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61.
To enable utilization of the broad potential of copper isotopes in nuclear medicine, rapid and robust chelation of the copper is required. Bowl adamanzanes (bicyclic tetraaza ligands) can form kinetically stable copper complexes, but they are usually formed at low rates unless high pH values and high temperatures are applied. We have investigated the effects of the variation in the pH, different anions, and UV irradiation on the chelation rate. UV spectra of mixtures of Cu(2+) and [2(4).3(1)]adz in water show the existence of a long-lived two-coordinated copper(II) intermediate (only counting coordinated amine groups) at pH above 6. These findings are supported by pH titrations of mixtures of Cu(2+) and [2(4).3(1)]adz in water. Irradiation of this complex in the ligand-to-metal charge-transfer (LMCT) band by a diode-array spectrophotometer leads to photodeprotonation and subsequently to formation of the four-coordinated copper(II) complex at a rate up to 7800-fold higher at 25 °C than in the dark. Anions in the solution were found to have three major effects: competitive inhibition due to Cu(II) binding anions, inhibition of the photoinduced transchelation from UV-absorbing anions, and photoredox inhibition from acido ligands capable of acting as electron donors in LMCT reactions. Dissolved O(2) was also found to result in photoredox inhibition. 相似文献
62.
In SI Nielsen MG Vesborg PC Hou Y Abrams BL Henriksen TR Hansen O Chorkendorff I 《Chemical communications (Cambridge, England)》2011,47(9):2613-2615
We report here on a study of vertically aligned TiO(2) nanotube arrays grown by the one-step anodic oxidation technique and their photocatalytic performance for methane decomposition. Quantitative activity data as a function of film thickness is obtained. 相似文献
63.
We propose and study discontinuous Galerkin methods for strongly degenerate convection-diffusion equations perturbed by a fractional diffusion (Lévy) operator. We prove various stability estimates along with convergence results toward properly defined (entropy) solutions of linear and nonlinear equations. Finally, the qualitative behavior of solutions of such equations are illustrated through numerical experiments. 相似文献
64.
Jesper L. Mortensen Alan McWilliam Christopher G. Leburn Peter Tidemand-Lichtenberg Morten Thorhauge Jirí Janousek Christian T.A. Brown Alexander A. Lagatsky Preben Buchhave Wilson Sibbett 《Optics Communications》2006,260(2):637-640
Efficient generation of continuous-wave (CW) tunable light in the yellow region is reported. The method is based on sum-frequency mixing of a tunable Cr4+:forsterite laser with a Nd:YVO4 laser. A periodically poled lithium niobate crystal was placed intra-cavity in a Nd:YVO4 laser, and the Cr4+:forsterite laser was single-passed through the non-linear media. With this setup, it was possible to generate up to 3 mW of yellow light smoothly tunable from 573 to 587 nm. This is the highest output demonstrated to date for a tunable diode pumped solid-state CW laser in this wavelength region. The ways to improve the efficiency further are discussed. 相似文献
65.
Morten E. Simonsen Henrik Jensen Zheshen Li Erik G. Sgaard 《Journal of photochemistry and photobiology. A, Chemistry》2008,200(2-3):192-200
In this work the efficiency and physicochemical details of a thin film produced by help of a microwave assisted sol gel technique is compared to different commercial powders (Degussa P25 and Hombikat UV100) deposited on glass substrates. Furthermore, a supercritical produced TiO2 powder (SC 134) was included in the comparison.The prepared TiO2 films were characterized using XRD, XPS, AFM, DSC and DLS. The photocatalytic activity was determined using stearic acid as a model compound. Investigation of the prepared films showed that the Degussa P25 film and the sol–gel film were the most photocatalytic active films. The activity of the films was found to be related to the crystallinity of the TiO2 film and the amount of surface area and surface hydroxyl groups. Based on the XPS investigation of the films before and after UV irradiation it was suggested that the photocatalytic destruction of organic matter on TiO2 films proceeds partly through formation of hydroxyl radicals which are formed from surface hydroxyl groups created by interactions between adsorbed water and vacancies on the TiO2 surface. Furthermore a correlation between the amount of OH groups on the surface of the different TiO2 films and the photocatalytic activity was found. 相似文献
66.
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68.
E. R. Jakobsen 《BIT Numerical Mathematics》2004,44(2):269-285
In this paper we provide estimates of the rates of convergence of monotone approximation schemes for non-convex equations in one space-dimension. The equations under consideration are the degenerate elliptic Isaacs equations with x-depending coefficients, and the results applies in particular to certain finite difference methods and control schemes based on the dynamic programming principle. Recently, Krylov, Barles, and Jakobsen obtained similar estimates for convex Hamilton–Jacobi–Bellman equations in arbitrary space-dimensions. Our results are only valid in one space-dimension, but they are the first results of this type for non-convex second-order equations. 相似文献
69.
70.
Liquid hydrogen in protonic chabazite 总被引:2,自引:0,他引:2
Zecchina A Bordiga S Vitillo JG Ricchiardi G Lamberti C Spoto G Bjørgen M Lillerud KP 《Journal of the American Chemical Society》2005,127(17):6361-6366
Due to its fully reversible nature, H(2) storage by molecular adsorption could represent an advantage with respect to dissociative processes, where kinetic effects during the charging and discharging processes are present. A drawback of this strategy is represented by the extremely weak interactions that require low temperature and high pressure. High surface area materials hosting polarizing sites can represent a viable way toward more favorable working conditions. Of these, in this contribution, we have studied hydrogen adsorption in a series of zeolites using volumetric techniques and infrared spectroscopy at 15 K. We have found that in H-SSZ-13 zeolite the cooperative role played by high surface area, internal wall topology, and presence of high binding energy sites (protons) allows hydrogen to densify inside the nanopores at favorable temperature and pressure conditions. 相似文献