Recent Advances of Freestanding Cathodes for Li-S Batteries

Lithium-sulfur batteries (LSBs) with high energy density and low cost have been recognized as one of the most promising next-generation energy storage systems. Although it has taken decades of development, the practical application of LSBs has been hindered by several inherent obstacles, particularly the severe shuttle effect and sluggish reaction kinetics in the sulfur cathode. Various strategies have been proposed to address these problems via rational design of electrode materials and configurations. Freestanding sulfur cathode could be a promising strategy to improve the sulfur mass loading at the cathode level and energy density of LSBs. This minireview will briefly summary the recent advances in freestanding cathodes for LSBs. The advantages and disadvantages of various freestanding cathodes are discussed and the prospects for the development of flexible cathodes are envisioned.     

Nb(iPrNPMe2)3Fe–PMe3: A potential high reactivity heterobimetallic catalyst for acetylene cycloadditions

Alkynes cycloaddition reactions are powerful tools for constructing cyclic molecules with optimal atom efficiency, but these reactions cannot proceed at ambient temperature without transition-metal catalysts. In this work, a heterobimetallic complex featuring an Nb–Fe triple bond, Nb(ⁱPrNPMe₂)₃Fe–PMe₃, has been evaluated as the potential catalyst for acetylene cycloaddition, using density functional theory. The calculated results show that the singlet-state (i.e. ground-state) Nb(ⁱPrNPMe₂)₃Fe–PMe₃ can be applied to benzene synthesis, but is not suitable for cyclobutadiene. Benzene can be obtained easily at room temperature and is the unique product on the singlet potential surface. The irradiation of infrared-red light can drive the excitation of singlet Nb(ⁱPrNPMe₂)₃Fe–PMe₃ to its triplet state. Both benzene and cyclobutadiene can be formed on the triplet reaction potential surface due to their low energy barriers. Therefore, Nb(ⁱPrNPMe₂)₃Fe–PMe₃ is a potential high reactivity heterobimetallic catalyst for the cyclotrimerization of alkynes. In the reaction process, the catalytic active site of Nb(ⁱPrNPMe₂)₃Fe–PMe₃ moves from niobium to iron.     

A new solution of reducing polymer optical fiber losses

Polymethyl methacrylate (PMMA) is one of the most commonly used optical materials. However, the application of it in the area of optical communication is strongly limited by the intrinsic absorption loss of carbon-hydrogen stretching vibration. In this paper, we present a method to solve the problem by adopting the hollow-core fibers with cobweb cladding structure. The fibers use a single dielectric material and may solve the problem of structural support. Thus the feasibility of the “OmniGuide” fibers is improved, while a series of advantages of the “OmniGuide” hollow-core fiber are retained. It is promising that a fiber with low transmission loss, high bandwidth, large-core, and low costs can be designed and fabricated using PMMA. At the same time, a very broad range of the wavelengths (from visible to near infrared region, for instance, wavelengths at 0.65-1.12 μm, and even 1.30 μm, 1.54 μm and their neighbors) may be adopted for signal wavelength.     

Energy loss effect in high energy nuclear Drell-Yan process

The energy loss effect in nuclear matter, which is a nuclear effect apart from the nuclear effect on the parton distribution as in deep-inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the measured Drell-Yan production cross sections for 800 GeV proton incident on a variety of nuclear targets are analyzed within the Glauber framework which takes into account the energy loss of the beam proton. It is shown that the theoretical results with considering the energy loss effect are in good agreement with the FNAL E866 data.Arrival of the final proofs: 24 June 2003     

Detection of Pb2+ using a hydrogel swelling microcantilever sensor.

Hydrogels containing benzo-18-crown-6 were used to modify microcantilevers for measurements of the concentration of Pb2+ in aqueous solutions. These microcantilevers undergo bending deflection upon exposure to solutions containing various Pb2+ concentrations as the result of a swelling of the hydrogels. It was found that a concentration of 10(-6) M Pb2+ can be detected using this technology. Other cations, such as Na+, have no effect on the deflection of this cantilever. The cation K+, which also complexes with benzo-18-crown-6, could interfere with Pb2+ detection, but only at high concentrations (> 10(-4) M).     

利用半导体光放大器进行光脉冲消基座的理论研究

提出了一种利用半导体光放大器(SOA)联合可调谐光滤波器进行高阶孤子压缩消基座的新方法.进行了详尽的理论分析和优化.数值计算表明,在一定条件下,这种方法能够在不展宽脉冲的前提下,对基座进行有效地抑制.     

紫外波段CH2I2分子的光解离动力学研究

利用离子速度成像方法,研究CH2I2分子在277—305nm范围内若干波长处的光解离动力学.通过同一束激光经(2+1)共振多光子电离(REMPI)过程探测光解碎片I(2P32)和I(2P12),得到了不同激发波长处的离子速度分布图像,从而获得CH2I2光解产物的能量分配和角分布.实验发现,碎片CH2I自由基有很高的内能激发,约占总可资用能的80%,该能量分配可以较好地用冲击模型来解释.实验还发现,产物I(2P32)和I(2P12)具有很不相同的平动能分布,结合所得到的碎片能量分配和角分布,我们对碎片I(2P32)和I(2P12)生成机理进行了分析,指出CH2I2分子电子激发态的绝热和非绝热解离决定了碎片的平动能分布. 关键词： CH2I2 离子速度成像 绝热和非绝热解离     

Relativistic Electromagnetic Solitary Wave in a Cylindrical Magnetized Plasma

In the presence of an applied static and uniform magnetic field, a cylindrical Kadomtsev-Petviashivili equation is derived for a relativistic electromagnetic solitary wave propagating in collisionless plasma consisting electrons, positrons, and ions in the case of weak relativistic limit. This equation is solved in a stationary frame to obtain explicit expression for the velocity, amplitude and width of solitons. The amplitude of the solitary wave has a maximum value at a critical αc of the ratio of the ion equilibrium density to the electron one, and it increases as the applied magnetic field becomes larger.     

生物分子拉曼散射测定过程中荧光背景的抑制

拉曼共焦技术、表面拉曼增强技术以及降低入射激光强度的方法，被运用于SOD、DNA等生物分子拉曼散身实验中，以抑制其荧光背景，改善光谱质量。     

The Exact Hausdorff Measure Function of the Level Sets of Multi-parameter Symmetric Stable Process

In this paper, we investigate the Hausdorff measure for level sets of N-parameter Rd-valued stable processes, and develop a means of seeking the exact Hausdorff measure function for level sets of N-parameter Rd-valued stable processes. We show that the exact Hausdorff measure function of level sets of N-parameter Rd-valued symmetric stable processes of index α is Ф（r） = r^N-d/α （log log l/r）d/α when Nα 〉 d. In addition, we obtain a sharp lower bound for the Hausdorff measure of level sets of general （N, d, α） strictly stable processes.