The elastic property-crystal structure relations provide a foundation to design new materials with desired properties and understand the chemical decomposition and explosion of energetic materials. The supramolecular structural unit was proposed as the smallest chemical unit to quantitatively characterize the elastic anisotropy of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX). The supramolecular structural unit refers to the nearest-neighbor coordination polyhedron of one molecule. The supramolecular structural unit of RDX was composed of 15 molecules, which were analyzed by the total molecular number density and the density of intermolecular interactions. The elastic modulus model was established based on the following assumptions: (i) the RDX molecules were spherical and rigid-body; (ii) the intermolecular interactions were viewed as the linear spring, i.e., bond-spring model; (iii) the molecules were close-packed with the series mode. The elastic modulus model based on the supramolecular structural unit demonstrated that the elastic modulus was intrinsically determined by the total molecular number, the equilibrium distance of the molecular pair, the intermolecular force constant, and the angle between the intermolecular interactions and the normal to crystal face. The intermolecular force constant was calculated as the second derivative of the intermolecular interactions with regard to the equilibrium centroid distances. The intermolecular interactions were expressed as the sum of van der Waals and electrostatic interactions calculated by COMPASS (condensed-phase optimized molecular potentials for atomistic simulation studies) II forcefield. The calculated elastic moduli were 21.7, 17.1, 20.1, 19.1, and 15.3 GPa for RDX (100), (010), (001), (210), and (021) crystal faces, respectively. The calculation results were consistent with the theoretical values computed by the density functional theory. Excluding RDX(001), the calculated elastic moduli agreed with the experimental results measured by the resonant ultrasound spectroscopy (RUS), impulsive stimulated thermal scattering (ISTS), Brillouin spectroscopy, and nanoindentation methods. The theoretical values (20.1 GPa) of RDX(001) overestimated the experimental values with the range of 15.9~16.6 GPa. The reason can be attributed to the rigid-body approximation for flexible molecules, which ignored the motion and deformation of the ring and NO2 groups when the external loads were applied to RDX(001). The results suggested that the supramolecular structural unit can be the smallest chemical unit to quantitatively characterize the elastic anisotropy of RDX and the elastic anisotropy was mainly attributed to the angle between the intermolecular interactions and the normal to crystal face.
{"title":"Elastic Anisotropy of RDX Studied by the Supramolecular Structural Unit","authors":"Wei Fu-jing, Zhang Wei-bin, Dong Chuang, Chen Hua","doi":"10.7498/aps.72.20221615","DOIUrl":"https://doi.org/10.7498/aps.72.20221615","url":null,"abstract":"The elastic property-crystal structure relations provide a foundation to design new materials with desired properties and understand the chemical decomposition and explosion of energetic materials. The supramolecular structural unit was proposed as the smallest chemical unit to quantitatively characterize the elastic anisotropy of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX). The supramolecular structural unit refers to the nearest-neighbor coordination polyhedron of one molecule. The supramolecular structural unit of RDX was composed of 15 molecules, which were analyzed by the total molecular number density and the density of intermolecular interactions. The elastic modulus model was established based on the following assumptions: (i) the RDX molecules were spherical and rigid-body; (ii) the intermolecular interactions were viewed as the linear spring, i.e., bond-spring model; (iii) the molecules were close-packed with the series mode. The elastic modulus model based on the supramolecular structural unit demonstrated that the elastic modulus was intrinsically determined by the total molecular number, the equilibrium distance of the molecular pair, the intermolecular force constant, and the angle between the intermolecular interactions and the normal to crystal face. The intermolecular force constant was calculated as the second derivative of the intermolecular interactions with regard to the equilibrium centroid distances. The intermolecular interactions were expressed as the sum of van der Waals and electrostatic interactions calculated by COMPASS (condensed-phase optimized molecular potentials for atomistic simulation studies) II forcefield. The calculated elastic moduli were 21.7, 17.1, 20.1, 19.1, and 15.3 GPa for RDX (100), (010), (001), (210), and (021) crystal faces, respectively. The calculation results were consistent with the theoretical values computed by the density functional theory. Excluding RDX(001), the calculated elastic moduli agreed with the experimental results measured by the resonant ultrasound spectroscopy (RUS), impulsive stimulated thermal scattering (ISTS), Brillouin spectroscopy, and nanoindentation methods. The theoretical values (20.1 GPa) of RDX(001) overestimated the experimental values with the range of 15.9~16.6 GPa. The reason can be attributed to the rigid-body approximation for flexible molecules, which ignored the motion and deformation of the ring and NO2 groups when the external loads were applied to RDX(001). The results suggested that the supramolecular structural unit can be the smallest chemical unit to quantitatively characterize the elastic anisotropy of RDX and the elastic anisotropy was mainly attributed to the angle between the intermolecular interactions and the normal to crystal face.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"59 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80455554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since the Whitham modulation theory was first proposed in 1965, it has been widely concerned because of its superiority in studying dispersive fluid dynamics and dealing with discontinuous initial value problems. In this paper, the Whitham modulation theory of the defocusing nonlinear Schrödinger equation is developed, the classification and evolution of the solutions of discontinuous initial value problem are studied. Moreover, the region of dispersive shock wave, the region rarefaction wave, the region of unmodulated wave and the plateau region are distinguished. Particularly, the correctness of the results is verified by direct numerical simulation. Specifically, the solutions of 0-phase and 1-phase and their corresponding Whitham equations are derived by the finite gap integration method. Also the Whitham equation of genus N corresponding to the N-phase periodic wave solution is derived. The basic structures of rarefaction wave and dispersive shock wave are given, in which the boundaries of the regions are calculated in detail. The Riemann invariants and density distributions of dispersive fluids in each case are discussed. When the initial value is fixed as a special one, the vacuum point is considered and analyzed in detail. In addition, the oscillating front and the soliton front in the dispersive shock wave are considered. In fact, the Whitham modulation theory has many wonderful applications in real physics and engineering. The dam problem is investigated as a special Riemann problem, the piston problem of dispersive fluid is analyzed, and the novel undular bores are found.
