Dynamical Casimir effect in superradiant light scattering by Bose Einstein condensate in an optomechanical cavity

We investigate the effects of dynamical Casimir effect in superradiant light scattering by Bose-Einstein condensate in an optomechanical cavity. The system is studied using both classical and quantized mirror motions. The cavity frequency is harmonically modulated in time for both the cases. The main quantity of interest is the number of intracavity scattered photons. The system has been investigated under the weak and strong modulations. It has been observed that the amplitude of the scattered photons is more for the classical mirror motion than the quantized mirror motion. Also, initially, the amplitude of scattered photons is high for lower modulation amplitude than higher modulation amplitude. We also found that the behavior of the plots are similar under strong and weak modulations for the quantized mirror motion.

In situ nanobubble sizing by visualization particle tracking and image-based dynamic light scattering

A novel method combining visualization particle tracking with image-based dynamic light scattering was developed to achieve the in situ and real-time size measurement of nanobubbles(NBs).First,the in situ size distribution of NBs was visualized by dark-field microscopy.Then,real-time size during the preparation was measured using image-based dynamic light scattering,and the longitudinal size distribution of NBs in the sample cell was obtained in a steady state.Results show that this strategy can provide a detailed and accurate size of bubbles in the whole sample compared with the commercial ZetaSizer Nano equipment.Therefore,the developed method is a real-time and simple technology with excellent accuracy,providing new insights into the accurate measurement of the size distribution of NBs or nanoparticles in solution.

Dynamic Behavior and Mass Transport in Polyacrylic Acid Gel by Dynamic Light Scattering

Dynamic behaviors on polyacrylic acid (PAA) gels and mass (small molecules) transports in the gels have been studied mainly by dynamic light scattering (DLS). The cross-linking degree (fc), monomer concentration (Cm) and temperature of the gels have significant influences on its dynamic behavior and mass transport in the gels. The increase of fc leads to decrease of the mesh sizes of the gels, thus the obstacle of the gels for mass transport is increased. As a result, small molecular diffusion Dk in the gels is decreased. So even if for small molecules, the Dk also is influenced.

DYNAMIC LIGHT SCATTERING STUDY ON TRANSLATION DIFFUSION OF 8-ARM STAR POLYSTYRENE IN GOOD AND THETA SOLVENTS

The technique of dynamic light scattering has been used to investigate the translation diffusion behavior of 8-arm star polystyrene (SPS)in a good solvent, tetrahydrofuran (THF) or benzene (BZ) and a theta solvent, cyclohexane (CH), by homodyne photon correlation spectroscopy .The intensityintensity autocorrelation function was analyzed by the method of cumulant. The translation diffusion coefficients have been obtained as a function of temperature and concentration. Under theta condition ,the non-concentration dependence of diffusion coefficient showed the unperturbed Gaussian state o the SPS molecular chain. The different hydrodynamic radii estimated from Stokes- Einstein equation reflected the stretch extent of the arm chain for regular star polymer. The data of diffusion activation energy of SPS in THF, BZ and CH were also obtained respectively.

EARLY CATARACT DETECTION BY DYNAMIC LIGHT SCATTERING WITH SPARSE BAYESIAN LEARNING

Dynamic light scattering(DLS)is a promising technique for early cataract detection and for studying cataractogenesis.A novel probabilistic analysis tool,the sparse Bayesian learning(SBL)algorithm,is described for reconstructing the most-probable size distribution ofα-crystallin and their aggregates in an ocular lens from the DLS data.The performance of the algorithm is evaluated by analyzing simulated correlation data from known distributions and DLS data from the ocular lenses of a fetal calf,a Rhesus monkey,and a man,so as to establish the required efficiency of the SBL algorithm for clinical studies.

Applying dynamic light scattering to investigate the self-assembly process of DNA nanostructures

Understanding the dynamic assembly process of DNA nanostructures is important for developing novel strategy to design and construct functional devices.In this work,temperature-controlled dynamic light scattering(DLS)strategy has been applied to study the global assembly process of DNA origami and DNA bricks.Through the temperature dependent size and intensity profiles,the self-assembly process of various DNA nanostructures with different morphologies have been well-studied and the temperature transition ranges could be observed.Taking advantage of the DLS information,rapid preparation of the DNA origami and the brick assembly has been realized through a constant temperature annealing.Our results demonstrate that the DLS-based strategy provides a convenient and robust tool to study the dynamic process of forming hieratical DNA structures,which will benefit understanding the mechanism of self-assembly of DNA nanostructures.

