聚合物整体柱微萃取与高效液相色谱联用检测水性化妆品中的性激素

建立了水性化妆品中睾酮、甲基睾酮和孕酮的聚合物整体柱微萃取和高效液相色谱联用检测方法。聚(甲基丙烯酸-乙二醇二甲基丙烯酸酯)毛细管整体柱作为萃取介质,表现出较大的萃取容量。实验优化了影响萃取效率的参数,包括萃取流速、样品溶液pH值、盐浓度以及有机相含量。样品经过磷酸盐溶液稀释和过滤后便可直接进行萃取分析。睾酮、甲基睾酮和孕酮在10～1000μg/L的浓度范围内具有良好的线性关系,相关系数均大于0.996;它们的检出限分别为2.3,2.8和4.6μg/L;日内及日间相对标准偏差分别小于7.7%和7.5%。本

Photoluminescence from Er-doped Si-in-SiNx thin films

Photoluminescence from Er3+-implanted Si-in-SiN, films emitting efficiently visible light were investigated. A Stark structure in the Er3+ photoluminescence spectrum was observed at room temperature, which reveals more than one site symmetry for the Er3+-centers in the Si-in-SiN, matrix. The correlation between the visible photoluminescence from the silicon nanoparticles and the 1.54 mu m emission from the Er3+-centers was discussed. (c) 2006 Elsevier B.V. All rights reserved.

Solid-state qubit measurement with single electron transistors

In this paper we consider the continuous weak measurement of a solid-state qubit by single electron transistors (SET). For single-dot SET, we find that in nonlinear response regime the signal-to-noise ratio can violate the universal upper bound imposed quantum mechanically on any linear response detectors. We understand the violation by means of the cross-correlation of the detector currents. For double-dot SET, we discuss its robustness against wider range of temperatures, quantum efficiency, and the relevant open issues unresolved.

PHOTOLUMINESCENCE INVESTIGATIONS OF CD1-XMNXTE UNDER HYDROSTATIC-PRESSURE

The photoluminescence of Cd1-xMnxTe with x=0.25, 0.40, and 0.60 is investigated at 77 K and different pressures. The pressure coefficients of the photoluminescence bands Cd0.75Mn0.25Te and Cd0.6Mn0.4Te are found to be positive and the magnitudes are about 8 X 10(-3) eV/kbar, which is in good agreement with the pressure coefficients of the interband transition. The pressure coefficient of the photoluminescence bands for Cd0.4Mn0.6Te is found to be -6 X 10(-3) eV/kbar, which is quite different from the pressure coefficient of the interband transition. The possible transition mechanism is discussed in terms of group theory and crystal field theory.

量子阱共振腔增强型光电探测器的高功率特性

通过测量1.55 μm量子阱共振腔增强型光电探测器的光电流随反向电压和光功率的变化关系,以及模拟能带结构、电场分布等特性,研究了量子阱共振腔增强型光电探测器的高功率特性.分析了光电流的产生机制,测量了1.064 μm量子阱共振腔增强型光电探测器的光电响应,模拟了具有不同势垒高度的量子阱共振腔增强型光电探测器的光电响应.从实验和模拟两方面证明了量子阱的势垒高度是影响量子阱共振腔增强型光电探测器高功率特性的最主要因素.

Stability shear stress and equilibrium cross-sectional geometry of sheltered tidal channels

This study relates tidal channel cross-sectional area (A) to peak spring discharge (Q) via a physical mechanism, namely the stability shear stress ( tau sub(S)) just necessary to maintain a zero gradient in net along-channel sediment transport. It is assumed that if bed shear stress ( tau ) is greater than tau sub(S), net erosion will occur, increasing A, and reducing tau similar to (Q/A) super(2) back toward tau sub(S). If tau < tau sub(S) there will be net deposition, reducing A and increasing tau toward tau sub(S). A survey of the literature allows estimates of Q and A at 242 sections in 26 separate sheltered tidal systems. Assuming a single value of tau sub(S) characterizes the entire length of a given tidal channel, it is predicted that along-channel geometry will follow the relation Ah sub(R) super(1) super(/) super(6) similar to Q. Along-channel regressions of the form Ah sub(R) super(1) super(/) super(6) similar to Q super( beta ) give a mean observed value for beta of 1.00 plus or minus 0.06, which is consistent with this concept. Results indicate that a lower bound on tau sub(S) (and an upper bound on A) for stable channels is provided by the critical shear stress ( tau sub(C)) just capable of initiating sediment motion. Observed tau sub(S) is found to vary among all systems as a function of spring tidal range (R sub(sp)) according to the relation tau sub(S) approximately 2.3 R sub(sp) super(0.79) tau sub(C). Observed deviations from uniform tau sub(S) along individual channels are associated with along-channel variation in the direction of maximum discharge (i.e., flood-versus ebb-dominance).

黄土塬区果园套种对土壤微生物及酶活性的影响

研究了黄土塬区塬面不同套种作物的幼树苹果园土壤微生物的分布和酶活性。结果表明，果园土壤中微生物的分布在果树行与套种行中是不均匀的，细菌和真菌多为果树行多于套种行；土壤的过氧化氢酶，蔗糖酶，脲酶以及中性磷酸酶活性在套种小麦的果园中以套作行高于果树行，而套种烤烟则使脲酶和中性磷酸酶活性有所降低。套种豆类有利于土壤肥力的均衡发展。

玛纳斯河流域50年绿洲扩张及生态环境演变研究

玛纳斯河流域绿洲开发和经济发展是新疆维吾尔自治区的典范,以不同时相的卫星影像、土地利用图和地形图为数据源,借助遥感和地理信息系统等先进技术,恢复了玛纳斯河流域过去50年来6个时期(1949,1962,1976,1989,1999和2001年)的绿洲分布格局和动态演化过程.研究表明,按照绿洲年扩张速率,该流域的绿洲扩张过程可分为两个阶段:1949~1976年为绿洲化阶段,因人口急剧增加,耕地面积急剧扩大,绿洲总面积从1949年的156.385km2扩张到1976年的3639.491km2;1976~2001