{"title":"The Whitham Modulation Theory of Defocusing Nonlinear Schrödinger Equation and the Classification and Evolutions of Solutions With Initial Discontinuity","authors":"Gong Rui-Zhi, Wang Deng-Shan","doi":"10.7498/aps.72.20230172","DOIUrl":"https://doi.org/10.7498/aps.72.20230172","url":null,"abstract":"Since the Whitham modulation theory was first proposed in 1965, it has been widely concerned because of its superiority in studying dispersive fluid dynamics and dealing with discontinuous initial value problems. In this paper, the Whitham modulation theory of the defocusing nonlinear Schrödinger equation is developed, the classification and evolution of the solutions of discontinuous initial value problem are studied. Moreover, the region of dispersive shock wave, the region rarefaction wave, the region of unmodulated wave and the plateau region are distinguished. Particularly, the correctness of the results is verified by direct numerical simulation. Specifically, the solutions of 0-phase and 1-phase and their corresponding Whitham equations are derived by the finite gap integration method. Also the Whitham equation of genus N corresponding to the N-phase periodic wave solution is derived. The basic structures of rarefaction wave and dispersive shock wave are given, in which the boundaries of the regions are calculated in detail. The Riemann invariants and density distributions of dispersive fluids in each case are discussed. When the initial value is fixed as a special one, the vacuum point is considered and analyzed in detail. In addition, the oscillating front and the soliton front in the dispersive shock wave are considered. In fact, the Whitham modulation theory has many wonderful applications in real physics and engineering. The dam problem is investigated as a special Riemann problem, the piston problem of dispersive fluid is analyzed, and the novel undular bores are found.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"2 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79036568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Magnetic topological insulators have been a significant focus in the research of condensed matter physics over the past decade. The intricate interplay between the nontrivial band topology and spin, orbit, charge, and dimensionality degrees of freedom can give rise to a plethora of exotic topological quantum states and topological phase transitions. Measuring the transport properties of magnetic topological insulators is a crucial approach to exploring their exotic properties, which bears significant scientific importance in deepening our understanding of topological quantum states. Simultaneously, it also holds substantial potential for application in the development of novel low-power electronic devices. This article reviews the recent experimental advancements in transport studies of magnetic topological insulators in the past few years, encompassing the quantum anomalous Hall effect and topological quantum phase transitions in magnetically doped topological insulators, the quantum anomalous Hall phase, axion insulator phase and Chern insulator phase in intrinsic antiferromagnetic topological insulator MnBi2Te4, as well as the helical phase emerged from the Chern insulator in pulsed high magnetic fields. Finally, this article analyzes the future direction of development in magnetic topological insulators and the transport phenomena that remain to be understood in these systems, offering insights and perspectives on the potential breakthroughs to be achieved in this area of research.
