ADAPTIVE FINITE ELEMENT APPROXIMATION FOR A CLASS OF PARAMETER ESTIMATION PROBLEMS

In this paper, we study adaptive finite element discretisation schemes for a class of parameter estimation problem. We propose to efficient algorithms for the estimation problem use adaptive multi-meshes in developing We derive equivalent a posteriori error estimators for both the state and the control approximation, which particularly suit an adaptive multi-mesh finite element scheme. The error estimators are then implemented and tested with promising numerical results.     

Characteristics of ring type traveling wave ultrasonic motor in vacuum

The characteristics of ultrasonic motor strongly depend on the properties of stator/rotor contact interface which are affected by ambient environment. With the developed apparatus, load properties of two ring type traveling wave ultrasonic motors in atmosphere, low vacuum and high vacuum were studied, respectively. Wear of friction material, variations of vacuum degree and the temperature of motor during the experiment were also measured. The results show that load properties of motor A in vacuum were poorer than those in atmosphere, when load torque M_f was less than 0.55 N m. Compared to motor A, load properties of motor B were affected a little by environmental pressure. Wear of friction material in vacuum was more severe than wear in atmosphere. The temperature of motor in vacuum rose more quickly than it in atmosphere and had not reached equilibrium in 2 h experiment. However, the temperature of motor in atmosphere had reached equilibrium in about forth minutes. Furthermore, outgas was also observed during experiment under vacuum conditions.     

Global superconvergence for Maxwell's equations

In this paper, the global superconvergence is analysed on two schemes (a mixed finite element scheme and a finite element scheme) for Maxwell's equations in . Such a supercovergence analysis is achieved by means of the technique of integral identity (which has been used in the supercovergence analysis for many other equations and schemes) on a rectangular mesh, and then are generalized into more general domains and problems with the variable coefficients. Besides being more direct, our analysis generalizes the results of Monk.

     

Virus-like supramolecular assemblies formed by cooperation of base pairing interaction and peptidic association

A peptide nucleic acid(PNA)-peptide conjugated molecule, T′_3(AKAE)_2, was designed to have both a PNA segment for oligonucleotide binding and an ionic self-complementary peptide sequence for self-association. T′_3(AKAE)_2 could co-assemble with oligoadenines(d(A)_x) to form virus-like supramolecular structures whose morphology showed dependence on the chain length and rigidity of the d(A)_x molecules. Smaller nanospheres with diameters of 13.0±2.0 nm were produced in the case of d(A)_6. Wormlike aggregates with lengths of 20–50 nm and diameters of 15.0±2.5 nm were found in the cases of d(A)_(12), d(A)_(18), d(A)_(24) and d(A)_(30). And larger spherical aggregates with diameters of 18±5 nm came into presence in the cases of d(A)_(36) and d(A)_(42). These nanostructures were suggested to be formed under a cooperative effect of base pair recognition and peptidic association. The study provides insights into the programmed assembly of a multi-components system as well as control of the size and shape of the co-assembled structures, which is of great significance in developing gene/drug delivery systems.     

Electrochemical detection of DNA hybridization using methylene blue and electro-deposited zirconia thin films on gold electrodes

A novel electrochemical DNA biosensor based on methylene blue (MB) and zirconia (ZrO₂) thin films modified gold electrode for DNA hybridization detection is presented. Zirconia thin films were electrodynamically deposited onto the bare gold electrode in an aqueous electrolyte of ZrOCl₂ and KCl by cycling the potential between −1.1 and +0.7 V (versus Ag/AgCl) at a scan rate of 20 mV s⁻¹. Oligonucleotide probes with phosphate group at the 5′ end were attached onto the zirconia thin films because zirconia is affinity for phosphoric group. The surface density of the immobilized DNA molecules at the zirconia interface was investigated by fluorescence spectroscopy method. Hybridization was induced by exposure of the ssDNA-containing Au electrode to complementary ssDNA in solution. The decreases in the peak currents of MB, an electroactive label, were observed upon hybridization of probe with the target. The cathodic peak current (i_p) of MB after hybridization with the target DNA was linearly related to the logarithmic value of the target DNA concentration ranging from 2.25×10⁻¹⁰ to 2.25×10⁻⁸ mol l⁻¹. A detection limit of 1.0×10⁻¹⁰ mol l⁻¹ of oligonucleotides can be estimated.     

