Two 2D Metal‐organic Networks Based on a Rigid Imidazolate/Sulfonate Functionalized Ligand – Effect of the Coordination Modes of the Ligand on Crystal Structures

A rigid imidazolate/sulfonate functionalized ligand, 6‐(4‐sulfonatopheny)imidazo[4, 5‐f]isoindole‐5, 7‐dione (SPID) was designed and used for assembling reactions with Mn²⁺ and Cu²⁺ ions. Two 2D frameworks compounds, [Mn(H_‐1SPID)₂(DMAC)₂] ( 1 ) and [Cu(H_‐2SPID)(H₂O)₂] · 0.7DMAC · 0.3H₂O ( 2 ) (DMAC = N,N‐dimethylacetamide) were obtained. Single crystal X‐ray analyses show that 1 has a 2D (4, 4)‐net based on 4‐connected Mn²⁺ nodes and μ₂‐coordinated H_‐1SPID spacers, whereas compound 2 has a 2D (6, 3)‐net built of 3‐connected Cu²⁺ nodes and μ₃‐coordinated H_‐2SPID spacers. Additionally, the thermal behavior of 1 and 2 is presented.     

Improved list coloring algorithm in cognitive radio based on time cost and demand satisfaction

For the cognitive users to access the licensed frequency bands opportunistically, cognitive radio is the best solution to mitigate the spectrum resource scarcity at the moment. Dynamic spectrum allocation is a key technology to implement cognitive radio efficiently on the condition that the licensed users must not be interfered. Up to now, the spectrum allocation algorithms based on the graph model seldom focus on enhancing spectrum utilization, speedy accomplishing and requirement satisfaction simultaneously. In this paper, an improved algorithm is proposed to decrease time cost and increase demand satisfaction simultaneously based on a List-Coloring algorithm provided by Wei Wang research group. This improved algorithm was studied by handling connected component in parallel and depressing user’s priority which demand has been met, respectively. And the spectrum utilization is effectively guaranteed at the same time. Our experimental results show that the proposed algorithm is an efficient method. Compared with the original List-Coloring algorithm, the time cost is reduced obviously and the demand satisfaction is greatly improved while only a few bandwidth rewards are lost by using the algorithm proposed in our study.     

Dicarboxylic acid promoted immortal copolymerization for controllable synthesis of low‐molecular weight oligo(carbonate‐ether) diols with tunable carbonate unit content

Low‐molecular weight oligo(carbonate‐ether) diols are important raw materials for polyurethane formation, which with tunable carbonate unit content (CU) may endow new thermal and mechanical performances to polyurethane. Herein, facile synthesis of oligo(carbonate‐ether) diols with number average molecular weight (M_n) below 2000 g mol^?1 and CU tunable between 40% and 75% are realized in high activity by immortal copolymerization of CO₂/propylene oxide (PO) using zinc‐cobalt double metal cyanide complex (Zn‐Co‐DMCC) in the presence of sebacic acid (SA). M_n of the oligomer is in good linear relationship to the mole ratio of PO and SA (PO/SA) and hence can be precisely controlled by adjusting PO/SA. Besides, the molecular weight distribution is quite narrow due to the rapid reversible chain transfer in the immortal copolymerization. High pressure and low temperature are favorable for raising CU. In all the reactions, the weight fraction of propylene carbonate (W_PC) can even be controlled as low as 2.0 wt %, and the catalytic activity of Zn‐Co‐DMCC is above 1.0 kgg^?1 cat. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Dioxygen affinities of Schiff base cobalt(II) complexes with aza-crown or morpholino pendants

Abstract  

Schiff base Co(II) complexes, CoL₂¹–CoL₂⁶ with aza-crown or morpholino pendants were synthesized. The oxygenation constants (KO₂) of these complexes in MeOCH₂CH₂OMe solution were measured over the range of −5 to 25 °C, and the thermodynamic parameters (∆H ⁰, ∆S ⁰) for oxygenation were calculated based on these KO₂ values. The effects of different substituents on the Schiff base ligand with respect to the modulation of O₂-binding capability were explored. The results indicate that the dioxygen affinities of the Co(II) complexes are much more enhanced by aza-crown pendants than that by morpholino pendants, and the O₂-binding capabilities of the aza-crown pendants complexes can also be enhanced by adding Na⁺ cations.     

