Fe3O4 nanoparticles coated with polyhedral oligomeric silsesquioxanes and β‐cyclodextrin for magnetic solid‐phase extraction of carbaryl and carbofuran

In this study, porous sandwich structure Fe₃O₄ nanoparticles coated by polyhedral oligomeric silsesquioxanes and β‐cyclodextrin were prepared by surface polymerization and were used as the magnetic solid phase extraction adsorbent for the extraction and determination of carbaryl and carbofuran. The Fe₃O₄ nanoparticles coated with polyhedral oligomeric silsesquioxanes and β‐cyclodextrin were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, and scanning electron microscopy. After optimizing the extraction conditions, a method that combined magnetic solid phase extraction with high‐performance liquid chromatography was developed for the determination of carbaryl and carbofuran in apple. The method exhibited a good linearity in the range of 2–400 μg/kg for carbaryl and carbofuran (R² = 0.9995), respectively. The limits of detection were 0.5 μg/kg of carbaryl and 0.7 μg/kg for carbofuran in apple, respectively. Extraction recoveries ranged from 94.2 to 103.1% with the preconcentration factor of 300 and the relative standard deviations were less than 5.9%. These results indicated that the method combined magnetic solid phase extraction with high‐performance liquid chromatography and was promising for the determination of carbaryl and carbofuran at trace amounts.     

Synthesis and biological evaluation of novel isopropanolamine derivatives as non-peptide human immunodeficiency virus protease inhibitors

Novel potential human immunodeficiency virus (HIV) protease inhibitors were designed by a combination of nelfinavir and amprenavir motifs. The designed compounds were prepared by a facile synthetic route and their stereochemistry was further confirmed by a stereospecific synthesis from commercially available (S)-2-oxiranylmethyl m-nitrobenzenesulfonate. All compounds were tested for their ability in inhibiting HIV type 1 protease activity with the published method of reference 19. Derivatives 1a--u exhibited moderate to significant inhibitory activities in preliminary bioassay. The best compound 1a has IC50 value of 0.02 microM, comparable to that of amprenavir. A docking study on compounds 1a--u was performed using the published X-ray crystal structure of HIV type 1 protease, all compounds bound to the HIV type 1 protease in an extended conformation and the scaffoldings of the binding conformations could be aligned quite well. Comparative molecular field analysis (CoMFA) study was performed to explore the specific contributions of electrostatic and steric effects in the binding of these new compounds to HIV type 1 protease and a predictive CoMFA model was built with thirteen compounds as training set. Test analysis of other five compounds as test set demonstrated that the CoMFA model has strong predictive ability to this series of compounds. It will be very useful to further optimize the designed inhibitors.     

Identification of γ-AApeptides with potent and broad-spectrum antimicrobial activity

We report the identification of a new class of antimicrobial peptidomimetics-γ-AApeptides with potent and broad-spectrum activity, including clinically-relevant strains that are unresponsive to most antibiotics. They are also not prone to select for drug-resistance.     

Synthesis of novel functional polycyclic chromones through Michael addition and double cyclizations

A base-promoted, microwave-assisted one-pot tandem reaction from simple 3-(1-alkynyl)chromones with 2-halobenzylic nitriles (esters or amides) for the synthesis of novel functional polycyclic chromenones has been developed. This tandem process involves multiple reactions, such as Michael addition and double cyclizations without a transition metal catalyst.     

Domino reaction to functionalized 2-hydroxybenzophenones from electron-deficient chromones and 1,3-dicarbonyl compounds

A base-promoted one-pot tandem reaction sequence has been developed to transform electron-deficient chromone-fused dienes 1 and 1,3-dicarbonyl compounds 2 to functionalized 2-hydroxybenzophenones 3 under mild conditions. This domino process, which involves multiple reactions, including Michael addition/cyclization/elimination, serves as an efficient, economic, and eco-friendly method for the construction of diversified 2-hydroxybenzophenone scaffolds without a transition-metal catalyst and inert atmosphere.     

In vivo Visualization of the Process of Hg2+ Bioaccumulation in Water Flea Daphnia carinata by a Novel Aggregation‐Induced Emission Fluorogen

This paper employs a specially designed aggregation‐induced emission fluorogen (AIEgen) to in vivo visualize the process of Hg²⁺ bioaccumulation in a common species of freshwater zooplankton Daphnia carinata (D. carinata) by two methods, direct Hg²⁺ absorption and ingestion of Hg²⁺ contaminated food. We analysed the relevance between photoluminescence (PL, I₅₉₅/I₄₈₀) ratios and Hg²⁺ (C_Hg2+) and developed the master curve for Hg²⁺ determination based on measuring the PL intensity of the solution. Meanwhile, fluorescent image analysis showed that the major recipient organs of Hg²⁺ in D. carinata were the compound eyes and carapace, followed by the intestine and shell gland, but not the brain or heart. The response of D. carinata to Hg²⁺ via uptake from surrounding water differed distinctly from that through food intake of the algae (Euglena gracilis) contaminated by mercury. When Hg²⁺ was encapsulated by algae membrane, no fluorescence was detected, and the carapace morphology remained intact after ingesting algae for 80 min, in contrast to the rapid carapace deformation by direct Hg²⁺ absorption. The D. carinata showed higher mortality by direct Hg²⁺ immersion than via food ingestion. The reason for the high mortality after Hg²⁺ immersion was possibly due to carapace deformity after chemical reaction between chitin and mercury, but the biochemical pathway leading to morality needs further study.     

