Identification of high-lying odd energy levels of uranium by resonant ionization mass spectrometry

Single-colour and two-colour multiphoton resonant ionization spectra of uranium atom were studied extensively with a Nd: YAG laser-pumped dye laser atomic beam apparatus time-of-flight mass spectrometer in our laboratory. The energy locations of high-lying odd-parity levels in the region 33 003-34 264 cm(-1),mearured by a two-colour three-step ionization technique, were reported here. The angular momentum quantum number J was uniquely assigned for these levels by using angular momentum selection rules.

The role of redox property of La2-x(Sr,Th)(x)CuO4 +/-lambda playing in the reaction of NO decomposition and NO reduction by CO

Two systems of mixed oxides, La2-xSrxCuO4 +/- lambda (0.0 less than or equal to x less than or equal to 1.0) and La(2-x)Tn(x)CuO(4 +/-) (lambda) (0.0 less than or equal to x less than or equal to 0.4), with K2NiF4 structure were prepared. The average valence of Cu ions and oxygen nonstoichiometry (lambda) were determined by means of chemical analysis. Meanwhile, the adsorption and activation of nitrogen monoxide (NO) and the mixture of NO + CO over the mixed oxide catalysts were studied by means of mass spectrometry temperature-programmed desorption (MS-TPD). The catalytic behaviors in the reactions of direct decomposition of NO and its reduction by CO were investigated, and were discussed in relation with average valence of Cu ions, A and the activation and adsorption of reactant molecules. It has been proposed that both reactions proceed by the redox mechanism, in which the oxygen vacancies and the lower-valent Cu ions play important roles in the individual step of the redox cycle. Oxygen vacancy is more significant for NO decomposition than for NO + CO reaction. For the NO + CO reaction, the stronger implication of the lower-valent Cu ions or oxygen vacancy depends on reaction temperature and the catalytic systems (Sr- or Th-substituted). (C) 2000 Elsevier Science B.V. All rights reserved.

Preparation and characterization of ternary europium complex-doped thin sol-gel hybrid film by fluorescence spectroscopy

Ternary europium complex with dibenzoylmethane (DBM) and 1,10-phenanthroline (phen) was in-situ synthesized in thin SiO2/polyvinyl butyral (PVB) hybrid films by a two-step sol-gel process and characterized by;means of fluorescence spectroscopy. The luminescence spectra, fluorescence lifetimes and photostability were all investigated. The results showed that the hybrid films exhibited the characteristic emission bands of the Central rare earth Eu3+. In addition, Eu3+ presented longer fluorescence lifetime than in an ethanol solution and the complex had a higher photostability in the hybrid film than in the PVB film containing the corresponding pure complex.

Catalytic reduction of NO by CO with hydrotalcite derived mixed oxides

Catalysts with spinel structure derived from Hydrotalcite-like Compounds (HTLcs) containing cobalt have been investigated in NO catalytic reduction by Co. It was found that catalysts with spinel structures derived from HTLcs had obviously higher activity than that prepared from general methods. A two-step reaction was observed during the reaction curse: NO was first reduced to N2O by Co, and with the increase of temperature, the N2O was reduced to N-2. The reactivity of the catalysts studied increased with the amount of cobalt-content in the catalyst, and decreased with the calcination temperature. The crystal defect would play an important role in the reaction.

Some unusual features of highly oriented pyrolytic graphite observed by electrochemical scanning tunneling microscopy

Highly oriented pyrolytic graphite (HOPG) is the substrate often used in scanning tunneling microscopy (STM). It is well known that STM images of the basal plane of HOPG show some unusual structural patterns. In this letter, we present in situ STM images of some unusual features on HOPG in solutions, including normal or abnormal chain-like features and hexagonal or oblique superperiodic structures. These features emerge both next to and apart from the step of HOPG.