{"title":"Quantum Transport Phenomena in Magnetic Topological Insulators","authors":"Chang Liu, Yayu Wang","doi":"10.7498/aps.72.20230690","DOIUrl":"https://doi.org/10.7498/aps.72.20230690","url":null,"abstract":"Magnetic topological insulators have been a significant focus in the research of condensed matter physics over the past decade. The intricate interplay between the nontrivial band topology and spin, orbit, charge, and dimensionality degrees of freedom can give rise to a plethora of exotic topological quantum states and topological phase transitions. Measuring the transport properties of magnetic topological insulators is a crucial approach to exploring their exotic properties, which bears significant scientific importance in deepening our understanding of topological quantum states. Simultaneously, it also holds substantial potential for application in the development of novel low-power electronic devices. This article reviews the recent experimental advancements in transport studies of magnetic topological insulators in the past few years, encompassing the quantum anomalous Hall effect and topological quantum phase transitions in magnetically doped topological insulators, the quantum anomalous Hall phase, axion insulator phase and Chern insulator phase in intrinsic antiferromagnetic topological insulator MnBi2Te4, as well as the helical phase emerged from the Chern insulator in pulsed high magnetic fields. Finally, this article analyzes the future direction of development in magnetic topological insulators and the transport phenomena that remain to be understood in these systems, offering insights and perspectives on the potential breakthroughs to be achieved in this area of research.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"2 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76282749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuan Hong-Rui, Liu Tao, Zhu Tian-Xin, Liu Yun, Li Xiang, Chen Yang, Duan Chuan-Xi
Sulfur hexafluoride (SF６) is a greenhouse gas of very long lifetime. Its infrared absorption spectrum is very important for modeling the atmospheric radiation balances. SF６ is also a prototypical system for studying the principles and techniques of laser isotope separation using powerful infrared lasers. As a very heavy molecule, the infrared spectrum of SF６ at room temperature is very dense, which poses a great challenge for monitoring the relative abundances of different SF６ isotopomers by direct absorption spectroscopy. Supersonic jet expansions have been used widely to simplify gas phase molecular spectra. In this work, astigmatic multi-pass absorption cell and distributed feed-back quantum cascade lasers (QCLs) are used to measure jet-cooled rovibrational absorption spectrum of 32SF６ and 33SF６ at 10.6 μm. The spectrometer works in a segmented rapid-scan mode. The gas mixtures (SF6:Ar:He = 0.12:1:100) are expanded through a 80 mm×300 μm pulsed slit nozzle. Two QCLs running at room temperature are used and each one covers a spectral range of about 3.0 cm-1. The v3 fundamental bands of both 32SF６ and 33SF６ are observed. The rotational temperature of 32SF６ and 33SF６ in the ground state in the supersonic jet is estimated to be about 10 K and the linewidth is about 0.0008 cm-1 by comparing the simulated and observed spectrum with the PGOPHER program. A new weak vibrational band centered around 941.0 cm-1 is observed and tentatively assigned to the v1+v2+v3-(v1+v2)hot band of 32SF６. The effective Hamiltonian used to analyze the rovibrational spectrum of SF６ is briefly introduced. A simplified rotational analysis for this hot band is performed with the XTDS program developed by the Dijon group. The band-origin of this hot band is determined to be 941.1785(21) cm-1. The rotational temperature of this hot band is estimated to be about 50 K. A new scheme by measuring the jet-cooled absorption spectrum of this hot band of 32SF6 and the v3 fundamental band of 33SF６ is proposed for measuring the relative abundance of 33SF６／32SF６.
{"title":"High-resolution jet-cooled laser absorption spectroscopy of SF6 at 10.6 μm","authors":"Yuan Hong-Rui, Liu Tao, Zhu Tian-Xin, Liu Yun, Li Xiang, Chen Yang, Duan Chuan-Xi","doi":"10.7498/aps.72.20222285","DOIUrl":"https://doi.org/10.7498/aps.72.20222285","url":null,"abstract":"Sulfur hexafluoride (SF<sub>６</sub>) is a greenhouse gas of very long lifetime. Its infrared absorption spectrum is very important for modeling the atmospheric radiation balances. SF<sub>６</sub> is also a prototypical system for studying the principles and techniques of laser isotope separation using powerful infrared lasers. As a very heavy molecule, the infrared spectrum of SF<sub>６</sub> at room temperature is very dense, which poses a great challenge for monitoring