Synthesis and solvent‐dependent micellization of the amphiphilic block copolymer poly(styreneboronic acid)‐block‐polystyrene

The amphiphilic organoboron block copolymer poly (styreneboronic acid)‐block‐polystyrene ( PSBA‐b‐PS ) has been prepared through a postpolymerization modification route from the silicon‐functionalized block copolymer poly(4‐trimethylsilylstyrene)‐block‐polystyrene ( PSSi‐b‐PS ). PSBA‐b‐PS is obtained through highly selective reaction of PSSi‐b‐PS with BBr₃ at room temperature and subsequent hydrolysis of the BBr₂‐functionalized intermediate. Transmission electron microscopy studies demonstrate that PSBA‐b‐PS undergoes pH dependent micellization in aqueous solution. Different morphologies could be realized by using different mixtures of water and organic solvents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2438–2445, 2010     

DKSZ-Ⅲ电机实验装置的数字化改造

根据＂电力拖动自动控制系统＂课程特点及要求,本文针对DKSZ-Ⅲ电机控制系统实验装置,在模拟控制直流双闭环单元电路基础上,开发了数字控制双闭环调速的实验挂箱。数字实验挂箱硬件由数字信号处理器TMS320LF2407及相应的外围接口电路组成,软件采用C语言与汇编语言混合编程,并包括一个ASR和ACR调节器。该挂箱实现了直流双闭环的数字控制,为本课程提供了数字实验平台。     

Palladium‐Initiated Radical Cascade Stereoselective Iodofluoroalkylation/Cycloisomerization of Ene‐vinylidenecyclopropanes

A novel and convenient palladium‐initiated radical cascade stereoselective iodofluoroalkylation/cycloisomerization of ene‐vinylidenecyclopropanes with fluoroalkyl iodides has been developed. The reaction proceeds under mild reaction conditions with high atom economy and stereoselectivity, thereby allowing an efficient access to a variety of difluoromethylated or perfluoroalkylated pyrrolidines tethered with an alkyl iodide. Two plausible radical pathways for the transformation have been proposed on the basis of the results of control experiments and previous reports, which in one case it was thought that palladium(0) was an initiator rather than a catalyst.     

Enantioselective Hydrolysis of Phenyl Glycidyl Ether Catalyzed by Newly Isolated Bacillus Megaterium ECU1001

Microbial epoxide hydrolases from bacterial and fungal sources?1? are hi ghly versatile catalysts for the asymmetric hydrolysis of chiral epoxides which are extensively employed as useful building blocks for the synthesis of various biologically active products in the pharmaceutical and agrochemical industries. Microorganism means allows an unlimited supply of these enzymes for preparative -scale applications. Phenyl glycidyl ether (PGE), an aryl epoxide, is a potenti ally useful compound in the synthesis of chiral amino alcohols and bioactive com pounds such as ?blockers. No suitable biocatalyst with sufficiently high enan tioselectivity (E?20) for the kinetic resolution of this compound was previ ously found among bacteria and fungi. This prompted us to screen epoxide hydrola se-producing microorganisms with higher enantioselectivity toward phenyl glycid yl ether from soil samples.     

The detection of HBV DNA with gold-coated iron oxide nanoparticle gene probes

Gold-coated iron oxide nanoparticle Hepatitis B virus (HBV) DNA probes were prepared, and their application for HBV DNA measurement was studied. Gold-coated iron oxide nanoparticles were prepared by the citrate reduction of tetra-chloroauric acid in the presence of iron oxide nanoparticles which were added as seeds. With a fluorescence-based method, the maximal surface coverage of hexaethiol 30-mer oligonucleotides and the maximal percentage of hybridization strands on gold-coated iron oxide nanoparticles were (120 ± 8) oligonucleotides per nanoparticle, and (14 ± 2%), respectively, which were comparable with those of (132 ± 10) and (22 ± 3%) in Au nanoparticle groups. Large network aggregates were formed when gold-coated iron oxide nanoparticle HBV DNA gene probe was applied to detect HBV DNA molecules as evidenced by transmission electron microscopy and the high specificity was verified by blot hybridization. Our results further suggested that detecting DNA with iron oxide nanoparticles and magnetic separator was feasible and might be an alternative effective method.