids varied with sex,age,excessive scrubbing of keloids,family income,the comorbidity of rheumatism,disease duration,characteristics of the location,location in sites of high-stretch tension,the severity and frequency of pain,the severity of pruritus,and infection.Multivariable analysis revealed significant associations between severe keloids and infection(odds ratio[OR],3.55;P=0.005),excessive scrubbing of keloids(OR,8.65;P=0.001),low or middle family income(OR,13.44;P=0.021),comorbidity of rheumatism(OR,18.97;P=0.021),multiple keloids located at multiple sites(OR,3.18;P=0.033),and disease duration>15 years(OR,2.98;P=0.046).Conclusion:Doctors should implement more active and thorough measures to minimize the progression of mild keloids in patients who have any of the following risk factors:infection,excessive scrubbing of keloids,low or middle family income,comorbidity of rheumatism,multiple keloids located at multiple sites,and disease duration>15 years.
文摘To the Editor:Keloids are a specific type of scar that exceeds the original wound boundary and unlikely to shrink spontaneously.Numerous methods for treating keloids have been reported,including surgical resection,radiation,injection,laser therapy,and cryotherapy.However,no single method can ensure a complete cure.Among the reported methods,the intralesional injection of steroids is widely used.A large number of studies have shown that the injection of glucocorticoids combined with 5-fluorouracil(5-FU)into the keloid can soften the texture,reduce the volume,and relieve the associated symptoms.[1]The conventional intralesional injection was routinely performed by directly injecting the drug into the parenchyma through the surface of the keloid in a multipoint manner.
基金the National Natural Science Foundation of China(90406019,20573116,and 20673029)the National Basic Research Program of China(973 Program,2006CB932100).
文摘The assembling behavior and electronic properties of asymmetric tris(phthalocyaninato)lutetium triple-decker sandwich complex molecules(Lu2Pc3)on highly oriented pyrolytic graphite(HOPG)surfaces have been studied by scanning tunneling microscopy/spectroscopy(STM/STS)methods.Phase transitions were observed at different bias polarities,involving an ordered packing arrangement with fourfold symmetry at negative bias and an amorphous arrangement at positive bias.Molecular switching behaviour for individual Lu2Pc3 molecules was reported here according to the bias-polarity-induced flipping phenomena and the peak shift in dI/dV versus V curves at different voltage scanning directions.The sensitive response of the strong intrinsic molecular dipole to an external electric field is proposed to be responsible for molecular switching of Lu_(2)Pc_(3)at the solid/liquid interface.
文摘动物社会网络分析法(animal social network analysis,ASNA)是一套用于研究动物社会性、量化个体间各种社会关系、揭示个体行为与社会结构动态之间联系的工具,被广泛应用于多种动物类群的行为学研究。该分析方法所提供的一系列指标也非常适用于探究动物的声音交流及鸣声结构。在此,本文首先简要介绍了网络分析法的基本概念及一些常用的指标;然后基于野外和室内研究实例,阐述了如何利用ASNA建立声音通讯网络、量化声音交流,以及将ASNA与被动声学监测技术相结合的应用前景;随后探讨了ASNA在分析鸣声相似性及鸣声地理变异中的优势;最后概述了ASNA在解析鸣声结构和句法规则中的应用。ASNA为研究动物通讯网络以及声音信号的适应性进化提供了新的视角和新的思路。
基金This work was financially supported by the National Basic Research Program of China(No.2017YFA0205000)the National Natural Science Foundation of China(Nos.51875303 and 21972031)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000).
文摘Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems.In this work,the assembly structure and microscale superlubricity of a host–guest assembly are effectively controlled by the electric field.With the help of the scanning tunneling microscopy(STM)technique,the host–guest assembly structures constructed by the co-assembly of fullerene derivative(Fluorene-C60)with macrocycles(4B2A and 3B2A)are explicitly characterized.Combined with density functional theory(DFT),the distinct different assembly behaviors of fullerene derivatives are revealed at different probe biases,which is attributed to the molecular polarity of the fullerene derivative.Through the control on the adsorption behavior,the friction coefficient of host–guest assembly is demonstrated to be controllable in the electric field by using atomic force microscopy(AFM).At positive probe bias,the friction coefficient of the host–guest assembly is significantly reduced and achieves superlubricity(μmin=0.0049).The efforts not only help us gain insight into the host–guest assembly mechanism controlled by the electric field,but also promote the further application of fullerene in micro-electro-mechanical systems(MEMS).