Using the center of figure method and center of mass method,precipitation and heavy precipitation processes caused by No.9 typhoon "Muifa" in 2011 were analyzed based on helicity,and the mechanism of typhoon...Using the center of figure method and center of mass method,precipitation and heavy precipitation processes caused by No.9 typhoon "Muifa" in 2011 were analyzed based on helicity,and the mechanism of typhoon rainfall was interpreted from the relation between helicity and energy. The results showed that horizontal helicity checked the diffusion of nonlinear energy and maintained the development of the system. Precipitation mainly appeared on the southeast of vertical helicity,while heavy precipitation mainly occurred on its southwest. Compared with the center of figure method,the center of mass method had good results,especially for heavy precipitation. Vertical helicity at 700 hPa reflected system deviation in rainfall regions well and had the best correction effect on rainfall intensity and展开更多
This paper introduces a method for forecasting severe weather which is yieded by integrating helicity as a dynamical parameter with K and TOT indexes as thermal parameters.The results of operational tests for two year...This paper introduces a method for forecasting severe weather which is yieded by integrating helicity as a dynamical parameter with K and TOT indexes as thermal parameters.The results of operational tests for two years ure detailed.And the seasonal suitability of the method applications is discussed as well.展开更多
In this paper,we discuss the topological structures of the vortexfilaments and vortex tubes with an exact solution of a straight spiral vortex tube.We find that there are some confusions about the calculation of the h...In this paper,we discuss the topological structures of the vortexfilaments and vortex tubes with an exact solution of a straight spiral vortex tube.We find that there are some confusions about the calculation of the helicities of aknotted vortex filament and some linked vortex filaments by using different methods.We explain how to unify these methods and give the right results.展开更多
In this paper, we briefly introduce the basic questions in the measurements of solar magnetic fields and the possible error sources due to the approximation of the theory of radiation transfer of spectral lines in the...In this paper, we briefly introduce the basic questions in the measurements of solar magnetic fields and the possible error sources due to the approximation of the theory of radiation transfer of spectral lines in the solar atmosphere. We introduce some basic research progress in magnetic field measurement at Huairou Solar Observing Station of National Astronomical Observatories,Chinese Academy of Sciences, especially concerning the non-potentiality in solar active regions, such as the magnetic shear,current and helicity. We also discuss some basic questions for the measurements of the magnetic fields and corresponding challenges for the future studies.展开更多
This paper summarizes current helicity measurements in the solar active regions (ARs). There is a basic agreement with the "hemispheric sign rule (HSR)" of the current helicity among different vector magneto...This paper summarizes current helicity measurements in the solar active regions (ARs). There is a basic agreement with the "hemispheric sign rule (HSR)" of the current helicity among different vector magnetographs through two solar cycles, but there is a large dispersion of the fraction of ARs following the HSR. In our sample, there are 50%-78% ARs in solar cycle 22 and 44%-79% ARs in cycle 23 following the HSR. A variation is also found in the fraction of the ARs following the HSR between different instruments even when the same ARs are selected. The difference also exists for the same instrument when the selected ARs are different. There are some differences in the variation of HSR with solar cycle for the individual helicity parameter inferred from different instruments. Factors which influence the correlation of different data sets are analyzed.展开更多
Following Pevtsov and Latushko, we study the current helicity pattern of the large-scale magnetic field on the photosphere. We use the same technique as theirs to derive the vector magnetic field (Br,Bθ,Bφ) from ful...Following Pevtsov and Latushko, we study the current helicity pattern of the large-scale magnetic field on the photosphere. We use the same technique as theirs to derive the vector magnetic field (Br,Bθ,Bφ) from full-disk longitudinal magnetograms based on the assumption that large-scale magnetic fields evolve rather slowly and the variations of the longitudinal magnetic fields within certain time duration are caused by the changing position angles only. Different from their study, we have calculated the current helicity maps directly from the derived vector magnetograms, rather than from obtaining the latitudinal variation of hc by ignoring the role of Bθ component and averaging Br and Bφ over all solar longitudes. This approach significantly strengthens the evidence of the hemispheric rule presented in the reconstructed vector magnetic field. Our study shows that the established hemispheric sign rule, that is, positive helicity sign in the southern hemisphere and negative helicity sign in the northern hemisphere, is applicable everywhere in the global magnetic field, namely, also evident in weak fields outside active regions, and that the obtained sign pattern is independent of the longitudinal magnetograms and the parameters that we have used.展开更多
