Skyrmions emerging in centrosymmetric materials have garnered significant interest.GdGa_(2),a recently discovered centrosymmetric antiferromagnet with a triangular lattice,has been proposed to host possible Néel-...Skyrmions emerging in centrosymmetric materials have garnered significant interest.GdGa_(2),a recently discovered centrosymmetric antiferromagnet with a triangular lattice,has been proposed to host possible Néel-type skyrmions exhibiting an extremely short magnetic periodicity in the so-called A-phases.Here,we report the magnetic and magnetotransport properties of GdGa_(2) single crystals.Hall anomalies beyond magnetization scaling emerge at intermediate magnetic fields,coinciding with the skyrmion-hosting A-phases.The small amplitude of the Hall anomalies may be attributed to the short period of the spin textures.In contrast,the transport behavior of TbGa_(2) single crystals is well described by a conventional two-band model.This discrepancy likely arises from distinct Ruderman–Kittel–Kasuya–Yosida interaction strengths and/or magnetic anisotropy between the two crystals.Our results establish GdGa_(2) as a new material platform for the exploration of skyrmion physics in centrosymmetric systems.展开更多
Acoustic-vortex(AV)tweezers ensure stable particle trapping at a zero-pressure center,while particle assembly between two vortex cores is still prevented by the high-potential barrier.Although a one-dimensional low-pr...Acoustic-vortex(AV)tweezers ensure stable particle trapping at a zero-pressure center,while particle assembly between two vortex cores is still prevented by the high-potential barrier.Although a one-dimensional low-pressure attractive path of particle assembly can be constructed by the interference between two independent cylindrical Bessel beams,it remains challenging to create two-dimensional(2D)neighboring vortexes using a source array in practical applications.In this paper,a three-step phase-reversal strategy of 2D particle assembly based on the synchronized evolution of a centrosymmetric array of M off-axis acoustic vortexes(OA-AVs)with a preset radial offset is proposed based on a ring array of planar sources.By introducing initial vortex phase differences of-2π/M and+2π/M to the vortex array,low-pressure patterns of an M-sided regular polygon and M-branched star are formed by connecting the vortex cores and the field center before and after the tangent state of adjacent OA-AVs.Center-oriented particle assembly is finally realized by a central AV constructed by coincident in-phase OA-AVs.The capability of particle manipulation in the lateral and radial directions is demonstrated by low-pressure patterns with acoustic radiation forces pointing to the field center during a synchronized central approach.The field evolution is certified by experimental field measurements for OA-AVs with different vo rtex numbers,initial vortex phase differences,and radial offsets using a ring array of 16 planar sources.The feasibility of particle assembly in two dimensions is also verified by the accurate manipulation of four particles using the low-pressure patterns of a four-sided polygon,a four-branched star,and a central AV in experiments.The three-step strategy paves a new way for 2D particle assembly based on the synchronize d evolution of centrosymmetric OA-AVs using a simplified single-sided source array,exhibiting excellent potential for the precise navigation and manipulation of cells and particles in biomedical applications.展开更多
To optimize secondary air nozzle structure in purifying burner,this study focused on the comparison of purification,combustion and NO_(x)emission characteristics of pulverized coal preheated by a 30 kW purifying burne...To optimize secondary air nozzle structure in purifying burner,this study focused on the comparison of purification,combustion and NO_(x)emission characteristics of pulverized coal preheated by a 30 kW purifying burner with coaxial and centrosymmetric structures.Centrosymmetric structure shifted the position of main burning region down in high-temperature reduction unit(HTRU),and the number of branches differently influenced the temperature in different regions with this structure.For reductive gas components,CO concentration with centrosymmetric structure was higher compared to coaxial structure,while the differences in H_(2)and CH_(4)concentrations were smaller.Centrosymmetric structure was more disadvantageous to improve physicochemical properties of pulverized coal compared to coaxial structure,and this structure with four branches further deteriorated its properties compared to two branches.In mild combustion unit(MCU),the temperature at top was lower with centrosymmetric structure,while was higher in the rest.Centrosymmetric structure more effectively reduced NO_(x)emission compared to coaxial structure,but with slight sacrifice of combustion efficiency(η).Moreover,both two-branch and four-branch centrosymmetric structures realized ultra-low NO_(x)emission(<50 mg·m^(-3))with high η of over 98.50%,and the former was more advantageous.With this optimal structure,η and NO_(x)emission were 99.25%and 40.42 mg·m^(-3).展开更多
