Giant dielectric permittivity observed in Li and Ti doped NiO

A giant low-frequency dielectric constant ( epsilon 0 approximately 10(5)) near room temperature was observed in Li,Ti co-doped NiO ceramics. Unlike currently best-known high epsilon 0 ferroelectric-related materials, the doped oxide is a nonperovskite, lead-free, and nonferroelectric material. It is suggested that the giant dielectric constant response of the doped NiO could be enhanced by a grain boundary-layer mechanism as found in boundary-layer capacitors. In addition, there is about a one-hundred-fold drop in the dielectric constant at low temperature. This anomaly is attributed to a thermally excited relaxation process rather than a thermally driven phase transition, as for that yielding ferroelectrics.     

Boundary element monotone iteration scheme for semilinear elliptic partial differential equations, Part II: Quasimonotone iteration for coupled systems

Numerical solutions of semilinear systems of elliptic boundary value problems, whose nonlinearities are of quasimonotone nondecreasing, quasimonotone nonincreasing, or mixed quasimonotone types, are computed. At each step of the (quasi) monotone iteration, the solution is represented by a simple-layer potential plus a domain integral; the simple-layer density is then discretized by boundary elements. Because of the various combinations of Dirichlet, Neumann and Robin boundary conditions, there is an associated matrix problem, the norm of which must be estimated. From the analysis of such matrices, we formulate conditions which guarantee the monotone iteration a strict contraction staying within the close range of a given pair of subsolution and supersolution. Thereafter, boundary element error analysis can be carried out in a similar way as for the discretized problem. A concrete example of a monotone dissipative system on a 2D annular domain is also computed and illustrated.

     

Sustainable and Green Synthesis of Waste-Biomass-Derived Carbon Dots for Parallel and Semi-Quantitative Visual Detection of Cr(VI) and Fe3+

Carbon dot (CD)-based multi-mode sensing has drawn much attention owing to its wider application range and higher availability compared with single-mode sensing. Herein, a simple and green methodology to construct a CD-based dual-mode fluorescent sensor from the waste biomass of flowers of wintersweet (FW-CDs) for parallel and semi-quantitative visual detection of Cr(VI) and Fe³⁺ was firstly reported. The FW-CD fluorescent probe had a high sensitivity to Cr(VI) and Fe³⁺ with wide ranges of linearity from 0.1 to 60 µM and 0.05 to 100 µM along with low detection limits (LOD) of 0.07 µM and 0.15 µM, respectively. Accordingly, the FW-CD-based dual-mode sensor had an excellent parallel sensing capacity toward Cr(VI) and Fe³⁺ with high selectivity and strong anti-interference capability by co-using dual-functional integration and dual-masking strategies. The developed parallel sensing platform was successfully applied to Cr(VI) and Fe³⁺ quantitative detection in real samples with high precision and good recovery. More importantly, a novel FW-CD-based fluorescent hydrogel sensor was fabricated and first applied in the parallel and semi-quantitative visual detection of Cr(VI) and ferrous ions in industrial effluent and iron supplements, further demonstrating the significant advantage of parallel and visual sensing strategies.     

Characterization of Volatile Profiles and Correlated Contributing Compounds in Pan-Fried Steaks from Different Chinese Yellow Cattle Breeds through GC-Q-Orbitrap,E-Nose,and Sensory Evaluation

This study focused on characterizing the volatile profiles and contributing compounds in pan-fried steaks from different Chinese yellow cattle breeds. The volatile organic compounds (VOCs) of six Chinese yellow cattle breeds (bohai, jiaxian, yiling, wenshan, xinjiang, and pingliang) were analyzed by GC-Q-Orbitrap spectrometry and electronic nose (E-nose). Multivariate statistical analysis was performed to identify the differences in VOCs profiles among breeds. The relationship between odor-active volatiles and sensory evaluation was analyzed by partial least square regression (PLSR) to identify contributing volatiles in pan-fried steaks of Chinese yellow cattle. The results showed that samples were divided into two groups, and 18 VOCs were selected as potential markers for the differentiation of the two groups by GC-Q-Orbitrap combined multivariate statistical analysis. YL and WS were in one group comprising mainly aliphatic compounds, while the rest were in the other group with more cyclic compounds. Steaks from different breeds were better differentiated by GC-Q-Orbitrap in combination with chemometrics than by E-nose. Six highly predictive compounds were selected, including 3-methyl-butanal, benzeneacetaldehyde, 2-ethyl-6-methyl-pyrazine, 2-acetylpyrrole, 2-acetylthiazole, and 2-acetyl-2-thiazoline. Sensory recombination difference and preference testing revealed that the addition of highly predictive compounds induced a perceptible difference to panelists. This study provides valuable data to characterize and discriminate the flavor profiles in pan-fried steaks of Chinese yellow cattle.     

控压钻井重力置换与溢流气侵判断准则分析

考虑重力置换的恒定性、气侵的可变性,提出了重力置换与溢流气侵的判断三准则,实现了计算机自动判断气体来源。借助计算机编程对准则求解,并将判断准则应用于某微流量控压钻井的溢流气侵和重力置换判断。结果表明:重力置换发生后,一定量的置换气体侵入环空,气体的侵入量主要受岩层渗透率、钻井液-岩层接触面积的影响,而溢流气侵发生后,气体的侵入量主要受地层欠压差影响;为达到衡压钻井目的,溢流气侵发生后不但要抑制气体滑脱产生的压降,更要平衡地层欠压差,而重力置换只需抑制气体滑脱产生的压降;溢流气侵发生后,环空中流体的流动先由0气流转换为混合流,经回压控制后,再由混合流转换为0气流,重力置换发生后,环空中流体的流动由0气流转换为混合流。     