Modulating the helicity of self-assemblies of conjugated molecules is important for their application in chiral electronics.In this communication,solvent effect has been investigated on how to modulate the helicity of...Modulating the helicity of self-assemblies of conjugated molecules is important for their application in chiral electronics.In this communication,solvent effect has been investigated on how to modulate the helicity of supramolecular assemblies of sugar-substituted perylenediimide(PTCDI-BAG)by using UV-Vis,circular dichroism spectroscopy and transmission electron microscopy.Left-handed helical nanowires are obtained in the mixed solvent system of both N,N-dimethylformamide/ethanol(DMF/ethanol)and N,N-dimethylacetamide/ethanol(DMAC/ethanol).As changing the solvents into dimethyl sulfoxide/ethanol(DMSO/ethanol),ethylene glycol/ethanol(EG/ethanol),or N-methyl-2-pyrrolidone/ethanol(NMP/ethanol),only right-handed heical nanowires are observed.The chirality of supramolecular structures can be tuned by the controlling of the polarity of the solvents.A theoretical calculation is carried out to explain the chiral optical inversion phenomena of PTCDI-BAG aggregates in different solvents,which reveals that reversed CD spectra is due to the difference of clockwise and anticlockwise rotation of the dimer.展开更多
Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimens...Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow of molten metal and eliminating solidification defects.In this study,the single-winding helical stirring(SWHS)was introduced,offering advantages such as smaller volume and lower electromagnetic shielding compared to traditional helical stirring methods.Following a comprehensive numerical simulation,the stirring parameters of SWHS were adjusted to yoke inclination angle of 43°and frequency of 12 Hz.The higher electromagnetic force and flow velocity in drawing direction,as well as the lower temperature gradient induced by the SWHS,are positive factors for homogeneous solidification of billet.The experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the SWHS process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element segregation.The SWHS process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,SWHS holds great promise as a potential approach for improving the quality of continuous casting billets.展开更多
TAYLOR postulated that the total magnetic helicity is approximately conserved in a highly conductive plasma for resistive dissipation is limited to local regions in it. Using such a postu-
Helicity is an important quantity that represents the topological interpretation of vortices;however,helicity is not a Galilean invariant.In this study,VR helicity density(HVR)is derived via taking the dot product of ...Helicity is an important quantity that represents the topological interpretation of vortices;however,helicity is not a Galilean invariant.In this study,VR helicity density(HVR)is derived via taking the dot product of vorticity with the unit real eigen vector of the velocity gradient tensor when the complex eigenvalues exist.The analytical solution of HVR is derived to resolve it in a local pointwise manner,and the Galilean invariance of HVR is proved.Tip leakage flow structures in a direct numerical simulation of a tip leakage flow model and a delayed detached eddy simulation of a low-speed large-scale axial compressor rotor are extracted using helicity,eigen helicity density and HVR methods.Results show that the utilization of HVR permits the identification and accentuation of concentrated vortices.Vortices identified by HVR appear in more connective states.As in the case of helicity,the sign of HVR distinguishes between primary and secondary vortices,while eigen helicity density fails.The normalized HVR is superior to the normalized helicity density in locating the vortex axis,especially for the induced vortex structures.Hence,HVR is a strong candidate to replace the helicity density,especially when Galilean invariance is required.展开更多
