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V Correcher J Garcia-Guinea FJ Valle-Fuentes 《Journal of Thermal Analysis and Calorimetry》2006,83(2):439-444
In
this paper, novel results on the blue thermally stimulated luminescence (TSL)
emission of ulexite (NaCaB5O6(OH)6·5H2O)
have been studied. The four maxima appearing at 60, 110, 200 and 240°C
on the TSL glow curves of this borate could be respectively associated to:
(i) the first dehydration (NaCaB5O6(OH)6·5H2O→NaCaB5O6(OH)6·3H2O),
(ii) the creation-annihilation of the three-hydrated
phase, (iii) the Na-coordinated chains
dehydroxylation and the starting point of the alkali self-diffusion through
the lattice and (iv) the amorphisation
of the lattice. These results are fairly well correlated with the differential
thermal analyses (DTA), in situ thermal observations under environmental scanning
electron microscope (TESEM) and thermal X-ray diffraction (TXRD) techniques. 相似文献
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A method is described for neutron activation analysis of thorium by employing thorium-233. Decontamination steps include anion exchange in 12.5 N HCL, precipitation of fluoride, extraction with mesityl oxide and thorium oxalate precipitation. The time spent is less than 1 h; spurious activities in counting samples amount only to 2% and can easily be corrected for. The sensitivity of the method is ca. 0.02 μg of thorium in a neutron flux of 1012n/cm2/sec with an irradiation time of 5 min. 相似文献
7.
Francisco Pedroche Miguel Rebollo Carlos Carrascosa Alberto Palomares 《Czechoslovak Mathematical Journal》2016,66(3):603-620
In this paper we present some theoretical results about the irreducibility of the Laplacian matrix ordered by the Reverse Cuthill-McKee (RCM) algorithm. We consider undirected graphs with no loops consisting of some connected components. RCM is a well-known scheme for numbering the nodes of a network in such a way that the corresponding adjacency matrix has a narrow bandwidth. Inspired by some properties of the eigenvectors of a Laplacian matrix, we derive some properties based on row sums of a Laplacian matrix that was reordered by the RCM algorithm. One of the theoretical results serves as a basis for writing an easy MATLAB code to detect connected components, by using the function “symrcm” of MATLAB. Some examples illustrate the theoretical results. 相似文献
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A series of MCM22 zeolites exchanged with copper and cobalt are studied for the selective catalytic reduction (SCR) of NO
with C3H8 and the behavior compared with that of Cu and Co-beta and ZMS5 zeolites. The results show that Co and Cu-MCM22 samples are
stable SCR catalysts. These zeolites give the maximum activity at 450°C. Their behavior towards oxygen content in the reactant
phase and exchange level of the metal in the catalyst, is qualitatively similar to that of metal exchanged beta and ZSM5 zeolite,
but the yields obtained with this zeolite are lower in any case. The infrared studies of adsorbed NO show, contrary to what
is occurring in ZSM5 in which only Cu+ sites are observed at low NO partial pressure, that in this condition, Cu+ and Cu2+ species are formed on MCM22. The results indicate that in MCM22, the copper located in the 10 member ring (MR) circular channels
behaves similarly to that present in ZSM5, while the Cu present in the 12 MR cavities has a strong tendency to agglomerate
forming non active CuO clusters. 相似文献
10.
Coronado E Galán-Mascarós JR Martí-Gastaldo C Palomares E Durrant JR Vilar R Gratzel M Nazeeruddin MK 《Journal of the American Chemical Society》2005,127(35):12351-12356
The selectivity and sensitivity of two colorimetric sensors based on the ruthenium complexes N719 [bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) bis(tetrabutylammonium) bis(thiocyanate)] and N749 [(2,2':6',2' '-terpyridine-4,4',4' '-tricarboxylate)ruthenium(II) tris(tetrabutylammonium) tris(isothiocyanate)] are described. It was found that mercury ions coordinate reversibly to the sulfur atom of the dyes' NCS groups. This interaction induces a color change in the dyes at submicromolar concentrations of mercury. Furthermore, the color change of these dyes is selective for mercury(II) when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II). The detection limit for mercury(II) ions--using UV-vis spectroscopy--in homogeneous aqueous solutions is estimated to be approximately 20 ppb for N719 and approximately 150 ppb for N749. Moreover, the sensor molecules can be adsorbed onto high-surface-area mesoporous metal oxide films, allowing reversible heterogeneous sensing of mercury ions in aqueous solution. The results shown herein have important implications in the development of new reversible colorimetric sensors for the fast, easy, and selective detection and monitoring of mercuric ions in aqueous solutions. 相似文献