China is the world’s largest consumer of pork and grains.However,African swine fever(ASF)and the COVID-19 outbreak have greatly impacted the pork supply and food security in China.How can food security and the pork s...China is the world’s largest consumer of pork and grains.However,African swine fever(ASF)and the COVID-19 outbreak have greatly impacted the pork supply and food security in China.How can food security and the pork supply be ensured under the dual impacts of COVID-19 and ASF?This is a major problem to be urgently solved by the Chinese government.This study indicated that the main pork production and sales areas in China were separated,which reflected the spatial imbalance between the supply and demand.The total area of suitable selected sites for pig farms in China is 21.5 million ha.If only the areas with levels of high and moderate suitability are considered as potential sites for pig farms,the potential pork production can reach 56.1 million tons in China,which is slightly lower than demand.Due to the impact of the ASF epidemic,the food consumed by pigs has been reduced by 34.7 million tons.However,with increasing pork productivity in the future,the self-sufficiency rate of grains may further decline.On the premise that the quality of people’s life is not affected,the diversification of meat supply channels should be realized in an orderly and sustainable way,which might alleviate the pressure on food supply.This study provides a theoretical reference for the spatiotemporal layout of the swine industry and addresses the issue of food security in China under the influence of ASF and the COVID-19 outbreak.展开更多
The Gangdese batholith, more than 2500 km in length, is composed mainly of JurassicMiocene igneous rocks. This batholith is one of the most important constituents of the Tibetan orogenesis and provides an ideal place ...The Gangdese batholith, more than 2500 km in length, is composed mainly of JurassicMiocene igneous rocks. This batholith is one of the most important constituents of the Tibetan orogenesis and provides an ideal place for study of Neo-Tethyan ocean geodynamic evolution and plateau uplift. Recent studies on the Gangdese Jurassic felsic magmatism highlight its juvenile source. However, important aspects concerning the genesis of the juvenile magmatism and related deep geodynamic evolution are still unclear. Here, we report detailed petrological, geochronological, geochemical, whole-rock Sr-Nd isotopic, and in situ Sr-Hf isotopic data for a recently identified hornblende gabbro in the Dongga area, southern Lhasa sub-block. This hornblende gabbro is dominated by hornblende and plagioclase, dated at Early Jurassic（ca. 180–190 Ma）, and characterized by a narrow compositional range in SiO2（49.38wt%–52.27wt%）, MgO（4.08wt%–7.00wt%）, FeO（10.43wt%–11.77wt%）, Na2O（2.58wt%–3.51wt%）, and K2O（0.48wt%–1.53wt%）. It has depleted isotopic signatures, with whole-rock（87Sr/86Sr）i ratios of 0.7033–0.7043, εNd（t） values of ＋4.90 to ＋6.99, in situ plagioclase（87Sr/86Sr）i ratios of 0.7034–0.7042, and zircon εHf（t） of ＋12.2 to ＋16.8. Our results integrated with published data suggest a model of Gangdese juvenile crustal growth by a subduction-related water-enriched mantle wedge. The hydrous partial melting of the lithosphere mantle was triggered by the dehydration of a Neo-Tethyan oceanic slab. This mafic magmatism emplaced in the middle-lower crust of intraoceanic arcs or active continental margins, leading to Jurassic juvenile crustal growth in southern Tibet.展开更多
Weak localization and antilocalization are quantum transport phenomena that arise from the quantum interference in disordered metals.At low temperatures,they can give distinct temperature and magnetic field dependence...Weak localization and antilocalization are quantum transport phenomena that arise from the quantum interference in disordered metals.At low temperatures,they can give distinct temperature and magnetic field dependences in conductivity,allowing the symmetry of the system to be explored.In the past few years,they have also been observed in newly emergent topological materials,including topological insulators and topological semimetals.In contrast from the conventional electrons,in these new materials the quasiparticles are described as Dirac or Weyl fermions.In this article,we review our recent efforts on the theories of weak antilocalization and interaction-induced localization for Dirac and Weyl fermions in topological insulators and topological semimetals.展开更多
OBJECTIVE To identify and characterize a novel neuroprotective ShK peptide and its analogue originated from coral P.caribaeoru.METHODS P.caribaeoru was collected and subjected to transcriptome sequencing at which furt...OBJECTIVE To identify and characterize a novel neuroprotective ShK peptide and its analogue originated from coral P.caribaeoru.METHODS P.caribaeoru was collected and subjected to transcriptome sequencing at which further bioinformatics analysis had identified a unigene encoding a putative ShK protein candidate,named as PcShK1.PcShK1 and its rhodamine derivative(PcShK1-RhoB) were synthesized and tested for the neuroprotective effect in 6-OHDA induced Parkinson disease models in vitro and in vivo.Briefly,zebrafish larvae were co-exposed to 6-OHDA and various doses of the peptides;then,dopaminergic(DA) neurons immunoreactivity and locomotion behavior of the zebrafish larvae were examined.Similarly,PC12 cells were cultured with 6-OHDA in the absence or presence of different concentrations of peptides.Cell viability was determined by MTT assay while calcium flow in the PC12 cells was monitored by Fluo-4 fluorescent dye.RESULTS Compared with control group,6-OHDA treatment could lead to DA neurons loss and locomotion deficits in PD model of zebrafish larvae(P<0.01).Both PcS hK 1(2.5,5.0 and 7.5 μmol·L^(-1)) and PcS hK 1-RhoB(0.50 and 0.75 μmol·L^(-1)) were found to protect and restore dopaminergic neurons from6-OHDA mediated injury and locomotion deficiency in the PD zebrafish respectively(P<0.01).In addition,PcShK1(2.5 to 20.0 μmol·L^(-1)) and PcShK1-RhoB(0.6 to 2.5 μmol·L^(-1)) effectively prevented against 6-OHDA toxicity in PC12 cells(P<0.01).Further study revealed that they might exert their neuroprotective effects through regulating the calcium homeostasis.CONCLUSION PcS hK 1 and PcS hK 1-RhoB show neuroprotective effects on 6-OHDA induced PD models,and the underlying protective mechanisms of these peptides probably involve calcium homeostasis regulation.展开更多