the relative abundances of different SF<sub>６</sub> isotopomers by direct absorption spectroscopy. Supersonic jet expansions have been used widely to simplify gas phase molecular spectra. In this work, astigmatic multi-pass absorption cell and distributed feed-back quantum cascade lasers (QCLs) are used to measure jet-cooled rovibrational absorption spectrum of <sup>32</sup>SF<sub>６</sub> and <sup>33</sup>SF<sub>６</sub> at 10.6 μm. The spectrometer works in a segmented rapid-scan mode. The gas mixtures (SF<sub>6</sub>:Ar:He = 0.12:1:100) are expanded through a 80 mm×300 μm pulsed slit nozzle. Two QCLs running at room temperature are used and each one covers a spectral range of about 3.0 cm<sup>-1</sup>. The <i>v</i><sub>3</sub> fundamental bands of both <sup>32</sup>SF<sub>６</sub> and <sup>33</sup>SF<sub>６</sub> are observed. The rotational temperature of <sup>32</sup>SF<sub>６</sub> and <sup>33</sup>SF<sub>６</sub> in the ground state in the supersonic jet is estimated to be about 10 K and the linewidth is about 0.0008 cm<sup>-1</sup> by comparing the simulated and observed spectrum with the PGOPHER program. A new weak vibrational band centered around 941.0 cm<sup>-1</sup> is observed and tentatively assigned to the <i>v</i><sub>1</sub>+<i>v</i><sub>2</sub>+<i>v</i><sub>3</sub>-(<i>v</i><sub>1</sub>+<i>v</i><sub>2</sub>)hot band of <sup>32</sup>SF<sub>６</sub>. The effective Hamiltonian used to analyze the rovibrational spectrum of SF<sub>６</sub> is briefly introduced. A simplified rotational analysis for this hot band is performed with the XTDS program developed by the Dijon group. The band-origin of this hot band is determined to be 941.1785(21) cm<sup>-1</sup>. The rotational temperature of this hot band is estimated to be about 50 K. A new scheme by measuring the jet-cooled absorption spectrum of this hot band of <sup>32</sup>SF<sub>6</sub> and the <i>v</i><sub>3</sub> fundamental band of <sup>33</sup>SF<sub>６</sub> is proposed for measuring the relative abundance of <sup>33</sup>SF<sub>６</sub>／<sup>32</sup>SF<sub>６</sub>.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"135 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76611261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quantum computing is a new way to processing quantum information by using superposition and entanglement of the quantum system. Quantum state's vast Hilbert space allows it to perform operations that classical computers cannot compared with classical computing, quantum computing has unique advantages in dealing with some complex problems, so it has attracted wide attention. Computing a single qubit is the first of seven fundamental stages needed to achieve a large-scale quantum computer that is universal, scalable and fault-tolerant. In other words, the primary task of quantum computing is the careful preparation and precise regulation of qubits. At present, the physical systems that can be used as qubits include superconducting qubits, semiconductor qubits, ion trap systems and nitrogen-vacancy (NV) color centers, etc. These physical systems have made great progress in terms of decoherence time and scalability. Due to the vulnerability of qubits, ambient thermal noise can cause quantum decoherence, which greatly affects the fidelity of qubits. Improving the fidelity of qubits is therefore a key step towards large-scale quantum computing. Based on the dipole field driven qubit, the stochastic dynamic structure decomposition method is adopted and the Kubo-Einstein fluctuation-dissipation theorem is applied to study the qubit control in a thermal noise environment. The dipole field has components in three directions, not just in one plane, which allows for more flexible control of quantum states. Without considering the noise, the quantum state can reach the target state 100%. In the noisy environment, thermal noise will cause the deviation between the actual final state and the target final state caused by thermal fluctuation, which becomes the main factor affecting the quantum fidelity. The influence of thermal noise is related to temperature and the evolution trajectory of quantum states. Therefore, this paper proposes an optimization scheme to improve the qubit fidelity in the thermal noise environment. The feasibility of this method is verified by numerical calculation, which can provide a new solution for further guidance and evaluation of the experiment. The scheme is suitable for qubit systems of various physical control fields. For example, in semiconductor qubits and nitrogen vacancy center qubits. This work may have more applications in the future as quantum manipulation technology continues to evolve. This work can also be extended to multi-qubit systems, the details of which will be covered in future work.