An analysis of light–matter interactions based on symmetries can provide valuable insight,particularly because it reveals which quantities are conserved and which ones can be transformed within a physical system.In t...An analysis of light–matter interactions based on symmetries can provide valuable insight,particularly because it reveals which quantities are conserved and which ones can be transformed within a physical system.In this context,helicity can be a useful addition to more commonly considered observables such as angular momentum.The question arises how to treat helicity,the projection of the total angular momentum onto the linear momentum direction,in practical experiments.In this paper,we put forward a simple but versatile experimental treatment of helicity.We then apply the proposed method to the scattering of light by isolated cylindrical nanoapertures in a gold film.This allows us to study the helicity transformation taking place during the interaction of focused light with the nanoapertures.In particular,we observe from the transmitted light that the scaling of the helicity transformed component with the aperture size is very different to the direct helicity component.展开更多
Raman spectroscopy has been not only a technique for characterizing the composition and lattice structure of materials,but also a platform to explore the electron-photon and electron-phonon couplings.When excited by c...Raman spectroscopy has been not only a technique for characterizing the composition and lattice structure of materials,but also a platform to explore the electron-photon and electron-phonon couplings.When excited by circularly polarized light,the Raman scattered light can carry a spin angular momentum±h,which adds a new degree of freedom to study the Raman scattering process.This review explains the principles of the helicity of Raman scattered light excited by circular polarization,and introduces the recent advances in the fundamentals and applications of helicity-resolved Raman scattering in two dimensional(2 D)materials,including the assignment of overlapped Raman modes,the characterization of exciton-phonon coupling and the application in chiral optics.We hope that this review will give a comprehensive understanding of the helicity selection rule in the Raman scattering process and inspire more exploration on the applications of the helicity of Raman scattered light.展开更多
Responsive polymers have attracted increasing attention for prospective design of smart materials.The development of multifunctional responsive materials is very dependent on polymeric structures that can be manipulat...Responsive polymers have attracted increasing attention for prospective design of smart materials.The development of multifunctional responsive materials is very dependent on polymeric structures that can be manipulated with the change of microenvironment at the molecular level.Herein,we report a type of responsive coordination polymers(RCPs)consisting of dual phenanthroline-oxadiazole(DPO)units and metal Zn^(2+)ions,which can contract from linear structure into topologically helical structure driven by hydrophobic effect while changing the microenvironment from nonpolar solvent to aqueous media.The symmetry breaking of RCPs was confirmed by circular dichroism(CD)spectra and atomic force microscope(AFM)images,clearly demonstrating the intramolecularly contraction-arisen helicity.Moreover,RCPs can intelligently adapt different microenvironments by changing their conformations,as evidenced by a demonstration of biomimetic lipid bilayer-based vesicle experiments.Furthermore,RCPs show significant concentration-dependent transmembrane transport functions,implying that RCPs are able to span cellular membranes to form channels inside the hydrophobic lipid bilayers.At the same time,the electrophysiological conductance experiments further underpin the biomimetic transport functions and channel-based conduction mechanism of RCPs.This study demonstrates an important paradigm of responsive polymers performing microenvironment-induced conformational change and thereof unique functions,and thus provides valuable insights on the development of functional responsive materials.展开更多
The static balance and the geostrophic balance are the common balances in meteorology.All the synoptic systems and most of the mesoscale systems satisfy the above two balances.However,due to the strong convection and ...The static balance and the geostrophic balance are the common balances in meteorology.All the synoptic systems and most of the mesoscale systems satisfy the above two balances.However,due to the strong convection and non-geostrophic feature,many mesoscale systems usually present as static imbalance,and the quasi-geostrophic approximation is no longer attainable.This paper tried to find out a kind of balance that exists for mesoscale convective system.To do this,the concrete mathematics definitions for balance and imbalance equations were defined.Then,it is proposed that the new balance equation should include the divergence,vorticity,and vertical motion simultaneously,and the helicity equation was a good choice for the basis.Finally,the mesoscale balance and imbalance equations were constructed,as well as a new balance model that was based on the helicity,horizontal divergence,vertical vorticity,continuity,and thermal dynamic equations under same approximations.Moreover,the corresponding potential vorticity(PV)inversion technique was introduced.It was pointed out that by using the PV conservation and the potential temperature conservation,the flows of the mesoscale balance model can be deduced,and their comparison with the real fields would give the degree of the imbalance.展开更多