For the numerical simulation of the fractional quantum Hall(FQH) effects on a finite disk, the rotational symmetry is the only symmetry that is used in diagonalizing the Hamiltonian. In this work, we propose a method ...For the numerical simulation of the fractional quantum Hall(FQH) effects on a finite disk, the rotational symmetry is the only symmetry that is used in diagonalizing the Hamiltonian. In this work, we propose a method of using the weak translational symmetry for the center of mass of the many-body system. With this approach, the bulk properties, such as the energy gap and the magneto-roton excitation are consistent with those in the closed manifolds like the sphere and torus. As an application, we consider the FQH phase and its phase transition in the fast rotated dipolar fermions. We thus demonstrate the disk geometry having versatility in analyzing the bulk properties beside the usual edge physics.展开更多
Most fluid flows in nature and engineering applications are in the state of turbulence.Turbulent motions usually exhibit a wide range of spatial and temporal scales,such as the flow of natural gas and oil in pipelines...Most fluid flows in nature and engineering applications are in the state of turbulence.Turbulent motions usually exhibit a wide range of spatial and temporal scales,such as the flow of natural gas and oil in pipelines,the wakes of cars and submarines,the boundary layer of an aircraft,the current in the ocean surface,the atmospheric boundary layer,the interstellar gas clouds(gaseous stars),and the Earth’s wake in the solar wind.Turbulence can greatly improve the heat and mass transfer efficiency of macroscopic flow.For example,chemical engineers use turbulence to mix up and homogenize fluid components and to increase chemical reaction rates in liquids or gases.However,turbulence can also lead to increases in drag,aerodynamic heat,and hydrodynamic and aerodynamic noise.For instance,the aerodynamic loading of high-speed aircraft can be significantly increased due to turbulence.展开更多
Recently, ZrTe5 has received a lot of attention as it exhibits various topological phases, such as weak and strong topological insulators, a Dirac semimetal, a three-dimensional quantum Hall state, and a quantum spin ...Recently, ZrTe5 has received a lot of attention as it exhibits various topological phases, such as weak and strong topological insulators, a Dirac semimetal, a three-dimensional quantum Hall state, and a quantum spin Hall insulator in the monolayer limit. While most of studies have been focused on the three-dimensional bulk material, it is highly desired to obtain nanostructured materials due to their advantages in device applications. We report the synthesis and characterizations of ZrTe5 nanoribbons. Via a silicon-assisted chemical vapor transport method, long nanoribbons with thickness as thin as 20 nm can be grown. The growth rate is over an order of magnitude faster than the previous method for the bulk crystals.Moreover, transport studies show that the nanoribbons are of low unintentional doping and high carrier mobility, over30000 cm2/V·s, which enable reliable determination of the Berry phase of π in the ac plane from quantum oscillations. Our method holds great potential in growth of high quality ultra-thin nanostructures of ZrTe5.展开更多
Richard Feynman once said, “I think it is safe to say that no one understands Quantum Mechanics”. The well-known article on the Einstein-Podolsky-Rosen (EPR) paradox brought forth further doubts on the interpretatio...Richard Feynman once said, “I think it is safe to say that no one understands Quantum Mechanics”. The well-known article on the Einstein-Podolsky-Rosen (EPR) paradox brought forth further doubts on the interpretation of quantum theory. Einstein’s doubt on quantum theory is a doubleedged sword: experimental verification of quantum theory would contradict the hypothesis that speed of light is finite. It has been almost a century since the creation of quantum theory and special relativity, and the relevant doubts brought forward remain unresolved. We posit that the existence of discontinuity points and quantum wormholes would imply superluminal phenomenon or infinite speed of light, which provides for an important supplement to the invariance principle of the speed of light and superluminal phenomena. This can potentially resolve the inconsistency between special relativity and quantum theory.展开更多
This paper addresses the power con- trol problems of Cognitive Radio （CR） trader transmission power and interference tempera- ture constraints. First, we propose the interfer- ence constraint which ensures that the ...This paper addresses the power con- trol problems of Cognitive Radio （CR） trader transmission power and interference tempera- ture constraints. First, we propose the interfer- ence constraint which ensures that the Quality of Service （QoS） standards for primary users is considered and a non-cooperative game power control model. Based on the proposed model, we developed a logical utility function based on the Signal-to-Interference-Noise Ratio （S/NR） and a novel algorithm network power control. that is suitable for CR Then, the existence and uniqueness of the Nash Equilibrium （NE） in our utility function are proved by the principle of game theory and the corresponding optimi- zations. Compared to traditional algorithms, the proposed one could converge to an NE in 3-5 iterative operations by setting an appropriate pricing factor. Finally, simulation results ver- ified the stability and superiority of the novel algorithm in flat-fading channel environments.展开更多
