Synthesis,Luminescent Properties of aza-Boron-Diquinomethene Difluoride Complexes and Their Application for Fluorescent Security Inks

Two aza-boron-diquinomethene (aza-BODIQU) complexes bearing phenyl and carbazyl substituents were synthesized and characterized. Their photophysical properties were investigated systematically via spectroscopic and theoretical methods. Both complexes exhibit strong ¹π-π* transition absorptions (λ _abs = 400–540 nm) and intense fluorescent emissions (λ _em = 440–600 nm, Φ _PL  = 0.93 and 0.78) in CH₂Cl₂ solution and in solid state at room temperature. Compared to the complex with phenyl groups, the complex bearing carbazyl groups shows significant bathochromic shift in both absorption and emission. This could be attributed to the larger π-electron conjugation of the carbazole unit and intramolecular charge transfer feature from carbazole to aza-BODIQU component. In addition, the complexes exhibit intense photoluminescence and good stability on antacid, anti-alkali and stability in printing ink samples, which makes them potential dopants for the application of fluorescent security inks.     

Nonionic block copolymers assemble on the surface of protein bionanoparticle

Efficient delivery of therapeutic proteins to a target site remains a challenge due to rapid clearance from the body. Here, we selected tobacco mosaic virus (TMV) as a model protein system to investigate the interactions between the protein and a nonionic block copolymer as a possible protecting agent for the protein. By varying the temperature, we were able to obtain core-shell structures based on hydrophobic interactions among PO blocks and noncovalent interactions between TMV and EO blocks. The protein-polymer interactions were characterized by dynamic light scattering and isothermal titration calorimetry. This study establishes principles for the possible design of clinically useful protein delivery systems.     

Automating identification of avian vocalizations using time-frequency information extracted from the Gabor transform

Based on the Gabor transform, a metric is developed and applied to automatically identify bird species from a sample of 568 digital recordings of songs/calls from 67 species of birds. The Gabor frequency-amplitude spectrum and the Gabor time-amplitude profile are proposed as a means to characterize the frequency and time patterns of a bird song. An approach based on template matching where unknown song clips are compared to a library of known song clips is used. After adding noise to simulate the background environment and using an adaptive high-pass filter to de-noise the recordings, the successful identification rate exceeded 93% even at signal-to-noise ratios as low as 5 dB. Bird species whose songs/calls were dominated by low frequencies were more difficult to identify than species whose songs were dominated by higher frequencies. The results suggest that automated identification may be practical if comprehensive libraries of recordings that encompass the vocal variation within species can be assembled.     

论科学探究中学生的自我评价

在科学探究中重视学生自我评价意识和方法的培养对促进学生科学素养的发展具有重要意义。论述了科学探究各要素中学生的自我评价,给出了学生进行自我评价时需要回答的自我评估问题。     

圆管湍流减阻电磁力控制的直接数值模拟

利用直接数值模拟研究了圆管湍流减阻的电磁力控制问题. 在圆管表面布置一层交替排 列的条形电极和磁极,施加电压后在导电的流体介质中产生周向随时间变化的电磁力,通过 改变电磁力的大小和变化周期等参数可以使阻力大幅减少. 研究减阻率和控制参数的 关系,并研究了电磁力减阻的机理. 电磁力控制存在最优周期,阻力最大降 低24.2{\%}; 电磁力控制抑制了流向和法向速度的脉动,而周向脉动速度随振荡周 期的增大而增大.