Rapid determination of lead extracted by acetic acid from glazed ceramic surfaces by flow injection on-line preconcentration and spectrophotometric detection

A rapid method has been developed for the determination of lead extracted by acetic acid from glazed ceramic surfaces by flow injection analysis without any pretreatment. An aliquot of 4% acetic acid solution, which has been kept in a teacup for 24 h in the dark, is injected into a carrier solution (1 M nitric acid) and passed through a Pb-Spec resin column. After washing the column with an ammonium nitrate solution, the lead adsorbed on the column is eluted with an ammonium oxalate solution and then merged with a 4-(2-pyridylazo)resorcinol (PAR) solution, followed by measurement of the absorbance of the lead-PAR complex at 530 nm. The detection limit, concentration giving a signal equal to three times the standard deviation of the blank signal, is 8 ng ml⁻¹. The relative standard deviation of measurements at the 0.8 μg ml⁻¹ level is 0.35% (n = 5). The sample throughput is 12 per hour.     

Rapid differentiation of Fusarium oxysporum isolates using PCR-SSCP with the combination of pH-variable electrophoretic medium and low temperature

Differentiation of Fusarium oxysporum is significantly important for unraveling the pathogenetic mechanism of Fusaria wilts. In this study, isolates of F. oxysporum were screened from the soils in the rhizosphere of watermelon plant by Komada medium and differentiated by SSCP approach with the combination of pH-variable electrophoretic medium (Tris-MES-EDTA (TME), pH 6.1) and low temperature (9 degrees C). We found that TME was a good electrophoretic medium and its pH value was variable over the course of electrophoresis in our apparatus. The pH-variable electrophoretic medium made more contribution for the better differentiation of F. oxysporum isolates than low temperature. The combination of TME pH 6.1 and low temperature showed an improved effect on resolution of ssDNAs. Leaving partial nondenatured dsDNA for SSCP was advantageous for differentiation of F. oxysporum isolates. The SSCP patterns of F. oxysporum isolates proved to be highly reproducible. Sequencing data confirmed that this SSCP method could detect one single base change within the 550 bp PCR fragment from the ribosomal internal transcribed spacer region of F. oxysporum.     

Transformed steroids. 118. The geometric isomerism of 20-ethoxycarbonylhydrazones of 3β-hydroxy-16,17α-cyclopropanopregn-5-en-20-one

In the reaction of the 3β-acetate of 3β-hydroxy-3′H-cyclopropano[16,17α]pregn-5-en-20-one (I) with ethoxycarbonylhydrazine in AcOH at 20°C (exposure for up to 6 days), a chromatographically separable equilibrium mixture of the 20Z-ethoxycarbonylhydrazone of 3β-acetoxy-3′H-cyclopropano[16,17α]pregn-5-en-20-one (II), with mp 190–195°C, and the 20E-ethoxycarbonylhydrazone of 3β-acetoxy-3′H-cyclopropano[16,17α]pregn-5-en-20-one (III) with mp 186–193°C (ratio 2:1) is obtained. The geometric isomers obtained are distinguished by IR, PMR, and CD spectroscopy. It has been shown that the observed geometric isomerism takes place via an intermediate enehydrazine form.     

Disorder-induced microscopic magnetic memory

Using coherent x-ray speckle metrology, we have measured the influence of disorder on major loop return point memory (RPM) and complementary point memory (CPM) for a series of perpendicular anisotropy Co/Pt multilayer films. In the low disorder limit, the domain structures show no memory with field cycling--no RPM and no CPM. With increasing disorder, we observe the onset and the saturation of both the RPM and the CPM. These results provide the first direct ensemble-sensitive experimental study of the effects of varying disorder on microscopic magnetic memory and are compared against the predictions of existing theories.     

Field Patterns in Double Circular-Groove Guide by Finite Element Method

The electromagnetic power coupling in symmetrical and asymmetrical double circular-groove guides have been analyzed by finite element method (FEM) in this paper. The electrical field patterns of the dominant mode and the first higher-order TE mode have been presented. The electromagnetic field of the dominant mode distributes with a concentration in the two grooves and the region between grooves as well for symmetrical double circular-groove guide, while it distributes with a concentration in the groove with larger radius for the asymmetrical double circular-groove guide. The electrical field patterns of the first higher-order TE mode in symmetrical and asymmetrical double circular-groove guide are also presented. The figures in this paper have important values in design of circular-groove guide power coupler for millimeter wave applications.     

CuO/Al2O3、CuO/CeO2-Al2O3和CuO/La2O3-Al2O3催化剂中CuO物种被CO氧化的比较

用浸渍法制备了CuO/Al2O3 (Cu/Al)、CuO/CeO2- Al2O3 (Cu/CeAl)和CuO/La2O3-Al2O3(Cu/LaAl)催化剂. 通过原位XRD、Raman和H2-TPR方法， 对催化剂中的CuO物种以及CuO-Al2O3的固-固相反应进行了表征. 结果表明，对于Cu/Al催化剂，CuAl2O4存在于CuO与Al2O3层之间，CuO以高分散和晶相两种相态存在于催化剂的表层；对于Cu/CeAl催化剂，除了少量高分散和晶相的CuO存在于表层外，大部分CuO迁移到了CeO2的内层，     

Efficient carbon-doped nanostructured TiO<Subscript>2</Subscript> (anatase) film for photoelectrochemical solar cells

In this paper, we have demonstrated that carbon-doped nanostructured TiO₂ (CD ns-TiO₂) films could be prepared simply and cheaply with oxalic acid and tetrabutylammonium bromide (Bu₄N·Br) as the carbon sources. The surface morphology of the films was a multiple-porous network structure.The average size of nanoparticle was about 40 nm. Carbon doped into substitutional sites of TiO₂ has also proven to be indispensable for band-gap narrowing and photovoltaic effect. Carbon doping lowered the band gap of n-TiO₂ to 1.98, 1.64, and 1.26 eV. The CD ns-TiO₂ film was first used as photoanode for solar cells, exhibiting high photocurrent densities (l.34 mA/cm²) and yielding an overall conversion efficiency (η) of 4.42 %.     

Structural study and magnetoresistance effect of epitaxial La0.67Sr0.33MnO3–δ and Pr0.7Ca0.3MnO3−δ multilayer films

La_0.67Sr_0.33MnO_3−δ (LSMO) and Pr_0.7Ca_0.3MnO_3−δ (PCMO) multilayer epitaxial films, which were fabricated with different LSMO and PCMO layer thickness on LaAlO₃ single crystal substrates of (0 0 1) orientation by a direct current magnetron sputtering technique, were studied further, after the structure, magnetoresistance effect and magnetic properties of LSMO/PCMO/LSMO (LPL) trilayer epitaxial films were systemically studied. The superlattice structures of multilayer films were observed according to the diffraction peaks of X-ray diffraction patterns at small angles. The metal–insulator transition temperature (T_P) and peak resistivity (ρ_max) obviously changed when we altered the thickness of PCMO middle layer and the intra-field related with the thickness of those layers and their interaction. Considering the effect of the distribution of electrical field and current, and the interaction among the layers of LSMO and PCMO, an effective fact n* was introduced to replace n (the number of layer). All the calculated values of ρ (the resistivity of multilayer films) accorded with the experimental values.