Single grit grinding is the simplified model to abstract the macro scale grinding.Finite element analysis is a strong tool to study the physical fields during a single grit grinding process,compared to experimental re...Single grit grinding is the simplified model to abstract the macro scale grinding.Finite element analysis is a strong tool to study the physical fields during a single grit grinding process,compared to experimental research.Based on the dynamic mechanical behavior of 2Cr12Ni4Mo3VNbN steel and the mathematical statistics of abrasive grit,modeling of the single grit grinding process was conducted by using commercial software AdvantEdge.The validation experiment was designed to validate the correctness of the FEA model by contrast with grinding force.The validation result shows that the FEA model can well describe the single grit grinding process.Then the grinding force and multi-physics fields were studied by experimental and simulation results.It was found that both the normal and tangential grinding forces were linearly related to the cutting speed and cutting depth.The maximum temperature is located in the subsurface of the workpiece in front of the grit,while the maximum stress and strain are located under the grit tip.The strain rate can reach as high as about 106 s–1 during the single grit grinding,which is larger than other traditional machining operations.展开更多
A sound understanding of groundwater recharged from various sources occurring at different time scales is crucial for water management in arid and semi-arid river basins. Groundwater recharge sources and their geochem...A sound understanding of groundwater recharged from various sources occurring at different time scales is crucial for water management in arid and semi-arid river basins. Groundwater recharge sources and their geochemical evolution are investigated for the Heihe River Basin （HRB） in northwest China on the basis of a comprehensive compilation of geochemical and isotopic data. Geochemical mass- balance modeling indicates that mountain-block recharge accounts for a small fraction （generally less than 5%） of the shallow and deep groundwater sustaining the oasis, whereas infiltration of rivers and irrigation water contribute most of the groundwater recharge. Dedolomitization is the primary process responsible for the changes in groundwater chemical and carbon isotope compositions from the piedmont to the groundwater discharge zone, where the dedolomitization is very likely enhanced by modern agricultural activities affecting the shallow groundwater quality. Analysis of radioactive isotopes suggests that these primary recharge sources occur at two different time scales. Radiocarbon-derived groundwater age profiles indicate a recharge rate of approximately 12 mm/year, which probably occurred during 2000-7000 years B.P., corresponding to the mid-Holocene humid period. The recharge of young groundwater on the tritium-dated time scale is much higher, about 360 mm/year in the oasis region. Infiltration from irrigation canals and irrigation return flow are the primary contributors to the increased young groundwater recharge. This study suggests that groundwater chemistry in the HRB has been influenced by the complex interaction between natural and human-induced geochemical processes and that anthropogenic effects have played a more significant role in terms of both groundwater quantity and quality.展开更多
DEAR EDITOR Protein arginine methyltransferases (PRMTs)are involved in many cellular processes via the arginine methylation of histone or non-histone proteins.We examined the expression patterns of prmt4,prmt7,and prm...DEAR EDITOR Protein arginine methyltransferases (PRMTs)are involved in many cellular processes via the arginine methylation of histone or non-histone proteins.We examined the expression patterns of prmt4,prmt7,and prmt9 during embryogenesis in Xenopus using whole-mount in situ hybridization and quantitative reverse transcription polymerase chain reaction (RT-PCR).Xenopus prmt4 and prmt7 were expressed in the neural crest,brain,and spinal cord,and also detected in the eye,branchial arches,and heart at the tailbud stage.Specific print9 signals were not detected in Xenopus embryos until the late tailbud stage when weak expression was observed in the branchial arches.Quantitative RT-PCR indicated that the expression of prmt4 and prmt7 was up-regulated during the neurula stage,whereas prmt9 maintained its low expression until the late tailbud stage,consistent with the whole-mount in situ hybridization results.Thus,the developmental expression patterns of these three print genes in Xenopus embryos provide a basis for further functional study of such genes.展开更多
The two-dimensional (2D) structure of layered transition metal dichalcogenides (TMDs) provides unusual physical properties [1,2]and chemical reactivity [3,4], which can be influenced by defects such as dislocations [5...The two-dimensional (2D) structure of layered transition metal dichalcogenides (TMDs) provides unusual physical properties [1,2]and chemical reactivity [3,4], which can be influenced by defects such as dislocations [5,6]. For example, dislocations can act as nucleation sites for the onset of deformation when subjected to stress [7].展开更多
Agriculture is a large source of carbon emissions. The cropland practices of fertilizer substitution, crop straw and conservation tillage are beneficial and help to rebuild local soil carbon stocks and reduce soil car...Agriculture is a large source of carbon emissions. The cropland practices of fertilizer substitution, crop straw and conservation tillage are beneficial and help to rebuild local soil carbon stocks and reduce soil carbon emissions, in addition to reducing the consumption of fertilizers and fossil fuels. These improved cropland practices can directly and indirectly mitigatecarbon emissions, benefiting the sustainability of croplands. For these three improved practices, we estimated carbon mitigation potentials in rice, wheat and maize croplands in China. The combined contribution of these practices to carbon mitigation was 38.8 Tg C yr-1, with fertilizer substitution, crop straw return, and conservation tillage contributing 26.6, 3.6 and 8.6 Tg C yr-1, respectively. Rice, wheat and maize croplands had potentials to mitigate 13.4, 11.9 and 15.5 Tg C yr-1, respectively, with the combined direct and indirectpotential of 33.8 and 5.0 Tg C yr-1. Because of differences in local climate and specific diets, the regional cropland carbon mitigation potentials differed greatly among provinces in China. In China, 18 provinces had a "target surplus" for which the carbon mitigation from these three practices was larger than the mitigation target set for 2020. At the national level, a net "target surplus"of 4.84 Tg C yr-1 would be attained for Chinese croplands with full implementation of the three improved practices. Regional cooperation must be developed to achieve carbon mitigation targets using such measures as carbon trading, establishing regional associations, and strengthening research programs to improve practices.展开更多
