拉曼光谱编码的荧光液相生物芯片检测系统研究

随着医疗诊断需求的增加,生物分子检测技术越来越受到人们的重视,液相生物芯片技术作为一种高通量,多通道的分子检测手段在近几年得到了飞速发展。通过层层自组装方法制备以微片为载体的拉曼光谱编码液相生物芯片,并利用自行搭建的一套高灵敏度、高分辨率的光学系统,实现对液相生物芯片的定性与定量分析。光学系统由拉曼光谱检测系统与荧光显微成像系统耦合而成。在拉曼光谱检测系统中激光器发射出785 nm波长的激光,通过二向色镜,带反反射镜与物镜汇聚到样品上,样品产生的拉曼散射光,经物镜,带反反射镜,二向色镜与拉曼滤波片,最后通过凹透镜聚焦到光谱仪的狭缝上,光谱仪色散实现在线阵CCD上拉曼光谱的获取。荧光显微成像系统应用光学成像原理,通过调节凹透镜与405 nm的激发光之间的距离,使激发光通过物镜均匀的照射到样品之上,样品激发出的荧光,通过物镜,带反反射镜,二向色镜,滤波片与相应的凹透镜,最后成像到面阵CCD上。改进传统便携式拉曼光谱检测系统光路并选用相应波段的带反反射镜与焦距20倍的物镜完成拉曼光谱检测系统与荧光显微成像系统的耦合。为了减少两路系统之间的相互影响选用合适的二向色镜以及滤波片,在提高耦合系统获取数据的准确性中有着重要的作用。该系统通过对反应之后的液相生物芯片进行拉曼光谱检测,以完成对每个编码玻片的定性识别,即解码;同时激发反应后液相生物芯片的荧光并采集荧光强度图,根据每个解码玻片上的荧光强度值完成对目标检测物的定量分析。区别于传统荧光编码液相生物芯片, 拉曼光谱编码具有稳定性更强,光谱分辨率更高等优点。该光学系统集拉曼光谱检测系统与荧光显微成像系统于一体,解决了目前未有基于拉曼编码的液相生物芯片的检测系统的问题,并且可同时对多种目标物进行识别和定量分析,提升了实验结果的准确性。     

The Boson peak interpretation and evolution in confined amorphous water

We study the evolution of the Boson peak for water confined in cement paste obtained by means of Inelastic Neutron Scattering from room temperature to the deep supercooled regime. We analyze the data in terms of a universal-like model, developed for glass forming liquids in the frame of the energy landscape. In such a way it is possible to discriminate between the fragile and strong glass forming character of supercooled liquids and the dynamical crossover, fragile to strong, between them. Hence, we confirm the link between the Boson peak and the water polymorphism. In particular, the main result is represented by a crossover from a local energetic minima configuration to that characteristic of saddle points on going towards the deep supercooled regime up to the dynamical arrest.     

基于元件组合理论的砂岩动态损伤本构模型

采用分离式霍普金森压杆（SHPB）系统,对砂岩进行不同速度下的冲击试验,得到砂岩的应变率效应特征以及典型的动态本构曲线。该曲线分为近似线弹性阶段、塑性阶段、塑性增强阶段和正向卸载阶段。通过组合模型的方法,构建了砂岩含损伤的动态本构模型,借助LS-DYNA软件中的用户材料子程序UMAT接口实现对本构模型的二次开发,并对砂岩在冲击速度为7.5、9.5、11.5和13.5 m/s 4种情况下的SHPB动态冲击压缩试验进行模拟。结果表明:所构建的模型可以很好地描述砂岩的应变率效应和应力-应变曲线弹性段,并且动态峰值强度、最大应变均与试验结果一致,应变率、峰值强度、最大应变与试验结果的相对误差不超过10%。所构建的砂岩动态本构模型能够准确地描述砂岩在冲击作用下的动态力学特性。     

Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface

In this work we study the turbulence modulation in a viscosity-stratified two-phase flow using Direct Numerical Simulation (DNS) of turbulence and the Phase Field Method (PFM) to simulate the interfacial phenomena. Specifically we consider the case of two immiscible fluid layers driven in a closed rectangular channel by an imposed mean pressure gradient. The present problem, which may mimic the behaviour of an oil flowing under a thin layer of different oil, thickness ratio h₂/h₁ =?9, is described by three main flow parameters: the shear Reynolds number Re _τ (which quantifies the importance of inertia compared to viscous effects), the Weber number We (which quantifies surface tension effects) and the viscosity ratio λ = ν₁/ν₂ between the two fluids. For this first study, the density ratio of the two fluid layers is the same (ρ₂ = ρ₁), we keep Re _τ and We constant, but we consider three different values for the viscosity ratio: λ =?1, λ =?0.875 and λ =?0.75. Compared to a single phase flow at the same shear Reynolds number (Re _τ =?100), in the two phase flow case we observe a decrease of the wall-shear stress and a strong turbulence modulation in particular in the proximity of the interface. Interestingly, we observe that the modulation of turbulence by the liquid-liquid interface extends up to the top wall (i.e. the closest to the interface) and produces local shear stress inversions and flow recirculation regions. The observed results depend primarily on the interface deformability and on the viscosity ratio between the two fluids (λ).     