In this study,the non-trival effect of the selection of reference particles for decay angle definitions is demonstrated when constructing the partial-wave amplitude of multi-body decays using helicity formalism.This i...In this study,the non-trival effect of the selection of reference particles for decay angle definitions is demonstrated when constructing the partial-wave amplitude of multi-body decays using helicity formalism.This issue is often ignored in the standard use case of helicity formalism.A new technique is proposed to test the selection of the particle ordering,and it can also be used as a generalized method to calculate the rotation operators that are used for the final-state alignment between different decay chains.Moreover,numerical validations are performed to support the arguments and to verify the effectiveness of the proposed technique.展开更多
In this paper,we calculate the B_(c)→J/ψhelicity form factors(HFFs)up to twist-4 accuracy by using the light-cone sum rules(LCSR)approach.After extrapolating those HFFs to the physically allowable q^(2)region,we inv...In this paper,we calculate the B_(c)→J/ψhelicity form factors(HFFs)up to twist-4 accuracy by using the light-cone sum rules(LCSR)approach.After extrapolating those HFFs to the physically allowable q^(2)region,we investigate the B_(c)^(+)-meson two-body decays and semi-leptonic decays B_(c)^(+)→J/ψ+(P,V,ℓ^(+)ν_(ℓ)),where P/V stand for light pseudoscalar and vector mesons,respectively.The branching fractions can be derived using the CKM matrix element and the B_(c)lifetime from the Particle Data Group,and we obtain B(B^(+)_(c)→J/ψπ^(+))=(0.136+0.002−0.002)%,B(B^(+)_(c)→J/ψK^(+))=(0.010+0.000−0.000)%,B(B^(+)_(c)→J/ψρ+)=(0.768+0.029−0.033)%,B(B^(+)_(c)→J/ψK^(∗+))=(0.043+0.001−0.001)%,B(B^(+)_(c)→J/ψ_(μ)+ν_(μ))=(2.802+0.526−0.675)%and B(B^(+)_(c)→J/ψτ^(+)ν_(τ))=(0.559+0.131−0.170)%.We then obtain R_(π^(+)/μ+ν_(μ))=0.048+0.009−0.012 and R_(K^(+)/π^(+))=0.075+0.005−0.005,which agree with the LHCb measured value within 1σ-error.We also obtain R_(J/ψ)=0.199+0.060−0.077,which like other theoretical predictions,is consistent with the LHCb measured value within 2σ-error.These imply that the HFFs under the LCSR approach are also applicable to the B+c meson two-body decays and semi-leptonic decays B+c→J/ψ+(P,V,ℓ^(+)ν_(ℓ)),and the HFFs obtained using LCSR in a new way implies that there may be new physics in the B_(c)→J/ψℓ^(+)ν_(ℓ)semi-leptonic decays.展开更多
We study the structure of nonstrange baryons by analytically calculating the electromagnetic transition helicity amplitudes of the nucleon andΔresonances.We employ an improved hypercentral constituent quark model and...We study the structure of nonstrange baryons by analytically calculating the electromagnetic transition helicity amplitudes of the nucleon andΔresonances.We employ an improved hypercentral constituent quark model and obtain the corresponding eigenenergies and eigenfunctions in closed forms.Then,we calculate the transverse and longitudinal helicity amplitudes for nucleon andΔresonances.The comparison of evaluated observables and experimental data indicates good agreement between the proposed model and available data.展开更多
Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H...Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers.展开更多
文摘Using the center of figure method and center of mass method,precipitation and heavy precipitation processes caused by No.9 typhoon "Muifa" in 2011 were analyzed based on helicity,and the mechanism of typhoon rainfall was interpreted from the relation between helicity and energy. The results showed that horizontal helicity checked the diffusion of nonlinear energy and maintained the development of the system. Precipitation mainly appeared on the southeast of vertical helicity,while heavy precipitation mainly occurred on its southwest. Compared with the center of figure method,the center of mass method had good results,especially for heavy precipitation. Vertical helicity at 700 hPa reflected system deviation in rainfall regions well and had the best correction effect on rainfall intensity and
文摘This paper introduces a method for forecasting severe weather which is yieded by integrating helicity as a dynamical parameter with K and TOT indexes as thermal parameters.The results of operational tests for two years ure detailed.And the seasonal suitability of the method applications is discussed as well.
