We explore some necessary and sufficient conditions for the boundedness of the Forelli-Rudin type operator T on the weighted Lebesgue space associated with tubular domains over the forward light cone.Our approach invo...We explore some necessary and sufficient conditions for the boundedness of the Forelli-Rudin type operator T on the weighted Lebesgue space associated with tubular domains over the forward light cone.Our approach involves conducting precise computations for a series of complex integrals to identify appropriate test functions,and through a detailed analysis of these test functions,we derive the boundedness properties of the operator T.This work is significant in the study of the Bergman projection operators.展开更多
Novel headstand pyrocarbon cones （HPCs） with hollow structure were developed on the surfaces of pyrocarbon layers of the carbon/carbon （C/C） composites at 650-750 °C by the electromagnetic-field-assisted chem...Novel headstand pyrocarbon cones （HPCs） with hollow structure were developed on the surfaces of pyrocarbon layers of the carbon/carbon （C/C） composites at 650-750 °C by the electromagnetic-field-assisted chemical vapor deposition in the absence of catalysts. The fine microstructures of the HPCs were characterized by high-resolution transmission electron microscopy. The results show that the textural features of the HPCs directly transfer from turbostratic structure in roots to a well-ordered high texture in stems. And the degree of high texture ordering decreases gradually from the stem to the tail of the HPCs. The formation mechanism of the HPCs was inferred as the comprehensive effect of polarization induction on electromagnetic fields and particle-filler property under disruptive discharge.展开更多
Flexible spinning is a new type of spinning process where spin-forming isperformed without using a mandrel. Combining shearing and rolling processes, the calculationformulas of the spinning forces in flexible spinning...Flexible spinning is a new type of spinning process where spin-forming isperformed without using a mandrel. Combining shearing and rolling processes, the calculationformulas of the spinning forces in flexible spinning of cones is presented. The effects of the mainprocessing parameters, such as gripping force G applied to the blank by the inner roller, the feedrate of rollers f and the roundness radius of outer roller r_o, on the spinning forces are analyzedexperimentally and theoretically.展开更多
For direct numerical simulation （DNS） of turbulent boundary layers, generation of an appropriate inflow condition needs to be considered. This paper proposes a method, with which the inflow condition for spatial-mod...For direct numerical simulation （DNS） of turbulent boundary layers, generation of an appropriate inflow condition needs to be considered. This paper proposes a method, with which the inflow condition for spatial-mode DNS of turbulent boundary layers on supersonic blunt cones with different Mach numbers, Reynolds numbers and wall temperature conditions can be generated. This is based only on a given instant flow field obtained by a temporal-mode DNS of a turbulent boundary layer on a flat plate. Effectiveness of the method is shown in three typical examples by comparing the results with those obtained by other methods.展开更多
Oceanic plateaus are large igneous provinces in the oceans,created by massive underwater eruptions,but their late-stage volcanism is poorly understood.With the addition of recent high-quality bathymetric data to exist...Oceanic plateaus are large igneous provinces in the oceans,created by massive underwater eruptions,but their late-stage volcanism is poorly understood.With the addition of recent high-quality bathymetric data to existing data,286 secondary cones were discovered over Shatsky Rise oceanic plateau.These cones with steeper flank slopes(mean 6.1°±4.4°)and smaller sizes(102–1923 m in height)are morphologically distinct from the plateau,and they are thought to have formed after the main volcanic episodes.Cone height and characteristic height(420 m)are close to seamounts in the Pacific Ocean,whereas greater than those in the Atlantic Ocean.Mean flatness of Shatsky Rise’s cones(0.25±0.20)are similar to that of seamounts in both Pacific and Atlantic Oceans,but notably density in cone distribution(0.56 km^-3)and their mean slope are significantly lower than those of seamounts in the two oceans.Lower slopes of secondary cones within Shatsky Rise may be explained by higher effusion rates of remaining magma.Although cone formation was expected to have a link to rifting by seafloor spreading,weak relationship between cone orientation and magnetic anomaly pattern implies that the expectation is negative.Moreover,weak correlation between the cone height and depth indicates it is not true that volcanic cones grow taller when they occur closer to the massif summits with thicker oceanic crust,which was suggested as the increase in hydraulic pressure.Cone height and flatness are also not strongly related,implying that remaining magma supply was too limited to foster the cones to critical height.展开更多
