Influence of laser mode on splitting beam illumination effect of Dammann grating

The influences of various laser modes on the splitting beam effect of Dammann grating are studied in theory and by numerical simulation. The results show that fundamental mode laser resembles plane wave while high order mode laser differs from plane wave in the splitting beam effect by Dammann grating. Therefore, the fundamental mode laser is more suitable to be the light source to improve the energy efficiency in far-distance image detecting systems, such as laser image ladar, which use Dammann grating in the ilhlmination svstem.     

Influence of the illumination on the subband structure and?occupation in AlxGa1?xN/GaN heterostructures

The subband structure and occupation in the triangular quantum well at Al _x Ga_1−x N/GaN heterointerfaces have been investigated by means of temperature dependent Shubnikov–de Haas (SdH) measurements at low temperatures and high magnetic fields under illumination. After the illumination of the heterostructures, the total two-dimensional electron gas concentration increases, and the SdH oscillation amplitudes are enhanced when there is no additional subband occupation. It is also found that the energy separation between the subbands decreases after the illumination. We suggest that the illumination decreases the electric field and thus weakens the quantum confinement of the triangular quantum well at Al _x Ga_1−x N/GaN heterointerfaces. The GaN layer is thought to be the primary contributor of the excited electrons by the illumination.     

Electronic structure, magnetism and superconductivity of layered iron compounds

The layered iron superconductors are discussed using electronic structure calculations. The four families of compounds discovered so far, including Fe (Se, Te) have closely related electronic structures. The Fermi surface consists of disconnected hole and electron cylinders and additional hole sections that depend on the specific material. This places the materials in proximity to itinerant magnetism, both due to the high density of states and due to nesting. Comparison of density functional results and experiment provides strong evidence for itinerant spin fluctuations, which are discussed in relation to superconductivity. It is proposed that the intermediate phase between the structural transition and the SDW transition in the oxy-pnictides is a nematic phase.     

由单负材料组成的一维对称型光子晶体中的隧穿模

由电单负材料A和磁单负材料B构成了一维对称型光子晶体,数值计算表明其带隙中出现了一隧穿模. 材料层数增加,隧穿模宽度急剧变窄,而其位置不变.隧穿模的位置和宽度对入射角的变化都不太敏感. 材料的几何厚度减小,隧穿模的位置蓝移,而其宽度不变. μ_A, ε_B增加,隧穿模的位置红移,宽度减小. 利用隧穿模的以上特性可以实现对电磁波传播的动态调控.     

In vivo assessment of the permeability of the blood--brain barrier and blood-retinal barrier to fluorescent indoline derivatives in zebrafish

ABSTRACT: BACKGROUND: Successful delivery of compounds to the brain and retina is a challenge in the development of therapeutic drugs and imaging agents. This challenge arises because internalization of compounds into the brain and retina is restricted by the blood--brain barrier (BBB) and blood-retinal barrier (BRB), respectively. Simple and reliable in vivo assays are necessary to identify compounds that can easily cross the BBB and BRB. METHODS: We developed six fluorescent indoline derivatives (IDs) and examined their ability to cross the BBB and BRB in zebrafish by in vivo fluorescence imaging. These fluorescent IDs were administered to live zebrafish by immersing the zebrafish larvae at 7--8 days post fertilization in medium containing the ID, or by intracardiac injection. We also examined the effect of multidrug resistance proteins (MRPs) on the permeability of the BBB and BRB to the ID using MK571, a selective inhibitor of MRPs. RESULTS: The permeability of these barriers to fluorescent IDs administered by simple immersion was comparable to when administered by intracardiac injection. Thus, this finding supports the validity of drug administration by simple immersion for the assessment of BBB and BRB permeability to fluorescent IDs. Using this zebrafish model, we demonstrated that the length of the methylene chain in these fluorescent IDs significantly affected their ability to cross the BBB and BRB via MRPs. CONCLUSIONS: We demonstrated that in vivo assessment of the permeability of the BBB and BRB to fluorescent IDs could be simply and reliably performed using zebrafish. The structure of fluorescent IDs can be flexibly modified and, thus, the permeability of the BBB and BRB to a large number of IDs can be assessed using this zebrafish-based assay. The large amount of data acquired might be useful for in silico analysis to elucidate the precise mechanisms underlying the interactions between chemical structure and the efflux transporters at the BBB and BRB. In turn, understanding these mechanisms may lead to the efficient design of compounds targeting the brain and retina.     

