Study of 1-3-2 type piezoelectric composite transducer array

Based on a new structure of precise location and decoupling between the transducer elements, high frequency underwater transmission transducer arrays with 4 elements and 8 elements serried uniform linear array were studied, using novel 1-3-2 type piezoelectric composite as the sensing material. There are ceramic framework supports in the transverse and longitudinal directions in 1-3-2 type piezoelectric composite structure; the transducer is free from the influence of outside mechanical impact and the environment temperature change. Transducer and array samples have been designed, fabricated and measured. The resonant frequency is 150 kHz, resonant transmission response greater than 160 dB, and bandwidth is from 140 kHz to 160 kHz. The results indicate that, the transducer array has wide bandwidth, high sensitivity, stabile performance, and good coherence.     

Determination of metformin based on amplification of its voltammetric response by a combination of molecular wire and carbon nanotubes

Molecular wires containing copper(II) (CuMW), in the form of the coordination polymer (Cu(II)₄(bpp)₄(maa)₈(H₂O)₂).2H₂O (bpp=1,3-bis(4-pyridyl)propane, maa=2-methylacrylic acid), and multiwalled carbon nanotubes (CNT) have been combined to prepare a paste electrode (CuMW/CNT/PE). The voltammetric response of the CuMW/CNT/PE to metformin (MET) was significantly greater than that of electrodes prepared from other materials, because of both the surface effect of CuMW and CNT and coordination of MET with the Cu(II) ion in the CuMW. A novel voltammetric method for determination of MET is proposed. In pH 7.2 Britton–Robinson buffer, using single sweep voltammetry, the second-order derivative peak current for oxidation of MET at 0.97 V (relative to SCE) increased linearly with MET concentration in the range 9.0 × 10⁻⁷–5.0 × 10⁻⁵ mol L⁻¹ and the detection limit was 6.5 × 10⁻⁷ mol L⁻¹. Figure When a combination of molecular wires containing copper(II) (CuMW) and multiwalled carbon nanotubes (CNT) was used to prepare a paste electrode (CuMW/CNT/PE) the voltammetric response to metformin (curve c) was significantly higher than that at a carbon/PE (curve a) or a CNT/PE (curve b), because of the amplification effect of CNT and CuMW. A novel voltammetric method is proposed for determination of MET     

An investigation of the self-assembly of neutral, interlaced, triple-stranded molecular braids

The synthesis and structures of six compounds prepared in two different systems have been explored with the purpose of isolating coordination polymers with interlaced triple-stranded molecular braid architectures. The dinuclear paddle-wheel units of [Cu(2)(maa)(4)2 H(2)O] can be rationally tuned to form three classes of isomorphous compounds, namely [Cu(2)(maa)(4)(bpp)] (1) (bpp=1,3-bis(4-pyridyl)propane, Hmaa=2-methylacrylic acid), [Cu(3)(maa)(6)(bpp)(2)] (2), and[Cu(4)(maa)(8)(bpp)(4)(H(2)O)(2)]2 H(2)O (3), with a bridging bpp ligand, at controlled ligand-to-metal molar ratios, and lead to three coordination polymers having similar one-dimensional characteristics but different mono- and dinuclear nodes. Compound 1, with a bpp:[Cu(2)(maa)(4)2 H(2)O] stoichiometry of 1:1, contains a zigzag chain containing dinuclear nodes, whereas polymer 2, with a bpp:[Cu(2)(maa)(4)2 H(2)O] stoichiometry of 1.5:1, also adopts the topology of a zigzag chain but with both mono- and dinuclear nodes. Compound 3, with a bpp:[Cu(2)(maa)(4)2 H(2)O] stoichiometry of 2:1, contains a neutral, interlaced, triple-stranded molecular braid, which is interwoven by three single-stranded meso-helical chains that contain only a mononuclear node. With the three aromatic chelating terminal ligands 2,2':6',2'-terpyridine (tpy), 1,10-phenanthroline (phen), and di(2-pyridyl)amine (dpa) we have also prepared three neutral complexes containing the linear, rigid bridging ligand biphenyl-4,4'-dicarboxylate (bpdc), namely [Cd(bpdc)(tpy)]H(2)O (4), [Cu(bpdc)(phen)(2)]4.25 H(2)O (5), and [Cu(bpdc)(dpa)] (6). An infinite meso-helix is formed initially in 4, and then three of these chains assemble into a triple-stranded braid similar to that of 3. Complexes 5 and 6 have a mononuclear and a looped dinuclear structure, respectively. Compounds 3 and 4 are unusual examples of triple-stranded molecular braid coordination frameworks based on different types of co-ligands.     