In this paper, the authors investigate the invariant cones of quadratic homoge- neous polynomial vector fields in three variables. Necessary and sufficient conditions for the existence of non-isolated invariant closed...In this paper, the authors investigate the invariant cones of quadratic homoge- neous polynomial vector fields in three variables. Necessary and sufficient conditions for the existence of non-isolated invariant closed cones are obtained by the algebraic expressions in terms of the coefficients of certain quadratic homogeneous polynomials.展开更多
By using the theory of Euclidean Jordan algebras,based on a new class of smoothing functions,the QiSun-Zhou's smoothing Newton algorithm is extended to solve linear programming over symmetric cones(SCLP).The algor...By using the theory of Euclidean Jordan algebras,based on a new class of smoothing functions,the QiSun-Zhou's smoothing Newton algorithm is extended to solve linear programming over symmetric cones(SCLP).The algorithm is globally convergent under suitable assumptions.展开更多
Based on the Ref [9]the displacement and stress distributions in a spherically isotropic cone subjected to concentrated loads at apex are studied The displacementand stresses are given explicitly for the cone in compr...Based on the Ref [9]the displacement and stress distributions in a spherically isotropic cone subjected to concentrated loads at apex are studied The displacementand stresses are given explicitly for the cone in compression torsion and bending cases respectively based on the situation of the concentrated forces and moments Finally.the hollow cone problems are discussed .展开更多
The author gives a dual characterization of solid cones in locally convex spaces. From this the author obtains some criteria for judging convex cones to be solid in various kinds of locally convex spaces. Using a gene...The author gives a dual characterization of solid cones in locally convex spaces. From this the author obtains some criteria for judging convex cones to be solid in various kinds of locally convex spaces. Using a general expression of the interior of a solid cone, the author obtains a number of necessary and sufficient conditions for convex cones to be solid in the framework of Banach spaces. In particular, the author gives a dual relationship between solid cones and generalized sharp cones. The related known results are improved and extended.展开更多
Groundwater in Yinchuan City has been heavily over-exploited, thus leading to the formation of depression cones in confined and phreatic groundwater environments. The depression cones have an important influence on th...Groundwater in Yinchuan City has been heavily over-exploited, thus leading to the formation of depression cones in confined and phreatic groundwater environments. The depression cones have an important influence on the hydrodynamic and hydrochemical fields of groundwaters. The evolution of depression cones was analyzed on the basis of the monitoring data on groundwater level accumulated in the past 14 years. The ratio of rCl-/rCa2+ showed that phreatic water circulation was intensified, and confined groundwater was affected by external factors. Mass balance of Cl- showed confined water mixed with about 11% phreatic water. It is shown that the alternative function of confined water was affected by external factors. At last, the evolution of groundwater hydrochemical field on the basis of groundwater chemical composition showed that phreatic water quality has been improved whereas confined water quality has been deteriorated. Saturation indices of minerals with respect to phreatic and confined waters were calculated by using PHREEQC.展开更多
Stem implants of acephate were tentatively used to contfol cone and seed insects in Northeastern China in 1993. Experiments considered in a Siberian larch seed orchard and mother-tree stands of Korean pine and Korean ...Stem implants of acephate were tentatively used to contfol cone and seed insects in Northeastern China in 1993. Experiments considered in a Siberian larch seed orchard and mother-tree stands of Korean pine and Korean spruce that promising control of major cone pests, including cone tlies, cone-worms and seed-worms, was obtained in all of the conifer species but treatment did not reduce significantly damage due to seed chalcids. Acephate implants did not seem to affect seed germination.展开更多
Two species of cone flies (Strobilomyia anthracina andS. svenssoni) emerged from puparia were collected under Siberian spruce (Picea obovata) trees in the central part of the Krasnoyarsk region, central Siberia. Paras...Two species of cone flies (Strobilomyia anthracina andS. svenssoni) emerged from puparia were collected under Siberian spruce (Picea obovata) trees in the central part of the Krasnoyarsk region, central Siberia. Parasites of the Figitidae and Braconidae families emerged from 28.1% of the puparia, and fungal and bacterial diseases destroyed 24.8% of the puparia. Weight and length of the puparia depended on the sanitary status. Two types of cone fly eggs were observed on spruce cones. At least three species ofStrobilomyia (S. Infrequens, S. laricicola, and S. sibirica) attacked cones of Siberian larch (Larix sibirica) in central Siberia.展开更多