{"title":"Qubit dynamics driven by dipole field in thermal noise environment","authors":"Xiong Fan, Chen Yong-Cong, Ao Ping","doi":"10.7498/aps.72.20230625","DOIUrl":"https://doi.org/10.7498/aps.72.20230625","url":null,"abstract":"Quantum computing is a new way to processing quantum information by using superposition and entanglement of the quantum system. Quantum state's vast Hilbert space allows it to perform operations that classical computers cannot compared with classical computing, quantum computing has unique advantages in dealing with some complex problems, so it has attracted wide attention. Computing a single qubit is the first of seven fundamental stages needed to achieve a large-scale quantum computer that is universal, scalable and fault-tolerant. In other words, the primary task of quantum computing is the careful preparation and precise regulation of qubits. At present, the physical systems that can be used as qubits include superconducting qubits, semiconductor qubits, ion trap systems and nitrogen-vacancy (NV) color centers, etc. These physical systems have made great progress in terms of decoherence time and scalability. Due to the vulnerability of qubits, ambient thermal noise can cause quantum decoherence, which greatly affects the fidelity of qubits. Improving the fidelity of qubits is therefore a key step towards large-scale quantum computing. Based on the dipole field driven qubit, the stochastic dynamic structure decomposition method is adopted and the Kubo-Einstein fluctuation-dissipation theorem is applied to study the qubit control in a thermal noise environment. The dipole field has components in three directions, not just in one plane, which allows for more flexible control of quantum states. Without considering the noise, the quantum state can reach the target state 100%. In the noisy environment, thermal noise will cause the deviation between the actual final state and the target final state caused by thermal fluctuation, which becomes the main factor affecting the quantum fidelity. The influence of thermal noise is related to temperature and the evolution trajectory of quantum states. Therefore, this paper proposes an optimization scheme to improve the qubit fidelity in the thermal noise environment. The feasibility of this method is verified by numerical calculation, which can provide a new solution for further guidance and evaluation of the experiment. The scheme is suitable for qubit systems of various physical control fields. For example, in semiconductor qubits and nitrogen vacancy center qubits. This work may have more applications in the future as quantum manipulation technology continues to evolve. This work can also be extended to multi-qubit systems, the details of which will be covered in future work.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"95 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78359186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gao Ming-Zhu, Liu Chun-Liang, Wang Hong-Guang, Li Yong-Dong, Lin Shu, Zhai Yong-Gui
As a regulator of cation activity in living cells, KcsA (K+ Conduction and Selectivity Architecture) potassium channel plays an important role in the depolarization and repolarization of nerve cell action potential. In this paper, Brownian Dynamics (BD) method is used to simulate the electrical characteristics of the actual KcsA potassium channel systematically. The PMF of ions in the channel under electrostatic field, the current-voltage characteristic curve of symmetric solution and asymmetric solution, the ion concentration distribution curve in the axial direction of the channel, and the conduction-concentration curve are obtained. The results showed that the SF region of KcsA potassium ion channel blocked the passage of Cl- basically, showing a special selection characteristic of the passage of K+; Its current-voltage curve basically presents a linear distribution, and the conductivity-concentration curve presents a trend of first increasing and then flattening. The basic law is consistent with the experimental phenomenon. In addition, the influence of the specific intensity THz field on the channel K+ current is also simulated and analyzed. Compared with the electrostatic field of the same amplitude, the selected 0.6/1.2/5THz terahertz field can reduce the PMF by affecting the interaction potential energy between ion pairs, thereby increasing the K+ current. The research in this paper not only deepens the understanding of the regularity of KcsA potassium ion channels, but also provides a new idea for the study of other types of ion channels and the influence of terahertz field on the characteristics of ion channels.
KcsA (K+ Conduction and Selectivity Architecture)钾离子通道作为活细胞中阳离子活性的调节剂，在神经细胞动作电位的去极化和复极化过程中起着重要作用。本文采用布朗动力学方法系统地模拟了实际KcsA钾通道的电特性。得到了静电场作用下通道内离子的PMF、对称溶液和非对称溶液的电流-电压特性曲线、通道轴向离子浓度分布曲线和电导-浓度曲线。结果表明:KcsA钾离子通道的SF区基本阻断Cl-的通过，对K+的通过表现出特殊的选择特性;其电流-电压曲线基本呈线性分布，电导率-浓度曲线呈先升高后趋于平缓的趋势。该基本定律与实验现象是一致的。此外，还模拟分析了比强太赫兹场对通道K+电流的影响。与相同振幅的静电场相比，选择0.6/1.2/5THz太赫兹场可以通过影响离子对之间的相互作用势能来降低PMF，从而增加K+电流。本文的研究不仅加深了对KcsA钾离子通道的规律性的认识，而且为研究其他类型的离子通道以及太赫兹场对离子通道特性的影响提供了新的思路。
{"title":"Brownian dynamics simulation of electrical properties of KcsA potassium ion channel","authors":"Gao Ming-Zhu, Liu Chun-Liang, Wang Hong-Guang, Li Yong-Dong, Lin Shu, Zhai Yong-Gui","doi":"10.7498/aps.72.20230118","DOIUrl":"https://doi.org/10.7498/aps.72.20230118","url":null,"abstract":"As a regulator of cation activity in living cells, KcsA (K+ Conduction and Selectivity Architecture) potassium channel plays an important role in the depolarization and repolarization of nerve cell action potential. In this paper, Brownian Dynamics (BD) method is used to simulate the electrical characteristics of the actual KcsA potassium channel systematically. The PMF of ions in the channel under electrostatic field, the current-voltage characteristic curve of symmetric solution and asymmetric solution, the ion concentration distribution curve in the axial direction of the channel, and the conduction-concentration curve are obtained. The results showed that the SF region of KcsA potassium ion channel blocked the passage of Cl- basically, showing a special selection characteristic of the passage of K+; Its current-voltage curve basically presents a linear distribution, and the conductivity-concentration curve presents a trend of first increasing and then flattening. The basic law is consistent with the experimental phenomenon. In addition, the influence of the specific intensity THz field on the channel K+ current is also simulated and analyzed. Compared with the electrostatic field of the same amplitude, the selected 0.6/1.2/5THz terahertz field can reduce the PMF by affecting the interaction potential energy between ion pairs, thereby increasing the K+ current. The research in this paper not only deepens the understanding of the regularity of KcsA potassium ion channels, but also provides a new idea for the study of other types of ion channels and the influence of terahertz field on the characteristics of ion channels.