In this letter, excited state dynamics of TPZ2, a centrosymmetric PRODAN dye, has been studied by using several time-resolved spectroscopy techniques. Fluorescence quantum yield of TPZ2 is found to be 0.50 in both ace...In this letter, excited state dynamics of TPZ2, a centrosymmetric PRODAN dye, has been studied by using several time-resolved spectroscopy techniques. Fluorescence quantum yield of TPZ2 is found to be 0.50 in both acetonitrile and ethanol solution. The radiative decay rate of the excited state of TPZ2 is determined to be 2.0×10^8 s^-1. Meanwhile, highly efficient triplet state and singlet oxygen generation have been observed in TPZ2 and the intersystem crossing（ISC） rate is determined to be 2.0×10^8s^-1. The almost identical ISC and non-radiative decay rates indicate that ISC is the only non-radiative decay pathway in TPZ2. Thus, dual excited state（S1） deactivation mechanism（50/50, fluorescence/ISC） of TPZ2 is proposed.Because of this unique property, TPZ2 has the potential to be used as biocompatible imaging and photodynamic therapy agent in the same time.展开更多
The current paper is mainly devoted for solving centrosymmetric linear systems of equations. Formulae for the determinants of tridiagonal centrosymmetric matrices are obtained explicitly. Two efficient computational a...The current paper is mainly devoted for solving centrosymmetric linear systems of equations. Formulae for the determinants of tridiagonal centrosymmetric matrices are obtained explicitly. Two efficient computational algorithms are established for solving general centrosymmetric linear systems. Based on these algorithms, a MAPLE procedure is written. Some illustrative examples are given.展开更多
Chirality is a widespread phenomenon in nature,where two non-superimposable enantiomers exist with one being the mirror image of the other.The interplay between chirality and magnetism has recently drawn intensive int...Chirality is a widespread phenomenon in nature,where two non-superimposable enantiomers exist with one being the mirror image of the other.The interplay between chirality and magnetism has recently drawn intensive interest in non-centrosymmetric magnetic materials absent of both spatial and time inversion symmetries[1].Among various chiral magnetic effects,the electrical manifestation of the magneto-chiral effect is crucial for both fundamental science and technological applications[2,3].The non-reciprocal resistance depending on the inner product of the magnetic field(H)and the current density U),termed the electrical magneto-chiral effect(eMChE),has recently been demonstrated in correlated oxides[4,5].展开更多
The separation of photogenerated electron–hole pairs is vitally important for photocatalysis,which can be effectively promoted by polarization field.However,it only manifests in piezoelectric/pyroelectric/ferroelectr...The separation of photogenerated electron–hole pairs is vitally important for photocatalysis,which can be effectively promoted by polarization field.However,it only manifests in piezoelectric/pyroelectric/ferroelectric materials that have a non-centrosymmetric structure.Here,we demonstrate that the polarization enhanced photocatalysis(with wide spectra from ultraviolet(UV)light to visible light)can be achieved in centrosymmetric semiconductors,such asδ-MnO_(2) and TiO_(2) nanosheets integrated nanoflowers,by using the strain-gradient-induced flexoelectric polarization that is always overlooked in polarization-enhanced catalysis.Under ultrasonic and illumination excitation,the organic pollutants(methylene blue(MB),etc.)can be effectively degraded within 30 min with excellent stability and repeatability.Compared with photocatalysis,the flexo-photocatalytic performance of above centrosymmetric semiconductors is substantially increased by 85%.Moreover,the factors related to flexo-photocatalysis such as material morphology,mechanical stimuli source,and adsorption are explored to deeply understand the mechanism of flexo-photocatalysis.This work opens up a way for high-performance photocatalysis in centrosymmetric semiconductors.展开更多
Spontaneous polarization due to symmetry breaking in the transition metal ditellurides(MTe_(2))family exhibits intriguing sliding ferroelectricity.Although theoretical predictions of MTe_(2)ferroelectric metals with n...Spontaneous polarization due to symmetry breaking in the transition metal ditellurides(MTe_(2))family exhibits intriguing sliding ferroelectricity.Although theoretical predictions of MTe_(2)ferroelectric metals with noncentrosymmetric stacking have been reported,the realization of such polarization structure remains a challenge.Here,we demonstrate the synthesis of PtTe_(2)with non-centrosymmetric stacking layers,in contrast to bulk AA stacking,achieved within a scanning transmission electron microscope(STEM)by irradiating amorphous PtxTeythin flms with an electron beam probe.Cross-sectional STEM imaging combined with frst-principles calculations reveals that the diverse stacking confgurations due to an intralayerπ-stacking system break centrosymmetry in PtTe_(2),giving rise to the out-of-plane polarization.Three-dimensional atomic positions identifed by the atomic electron tomography method further demonstrate the local distortions associated with the non-centrosymmetric stacking layers in PtTe_(2).The understanding of the atomic origin of polarization in PtTe_(2)is of signifcant importance for developing devices that integrate ferroelectricity with metallicity.展开更多
We define an m-involution to be a matrix K ∈ Cn×n for which Km -= I. In this article, we investigate the class Sm （A） of m-involutions that commute with a diagonalizable matrix A E Cn×n. A number of basic...We define an m-involution to be a matrix K ∈ Cn×n for which Km -= I. In this article, we investigate the class Sm （A） of m-involutions that commute with a diagonalizable matrix A E Cn×n. A number of basic properties of Sm （A） and its related subclass Sm （A, X） are given, where X is an eigenvector matrix of A. Among them, Sm （A） is shown to have a torsion group structure under matrix multiplication if A has distinct eigenvalues and has non-denumerable cardinality otherwise. The constructive definition of Sm （A, X） allows one to generate all m-involutions commuting with a matrix with distinct eigenvalues. Some related results are also given for the class S,, （A） of m-involutions that anti-commute with a matrix A ∈ Cnn×n.展开更多