Polarized imaging dynamic light scattering for simultaneous measurement of nanoparticle size and morphology

The performance of nanoparticles is often affected by particle size and morphology.Currently,electron microscopy or atomic force microscopy is typically utilized to determine the size and morphology of nanoparticles.However,there are issues such as difficult sample preparation,long processing times,and challenges in quantitative characterization.Therefore,it is of great significance to develop a fast,accu-rate,and statistical method to measure the size and morphology of nanoparticles.In this study,a new method,called polarized imaging dynamic light scattering(PIDLS),is proposed.The nanoparticles are irradiated with a vertical linearly polarized laser beam,and a polarization camera collected the dynamic light scattering images of particles at four different polarization directions(0°,45°,90°,and 135°)at a scattering angle of 90°.The average particle size and distribution are obtained using the imaging dy-namic light scattering method at 0°polarization direction,and the morphology of the particles is ob-tained based on the depolarization patterns of the scattered light.The optical sphericityΦis defined based on the degree of linear polarization(DoLP).It is also implemented for the quantitative evaluation of the sphericity of the nanoparticles,including spherical,octahedral,nanoplate,nanorod,and linear ones.Together with the Poincarésphere parameterψ,the morphology of the nanoparticles can be roughly identified.In addition,PIDLS enables the measurement of particle size and morphology distributions simultaneously for evaluating the uniformity of particles.The effectiveness of PIDLS is verified by the measurement of five kinds of industrial titanium dioxide as well.

A regularization algorithm of dynamic light scattering for estimating the particle size distribution of dual-substance mixture in water

Dynamic light scattering(DLS)is a nondestructive,well-established technique for the size characterization of proteins,nanoparticles,polymers,and colloidal dispersions.However,current DLS techniques are only applied to particle groups of single composition due to the limitation of their inversion algorithm.In this study,we propose a particle size distribution inversion algorithm based on the Tikhnonov regularization method that can be applied to the dual-substance particle mixture.The algorithm retrieves the particle size distributions of two substances,respectively,by taking advantage of their refractive index differences.The simulation results reveal that the algorithm has excellent accuracy and stability when the scattering angle is 30°.Instead of the original identity matrix,the first-order difference matrix and second-order difference matrix are used as the regular matrix when utilizing the Tikhnonov algorithm,which obviously improves the anti-interference,accuracy,and stability of the algorithm.Furthermore,the inversion of particle size distribution is carried out at a 0.01%–1%noise level,which shows that the algorithm has an available antinoise ability.Finally,experimental particle size measurements for a mixture of polystyrene beads and toner particles demonstrate that the proposed algorithm is superior to the traditional Tikhnonov algorithm in applicability and accuracy.

Study of asphaltene reaggregation in toluene/heptane mixture by dynamic and static light scattering

This paper presents the study of the effect of multiple ultrasonic impacts on submicron asphaltene aggregates in a toluene/heptane solution,conducted with dynamic light scattering technique.The objects of the study were four samples of asphaltenes obtained from four different oils.For all samples,the change in the average size of the asphaltene submicron aggregates with time was measured after the addition of a precipitant(heptane)to a solution of asphaltenes in toluene at an amount above the threshold concentration.Asphaltene aggregates formed in solution after the addition of the precipitant and were subjected to ultrasonic treatment,which led to the destruction of the asphaltene aggregates.Aggregation of destroyed asphaltenes was observed.The kinetics of this aggregation were similar to the kinetics of aggregation of asphaltenes after the addition of a precipitant.Multiple iterations of asphaltene aggregate destruction in the sample led to a significant change in the kinetics of aggregation:the growth of aggregates slowed and stabilized at a size of approximately 200 nm and 30 nm for the different studied samples.