基金This work is supported by the National Basic Research Important Project"Nonlinear Science"
文摘In this paper,we discuss the topological structures of the vortexfilaments and vortex tubes with an exact solution of a straight spiral vortex tube.We find that there are some confusions about the calculation of the helicities of aknotted vortex filament and some linked vortex filaments by using different methods.We explain how to unify these methods and give the right results.
基金supported by the National Natural Science Foundation of China(Grant Nos.11673033,11911530089,11427803,and 11427901)the Huairou Solar Observing Station,Chinese Academy of Sciences
文摘In this paper, we briefly introduce the basic questions in the measurements of solar magnetic fields and the possible error sources due to the approximation of the theory of radiation transfer of spectral lines in the solar atmosphere. We introduce some basic research progress in magnetic field measurement at Huairou Solar Observing Station of National Astronomical Observatories,Chinese Academy of Sciences, especially concerning the non-potentiality in solar active regions, such as the magnetic shear,current and helicity. We also discuss some basic questions for the measurements of the magnetic fields and corresponding challenges for the future studies.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10611120338, 10473016, 10673016, 60673158, 10733020, and10978015)the National Basic Research Program of China (Grant No. 2006CB806301)the Important Directional Project of Chinese Academy of Sciences (Grant No. KLCX2-YW-T04)
文摘This paper summarizes current helicity measurements in the solar active regions (ARs). There is a basic agreement with the "hemispheric sign rule (HSR)" of the current helicity among different vector magnetographs through two solar cycles, but there is a large dispersion of the fraction of ARs following the HSR. In our sample, there are 50%-78% ARs in solar cycle 22 and 44%-79% ARs in cycle 23 following the HSR. A variation is also found in the fraction of the ARs following the HSR between different instruments even when the same ARs are selected. The difference also exists for the same instrument when the selected ARs are different. There are some differences in the variation of HSR with solar cycle for the individual helicity parameter inferred from different instruments. Factors which influence the correlation of different data sets are analyzed.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40636031 and 10778723)the Important Directional Projects of Chinese Academy of Sciences (Grant No. KLCX2-YW-T04)the National Basic Research Program of China (Grant No. 2006CB806301)
文摘Following Pevtsov and Latushko, we study the current helicity pattern of the large-scale magnetic field on the photosphere. We use the same technique as theirs to derive the vector magnetic field (Br,Bθ,Bφ) from full-disk longitudinal magnetograms based on the assumption that large-scale magnetic fields evolve rather slowly and the variations of the longitudinal magnetic fields within certain time duration are caused by the changing position angles only. Different from their study, we have calculated the current helicity maps directly from the derived vector magnetograms, rather than from obtaining the latitudinal variation of hc by ignoring the role of Bθ component and averaging Br and Bφ over all solar longitudes. This approach significantly strengthens the evidence of the hemispheric rule presented in the reconstructed vector magnetic field. Our study shows that the established hemispheric sign rule, that is, positive helicity sign in the southern hemisphere and negative helicity sign in the northern hemisphere, is applicable everywhere in the global magnetic field, namely, also evident in weak fields outside active regions, and that the obtained sign pattern is independent of the longitudinal magnetograms and the parameters that we have used.
基金supported by the National Natural Science Foundation of China (Grant Nos.91027031 and 21125420)the Ministry of Science and Technology of China (Grant No.2011CB932300)the Chinese Academy of Sciences.