The title compound, 〔NH 4〕 6〔(CH 3CO) 2(Mo 8O 28 )〕·4H 2O, was produced from (NH 4) 6〔Mo 7O 24 〕·4H 2O aqueous solution in the presence of N 2H 4·H 2SO 4 and its structure ha...The title compound, 〔NH 4〕 6〔(CH 3CO) 2(Mo 8O 28 )〕·4H 2O, was produced from (NH 4) 6〔Mo 7O 24 〕·4H 2O aqueous solution in the presence of N 2H 4·H 2SO 4 and its structure has been determined by X ray single crystal analysis. The crystallographic data: C 4H 38 Mo 8N 6O 34 , M r =1481.92, triclinic, P1, a=8.127(2), b = 10\^373(2), c = 12.383(3) , α=99.51(3), β=105.47(3), γ=112.92(3)°, V=883.0(3) 3, Z=1, D c =2.787g/cm 3, F(000)= 712, μ =2.864 mm -1 , Final R =0.0368 and wR =0.0924 for 2926 reflections with I】2σ(I ). The X ray crystal structure analysis reveals that there is one independent molecule in the unit cell of the title compound which contains one centrosymmetric diacetyloctamolybdate anion, six ammonium cations and four water molecules.展开更多
The title compound, [C3H5N2]4[(C6H5NO2)2(Mo8O26)] 1, was synthesized by the reaction of H2MoO4, nicotinic acid and imidazole in aqueous solution. Single-crystal X-ray analysis has revealed that compound 1 (C24H30Mo8N1...The title compound, [C3H5N2]4[(C6H5NO2)2(Mo8O26)] 1, was synthesized by the reaction of H2MoO4, nicotinic acid and imidazole in aqueous solution. Single-crystal X-ray analysis has revealed that compound 1 (C24H30Mo8N10O30) crystallizes in the monoclinic system, space group P21/n, Mr = 1706.10, a = 12.529(1), b = 12.796(1), c = 14.038(1) , b = 100.2(1), V = 2215.3(2) 3, Z = 2, Dc = 2.558 g/cm3, F(000) = 1640, = 2.299 mm-1, the final R = 0.0527 and wR = 0.0964 for 3064 observed reflections with I > 2s(I). X-ray crystal structure analysis suggests that compound 1 consists of centrosymmetric dinicotinatooctamolybdate anion and four protonated imidazole cations, which are linked into a three-dimensional framework through hydrogen bonding.展开更多
The title compound (Himi)4[Mo8O26(imi)2]4H2O (imi = imidazole) 1 was synthe- sized by the reaction of H2MoO4 and imidazole in aqueous solution. Single-crystal X-ray analysis reveals that compound 1 is crystallized in ...The title compound (Himi)4[Mo8O26(imi)2]4H2O (imi = imidazole) 1 was synthe- sized by the reaction of H2MoO4 and imidazole in aqueous solution. Single-crystal X-ray analysis reveals that compound 1 is crystallized in the triclinic system, space group P with a = 10.6219(8), b = 10.7260(8), c = 11.3220(9) , a = 92.842(2), b =117.364(1), g = 101.655(1), C18H36Mo8N12- O30, Mr = 1668.11, V = 1106.8(2) 3, Z = 1, Dc = 2.503 g/cm3, F(000) = 804, m = 2.298 mm-1, the final R = 0.0714 and wR = 0.1651 for 3121 observed reflections with I > 2s(I). The X-ray crystal structure analysis suggests that compound 1 is built up by two imidazole ligands coordinated by the centrosymmetric octamolybdate anions, protonated imidazole cations and crystallization water molecules.展开更多
Generalize reflexive matrices are a special class of matrices ?that have the relation where? and ?are some generalized reflection matrices. The nontrivial cases ( or ) of this class of matrices occur very often in man...Generalize reflexive matrices are a special class of matrices ?that have the relation where? and ?are some generalized reflection matrices. The nontrivial cases ( or ) of this class of matrices occur very often in many scientific and engineering applications. They are also a generalization of centrosymmetric matrices and reflexive matrices. The main purpose of this paper is to present block decomposition schemes for generalized reflexive matrices of various types and to obtain their decomposed explicit block-diagonal structures. The decompositions make use of unitary equivalence transformations and, therefore, preserve the singular values of the matrices. They lead to more efficient sequential computations and at the same time induce large-grain parallelism as a by-product, making themselves computationally attractive for large-scale applications. A numerical example is employed to show the usefulness of the developed explicit decompositions for decoupling linear least-square problems whose coefficient matrices are of this class into smaller and independent subproblems.展开更多
Electric polarization typically originates from non-centrosymmetric charge distributions in compounds.In elemental crystalline materials,chemical bonds between atoms of the same element favor symmetrically distributed...Electric polarization typically originates from non-centrosymmetric charge distributions in compounds.In elemental crystalline materials,chemical bonds between atoms of the same element favor symmetrically distributed electron charges and centrosymmetric structures,making elemental ferroelectrics rare.Compared to atoms,elemental clusters are intrinsically less symmetric and can have various preferred orientations when they are assembled to form crystals.Consequently,the assembly of clusters with different orientations tends to break the inversion symmetry.By exploiting this concept,we show that sliding ferroelectricity naturally emerges in trilayer quasi-hexagonal phase(qHP)C_(60),a cluster-assembled carbon allotrope recently synthesized.Compared to many metallic or semi-metallic elemental ferroelectrics,trilayer qHP C_(60)’s have sizable band gaps and several ferroelectric structures,which are distinguishable by measuring their second-harmonic generation(SHG)responses.Some of these phases show both switchable out-of-plane and in-plane polarizations on the order of 0.2 pC/m.The out-of-plane and in-plane polarizations can be switched independently and enable an easy-to-implement construction of Van der Waals homostructures with ferroelectrically switchable chirality.展开更多
