Biodegradable poly(sebacic anhydride-co-caprolactone) multi-block copolymers: Synthesis, characterization, crystallinity and crystalline morphology

Biodegradable poly(sebacic anhydride-co-caprolactone) (PSA-co-PCL) multi-block copolymers were prepared by condensation of acylated PSA and PCL prepolymers with different weight ratios. The homopolymer and copolymers were characterized by ¹H-NMR, gel permeation chromatography (GPC), differential scanning calorimeter (DSC) and atom force microscope (AFM). ¹H-NMR and GPC has indicated the formation of PSA-co-PCL multi-block copolymers, in which PSA and PCL segments are randomly distributed. The incorporation of PCL segments into the molecule chains even at a content of 20 wt% could significantly decrease the molecular weight distribution of the copolymer and increase its weight average molecular weight, as compared with PSA homopolymer. DSC has revealed that the melting temperature and degree of crystallinity for both SA and CL components are strongly composition dependent, implying the hindrance effect of the two components on crystallinity of each other. AFM observation has shown the difference in crystalline structures between PSA and PCL phases in the copolymers. In-vitro degradation tests performed at 37 °C in PBS buffer solution (pH 7.4, 0.1 M) have demonstrated the acceleration of degradation rate of the sample with increasing SA content in the copolymer.     

Fe（Ⅲ）APO分子筛在芳香族化合物氧化反应中的催化活性

 Fe取代系列磷酸铝分子筛（FeAlPO4－5，FeAlPO4－11和FeVPI－5）在催化氧化芳香族化合物反应（如苯酚和苯的羟化、苯乙烯的环氧化以及萘酚的氧化）中具有很高的活性．系统研究的数据显示，在苯酚和苯的羟化及苯乙烯的环氧化反应中，FeAlPO4－5及FeAlPO4－11的活性与TS－1催化剂相近；在大分子萘酚的氧化反应中，FeVPI－5具有较高的活性，而小孔的TS－1则没有活性．比较不同催化剂的活性结果表明，骨架中的Fe（Ⅲ）是催化剂的活性中心．     

Tuning the Electronic Coupling and Electron Transfer in Mo2 Donor–Acceptor Systems by Variation of the Bridge Conformation

Assembling two quadruply bonded dimolybdenum units [Mo₂(DAniF)₃]⁺ (DAniF=N,N′‐di(p‐anisyl)formamidinate) with 1,4‐naphthalenedicarboxylate and its thiolated derivatives produced three complexes [{Mo₂(DAniF)₃}₂(μ‐1,4‐O₂CC₁₀H₆CO₂)], [{Mo₂(DAniF)₃}₂(μ‐1,4‐OSCC₁₀H₆COS)], and [{Mo₂(DAniF)₃}₂(μ‐1,4‐S₂CC₁₀H₆CS₂)]. In the X‐ray structures, the naphthalene bridge deviates from the plane defined by the two Mo?Mo bond vectors with the torsion angle increasing as the chelating atoms of the bridging ligand vary from O to S. The mixed‐valent species exhibit intervalence transition absorption bands with high energy and very low intensity. In comparison with the data for the phenylene analogues, the optically determined electronic coupling matrix elements (H_ab=258–345 cm^?1) are lowered by a factor of two or more, and the electron‐transfer rate constants (k_et≈10¹¹ s^?1) are reduced by about one order of magnitude. These results show that, when the electron‐transporting ability of the bridge and electron‐donating (electron‐accepting) ability of the donor (acceptor) are both variable, the former plays a dominant role in controlling the intramolecular electron transfer. DFT calculations revealed that increasing the torsion angle enlarges the HOMO–LUMO energy gap by elevating the (bridging) ligand‐based LUMO energy. Therefore, our experimental results and theoretical analyses verify the superexchange mechanism for electronic coupling and electron transfer.     

An ultrasensitive aptasensor for prostate specific antigen assay based on Exonuclease T-aided cyclic cleavage

An ultrasensitive electrochemical aptasensor is presented for prostate specific antigen(PSA) detection. DNA tetrahedronaptamer is designed, which not only facilitates the molecular self-assembly events,but also improves the recognition efficiency between PSA and aptamer sequence on the electrode interface. The DNA conformation on top of DNA tetrahedron changes accordingly, which can be further digested by Exonuclease T(Exo T), a type of single-strand specific nuclease. Electrochemical species are removed synchronously and the initial PSA level can thus be determined. A linear range from 0.5 pg mL~(-1) to50 ng mL~(-1) is achieved with the limit of detection(LOD) as low as 0.15 pg mL~(-1). Moreover, this proposed method is highly selective and is successfully applied to determine PSA in human serum samples.     

Plasmon coupling in the double-sector structure

A silver nanostructure consisting of double sectors is proposed in this paper. In addition, the plasmon resonance and electric field enhancement have been investigated theoretically. It is found that, in this structure, the multiple resonances produce, which is tunable by the parameter of the structure. The localized electromagnetic fields can be produced at the tips of the structure. In addition, the enhanced electromagnetic fields can be observed between the sectors in a wide scale at the lower energy peak. The result of the investigation has great significance for the production of practical nanostructures and the improvement of possible applications.     

Hopf bifurcation analysis in a Lorenz-type system

In this technical note, the Hopf bifurcation in a new Lorenz-type system is studied. By analyzing the characteristic equations, the existence of a Hopf bifurcation is established. Some corresponding dynamics are also discussed briefly. Numerical simulations are carried out to illustrate the main theoretical results.     

Syntheses and Bioactivity of o- or p-Trifluoromethylphenyl Phosphates

o- and p-Trifluoromethylphenyl phosphates designed as mechanism-based phosphotyrosine phosphatase inactivators have been prepared. Some of them show herbicidal activities.     

Markov Chain Monte Carlo (MCMC) Method for Studying Magnetic Behaviors in Trinuclear Cobalt(II) Compound

A Co^II coordination polymer built from a mixed azide and zwitterionic pyridinium ions and its temperature‐dependent magnetic properties are described. We used the Markov chain Monte Carlo (MCMC) method to fit the data, and found the following results: (1) there are strong correlations between the model parameters; (2) the data at above 28 K are well fitted by the magnetism model.