Incoherent subharmonic light scattering in isotropic media

Incoherent subharmonic light scattering in isotropic media is a new kind of nonlinear light scattering, which involves single input photon and multiple output photons of equal frequency. We investigate theoretically the dependence of the subharmonic scattering intensity on the hyperpolarizability of molecules and the incident intensity using nonlinear optics theory similar to that used for Hyper-Rayleigh scattering and degenerate optical parametric oscillators. It is derived that the subharmonic scattering intensities grow exponentially or superexponentially with the hyperpolarizability of molecules and the incident intensity. (C) 2004 Elsevier B.V. All rights reserved.

Distributed Temperature Sensing System Based on Rayleigh Scattering BOTDA

A distributed temperature sensor based on Rayleigh scattering Brillouin optical time domain analysis (Rayleigh-BOTDA) is proposed in this paper. The sensor uses Rayleigh backscattering effect of microwave modulated pulse base sidebands as probe wave and a high sensitive photon counting detector for Brillouin signal intensity detection. Compared with a conventional BOTDA system, the Rayleigh-BOTDA effectively suppresses polarization-induced signal fluctuation resulting in improved signal intensity. The experimental scheme presented is simplified by using a single laser with one-end access. The temperature accuracy of the new sensing system was demonstrated as 1 degrees C on spatial resolution of 3 m.

Enhanced resonance light scattering based on biocatalytic growth of gold nanoparticles for biosensors design

The biocatalytic growth of gold nanoparticles (Au-NPs) has been employed in the design of new optical biosensors based on the enhanced resonance light scattering (RLS) signals. Both absorption spectroscopy and transmission electron microscopy (TEM) analysis revealed Au-NP seeds could be effectively enlarged upon the reaction with H2O2, an important metabolite that could be generated by many biocatalytic reactions.

圆弧形沉积场地对平面瑞利波散射的解析分析

分别采用Biot饱和多孔介质动力学理论和单相介质弹性动力学理论模拟层状沉积谷场地和周围场地,利用波函数展开法,得出了层状饱和沉积场地对Rayleigh波散射的解析解.进行参量分析,研究了无量纲入射波频率、层状沉积层排列顺序及相对刚度和厚度等因素对Rayleigh波散射效应的影响

Study on the interaction of intense femtosecond laser pulses with nanometre-sized hydrogen clusters

The interaction of intense femtosecond laser pulses with hydrogen clusters has been experimentally studied. The hydrogen clusters were produced from expansion of high-pressure hydrogen gas (backed up to 8x10(6)Pa) into vacuum through a conical nozzle cryogenically cooled by liquid nitrogen. The average size of hydrogen clusters was estimated by Rayleigh scattering measurement and the maximum proton energy of up to 4.2keV has been obtained from the Coulomb explosion of hydrogen clusters under 2 x 10(16)W/cm(2) laser irradiation. Dependence of the maximum proton energy on cluster size and laser intensity was investigated, indicating the correlation between the laser intensity and the cluster size. The maximum proton energy is found to be directly proportional to the laser intensity, which is consistent with the theoretical prediction.

Effects on the proton production from explosions of hydrogen clusters subjected to intense femtosecond laser fields

The dependence of the maximum and average energies of protons, which were produced in the interaction of an intense laser pulse (similar to 1 x 10(16) W cm(-2), 65 fs) with hydrogen clusters in a gas jet backed up to 80 bar at liquid nitrogen temperature (similar to 80 K), on the backing pressure has been studied. The general trend of the proton energy dependence on the square of the average cluster radius, which is determined by a calibrated Rayleigh scattering measurement, is similar to that described by theory under the single size approximation. Calculations are made to fit the experimental results under a simplified model by taking into account both a log-normal cluster size distribution and the laser intensity attenuation in the interaction volume. A very good agreement between the experimental proton energy spectra and the calculations is obtained in the high- energy part of the proton energy distributions, but a discrepancy of the fits is revealed in the low-energy part at higher backing pressures which are associated with denser flows. A possible mechanism which would be responsible for this discrepancy is discussed. Finally, from the fits, a variation of the cluster size distributions was revealed to be dependent on the gas backing pressure as well as on the evolving time of the gas flow of clusters.

Crystallization Kinetics of Syndiotactic Polypropylene Studied by Time-Dependent Light Attenuation

Crystallization kinetics of syndiotactic polypropylene ( sPP) was observed by light attenuation measurements. The initial stages of temperature dependent sPP crystallization fall in the range of Rayleigh scattering and Rayleigh-Debye-Gans scattering. Initial time and growth time of crystallization were obtained, and the trend of crystallization temperature dependent linear attenuation coefficient on the radius and the index of the refraction of the spherulite were evaluated.

Small-molecule-directed assembly: A gold nanoparticle-based strategy for screening of homo-adenine DNA duplex binders

By using AuNP-modified homo-adenine DNA conjugate as a model system, simple colorimetric and resonance Rayleigh scattering assays have been developed for screening small molecules that trigger the formation of the non-Watson-Crick homo-adenine duplexes. The assay presented here is more simplified in format as it involves only one type of ssDNA modified Au-NP, and can be easily adapted to high-throughput screening.