We present a qualitative and quantitative study of the magneto-thermoelectric effect of graphene. In the limit of impurity scattering length being much longer than the lattice constant, the intra-valley scattering dom...We present a qualitative and quantitative study of the magneto-thermoelectric effect of graphene. In the limit of impurity scattering length being much longer than the lattice constant, the intra-valley scattering dominates the charge and thermal transport. The self-energy and the Green＇s functions are calculated in the self-consistent Born approximation. It is found that the longitudinal thermal conductivity splits into double peaks at high Landau levels and exhibits oscillations which are out of phase with the electric conductivity. The chemical potential-dependent electrical resistivity, the thermal conductivities, the Seebeck coefficient, and the Nernst coefficient are obtained. The results are in good agreement with the experimental observations.展开更多
A brief review of commonly encountered anions,cations and co-doped HA and Ca-deficient HA was given in the DFT studies.First,the charge compensation mechanism,the preference substitution sites and crystal structure ch...A brief review of commonly encountered anions,cations and co-doped HA and Ca-deficient HA was given in the DFT studies.First,the charge compensation mechanism,the preference substitution sites and crystal structure changes of doped HA were described and discussed.And then conclusions were drawn and future challenges were discussed.The review is expected to provide theoretical guidance for the development of bioactive HA with special structures and functions.展开更多
In this paper,we propose a cooperative spectrum sharing strategy based on the Nash bargaining solution.Specifically,the primary system leases a fraction of its transmission time to the secondary system in exchange for...In this paper,we propose a cooperative spectrum sharing strategy based on the Nash bargaining solution.Specifically,the primary system leases a fraction of its transmission time to the secondary system in exchange for cooperation to improve its transmission performance.To gain access to the spectrum of the primary system,the secondary system needs to split a fraction of its transmission bandwidth to help to forward the primary signal.As a reward,the secondary system can use the remaining bandwidth to transmit its own signal.We find a unique solution for this time and bandwidth allocation using the Nash bargaining solution.Simulation results demonstrate that the performance of the primary and secondary systems can both be improved by the proposed spectrum sharing strategy.展开更多
Two-dimensional(2 D) transition metal dichalcogenides(TMDCs) have drawn intensive attention due to their ultrathin feature with excellent electrostatic gating capability, and unique thickness-dependent electronic and ...Two-dimensional(2 D) transition metal dichalcogenides(TMDCs) have drawn intensive attention due to their ultrathin feature with excellent electrostatic gating capability, and unique thickness-dependent electronic and optical properties. Controlling the thickness and doping of 2 D TMDCs are crucial toward their future applications. Here, we report an effective HAu Cl4 treatment method and achieve simultaneous thinning and doping of various TMDCs in one step. We find that the HAu Cl4 treatment not only thins thick Mo S2 flakes into few layers or even monolayers, but also simultaneously tunes Mo S2 into p-type. The effects of various parameters in the process have been studied systematically,and an Au intercalation assisted thinning and doping mechanism is proposed. Importantly, this method also works for other typical TMDCs, including WS2, Mo Se2 and WSe2,showing good universality. Electrical transport measurements of field-effect transistors(FETs) based on Mo S2 flakes show a big increase of On/Off current ratios(from 102 to 107) after the HAu Cl4 treatment. Meanwhile, the subthreshold voltages of the Mo S2 FETs shift from-60 to +27 V after the HAu Cl4 treatment, with a p-type doping behavior. This study provides an effective and simple method to control the thickness and doping properties of 2 D TMDCs, paving a way for their applications in high performance electronics and optoelectronics.展开更多
MoS2, MoSe2 and WSe2 thin flakes were fabricated by the standard micromechanical cleavage procedures. The thickness and the optical contrast of the atomic thin dichalcogenide flakes on SiO2/Si substrates were measured...MoS2, MoSe2 and WSe2 thin flakes were fabricated by the standard micromechanical cleavage procedures. The thickness and the optical contrast of the atomic thin dichalcogenide flakes on SiO2/Si substrates were measured by atomic force microscopy（AFM） and spectroscopic ellipsometer. A rapid and nondestructive method by using reflection spectra was proposed to identify the layer number of 2D layered transition metal dichalcogenides on SiO2（275 nm）/Si substrates. The contrast spectra of 2D nanosheets with different layer numbers are in agreement with theoretical calculations based on Fresnel＇s law, indicating that this method provides an unambiguous and nondestructive contrast spectra fingerprint for identifying single-and few-layered transition metal dichalcogenides. The results will greatly help in fundamental research and application.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.41625001,31660233).