文摘Modulating the helicity of self-assemblies of conjugated molecules is important for their application in chiral electronics.In this communication,solvent effect has been investigated on how to modulate the helicity of supramolecular assemblies of sugar-substituted perylenediimide(PTCDI-BAG)by using UV-Vis,circular dichroism spectroscopy and transmission electron microscopy.Left-handed helical nanowires are obtained in the mixed solvent system of both N,N-dimethylformamide/ethanol(DMF/ethanol)and N,N-dimethylacetamide/ethanol(DMAC/ethanol).As changing the solvents into dimethyl sulfoxide/ethanol(DMSO/ethanol),ethylene glycol/ethanol(EG/ethanol),or N-methyl-2-pyrrolidone/ethanol(NMP/ethanol),only right-handed heical nanowires are observed.The chirality of supramolecular structures can be tuned by the controlling of the polarity of the solvents.A theoretical calculation is carried out to explain the chiral optical inversion phenomena of PTCDI-BAG aggregates in different solvents,which reveals that reversed CD spectra is due to the difference of clockwise and anticlockwise rotation of the dimer.
基金financially supported by the National Key R&D Projects(No.2021YFB3702000)the Regional Company Projects in Ansteel Beijing Research Institute(No.2022BJB07GF&No.2022BJB-13GF)。
文摘Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow of molten metal and eliminating solidification defects.In this study,the single-winding helical stirring(SWHS)was introduced,offering advantages such as smaller volume and lower electromagnetic shielding compared to traditional helical stirring methods.Following a comprehensive numerical simulation,the stirring parameters of SWHS were adjusted to yoke inclination angle of 43°and frequency of 12 Hz.The higher electromagnetic force and flow velocity in drawing direction,as well as the lower temperature gradient induced by the SWHS,are positive factors for homogeneous solidification of billet.The experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the SWHS process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element segregation.The SWHS process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,SWHS holds great promise as a potential approach for improving the quality of continuous casting billets.
文摘TAYLOR postulated that the total magnetic helicity is approximately conserved in a highly conductive plasma for resistive dissipation is limited to local regions in it. Using such a postu-
基金supported by the National Natural Science Foundation of China(Nos.52106039,51976006 and 51790513)the National Science and Technology Major Project,China(No.2017-Ⅱ-003-0015)+3 种基金the Aeronautical Science Foundation of China(No.2018ZB51013)the Open Fund from State Key Laboratory of Aerodynamics,China(No.SKLA2019A0101)the China Postdoctoral Science Foundation(Nos.2020M670097 and 2021T140037)also supported by the High-Performance Computing(HPC)resources at Beihang University,China。
文摘Helicity is an important quantity that represents the topological interpretation of vortices;however,helicity is not a Galilean invariant.In this study,VR helicity density(HVR)is derived via taking the dot product of vorticity with the unit real eigen vector of the velocity gradient tensor when the complex eigenvalues exist.The analytical solution of HVR is derived to resolve it in a local pointwise manner,and the Galilean invariance of HVR is proved.Tip leakage flow structures in a direct numerical simulation of a tip leakage flow model and a delayed detached eddy simulation of a low-speed large-scale axial compressor rotor are extracted using helicity,eigen helicity density and HVR methods.Results show that the utilization of HVR permits the identification and accentuation of concentrated vortices.Vortices identified by HVR appear in more connective states.As in the case of helicity,the sign of HVR distinguishes between primary and secondary vortices,while eigen helicity density fails.The normalized HVR is superior to the normalized helicity density in locating the vortex axis,especially for the induced vortex structures.Hence,HVR is a strong candidate to replace the helicity density,especially when Galilean invariance is required.
