Search results for "mines"
showing 10 items of 2609 documents
Time-Resolved Luminescence of Nanocrystalline Inorganic Complex Oxides
2007
Two types of complex nanosized oxides – cerium doped Y3Al5O12 (YAG) and CaWO4– have been studied by means of time-resolved luminescence spectroscopy. Comparative study of time-resolve luminescence characteristics of cerium doped YAG single crystal, nanopowders and nanoceramic as well as for CaWO4 macro- and nanocrystals has been done. Two components in the decay kinetic of Ce3+ related emission in YAG nanocrystals were detected and it was suggested that a different energy transfer rate to volume and surface Ce3+ ions takes place. It is shown that the segregation of Ce3+ ions near nanoparticles surface and/or dislocation lines plays a crucial role in degradation of light yield of cerium rela…
The luminescence properties of ZnO nanopowders
2007
Pure and Al3+ doped ZnO nanopowders were studied by means of time-resolved luminescence spectroscopy. The powders were synthesized by hydrothermal and plasma methods. These powders were used as a raw material for vaporization-condensation process inside the Solar reactor. The commercially available ZnO nanopowder was studied for a comparison. Exciton to defect band luminescence intensity ratio was estimated in different types of ZnO nanopowders. It was found that nanopowders with whiskers morphology show superlinear luminescence intensity depending on excitation density. The observed effect depends on the average nanoparticle size and on the powder morphology.
Up-conversion process in erbium doped lithium fluoride bulk crystal, lithium borate glass and glass ceramics
2007
In our research the up-conversion processes in Er doped bulk LiF crystal, lithium borate oxyfluoride glass and lithium borate oxyfluoride glass ceramics were studied: up- conversion and traditional photoluminescence spectra, the up-converted signal as a function of the laser power are presented. It was found that sharp luminescence bands in the visible part of the spectrum appear when the bulk crystal is subjected to IR irradiation at 980 nm by a laser diode. After the heat treatment of the glass submicron crystallites were detected by SEM technique. The presence of LiF crystalline phase in the oxyfluoride glass ceramics was proved by XRD method. The questions about the synthesis of the oxy…
Luminescence properties of AlN nanostructures revealed under UV light irradiation
2007
The luminescence properties of the AlN nanostructures – nanorods and nanotips -revealed under the UV irradiation are similar to those of the AlN ceramics. Presumably they are induced by the recombination processes in the oxygen-related centers. All the studied luminescence processes (photoluminescence, thermoluminescence and optically stimulated luminescence) in the nanostructures occur mainly through the host lattice excitation. That may be explained by the smaller concentration of the defect centers and more perfect structure of the host lattice of the nanostructures compared to the ceramics. The small mutual differences revealed in the spectra and TL curves of the AlN nanotips and nanoro…
Les loisirs sportifs en milieu de grande industrie : sport, patronat et organisations ouvrières au Creusot et à Montceau-les-Mines (1879-1939).
2009
This study describes the origin and development of the sports phenomenon in the industrial cities of Le Creusot and Montceaules-Mines (Saône-et-Loire, Burgundy), from 1879 to 1939. Throughout this period, sports in Le Creusot were totally dominated by associations led and controlled by the manufacturers, whereas in Montceau-les-Mines, worker sports were the object of conflict between industrialists and labor organisations. Such a contrast signals the existence of tight connections at the local level between the history of a place and the way in which a sport develops there. At the same time, these observations suggest some conclusions about historical conditions necessary to the emergence o…
Comparison of ZrO2:Y nanocrystals and macroscopic single crystal luminescence
2007
The luminescence spectra of a tetragonally structured ZrO2:Y single crystal and nanocrystals were compared. It was found that the number of luminescence centers contributed to the spectra. The excitation of luminescence within the band gap region led to different luminescence spectra for the single crystal and nanocrystal samples, whereas recombinative luminescence spectra were the same for both samples. The origin of this difference is that in the nanocrystals, even under excitation within the band gap, charge carriers were created. Zirconium- oxygen complexes distorted by intrinsic defects were proposed to be the luminescence centres responsible for the wide luminescence band observed.
Investigation of archaeological amphorae from the Egadi battles
2022
Abstract Archaeological ceramics are considered one of the most important sources of both technological and chronological information. Here, the investigation of some archaeological underwater amphorae from the Egadi’s Battle, that decided the end of the First Punic War (241 B.C.), is reported. X-ray Diffraction (XRD), X-ray Fluorescence (XRF), petrography, and Thermoluminescence (TL) were used to determine the composition of the amphorae and to evaluate the compatibly of their age with the above Battle. Considering the historical importance of the act and the well-defined historical collocation these amphorae represent an interesting archaeometric case study.
Titanium complexes for the formation of nitrogen compounds : synthesis of homoallylamines and amidines
2011
Homoallylic amines are key reagents for the formation of a large number of biologically interesting products. Due to the double bond of their allylic moiety, easily functionalisable, they are commonly used in organic synthesis. This research work deals with the synthesis of homoallylic amines thanks to titanium complexes. In fact, the reductive coupling between of imines and dienes promoted by titanium allows the formation of diastereoisomeric homoallylamines syn and anti. The diastereoselectivity of the reaction is directly affected by the nitrogen substituent. Whether it is benzyl or phenyl, the selectivity will be in favour of syn or anti respectively. Moreover, the addition of a the Lew…
The Photoluminescence and Biochemical Properties of Biological
1995
The UV-VIS range photoiuminescence of entomophatogenic mushrooms Entomophora txaxteriana (Petch) Hall et Bell, Beauveria bassiana (Bals) Vuill as well as of biologicals on their basis enthomophtorin and bouverin are examined. They were worked out for abolition insect-pests of plants: louses of apple-tree and Colorado potato beetles, therefore obtaining ecologically clean fruits and potatoes. The biologicals were produced in the Institute of Biology (Latvian AS) by K. Jegina on basis of regional mushrooms.
Modeling Tyrosinase and Catecholase Activity Using New m-Xylyl-Based Ligands with Bidentate Alkylamine Terminal Coordination
2012
Chemical model systems possessing the reactivity aspects of both tyrosinase and catechol oxidase are presented. Using two m-xylyl-based ligands providing bidentate alkylamine terminal coordination, 1,3-bis[(N,N-dimethylaminoethyl)aminomethyl]benzene (L(H,H)) and 1,3-bis[(N,N,N'-trimethylaminoethyl)aminomethyl]benzene (L(Me,Me)), four new dicopper(I) complexes, [Cu(I)(2)(L(H,H))(MeCN)(4)][ClO(4)](2) (1), [Cu(I)(2)(L(H,H))(PPh(3))(2)(MeCN)(2)][ClO(4)](2) (2), [Cu(I)(2)(L(Me,Me))(MeCN)(2)][ClO(4)](2) (3), and [Cu(I)(2)(L(Me,Me))(PPh(3))(2)][ClO(4)](2) (4), have been synthesized and characterized. Complex 2 has been structurally characterized. Reaction of the dicopper(I) complex 3(2+) with diox…