Fe3O4/poly (acrylic acid) nanoparticles as modifiers for improving rheological and filtration properties of water-based drilling fluids

Drilling fluid is a vital element and is often regarded as the “blood” in the oil industry. Although traditional oil-based drilling fluids have advantages in some harsh cases, the high cost and environmental pollution faced with them limit its application. Water-based drilling fluids (WBDFs) with environmental friendly, low cost, and high performance are important for drilling engineering to solve the problems of low efficiency and wellbore instability caused by poor rheological properties and large filtration loss in drilling operations. In this paper, Fe₃O₄ nanoparticles modified by poly (acrylic acid) (PAA) through 3-(trimethoxysilyl) proryl methacrylate (TMSPMA) were introduced into WBDFs for enhancing their rheological and plugging performance. Rheological tests indicated that the consistency coefficient (K) of the Fe₃O₄/PAA nanoparticles/WBDFs decreased at a higher concentration. Incorporated nanoparticles with a concentration of 0.05?wt %, the WBDFs will exhibit good shear-thinning behavior. The results showed that the best performance for Fe₃O₄/PAA nanoparticles being as a filtration additive in WBDFs was achieved at concentration as low as 0.1?wt %. These results demonstrated that Fe₃O₄/PAA nanoparticles are effective additives for WBDFs.     

Determination of the interaction using FTIR within the components of GPE based on the synthesized grafted polymer

An oxyethylene chain (–CH₂–CH₂–O–) grafted polymer (P(MMA–MAh)–PEGME) was synthesized by reacting poly(ethylene glycol) monomethyl ether (PEGME) with the copolymer of poly(methyl metacrylate–maleic anhydride) (P(MMA–MAh)) and endcapping the residual carboxylic acid with methanol. Rectorite modified with dodecyl benzyl dimethyl ammonium chloride (OREC) was used as a filler additive to modify gel polymer electrolytes (GPE) that consisted of P(MMA–MAh)–PEGME used as polymer matrix, propylene carbonate (PC) as plasticizer and LiClO₄ as lithium ion producer. Characterization of interaction of the polar group of C=O or C–O–C in PC and grafted polymer with Li⁺ and OH group on OREC surface has been thoroughly examined using Fourier transform infrared (FTIR), respectively. The quantitative analysis of FTIR shows that the absorptivity coefficients (a) of polymer/LiClO₄, PC/LiClO₄, PC/OREC and polymer/OREC are 0.705, 0.113, 0.430 and 0.500, respectively, which means that the Li⁺ or OH bonded polar group of C=O and C–O–C is more sensitive than free C=O and C–O–C in FTIR spectra. The limited values of bonded C=O and C–O–C equivalent fraction of polymer/LiClO₄, PC/LiClO₄, PC/OREC and polymer/OREC are 33%, 94%, 60% and 22%, respectively, which implies that the interaction within the components is reversible and the intensity of interaction is ordered as PC/LiClO₄, PC/OREC, polymer/OREC and polymer/LiClO₄.     

Cure characteristics and properties of NBR composites filled with co‐precipitates of black liquor and montmorillonite

Acrylonitrile‐butadiene rubber (NBR) composites filled with co‐precipitates of black liquor and montmorillonite (CLM) were prepared by mechanical mixing on a two‐roll mill. The cure characteristics, mechanical properties, thermal properties, and thermo‐oxidative aging properties of NBR/CLM composites were evaluated. Scanning electron microscopy and transmission electron microscopy showed that the filler particles were well dispersed in the NBR/CLM composites. The scorch time and optimum cure time increase with increasing filler loading. A remarkable enhancement in tensile strength, elongation at break, 300% modulus, and shore “A” hardness was also observed. When the loading of CLM was 40 parts per hundred rubbers, it showed about seven times increase in tensile strength, about 1.8 times increase in elongation at break, about three times increase in 300% modulus, and about 1.3 times increase in shore A hardness, respectively, as compared with those of pure cured NBR. Thermal properties and thermal oxidative aging properties, in general, were also improved with loading of this novel filler. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of a green [60]fullerene derivative through cage-opening reactions

Open-cage derivative C(60)(O)(4)(OH)(2)(NC(6)H(4)(t)Bu)(2) reacts with ICl to form a Baeyer-Villiger type product, which yields an intense green product upon treatment with HI.     

Adsorption characteristics of thionine on gold nanoparticles

Adsorption characteristics of thionine on gold nanoparticles have been studied by using UV-vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), cyclic voltammetry and Fourier transform infrared spectroscopy. With the increasing concentration of gold nanoparticles, the absorption peak intensity of H-type dimers of thionine increases continuously, whereas that of monomers of thionine first increases and then decreases. The addition of gold nanoparticles makes the equilibrium between the monomer and H-type dimer forms of thionine move toward the dimer forms. Furthermore, the adsorption behavior of thionine on gold nanoparticles is also influenced by temperature. TEM images show that the addition of thionine results in an obvious aggregation, and further support the absorption spectral results. The fluorescence intensity of adsorbed thionine is quenched by gold nanoparticles due to the electronic interaction between thionine molecules and gold nanoparticles. Cyclic voltammetric and infrared spectroscopic studies show that the nitrogen atoms of both of the NH2 moieties of thionine strongly bind to the gold nanoparticle surfaces through the electrostatic interaction of thionine with gold nanoparticles. For 15-20 nm particles, the number of adsorbed thionine molecules per gold nanoparticle is about 7.66 x 10(4). Thionine molecules can not only bind to a particle to form a compact monolayer via both of the NH2 moieties, but they can also bind to two particles via their two NH(2) moieties, respectively.