基金This work was funded by the Centre of Excellence for Engineered Quantum SystemsGM-T is also funded by the Future Fellowship program
文摘An analysis of light–matter interactions based on symmetries can provide valuable insight,particularly because it reveals which quantities are conserved and which ones can be transformed within a physical system.In this context,helicity can be a useful addition to more commonly considered observables such as angular momentum.The question arises how to treat helicity,the projection of the total angular momentum onto the linear momentum direction,in practical experiments.In this paper,we put forward a simple but versatile experimental treatment of helicity.We then apply the proposed method to the scattering of light by isolated cylindrical nanoapertures in a gold film.This allows us to study the helicity transformation taking place during the interaction of focused light with the nanoapertures.In particular,we observe from the transmitted light that the scaling of the helicity transformed component with the aperture size is very different to the direct helicity component.
基金supported by the Ministry of Science and Technology of China(2016YFA0200100,2018YFA0703502)the National Natural Science Foundation of China(52021006,51720105003,21790052,21974004)+1 种基金Beijing National Laboratory for Molecular Sciences(BNLMS-CXTD-202001)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB36030100)。
文摘Raman spectroscopy has been not only a technique for characterizing the composition and lattice structure of materials,but also a platform to explore the electron-photon and electron-phonon couplings.When excited by circularly polarized light,the Raman scattered light can carry a spin angular momentum±h,which adds a new degree of freedom to study the Raman scattering process.This review explains the principles of the helicity of Raman scattered light excited by circular polarization,and introduces the recent advances in the fundamentals and applications of helicity-resolved Raman scattering in two dimensional(2 D)materials,including the assignment of overlapped Raman modes,the characterization of exciton-phonon coupling and the application in chiral optics.We hope that this review will give a comprehensive understanding of the helicity selection rule in the Raman scattering process and inspire more exploration on the applications of the helicity of Raman scattered light.
基金This work was supported by the National Natural Science Foundation of China(Nos.22071078,92156012 and 21722403)the Program for Jilin University Science and Technology Innovative Research Team(JLUSTIRT),China(No.2019TD-36).
文摘Responsive polymers have attracted increasing attention for prospective design of smart materials.The development of multifunctional responsive materials is very dependent on polymeric structures that can be manipulated with the change of microenvironment at the molecular level.Herein,we report a type of responsive coordination polymers(RCPs)consisting of dual phenanthroline-oxadiazole(DPO)units and metal Zn^(2+)ions,which can contract from linear structure into topologically helical structure driven by hydrophobic effect while changing the microenvironment from nonpolar solvent to aqueous media.The symmetry breaking of RCPs was confirmed by circular dichroism(CD)spectra and atomic force microscope(AFM)images,clearly demonstrating the intramolecularly contraction-arisen helicity.Moreover,RCPs can intelligently adapt different microenvironments by changing their conformations,as evidenced by a demonstration of biomimetic lipid bilayer-based vesicle experiments.Furthermore,RCPs show significant concentration-dependent transmembrane transport functions,implying that RCPs are able to span cellular membranes to form channels inside the hydrophobic lipid bilayers.At the same time,the electrophysiological conductance experiments further underpin the biomimetic transport functions and channel-based conduction mechanism of RCPs.This study demonstrates an important paradigm of responsive polymers performing microenvironment-induced conformational change and thereof unique functions,and thus provides valuable insights on the development of functional responsive materials.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2012CB417201)National Natural Science Foundation of China(91437215,41475100,and 41375052)
文摘The static balance and the geostrophic balance are the common balances in meteorology.All the synoptic systems and most of the mesoscale systems satisfy the above two balances.However,due to the strong convection and non-geostrophic feature,many mesoscale systems usually present as static imbalance,and the quasi-geostrophic approximation is no longer attainable.This paper tried to find out a kind of balance that exists for mesoscale convective system.To do this,the concrete mathematics definitions for balance and imbalance equations were defined.Then,it is proposed that the new balance equation should include the divergence,vorticity,and vertical motion simultaneously,and the helicity equation was a good choice for the basis.Finally,the mesoscale balance and imbalance equations were constructed,as well as a new balance model that was based on the helicity,horizontal divergence,vertical vorticity,continuity,and thermal dynamic equations under same approximations.Moreover,the corresponding potential vorticity(PV)inversion technique was introduced.It was pointed out that by using the PV conservation and the potential temperature conservation,the flows of the mesoscale balance model can be deduced,and their comparison with the real fields would give the degree of the imbalance.
