Interferometry of a single nanoparticle using the Gouy phase of a focused laser beam

We provide a quantitative explanation of the mechanism of the far-field intensity modulation induced by a nanoparticle in a focused Gaussian laser beam, as was demonstrated in several recent direct detection studies. Most approaches take advantage of interference between the incident light and the scattered light from a nanoparticle to facilitate a linear dependence of the signal on the nanoparticle volume. The phase relation between the incoming field and the scattered field by the nanoparticle is elucidated by the concept of Gouy phase. This phase relation is used to analyze the far-field signal-to-noise ratio as a function of exact nanoparticle position with respect to the beam focus. The calculation suggests that a purely dispersive nanoparticle should be displaced from the Gaussian beam focus to generate a far-field intensity change.     

Optical Spectroscopy of Single Impurity Molecules in Solids

Optical spectroscopy of a single impurity molecule provides the first truly local probe of host–guest interactions in doped solids. In conventional optical high-resolution experiments with many molecules only ensemble averages of the microscopic parameters can be obtained. In the single-molecule regime, the exquisite sensitivity of an individual dopant molecule to both the local environment and to external perturbations has been exploited in recent experiments to reveal a wealth of fascinating novel phenomena such as spectral diffusion in crystals and polymers, optical modification of a single impurity molecule (spectral hole-burning), local field measurements at the site of a single impurity molecule, and quantum optics in a solid.     

The influence of tetrahydroquinoline rings in dicyanomethylenedihydrofuran (DCDHF) single-molecule fluorophores

We have synthesized several series of DCDHF fluorophores with the amine donor either acyclic or constrained in one or two tetrahydroquinoline rings. The absorption and the fluorescence emission wavelengths and quantum yields have been determined and correlated with the specific donor structures. Generally, inclusion of the donor in a ring annulated to the benzene or naphthalene aromatic (Ar) π-core results in a bathochromic shift of absorption and emission accompanied by an increase in the quantum yield. Thus, the tetrahydroquinoline donor provides an efficient way to tailor the properties of fluorophores with substituted amines as electron-donating groups.     

Cy3-Cy5 covalent heterodimers for single-molecule photoswitching

Covalent heterodimers of the Cy3 and Cy5 fluorophores have been prepared from commercially available starting materials and characterized at the single-molecule level. This system behaves as a discrete molecular photoswitch, in which photoexcitation of the Cy5 results in fluorescence emission or, with a much lower probability, causes the Cy5 to enter into a long-lived, but metastable, dark state. Photoinduced recovery of the emissive Cy5 is achieved by very low intensity excitation (5 W cm(-2)) of the Cy3 fluorophore at a shorter wavelength. A similar system consisting of proximal, but not covalently linked, Cy3 and Cy5 has found application in stochastic optical reconstruction microscopy (STORM), a single-molecule localization-based technique for super-resolution imaging that requires photoswitching. The covalent Cy3-Cy5 heterodimers described herein eliminate the need for probabilistic methods of situating the Cy3 and Cy5 in close proximity to enable photoswitching. As proof of principle, these heterodimers have been applied to super-resolution imaging of the tubular stalk structures of live Caulobacter crescentus bacterial cells.     

非线性流固耦合问题的ALE分步有限元数值方法

推导了一种基于ALE（Arbitrary Lagrangian-Eulerian,即任意的拉格朗日-欧拉）描述下的带有自由液面不可压液体与运动结构非线性耦合问题的一种有限元数值计算方法,在时间域上采用分步格式计算,这种方法与混合插值方法比较其优点是速度和压力可使用同阶线性插值,给数值计算带来很大方便,将所得到的方法应用到结构与TLD（调谐式（液体阻尼器）装置之间的耦合问题,数值计算结果验证了本文所推导的方法。     

二层供应链网络均衡模型的研究

利用均衡理论和二层规划理论来研究供应链网络均衡问题。针对供应链网络中上下层成员之间具有的Stackelberg博弈特征以及同层成员之间具有的非合作博弈特征,构建了二层供应链网络的均衡模型,该模型实际上一个均衡约束的二层规划问题。此外,为了使得供应链网络在整体上实现最优,本文还在模型中引入回收契约以协调供应链网络。最后,利用罚函数法对模型进行了求解,算例分析说明了模型的合理性和有效性。     

A New Method of Constructing the Functional Integral Directly from Hamiltonian in N (> 2)-Dimensional State space

Using the new method of constructing the functional path integral in state space, we accomplished the construction of the functional path integral in N(> 2)-dimensional state space, and illustrated it with the example of n = 3 dimensional case that leads to the same results with others.