A facile method to fabricate tough hydrogel with ultra-wide adjustable stiffness,stress, and fast recoverability

In this article, we report a synergistic strategy to develop dual physically cross-linked tough hydrogels via one-pot bulk copolymerization of N-vinyl-2-pyrrolidone, acrylic acid, and stearyl methylacrylate (SMA) without any adscititious surfactant. Due to synergic effects of hydrogen bonding and hydrophobic association, the resulted dual physically cross-linked hydrogels (DP Gel) with ultra-wide range adjustable Young's modulus (0.08–45.6 MPa), tensile stress (0.7–6.9 MPa), and toughness (3.3–23.1 MJ m⁻³). Stretching to 300%, DP Gel exhibited fast recoverability that remained ~95% of initial dissipated energy after resting in 60 °C for 3 min. Finally, scanning electron microscopy revealed that the microstructure of hydrogel changed from phase separation structure to micro phase separation as SMA added, which accounted for excellent performance of DP Gel. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1469–1474     

Theoretical study on electronic structure of (CNC)Fe_2N2 and its N2 elimination mechanism

The density function theory (DFT) is to elucidate the electronic structure of bis(dinitrogen) Fe(0) complex, (CNC)Fe_2N₂, and its N₂ elimination mechanism. (CNC)Fe_2N₂ has a low‐spin singlet (S = 0) ground state with a distorted square pyramidal structure. Fragment orbital interaction analysis yields total occupancy of π* orbitals (LUF₍₄₎O and LUF₍₄₎O−1) of apical N3 N4 is 0.188 while that of basal N1 N2 is 0.187 in ^S0(CNC)Fe_2N₂, suggesting nearly the same activation extent for both basal and apical N₂ ligands. The lowest‐lying triplet state T₁ (3‐A′) has a repulsive potential energy surface along the Fe N3 bong length by PBE functional, while a minimum on T₂ state (3‐A″) with higher energy is found by B3LYP functional. The nonadiabatic N₂ elimination mechanism of (CNC)Fe_2N₂ involves an S₀‐T₁ states crossing, which lowers the activation energy to 9.7 kcal/mol and produces high‐spin intermediate (CNC)Fe N₂. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

An online method combining a Gasbench II with continuous flow isotope ratio mass spectrometry to determine the content and isotopic compositions of minor amounts of carbonate in silicate rocks

An online method using continuous flow isotope ratio mass spectrometry (CF‐IRMS) interfaced with a Gasbench II device was established to analyze carbon and oxygen isotopic compositions and to estimate the content of minor amounts of carbonate in silicate rocks. The mixtures of standard materials and high‐purity quartz are firstly used to calibrate different quantities of carbonate in silicates. The results suggest that the accuracy and precision of the online analysis are both better than those obtained using an offline method. There is a positive correlation between the carbonate weight and the Mass44 ion beam intensity (or peak area). When the weight of carbonate in the mixtures is greater than 70 µg (equal to ～1800 mV Mass44 ion beam intensity), the δ¹³C and δ¹⁸O values of samples usually have accuracy and precision of ±0.1‰ and ±0.2‰ (1σ), respectively. If the weight is less than 70 µg, some limitations (e.g., not perfectly linear) are encountered that significantly reduce the accuracy and precision. The measured δ¹⁸O values are systematically lower than the true values by ?0.3 to ?0.7‰; the lower the carbonate content, the lower the measured δ¹⁸O value. For samples with lower carbonate content, the required phosphoric acid doses are higher and more oxygen isotope exchanges with the water in the phosphoric acid. To guarantee accurate results with high precision, multiple analyses of in‐house standards and an artificial MERCK sample with δ¹³C values from ?35.58 to 1.61‰ and δ¹⁸O from 6.04 to 18.96‰ were analyzed simultaneously with the unknown sample. This enables correction of the measured raw data for the natural sample based on multiple‐point normalization. The results indicate that the method can be successfully applied to a range of natural rocks. Copyright © 2010 John Wiley & Sons, Ltd.     

空间几何角度下看代入法求条件极值

通过具体实例,借助matlab作图,阐述了代入法求条件极值的几何含义和理论依据,指出了这种解法容易遗漏极值点的原因,并根据代入法的使用限制归纳了三种常见的代入形式,为学习者正确使用代入法提供参考.     

Syntheses and Crystal Structures of LnIII–CuI Coordination Polymers

Four three‐dimensional heterometallic coordination polymers, [Ln₂Cu₄I₃(IN)₇(H₂O)]_n ( 1 , 2 ) and [LnCu_3.5I₃(IN)_3.5(H₂O)₃]_n · nH₂O ( 3 , 4 ) [HIN = isonicotinic acid, Ln = Nd ( 1 ), Gd ( 2 ), La ( 3 ), Eu ( 4 )] were hydrothermally synthesized by using lanthanide oxides, isonicotinic acid, copper chloride, and potassium iodide. The different molar ratio of raw materials results in two distinct types of three‐dimensional frameworks of compounds 1 – 4 . The structure of compounds 1 and 2 are constructed by the layer modules of [Ln₂(IN)₇(H₂O)]_n^n– and Cu₄I₃ clusters, whereas that of compounds 3 and 4 are built by dimeric Ln₂(IN)₆(H₂O)₆ and layered polymeric [Cu₇I₆]_nⁿ⁺ units.     

Determination of pethidine in human plasma by LC–MS/MS

A sensitive and selective liquid chromatography–tandem mass spectrometry method for the determination of pethidine in human plasma was developed and validated over the concentration range of 4–2000 ng/mL. After addition of ketamine as internal standard, liquid–liquid extraction was used to produce a protein‐free extract. Chromatographic separation was achieved on a 100 × 2.1 mm, 5 µm particle, Allure^TM PFP propyl column, with 45:40:15 (v/v/v) acetonitrile–methanol–water containing 0.2% formic acid as mobile phase. The MS data acquisition was accomplished by multiple reactions monitoring mode with positive electrospray ionization interface. The lower limit of quantification was 4 ng/mL; for inter‐day and intra‐day tests, the precision (RSD) for the entire validation was less than 7%, and the accuracy was within 95.9–106.5%. The method is sensitive and simple, and was successfully applied to analysis of samples of clinical intoxication. Copyright © 2010 John Wiley & Sons, Ltd.     

环糊精在电化学中的应用

本文对环糊精在电化学中的应用进行了简要的介绍。     

Global existence and nonexistence for diffusive polytropic filtration equations with nonlinear boundary conditions

In this paper, we deal with the global existence and nonexistence of solutions to a diffusive polytropic filtration system with nonlinear boundary conditions. By constructing various kinds of sub- and super-solutions and using the basic properties of M-matrix, we give the necessary and sufficient conditions for global existence of nonnegative solutions, which extend the recent results of Li et al. (Z Angew Math Phys 60:284–298, 2009) and Wang et al. (Nonlinear Anal 71:2134–2140, 2009) to more general equations and simplify their proofs slightly.