文摘China is the world’s largest consumer of pork and grains.However,African swine fever(ASF)and the COVID-19 outbreak have greatly impacted the pork supply and food security in China.How can food security and the pork supply be ensured under the dual impacts of COVID-19 and ASF?This is a major problem to be urgently solved by the Chinese government.This study indicated that the main pork production and sales areas in China were separated,which reflected the spatial imbalance between the supply and demand.The total area of suitable selected sites for pig farms in China is 21.5 million ha.If only the areas with levels of high and moderate suitability are considered as potential sites for pig farms,the potential pork production can reach 56.1 million tons in China,which is slightly lower than demand.Due to the impact of the ASF epidemic,the food consumed by pigs has been reduced by 34.7 million tons.However,with increasing pork productivity in the future,the self-sufficiency rate of grains may further decline.On the premise that the quality of people’s life is not affected,the diversification of meat supply channels should be realized in an orderly and sustainable way,which might alleviate the pressure on food supply.This study provides a theoretical reference for the spatiotemporal layout of the swine industry and addresses the issue of food security in China under the influence of ASF and the COVID-19 outbreak.
基金jointly supported by The National Key Research and Development Project of China(2016YFC0600310)National Science Foundation of China(4132010400441672197 and 41302054)
文摘The Gangdese batholith, more than 2500 km in length, is composed mainly of JurassicMiocene igneous rocks. This batholith is one of the most important constituents of the Tibetan orogenesis and provides an ideal place for study of Neo-Tethyan ocean geodynamic evolution and plateau uplift. Recent studies on the Gangdese Jurassic felsic magmatism highlight its juvenile source. However, important aspects concerning the genesis of the juvenile magmatism and related deep geodynamic evolution are still unclear. Here, we report detailed petrological, geochronological, geochemical, whole-rock Sr-Nd isotopic, and in situ Sr-Hf isotopic data for a recently identified hornblende gabbro in the Dongga area, southern Lhasa sub-block. This hornblende gabbro is dominated by hornblende and plagioclase, dated at Early Jurassic（ca. 180–190 Ma）, and characterized by a narrow compositional range in SiO2（49.38wt%–52.27wt%）, MgO（4.08wt%–7.00wt%）, FeO（10.43wt%–11.77wt%）, Na2O（2.58wt%–3.51wt%）, and K2O（0.48wt%–1.53wt%）. It has depleted isotopic signatures, with whole-rock（87Sr/86Sr）i ratios of 0.7033–0.7043, εNd（t） values of ＋4.90 to ＋6.99, in situ plagioclase（87Sr/86Sr）i ratios of 0.7034–0.7042, and zircon εHf（t） of ＋12.2 to ＋16.8. Our results integrated with published data suggest a model of Gangdese juvenile crustal growth by a subduction-related water-enriched mantle wedge. The hydrous partial melting of the lithosphere mantle was triggered by the dehydration of a Neo-Tethyan oceanic slab. This mafic magmatism emplaced in the middle-lower crust of intraoceanic arcs or active continental margins, leading to Jurassic juvenile crustal growth in southern Tibet.
基金Project supported by the National Key R&D Program,China(Grant No.2016YFA0301700)the Research Grant Council,University Grants Committee,Hong Kong,China(Grant No.17303714)+1 种基金the National Natural Science Foundation of China(Grant No.11574127)the National Thousand-Young-Talents Program of China
文摘Weak localization and antilocalization are quantum transport phenomena that arise from the quantum interference in disordered metals.At low temperatures,they can give distinct temperature and magnetic field dependences in conductivity,allowing the symmetry of the system to be explored.In the past few years,they have also been observed in newly emergent topological materials,including topological insulators and topological semimetals.In contrast from the conventional electrons,in these new materials the quasiparticles are described as Dirac or Weyl fermions.In this article,we review our recent efforts on the theories of weak antilocalization and interaction-induced localization for Dirac and Weyl fermions in topological insulators and topological semimetals.
基金Science and Technology Development Fund(FDCT) of Macao SAR (FDCT / 017 / 2015 / AMJFDCT134/2014/A3).
文摘OBJECTIVE To identify and characterize a novel neuroprotective ShK peptide and its analogue originated from coral P.caribaeoru.METHODS P.caribaeoru was collected and subjected to transcriptome sequencing at which further bioinformatics analysis had identified a unigene encoding a putative ShK protein candidate,named as PcShK1.PcShK1 and its rhodamine derivative(PcShK1-RhoB) were synthesized and tested for the neuroprotective effect in 6-OHDA induced Parkinson disease models in vitro and in vivo.Briefly,zebrafish larvae were co-exposed to 6-OHDA and various doses of the peptides;then,dopaminergic(DA) neurons immunoreactivity and locomotion behavior of the zebrafish larvae were examined.Similarly,PC12 cells were cultured with 6-OHDA in the absence or presence of different concentrations of peptides.Cell viability was determined by MTT assay while calcium flow in the PC12 cells was monitored by Fluo-4 fluorescent dye.RESULTS Compared with control group,6-OHDA treatment could lead to DA neurons loss and locomotion deficits in PD model of zebrafish larvae(P<0.01).Both PcS hK 1(2.5,5.0 and 7.5 μmol·L^(-1)) and PcS hK 1-RhoB(0.50 and 0.75 μmol·L^(-1)) were found to protect and restore dopaminergic neurons from6-OHDA mediated injury and locomotion deficiency in the PD zebrafish respectively(P<0.01).In addition,PcShK1(2.5 to 20.0 μmol·L^(-1)) and PcShK1-RhoB(0.6 to 2.5 μmol·L^(-1)) effectively prevented against 6-OHDA toxicity in PC12 cells(P<0.01).Further study revealed that they might exert their neuroprotective effects through regulating the calcium homeostasis.CONCLUSION PcS hK 1 and PcS hK 1-RhoB show neuroprotective effects on 6-OHDA induced PD models,and the underlying protective mechanisms of these peptides probably involve calcium homeostasis regulation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674041,91630205,11474144,and 11847301)Chongqing Research Program of Basic Research and Frontier Technology(Grant No.cstc2017jcyjAX0084)FRF for the Central Universities(Grant No.2019CDJDWL0005)
文摘For the numerical simulation of the fractional quantum Hall(FQH) effects on a finite disk, the rotational symmetry is the only symmetry that is used in diagonalizing the Hamiltonian. In this work, we propose a method of using the weak translational symmetry for the center of mass of the many-body system. With this approach, the bulk properties, such as the energy gap and the magneto-roton excitation are consistent with those in the closed manifolds like the sphere and torus. As an application, we consider the FQH phase and its phase transition in the fast rotated dipolar fermions. We thus demonstrate the disk geometry having versatility in analyzing the bulk properties beside the usual edge physics.