基金This work was supported in part by National Key R&D Program of China(2017YFA0402103,2020YFA0406400)National Natural Science Foundation of China(11775122,11822506,11975015)Fundamental Research Funds for the Central Universities。
文摘In this study,the non-trival effect of the selection of reference particles for decay angle definitions is demonstrated when constructing the partial-wave amplitude of multi-body decays using helicity formalism.This issue is often ignored in the standard use case of helicity formalism.A new technique is proposed to test the selection of the particle ordering,and it can also be used as a generalized method to calculate the rotation operators that are used for the final-state alignment between different decay chains.Moreover,numerical validations are performed to support the arguments and to verify the effectiveness of the proposed technique.
基金Supported in part by the National Natural Science Foundation of China(11765007,11625520,11947406,12047564)the Project of Guizhou Provincial Department of Science and Technology(KY[2019]1171)+4 种基金the Project of Guizhou Provincial Department of Education(KY[2021]030)the China Postdoctoral Science Foundation(2019TQ0329,2020M670476)the Chongqing Graduate Research and Innovation Foundation(ydstd1912)the Fundamental Research Funds for the Central Universities(2020CQJQY-Z003)the Project of Guizhou Minzu University(GZMU[2019]YB19)。
文摘In this paper,we calculate the B_(c)→J/ψhelicity form factors(HFFs)up to twist-4 accuracy by using the light-cone sum rules(LCSR)approach.After extrapolating those HFFs to the physically allowable q^(2)region,we investigate the B_(c)^(+)-meson two-body decays and semi-leptonic decays B_(c)^(+)→J/ψ+(P,V,ℓ^(+)ν_(ℓ)),where P/V stand for light pseudoscalar and vector mesons,respectively.The branching fractions can be derived using the CKM matrix element and the B_(c)lifetime from the Particle Data Group,and we obtain B(B^(+)_(c)→J/ψπ^(+))=(0.136+0.002−0.002)%,B(B^(+)_(c)→J/ψK^(+))=(0.010+0.000−0.000)%,B(B^(+)_(c)→J/ψρ+)=(0.768+0.029−0.033)%,B(B^(+)_(c)→J/ψK^(∗+))=(0.043+0.001−0.001)%,B(B^(+)_(c)→J/ψ_(μ)+ν_(μ))=(2.802+0.526−0.675)%and B(B^(+)_(c)→J/ψτ^(+)ν_(τ))=(0.559+0.131−0.170)%.We then obtain R_(π^(+)/μ+ν_(μ))=0.048+0.009−0.012 and R_(K^(+)/π^(+))=0.075+0.005−0.005,which agree with the LHCb measured value within 1σ-error.We also obtain R_(J/ψ)=0.199+0.060−0.077,which like other theoretical predictions,is consistent with the LHCb measured value within 2σ-error.These imply that the HFFs under the LCSR approach are also applicable to the B+c meson two-body decays and semi-leptonic decays B+c→J/ψ+(P,V,ℓ^(+)ν_(ℓ)),and the HFFs obtained using LCSR in a new way implies that there may be new physics in the B_(c)→J/ψℓ^(+)ν_(ℓ)semi-leptonic decays.
文摘We study the structure of nonstrange baryons by analytically calculating the electromagnetic transition helicity amplitudes of the nucleon andΔresonances.We employ an improved hypercentral constituent quark model and obtain the corresponding eigenenergies and eigenfunctions in closed forms.Then,we calculate the transverse and longitudinal helicity amplitudes for nucleon andΔresonances.The comparison of evaluated observables and experimental data indicates good agreement between the proposed model and available data.
基金financial supports from the 973 Program(No.2015CB856502)the National Natural Science Foundation of China(No.21672026)。
文摘Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers.