The Crucial Role of Chlorinated Thiophene Orientation in Conjugated Polymers for Photovoltaic Devices

Chlorinated conjugated polymers not only show great potential for the realization of highly efficient polymer solar cells (PSCs) but also have simple and high‐yield synthetic routes and low‐cost raw materials available for their preparation. However, the study of the structure–property relationship of chlorinated polymers is lagging. Now two chlorinated conjugated polymers, PCl(3)BDB‐T and PCl(4)BDB‐T are investigated. When the polymers were used to fabricate PSCs with the nonfullerene acceptor (IT‐4F), surprisingly, the PCl(3)BDB‐T:IT‐4F‐based device exhibited a negligible power conversion efficiency (PCE) of 0.18 %, while the PCl(4)BDB‐T:IT‐4F‐based device showed an outstanding PCE of 12.33 %. These results provide new insight for the rational design and synthesis of novel chlorinated polymer donors for further improving the photovoltaic efficiencies of PSCs.     

Solid-phase extraction of aflatoxins using a nanosorbent consisting of a magnetized nanoporous carbon core coated with a molecularly imprinted polymer

A core consisting of nanoporous carbon (MNPC) and magnetized with Co₃O₄ was coated with a molecularly imprinted polymer (MIP) by atom transfer radical precipitation polymerization. Ethyl 3-coumarincarboxylate was used as a pseudo-template to give a MIP that has a fairly specific recognition capability for aflatoxins. Batch rebinding studies were carried out to determine the specific adsorption equilibrium and specific recognition. Extraction is achieved in a single step by mixing and vortexing the sample extract with the Co-MNPC@MIP. The loaded nanosorbent was then magnetically separated and eluted with acetonitrile/water (6/4, v/v). The aflatoxins were then quantified by HPLC. Under optimal conditions, the detection limits for aflatoxins typically are 0.05–0.07 ng mL^?1, recoveries from spiked corn are found to be 75.1 to 99.4%, and relative standard deviations range from 1.7 to 5.1 (n =?6).

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Graphical abstract Poly(methacrylic acid) was imprinted with the pseudo-template ethyl 3-coumarincarboxylate by atom transfer radical precipitation polymerization on the surface of cobalt-derived magnetic nanoporous carbon (Co-MNPC). This nanosorbent was used for the magnetic solid phase extraction of aflatoxins, followed by HPLC analysis.

     

Synthesis of cobalt-based magnetic nanoporous carbon core-shell molecularly imprinted polymers for the solid-phase extraction of phthalate plasticizers in edible oil

Analytical and Bioanalytical Chemistry - In this work, cobalt magnetic nanoporous carbon (Co-MNPC) is employed as an alternative to intensively used Fe3O4 cores for the preparation of magnetic...     

Direct enrichment of phenols in lake and sea water by stir bar sorptive extraction based on poly (vinylpyridine-ethylene dimethacrylate) monolithic material and liquid chromatographic analysis

A poly (vinylpyridine-ethylene dimethacrylate) monolithic material was synthesized and selected as stir bar sorptive extraction (SBSE) medium. The influences of polymerization conditions on the extraction efficiency were investigated using phenol and p-nitrophenol as target analytes. Based on this, six strongly polar phenols in water were directly concentrated by the new SBSE and determined with high performance liquid chromatography equipped with diode array detector. To achieve the optimum extraction performance, several main parameters, including extraction and desorption time, pH value and contents of inorganic salt in the sample matrix were investigated. The method showed good linearity and acceptable recoveries, as well as advantages such as sensitivity, simplicity, low cost and high feasibility. The proposed method was successfully applied to the determination of phenolic compounds in lake and sea waters.     

Promotion effect of nickel for Cu–Ni/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts in the transfer dehydrogenation of primary aliphatic alcohols

Cu–Ni/γ-Al₂O₃ bimetallic catalysts were developed for anaerobic dehydrogenation of non-activated primary aliphatic alcohols to aldehydes. Systematic investigation about the promotion effect of nickel on the catalytic performance was carried out. Hydrogenation of C=C bond rather than C=O bond, was significantly improved over Cu–Ni/γ-Al₂O₃ catalyst by introducing nickel, which interprets the good conversion of primary aliphatic alcohols. This work would contribute to design new catalysts for dehydrogenation of primary aliphatic alcohols.