用于微量生物样本检测的显微动态光散射系统研制

针对微量生物样品的粒径检测需求,提出了一种显微动态光散射测量系统。传统的动态光散射技术在微量生物样品检测中通常需要毫升级别的样品,这种大量样品消耗不适用于微量生物样品的检测。为解决这一问题,设计了一套融合普通显微镜和动态光散射技术的显微动态光散射系统。通过整合这两种技术,文章成功将测量样品的用量降低到几十微升的水平,实现了两个数量级的提升,从而显著减少了样品的消耗,满足了实验室对微量生物样品检测的需求。为验证该系统的可行性,对不同材质和尺寸的纳米颗粒以及生物外泌体样本进行了评估。实验结果显示,针对60nm的聚苯乙烯微球颗粒和208.6nm的外泌体颗粒的测量尺寸误差分别为1.5%和-3.4%,与实际尺寸吻合良好,证明了该系统在实际应用中的可行性。

动态光散射测量仪粒度标准物质的研制

【目的】解决国内尚缺动态光散射测量法专用粒度标准物质的问题。【方法】采用微乳液聚合法合成标称粒径为40、80 nm的态光散射粒度标准物质,标准物质编号分别是QBW12001和GBW12011b;采用动态光散射多家定值法测定2种粒度标准物质的散射光强调和平均粒径,定值结果溯源至动态光散射法(ISO 22412:2017)。【结果】合成的2种粒度标准物质均匀且稳定,散射光强调和平均粒径分别为(40.0±0.5)、(80±2)nm。【结论】不同厂家生产的激光粒度仪测的散射光强度调和平均粒径一致性最好;散射光强度平均粒径一致性较好;体积平均粒径一致性较差;颗粒数目平均粒径一致性最差。

基于偏振图像动态光散射的非球形纳米颗粒测量

纳米材料的功能特性与其粒度和形貌有很大关系。图像动态光散射法是一种快速、准确、非接触的纳米颗粒测量方法。将图像动态光散射与偏振散射结合,提出了一种测量非球形纳米颗粒形貌的方法。根据偏振散射理论,当入射光为垂直线偏振光,颗粒的散射光在不同偏振方向的偏振散射特性与颗粒的形貌有关,可以用线偏振度参数描述。在90°散射角方向采用偏振相机,对球形和非球形纳米颗粒在0°,45°,90°,135°偏振方向上的动态光散射信号进行测量,结果表明:球形颗粒的线偏振度接近1,八面体颗粒的线偏振度略小于1,棒状颗粒的线偏振度小于1且随长径比增加而减小,纳米片及纳米线等非球形颗粒的线偏振度都有不同程度的减小。定义线偏振度为光学球体度,用以表征颗粒形貌,采用偏振图像动态光散射方法可以快速测量纳米颗粒的形貌分布。

基于改进Morozov偏差原理的动态光散射粒度反演

与窄粒度分布反演相比,宽粒度分布的反演难以获取与其相适应的正则参数。为提高宽分布颗粒体系反演结果的准确性,提出基于改进Morozov偏差原理,通过遗传算法迭代求取正则参数的方法,该方法通过小波包分解求出电场自相关函数的噪声分量,利用Morozov偏差原理建立适应值函数,在正则参数经验范围内生成初始种群,将适应值函数与初始种群带入遗传算法,全局寻找最优适应值对应的参数值作为正则参数。模拟与实测数据的反演结果表明,在窄分布颗粒体系条件下,所提方法与L-curve准则反演结果无显著差异,在宽分布条件下,所提方法反演结果的性能指标均优于L-curve准则,且避免了宽粒度分布条件下可能出现的虚假峰情况,表现出明显优于L-curve准则的宽分布反演效果。

不同尺寸纳米塑料团聚行为的定量研究

由于塑料制品大量使用和不当处置,环境中微塑料(尤其是纳米塑料)的地球化学行为已成为全球关注的热点问题。团聚效应是控制纳米塑料地球化学行为的重要因素。自然界中纳米塑料大小不一,然而已有的研究结果对于纳米塑料尺寸与团聚效应的关联性还存在一定矛盾。为揭示不同尺寸纳米塑料的团聚行为及影响作用机制,本文以50nm、100nm、200nm聚苯乙烯纳米塑料(PS50、PS100、PS200)为研究对象,利用动态光散射技术实时监测不同pH(3.0~10.0)及NaCl溶液(浓度0~800mmol/L)中纳米塑料的Zeta电位(ζ电位)和水动力直径,并通过理论计算得到三种粒径纳米塑料的临界团聚浓度(CCC)和总相互作用能。PS50、PS100和PS200去离子水中的初始ζ电位分别为-35.2mV、-35.1mV和-38.2mV,高的表面负电荷使其在水中保持分散。离子强度增加引起的电荷屏蔽效应促进了纳米塑料的团聚,PS50、PS100、PS200在NaCl溶液中CCC值分别为325mmol/L、296mmol/L、264mmol/L,表明初始ζ电位值接近时,粒径越小的纳米塑料越稳定,能够在环境中较长时间地迁移。随着pH从酸性增加至碱性,纳米塑料表面酸性官能团发生去质子化,负电荷增多,导致其团聚行为受到抑制。当pH=7时,即使是在较高离子强度下(400mmol/L NaCl),PS100和PS200基本恢复稳定,但PS50仍发生快速团聚,可能因为在此条件下PS50的ζ电位仍较小(-19.3mV)。通过回归分析可知,三种尺寸纳米塑料的团聚行为与ζ电位密切相关(r2为0.70~0.88)。因此在实际应用中,需要综合考虑溶液pH、离子强度以及纳米塑料自身尺寸等容易影响ζ电位的因素,以更精准地预测和评估纳米塑料在自然环境中的地球化学行为。

