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31.
The controlled hydrolysis of fluoro(2-methylbutan-2-oxy)di(pentan-2,4-dionato)tin followed by annealing at 400-550 °C gave conductive mesoporous F-doped SnO2 materials. The materials consist of a porous network of aggregated nanoparticles, the mesoporosity observed corresponding to the interparticle space. Tuning of the annealing temperature enabled us to prepare materials with surface areas ranging from 70 to 150 m2 g−1, with an average pore size comprised between 50 and 100 Å and with a mean particle diameter ranging from 50 to 120 Å. Resistivities as low as 1-2 Ω cm were measured for the sample treated at 550 °C which contained 2-3 at.% of fluorine. This powder reacted with 3-(6-trihex-1-ynylstannylhexyl)perylene to furnish a dye-sensitized F-doped SnO2 mesoporous materials. An intensity-dependent photocurrent was produced under blue light illumination using the cavity microelectrode (CME) technique. With an aqueous NaBr solution, the photopotential reaches 700 mV, a value slightly higher than that found for an undoped sensitized SnO2 powder (∼600 mV). 相似文献
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The mechanistic details of the initial steps of the polymerization brought about by a dicyclopentadienyl yttriumhydrid catalyst have been computationally investigated using approximate density functional theory. In accord with the experimental information, the overall reaction sequence Cp2YH + C2H4 → Cp2Y–C2H5 and Cp2YH + C3H6 → Cp2Y–C3H7 is computed to be exothermic by ca. 22.2 and 20.8 kcal mol–1, respectively. The reaction mechanism predicted by our calculations is in harmony with the available experimental information but provides additional information into the various elementary steps of this reaction, which could not be obtained by experimental means. 相似文献
34.
Nadja Hvala Mario Zec Stanko Strm?nik 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(6):587-605
This article deals with non-linear model parameter estimation from experimental data. As for non-linear models a rigorous identifiability analysis is difficult to perform, parameter estimation is performed in such a way that uncertainty in the estimated parameter values is represented by the range of model use results when the model is used for a certain purpose. Using this approach, the article presents a simulation study where the objective is to discover whether the estimation of model parameters can be improved, so that a small enough range of model use results is obtained. The results of the study indicate that from plant measurements available for the estimation of model parameters, it is possible to extract data that are important for the estimation of model parameters relative to a certain model use. If these data are improved by a proper measurement campaign (e.g. proper choice of measured variables, better accuracy, higher measurement frequency) it is to be expected that a valid model for a certain model use will be obtained. The simulation study is performed for an activated sludge model from wastewater treatment, while the estimation of model parameters is done by Monte Carlo simulation. 相似文献
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Elisa Will Johannes Ullmann Nadja Frömmgen Christopher Geppert Christian Gorges Michael Hammen Simon Kaufmann Andreas Krieger Wilfried Nörtershäuser 《Hyperfine Interactions》2014,227(1-3):157-168
An electronic measurement of high-voltages of several ten kV with accuracy as required for precision experiments is currently only feasible using highly sophisticated voltage dividers. Collinear laser spectroscopy can provide a direct and precise measurement of high-voltages using the Doppler shift of accelerated ions. Although proposed already in 1982, a measurement with relative accuracy better than 10?4 was not reported so far. To improve this accuracy, a dedicated new setup for high-voltage measurements will be installed at the Technische Universität Darmstadt. A two-chamber approach will be used to remove uncertainties due to the insufficiently known starting potential inside the ion source. Here we present a demonstration of the pump-and-probe technique performed in preparatory studies at the TRIGA-LASER experiment in Mainz. 相似文献
37.