最小二乘辨识的强一致性

系统辨识中参数估计的一致性问题已有很多研究。[1,2]研究了最小二乘辨识的弱一致性问题。[3,4]对离散时间系统、[5]对连续时间系统提出了保证最小二乘估计收敛且强一致的条件。但其中包含了噪声的条件协方差阵对(t,ω)一致有界。[6,7]把递推算法的收敛性、强一致性和某一常微分方程的稳定性建立了联系,这一类定理所讨论的并不是某一种特定的算法,而是一类算法。但[6]中所要求的条件很多,有的不容易验证,[7]中处理方法较[6]简单。但所要求的条件仍很强,特别是事先要求递推过程一致有界及常返某一紧集,这样一个不太合理的要求。     

Novel proton-type ionic liquid doped polyaniline for the headspace solid-phase microextraction of amines

A novel proton-type ionic liquid doped polyaniline (HIL-doped PANI) coating was presented, which was prepared on a stainless steel wire by electrodeposition in an aqueous solution containing aniline and 1-sulfobutyl-3-methylimidazolium hydrosulfate. The HIL-doped PANI coating showed granular nanostructure and had large specific surface. When it was applied to the headspace solid-phase microextraction of several amines (i.e., aniline, N-methylaniline, 3-methylaniline, 2-chloroaniline and 3-chloroaniline), it showed high extraction efficiency. The enrichment factors were 191.8–343.9 for different amines, much higher than those of common PANI and commercial polydimethylsiloxane/divinylbenzene coatings. Coupled with gas chromatographic analysis, the linear ranges were 0.097–100 μg/L with correlation coefficients above 0.9942, and the detection limits were 0.012–0.048 μg/L (S/N = 3) for different amines. The relative standard deviations (RSD) were smaller than 8.1% for five successive measurements with single fiber and the fiber-to-fiber RSDs were 8.6–13.8% (n = 5) for these amines. The proposed method was successfully applied to the extraction and determination of amines in organic waste water samples, and the recoveries were 78.3–112.8% for different analytes.     

One-pot synthesis of furocoumarins through cascade addition-cyclization-oxidation

A novel one-pot cascade addition-cyclization-oxidation for the regioselective synthesis of furo[3,2-c]coumarins has been developed; the reaction is mild and easily handled without the necessity for dry solvents and inert atmosphere.     

Vortex fluidic induced mass transfer across immiscible phases

Mixing immiscible liquids typically requires the use of auxiliary substances including phase transfer catalysts, microgels, surfactants, complex polymers and nano-particles and/or micromixers. Centrifugally separated immiscible liquids of different densities in a 45° tilted rotating tube offer scope for avoiding their use. Micron to submicron size topological flow regimes in the thin films induce high inter-phase mass transfer depending on the nature of the two liquids. A hemispherical base tube creates a Coriolis force as a ‘spinning top’ (ST) topological fluid flow in the less dense liquid which penetrates the denser layer of liquid, delivering liquid from the upper layer through the lower layer to the surface of the tube with the thickness of the layers determined using neutron imaging. Similarly, double helical (DH) topological flow in the less dense liquid, arising from Faraday wave eddy currents twisted by Coriolis forces, impact through the less dense liquid onto the surface of the tube. The lateral dimensions of these topological flows have been determined using ‘molecular drilling’ impacting on a thin layer of polysulfone on the surface of the tube and self-assembly of nanoparticles at the interface of the two liquids. At high rotation speeds, DH flow also occurs in the denser layer, with a critical rotational speed reached resulting in rapid phase demixing of preformed emulsions of two immiscible liquids. ST flow is perturbed relative to double helical flow by changing the shape of the base of the tube while maintaining high mass transfer between phases as demonstrated by circumventing the need for phase transfer catalysts. The findings presented here have implications for overcoming mass transfer limitations at interfaces of liquids, and provide new methods for extractions and separation science, and avoiding the formation of emulsions.

Micron to submicron size Coriolis and Faraday wave induced high shear topological flow regimes in 45° titled rapidly rotating tubes result in high inter-phase mass transfer of immiscible liquids and spontaneous demixing.