手性1-芳基-2-(1H-1,2,4-三唑-1-基)乙醇衍生物的合成与生物活性

取代苯乙烯1与KHSO₅在手性催化剂2存在的条件下反应, 生成1-芳基环氧化物3, 3与1H-1,2,4-三唑在固体碳酸钾催化下作用, 得到手性的1-芳基-2-(1H-1,2,4-三唑-1-基)乙醇衍生物4. 部分4对甾醇14α-脱甲基化酶表现出强结合作用.     

A new monosaccharide from Swertia punicea Hemsl

A new compound named 1-hydrate,3-deoxy-α-D-tagatofuranose was isolated from Swertia punicea Hemsl.The structure of compound was determined by 1D and 2D NMR,HRESIMS techniques.     

On the nonlinear wave equation with the mixed nonhomogeneous conditions: Linear approximation and asymptotic expansion of solutions

In this paper, we consider the following nonlinear wave equation

(1)

where , , μ, f, g are given functions. To problem (1), we associate a linear recursive scheme for which the existence of a local and unique weak solution is proved by applying the Faedo–Galerkin method and the weak compact method. In the case of , , μ(z)≥μ₀>0, μ₁(z)≥0, for all , and , , , a weak solution u_ε1,ε2(x,t) having an asymptotic expansion of order N+1 in two small parameters ε₁, ε₂ is established for the following equation associated to (1)_2,3:

(2)

     

Preparation of high temperature resistance polybenzimidazole resin

Polybenzimidazole’s (PBI) was synthesized from 3,3′-diaminobenzidine and adipic acid by melting copolycondensation. Its thermal properties have been studied The molecular structure and thermal stability of the resulting polymers were characterized by means of FTIR, TGA and DSC. The results indicate that the melting temperature of the PBI is higher than 400°C and the polymer possesses excellent thermal stability. The onset decomposition temperature was determined to be 516°C, and the highest decomposition temperature reaches 536°C. __________ Translated from Journal of Xihua University (Natural Science Edition), 2008, 27 (1) (in Chinese)     

QSPR study for the prediction of half-wave potentials of benzoxazines by heuristic method and radial basis function neural network

The half-wave potential (E_1/2) is an important electrochemical property of organic compounds. In this work, a quantitative structure-property relationship (QSPR) analysis has been conducted on the half-wave reduction potential (E_1/2) of 40 substituted benzoxazines by means of both a heuristic method (HM) and a non-linear radial basis function neural network (RBFNN) modeling method. The statistical parameters provided by the HM model (R² =0.946; F=152.576; RMSCV=0.0141) and the RBFNN model (R²=0.982; F=1034.171 and RMS =0.0209) indicated satisfactory stability and predictive ability. The obtained models showed that benzoxazines with larger Min valency of a S atom (MVSA), lower Relative number of H atom (RNHA) and Min n-n repulsion for a C-H bond (MnnRCHB) and Minimal Electrophilic Reactivity Index for a C atom (MERICA) can be more easily reduced. This QSPR approach can contribute to a better understanding of structural factors of the organic compounds that contribute to the E_1/2, and can be useful in predicting the E_1/2 of other compounds.      

Boundary control of non-well-posed elliptic equations with nonlinear Neumann boundary conditions

In this paper, we consider a boundary control problem governed by a class of non-well-posed elliptic equations with nonlinear Neumann boundary conditions. First, the existence of optimal pairs is proved. Then by considering a well-posed penalization problem and taking limit in the optimality system for penalization problem, we obtain the necessary optimality conditions for optimal pairs of initial control problem.     

Mercaptopropionic acid capped CdSe/ZnS quantum dots as fluorescence probe for lead(II)

MPA stabilized CdSe/ZnS NCs was applied as a fluorescent probe for the sensitive detection of Pb²⁺ in water. The microreaction was demonstrated as a facile method for the reproducible synthesis of CdSe/ZnS NCs with a high quantum yield. The good stability of CdSe/ZnS NCs was proved by the significant maintaining of photoluminescent (PL) after the ligand exchange with MPA, and was further demonstrated by the excellent PL property in water solution with various pH values. The cation exchange of Zn with Pb led to the linear quenching of PL with the concentration of Pb²⁺, which provided as an opportunity to apply MPA stabilized CdSe/ZnS NCs as fluorescent probes for Pb²⁺. A facile method by adjustment of QDs concentration was demonstrated as a suitable way to approach different detection limits. The detection limits of 0.03 and 3.3 μM were achieved by setting QDs solutions with the absorbance of the first exciton peak as 0.05 and 0.15, respectively.