A simple rule for finding Dirac cone electronic states in solids is proposed, which is neglecting those lattice atoms inert to particular electronic bands, and pursuing the two-dimensional(2D) graphene-like quasi-atom...A simple rule for finding Dirac cone electronic states in solids is proposed, which is neglecting those lattice atoms inert to particular electronic bands, and pursuing the two-dimensional(2D) graphene-like quasi-atom lattices with s-and pbindings by considering the equivalent atom groups in the unit cell as quasi-atoms.Taking CsPbBr3 and Cs3Bi2Br9 bilayers as examples, we prove the effectiveness and generality of this rule with the density functional theory(DFT) calculations.We demonstrate that both bilayers have Dirac cones around the Fermi level and reveal that their corresponding Fermi velocities can reach as high as^0.2 × 10^6 m/s.This makes these new 2D layered materials very promising in making new ultra-fast ionic electronic devices.展开更多
Experimental quasi-static crushing tests were conducted by using a universal testing machine format kenaf-epoxy composite elliptical cones. The work focused on the vertex angle's effects on energy absorption capab...Experimental quasi-static crushing tests were conducted by using a universal testing machine format kenaf-epoxy composite elliptical cones. The work focused on the vertex angle's effects on energy absorption capability; the vertex angles vary from 0° to 24° in 6 increments. The failure modes of the kenaf fibre epoxy composite elliptical cones were observed utilising delegate photos taken during the quasistatic crushing test. Load-deformation curves and deformation histories of typical specimens are presented and discussed. Moreover, the effects of cone vertex angles on the load carrying capacity and the energy absorption capability are also discussed. The results show that the energy absorption abilities significantly influence the ellipticity vertex angle as the load carrying capacity. We concluded that the quasi-static axial crushing behaviour of elliptical mat laminated composite cones is strongly affected by their structural geometry and the specific energy absorbed by the composite elliptical cones with vertex angles of 6°, 12°, 18°, and 24°, which is more than an elliptical cone with the vertex angle of 0°(the elliptical tube) at any given deformation. However, the specific energy absorption for the elliptical composite cone showed a positive correlation, i.e., the more the angle increased, the more energy was absorbed. In this regard, an elliptical composite cone with a 24° angle exhibited the best energy absorption capability.展开更多
By Ar+ sputtering onto Si wafers which were surrounded by Mo plates, uniform cones over a large area on the Si surface were formed. Scanning electron microscopic study showed that the cones were formed on the entire s...By Ar+ sputtering onto Si wafers which were surrounded by Mo plates, uniform cones over a large area on the Si surface were formed. Scanning electron microscopic study showed that the cones were formed on the entire surface of the Si wafer. The dimensions of the uniform cones were one micrometer in diameter and 5-6 micrometers high. They were further characterized by means of cross-sectional transmission electron microscopy, with the technique of micro-diffractions. It was found that the cone contained a pure Si regime and a Mo-rich regime. In the binary Mo-Si zone, we identified three distinct areas vertically: (1) domains of Mo-induced Si ordered structures, (2) a small volume of a new Mo3Si2 structural variant, intergrown with the Si ordered structure, and (3) a small amount of pure Mo nanoparticles covering the surface of the cones. The formation of the large and uniform cones may provide a new surface configuration for potential applications in surface science and technology.展开更多
Two-dimensional materials with Dirac cones have significant applications in photoelectric technology. The origin and manipulation of multiple Dirac cones need to be better understood. By first-principle calculations, ...Two-dimensional materials with Dirac cones have significant applications in photoelectric technology. The origin and manipulation of multiple Dirac cones need to be better understood. By first-principle calculations, we study the influence of external fields on the electronic structure of the hexagonal CrB4 sheet with double nonequivalent Dirac cones. Our results show that the two cones are not sensitive to tensile strain and out-of-plane electric field, but present obviously different behaviors under the in-plane external electric field（along the B-B direction）, i.e., one cone holds while the other vanishes with a gap opening. More interestingly, a new nonequivalent cone emerges under a proper in-plane electric field. We also discuss the origin of the cones in CrB4 sheet. Our study provides a new method on how to obtain Dirac cones by the external field manipulation, which may motivate potential applications in nanoelectronics.展开更多
