- Desorption characteristics of rare earth (R) hydrides (R=Y, Ce, Pr, Nd, Sm, Gd and Tb) in relation to the HDDR behaviour of R-Fe-based-compounds
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Vacuum desorption characteristics of binary hydrides of rare earth metals (R=Ce, Pr, Nd, Y, Sm, Gd, Tb) were studied. A complete decomposition of hydrides, confirmed by X-ray diffraction, was achieved at temperatures up to 820°C. When heating the hydrogenated material in vacuum, two distinct hydrogen desorption events were observed for all the hydrides under investigation. The hydrogen desorption behaviour is different for the two groups of metals, namely group I (Ce, Pr and Nd) and group II (Y, Sm, Gd and Tb). The hydrogenation-disproportionation-desorption-recombination (HDDR) process was shown to take place for the Nd6Fe13Ge and Nd6Fe12.8Ga1.2 intermetallic compounds, both with the Nd6Fe13Si-type structure. The hydrogen absorption and desorption properties of these compounds were studied in relation to the desorption characteristics of neodymium hydride.
- Yartys,Gutfleisch,Panasyuk,Harris
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- Cathodic behaviour of samarium(III) in LiF-CaF2 media on molybdenum and nickel electrodes
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The electrochemical behaviour of SmF3 is examined in molten LiF-CaF2 medium on molybdenum and nickel electrodes. A previous thermodynamic analysis suggests that the reduction of SmF3 into Sm proceeds according to a two-step mechanism:SmIII + e- = SmIISmII + 2e- = Sm The second step occurs at a potential lower than the reduction potential of Li+ ions. Cyclic voltammetry, chronopotentiometry and square-wave voltammetry were used to confirm this mechanism and the results show that it was not possible to produce samarium metal in molten fluorides on an inert cathode (molybdenum) without discharging the solvent. The electrochemical reduction of SmF3 is limited by the diffusion of SmF3 in the solution. The diffusion coefficient was calculated at different temperatures and the values obtained obey Arrhenius' law. For the extraction of the samarium from fluoride media, the use of a reactive cathode made of nickel leading to samarium-nickel alloys is shown to be a pertinent route. Cyclic voltammetry and open-circuit chronopotentiometry were used to identify and to characterise the formation of three alloys: liquid Sm3Ni and a compact layer made of SmNi 3 and SmNi2.
- Massot,Chamelot,Taxil
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- Synthesis and theoretical analysis of samarium nanoparticles: Perspectives in nuclear medicine
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The use of lanthanides as radionuclides in nuclear medicine is well-known, because they can be used for detecting and treating cancerous tumors. Due to the fact that the doses are directly related to the number of unstable atoms involved, the possibility of obtaining controlled-size lanthanide nanoparticles opens a wide scope for their application in nuclear medicine. In this work, we report the synthesis of anew samarium nanoparticle by using the bioreduction method, where the pH conditions play an important role in the size control of the produced clusters. The nanoparticles were characterized by using an transmission electron microscope, in addition to the use of a quantum mechanical method to relate the atomic and electronic structures to the chemical selectivity, which allows us to predict a direct coordination between the DTPA-bis-biotin molecules with the samarium nanoparticles larger than 55 atoms. This work involves experimental and theoretical methods to propose a totally new application for nanotechnology in nuclear medicine.
- Ascencio, Jorge A.,Rincon, Ana C.,Canizal, Gerardo
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- Sm2O2I - A new mixed-valence samarium(II,III) oxide halide
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Dark red single crystals of Sm2O2I were obtained from a reaction of SmI2 (in the presence of SmOI) and Na in a sealed tantalum ampoule at 650 °C. The title compound crystallizes in the monoclinic system (C2/m, Z = 4, a = 12.639(2), b = 4.100(1), c = 9.762(3) A, β = 117.97(2)°). The structure consists of corrugated [Sm 2+Sm3+(O2-)2]+ layers of edge and vertex-connected Sm4O tetrahedral units with I- anions separating the layers.
- Ryazanov, Mikhail,Hoch, Constantin,Mattausch, Hansjuergen,Simon, Arndt
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p. 2385 - 2388
(2008/10/09)
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- Temperature dependent rate constants for the reactions of gas phase lanthanides with N2O
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The reactivity of gas phase lanthanide (Ln) atoms (Ln=La-Yb with the exception of Pm) with N2O from 298 to 623 K is reported. Lanthanide atoms were produced by the photodissociation of Ln(TMHD)3 (TMHD=2,2,6,6-tetramethyl-3,5-heptanat
- Campbell, Mark L.