ELECTROCATALYTIC REDUCTION OF DIOXYGEN BY AN ELECTROCHEMICALLY POLYMERIZED FLAVIN ADENINE-DINUCLEOTIDE FILM

An electrochemically polymerized flavin adenine dinucleotide (FAD) film electrode is reported for the first time. The polymerized film was prepared by a two-step method. The electrocatalytic reduction of dioxygen at a glassy carbon electrode (GCE) modifie

DETERMINATION OF PARAMETERS OF FAST CHEMICAL REACTION OF ALIZARIN RED S BY SPECTROELECTROCHEMICAL METHOD WITH LOPTLC

The rate constant of very fast chemical reaction generally can be measured by electrochemical methods, but can not by the thin layer electrochemical methods because of the influence of diffusion effect. Long optical path length thin layer cell (LOPTLC) with large ratio of electrode area to solution volume can be used to monitor the fist chemical reaction in situ with high sensitivity and accuracy. It enable the adsorption spectra to be measured without the influence of diffusion effect. In the present paper, a fast chemical reaction of Alizarin Red S (ARS) with its oxidative state has been studied. The reaction equilibrium constant (K) under different potentials can be determined by single step potential-absorption spectra in LOPTLC. An equilibrium constant of 7.94 x 10(5) l.mol(-1) for the chemical reaction has been obtained from the plot of lgK vs. (E - E-1(0)'). Rate constant (k) under different potentials can be measured by single step potential-chronoabsorptiometry. A rate constant of 426.6 l.mol(-1).s(-1) for the chemical reaction has been obtained from the plot of lgK vs. (E - E-1(0)') with (E - E-1(0)') = 0.

Biosorption of Cr(VI) from aqueous solutions by nonliving green algae Cladophora albida

Biosorption of Cr(VI) from aqueous solutions by nonliving green algae Cladophora albida was investigated in batch experiments. The influence of pH, algal dosage, initial Cr(VI) concentration, temperature and coexisting anions on removal efficiencies of C. albida was studied. Cr(VI) removal process was influenced significantly by the variation of pH, and the optimum pH was chosen at a range of 1.0-3.0. The optimum algal dosage 2 g/L was used in the experiment. The removal rate of Cr(VI) was relatively rapid in the first 60 min, but then the rate decreased gradually. Removal mechanism was studied by analyzing Cr(VI) and total Cr in the solution. Biosorption and bioreduction were involved in the Cr(VI) removal. Biosorption of Cr(VI) was the first step. followed by Cr(VI) bioreduction and Cr(III) biosorption on the algal biomass. Actual industrial wastewater was used to evaluate the practicality of the biomass C. albida. From a practical viewpoint, the abundant and economic biomass C. albida could be used for removal of Cr(VI) from wastewater by the reduction of toxic Cr(VI) to less toxic Cr(III). (C) 2008 Elsevier Ltd. All rights reserved.

Characterization of eastern oyster (Crassostrea virginica Gmelin) chromosomes by fluorescence in situ hybridization with bacteriophage P1 clones

Chromosome identification is an essential step in genomic research, which so far has not been possible in oysters. We tested bacteriophage P1 clones for chromosomal identification in the eastern oyster Crassostrea virginica, using fluorescence in situ hybridization (FISH). P1 clones were labeled with digoxigenin-11-dUTP using nick translation. Hybridization was detected with fluorescein-isothiocyanate-labeled anti-digoxigenin antibodies and amplified with 2 layers of antibodies. Nine of the 21 P1 clones tested produced clear and consistent FISH signals when Cot-1 DNA was used as a blocking agent against repetitive sequences. Karyotypic analysis and cohybridization positively assigned the 9 P1 clones to 7 chromosomes. The remaining 3 chromosomes can be separated by size and arm ratio. Five of the 9 P1 clones were sequenced at both ends, providing sequence-tagged sites that can be used to integrate linkage and cytogenetic maps. One sequence is part of the bone morphogenetic protein type 1b receptor, a member of the transforming growth factor superfamily, and mapped to the telomeric region of the long arm of chromosome 2. This study shows that large-insert clones such as P1 are useful as chromosome-specific FISH probes and for gene mapping in oysters.

