Search results for "metals"
showing 10 items of 2013 documents
Regio- and stereo-selectivity in the intramolecular quenching of the excited benzoylthiophene chromophore by tryptophan
2000
Laser flash photolysis studies on the photobehaviour of a series of bichromophoric derivatives bearing benzoylthiophene and tryptophan groups have shown that the efficiency of the intramolecular quenching process depends on both the stereochemistry of the chiral centers and the relative ketone versus tryptophan orientation. Perez Prieto, Julia, Julia.Perez@uv.es
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; …
Effects of pyrolysis conditions on the porous structure development of date pits activated carbon
2012
International audience; Activated carbons were prepared from biomass of Algerian date pits for developing efficient and cheap adsorbents in the aim to remove heavy metals from waste water. Carbon adsorbents were obtained following two successive treatments: pyrolysis under dry nitrogen flow and physical activation under wet nitrogen flow. Pyrolysis process was optimized by varying some operating parameters such as temperature, nitrogen flow, heating rate and pyrolysis hold time in order to determine their effects on the porous structure development of date pits activated carbon. Chars obtained from pyrolysis process were activated with the same operating conditions (activation temperature o…
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.
Designing biochar properties through the blending of biomass feedstock with metals: Impact on oxyanions adsorption behavior
2018
Metal-blending of biomass prior to pyrolysis is investigated in this work as a tool to modify biochar physico-chemical properties and its behavior as adsorbent. Six different compounds were used for metal-blending: AlCl3, Cu(OH)2, FeSO4, KCl, MgCl2 and Mg(OH)2. Pyrolysis experiments were performed at 400 and 700 °C and the characterization of biochar properties included: elemental composition, thermal stability, surface area and pore size distribution, Zeta potential, redox potential, chemical structure (with nuclear magnetic resonance) and adsorption behavior of arsenate, phosphate and nitrate. Metalblending strongly affected biochars' surface charge and redox potential. Moreover, it incre…
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…
Coexistence of long-range antiferromagnetic order and slow relaxation of the magnetization in the first lanthanide complex of a 1,2,4-benzotriazinyl …
2017
The first lanthanide complex of a 1,2,4-benzotriazinyl radical (1), Dy(1)(tbacac)3 (2, tbacac = 2,2,6,6-tetramethyl-3,5-heptane-dionato), was synthesised and found to have an antiferromagnetically ordered ground state with a metamagnetic phase diagram and a critical field of 0.91 T at 1.85 K. The application of a small dc field revealed the single-molecule magnet behaviour of 2, illustrating the coexistence of long-range antiferromagnetic order and slow relaxation of the magnetization. peerReviewed
Geochemical behaviour of rare earths in Vitis vinifera grafted onto different rootstocks and growing on several soils.
2014
The geochemical behaviour of lanthanides and yttrium (Rare Earth Elements, REEs) has been investigated mainly in geological systems where these elements represent the best proxies of processes involving the occurrence of an interface between different media. This behaviour is assessed according to features recorded in sequences of REE concentrations along the REE series normalised with respect to a reference material. In this study, the geochemical behaviour of REE was investigated in different parts of Vitis vinifera specimens grown off-soil, on soils of different nature and grafted onto several rootstocks in order to evaluate effects induced by these changes. The results indicated that ro…