527 research outputs found
Cytogenetic evidences on the evolutionary relationships between the tetraploids of the section Rhizomatosae and related diploid species (Arachis, Leguminosae).
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Previous issue date: 2017-07-27bitstream/item/181202/1/Ortiz2017-Article-CytogeneticEvidencesOnTheEvolu.pd
Radial correlation effects on interconfigurational excitations at the end of the lanthanide series. A restricted active space second order perturbation study of Yb2+ and SrCl2:Yb2+
Preliminary Experience With the Use of Electromagnetic Navigation for the Diagnosis of Peripheral Pulmonary Nodules and Enlarged Mediastinal Lymph Nodes
Electromagnetic navigation is a new technique that can be
used with bronchoscopy to obtain samples of small peripheral
nodular lesions and enlarged mediastinal lymph nodes. It is
very versatile in that it enables both transbronchial biopsies
and fine-needle aspiration to be performed. We describe
2 cases in which navigation with the superDimension/
Bronchus system combined with traditional diagnostic
techniques facilitated a definitive diagnosis by bronchoscopy.
Electromagnetic navigation can obviate the need for more
invasive diagnostic procedures such as surgery, thus saving
time and money and avoiding complications
Metal-to-metal charge transfer between dopant and host ions: Photoconductivity of Yb-doped CaF2 and SrF2 crystals
Dopant-to-host electron transfer is calculated using ab initio wavefunction-based embedded cluster methods for Yb/Ca pairs in CaF2 and Yb/Sr pairs in SrF2 crystals to investigate the mechanism of photoconductivity. The results show that, in these crystals, dopant-to-host electron transfer is a two-photon process mediated by the 4fN-15d excited states of Y b2+: these are reached by the first photon excitation; then, they absorb the second photon, which provokes the Y b2+ + Ca2+ (Sr2+) → Y b3+ + Ca+ (Sr+) electron phototransfer. This mechanism applies to all the observed Y b2+ 4f-5d absorption bands with the exception of the first one: Electron transfer cannot occur at the first band wavelengths in CaF2:Y b2+ because the Y b3+-Ca+ states are not reached by the two-photon absorption. In contrast, Yb-to-host electron transfer is possible in SrF2:Y b2+ at the wavelengths of the first 4f-5d absorption band, but the mechanism is different from that described above: first, the two-photon excitation process occurs within the Y b2+ active center, then, non-radiative Yb-to-Sr electron transfer can occur. All of these features allow to interpret consistently available photoconductivity experiments in these materials, including the modulation of the photoconductivity by the absorption spectrum, the differences in photoconductivity thresholds observed in both hosts, and the peculiar photosensitivity observed in the SrF2 host, associated with the lowest 4f-5d bandThis work was partly supported by a grant from Ministerio de Economía y Competitividad, Spain (Dirección General de Investigación y Gestión del Plan Nacional de I+D+i, Grant Nos. MAT2011-24586 and MAT2014-54395-P
Yb2+-doped SrCl2: electronic structure of impurity states and impurity-trapped excitons
5f--5f transitions of U4+ ions in high-field, octahedral fluoride coordination: the Cs2GeF6:U4+ crystal
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