Resettable fluorescence logic gate based on calcein/layered double hydroxide ultrathin films

A fluorescent logic gate was fabricated based on calcein/layered double hydroxide ultrathin films (UTFs) via alternate assembly technique, which exhibits high stability, reversibility, and resettability. The logic gate was manipulated by utilizing pH value, Hg(2+) and Cl(-) ion as inputs, and the fluorescence emission of the (calcein/LDH)(16) UTF as output, serving as a three-input logic gate that combines the YES and INHIBIT operation.     

Synthesis,crystal structures,and catalytic activities of palladium imidazole complexes formed by 2-hydroxyethyl group cleavage

N-4,6-dimethyl-2-pyrimidinylimidazole 1 and its hydroxyethyl derivative 1-(2-hydroxyethyl)-3-(4,6-dimethyl-2-pyrimidinyl)imidazolium chloride 2 have been synthesized and characterized. The attempted synthesis of bis(N-heterocyclic carbene)palladium complexes via the direct reaction of 2 with Pd(OAc)₂ results in the unexpected formation of a bis(N-arylimidazole) palladium complex 3. Additionally, the analogous bis(N-methylimidazole) palladium complex 4 has also been synthesized by the above method. Compounds 1–4 were characterized by elemental analysis, IR, and ¹H NMR. Additionally, their crystal structures have been determined by X-ray diffraction. Complexes 3 and 4 were found to be efficient catalysts for the Suzuki reaction.     

Resonant cavity enhanced (RCE) photodetectors with flat-top and steep-edge spectral response

Flat-top and steep-edge spectral response of photodetectors is important for dense wavelength-division-multiplexed system. Realization of the flat-top and steep-edge response is very challenging. In the last two decades many methods have been proposed, but the spectral response linewidth is not acceptable to wavelength-division-multiplexes system. In this paper a novel RCE photodetector with flat-top and steep-edge spectral response is presented. Using the step shaped structure, designing multiple-step-type p-type In_0.67Ga_0.33As_0.7P_0.3 contact layer and adjusting the thickness of the absorption layer, a design with good flat-top performance is demonstrated such that the quantum efficiency is 51.161% in the flat-top passband, 0.5 and 3 dB bandwidths are 0.26 and 0.4 nm, respectively.     

Insights into quinaldic acid moiety formation in thiostrepton biosynthesis facilitating fluorinated thiopeptide generation

Thiostrepton (TSR), often referred as to a parent compound in the thiopeptide family, is a bimacrocyclic member that features a quinaldic acid (QA) moiety-containing side ring appended to the characteristic core system. QA biosynthesis requires an unusual ring-expanding conversion, showing a methyl transfer onto and a rearrangement of the indole part of L-tryptophan to give a quinoline ketone. Herein, we report that the process involves the activities of the radical methyltransferase TsrT, aminotransferase TsrA, dehydrogenase TsrE, and cyclase TsrD. TsrU, a stereospecific oxidoreductase, catalyzes the further conversion of the ketone into an enantiomerically pure S-alcohol. Elucidation of this chemistry, which is common in the biosynthesis of a number of thiopeptides sharing a QA side ring system, facilitates analog generation, as shown by the achievement of region-specific fluorination of thiostrepton with the improved antibacterial activity.     

A hybrid finite element approach to modeling sound radiation from circular and rectangular ducts

A numerical model based on a hybrid finite element method is developed that seeks to join sound pressure fields in interior and exterior regions. The hybrid method is applied to the analysis of sound radiation from open pipes, or ducts, and uses mode matching to couple a finite element discretization of the region surrounding the open end of the duct to wave based modal expansions for adjoining interior and exterior regions. The hybrid method facilitates the analysis of ducts of arbitrary but uniform cross section as well the study of conical flanges and here a modal expansion based on spherical harmonics is applied. Predictions are benchmarked against analytic solutions for the limiting cases of flanged and unflanged circular ducts and excellent agreement between the two methods is observed. Predictions are also presented for flanged and unflanged rectangular ducts, and because the hybrid method retains the sparse banded and symmetric matrices of the traditional finite element method, it is shown that predictions can be obtained within an acceptable time frame even for a three dimensional problem.     

Solubility and crystallization of BaHPO4 crystals

A study of growth of barium hydrogen phosphate (BaHPO₄) crystal from solution is reported. The raw materials of barium hydrogen phosphate were successfully synthesized through chemical reaction in water. The solubility in HCl and H₃PO₄ solution were studied. It increased when acid concentration and temperature become higher, and the fitted curve of solubility is nearly a line. The acid concentration affects crystalline morphology of BaHPO₄ crystal. The crystallization is well when the acid solution ranges from 0.5 to 0.8M. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Local defect structures and EPR studies on (FeO6)9− and (FeO4)5− clusters in YGG: Fe3+ system

The octahedral (FeO₆)^9? and tetrahedral (FeO₄)^5? clusters in yttrium gallium garnet (YGG): Fe³⁺ system are investigated based on the 252 × 252 complete energy matrices for d⁵ configuration ions in trigonal and tetragonal ligand fields, moreover, the EPR and optical spectra are made unified calculation. The results indicate that the defect structures around Fe³⁺ centres display expansion effects at different temperatures 4.2 and 295 K, and which are close to those in YIG garnet, respectively. Simultaneously, the defect structure parameters for Fe³⁺ centres in YGG are determined, and the relationship between the defect structure and the temperature has been discussed.     

YMnO_3薄膜的铁电行为及其纳米尺度铁电畴的研究

六方YMnO_3是一种特殊的多铁性材料,因其具有介电常数低、单一极化轴、无挥发性元素等特点,在磁电领域具有独特的优势,但目前关于YMnO_3薄膜的铁电性特别是畴结构的研究相对较少.本文采用溶胶-凝胶法在Si(100)基片上制备了多铁性YMnO_3薄膜,利用掠入射X-射线衍射、原子力显微镜对薄膜的结构及表面形貌进行了分析,用压力显微镜(PFM)技术研究了纳米尺度畴结构及微区电滞行为,并通过I-V,P-E曲线进一步研究了薄膜的漏电流和宏观电滞行为.结果表明,该薄膜为六方钙钛矿结构,YMnO_3晶粒大小均匀并且结晶性较好,薄膜表面粗糙度为7.209 nm.PFM图显示出清晰的电畴结构,结合典型的微区振幅蝴蝶曲线和相位电滞回线,证实该YMnO_3薄膜具有较好的铁电性.由于受内建电场的作用,振幅曲线和相位曲线都向正向偏移,表现出非对称特征.该薄膜的漏电流密度低于10~(-6)A·cm~(-2),因而其电滞回线基本能够达到饱和.     

一个不定方程以及它的实数解

研究了一类不定方程 ,并获得了它的所有实数解     

Population size estimation with covariate values missing non-ignorable

The main purpose of this paper is using capture-recapture data to estimate the population size when some covariate values are missing, possibly non-ignorable. Conditional likelihood method is adopted, with a sub-model describing various missing mechanisms. The derived estimate is proved to be asymptotically normal, and simulation studies via a version of EM algorithm show that it is approximately unbiased. The proposed method is applied to a real example, and the result is compared with previous ones.