Aqueous Synthesis of CdTe/CdSe Core/Shell Quantum Dots as pH-Sensitive Fluorescence Probe for the Determination of Ascorbic Acid

By controlling the reflux time and the quantity of the shell materials, different sizes of thioglycollic acid (TGA) modified CdTe/CdSe core/shell quantum dots were synthesized in aqueous solution. This type of QDs was used for sensitive and selective determination of ascorbic acid in commercial tablets. Under optimal conditions, a good linearity was observed between the relative fluorescence (FL) intensity and the concentration of ascorbic acid in the range of 4.0 to 64.0 μg/mL with a correlation coefficient of 0.9968. The limit of detection was 2.4 μg/mL. This method was applied to the determination of the ascorbic acid in Vitamin C tablets and Vitamin C Yinqiao pills, and satisfactory results were obtained.     

Fractional scanned carbon dioxide laser induces collagen remodelling in murine dermis

Resurfacing using a fractional CO₂ laser shows an important promise in the therapy on photoaged skin. The present study investigated that fractional CO₂ laser with a special sequential scanned manner induced the collagen remodelling in murine dermis. The results showed that laser resulted in the improvement of elasticity and histology in the murine dermis, meaning laser efficacy depends on both of the collagen formation and organization. We further investigated the relations between skin elasticity and type I, and type III collagen. These data demonstrated that laser could significantly lead to the collagen remodelling in murine dermis and induce neocollagenisis as a mode of resurfacing.     

《微分方程数值解》课程教学改革与实践

针对一般本科院校的教学实际,研讨《微分方程数值解》课程教学改革的一些体会,主要包括教学定位的确定、课程教学内容的优化、教学方法的改革以及教学手段的更新等问题.     

Variable selection using penalized empirical likelihood

This paper considers variable selection for moment restriction models.We propose a penalized empirical likelihood(PEL) approach that has desirable asymptotic properties comparable to the penalized likelihood approach,which relies on a correct parametric likelihood specification.In addition to being consistent and having the oracle property,PEL admits inference on parameter without having to estimate its estimator's covariance.An approximate algorithm,along with a consistent BIC-type criterion for selecting ...     

A Kind of New Three-Mode Coherent-Entangled State and Its Application

A kind of new continuous variable three-mode coherent-entangled state (CV-CES) is proposed in Fock space by the technique of integration within an ordered product (IWOP), which exhibits both the properties of coherent state and entangled state, and spans a complete and orthonormal representation. The conjugate state of CV-CES is derived by Fourier transformation. Moreover, the simple experimental protocol of generating a CV-CES is proposed by beam-splitters. As applications of this CV-CES, a three-mode entangled state and a three-mode squeezing-Fresnel operator are constructed.     

The multi-dimensional limiters for solving hyperbolic conservation laws on unstructured grids

Novel limiters based on the weighted average procedure are developed for finite volume methods solving multi-dimensional hyperbolic conservation laws on unstructured grids. The development of these limiters is inspired by the biased averaging procedure of Choi and Liu [10]. The remarkable features of the present limiters are the new biased functions and the weighted average procedure, which enable the present limiter to capture strong shock waves and achieve excellent convergence for steady state computations. The mechanism of the developed limiters for eliminating spurious oscillations in the vicinity of discontinuities is revealed by studying the asymptotic behavior of the limiters. Numerical experiments for a variety of test cases are presented to demonstrate the superior performance of the proposed limiters.     

Solvothermal synthesis, cubic structure and multicolor upconversion emission of ultrasmall monodisperse lanthanide-doped BaYF5 nanocrystals

Lanthanide (Ln³⁺) doped BaYF₅ (Ln=Yb³⁺, Er³⁺, Tm³⁺) nanocrystals (NCs) with a mean size of approximately 10 nm are synthesized by a solvothermal method using oleic acid as a stabilizing agent at 210 °C. The size of BaYF₅ NCs can be controlled by simply tuning the reaction parameters such as reaction temperature, reaction time and the molar ratio of F⁻/Y³⁺. The detailed structure investigation reveals that the as-synthesized BaYF₅ NCs are in the cubic structure with space group Fm3¯m instead of the reported tetragonal structure. Ln³⁺ cations occupy crystal lattice positions with lower point symmetry, which may lead to high upconversion efficiency under the excitation of a 980 nm diode laser. By adjusting the dopant concentrations of Yb³⁺, Er³⁺ and Tm³⁺, intense near-infrared, blue, yellow and white upconversion emissions are readily realized, respectively. The desirable property of the ultrasmall monodisperse NCs makes it the promising material for the applications in miniaturized solid-state light sources, multicolor three-dimensional display devices and fluorescent labels for biomedicine imaging.     

Surface plasmon resonance sensors based on Ag-metalized nanolayer in microstructured optical fibers

Surface plasmon resonance sensors based on Ag-metalized nanolayer in microstructured optical fibers are theoretically analyzed by using finite element method (FEM). In our simulations we use Drude-Lorentz model to describe the metal dielectric constant. The numerical results show that the sensitivity of Ag-metalized SPR sensor could reach 1167 nm/RIU and corresponding resolution is 8.57×10⁻⁵ RIU. Compared to conventional Au-metalized SPR sensors the performance of our device is obviously better.     

Study on inverse taper based mode transformer for low loss coupling between silicon wire waveguide and lensed fiber

We have simulated the coupling loss of three types of Inverse Taper and taper-lensed fiber using three dimensional (3D) semi-vectorial beam propagation methods (BPM) respectively. Our results showed that the performances of exponential inverse taper and quadratic inverse taper were better than the commonly used linear inverse taper. Especially, for TM mode the improvement in the reduction of devices size is 53% and 136% for exponential and quadratic inverse taper compared with the linear inverse taper.     

Multi-wavelength operation of LD side-pumped Nd:YAG laser

A dual-wavelength laser at 1064 nm and 1319 nm is obtained by a single Nd:YAG crystal rod. On the basis of 1064 nm and 1319 nm dual-wavelength laser installation, the second harmonic waves at 532 nm and 660 nm can be achieved by using non-linear frequency conversion technology. When 1064 nm and 1319 nm lasers oscillate simultaneously, the maximum output power is 30.5 W and 8.78 W, respectively. When the 1319 nm laser is restrained, we obtain a 35.6 W maximum output power at 1064 nm and by contrary 11.2 W at 1319 nm. The maximum output powers of 532 nm and 660 nm lasers are 5.34 W and 1.353 W when oscillating simultaneously. With one of them restrained, the maximum output power is 6.72 W at 532 nm and 1.90 W at 660 nm. The optimum repetition rate of the acousto-optic Q-switch is 10.5 KHz and 20.5 KHz for 532 nm and 660 nm lasers, respectively. The optical-to-optical conversion efficiency from the fundamental waves to the harmonic waves is 17.5% and 15.4%. The instability is less than 2%.