基金Project supported by the National Natural Science Foundation of China(No.91752000)
文摘Most fluid flows in nature and engineering applications are in the state of turbulence.Turbulent motions usually exhibit a wide range of spatial and temporal scales,such as the flow of natural gas and oil in pipelines,the wakes of cars and submarines,the boundary layer of an aircraft,the current in the ocean surface,the atmospheric boundary layer,the interstellar gas clouds(gaseous stars),and the Earth’s wake in the solar wind.Turbulence can greatly improve the heat and mass transfer efficiency of macroscopic flow.For example,chemical engineers use turbulence to mix up and homogenize fluid components and to increase chemical reaction rates in liquids or gases.However,turbulence can also lead to increases in drag,aerodynamic heat,and hydrodynamic and aerodynamic noise.For instance,the aerodynamic loading of high-speed aircraft can be significantly increased due to turbulence.
基金National Key Research and Development Program of China(Grant Nos.2016YFA0300600,2016YFA0300802,2013CB932904,and 2016YFA0202500)the National Natural Science Foundation of China(Grant Nos.11574005,11774009,and 11234001).
文摘Recently, ZrTe5 has received a lot of attention as it exhibits various topological phases, such as weak and strong topological insulators, a Dirac semimetal, a three-dimensional quantum Hall state, and a quantum spin Hall insulator in the monolayer limit. While most of studies have been focused on the three-dimensional bulk material, it is highly desired to obtain nanostructured materials due to their advantages in device applications. We report the synthesis and characterizations of ZrTe5 nanoribbons. Via a silicon-assisted chemical vapor transport method, long nanoribbons with thickness as thin as 20 nm can be grown. The growth rate is over an order of magnitude faster than the previous method for the bulk crystals.Moreover, transport studies show that the nanoribbons are of low unintentional doping and high carrier mobility, over30000 cm2/V·s, which enable reliable determination of the Berry phase of π in the ac plane from quantum oscillations. Our method holds great potential in growth of high quality ultra-thin nanostructures of ZrTe5.
文摘Richard Feynman once said, “I think it is safe to say that no one understands Quantum Mechanics”. The well-known article on the Einstein-Podolsky-Rosen (EPR) paradox brought forth further doubts on the interpretation of quantum theory. Einstein’s doubt on quantum theory is a doubleedged sword: experimental verification of quantum theory would contradict the hypothesis that speed of light is finite. It has been almost a century since the creation of quantum theory and special relativity, and the relevant doubts brought forward remain unresolved. We posit that the existence of discontinuity points and quantum wormholes would imply superluminal phenomenon or infinite speed of light, which provides for an important supplement to the invariance principle of the speed of light and superluminal phenomena. This can potentially resolve the inconsistency between special relativity and quantum theory.
基金partially supported by the National Natural Science Foundation of China under Grant No.61172073the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University under Grant No.2012D19+1 种基金the Fundamental Research Funds for the Central Universities,Beijing Jiaotong University under Grant No.2013JBZ01the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No.NCET-12-0766
文摘This paper addresses the power con- trol problems of Cognitive Radio （CR） trader transmission power and interference tempera- ture constraints. First, we propose the interfer- ence constraint which ensures that the Quality of Service （QoS） standards for primary users is considered and a non-cooperative game power control model. Based on the proposed model, we developed a logical utility function based on the Signal-to-Interference-Noise Ratio （S/NR） and a novel algorithm network power control. that is suitable for CR Then, the existence and uniqueness of the Nash Equilibrium （NE） in our utility function are proved by the principle of game theory and the corresponding optimi- zations. Compared to traditional algorithms, the proposed one could converge to an NE in 3-5 iterative operations by setting an appropriate pricing factor. Finally, simulation results ver- ified the stability and superiority of the novel algorithm in flat-fading channel environments.
基金Projects(U1537202,51575305)supported by the National Natural Science Foundation of ChinaProject(61328302)supported by National Security Major Basic Research Program of China
文摘Single grit grinding is the simplified model to abstract the macro scale grinding.Finite element analysis is a strong tool to study the physical fields during a single grit grinding process,compared to experimental research.Based on the dynamic mechanical behavior of 2Cr12Ni4Mo3VNbN steel and the mathematical statistics of abrasive grit,modeling of the single grit grinding process was conducted by using commercial software AdvantEdge.The validation experiment was designed to validate the correctness of the FEA model by contrast with grinding force.The validation result shows that the FEA model can well describe the single grit grinding process.Then the grinding force and multi-physics fields were studied by experimental and simulation results.It was found that both the normal and tangential grinding forces were linearly related to the cutting speed and cutting depth.The maximum temperature is located in the subsurface of the workpiece in front of the grit,while the maximum stress and strain are located under the grit tip.The strain rate can reach as high as about 106 s–1 during the single grit grinding,which is larger than other traditional machining operations.