Monte Carlo Simulation Of Thermal Fluctuations Below The Onset Of Rayleigh-Benard Convection

The density fluctuations below the onset of convection in the Rayleigh-Benard problem are studied with the direct simulation Monte Carlo method. The particle simulation results clearly show the connection between the static correlation functions of fluctuations below the critical Rayleigh number and the flow patterns above the onset of convection for small Knudsen number flows (Kn=0.01 and Kn=0.005). Furthermore, the physical nature for no convection in the Rayleigh-Benard problem under large Knudsen number conditions (Kn>0.028) is explained based on the dynamics of fluctuations.

NEW METHOD FOR ACQUIRING A HIGH-RESOLUTION ATMOSPHERIC RAYLEIGH-MIE SPECTRUM

A new method using an atomic-resonance filter and deconvolution techniques has been developed to acquire high-resolution spectra of atmospheric Rayleigh-Mie scattering. In the deconvolution process, the difficulty of the undetermined division 0/0 is overcome by a fitting method. Preliminary laboratory experimental results on 90-deg scattering show that with a signal-to-noise ratio of 20, the scattered Rayleigh-Mie spectrum may be retrieved in agreement with the theoretical analysis.

Large-Eddy-Simulation of 3-Dimensional Rayleigh-Taylor Instability in Incompressible Fluids

The 3-dimensiqnal incompressible Rayleigh-Taylor instability is numerically studied through the large-eddy-simulation (LES) approach based on the passive scalar transport model. Both the instantaneous velocity and the passive scalar fields excited by sinu

Instability of Two-Layer Rayleigh-Benard Convection with Interfacial Thermocapillary Effect

The linear instability analysis of the Rayleigh-Allarangoni-Benard convection in a two-layer system of silicon oil 10cS and fluorinert FC70 liquids are performed in a larger range of two-layer depth ratios H, from 0.2 to 5.0 for different total depth H less than or equal to 12 mm. Our results are different from the previous study on the Rayleigh-Benard instability and show strong effects of thermocapillary force at the interface on the time-dependent oscillations arising from the onset of instability convection.

Oscillatory instability of Rayleigh-Marangoni-Bénard convection in two-layer liquid systems

The oscillatory behaviour of the Rayleigh-Marangoni-Bénard convective instability (R-M-B instability) regarding two combinations of two-layer fluid systems has been investigated theoretically and numerically. For the two-layer system of Silicone oil (10cSt) over Fluorinert (FC70), both linear instability analysis and 2D numerical simulation show that the instability of the system depends strongly on the depth ratio Hr = H1/H2 of the two-layer liquid. The oscillatory regime at the onset of R-M-B convection enlarges with reducing Γ = Ra/Ma values. In the two-layer system of Silicone oil (2cSt) over water, it loses its stability and onsets to steady convection at first, then the steady convection bifurcates to oscillatory convection with increasing Rayleigh number Ra. This behaviour was found through numerical simulation above the onset of steady convection in the case of r = 2.9, ε=(Ra-Ruc)/Rac = 1.0, and Hr = 0.5. Our findings are different from the previous study of the Rayleigh-Benard instability and show the strong effects of the thermocapillary force at the interface on the time-dependent oscillations at or after the onset of convection. We propose a secondary oscillatory instability mechanism to explain the experimental observation of Degen et al. [Phys. Rev. E, 57 (1998), 6647-6659].

Rayleigh-Taylor Instability of a Liquid Drop at High Bond Numbers

给出了高Bond数下黏性液滴表面Rayleigh-Taylor线性不稳定性的分析解,这种不稳定性对于超音速气流作用下液滴破碎的早期阶段起着至关重要的作用.基于稳定性分析的结果,导出了用于估算稳定液滴的最大直径及液滴无量纲初始破碎时间的计算式,这些计算式与相关文献给出的实验和分析结果比较显示了良好的一致.

The scattering of general SH plane wave by interface crack between two dissimilar viscoelastic bodies

The scattering of general SH plane wave by an interface crack between two dissimilar viscoelastic bodies is studied and the dynamic stress,intensity factor at the crack-tip is computed. The scattering problem can be decomposed into two problems: one is the reflection and refraction problem of general SH plane waves at perfect interface (with no crack); another is the scattering problem due to the existence of crack. For the first problem, the viscoelastic wave equation, displacement and stress continuity conditions across the interface are used to obtain the shear stress distribution at the interface. For the second problem, the integral transformation method is used to reduce the scattering problem into dual integral equations. Then, the dual integral equations are transformed into the Cauchy singular integral equation of first kind by introduction of the crack dislocation density function. Finally, the singular integral equation is solved by Kurtz's piecewise continuous function method. As a consequence, the crack opening displacement and dynamic stress intensity factor are obtained. At the end of the paper, a numerical example is given. The effects of incident angle, incident frequency and viscoelastic material parameters are analyzed. It is found that there is a frequency region for viscoelastic material within which the viscoelastic effects cannot be ignored.