Treecode-based generalized Born method

We have developed a treecode-based O(N log N) algorithm for the generalized Born (GB) implicit solvation model. Our treecode-based GB (tGB) is based on the GBr6 [J. Phys. Chem. B 111, 3055 (2007)], an analytical GB method with a pairwise descreening approximation for the R6 volume integral expression. The algorithm is composed of a cutoff scheme for the effective Born radii calculation, and a treecode implementation of the GB charge-charge pair interactions. Test results demonstrate that the tGB algorithm can reproduce the vdW surface based Poisson solvation energy with an average relative error less than 0.6% while providing an almost linear-scaling calculation for a representative set of 25 proteins with different sizes (from 2815 atoms to 65456 atoms). For a typical system of 10k atoms, the tGB calculation is three times faster than the direct summation as implemented in the original GBr6 model. Thus, our tGB method provides an efficient way for performing implicit solvent GB simulations of larger biomolecular systems at longer time scales.     

Colorimetric and ratiometric fluorescent chemosensor based on diketopyrrolopyrrole for selective detection of thiols: an experimental and theoretical study

A colorimetric and ratiometric fluorescent thiol probe was devised with diketopyrrolopyrrole (DPP) fluorophore. The probe gives absorption and emission at 523 and 666 nm, respectively. In the presence of thiols, such as cysteine, the absorption and emission band shifted to 479 and 540 nm, respectively. Correspondingly, the color of the probe solution changed from purple to yellow, and the fluorescence changed from red to yellow. The emission intensity at 540 nm was enhanced by 140-fold. The Stokes shift of probe 1 (107 nm) is much larger than the unsubstituted DPP fluorophore (56 nm). Mass spectral analysis demonstrated that besides the expected Michael addition of thiols to the C═C bonds, the CN groups of the malonitrile moieties also react with thiols to form 4,5-dihydrothiazole structure. Probe 1 was used for fluorescence imaging of intracellular thiols. In the presence of thiols, both the green and red channel of the microscopy are active. With removal of the intracellular thiols, signal can only be detected through the red channel; thus, ratiometric bioimaging of intracellular thiols was achieved. The ratiometric response of probe 1 was rationalized by DFT calculations. Our complementary experimental and theoretical studies will be useful for design of ratiometric/colorimetric molecular probes.     

Acid and alkali effects on the decomposition of HMX molecule: a computational study

The stored and wasted explosives are usually in an acid or alkali environment, leading to the importance of exploring the acid and alkali effects on the decomposition mechanism of explosives. The acid and alkali effects on the decomposition of HMX molecule in gaseous state and in aqueous solution at 298 K are studied using quantum chemistry and molecular force field calculations. The results show that both H(+) and OH(-) make the decomposition in gaseous state energetically favorable. However, the effect of H(+) is much different from that of OH(-) in aqueous solution: OH(-) can accelerate the decomposition but H(+) cannot. The difference is mainly caused by the large aqueous solvation energy difference between H(+) and OH(-). The results confirm that the dissociation of HMX is energetically favored only in the base solutions, in good agreement with previous HMX base hydrolysis experimental observations. The different acid and alkali effects on the HMX decomposition are dominated by the large aqueous solvation energy difference between H(+) and OH(-).     

代数数极小多项式的近似重构

给出了代数数极小多项式近似重构的误差控制条件,进而基于同步整数关系探测算法SIRD,得到一个从代数数近似值重构其准确极小多项式的完备的新算法,从而将“采用近似计算获得准确值”这一思想的适用范围从有理数扩展到代数数.     

Improving Mass Transfer in Gas-Liquid by Ionic Liquids Dispersion

This study investigates effects of dispersed ionic liquids on chemical absorption of CO₂ in alkanolamine aqueous solution. Oil-in-water emulsion has been prepared, whose continuous phase is trethanol amine aqueous solution, and dispersed phase is an ionic liquid, 1-octyl-3methyl imidazole six phosphate fluoride. The morphololgy of dispersion has been observed by visual method. Absorption rates are linearly fitted based on experimental data. Results show that a mass transfer enhancement has been realized by ionic liquids dispersion. The collaborative action of hydrodynamic effect and shuttle effect is proved to be the main mechanism that ionic liquids dispersion enhances gas absorption. The research indicates that dispersed ionic liquids can bring some advantages, higher absorption rate, lower corrosion for equipment, and higher regeneration efficiencies.     

32路光纤激光相干阵列的相位锁定

报道了32路光纤激光相干阵列的相位锁定实验研究。搭建了32路光纤激光相干阵列实验系统,基于现场可编程逻辑阵列(FPGA)设计制作了高速高精度相位控制器。当相位控制器执行随机并行梯度下降(SPGD)算法对各路激光的相位进行锁定时,相干阵列输出的激光功率与不进行相位锁定时相比提高了约26倍。     

Spectral Analysis and Determination of Palladium II Based on the Environment-Friendly and Water-Soluble Polymer

The environment-friendly and water-soluble polymer was prepared via ring-opening reaction between polyvinyl alcohol (PVA) and 3-epoxypropoxy fluorescein (EPF). Based on the quenching of fluorescence signals of PVA–EPF in the 520 nm wavelength and relative quenched intensity is good linear with the concentration of palladium II. A simple, rapid, sensitive, and specific detection method for palladium II is proposed. In comparison with traditionary methods, the present method is environment-friendly, stable, easy to operation, more water-soluble, and cheaper. The results suggested that PVA–EPF may offer potential as a reusable polymer sensor for palladium II ion in aqueous solution.     

一道数列问题的多种解法及拓展

针对一道已知通项关系求证数列收敛的问题,分别利用夹逼准则、单调有界原理和函数图像性质,给出三种证明方法,并推广得出这类问题的一般形式及其解。     

Structural characterization of ammonium molybdophosphate with different amount of cesium adsorption

Powdered crystal AMP was synthesized by precipitation method and different Cs-loading AMP samples were prepared in this work. They were studied by modern methods of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) to gain a better understanding of the ion exchange mechanism of ammonium molybdophosphate (AMP). The XRD patterns combined with the FT-IR analysis indicate that the Keggin structure is retained after Cs adsorption, while the changes of certain characteristic diffraction peaks show crystal lattice distortion caused by the mismatching sizes of Cs⁺ and [NH₄]⁺. The TGA showed that the weight percent of H₂O and [NH₄]⁺ decreases as the amount of Cs adsorbed onto AMP increases, which corresponds with the theory of isomorphous exchange.     

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.