吲哚化合物绿色高效的硫氰酸化反应

本文报道了在温和绿色的条件下,以过氧化氢（H₂O₂）作为氧化剂,进行吲哚化合物区域选择性硫氰酸化反应。结果表明：该反应体系中,无论是氮取代吲哚还是游离氨基吲哚均可获得较高的产率。产物2a～2o的结构经¹H NMR和¹³C NMR表征。该方法的主要特点是反应条件温和,反应时间短,产率高。     

Detection of bleomycin based on N and S co-doped graphene quantum dots as a fluorescence probeEI北大核心CSCD

N and S co-doped graphene quantum dotsNS-GQDswith excellent fluorescence properties were synthesized by hydrothermal method using citrate and thiourea as ingredientsand were characterized. The fluorescence signal was notably reduced in the presence of single stranded DNAssDNAsince ssDNA can adsorb on the surface of NS-GQDs through p-p stacking interaction. Whereas a significantly restored fluorescence signal was observed in the presence of bleomycinowing to the irreversible cleavage of ssDNA by bleomycin with Fe2+ as cofactor. Thusa fluorescence sensor for bleomycin detection was developed. The linear range was from 1.8 to 1200 nmol/L and the detection limit was 0.25 nmol/L. The method was used to detect bleomycin content in human serum samples with satisfactory results. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

A stochastic expectation-maximization algorithm for the analysis of system lifetime data with known signature

Statistical estimation of the model parameters of component lifetime distribution based on system lifetime data with known system structure is discussed here. We propose the use of stochastic expectation-maximization (SEM) algorithm for obtaining the maximum likelihood estimates of model parameters based on complete and censored system lifetimes. Different ways of implementing the SEM algorithm are also studied. We have shown that the proposed methods are feasible and are easy to implement for various families of component lifetime distributions. The proposed methodologies are then illustrated with two popular lifetime models—the Weibull and Birnbaum-Saunders distributions. Monte Carlo simulation is then used to compare the performance of the proposed methods with the corresponding estimation by direct maximization. Finally, two illustrative examples are presented along with some concluding remarks.     

Microstructure and Thermal and Tensile Properties of Poly(vinyl alcohol) Nanocomposite Films Reinforced by Polyacrylamide Grafted Cellulose Nanocrystals

Abstract

Polyacrylamide grafted cellulose nanocrystals (CNC-g-PAM) were incorporated into poly(vinyl alcohol) (PVA) by a solution casting method to fabricate nanocomposite films with enhanced thermal and tensile properties. The microstructure and the thermal and tensile properties of the PVA/CNC-g-PAM nanocomposite films were investigated as a function of CNC-g-PAM content. Infrared spectroscopy corroborated the presence of hydrogen bonds between PVA and the PAM on the surface of the CNC. Polarized optical microscopy and scanning electron microscopy revealed good dispersion of the CNC-g-PAM in the PVA matrix and good interfacial compatibility. Accordingly, the initial degradation temperature of the nanocomposite films was elevated slightly compared to pristine PVA film. The glass transition temperature, melting temperature, and crystallinity of the PVA also varied slightly after the incorporation of the CNC-g-PAM. At both 0% and 50% RH, the nanocomposite films showed an obvious increase of elastic modulus, no apparent change of breaking strength and a drastic reduction of elongation at break with increasing CNC-g-PAM content.     

Rotational analysis of the (3, 6) band in the comet-tail (AΠi -XΣ) system of CO

The direct observation and rotational analysis of the (3, 6) band in the comet-tail (A²Π_i-X²Σ⁺) system of CO⁺ are carried out for the first time employing optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy. That 193 lines are assigned to this band ranging from 12 100 to 12 370 cm⁻¹ results in most accurate molecular constants by nonlinear least-squares fitting procedure employing the effective Hamiltonians.     

Study of (1, 4) band in the comet-tail (AΠi-XΣ) system of CO

Ro-vibrational spectrum of the (1, 4) band in the comet-tail system of CO⁺ cation is observed employing the optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy in the range of 13 189-13 472 cm⁻¹. Two hundred and eighteen spectral lines are assigned to 12 branches of this band for the first time, thus, precise molecular constants of the levels involved are obtained by nonlinear least-squares fitting procedure combining with our previous spectrum of the (1, 2) band.     

Comparative study on the interaction of DNA with three different kinds of surfactants and the formation of multilayer films

The interactions between double-stranded DNA (dsDNA) and three different kinds of surfactants, i.e., cationic, anionic, and nonionic surfactants, were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and UV-vis spectroscopy. Multilayer films composed of DNA and surfactants were prepared at gold electrode by electrostatic or hydrophobic interactions. It was found that the cationic surfactant, CTAB, can bind to DNA by electrostatic interaction, and the electron transfer resistance of CTAB-DNA complex film increases first and then decreases with CTAB concentration. The anionic surfactant, LAS, can bind to DNA but by hydrophobic interaction, and the electron transfer resistance of the complex film keeps decreasing with LAS concentration. Nonionic surfactants can also directly bind to DNA by hydrophobic interaction. All the three different kinds of surfactants can form multilayer films with DNA on the electrode surface. The chemical structure of DNA keeps unchanged during interacting with these surfactants. The binding modes of DNA with these three different kinds of surfactants were also deduced.     

Unsteady heating of metallic particles in a rarefied plasma

Analytical results are presented concerning the unsteady heating of a metallic spherical particle innnersed in a rarefied plasma. The results show that the tinte periods required for the solid-phase heating, melting, liquid-phase heating, and evaporation are all proportional to the particle radius. For estimating the time needed for the solid-phase heating and that for the melting, the additional heat transfer rmechanism due to the thermionic emission front the particle surface is usually negligible since the surface temperatures of the particle heated in the plasma are, in general, compartively low during those heating steps. Thermionic emission assumes its effect only as the higher surface temperatures of the heated particle are involved (e.g., higher than 4000 K), while radiation loss shows its effects at much lower wall temperatures. As the plasma temperature is comparatively low, radiation heat loss may restrict the surface temperature of a particle to such a low value that the effect of thermionic emission on the overall heating time can he neglected and complete evaporation of refractor y metallic particles becomes impossible. The uncertainty in the calculation of the effect of thermionic emission is associated with the choice of the value of the effective work function for the particle material.     

Weighted estimates for bilinear square functions with non-smooth kernels and commutators

Under weaker conditions on the kernel functions,we discuss the boundedness of bilinear square functions associated with non-smooth kernels on the product of weighted Lebesgue spaces.Moreover,we investigate the weighted boundedness of the commutators of bilinear square functions(with symbols which are BMO functions and their weighted version,respectively)on the product of Lebesgue spaces.As an application,we deduce the corresponding boundedness of bilinear Marcinkiewicz integrals and bilinear Littlewood-Paley^-functions.     

Transference on Some Non-convolution Operators from Euclidean Spaces to Torus

The authors prove the certain de Leeuw type theorems on some non-convolution operators, and give some applications on certain known results.