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"22 3 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78449710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is shown that discharges with negative triangularity have lower turbulence induced transport and better energy confinement, so the tokamaks with negative triangularity are recognized as a better choice for future fusion devices. In order to explore the features of the energetic particle driven instabilities with negative triangularity, the kinetic- magnetohydrodynamic hybrid code M3D-K has been applied to investigate the linear instability and nonlinear evolution of the fishbone driven by energetic ions with different triangularity. Based on EAST like parameters, it is found that negative triangularity destabilizes the ideal internal kink mode, but stabilizes the fishbone instability. Nonlinear simulations show that the fishbone instability with negative triangularity is hard to saturate without fluid nonlinearity. The possible explanation is that the orbits of fast ions locate more centrally with negative triagularity, so the energy exchange between energetic ions and the fishbone is more efficient than that with positive triangularity. These simulation results demonstrate that considering the fishbone driven by energetic particles, the negative triangularity does not confer a obvious advantage over the positive triangularity.
{"title":"Numerical simulations of fishbones driven by fast ions in negative triangularity tokamak","authors":"Ren Zhen-Zhen, Shen Wei","doi":"10.7498/aps.72.20230650","DOIUrl":"https://doi.org/10.7498/aps.72.20230650","url":null,"abstract":"It is shown that discharges with negative triangularity have lower turbulence induced transport and better energy confinement, so the tokamaks with negative triangularity are recognized as a better choice for future fusion devices. In order to explore the features of the energetic particle driven instabilities with negative triangularity, the kinetic- magnetohydrodynamic hybrid code M3D-K has been applied to investigate the linear instability and nonlinear evolution of the fishbone driven by energetic ions with different triangularity. Based on EAST like parameters, it is found that negative triangularity destabilizes the ideal internal kink mode, but stabilizes the fishbone instability. Nonlinear simulations show that the fishbone instability with negative triangularity is hard to saturate without fluid nonlinearity. The possible explanation is that the orbits of fast ions locate more centrally with negative triagularity, so the energy exchange between energetic ions and the fishbone is more efficient than that with positive triangularity. These simulation results demonstrate that considering the fishbone driven by energetic particles, the negative triangularity does not confer a obvious advantage over the positive triangularity.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"5 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76887094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gao Wei, Yifan Luo, Xing Yu, Ding Peng, Chen Bin-Hui, Han Qing-Yan, Yan Xue-Wen, Zhang Cheng-Yun, Dong Jun
Building core-shell structures have been widely used to enhance and regulate the luminescence properties of rare-earth-doped micro/nano materials. In this work, a variety of different NaErF4 core-shell and core-shell-shell nanocrystals were successfully constructed based on high temperature co-precipitation method by epitaxial growth technology. The upconversion red emission intensity of Er3+ ions in different core-shell structures was effectively enhanced by regulating their structures and doping ions. The experimental structures show that the constructed core-shell nanocrystals are all hexagonal phase structure, and the size of the core-shell structure is about 40 nm. In the near infrared 980 nm laser excitation, the NaErF4 core-shell nanocrystals showed strong single-band red emission. And the single-band red emission intensity of Er3+ ions was enhanced through constructing the NaErF4@NaYbF4:2%Er3+ core-shell structures. The experimental results showed that red emission intensity of Er3+ ions was about 1.4 times higher than that of the NaErF4@NaYbF4 core-shell structures by constructing the NaErF4@NaYbF4:2%Er3+ core-shell structures under 980 nm excitation, and the red/green emission intensity ratio was increased from 5.4 to 6.5. Meanwhile, when NaErF4@NaYbF4:2%Er3+ core-shell structures have recoated the NaYF4 inert shell and introduced trace amounts of Tm3+ ions, the red emission intensity of Er3+ ions was 23.2 and 40.3 times compared with NaErF4@NaYbF4 core-shell structures, and the red/green emission intensity ratio reached 7.5 and 10.2, respectively. The red emssion enhancement of Er3+ ions was mainly caused by bidirectional energy transfer processes of high excitation energy of Yb3+ ions and energy trapping center of Tm3+ ions which effectively changed the densities of population of luminescent energy levels of Er3+ ions. What’s more, the coated NaYF4 inert shell also effectively reduced the surface quenching effect of nanocrystals. The mechanism of red enhancement in different core-shell structures were discussed based on the spectral properties, the processes of interion energy transfer and luminescence kinetics. The constructed NaErF4@NaYbF4:2%Er3+@NaYF4 core-shell structures with high-efficiency red emission in this work has great application potential in the fields of colorful anti-counterfeiting, display and biological imaging.