基于单模光纤的DLS粒径测量研究

动态光散射技术是一种测量纳米颗粒粒径分布的最有效方法。为了克服高浓度样品溶液中存在的多重散射效应,本文基于单模光纤搭建了一套DLS实验系统,传输光纤的输出端与接收光纤的接收端都作了抛光磨平处理。在模拟复杂工业环境下,分别用低浓度单分散、不同浓度单分散以及高浓度多分散性标准聚苯乙烯乳胶球悬浮液检测了该系统的适用性。实验结果表明,利用该系统可快速准确的测量体积分数达40%的聚苯乙烯乳胶球悬浮液中的纳米颗粒粒径及其分布。

合肥光源1 nm发射度的储存环初步物理设计研究

针对合肥光源未来升级为纳米级发射度储存环的计划,设计了一个紧凑的H6BA lattice物理方案。在800 MeV束流能量下,自然发射度为1.2 nm·rad,达到了所辐射的极紫外光的衍射极限发射度。考虑误差效应的6D动力学孔径在水平正方向上大于20 mm,可满足离轴注入的需要。由于束流能量和发射度均较低,束内散射和Touschek效应显著,考虑10%耦合情况下,平衡发射度增长了约50%,Touschek寿命为4.2 h,采用全耦合模式可较为有效地抑制这2种效应。

DLS粒度测量实验中噪声的影响与克服

噪声是始终存在于动态光散射实验的整个测量过程中,噪声的大小直接影响测量系统的信噪比大小与测量结果的准确性。根据噪声产生的物理原因,将动态光散射实验中的噪声分为外部环境噪声和设备内部噪声两大类。为了最大限度的降低噪声提高测量的准确性,在详细探讨影响动态光散射粒度测量实验中各种噪声的来源的基础上,分析了噪声对实验结果的影响,并提出相应解决的办法。

DLS粒度测量实验中噪声的影响与克服

噪声始终存在于动态光散射实验的整个测量过程中,噪声的大小直接影响测量系统的信噪比大小与测量结果的准确性。根据噪声产生的物理原因,将动态光散射实验中的噪声分为外部环境噪声和设备内部噪声两大类。为了最大限度的降低噪声以提高测量的准确性,在详细探讨影响动态光散射粒度测量实验中各种噪声来源的基础上,分析了噪声对实验结果的影响,并提出相应解决的办法。

海藻酸钠溶液的动静态光散射和扩散波谱研究

海藻因其优异特性,被广泛用于食品、生物医学等领域。海藻水溶液的性质很大程度受到溶液环境的影响。本文基于动静态同步光散射和扩散波谱技术分别研究pH和盐对于海藻酸钠稀溶液和浓溶液形态的影响,从溶液构象和网络结构多个尺度深入探讨宏观性能差异背后的作用机制。研究发现,溶液pH和盐的变化带来的海藻的电离平衡的改变,使得氢键和静电作用权重发生变化,这是不同溶液环境下粘度差异、凝胶化现象的根本原因。

油田用防垢剂的动态防垢评价与多重光散射分析及其应用

采用动态结垢评价法和多重光散射技术分析法研究了3种防垢剂FG-01、FG-02和FG-03的综合防垢效果以及作用机理。动态结垢实验结果表明,FG-03的综合防垢率可达96.24%,效果较好。多重光散射技术分析结果表明:在FG-03作用下,成垢溶液透光率较高,达到85%以上;垢颗粒平均粒径较小,在0.015μm以下,垢颗粒处于分散状态,不易聚集变大,FG-03作用机理以分散作用为主。现场试验效果表明,FG-03可使管道短节内壁干净光滑,防垢效果较好。