Observation of the resonant Raman behavior of individual single-walled carbon nanotubes

The different resonant Raman scattering process of single-walled carbon nanotubes (SWNTs) has been found between the Stokes and anti-Stokes sides of the radial breathing modes (RBMs), and this provides strong evidence that Raman spectra of some special diametric SWNTs are in resonance with their electronic transitions between the singularities in the one-dimensional electronic density of states in the valence and conduction bands, and other SWNTs axe beyond the resonant condition. Because of the coexistence of resonant and non-resonant Raman scattering processes for different diametric SWNTs, the relative intensity of each RBM does not reflect the proportion of a particular SWNT.

黑土侵蚀区生态重建的景观结构与功能分析

以黑龙江省拜泉县为案例,研究了区域生态恢复与生态重建对景观结构及其水土保持功能的调控.在GIS支持下,结合野外调查数据,对县域水平的生态建设成果进行了空间表达和定量辨识.对比分析1989年和2002年类型水平景观指数及13年来景观类型的转移面积和转移方向、林网宏观结构变化、水库塘坝空间分布与数量变化;土地利用和景观结构调整对水蚀、风蚀的控制以及水库塘坝的蓄水功能变化.结果表明,大规模生态建设下,区域景观类型数量和空间配置的变化对发挥其水土保持功能起到很好的调控作用.1989~2002年,耕地面积减少24 731.01 hm2,林草地和水体面积增加了13 567.53 hm2和1 190.97 hm2.全县55%的水土流失面积得到治理,82.2%的农田得到林网防护,43.7%的景观地表超渗径流得到集蓄.景观结构调整应注意增加林草地等类型斑块的聚集度;调节林网连接度、环度及网眼大小;增加水库塘坝的泄洪与灌溉配套设施等.

基于随机背包的公钥密码

该文构造了一个背包型公钥密码算法。该背包公钥密码具有如下优点:加解密只需要加法和模减法运算,因此加解密速度快;该算法是基于随机背包问题而不是易解背包问题而构造的;证明了在攻击者不掌握私钥信息情况下该密码算法能抵抗直接求解背包问题的攻击,包括低密度攻击和联立丢番图逼近攻击等;证明了攻击者能够恢复私钥信息与攻击者能够分解一个大整数是等价的。分析表明,该算法是一个安全高效的公钥加密算法。

Blue electroluminescent polymers with dopant-host systems and molecular dispersion features: polyfluorene as the deep blue host and 1,8-naphthalimide derivative units as the light blue dopants

We developed a series of highly efficient blue electroluminescent polymers with dopant-host systems and molecular dispersion features by selecting 1,8-naphthalimide derivatives as the light blue emissive dopant units, choosing polyfluorene as the deep blue emissive polymer host and covalently attaching the dopant units to the side chain of the polymer host. The polymers' EL spectra exhibited both deep blue emission from the polymer host and light blue emission from the dopant units because of the energy transfer and charge trapping from the polymer host to the dopant units.

Determination of total calcium in plasma by flow injection analysis with tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescent detection

We described here a new method for the determination of total calcium in plasma. The method is based on the precipitation of calcium with excess oxalate and the measurement of residual oxalate by flow injection analysis with Ru(bpy)(3)(2+) electrochemiluminescent detection. It has the advantages of extremely stable reagent, user-friendly instrument, high selectivity, good analytical recovery, wide dynamic range, and nice correlation with atomic absorption spectroscopy. The calibration plot for calcium is linear over a concentration range from 0.5 mmol L-1 to 4.8 mmol L-1, which is wider than those obtained by most other methods. The analytical recoveries for plasma calcium are 98.4-101.2% with coefficients of variation (CVs) of 1.96-2.52%. The within-day CVs range from 0.76% to 0.95%, and between-day CVs were from 1.12% to 1.46%. The time for each injection is one minute. Because the proposed method can be readily carried out on increasingly popular instruments for Ru(bpy)(3)(2+) ECL immunoassays and DNA probe assays, Ru(bpy)32+ ECL method is suitable for routine clinical analysis of calcium.

Syntheses of Ag, PbSe, and PbTe nanocrystals and their binary self-assembly exploration at low size-ratio

Nanocrystals of Ag, PbSe, and PbTe were prepared via a high-temperature organic solution approach, respectively. Using a size-selection technique, the size-distribution of each set of nanocrystals could be fine-tuned and finally monodisperse products were achieved. Superlattice structure of binary self-assemblies in low size-ratio were also explored and characterized by transmission electron microscopy. It is realized that a success of achieving binary self-assembly pattern is greatly dependent on several key factors including particle size-distributions, relative concentrations of both components, as well as the size-ratios between Ag and PbSe (or PbTe) nanocrystals.