Analysis of urinary 8-hydroxydeoxyguanosine by capillary electrophoresis and solid-phase extraction

Urinary 8-hydroxydeoxyguanosine (80HdG) has been considered as an excellent marker of individuals at high risk of developing cancer. Until now, urinary 80HdG has largely been measured by high-performance liquid chromatography with electrochemical detection. A new method for the analysis of urinary 80HdG by high-performance capillary electrophoresis has been developed and optimized in our laboratory. A single step solid-phase extraction procedure was optimized and used for extracting 80HdG from human urine. Separations were performed in an uncoated silica capillary (50 cm x 50 tm i.d.) using a P/ACE MDQ system with UV detection. The separation of 80HdG from interfering urinary matrix components is optimized with regard to pH, applied voltage, pressure injection time and concentration of SDS in running buffer. The detection limit of this method is 0.4 mug/ml, the linear range is 0.8-500 mug/ml, the correlation coefficients levels is better than 0.999. The developed method is simple, fast and good reproducibility, furthermore, it requires a very small injection volumes and low costs of analysis, which makes it possible to provide a new noninvasive assay for an indirect measurement of oxidative DNA damage.

The study of oxygen spillover and back spillover on Pt/TiO2 by a potential dynamic sweep method

Oxygen spillover and back spillover on Pt/TiO2 catalysts have been studied by a potential dynamic sweep method. The characteristics of I-V profiles of Pt/TiO2 electrodes in the three potential sweep regions are different from those of Pt and TiO2 electrodes. The catalytic role of Pt/TiO2 in oxygen spillover and back spillover is identified. It decreases, and the electrochemical oxygen adsorption (or desorption) increases with elevating temperature of hydrogen post-treatment of Pt/TiO2; to a certain extent (hydrogen post-treatment of Pt/TiO2 at 700 degrees C), the control step of oxygen electrode process (anodic oxidation or cathodic reduction) changes from oxygen diffusion to electrochemical oxygen adsorption or desorption, respectively. Increasing the amount of Pt supported on TiO2 enhances the processes of oxygen spillover and back spillover. (C) 1999 Elsevier Science B.V. All rights reserved.

The Bifurcation Interpreter: A Step Towards the Automatic Analysis of Dynamical Systems

The Bifurcation Interpreter is a computer program that autonomously explores the steady-state orbits of one-parameter families of periodically- driven oscillators. To report its findings, the Interpreter generates schematic diagrams and English text descriptions similar to those appearing in the science and engineering research literature. Given a system of equations as input, the Interpreter uses symbolic algebra to automatically generate numerical procedures that simulate the system. The Interpreter incorporates knowledge about dynamical systems theory, which it uses to guide the simulations, to interpret the results, and to minimize the effects of numerical error.

Learning Fine Motion by Markov Mixtures of Experts

Compliant control is a standard method for performing fine manipulation tasks, like grasping and assembly, but it requires estimation of the state of contact between the robot arm and the objects involved. Here we present a method to learn a model of the movement from measured data. The method requires little or no prior knowledge and the resulting model explicitly estimates the state of contact. The current state of contact is viewed as the hidden state variable of a discrete HMM. The control dependent transition probabilities between states are modeled as parametrized functions of the measurement We show that their parameters can be estimated from measurements concurrently with the estimation of the parameters of the movement in each state of contact. The learning algorithm is a variant of the EM procedure. The E step is computed exactly; solving the M step exactly would require solving a set of coupled nonlinear algebraic equations in the parameters. Instead, gradient ascent is used to produce an increase in likelihood.

Analysis of phenols by high-performance liquid chromatography with pre-column derivatization by 2-(9-carbazole)-ethyl-chloroformate

2-(9-Carbazole)-ethyl-chloroformate (CEOC), a novel pre-column fluorescence labeling reagent, has been synthesized and applied for the derivatization of phenols. Taken phenol, p-chlorophenol, 2,5-dimethylphenol, 2,4-dichlorophenol and 1,4-dihydroxybenzene as testing standards, the effects of derivatization conditions, such as pH of borate buffer, reaction time and fluorescent tagging reagent concentration, have been systematically studied. Under the optimized conditions, CEOC reacts readily with the phenols to form stable derivatives with excitation and emission wavelengths, respectively, at 293 and 360 nm. The single step derivatization reaction could be finished within 20 min even at room temperature. Such a method has been successfully applied to the analysis of phenols in printing ink by high-performance liquid chromatography. (c) 2005 Elsevier B.V. All rights reserved.