Search results for "ALLOYS"
showing 10 items of 1689 documents
La conducta prosocial como factor protector de los problemas de adicción al juego en universitarios
2020
espanolEsta investigacion busca analizar las variables implicadas en la conducta prosocial y la capacidad de esta para actuar como un factor protector frente a los problemas de adiccion al juego. Este estudio es de tipo cuantitativo, descriptivo, transversal y correlacional. La muestra se compuso por 258 adultos jovenes universitarios (59.5% mujeres) con una edad media de 20.95 anos (DE= 2.19). Se aplicaron cuestionarios (Brief Resilient Coping Scale, cuestionario de apoyo social, Escala de Prosocialidad y South Oaks Gambling Screen) para medir las variables implicadas y realizo un modelo de ecuaciones estructurales. Los resultados mostraron buenos indices de ajuste (X2(41)= 59.31, p= .06; …
Complementarity of the XRF and LIBS analyses in the conservation science: the case studies of the bronze alloys
2011
The present study confirms how the integrated use of non-destructive or micro-destructive spectroscopic techniques are capable to provide a clear response to the investigative needs in the conservation science. In particular, the X-ray fluorescence analysis in association with laser-induced breakdown spectroscopy can be useful for collecting information about chemical composition and elemental stratigraphic distribution of the external layers. The complementarity of these techniques has been tested by analysing bronze samples, made in the laboratory according to binary, ternary and quaternary alloys, typical of Roman archaeometallurgical production and buried for one year. The findings have…
Langmuir films and Langmuir-Blodgett multilayers incorporating mechanically-threaded molecules-pseudorotaxanes
1996
This paper describes the synthesis of a π-electron rich aromatic lipid containing a polyether thread intercepted by a 1,5-dioxynaphthalene moiety. The terminus of one end of the polyether is a methoxyl group and the other a glycerol unit linked via the 2-oxo position, while the 1,3-oxo functions are covalently attached to octadecyl chains. This compound, when cospread at the air-water interface with the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), and the phospholipid, dimyristoylphosphatidic acid, as its monoanion, forms self-assembled pseudorotaxanes which are self-organized into a two-dimensional supramolecular array at the interface. The electrostatic interactions between t…
Polyoxometalates in Langmuir–Blodgett films: toward new magnetic materials
1998
Abstract Polyoxometalates having various structures and properties can be organized by the Langmuir–Blodgett (LB) technique. The adsorption of such polyanions along a positively charged monolayer of DODA (dimethyldioctadecylammonium) induces large changes in the compression isotherm and enables the transfer of the Langmuir film onto solid substrate. X-ray diffraction and infrared dichroism experiments demonstrate that the polyoxometalates are organized in monolayers within the LB films. Furthermore, these magnetic multilayers were characterized by their paramagnetic susceptibility measured by a SQUID magnetometer.
Magnetic properties of AgLnSe2 compounds (Ln=Ho, Er, Tm and Yb)
2001
Abstract The heavy lanthanide selenides AgLnSe2 (Ln=Ho–Yb) crystallize in the orthorhombic AgErSe2 type structure (P212121). The lanthanide ions are placed in the centres of slightly distorted octahedra, whereas each of the silver ions is surrounded by four selenide ions forming a strongly distorted tetrahedron. The high field magnetization (up to 14 T) and the magnetic susceptibility were measured on the polycrystalline samples. The crystal field parameters were estimated from the field dependences of the magnetizations, assuming a rhombic distortion of LnSe6 octahedra. The magnetic susceptibilities were also calculated using the same set of the crystal field parameters. None of the compou…
Synthesis and X-ray crystal structure of cationic polynuclear hydroxide acetylacetonate lanthanide(III) clusters with homodinuclear or heterodinuclea…
2006
The synthesis and characterization of new polynuclear lanthanide(III) ionic clusters of general formula [Ln 9 (acac) 16 (OH) 10 ] + [Mo 2 (CO) 10 (μ-H)]- (Ln = Sm, Eu, Gd, Dy, Yb) and [Sm 9 (acac) 16 OH) 10 ] + [CrW(CO) 10 (μ-H)] - is reported. The polynuclear complexes, prepared under pure nitrogen atmosphere by interaction of the hydridic metal carbonyls with the β-dichetonate Ln(acac) 3 ·3H 2 O (Ln=Sm, Eu, Gd, Dy, Yb). The new clusters were characterized by elemental analysis, complexometric titration for Ln, atomic absorption for Cr, W and Mo, gas-volumetric analysis for CO, FTIR spectroscopy and single crystal X-ray structure determination of [Sm 9 (acac) 16 (OH) 10 ][Mo 2 (CO) 10 (μ-H…
Synthesis and Chemical physical characterization of a new series of hydroxil, acetylacetonate lanthanide (III) – ditungsten decacarbonyl hydride comp…
2004
A novel series of the heterometallic lanthanide(III) ionic cluster complexes of general formula Ln 9 (acac) 16 (OH) 10 [W 2 (CO) 10 (μ-H)] with Ln = Sm (la), Eu (1b), Gd (1c), Dy (1d), and Yb (le) was prepared and characterized by FTIR, 1 H NMR spectroscopy and single crystal X-ray analysis. The cluster series was obtained by reaction in ethanol solution of the 2,4-pentanedionate hydrate of lanthanide(III), Ln(acac) 3 .3H 2 O, with the hydridic ditungsten decacarbonyl, [W 2 (CO) 10 (μ-H)] - . X-ray analysis showed that the complexes la-le are isostructural. The complete structural characterization of the Eu derivative (1b) shows, similarly to their chromium derivative analogues, a square an…
Hybrid organic-inorganic mononuclear lanthanoid single ion magnets
2019
The first family of hybrid mononuclear organic-inorganic lanthanoid complexes is reported, based on [PW11O39]7− and 1,10-phenanthroline ligands. This hybrid approach causes a dramatic improvement of the relaxation time (×1000) with a decrease of the optimal field while maintaining the Ueff of the inorganic analogues.
Extended dipyrrin ligands : candidates for optical metal ion detection under competitive conditions
2017
Acylhydrazone based extended dipyrrins L1-H and L2-H are introduced as complexometric ppb sensitive metal ion detectors. The binding of lanthanide, transition as well as post-transition metal ions is followed by UV-Vis measurements. The carbohydrate based ligand L2 is water soluble and thus can act as a metal ion sensor in this medium.
Full multiple scattering analysis of X-ray absorption near edge structure at the Eu L3-edge in EuO
2004
Abstract X-ray absorption near edge structure (XANES) at the Eu L 3 -edge in crystalline EuO is interpreted within full multiple scattering (FMS) formalism. Our theoretical results, based on the ab initio self-consistent (SC) potential calculations, are in good agreement with experimental data. The main features in the experimental signal are reproduced taking into account a cluster of about five coordination shells, centred at the europium atom and having EuO structure. An addition of more distant coordination shells makes features only better resolved. The relatively high intensity of the peak, located just above the Eu L 3 -edge, indicates that 5d states are well localised. Comparative a…