Elisabeth Kreutzwiesner Nadja Noormofidi Frank Wiesbrock Wolfgang Kern Karl Rametsteiner Franz Stelzer Christian Slugovc 《Journal of polymer science. Part A, Polymer chemistry》2010,48(20):4504-4514
This study is aimed at investigating the microbiocidal potential of amino‐functionalized poly(norbornenes) in the solid state. A series of norbornene‐type monomers that carry secondary or tertiary amine functions as well as hexyl and dodecyl groups were prepared. Ring‐opening metathesis polymerization was used to prepare homopolymers of the amine bearing monomers and random copolymers of amine‐ and alkyl‐substituted monomers of high average molar mass. The resulting polymers were characterized by nuclear magnetic resonance, thermogravimetry, differential scanning calorimetry, infrared spectroscopy, and contact angle measurements, and their contact biocidal potential was evaluated according to the Japanese Industry standard Z2801. Tested microorganisms comprised Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Candida albicans, and Aspergillus niger. Microbiocidal activity of selected polymer films against E. coli, S. aureus, and A. niger was found, whereas against C. albicans and P. aeruginosa microbiostatic behavior was observed. Moreover, the most potent copolymer revealed no cytotoxicity rendering a biocidal polymer with potential applications in mammalian‐, and in particular, human‐related fields. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
38.
P. Tamiasso-Martinhon H. Cachet C. Deslouis V. Vivier 《Electrochemistry communications》2010,12(8):1074-1076
Fabrication and characterization of amorphous carbon nitride a-CNx microelectrodes are reported. These electrodes were prepared by DC-sputtering of a thin carbon layer on sharpened glass tip. The kinetic parameters (k0 and α) and the diffusion coefficient of the ferri-ferrocyanide redox probe were determined by steady-state voltammetry (CV) and by electrochemical impedance spectroscopy (EIS), and were used for characterizing both the electrochemical sensitivity of microelectrodes and their dimensions. The cathodic activation procedure of the electrode resulted in an increase of the electron rate constant. This procedure provides a new way for the fabrication of carbon microelectrodes for local electrochemical measurements. 相似文献
39.
Patrick Michaelis Nadja Klein Thomas Kneib 《Journal of computational and graphical statistics》2018,27(3):602-611
The normal and the t distribution are classical tools for building random effects regression models where both can be used for the specification of either the conditional response distribution or the random effects distribution. However, the underlying assumption of symmetry can be questionable in many applications. We, therefore, propose regression models where the skew-normal and skew-t distribution are considered for both the response and the random effects specification and embed these models in the framework of distributional regression such that regression predictors can be specified for all distributional parameters. The distributional regression framework also allows us to consider multivariate versions of the skew-normal and the skew-t distribution. For Bayesian inference, we adapt iteratively weighted least-square proposals within Markov chain Monte Carlo simulations such that they can also facilitate the inclusion of nonnormal random effects specifications. Model choice is based on the Watanabe–Akaike information criterion, in particular, to differentiate between skew and nonskew distributional specifications in a number of simulation studies. Finally, to illustrate their practical applicability, the developed models are applied to a study on cholesterol levels originating from the Framingham Heart Study and a dataset from the Demographic and Health Surveys on undernutrition among children in Nigeria. Supplementary material for this article is available online. 相似文献
40.
Michael E. Böttcher Nadja Neubert Katja von Allmen Elias Samankassou Thomas F. Nägler 《Isotopes in environmental and health studies》2018,54(3):324-335
In this study, we present the experimental results for stable barium (Ba) isotope fractionation (137Ba/134Ba) during the transformation of aragonite (CaCO3) and gypsum (CaSO4·2H2O) in Ba-bearing aqueous solution to witherite (BaCO3) and barite (BaSO4), respectively. The process was studied at three temperatures between 4 and 60?°C. In all cases, the transformation leads to a relative enrichment of the lighter 134Ba isotope in the solid compared to the aqueous solution, with 137/134Ba enrichment factors between –0.11 and ?0.17?‰ for BaCO3, and –0.21 and –0.26?‰ for BaSO4. The corresponding mass-dependent 138/134Ba enrichment factors are ?0.15 to –0.23?‰ for BaCO3, and –0.28 to –0.35?‰ for BaSO4. The magnitude of isotope fractionation is within the range of recent reports for witherite and barite formation, as well as trace Ba incorporation into orthorhombic aragonite, and no substantial impact of temperature can be found between 4 and 80?°C. In previous studies, ion (de)solvation has been suggested to impact both the crystallization process of Ba-bearing solids and associated Ba isotope fractionation. Precipitation experiments of BaSO4 and BaCO3 using an methanol-containing aqueous solution indicate only a minor effect of ion and crystal surface (de)solvation on the overall Ba isotope fractionation process. 相似文献