The bulk photovoltaic(BPV)effect,which generates steady photocurrents and above-bandgap photovoltages in non-centrosymmetric materials when exposed to light,holds great potential for advancing optoelectronic and photo...The bulk photovoltaic(BPV)effect,which generates steady photocurrents and above-bandgap photovoltages in non-centrosymmetric materials when exposed to light,holds great potential for advancing optoelectronic and photovoltaic technologies.However,its influence on the reconfiguration of ferroelectric domain structure remains underexplored.In this study,we developed a phase-field model to understand the BPV effect in ferroelectric oxides.Our model reveals that variations in BPV currents across domains create opposing charges at domain walls,enhancing the electric field within domains to~1000 kV/cm.The strong electric fields can reorient the ferroelectric polarization and enable ultrafast domain wall movements and nonvolatile domain switching on the picosecond scale.Applying anisotropic strain can further strengthen this effect,enablingmore precise control of domain switching.Our findings advance the fundamental understanding of BPV effect in ferroelectrics,paving the ways for developing opto-ferroelectric memory technologies and highefficiency photovoltaic applications via precise domain engineering.展开更多
We consider the system of four linear matrix equations A_1 X = C_1,XB_2 =C_2,A_3,XB_3, = C3 and A_4XB_4 = C_4 over R, an arbitrary von Neumann regular ring with identity. Anecessary and sufficient condition for the ex...We consider the system of four linear matrix equations A_1 X = C_1,XB_2 =C_2,A_3,XB_3, = C3 and A_4XB_4 = C_4 over R, an arbitrary von Neumann regular ring with identity. Anecessary and sufficient condition for the existence and the expression of the general solution tothe system are derived. As applications, necessary and sufficient conditions are given for thesystem of matrix equations A_1X = C_1 and A_3X = C_3 to have a bisymmetric solution, the system ofmatrix equations A_1X = C_1 and A_3XB_3 = C_3 to have a perselfconjugate solution over R with aninvolution and char R≠2, respectively. The representations of such solutions are also presented.Moreover, some auxiliary results on other systems over R are obtained. The previous known results onsome systems of matrix equations are special cases of the new results.展开更多
In the present investigation,a facile synthesis method is explored involving a self-combustion of a solid precursor mixture of iron oxide Fe_(2)O_(3) and boric acid(H_(3)BO_(3))using camphor(C_(10)H_(16)O)as fuel in a...In the present investigation,a facile synthesis method is explored involving a self-combustion of a solid precursor mixture of iron oxide Fe_(2)O_(3) and boric acid(H_(3)BO_(3))using camphor(C_(10)H_(16)O)as fuel in ambient air in order to form a single phase Fe_(3)BO_(6) crystallites.X-ray diffraction(XRD),Field emission electron microscopy(FESEM),magnetic,and dielectric properties of as prepared sample are studied.From XRD pattern,a single phase compound is observed with an orthorhombic crystal structure(Pnma space group),with average crystallite size of 42 nm.A reasonably uniform size distribution of the plates and self-assemblies is retained in the sample.A magnetic transition is observed in dielectric permittivity(at-445 K)and power loss(at-435 K)when plotted against temperature.A weak peak occurs near 330 K due to the charge reordering in the sample.For temperatures above the transition temperature,a sharp increase of the dielectric loss is observed which occurs due to the presence of thermally activated charge carriers.A canted antiferromagnetic Fe_(3)þordering in a Fe_(3)BO_(6) lattice with a localized charge surface layer is an apparent source of exhibiting a ferroelectric feature in this unique example of a centrosymmetric compound.An induced spin current over the Fe sites thus could give rise to a polarization hysteresis loop.Due to the presence of both ferromagnetic as well as polarization ordering,Fe_(3)BO_(6) behaves like a single phase multiferroic ceramics.展开更多
Two isostructural tellurite phosphates Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)have been synthesized via hydrothermal method.Both of them crystalize in monoclinic space group C2/m(No.12).For Ni_(...Two isostructural tellurite phosphates Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)have been synthesized via hydrothermal method.Both of them crystalize in monoclinic space group C2/m(No.12).For Ni_(2)ZnTe^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4),a=19.3247(10),b=5.9697(3),c=4.7737(2)Å,β=103.637(5)°,V=535.18(5)Å^(3),Z=2,M_(r)=727.94,S=1.103,D_(c)=4.517 g·cm^(-3),μ(Mo Kα)=11.434 mm^(-1) and F(000)=672,the final R=0.0369and wR=0.1086 for 639 observed reflections with I>2σ(I).The crystal structure of Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)features a 3D framework composed of[Ni_(2)O_(2)(PO_(4))_(2)]^(6-)layers interconnected by[MTe_(2)O_(2)(OH)_(4)]^(2+)single chains.Different magnetic susceptibility results at low temperature of the two title compounds confirm that Zn(1)completely occupies the Ni(2)position but not partially substitutes both Ni(1)and Ni(2)position atoms.Additionally,the acentric TeO_(3)(OH)_(2) tetragonal pyramids are aligned in an antiparallel manner,resulting in the crystallization of centrosymmetric(C2/m)crystal structure instead of the non-centrosymmetric crystal structure.The investigation of the origin of centrosymmetric crystal structure with strong dipole moment units provides deeper understanding for future rational design for non-centrosymmetric crystal structure.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12274125,12574117,12374105,12174103)。