Well-preserved Ginkgo pollen organs are analyzed from the Middle Jurassic Xishanyao Formation of the Turpan–Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China, and are described as a new species, Ginkgo...Well-preserved Ginkgo pollen organs are analyzed from the Middle Jurassic Xishanyao Formation of the Turpan–Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China, and are described as a new species, Ginkgo hamiensis Z.X. Wang et B.N. Sun sp. nov. The immature male cones are cylindrical and catkin-like, with two longitudinal stripes on the stalk. The pollen sacs are shaped like a long oval with two pollen sacs fused together for each microsporophyll, and the microsporophyll tip is a triangular cystidium. The pollen grains are oblong or fusiform and monocolpate; both ends are blunt or sharp. By comparison with previously reported fossil records of Ginkgo plants, we determined that the current fossils are different from all other reported species; thus, the present fossil is referred to as a new species of Ginkgo. The reproductive organs of the Ginkgo fossils described herein can provide valuable information for the study of Ginkgo plants. Further, there are two probable evolutionary trends in the Ginkgo pollen cones. One trend is that the number of pollen sacs changed from three or four during the Jurassic and Cretaceous to two at the present day; the other is that the number of pollen sacs has remained two from the Middle Jurassic to the present day. In addition, the pollen cones described herein are similar to the pollen cones of the extant Ginkgo, which strongly indicates that the morphology of Ginkgo plants may have remained highly conserved over millions of years.展开更多
It is well established that guidance of axons during neuronal development is regulated by a variety of extracellular signals,governing cytoskeletal dynamics in growth cones.The actin and microtubule（MT）cytoskeleton ...It is well established that guidance of axons during neuronal development is regulated by a variety of extracellular signals,governing cytoskeletal dynamics in growth cones.The actin and microtubule（MT）cytoskeleton have both been shown to play important roles.However,a growing body of work suggests that a critical issue is the proper coordination of changes within these two major cytoskeletal systems（reviewed in Cammara-ta et al., 2016）.展开更多
The paper presents the results of biometrical study of the seeds and cones of larch taxa from Northeast of China. Fourteen characters are considered and their analyses showed that the seeds and cones of the larch taxa...The paper presents the results of biometrical study of the seeds and cones of larch taxa from Northeast of China. Fourteen characters are considered and their analyses showed that the seeds and cones of the larch taxa were relative greatly variable. Cluster analysis and principal component analysis for all 6 larch taxa were made. The analysis results proved that the dominant larch population in Toudao Farm fell within the range of variation ofLarix olgensis. The key taxonomic characters are the length of seed wing, length of cone, length of seed, the length/width ratio of seed and number of scales.展开更多
基金Liu’s research was supported by the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(31610030)Deng’s research was supported by the NSFC(11971042,12071035)the National Key R&D Program of China(2021YFA1002600).
文摘We explore some necessary and sufficient conditions for the boundedness of the Forelli-Rudin type operator T on the weighted Lebesgue space associated with tubular domains over the forward light cone.Our approach involves conducting precise computations for a series of complex integrals to identify appropriate test functions,and through a detailed analysis of these test functions,we derive the boundedness properties of the operator T.This work is significant in the study of the Bergman projection operators.
基金Project (2011CB605801) supported by the National Basic Research Program of ChinaProject (2011M500127) supported by the China Postdoctoral Science Foundation+1 种基金Projects (50802115, 51102089) supported by the National Natural Science Foundation of ChinaProject supported by the Postdoctoral Fund of the Central South University, China
文摘Novel headstand pyrocarbon cones （HPCs） with hollow structure were developed on the surfaces of pyrocarbon layers of the carbon/carbon （C/C） composites at 650-750 °C by the electromagnetic-field-assisted chemical vapor deposition in the absence of catalysts. The fine microstructures of the HPCs were characterized by high-resolution transmission electron microscopy. The results show that the textural features of the HPCs directly transfer from turbostratic structure in roots to a well-ordered high texture in stems. And the degree of high texture ordering decreases gradually from the stem to the tail of the HPCs. The formation mechanism of the HPCs was inferred as the comprehensive effect of polarization induction on electromagnetic fields and particle-filler property under disruptive discharge.
