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Carbon nitrides are excellent candidates for extreme hardness materials. In this work, a new I4̅3m phase of C3N2 has been uncovered by replacing part of the nitrogen atoms in the cagelike diamondoid nitrogen N10 with carbon atoms. This phase is mechanically and dynamically stable up to at least 50 GPa. The elastic anisotropy of I4̅3m-C3N2 is investigated by comparing with previously proposed α-C3N2. The tensile directional dependence of Young's modulus obeys the following trend: E[111]> E[110]> E[100]. Electronic structure calculations reveal that I4̅3m-C3N2 is hole conducting. Hardness calculation shows that the I4̅3m-C3N2 is superhard with a hardness of 72.9 GPa. [ABSTRACT FROM AUTHOR]

Debye series expansion is employed to the analysis of radiation pressure force exerted on a spherical particle induced by an axicon-generated Bessel beam. The beam shape coefficients for Bessel beams are calculated using analytical expressions obtained by the integral localized approximation, and the scattering coefficients are expanded using Debye series. The effect of different parameters (beam center location, radius of particle, half-cone angle, etc.) on radiation pressure force is studied. The contributions of different scattering processes on radiation pressure force are isolated for better understanding of physical mechanism of various features of radiation pressure force. [ABSTRACT FROM PUBLISHER]

Based on Lighthill acoustic analogy theory and combining boundary element method ( BEM) with computational fluid dynamics ( CFD), the pulsating pressure data of flow field boundary are input into the BEM model for a passenger car, and the boundary conditions of aerodynamic dipole sound source near car surface are obtained through conversion and calculation. A numerical simulation on the external radiation sound field of vehicle aerodynamic noise is conducted by using direct BEM. The results show that the intensity of dipole sound source on car surface decreases with the increase of frequency, the sound pressure level of aerodynamic noise near rearview mirrors is up to some 78 dB at 2,000Hz with a vehicle speed of 120km/h, and at the same frequency, the radiation intensity of aerodynamic sound source on the longitudinal symmetric plane of vehicle is larger than that on horizontal plane. [ABSTRACT FROM AUTHOR]

Abstract: An efficient numerical procedure for computing the scattering coefficients of a radially stratified tilted cylinder is discussed. Compared with the previous algorithms, computations for scattering field in our code are extended to fairly large parameters, up to more than 10,000 and a few millions in the number of layers, and computational time is only a few seconds. The capabilities of our code depend also on the memory of the computer. The algorithm can also be used for absorbing or nonabsorbing cylinders in different electromagnetic wave bands. Compared with the known results, the algorithm is validated. At last, the algorithm is used to simulate the intensity distributions of two-layered cylinders with large size parameter and of graded-index polymer optical fiber (GI-POF) at tilted incidence, which supplies information on non-intrusive measurement on-line of refractive index profile by light scattering. [Copyright &y& Elsevier]

The potential applications of complex optical fields for environmental detection have attracted a lot of attention. In this study, dusty medium is equivalent to a uniformly charged sphere and a non-uniform concentric layered sphere that satisfying the single scattering condition, respectively. The interaction between a high-order polarized Bessel Gaussian beam and a spherical particle is investigated using the generalized Lorenz–Mie theory and the angular spectrum decomposition method. The location of incident beam is considered for the first time. The extinction efficiency results of a wet charged particle are compared with those of a wet neutral particle. Simulations show that the difference in extinction between these two kinds of particles mentioned above is more evident in the smaller size parameter range, which is similar to the case of plane wave incidence. In addition, the influence of complex refractive index and size proportion of heterogeneous medium on the extinction effect is analyzed. The characteristic parameters of the incident beam are considered and find out that how they affect the differences in extinction is independent of the illuminated particle. This study lays the foundation for analyzing the transmission capacity of a Bessel Gaussian vortex beam with various parameters in a dust particle cluster. • The attenuation characteristics of a high-order polarized Bessel Gaussian beam by a uniformly charged sphere and a non-uniformly concentric sphere are studied for the first time. • The influence of the position of the incident beam on the attenuation effect is discussed. • The difference in extinction between charged and neutral particles is more evident in the smaller size parameter range, which is similar to the case of plane wave incidence. [ABSTRACT FROM AUTHOR]