文摘Skyrmions emerging in centrosymmetric materials have garnered significant interest.GdGa_(2),a recently discovered centrosymmetric antiferromagnet with a triangular lattice,has been proposed to host possible Néel-type skyrmions exhibiting an extremely short magnetic periodicity in the so-called A-phases.Here,we report the magnetic and magnetotransport properties of GdGa_(2) single crystals.Hall anomalies beyond magnetization scaling emerge at intermediate magnetic fields,coinciding with the skyrmion-hosting A-phases.The small amplitude of the Hall anomalies may be attributed to the short period of the spin textures.In contrast,the transport behavior of TbGa_(2) single crystals is well described by a conventional two-band model.This discrepancy likely arises from distinct Ruderman–Kittel–Kasuya–Yosida interaction strengths and/or magnetic anisotropy between the two crystals.Our results establish GdGa_(2) as a new material platform for the exploration of skyrmion physics in centrosymmetric systems.
基金funded by the National Nature Science Foundation of China(11934009,12174198,and 12227808)the Natural Science Foundation of Jiangsu Province,China(BE2022814)+2 种基金the Universal Technology for Primary and Secondary Schoolsthe National Research Institute for Teaching Materialsthe Qing Lan Project of Jiangsu Province,China。
文摘Acoustic-vortex(AV)tweezers ensure stable particle trapping at a zero-pressure center,while particle assembly between two vortex cores is still prevented by the high-potential barrier.Although a one-dimensional low-pressure attractive path of particle assembly can be constructed by the interference between two independent cylindrical Bessel beams,it remains challenging to create two-dimensional(2D)neighboring vortexes using a source array in practical applications.In this paper,a three-step phase-reversal strategy of 2D particle assembly based on the synchronized evolution of a centrosymmetric array of M off-axis acoustic vortexes(OA-AVs)with a preset radial offset is proposed based on a ring array of planar sources.By introducing initial vortex phase differences of-2π/M and+2π/M to the vortex array,low-pressure patterns of an M-sided regular polygon and M-branched star are formed by connecting the vortex cores and the field center before and after the tangent state of adjacent OA-AVs.Center-oriented particle assembly is finally realized by a central AV constructed by coincident in-phase OA-AVs.The capability of particle manipulation in the lateral and radial directions is demonstrated by low-pressure patterns with acoustic radiation forces pointing to the field center during a synchronized central approach.The field evolution is certified by experimental field measurements for OA-AVs with different vo rtex numbers,initial vortex phase differences,and radial offsets using a ring array of 16 planar sources.The feasibility of particle assembly in two dimensions is also verified by the accurate manipulation of four particles using the low-pressure patterns of a four-sided polygon,a four-branched star,and a central AV in experiments.The three-step strategy paves a new way for 2D particle assembly based on the synchronize d evolution of centrosymmetric OA-AVs using a simplified single-sided source array,exhibiting excellent potential for the precise navigation and manipulation of cells and particles in biomedical applications.
基金Postdoctoral Fellowship Program of CPSF(GZC20232672)CAS Project for Young Scientists in Basic Research(YSBR-028)the Strategic Priority Research Program(XDA29010200)are gratefully acknowledged.
文摘To optimize secondary air nozzle structure in purifying burner,this study focused on the comparison of purification,combustion and NO_(x)emission characteristics of pulverized coal preheated by a 30 kW purifying burner with coaxial and centrosymmetric structures.Centrosymmetric structure shifted the position of main burning region down in high-temperature reduction unit(HTRU),and the number of branches differently influenced the temperature in different regions with this structure.For reductive gas components,CO concentration with centrosymmetric structure was higher compared to coaxial structure,while the differences in H_(2)and CH_(4)concentrations were smaller.Centrosymmetric structure was more disadvantageous to improve physicochemical properties of pulverized coal compared to coaxial structure,and this structure with four branches further deteriorated its properties compared to two branches.In mild combustion unit(MCU),the temperature at top was lower with centrosymmetric structure,while was higher in the rest.Centrosymmetric structure more effectively reduced NO_(x)emission compared to coaxial structure,but with slight sacrifice of combustion efficiency(η).Moreover,both two-branch and four-branch centrosymmetric structures realized ultra-low NO_(x)emission(<50 mg·m^(-3))with high η of over 98.50%,and the former was more advantageous.With this optimal structure,η and NO_(x)emission were 99.25%and 40.42 mg·m^(-3).