{"title":"Enhancing red upconversion emission of Er3+ by building NaErF4@NaYbF4:2%Er3+ core-shell structure","authors":"Gao Wei, Yifan Luo, Xing Yu, Ding Peng, Chen Bin-Hui, Han Qing-Yan, Yan Xue-Wen, Zhang Cheng-Yun, Dong Jun","doi":"10.7498/aps.72.20230762","DOIUrl":"https://doi.org/10.7498/aps.72.20230762","url":null,"abstract":"Building core-shell structures have been widely used to enhance and regulate the luminescence properties of rare-earth-doped micro/nano materials. In this work, a variety of different NaErF<sub>4</sub> core-shell and core-shell-shell nanocrystals were successfully constructed based on high temperature co-precipitation method by epitaxial growth technology. The upconversion red emission intensity of Er<sup>3+</sup> ions in different core-shell structures was effectively enhanced by regulating their structures and doping ions. The experimental structures show that the constructed core-shell nanocrystals are all hexagonal phase structure, and the size of the core-shell structure is about 40 nm. In the near infrared 980 nm laser excitation, the NaErF<sub>4</sub> core-shell nanocrystals showed strong single-band red emission. And the single-band red emission intensity of Er<sup>3+</sup> ions was enhanced through constructing the NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup> core-shell structures. The experimental results showed that red emission intensity of Er<sup>3+</sup> ions was about 1.4 times higher than that of the NaErF<sub>4</sub>@NaYbF<sub>4</sub> core-shell structures by constructing the NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup> core-shell structures under 980 nm excitation, and the red/green emission intensity ratio was increased from 5.4 to 6.5. Meanwhile, when NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup> core-shell structures have recoated the NaYF<sub>4</sub> inert shell and introduced trace amounts of Tm<sup>3+</sup> ions, the red emission intensity of Er<sup>3+</sup> ions was 23.2 and 40.3 times compared with NaErF<sub>4</sub>@NaYbF<sub>4</sub> core-shell structures, and the red/green emission intensity ratio reached 7.5 and 10.2, respectively. The red emssion enhancement of Er<sup>3+</sup> ions was mainly caused by bidirectional energy transfer processes of high excitation energy of Yb<sup>3+</sup> ions and energy trapping center of Tm<sup>3+</sup> ions which effectively changed the densities of population of luminescent energy levels of Er<sup>3+</sup> ions. What’s more, the coated NaYF<sub>4</sub> inert shell also effectively reduced the surface quenching effect of nanocrystals. The mechanism of red enhancement in different core-shell structures were discussed based on the spectral properties, the processes of interion energy transfer and luminescence kinetics. The constructed NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup>@NaYF<sub>4</sub> core-shell structures with high-efficiency red emission in this work has great application potential in the fields of colorful anti-counterfeiting, display and biological imaging.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"56 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76909564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Huang Zhi-Qiu, Zhang Meng, Peng Zhi-Min, Wang Zhen, Yang Qian-suo
Using numerical simulation and a constructed cavity ring-down spectroscopy device, the influence of the finite coherence of the injected laser on the coupling process between the injected light and the cavity longitudinal mode was studied. The finite coherence of the injected light leads to the randomness of the coupling pulse during frequency scanning. The randomness is mainly reflected in two aspects: Firstly, as the coherence length decreases, the random amplitude range of the coupling pulse increases. Secondly, as the coherence of the injected light deteriorates, the coupling pulse changes from a single pulse with intensity evolution to continuous multiple pulses, and the overall width gradually increases with the decrease of the scanning rate. Moreover, with the deterioration of the coherence, when the light intensity of the cavity is used to turn off the injected light, the decrease in the scanning rate can cause more than one injection shut-off and ring-down event in a frequency coupling process, especially when scanning with the length of the cavity. In addition, a theoretical method is proposed to estimate the ring-down time using the strength integral of different time intervals, and the relevant experimental verification is carried out. The experimental results show that the relative error of the ring-down time obtained by the intensity integration method is smaller than that obtained by the traditional fitting method.