Flame Induced Flow Features in the Presence of Darrieus-Landau Instability

The onset of hydrodynamic or Darrieus-Landau (DL) instability can largely impact on premixed flame morphology, turbulent flame speed and induced flow field. In this work, we focus on the latter induced flow by means of two dimensional direct numerical simulations (DNS) of slot burner flames performed in a parametric fashion. Results from linear stability analysis are used to select the adequate parameter range to be investigated. The presence of DL instability is initially assessed using a recently proposed statistical marker related to flame morphology. The differences between stable and unstable flames are then statistically investigated, utilizing a single, laminar, DL-induced corrugation as a reference state. Such DL-induced effects are investigated at various turbulence intensities, in terms of local propagation, induced strain rate patterns and flow field as well as vorticity production and transformation. Using displacement speed as a measure of local propagation, no noticeable statistical difference is observed between stable and unstable flames while strain rate and vorticity patterns are shown to be largely influenced by the DL induced morphology. From the modeling point view, an enhancement of counter gradient type transport for turbulent scalar fluxes is observed for hydrodynamically unstable flames.     

Multiplicative non-Gaussian noise and additive Gaussian white noise induced transition in a piecewise nonlinear model

We study the transition problems in a piecewise nonlinear model induced by correlated multiplicative non-Gaussian noise and additive Gaussian white noise. Firstly, applying the path integral approach, the unified colored noise approximation, the analytical expression of the steady-state probability density function (SPD) is derived. Then the change regulation of the SPD is analyzed with the change of the strength and relevance of multiplicative noise and additive noise. From numerical computations we obtain some new nonlinear phenomena: the transition can be induced by the cross-correlation strength between noises, the non-Gaussian noise intensity and the Gaussian noise intensity as well as the non-Gaussian noise deviation parameter. This indicates that the effect of the non-Gaussian noise intensity on SPD is the same as that of the Gaussian noise intensity. Moreover, we also find the correlation time of the non-Gaussian noise can not induce the transition.     

A convolutional neural network approach to calibrating the rotation axis for X‐ray computed tomography

This paper presents an algorithm to calibrate the center‐of‐rotation for X‐ray tomography by using a machine learning approach, the Convolutional Neural Network (CNN). The algorithm shows excellent accuracy from the evaluation of synthetic data with various noise ratios. It is further validated with experimental data of four different shale samples measured at the Advanced Photon Source and at the Swiss Light Source. The results are as good as those determined by visual inspection and show better robustness than conventional methods. CNN has also great potential for reducing or removing other artifacts caused by instrument instability, detector non‐linearity, etc. An open‐source toolbox, which integrates the CNN methods described in this paper, is freely available through GitHub at tomography/xlearn and can be easily integrated into existing computational pipelines available at various synchrotron facilities. Source code, documentation and information on how to contribute are also provided.     

A class of linear viscoelastic models based on Bessel functions

In this paper we investigate a general class of linear viscoelastic models whose creep and relaxation memory functions are expressed in Laplace domain by suitable ratios of modified Bessel functions of contiguous order. In time domain these functions are shown to be expressed by Dirichlet series (that is infinite Prony series). It follows that the corresponding creep compliance and relaxation modulus turn out to be characterized by infinite discrete spectra of retardation and relaxation time respectively. As a matter of fact, we get a class of viscoelastic models depending on a real parameter \(\nu > -1\). Such models exhibit rheological properties akin to those of a fractional Maxwell model (of order 1/2) for short times and of a standard Maxwell model for long times.     

光电经纬仪机电一体化耦合特性

区别于传统刚体控制模型,将结构动态设计方法与控制理论相结合,构建了光电经纬仪的柔性机电耦合控制模型,分析了该模型的结构基频、阻尼比等机械因素与控制带宽的耦合关系,并提出了光电经纬仪动态量化设计准则.实验表明:光电经纬仪结构谐振频率ω_n应尽可能地远大于系统谐振频率ω_r,至少满足ω_n≥3ω_r.该方法有效可行,可解决高精度大型经纬仪机电谐振问题,为设计快速响应、高跟踪精度的光电经纬仪提供了工程依据.     

A paradigmatic minimal system to explain the Ziegler paradox

The destabilization effect of damping on a class of general dynamical systems is discussed. The phenomenon of jump in the critical value of the bifurcation parameter, in passing from undamped to damped system, is view in a new perspective, according to which no discontinuities manifest themselves. By using asymptotic analysis, it is proved that all subcritically loaded undamped systems are candidate to become unstable, provided a suitable damping matrix is added. The mechanism of instability is explained by introducing the concept of modal dampings, as the components of the damping forces along the unit vectors of a non-orthogonal eigenvector basis. Such quantities can change sign while the load changes the eigenvectors of the basis, thus triggering instability. A paradigmatic, non-physical, minimal system has been built up, admitting closed-form solutions able to explain the essence of the destabilizing phenomenon. Series expansions carried out on the exact solution give information on how to deal more complex systems by perturbation methods.