• Beam shape coefficients of high-order vector Bessel-Gaussian beams are derived. • Incident beam and scatterer parameters can highly influence the scattering results. • It is not feasible to recognize the relative humidity of aerosol environment by using the differences of scattering intensities. Based on the generalized Lorenz-Mie theory (GLMT) and the angular spectrum decomposition method (ASDM), we derive the beam shape coefficients (BSCs) of high-order vector Bessel Gaussian beams (H-VBGB), and investigate the interaction mechanism of H-VBGB illuminating a spherical marine aerosol. Linear (x, y), circular (left, right), azimuthal and radial polarizations are considered. The effects of various parameters characterizing the incident beam and the aerosol on the normalized differential scattering cross section (DSCS) are investigated. Numerical results show that the normalized DSCS is very sensitive to fluctuations in the parameters, and that the distinctions of incident beams may highly influence results. The relative humidity of aerosol performs similar effects on results for all polarizations, so it is not feasible to recognize the relative humidity of aerosol environment by using the differences of normalized DSCS for various polarization states. We provide a reference for the practical use of the scattering features of non-diffractive beams illuminating spherical calibrators. [ABSTRACT FROM AUTHOR]

• The internal and near-surface fields for a charged sphere by a vector Bessel beam is investigated in the framework of GLMT. • The effects of the surface charge, polarization, order, and half-cone angle are discussed. • The local enhancements of internal and near-surface fields are analyzed. The interaction of an axicon-generated vector Bessel beam (AGVBB) with a charged sphere is investigated in the framework of generalized Lorenz–Mie theory (GLMT). The incident, internal, and scattered fields are expanded using vector spherical wave functions (VSWFs), beam shape coefficients (BSCs), and internal and scattered coefficients. An analytical expressions of beam shape coefficients (BSCs), which are derived using angular spectrum decomposition method (ASDM), are given. The internal and scattered coefficients are derived by considering the boundary conditions. The internal and near-surface electric fields of a charged sphere illuminated by AVGBBs are numerical calculated, and the effects of polarization, order of beam, half-cone angle are mainly discussed. The results are compared with that for neutral particles. The effect of the surface charge are discussed by the comparison of the results for charged spheres with that for neutral particles. Numerical results show that the internal and near-surface fields are sensitive to the surface charge. The internal fields and the near-surface fields can be locally enhanced. Internal and near-surface fields, especially its local enhancement, are very sensitive to the beam parameters, including polarization, order, half-cone angle, etc. [ABSTRACT FROM AUTHOR]

The remarkable properties of magnetic nanostructures have sparked considerable interest within the biomedical domain, owing to their potential for diverse applications. In targeted drug delivery systems, therapeutic molecules can be loaded onto magnetic nanocarriers and precisely guided and released within the body with the assistance of an externally applied magnetic field. However, conventional external magnetic fields generated by permanent magnets or electromagnets are limited by finite magnetic field gradients, shallow penetration depths, and low precision. The novel structured light field known as the Airy light-sheet possesses unique characteristics such as non-diffraction, self-healing, and self-acceleration, which can potentially overcome the limitations of traditional magnetic fields to some extent. While existing studies have primarily focused on the manipulation of dielectric particles by Airy light-sheet, comprehensive analyses exploring the intricate interplay between Airy light-sheet and magnetic nanostructures are currently lacking in the literature, with only preliminary theoretical discussions available. This study systematically explores the mechanical response of magnetic spherical particles under the influence of Airy light-sheet, including radiation forces and spin torques. Furthermore, we provide an in-depth analysis of the effects of particle size, permittivity, permeability, and incident light-sheet parameters on the mechanical effects. Our research findings not only offer new theoretical guidance and practical references for the application of magnetic nanoparticles in biomedicine but also provide valuable insights for the manipulation of other types of micro/nanoparticles using structured light fields.

Electromagnetic scattering is a routine tool for rapid, non-contact characterization of particle media. In previous work, the interaction targets of scattering intensity, scattering efficiency, and extinction efficiency of Bessel pincer light-sheet beams were all aimed at dielectric spheres. However, most particles in nature are charged. Considering the boundary condition on a charged sphere, the beam shape coefficients (BSCs) (pmn,qmn) of the charged spherical particle illuminated by a Bessel pincer light-sheet beam are obtained. The extinction, scattering, and absorption efficiencies are derived under the generalized Lorenz-Mie theory (GLMT) framework. This study reveals the significant differences in scattering characteristics of Bessel pincer light-sheet beams on a charged particle compared to traditional beams. The simulations show a few apparent differences in the far-field scattering intensity and efficiencies between charged and natural spheres under the influence of dimensionless size parameters. As dimensionless parameters increase, the difference between the charged and neutral spheres decreases. The effects of refractive index and beam parameters on scattering, extinction, and absorption coefficients are different but tend to converge with increasing dimensionless parameters. When applied to charged spheres with different refractive indices, the scattering, extinction, and absorption efficiencies of Bessel pincer light-sheet beams change with variations in surface charge. However, once the surface charge reaches saturation, these efficiencies become stable. This study is significant for understanding optical manipulation and super-resolution imaging in single-molecule microbiology.