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p. 562 - 566
(2007/10/03)
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- Temperature-Dependent Rate Constants for the Reactions of Gas-Phase Lanthanides with O2
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The reactivity of the gas-phase lanthanide atoms Ln (Ln = La-Yb with the exception of Pm) with O2 is reported. Lanthanide atoms were produced by the photodissociation of [Ln(TMHD)3] and detected by laser-induced fluorescence. For all the lanthanides studied with the exception of Yb, the reaction mechanism is bimolecular abstraction of an oxygen atom. The bimolecular rate constants (in molecule-1 cm3 s-1) are described in Arrhenius form by k[Ce(1G4)] = (3.0 ± 0.4) × 10-10 exp(-3.4 ± 1.3 kJ mol-1/RT); Pr(4I9/2), (3.1 ± 0.7) × 10-10 exp(-5.3 ± 1.5 kJ mol-1/RT); Nd(5I4), (3.6 ± 0.3) × 10-10 exp(-6.2 ± 0.4 kJ mol-1/RT); Sm(7F0), (2.4 ± 0.4) × 10-10 exp(-6.2 ± 1.5 kJ mol-1/RT); Eu(8S7/2), (1.7 ± 0.3) × 10-10 exp(-9.6 ± 0.7 kJ mol-1/RT); Gd(9D2), (2.7 ± 0.3) × 10-10 exp(-5.2 ± 0.8 kJ mol-1/RT); Tb(6H15/2), (3.5 ± 0.6) × 10-10 exp(-7.2 ± 0.8 kJ mol-1/RT); Dy(5I8), (2.8 ± 0.6) × 10-10 exp(-9.1 ± 0.9 kJ mol-1/RT); Ho(4I15/2), (2.4 ± 0.4) × 10-10 exp(-9.4 ± 0.8 kJ mol-1/RT); Er(3H6), (3.0 ± 0.8) × 10-10 exp(-10.6 ± 1.1 kJ mol-1/RT); Tm(2F7/2), (2.9 ± 0.2) × 10-10 exp(-11.1 ± 0.4 kJ mol-1/RT), where the uncertainties represent ±2σ. The reaction barriers are found to correlate to the energy required to promote an electron out of the 6s subshell. The reaction of Yb(1S0) with O2 reacts through a termolecular mechanism. The limiting low-pressure third-order rate constants are described in Arrhenius form by k0[Yb(1S0)] = (2.0 ± 1.3) × 10-28 exp(-9.5 ± 2.8 kJ mol-1/RT) molecule-2 cm6 s-1.
- Campbell, Mark L.
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p. 7274 - 7279
(2007/10/03)
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- Optically active aminoalcohol derivatives and method of producing same
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An object of the present invention is to provide a safe method of commercially producing optically active aminoalcohol derivatives, which serve as intermediates for the synthesis of medicinal chemicals such as the immunopotentiating anticancer agent bestatin, in a simple and easy manner in high yields and with high levels of selectivity. The present invention consists in a method of producing 3-amino-1-nitro-4-phenyl-2-butanol derivatives of the general formula (1) STR1 wherein R1 and R2 each independently represents a hydrogen atom or an amino group protecting group, and a method of producing 3-amino-2-hydroxy-4-phenylbutyric acid derivatives derivable therefrom.
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- THERMODYNAMICS OF VAPORIZATION AND FORMATION OF SAMARIUM(III) OXIDE TELLURIDE.
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The thermal decomposition of solid samarium(III) oxide telluride (SmO)//2Te was studied over the temperature range 1788-1972 K by the Knudsen effusion weight-loss technique. The compound decomposes to yield B-Sm//2O//3(s) and a gas phase containing samarium and tellurium in a molar ratio of 2:3. Using enthalpy and entropy data from the literature for gaseous Sm, Te, SmTe and Te//2, it could be established from thermodynamic calculations that, within the given temperature range, samarium and tellurium are the principal vapour species in equilibrium with solid (SmO)//2Te and B-Sm//2O (monoclinic modification), while SmTe and Te//2 are of minor and very minor importance respectively.
- Petzel,Ludwigs
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p. 241 - 247
(2008/10/08)
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