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31.
Elena Chekmeneva José Manuel Díaz‐Cruz Cristina Ariño Miquel Esteban 《Electroanalysis》2010,22(2):177-184
The complexation of the natural antioxidants α‐lipoic acid (ALA) and its reduced form dihydrolipoic acid (DHLA) with Hg2+ was investigated by a recently proposed differential pulse voltammetric (DPV) method using the rotating Au‐disk electrode. Complexation processes are proposed from the multivariate curve resolution by alternating least squares (MCR‐ALS) analysis of DPV titration data. Main complexes were both 1 : 1 Hg : ALA and Hg : DHLA, although the formation of 1 : 2 complexes can be also deduced. ALA and DHLA show different Hg2+‐binding patterns at different pH. Voltammetric findings are completed with the data obtained by electrospray ionization mass‐spectrometry (ESI‐MS), especially in negative mode. 相似文献
32.
Núria Serrano José Manuel Díaz-Cruz Cristina Ariño Miquel Esteban 《Analytical and bioanalytical chemistry》2010,396(3):1365-1369
A commercially available screen-printed carbon electrode coated with an ex situ deposited bismuth film (BiSPCE) has been applied
to the determination of Pb(II) and Zn(II) ions in tap water (Barcelona water distribution network) by means of stripping voltammetry
(SV) and stripping chronopotentiometry (SCP). A good reproducibility of the measurements and a satisfactory agreement between
SV and SCP data were observed for both heavy metal ions. Although, in principle, the procedure could be also suited to the
determination of Cd(II), this species was not detected. The results were also consistent with the routine ICP-OES measurements
of the water distribution company, thus confirming the potential usefulness of such BiSPCE disposable devices for the analysis
of heavy metals in natural waters.
相似文献
33.
Poikonen A 《The Journal of the Acoustical Society of America》2011,129(4):EL128-EL134
Ambient noise spectra in a shallow brackish water environment were found to be steeper than expected at frequencies above 10 kHz. The high-frequency behavior of the spectra was resolved by modeling dispersion and noise in bubbly water. Bubble size distributions fitted to the brackish water spectra exhibit a distinctive maximum in the radius range 0.1-0.3 mm, and a substantial drop in bubble density below a radius of 0.1 mm. The brackish water distributions were tied to an oceanic spectrum with a spectral slope of 5.7 dB/octave obtained with a -3 / 2 power law dependence of bubble size density on radius. 相似文献
34.
Dislocation-pairing transitions in hot grain boundaries 总被引:1,自引:0,他引:1
We report the finding of a novel grain-boundary structural phase transition in both molecular-dynamics and phase-field-crystal simulations of classical models of bcc Fe. This transition is characterized by pairing of individual dislocations with mixed screw and edge components. We demonstrate that this type of transition is driven by a combination of factors including elastic softening, core interaction, and core disordering. At high homologous temperatures the occurrence of this transition is shown to prevent premelting at misorientation angles where it would otherwise be expected. 相似文献
35.
Hämäläinen SK Sun Z Boneschanscher MP Uppstu A Ijäs M Harju A Vanmaekelbergh D Liljeroth P 《Physical review letters》2011,107(23):236803
Despite the enormous interest in the properties of graphene and the potential of graphene nanostructures in electronic applications, the study of quantum-confined states in atomically well-defined graphene nanostructures remains an experimental challenge. Here, we study graphene quantum dots (GQDs) with well-defined edges in the zigzag direction, grown by chemical vapor deposition on an Ir(111) substrate by low-temperature scanning tunneling microscopy and spectroscopy. We measure the atomic structure and local density of states of individual GQDs as a function of their size and shape in the range from a couple of nanometers up to ca. 20 nm. The results can be quantitatively modeled by a relativistic wave equation and atomistic tight-binding calculations. The observed states are analogous to the solutions of the textbook "particle-in-a-box" problem applied to relativistic massless fermions. 相似文献
36.
The Zinc Selenide (ZnSe) thin films have been deposited on SnO2/glass substrates by a simple and inexpensive chemical bath deposition (CBD). The structural, optical and electrical properties of ZnSe films have been characterized by X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDAX), optical absorption spectroscopy, and four point probe techniques, respectively. The films have been subjected to different annealing temperature in Argon (Ar) atmosphere. An increase in annealing temperature does not cause a complete phase transformation whereas it affects the crystallite size, dislocation density and strain. The optical band gap (Eg) of the as-deposited film is estimated to be 3.08 eV and decreases with increasing annealing temperature down to 2.43 eV at 773 K. The as-deposited and annealed films show typical semiconducting behaviour, dρ/dT > 0. Interestingly, the films annealed at 373 K, 473 K, and 573 K show two distinct temperature dependent regions of electrical resistivity; exponential region at high temperature, linear region at low temperature. The temperature at which the transition takes place from exponential to linear region strongly depends on the annealing temperature. 相似文献
37.
This paper is concerned with the adaptive control problem, over the infinite horizon, for partially observable Markov decision processes whose transition functions are parameterized by an unknown vector. We treat finite models and impose relatively mild assumptions on the transition function. Provided that a sequence of parameter estimates converging in probability to the true parameter value is available, we show that the certainty equivalence adaptive policy is optimal in the long-run average sense. 相似文献
38.
By using two-section fibre where the first section has no spin and the second one is periodically spun, we demonstrate reduced
polarization dependent gain and polarization mode dispersion (0.3 dB and 0.0072 ps·km−1/2 correspondently) in a distributed fibre Raman amplifier. 相似文献
39.
40.
We briefly summarize our joint effort to understand catalytic reactions on the model catalyst RuO2(1 1 0) on the atomic scale, applying state-of-the-art density functional theory calculations and surface chemical characterizations in parallel. This intimate theory/experiment interplay allows us to gain new and deep insights into a catalytic system under investigation and to save recourses such as experimental and computing time as well as (wo)man power. Here we illustrate the utility of this intimate theory/experiment approach with a variety of recent examples related to the extraordinary activity of RuO2. The identification of RuO2(1 1 0) as the catalytically active state in the oxidation of CO on Ru(0 0 0 1) (Science 287 (2000) 1474) triggered a paradigm shift in model catalysis from the view of a rigid catalyst towards a structural and chemically flexible catalyst which adapts itself to the reaction conditions. 相似文献