基金funded by the National Natural Science Foundation of China (No. 11674101)
文摘In this letter, excited state dynamics of TPZ2, a centrosymmetric PRODAN dye, has been studied by using several time-resolved spectroscopy techniques. Fluorescence quantum yield of TPZ2 is found to be 0.50 in both acetonitrile and ethanol solution. The radiative decay rate of the excited state of TPZ2 is determined to be 2.0×10^8 s^-1. Meanwhile, highly efficient triplet state and singlet oxygen generation have been observed in TPZ2 and the intersystem crossing（ISC） rate is determined to be 2.0×10^8s^-1. The almost identical ISC and non-radiative decay rates indicate that ISC is the only non-radiative decay pathway in TPZ2. Thus, dual excited state（S1） deactivation mechanism（50/50, fluorescence/ISC） of TPZ2 is proposed.Because of this unique property, TPZ2 has the potential to be used as biocompatible imaging and photodynamic therapy agent in the same time.
文摘The current paper is mainly devoted for solving centrosymmetric linear systems of equations. Formulae for the determinants of tridiagonal centrosymmetric matrices are obtained explicitly. Two efficient computational algorithms are established for solving general centrosymmetric linear systems. Based on these algorithms, a MAPLE procedure is written. Some illustrative examples are given.
基金financially supported by the National Key R&D Program of China(2022YFA1403000 and 2022YFA1403300)the National Natural Science Foundation of China(52072244,12104305,12074080,12274088,11874054,and 12104301)+3 种基金the Science and Technology Commission of Shanghai Municipality(21JC1405000 and 21PJ410800)The research used resources from Analytical Instrumentation Center(#SPST-AIC10112914)C?EM(EM02161943)in Shanghai Tech Universitysupported by the U.S.DOE Office of Science-Basic Energy Sciences,under Contract No.DE-AC02-06CH11357。
文摘Chirality is a widespread phenomenon in nature,where two non-superimposable enantiomers exist with one being the mirror image of the other.The interplay between chirality and magnetism has recently drawn intensive interest in non-centrosymmetric magnetic materials absent of both spatial and time inversion symmetries[1].Among various chiral magnetic effects,the electrical manifestation of the magneto-chiral effect is crucial for both fundamental science and technological applications[2,3].The non-reciprocal resistance depending on the inner product of the magnetic field(H)and the current density U),termed the electrical magneto-chiral effect(eMChE),has recently been demonstrated in correlated oxides[4,5].
基金supported by the National Natural Science Foundation of China(No.52202162).
文摘The separation of photogenerated electron–hole pairs is vitally important for photocatalysis,which can be effectively promoted by polarization field.However,it only manifests in piezoelectric/pyroelectric/ferroelectric materials that have a non-centrosymmetric structure.Here,we demonstrate that the polarization enhanced photocatalysis(with wide spectra from ultraviolet(UV)light to visible light)can be achieved in centrosymmetric semiconductors,such asδ-MnO_(2) and TiO_(2) nanosheets integrated nanoflowers,by using the strain-gradient-induced flexoelectric polarization that is always overlooked in polarization-enhanced catalysis.Under ultrasonic and illumination excitation,the organic pollutants(methylene blue(MB),etc.)can be effectively degraded within 30 min with excellent stability and repeatability.Compared with photocatalysis,the flexo-photocatalytic performance of above centrosymmetric semiconductors is substantially increased by 85%.Moreover,the factors related to flexo-photocatalysis such as material morphology,mechanical stimuli source,and adsorption are explored to deeply understand the mechanism of flexo-photocatalysis.This work opens up a way for high-performance photocatalysis in centrosymmetric semiconductors.
基金supported by the National Key R&D Program of China(Grant Nos.2024YFA1208201,2022YFA1403000,and 2021YFA1400204)the National Natural Science Foundation of China(Grant Nos.52322311,12334001,52427802,12174432,12250710675,and 52461160301)the support from Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)。
文摘Spontaneous polarization due to symmetry breaking in the transition metal ditellurides(MTe_(2))family exhibits intriguing sliding ferroelectricity.Although theoretical predictions of MTe_(2)ferroelectric metals with noncentrosymmetric stacking have been reported,the realization of such polarization structure remains a challenge.Here,we demonstrate the synthesis of PtTe_(2)with non-centrosymmetric stacking layers,in contrast to bulk AA stacking,achieved within a scanning transmission electron microscope(STEM)by irradiating amorphous PtxTeythin flms with an electron beam probe.Cross-sectional STEM imaging combined with frst-principles calculations reveals that the diverse stacking confgurations due to an intralayerπ-stacking system break centrosymmetry in PtTe_(2),giving rise to the out-of-plane polarization.Three-dimensional atomic positions identifed by the atomic electron tomography method further demonstrate the local distortions associated with the non-centrosymmetric stacking layers in PtTe_(2).The understanding of the atomic origin of polarization in PtTe_(2)is of signifcant importance for developing devices that integrate ferroelectricity with metallicity.
文摘We define an m-involution to be a matrix K ∈ Cn×n for which Km -= I. In this article, we investigate the class Sm （A） of m-involutions that commute with a diagonalizable matrix A E Cn×n. A number of basic properties of Sm （A） and its related subclass Sm （A, X） are given, where X is an eigenvector matrix of A. Among them, Sm （A） is shown to have a torsion group structure under matrix multiplication if A has distinct eigenvalues and has non-denumerable cardinality otherwise. The constructive definition of Sm （A, X） allows one to generate all m-involutions commuting with a matrix with distinct eigenvalues. Some related results are also given for the class S,, （A） of m-involutions that anti-commute with a matrix A ∈ Cnn×n.
