喷雾干燥-碳热还原法制备介孔球形LiFePO4/C正极材料

以聚乙二醇(PEG)为辅助模板剂和碳源,以廉价的三价铁为铁源,采用喷雾干燥-碳热还原法制备了LiFePO4/C正极材料,并对该材料的微观结构及PEG添加量、焙烧温度等对材料结构和性能的影响进行了表征和研究.结果表明:制得的LiFePO4/C材料呈介孔结构,具有漂亮的差级球状形貌、高的比表面积和容量、优异的循环性;PEG...     

单臂氮氧自由基-抗磁金属Cd(Ⅱ)配合物的合成、结构和磁性研究

采用吡啶取代的单臂氮氧自由基与抗磁金属Cd(Ⅱ)进行配位,得到了一个新的单核配合物[Cd(1M4Py)3(OCN)2·2H2O](其中IM4Py=2-(4'-吡啶基)-4,4,5,5-四甲基咪唑啉-1-氧基自由基).单晶X-射线衍射结果表明,配合物属四方晶系,I4(1)/a空间群;晶胞参数a=1 443 9(3)nm,...     

阴阳直径等分圆的和谐美

用阴阳直径等分圆得到的圆形图案,有简单、对称、和谐之美。     

Skin collagen fiber-based radar absorbing materials

By using skin collagen fiber (CF) as raw material,Schiff base structure containing CF (Sa-CF) was synthesized through CF-salicylaldehyde reaction.Then a novel radar absorbing material (Fe-Sa-CF) was prepared by chelating reaction between Sa-CF and Fe 3+.The coaxial transmission and reflection method was used to analyze the complex permittivity and complex magnetic permeability of these CF-based materials,and the radar cross section (RCS) method was used to investigate their radar absorbing properties in the frequency range of 1.0-18.0 GHz.Experimental results indicated that the conductivity of CF increased from initial 1.08×10-11 to 2.86×10-6 S/cm after being transferred into Fe-Sa-CF,and its dielectric loss tangent (tanδ) in the frequency range of 1.0-17.0 GHz also increased.These facts suggest that the Fe-Sa-CF is electric-loss type radar absorbing material.In the frequency range of 3.0-18.0 GHz,Sa-CF (1.0 mm in thickness) exhibited somewhat radar absorbing property with maximum radar reflection loss (RL) of-4.73 dB.As for Fe-Sa-CF,the absorbing bandwidth was broadened,and the absorbing intensity significantly increased in the frequency range of 1.0-18.0 GHz where a maximum radar RL of-9.23 dB was observed.In addition,the radar absorbing intensity of Fe-Sa-CF can be further improved by increasing membrane thickness.When the thickness reached to 2.0 mm,the RL values of Fe-Sa-CF were-15.0-18.0 dB in the frequency range of 7.0-18.0 GHz.Consequently,a kind of novel radar absorbing material can be prepared by chemical modification of collagen fiber,which is characterized by thin thickness,low density,broad absorption bandwidth and high absorption intensity.     

Interpretation of the architectural design methods

文章结合笔者近年来的工作实践,从建筑设计因素入手,分析和阐述了建筑设计的几种方法,并提出了自己的一些看法.     

A two-tier location management mechanism for IMS

This paper proposed a two-tier location management mechanism(TTLM)by improving the currentregistration mechanism(CR)in IP Multimedia Subsystem(IMS).The TTLM includes the visited networkregistration and the home network registration,in which the visited network registration is responsible forre-registration in IMS.When subscriber roams,the location information of home network will be updatedby the visited network based on the change of user equipment(UE)' s IP address.Therefore the TTLMcan reduce the tim...     

Beta-catenin/TCF4 transactivates miR-30e during intestinal cell differentiation

The Wnt/beta-catenin/TCF4 pathway plays critical roles in the maintenance of small intestinal epithelium; however, downstream targets of the beta-catenin/TCF4 complex are not extensively characterized. We identified miR-30e as an immediate target activated by the beta-catenin/TCF4 complex. miR-30e was detected in the peri-nuclear region of the intestinal crypt IEC-6 cells. Bioinformatics analysis revealed clustered beta-catenin/TCF4 binding sites within the miR-30e promoter region. This promoter region was cloned into pGL3-control luciferase reporter vector, with the enhancer region removed. Transfection of pCMV-SPORT6-beta-catenin expression vector dose-dependently increased luciferase activity, and co-transfection of pCMV-SPORT6-TCF4 expression vector further enhanced the promoter activity. Dexamethasone-induced IEC-6 cells differentiation caused a 2.5-fold increase in miR-30e expression, and upon beta-catenin siRNA transfection, miR-30e increased 1.3-fold. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirmed the binding between beta-catenin/TCF4 complexes from IEC-6 nuclear extracts and the putative sequences in the miR-30e promoter. These results demonstrate that beta-catenin/TCF4 transactivates miR-30e during intestinal cell differentiation.     

Synthesis and photo-responsive behaviors of hollow polyazobenzene micro-spheres

By means of distillation precipitation polymerization, the silica-hybrid particles with polyazobenzene shell (PAzo@SiO₂) micro-spheres were prepared with 6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate (Azo-M) as monomer, divinylbenzene (DVB) as cross-linker, and ~250 nm vinylated sol-gel silica particles as template. Hollow polyazobenzene microspheres were further developed after selective removal of the silica cores with HF solution. When the content of DVB related to Azo-M is 20 wt%, the acetonitrile is 200 mL, and the polymerization time is 4.5 h, the hollow PAzo microspheres with about 20 nm shell are successfully fabricated. These hollow PAzo microspheres have excellent reversible photoisomerization, and their first-order rate constant of trans-cis isomerization only decreases 11.8% compared with homopolymer of azobenzene (Homo-PAzo).     

浅谈新闻写作角度和方法

文章结合自身从事新闻写作多年的经验,重点从新闻稿素材积累和选取的方法、选题的角度等分析和论述写作技巧。