Thermodegradable multisegmented polymer synthesized by consecutive radical addition‐coupling reaction of α,ω‐macrobiradicals and dithioester

A consecutive radical addition‐coupling reaction involving dithioester is applied to produce thermodegradable multisegmented polymer using α,ω‐dibromo polymer as precursor. The macroradical generated by single electron transfer process promoted by Cu/ligand from α,ω‐dibromo polymer can efficiently add to ethyl dithiobenzoate, which results intermediate adduct radical. The in situ formed adduct radical immediately undergoes crosscoupling reaction with macroradical, generating segmented polymer bridged with C? S bond. The consecutive radical addition‐coupling reaction generates multisegmented polymer linked by C? S bond following step‐growth mechanism. The multisegmented polymer can be thermodegraded in the presence of hydrogen atom donor or air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Comparison between Single-mode Treatment and Multi-mode Treatment of a Coaxial Bragg Resonator for a Terahertz Cyclotron Autoresonance Maser Oscillator

As a coaxial Bragg structure has more complex geometry configuration than a cylindrical or a planar Bragg structure, for simplicity of calculation a single-mode treatment is often adopted. However, heterogeneity of a coaxial Bragg structure always gives rise to the multi-mode conversion, which can change the performance of the resonator. Based on the scattering matrix method, detailed comparison between the single-mode treatment and the multi-mode treatment is presented to a coaxial Bragg resonator for a cyclotron autoresonance maser (CARM) oscillator operating in the higher-order mode TE₆₁ at frequency of 0.35 THz. Results indicate that there is a little difference between the results obtained by these two treatments to the upstream reflector due to its shallow ripple amplitude, whereas to the downstream reflector, due to its relatively deep ripple amplitude, an apparent difference occurs at the operating frequency and consequently it gives notable difference to the frequency response and Q-factor of the whole resonator. Optimization shows possible application of a coaxial Bragg resonator with a single higher-order mode operation in constructing a terahertz CARM oscillator.     

Femtocell技术的由来、优势和市场前景

Femtocell是用于增强室内无线覆盖的一项新技术,近年来受到了业界的广泛注意,发展十分迅速。本文叙述了Femtocell技术的由来和发展;讨论了Femtocell系统的优越性和需解决的关键技术;介绍了国外业界对Femtocell市场的预测。     

我国三大3G品牌定位的比较研究

介绍了我国3G牌照发放后,三大运营商都在进行各自品牌的建设,重点阐述了中国电信建立的是一个全新的移动业务形象和标识,中国移动则需要保持在2G时代的优势地位,而中国联通需要用创新改变旧联通的形象,探讨了"天翼"、 "G3"、 "沃"三大品牌的优劣.     

A Novel Adaptive Approach to Process Binary Fingerprint Images Using Directional Morphological Operations

An adaptive algorithm for removing false ridges, bridges and filling gaps in binary fingerprint images based on morphological operations is presented. A novel procedure for structuring elements design based on the specific fingerprint characteristic is described. Using the images from FVC2000 database, we have compared our method proposed here with the approach proposed by other ones. The Experimental results have demonstrated the efficiency of our method.     

Covalently Assembled Dipeptide Nanospheres as Intrinsic Photosensitizers for Efficient Photodynamic Therapy in Vitro

Monodispersed diphenylalanine‐based nanospheres with excellent biocompatibility are fabricated through a facile covalent reaction‐induced assembly. Interestingly, the nanospheres exhibit red autofluorescence. Most importantly, such assembled dipeptide nanospheres can serve as intrinsic photosensitizer to convert O₂ to singlet oxygen (¹O₂). Thus, photodynamic therapy in vitro can be achieved effectively. The versatile strategy could be extended to other biomolecules containing a primary amine group for the fabrication of potential intrinsic photosensitizers.     

Reduced Graphene‐Wrapped MnO2 Nanowires Self‐Inserted with Co3O4 Nanocages: Remarkable Enhanced Performances for Lithium‐Ion Anode Applications

A simple synthetic approach for graphene‐templated nanostructured MnO₂ nanowires self‐inserted with Co₃O₄ nanocages is proposed in this work. The Co₃O₄ nanocages were penetrated in situ by MnO₂ nanowires. As an anode, the as‐obtained MnO₂–Co₃O₄–RGO composite exhibits remarkable enhanced performance compared with the MnO₂–RGO and Co₃O₄–RGO samples. The MnO₂–Co₃O₄–RGO electrode delivers a reversible capacity of up to 577.4 mA h g^?1 after 400 cycles at 500 mA g^?1 and the Coulombic efficiency of MnO₂–Co₃O₄–RGO is about 96 %.