文摘The title compound, 〔NH 4〕 6〔(CH 3CO) 2(Mo 8O 28 )〕·4H 2O, was produced from (NH 4) 6〔Mo 7O 24 〕·4H 2O aqueous solution in the presence of N 2H 4·H 2SO 4 and its structure has been determined by X ray single crystal analysis. The crystallographic data: C 4H 38 Mo 8N 6O 34 , M r =1481.92, triclinic, P1, a=8.127(2), b = 10\^373(2), c = 12.383(3) , α=99.51(3), β=105.47(3), γ=112.92(3)°, V=883.0(3) 3, Z=1, D c =2.787g/cm 3, F(000)= 712, μ =2.864 mm -1 , Final R =0.0368 and wR =0.0924 for 2926 reflections with I】2σ(I ). The X ray crystal structure analysis reveals that there is one independent molecule in the unit cell of the title compound which contains one centrosymmetric diacetyloctamolybdate anion, six ammonium cations and four water molecules.
基金the NNSF of China (20073048), NSF of Fujian province (2002F015) and the Chinese Academy of Sciences
文摘The title compound, [C3H5N2]4[(C6H5NO2)2(Mo8O26)] 1, was synthesized by the reaction of H2MoO4, nicotinic acid and imidazole in aqueous solution. Single-crystal X-ray analysis has revealed that compound 1 (C24H30Mo8N10O30) crystallizes in the monoclinic system, space group P21/n, Mr = 1706.10, a = 12.529(1), b = 12.796(1), c = 14.038(1) , b = 100.2(1), V = 2215.3(2) 3, Z = 2, Dc = 2.558 g/cm3, F(000) = 1640, = 2.299 mm-1, the final R = 0.0527 and wR = 0.0964 for 3064 observed reflections with I > 2s(I). X-ray crystal structure analysis suggests that compound 1 consists of centrosymmetric dinicotinatooctamolybdate anion and four protonated imidazole cations, which are linked into a three-dimensional framework through hydrogen bonding.
基金This work was supported by the National Natural Science Foundation of China (20073048) NSF of Fujian province (2002F015) and the Chinese Academy of Sciences
文摘The title compound (Himi)4[Mo8O26(imi)2]4H2O (imi = imidazole) 1 was synthe- sized by the reaction of H2MoO4 and imidazole in aqueous solution. Single-crystal X-ray analysis reveals that compound 1 is crystallized in the triclinic system, space group P with a = 10.6219(8), b = 10.7260(8), c = 11.3220(9) , a = 92.842(2), b =117.364(1), g = 101.655(1), C18H36Mo8N12- O30, Mr = 1668.11, V = 1106.8(2) 3, Z = 1, Dc = 2.503 g/cm3, F(000) = 804, m = 2.298 mm-1, the final R = 0.0714 and wR = 0.1651 for 3121 observed reflections with I > 2s(I). The X-ray crystal structure analysis suggests that compound 1 is built up by two imidazole ligands coordinated by the centrosymmetric octamolybdate anions, protonated imidazole cations and crystallization water molecules.
文摘Generalize reflexive matrices are a special class of matrices ?that have the relation where? and ?are some generalized reflection matrices. The nontrivial cases ( or ) of this class of matrices occur very often in many scientific and engineering applications. They are also a generalization of centrosymmetric matrices and reflexive matrices. The main purpose of this paper is to present block decomposition schemes for generalized reflexive matrices of various types and to obtain their decomposed explicit block-diagonal structures. The decompositions make use of unitary equivalence transformations and, therefore, preserve the singular values of the matrices. They lead to more efficient sequential computations and at the same time induce large-grain parallelism as a by-product, making themselves computationally attractive for large-scale applications. A numerical example is employed to show the usefulness of the developed explicit decompositions for decoupling linear least-square problems whose coefficient matrices are of this class into smaller and independent subproblems.
基金support by the NationalNatural Science Foundation of China(12104080,12474221,12374253,and 12074053)the Guangdong Provincial Quantum Science Strategic Initiative(Grant No.GDZX2401002).Computational resources are provided by the National Supercomputer Center at Wuzhen.
文摘Electric polarization typically originates from non-centrosymmetric charge distributions in compounds.In elemental crystalline materials,chemical bonds between atoms of the same element favor symmetrically distributed electron charges and centrosymmetric structures,making elemental ferroelectrics rare.Compared to atoms,elemental clusters are intrinsically less symmetric and can have various preferred orientations when they are assembled to form crystals.Consequently,the assembly of clusters with different orientations tends to break the inversion symmetry.By exploiting this concept,we show that sliding ferroelectricity naturally emerges in trilayer quasi-hexagonal phase(qHP)C_(60),a cluster-assembled carbon allotrope recently synthesized.Compared to many metallic or semi-metallic elemental ferroelectrics,trilayer qHP C_(60)’s have sizable band gaps and several ferroelectric structures,which are distinguishable by measuring their second-harmonic generation(SHG)responses.Some of these phases show both switchable out-of-plane and in-plane polarizations on the order of 0.2 pC/m.The out-of-plane and in-plane polarizations can be switched independently and enable an easy-to-implement construction of Van der Waals homostructures with ferroelectrically switchable chirality.