基金supported by the National Natural Science Foundation of China(Grant Nos.91225301 and 91425303)
文摘A sound understanding of groundwater recharged from various sources occurring at different time scales is crucial for water management in arid and semi-arid river basins. Groundwater recharge sources and their geochemical evolution are investigated for the Heihe River Basin （HRB） in northwest China on the basis of a comprehensive compilation of geochemical and isotopic data. Geochemical mass- balance modeling indicates that mountain-block recharge accounts for a small fraction （generally less than 5%） of the shallow and deep groundwater sustaining the oasis, whereas infiltration of rivers and irrigation water contribute most of the groundwater recharge. Dedolomitization is the primary process responsible for the changes in groundwater chemical and carbon isotope compositions from the piedmont to the groundwater discharge zone, where the dedolomitization is very likely enhanced by modern agricultural activities affecting the shallow groundwater quality. Analysis of radioactive isotopes suggests that these primary recharge sources occur at two different time scales. Radiocarbon-derived groundwater age profiles indicate a recharge rate of approximately 12 mm/year, which probably occurred during 2000-7000 years B.P., corresponding to the mid-Holocene humid period. The recharge of young groundwater on the tritium-dated time scale is much higher, about 360 mm/year in the oasis region. Infiltration from irrigation canals and irrigation return flow are the primary contributors to the increased young groundwater recharge. This study suggests that groundwater chemistry in the HRB has been influenced by the complex interaction between natural and human-induced geochemical processes and that anthropogenic effects have played a more significant role in terms of both groundwater quantity and quality.
基金supported by grants from the Research Grants Council of Hong Kong CUHK14167017,CUHK24100414 to H.Z.the Shenzhen Innovation Committee of Science and Technology grants(JCYJ20150331101823691)Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research(2017B030301018)to Y.D
文摘DEAR EDITOR Protein arginine methyltransferases (PRMTs)are involved in many cellular processes via the arginine methylation of histone or non-histone proteins.We examined the expression patterns of prmt4,prmt7,and prmt9 during embryogenesis in Xenopus using whole-mount in situ hybridization and quantitative reverse transcription polymerase chain reaction (RT-PCR).Xenopus prmt4 and prmt7 were expressed in the neural crest,brain,and spinal cord,and also detected in the eye,branchial arches,and heart at the tailbud stage.Specific print9 signals were not detected in Xenopus embryos until the late tailbud stage when weak expression was observed in the branchial arches.Quantitative RT-PCR indicated that the expression of prmt4 and prmt7 was up-regulated during the neurula stage,whereas prmt9 maintained its low expression until the late tailbud stage,consistent with the whole-mount in situ hybridization results.Thus,the developmental expression patterns of these three print genes in Xenopus embryos provide a basis for further functional study of such genes.
基金supported by the National Key R&D Program of China[Nos.2018YFB1304902,2016YFA0300804,2016YFA0300903]the National Natural Science Foundation of China[Nos.51672007,11974023,11904372,11704389,U1813211]+3 种基金the Key-Area Research and Development Program of Guang Dong Province[Nos.2018B030327001,2018B010109009]the‘‘2011 Program”Peking-Tsinghua-IOP Collaborative Innovation Center of Quantum Matterthe Beijing Institute of Technology Research Fund Program for Young Scholarsthe Beijing Institute of Technology laboratory research project[No.2019BITSYA03]。
文摘The two-dimensional (2D) structure of layered transition metal dichalcogenides (TMDs) provides unusual physical properties [1,2]and chemical reactivity [3,4], which can be influenced by defects such as dislocations [5,6]. For example, dislocations can act as nucleation sites for the onset of deformation when subjected to stress [7].
基金supported by the National Science and Technology Major Project(2015ZX07203-005)the National Program for Support of Top-notch Young Professionals
文摘Agriculture is a large source of carbon emissions. The cropland practices of fertilizer substitution, crop straw and conservation tillage are beneficial and help to rebuild local soil carbon stocks and reduce soil carbon emissions, in addition to reducing the consumption of fertilizers and fossil fuels. These improved cropland practices can directly and indirectly mitigatecarbon emissions, benefiting the sustainability of croplands. For these three improved practices, we estimated carbon mitigation potentials in rice, wheat and maize croplands in China. The combined contribution of these practices to carbon mitigation was 38.8 Tg C yr-1, with fertilizer substitution, crop straw return, and conservation tillage contributing 26.6, 3.6 and 8.6 Tg C yr-1, respectively. Rice, wheat and maize croplands had potentials to mitigate 13.4, 11.9 and 15.5 Tg C yr-1, respectively, with the combined direct and indirectpotential of 33.8 and 5.0 Tg C yr-1. Because of differences in local climate and specific diets, the regional cropland carbon mitigation potentials differed greatly among provinces in China. In China, 18 provinces had a "target surplus" for which the carbon mitigation from these three practices was larger than the mitigation target set for 2020. At the national level, a net "target surplus"of 4.84 Tg C yr-1 would be attained for Chinese croplands with full implementation of the three improved practices. Regional cooperation must be developed to achieve carbon mitigation targets using such measures as carbon trading, establishing regional associations, and strengthening research programs to improve practices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274013 and 11774006)the National Basic Research Program of China(2012CB921300)the Australian Research Council Grant(Grant No.DP160101474)
文摘We present a qualitative and quantitative study of the magneto-thermoelectric effect of graphene. In the limit of impurity scattering length being much longer than the lattice constant, the intra-valley scattering dominates the charge and thermal transport. The self-energy and the Green＇s functions are calculated in the self-consistent Born approximation. It is found that the longitudinal thermal conductivity splits into double peaks at high Landau levels and exhibits oscillations which are out of phase with the electric conductivity. The chemical potential-dependent electrical resistivity, the thermal conductivities, the Seebeck coefficient, and the Nernst coefficient are obtained. The results are in good agreement with the experimental observations.