文摘Flexible spinning is a new type of spinning process where spin-forming isperformed without using a mandrel. Combining shearing and rolling processes, the calculationformulas of the spinning forces in flexible spinning of cones is presented. The effects of the mainprocessing parameters, such as gripping force G applied to the blank by the inner roller, the feedrate of rollers f and the roundness radius of outer roller r_o, on the spinning forces are analyzedexperimentally and theoretically.
基金the National Natural Science Foundation of China(Nos.10632050,90716007)the Special Foundation for the Authors of National Excellent Doctoral Dissertations(No.200328)
文摘For direct numerical simulation （DNS） of turbulent boundary layers, generation of an appropriate inflow condition needs to be considered. This paper proposes a method, with which the inflow condition for spatial-mode DNS of turbulent boundary layers on supersonic blunt cones with different Mach numbers, Reynolds numbers and wall temperature conditions can be generated. This is based only on a given instant flow field obtained by a temporal-mode DNS of a turbulent boundary layer on a flat plate. Effectiveness of the method is shown in three typical examples by comparing the results with those obtained by other methods.
基金supported by the National Key R&D Program of China (No. 2018YFC0309800)the National Natural Science Foundation of China (Nos. 91628301, U1606401, 41606069, 41776058)+2 种基金the Natural Science Foundation of Guangdong Province in China (No. 2017A030313243)the Chinese Academy of Sciences (Nos. Y4SL021001, QYZDY-SSWDQC005)the China Association of Marine Affairs (No. CAMAZD201714)
文摘Oceanic plateaus are large igneous provinces in the oceans,created by massive underwater eruptions,but their late-stage volcanism is poorly understood.With the addition of recent high-quality bathymetric data to existing data,286 secondary cones were discovered over Shatsky Rise oceanic plateau.These cones with steeper flank slopes(mean 6.1°±4.4°)and smaller sizes(102–1923 m in height)are morphologically distinct from the plateau,and they are thought to have formed after the main volcanic episodes.Cone height and characteristic height(420 m)are close to seamounts in the Pacific Ocean,whereas greater than those in the Atlantic Ocean.Mean flatness of Shatsky Rise’s cones(0.25±0.20)are similar to that of seamounts in both Pacific and Atlantic Oceans,but notably density in cone distribution(0.56 km^-3)and their mean slope are significantly lower than those of seamounts in the two oceans.Lower slopes of secondary cones within Shatsky Rise may be explained by higher effusion rates of remaining magma.Although cone formation was expected to have a link to rifting by seafloor spreading,weak relationship between cone orientation and magnetic anomaly pattern implies that the expectation is negative.Moreover,weak correlation between the cone height and depth indicates it is not true that volcanic cones grow taller when they occur closer to the massif summits with thicker oceanic crust,which was suggested as the increase in hydraulic pressure.Cone height and flatness are also not strongly related,implying that remaining magma supply was too limited to foster the cones to critical height.
文摘In this paper, the authors investigate the invariant cones of quadratic homoge- neous polynomial vector fields in three variables. Necessary and sufficient conditions for the existence of non-isolated invariant closed cones are obtained by the algebraic expressions in terms of the coefficients of certain quadratic homogeneous polynomials.
基金Supported by Liu Hui Centre for Applied Mathematics,Nankai University and Tianjin University
文摘By using the theory of Euclidean Jordan algebras,based on a new class of smoothing functions,the QiSun-Zhou's smoothing Newton algorithm is extended to solve linear programming over symmetric cones(SCLP).The algorithm is globally convergent under suitable assumptions.
文摘Based on the Ref [9]the displacement and stress distributions in a spherically isotropic cone subjected to concentrated loads at apex are studied The displacementand stresses are given explicitly for the cone in compression torsion and bending cases respectively based on the situation of the concentrated forces and moments Finally.the hollow cone problems are discussed .
基金the National Natural Science Foundation of China(10571035)
文摘The author gives a dual characterization of solid cones in locally convex spaces. From this the author obtains some criteria for judging convex cones to be solid in various kinds of locally convex spaces. Using a general expression of the interior of a solid cone, the author obtains a number of necessary and sufficient conditions for convex cones to be solid in the framework of Banach spaces. In particular, the author gives a dual relationship between solid cones and generalized sharp cones. The related known results are improved and extended.