Pure spin current generation in monolayer graphene by quantum pumping

We study a method to generate pure spin current in monolayer graphene over a wide range of Fermi energy by adiabatic quantum pumping. The device consists of three gate electrodes and two ferromagnetic strips, which induce a spin-splitting in the graphene through the proximity effect. A pure spin current is generated by applying two periodic oscillating gate voltages. We find that the pumped pure spin current is a sensitive oscillatory function of the Fermi energy. Large spin currents can be found at Fermi energies where there are Fabry-Perot resonances in the barriers. Furthermore, we analyze the effects of the parameters of the system on the pumped currents. Our predicted pumped spin current can be of the order of 100 nA which is measurable using the current technology. The proposed method is useful in the realization of graphene spintronic devices.     

Ultrasound-assisted extraction of three bufadienolides from Chinese medicine ChanSu

In this study, the application of ultrasound-assisted extraction (UAE) method was shown to be more efficient in extracting anti-tumor bufadienolides (bufalin, cinobufagin and resibufogenin) from important animal medicine of ChanSu than the maceration extraction (ME) and soxhlet extraction (SE) method. The effects of ultrasonic variables including extraction solvent, solvent concentration, solvent to solid ratio, ultrasound power, temperature, extraction time and particle size on the yields of three bufadienolides were investigated. The optimum extraction conditions found were: 70% (v/v) methanol solution, solvent to solid ratio of 10ml/g, ultrasound power of 125W, temperature of 20°C, extraction time of 20min and particle size of 60-80 mesh. The extraction yields of bufalin, cinobufagin and resibufogenin were 43.17±0.85, 52.58±1.12, 137.70±2.65mg/g, respectively. In order to achieve a similar yield as UAE, soxhlet extraction required 6h and maceration extraction required much longer time of 18h. The results indicated that UAE is an alternative method for extracting bufadienolides from ChanSu.     

相对论性力学系统的Birkhoff对称性与守恒量

提出了相对论性力学系统的一种新的对称性,并给出了此对称性导致的守恒量.提出了相对论性力学系统的Birkhoff对称性,即对应于相对论性力学系统的一组Birkhoff动力学函数的运动微分方程的解都满足从另一组Birkhoff动力学函数得到的运动微分方程.证明了与两组Birkhoff动力学函数分别给出的相对论性Birkhoff方程相关联的系数矩阵的各次幂的迹是系统的一个守恒量,从而将Currie和Saletan提出的力学系统的等效Lagrange函数定理拓展到了相对论性Birkhoff动力学系统.给出了两个例子以说明结果的正确性.     

Growth, Characterization and Theoretical Study of a Novel Organometallic Nonlinear Optical Crystal: CdHg(SCN)4(C2H5NO)2

A novel potentially useful second harmonic generation (SHG) organometallic nonlinear optical (NLO) crystal: cadmium mercury thiocyanate bis(N-methylformamide), CdHg(SCN)₄(C₂H₅NO)₂ (CMTN), has been prepared, and large high-optical-quality single crystals with dimensions up to 30 ×27×9 mm³ have been grown by the temperature-lowering method. Its structural, physicochemical and optical properties are characterized by elemental analyses, X-ray powder diffraction, Fourier transform infrared and Raman spectroscopy, thermal analysis, powder SHG measurements and UV/Vis/NIR transmission. The specific heat has been determined to be 515.5 J?mol^?1?K^?1 at 300 K. CMTN possesses good physicochemical stability up to 128.5^°C, exhibits powder SHG efficiencies 0.8 times that of urea and its UV transparency cutoff is 358 nm. By the use of the DFT/B3LYP/6-31G(d) method, the microscopic second order NLO behavior of CMTN has been investigated by computing the first-order hyperpolarizability together with that of CdHg(SCN)₄ (CMTC) and CdHg(SCN)₄(C₃H₈O₂) (CMTG) crystals. The results have been explained based on their crystal structures.     

正常金属-分子量子点-超导耦合系统的介观输运研究

运用非平衡格林函数理论、正则变换以及BCS平均场理论研究了正常金属-分子量子点-超导耦合系统（N-MQD-S）的介观输运,得到了系统的电流公式并选择适当的参数进行了数值计算。数值计算结果表明：电声子耦合强度 与线宽函数 对系统的输运行为有较大影响。当 增大时,由声子辅助隧穿所产生的共振峰将高于分子量子点自身能级产生的共振峰;当线宽函数 增大时,在Andreev反射共振峰的两侧将出现新的边峰。