基金Funded by the the National High Technology Research and Development Program("863"Program)(2015AA034202)the National Key Research and Development Program of China(2016YFB0700802)+4 种基金the Key Technology Research and Development Program of the Bureau of Science and Technology of Sichuan Province(2014GZ0174)the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase)(U1501501)the Education Department Program of Sichuan province(16ZB0313)the Teaching Reform Program of Mianyang Teachers’College(Mnu-JY1512)the Innovation and Entrepreneurship Training Program of University Students in Sichuan Province(201610639077)
文摘A brief review of commonly encountered anions,cations and co-doped HA and Ca-deficient HA was given in the DFT studies.First,the charge compensation mechanism,the preference substitution sites and crystal structure changes of doped HA were described and discussed.And then conclusions were drawn and future challenges were discussed.The review is expected to provide theoretical guidance for the development of bioactive HA with special structures and functions.
基金supported by the National Natural Science Foundation of China under Grants No.61372087,No.61303235the Zhejiang Leading Team of Science and Technology Innovation on Modem Communication and Network System under Grant No.2010R50011the Project of the Zhejiang Provincial Science and Technology Department under Grant No.Y201329389
文摘In this paper,we propose a cooperative spectrum sharing strategy based on the Nash bargaining solution.Specifically,the primary system leases a fraction of its transmission time to the secondary system in exchange for cooperation to improve its transmission performance.To gain access to the spectrum of the primary system,the secondary system needs to split a fraction of its transmission bandwidth to help to forward the primary signal.As a reward,the secondary system can use the remaining bandwidth to transmit its own signal.We find a unique solution for this time and bandwidth allocation using the Nash bargaining solution.Simulation results demonstrate that the performance of the primary and secondary systems can both be improved by the proposed spectrum sharing strategy.
基金support from the National Natural Science Foundation of China (51722206 and 11674150)the Youth 1000-Talent Program of China+3 种基金the Economic, Trade and Information Commission of Shenzhen Municipality for the “2017 Graphene Manufacturing Innovation Center Project” (201901171523)Shenzhen Basic Research Project (JCYJ20170307140956657 and JCYJ20160613160524999)Guangdong Innovative and Entrepreneurial Research Team Program (2017ZT07C341 and 2016ZT06D348)the Development and Reform Commission of Shenzhen Municipality for the development of the “Low-Dimensional Materials and Devices” discipline
文摘Two-dimensional(2 D) transition metal dichalcogenides(TMDCs) have drawn intensive attention due to their ultrathin feature with excellent electrostatic gating capability, and unique thickness-dependent electronic and optical properties. Controlling the thickness and doping of 2 D TMDCs are crucial toward their future applications. Here, we report an effective HAu Cl4 treatment method and achieve simultaneous thinning and doping of various TMDCs in one step. We find that the HAu Cl4 treatment not only thins thick Mo S2 flakes into few layers or even monolayers, but also simultaneously tunes Mo S2 into p-type. The effects of various parameters in the process have been studied systematically,and an Au intercalation assisted thinning and doping mechanism is proposed. Importantly, this method also works for other typical TMDCs, including WS2, Mo Se2 and WSe2,showing good universality. Electrical transport measurements of field-effect transistors(FETs) based on Mo S2 flakes show a big increase of On/Off current ratios(from 102 to 107) after the HAu Cl4 treatment. Meanwhile, the subthreshold voltages of the Mo S2 FETs shift from-60 to +27 V after the HAu Cl4 treatment, with a p-type doping behavior. This study provides an effective and simple method to control the thickness and doping properties of 2 D TMDCs, paving a way for their applications in high performance electronics and optoelectronics.
基金financially supported by the National Natural Science Foundation of China(Nos.11304381 and 11174366)
文摘MoS2, MoSe2 and WSe2 thin flakes were fabricated by the standard micromechanical cleavage procedures. The thickness and the optical contrast of the atomic thin dichalcogenide flakes on SiO2/Si substrates were measured by atomic force microscopy（AFM） and spectroscopic ellipsometer. A rapid and nondestructive method by using reflection spectra was proposed to identify the layer number of 2D layered transition metal dichalcogenides on SiO2（275 nm）/Si substrates. The contrast spectra of 2D nanosheets with different layer numbers are in agreement with theoretical calculations based on Fresnel＇s law, indicating that this method provides an unambiguous and nondestructive contrast spectra fingerprint for identifying single-and few-layered transition metal dichalcogenides. The results will greatly help in fundamental research and application.