基金the support of the National Science Foundation via grant CMMI-2132105.
文摘The bulk photovoltaic(BPV)effect,which generates steady photocurrents and above-bandgap photovoltages in non-centrosymmetric materials when exposed to light,holds great potential for advancing optoelectronic and photovoltaic technologies.However,its influence on the reconfiguration of ferroelectric domain structure remains underexplored.In this study,we developed a phase-field model to understand the BPV effect in ferroelectric oxides.Our model reveals that variations in BPV currents across domains create opposing charges at domain walls,enhancing the electric field within domains to~1000 kV/cm.The strong electric fields can reorient the ferroelectric polarization and enable ultrafast domain wall movements and nonvolatile domain switching on the picosecond scale.Applying anisotropic strain can further strengthen this effect,enablingmore precise control of domain switching.Our findings advance the fundamental understanding of BPV effect in ferroelectrics,paving the ways for developing opto-ferroelectric memory technologies and highefficiency photovoltaic applications via precise domain engineering.
基金This research is supported by the Natural Science Foundation of China(No.0471085the Natural Science Foundation of Shanghai)the Development Foundation of Shanghai Educational Committee the Special Funds for Major Specialities of Shanghai Education Co
文摘We consider the system of four linear matrix equations A_1 X = C_1,XB_2 =C_2,A_3,XB_3, = C3 and A_4XB_4 = C_4 over R, an arbitrary von Neumann regular ring with identity. Anecessary and sufficient condition for the existence and the expression of the general solution tothe system are derived. As applications, necessary and sufficient conditions are given for thesystem of matrix equations A_1X = C_1 and A_3X = C_3 to have a bisymmetric solution, the system ofmatrix equations A_1X = C_1 and A_3XB_3 = C_3 to have a perselfconjugate solution over R with aninvolution and char R≠2, respectively. The representations of such solutions are also presented.Moreover, some auxiliary results on other systems over R are obtained. The previous known results onsome systems of matrix equations are special cases of the new results.
基金supported by Science and Engineering Research Board,DST,New Delhi,Government of India(Grant no.:PDF/2016/003784).
文摘In the present investigation,a facile synthesis method is explored involving a self-combustion of a solid precursor mixture of iron oxide Fe_(2)O_(3) and boric acid(H_(3)BO_(3))using camphor(C_(10)H_(16)O)as fuel in ambient air in order to form a single phase Fe_(3)BO_(6) crystallites.X-ray diffraction(XRD),Field emission electron microscopy(FESEM),magnetic,and dielectric properties of as prepared sample are studied.From XRD pattern,a single phase compound is observed with an orthorhombic crystal structure(Pnma space group),with average crystallite size of 42 nm.A reasonably uniform size distribution of the plates and self-assemblies is retained in the sample.A magnetic transition is observed in dielectric permittivity(at-445 K)and power loss(at-435 K)when plotted against temperature.A weak peak occurs near 330 K due to the charge reordering in the sample.For temperatures above the transition temperature,a sharp increase of the dielectric loss is observed which occurs due to the presence of thermally activated charge carriers.A canted antiferromagnetic Fe_(3)þordering in a Fe_(3)BO_(6) lattice with a localized charge surface layer is an apparent source of exhibiting a ferroelectric feature in this unique example of a centrosymmetric compound.An induced spin current over the Fe sites thus could give rise to a polarization hysteresis loop.Due to the presence of both ferromagnetic as well as polarization ordering,Fe_(3)BO_(6) behaves like a single phase multiferroic ceramics.
基金Supported by the National Natural Science Foundation of China(No.21201144)the Natural Science Foundation of Fujian Province(No.2018J07006)。
文摘Two isostructural tellurite phosphates Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)have been synthesized via hydrothermal method.Both of them crystalize in monoclinic space group C2/m(No.12).For Ni_(2)ZnTe^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4),a=19.3247(10),b=5.9697(3),c=4.7737(2)Å,β=103.637(5)°,V=535.18(5)Å^(3),Z=2,M_(r)=727.94,S=1.103,D_(c)=4.517 g·cm^(-3),μ(Mo Kα)=11.434 mm^(-1) and F(000)=672,the final R=0.0369and wR=0.1086 for 639 observed reflections with I>2σ(I).The crystal structure of Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)features a 3D framework composed of[Ni_(2)O_(2)(PO_(4))_(2)]^(6-)layers interconnected by[MTe_(2)O_(2)(OH)_(4)]^(2+)single chains.Different magnetic susceptibility results at low temperature of the two title compounds confirm that Zn(1)completely occupies the Ni(2)position but not partially substitutes both Ni(1)and Ni(2)position atoms.Additionally,the acentric TeO_(3)(OH)_(2) tetragonal pyramids are aligned in an antiparallel manner,resulting in the crystallization of centrosymmetric(C2/m)crystal structure instead of the non-centrosymmetric crystal structure.The investigation of the origin of centrosymmetric crystal structure with strong dipole moment units provides deeper understanding for future rational design for non-centrosymmetric crystal structure.