文摘Groundwater in Yinchuan City has been heavily over-exploited, thus leading to the formation of depression cones in confined and phreatic groundwater environments. The depression cones have an important influence on the hydrodynamic and hydrochemical fields of groundwaters. The evolution of depression cones was analyzed on the basis of the monitoring data on groundwater level accumulated in the past 14 years. The ratio of rCl-/rCa2+ showed that phreatic water circulation was intensified, and confined groundwater was affected by external factors. Mass balance of Cl- showed confined water mixed with about 11% phreatic water. It is shown that the alternative function of confined water was affected by external factors. At last, the evolution of groundwater hydrochemical field on the basis of groundwater chemical composition showed that phreatic water quality has been improved whereas confined water quality has been deteriorated. Saturation indices of minerals with respect to phreatic and confined waters were calculated by using PHREEQC.
文摘Stem implants of acephate were tentatively used to contfol cone and seed insects in Northeastern China in 1993. Experiments considered in a Siberian larch seed orchard and mother-tree stands of Korean pine and Korean spruce that promising control of major cone pests, including cone tlies, cone-worms and seed-worms, was obtained in all of the conifer species but treatment did not reduce significantly damage due to seed chalcids. Acephate implants did not seem to affect seed germination.
文摘Two species of cone flies (Strobilomyia anthracina andS. svenssoni) emerged from puparia were collected under Siberian spruce (Picea obovata) trees in the central part of the Krasnoyarsk region, central Siberia. Parasites of the Figitidae and Braconidae families emerged from 28.1% of the puparia, and fungal and bacterial diseases destroyed 24.8% of the puparia. Weight and length of the puparia depended on the sanitary status. Two types of cone fly eggs were observed on spruce cones. At least three species ofStrobilomyia (S. Infrequens, S. laricicola, and S. sibirica) attacked cones of Siberian larch (Larix sibirica) in central Siberia.
基金Project supported by the National Natural Science Foundation of China(Grant No.61525404)
文摘A simple rule for finding Dirac cone electronic states in solids is proposed, which is neglecting those lattice atoms inert to particular electronic bands, and pursuing the two-dimensional(2D) graphene-like quasi-atom lattices with s-and pbindings by considering the equivalent atom groups in the unit cell as quasi-atoms.Taking CsPbBr3 and Cs3Bi2Br9 bilayers as examples, we prove the effectiveness and generality of this rule with the density functional theory(DFT) calculations.We demonstrate that both bilayers have Dirac cones around the Fermi level and reveal that their corresponding Fermi velocities can reach as high as^0.2 × 10^6 m/s.This makes these new 2D layered materials very promising in making new ultra-fast ionic electronic devices.
基金the Universiti Putra Malaysia for the financial support for this research programme using HiCoE Grant,Ministry of Higher Education,Malaysia
文摘Experimental quasi-static crushing tests were conducted by using a universal testing machine format kenaf-epoxy composite elliptical cones. The work focused on the vertex angle's effects on energy absorption capability; the vertex angles vary from 0° to 24° in 6 increments. The failure modes of the kenaf fibre epoxy composite elliptical cones were observed utilising delegate photos taken during the quasistatic crushing test. Load-deformation curves and deformation histories of typical specimens are presented and discussed. Moreover, the effects of cone vertex angles on the load carrying capacity and the energy absorption capability are also discussed. The results show that the energy absorption abilities significantly influence the ellipticity vertex angle as the load carrying capacity. We concluded that the quasi-static axial crushing behaviour of elliptical mat laminated composite cones is strongly affected by their structural geometry and the specific energy absorbed by the composite elliptical cones with vertex angles of 6°, 12°, 18°, and 24°, which is more than an elliptical cone with the vertex angle of 0°(the elliptical tube) at any given deformation. However, the specific energy absorption for the elliptical composite cone showed a positive correlation, i.e., the more the angle increased, the more energy was absorbed. In this regard, an elliptical composite cone with a 24° angle exhibited the best energy absorption capability.