{"title":"The influence of the finite coherence of injected light on the ring-down cavity measurement method and the intensity integral method for the ring-down time determination","authors":"Huang Zhi-Qiu, Zhang Meng, Peng Zhi-Min, Wang Zhen, Yang Qian-suo","doi":"10.7498/aps.72.20230448","DOIUrl":"https://doi.org/10.7498/aps.72.20230448","url":null,"abstract":"Using numerical simulation and a constructed cavity ring-down spectroscopy device, the influence of the finite coherence of the injected laser on the coupling process between the injected light and the cavity longitudinal mode was studied. The finite coherence of the injected light leads to the randomness of the coupling pulse during frequency scanning. The randomness is mainly reflected in two aspects: Firstly, as the coherence length decreases, the random amplitude range of the coupling pulse increases. Secondly, as the coherence of the injected light deteriorates, the coupling pulse changes from a single pulse with intensity evolution to continuous multiple pulses, and the overall width gradually increases with the decrease of the scanning rate. Moreover, with the deterioration of the coherence, when the light intensity of the cavity is used to turn off the injected light, the decrease in the scanning rate can cause more than one injection shut-off and ring-down event in a frequency coupling process, especially when scanning with the length of the cavity. In addition, a theoretical method is proposed to estimate the ring-down time using the strength integral of different time intervals, and the relevant experimental verification is carried out. The experimental results show that the relative error of the ring-down time obtained by the intensity integration method is smaller than that obtained by the traditional fitting method.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"21 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77210397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nong Jie, Zhang Yi-Yi, Wei Xue-Ling, Jiang Xin-Peng, Li Ning, Wang Dong-Ying, Xiao Si-Yang, Chen Hong-Ting, Zhang Zhen-Rong, Yang Jun-Bo
The "cat's eye effect" in the optical window of all kinds of photoelectric equipment is the main basis of a laser active detection system, which poses a great threat to military equipment and combatants. However, under the condition of ensuring high visible transmittance, the sniper stealth scheme for anti-laser active detection remains to be discussed. In this paper, genetic algorithm was used to reverse design the metasurface anti-reflection film. Si3N4 and Ag were composed of three-layer anti-reflection film, and rectangular array of metal micro-nano structures were added on the top layer to form a wavelength selective absorber, so as to achieve the effect of low reflection and high absorption at laser wavelength. By combining the device design with genetic algorithm, the parameter combination that best meets the target performance of the device is obtained. The average transmittance at 380nm~780nm is 88% meanwhile the maximum transmittance peak of 94%. The reflectance at 1550nm of 10%, and the absorption rate of 80% are achieved. In order to better meet the requirements of practical application, we further designed the cross metal array to obtain polarization insensitive characteristics. The metasurface anti-reflective membrane with improved structure can achieve an average visible transmittance of 82% and a reflectance of 5% at 1550nm. The two metasurface anti-reflection film designed in this paper does not require additional devices, and the imaging quality can be guaranteed. At the same time, it can effectively reduce the laser echo energy, so as to achieve the effect of high quality visible light transmittance and laser stealth compatibility.
{"title":"Research on Dielectric/Metal/Dielectric film system for high transmittance compatible laser stealth","authors":"Nong Jie, Zhang Yi-Yi, Wei Xue-Ling, Jiang Xin-Peng, Li Ning, Wang Dong-Ying, Xiao Si-Yang, Chen Hong-Ting, Zhang Zhen-Rong, Yang Jun-Bo","doi":"10.7498/aps.72.20230855","DOIUrl":"https://doi.org/10.7498/aps.72.20230855","url":null,"abstract":"The \"cat's eye effect\" in the optical window of all kinds of photoelectric equipment is the main basis of a laser active detection system, which poses a great threat to military equipment and combatants. However, under the condition of ensuring high visible transmittance, the sniper stealth scheme for anti-laser active detection remains to be discussed. In this paper, genetic algorithm was used to reverse design the metasurface anti-reflection film. Si3N4 and Ag were composed of three-layer anti-reflection film, and rectangular array of metal micro-nano structures were added on the top layer to form a wavelength selective absorber, so as to achieve the effect of low reflection and high absorption at laser wavelength. By combining the device design with genetic algorithm, the parameter combination that best meets the target performance of the device is obtained. The average transmittance at 380nm~780nm is 88% meanwhile the maximum transmittance peak of 94%. The reflectance at 1550nm of 10%, and the absorption rate of 80% are achieved. In order to better meet the requirements of practical application, we further designed the cross metal array to obtain polarization insensitive characteristics. The metasurface anti-reflective membrane with improved structure can achieve an average visible transmittance of 82% and a reflectance of 5% at 1550nm. The two metasurface anti-reflection film designed in this paper does not require additional devices, and the imaging quality can be guaranteed. At the same time, it can effectively reduce the laser echo energy, so as to achieve the effect of high quality visible light transmittance and laser stealth compatibility.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"580 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76259113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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