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31.
Olea-Azar C Rigol C Mendizábal F Briones R Cerecetto H Di Maio R Risso M González M Porcal W 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(1):69-74
The electron spin resonance (ESR) spectra of free radicals obtained by electrolytic or microsomal reduction of several potential antiprotozoal 1,2,5-oxadiazoles were characterized and analyzed. Ab initio molecular orbital calculations were performed to obtain the optimized geometries and the theoretical hyperfine constant was carried out using ZINDO semiempirical methodology. Density functional theory was used to rationalize the reduction potentials of these compounds. 相似文献
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D. Jaque J. I. Martín G. Armelles J. L. Costa-Krmer F. Briones J. L. Vicent 《Journal of magnetism and magnetic materials》2002,240(1-3):37-39
In-plane magneto optical hysteresis loops have been used to determine the magnetic axes distribution of crystalline Fe (0 0 1) micrometric squares of different sizes (2.5–10 μm) and separations (0.2 and 0.6 μm). The angular dependence of the magnetization at remanence shows the interplay between the anisotropy of the unpatterned Fe thin film and the anisotropies induced by the patterning process. A rich variety of behaviors are found when the arrays of squares are rotated with regard to the Fe main crystalline directions. 相似文献
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F. Briones L. González A. Ruiz 《Applied Physics A: Materials Science & Processing》1989,49(6):729-737
A new development of molecular beam epitaxy (MBE) for III–V compounds is described, based on cyclic perturbation of the growth front at atomic layer level by periodic pulsing, alternating or interrupting the molecular beams. The modification of the growth mechanism caused by this perturbations is discussed and related to periodic changes of surface stoichiometry which induce 2D growth mechanism by enhanced layer nucleation.Under appropriate modulation conditions, an atomic layer by layer growth mode can be achieved. A practical implementention of this mode, that we denote atomic layer MBE (ALMBE), is considered in which only group V beams are pulsed in a specially designed effusion cell. A number of growth applications of ALMBE are presented, including growth of highly mismatched heterostructures and short period superlattices containing two different group V elements such as arsenic and phosphorous. 相似文献
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C. Rigol C. Olea-Azar F. Mendizbal R. Briones H. Cerecetto M. Gonzlez 《Journal of Molecular Structure》2006,770(1-3):125-129
Theoretical studies of molecular conformations and electronic properties calculations of eight 5-nitrofuryl thiosemicarbazone free radicals, by means of ab initio (R/UHF), and DFT (R/UB3LYP) methods are presented and discussed in comparison with ESR and electrochemical experimental data. DFT calculated hyperfine coupling constants were used for the simulation of experimental spectra. We observed the molecules adopt mainly two conformations, both showing a pattern of spin density delocalization unusual for free radicals formed from aromatic nitrocompounds. Energy potential surfaces scaning through a determined dihedral angle were drawn to evaluate whether these conformations could coexist in equilibrium. Fukui and molecular orbital analysis were compared with ESR data as reactivity local indexes. 相似文献
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García MA Ruiz-González ML Quesada A Costa-Krämer JL Fernández JF Khatib SJ Wennberg A Caballero AC Martín-González MS Villegas M Briones F González-Calbet JM Hernando A 《Physical review letters》2005,94(21):217206
In this Letter, we experimentally show that the room temperature ferromagnetism in the Mn-Zn-O system recently observed is associated with the coexistence of Mn(3+) and Mn(4+) via a double-exchange mechanism. The presence of the ZnO around MnO(2) modifies the kinetics of MnO(2)-->Mn(2)O(3) reduction and favors the coexistence of both Mn oxidation states. The ferromagnetic phase is associated with the interface formed at the Zn diffusion front into Mn oxide, corroborated by preparing thin film multilayers that exhibit saturation magnetization 2 orders of magnitude higher than bulk samples. 相似文献
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