文摘By Ar+ sputtering onto Si wafers which were surrounded by Mo plates, uniform cones over a large area on the Si surface were formed. Scanning electron microscopic study showed that the cones were formed on the entire surface of the Si wafer. The dimensions of the uniform cones were one micrometer in diameter and 5-6 micrometers high. They were further characterized by means of cross-sectional transmission electron microscopy, with the technique of micro-diffractions. It was found that the cone contained a pure Si regime and a Mo-rich regime. In the binary Mo-Si zone, we identified three distinct areas vertically: (1) domains of Mo-induced Si ordered structures, (2) a small volume of a new Mo3Si2 structural variant, intergrown with the Si ordered structure, and (3) a small amount of pure Mo nanoparticles covering the surface of the cones. The formation of the large and uniform cones may provide a new surface configuration for potential applications in surface science and technology.
基金Project supported by the National Natural Sciences Foundation of China(Grant Nos.11704294 and 11504281)the Natural Science Foundation of Hubei Province,China(Grant No.2016CFB586)the Fundamental Research Funds for the Central Universities,China(Grant Nos.2017IVA078,2018IVB017,2017IB013,2018IB009,and 2018IB011)
文摘Two-dimensional materials with Dirac cones have significant applications in photoelectric technology. The origin and manipulation of multiple Dirac cones need to be better understood. By first-principle calculations, we study the influence of external fields on the electronic structure of the hexagonal CrB4 sheet with double nonequivalent Dirac cones. Our results show that the two cones are not sensitive to tensile strain and out-of-plane electric field, but present obviously different behaviors under the in-plane external electric field（along the B-B direction）, i.e., one cone holds while the other vanishes with a gap opening. More interestingly, a new nonequivalent cone emerges under a proper in-plane electric field. We also discuss the origin of the cones in CrB4 sheet. Our study provides a new method on how to obtain Dirac cones by the external field manipulation, which may motivate potential applications in nanoelectronics.
基金conducted under the National Natural Science Foundation of China (No.41172022)the Funds of Key Laboratory of Petroleum Resources,Gansu Province (No.SZD-KFJJ20150603)the Fundamental Research Funds for the Central Universities (No.lzujbky-2016-202)
文摘Well-preserved Ginkgo pollen organs are analyzed from the Middle Jurassic Xishanyao Formation of the Turpan–Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China, and are described as a new species, Ginkgo hamiensis Z.X. Wang et B.N. Sun sp. nov. The immature male cones are cylindrical and catkin-like, with two longitudinal stripes on the stalk. The pollen sacs are shaped like a long oval with two pollen sacs fused together for each microsporophyll, and the microsporophyll tip is a triangular cystidium. The pollen grains are oblong or fusiform and monocolpate; both ends are blunt or sharp. By comparison with previously reported fossil records of Ginkgo plants, we determined that the current fossils are different from all other reported species; thus, the present fossil is referred to as a new species of Ginkgo. The reproductive organs of the Ginkgo fossils described herein can provide valuable information for the study of Ginkgo plants. Further, there are two probable evolutionary trends in the Ginkgo pollen cones. One trend is that the number of pollen sacs changed from three or four during the Jurassic and Cretaceous to two at the present day; the other is that the number of pollen sacs has remained two from the Middle Jurassic to the present day. In addition, the pollen cones described herein are similar to the pollen cones of the extant Ginkgo, which strongly indicates that the morphology of Ginkgo plants may have remained highly conserved over millions of years.
基金supported by the Hungarian Science Foundation(OTKA)(K109330 to JM)the Hungarian Brain Research Program(KTIA_NAP_13-2-2014-0007 to JM)+1 种基金the National Research,Development and Innovation Office(GINOP-2.3.2-15-2016-00001 and GINOP-2.3.2-15-2016-00032 to JM)by an MTA Postdoctoral Fellowship(to IF)
文摘It is well established that guidance of axons during neuronal development is regulated by a variety of extracellular signals,governing cytoskeletal dynamics in growth cones.The actin and microtubule（MT）cytoskeleton have both been shown to play important roles.However,a growing body of work suggests that a critical issue is the proper coordination of changes within these two major cytoskeletal systems（reviewed in Cammara-ta et al., 2016）.
文摘The paper presents the results of biometrical study of the seeds and cones of larch taxa from Northeast of China. Fourteen characters are considered and their analyses showed that the seeds and cones of the larch taxa were relative greatly variable. Cluster analysis and principal component analysis for all 6 larch taxa were made. The analysis results proved that the dominant larch population in Toudao Farm fell within the range of variation ofLarix olgensis. The key taxonomic characters are the length of seed wing, length of cone, length of seed, the length/width ratio of seed and number of scales.
