196,069 research outputs found
Orbital angular momentum structure of an unoccupied spin-split quantum-well state in Pb/Cu(111)
No full textVibron-assisted spin relaxation at a metal/organic interface
No full textInspired by recent experiments for hybrid organic-ferromagnet interfaces, we propose a spin-relaxation mechanism which does not depend on either the spin-orbit or the hyperfine interaction. This takes place when a molecule with initial spin imbalance is weakly coupled to ametal surface and can be excited in various vibrational states. In such a situation the electron-vibron interaction promotes the exchange of spin-polarized electrons between the molecule and the surface, serving as an energy and angular momentum reservoir. This process leads to an effective spin relaxation of the electron population in the molecule. We suggest that this nonequilibrium mechanism can be investigated through time-resolved spin-polarized scanning tunnelingmicroscopy experiments
Electronic and magnetic properties of the interface between metal-quinoline molecules and cobalt
No full textIt was recently established that spin injection from a ferromagnetic metal into an organic semiconductor depends largely on the formation of hybrid interface states. Here we investigate whether the magnetic properties of the interface between cobalt and tris( 8-hydroxyquinolinato)-Al( III) ( Alq3), the most prominent molecular candidate for organicspin-valve devices, can be modified by substituting the aluminum atom with either gallium or indium. The electronic structure of Alq3, Gaq3, and Inq3 and the properties of their interfaces with ferromagnetic cobalt are probed experimentally, by using different photoemission spectroscopy methods, and theoretically, through density functional theory calculations. For all cases, the results highlight the presence of spin-polarized interface states. However no striking difference between the properties of the various molecules and interfaces is observed. This is a consequence of the fact that the molecules frontier orbitals are mainly localized on the ligands and they show only a negligible contribution coming from the metal ion
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Qualitative and quantitative changes of melatonin levels in physiological and pathological aging and in centenarians
No full textMelatonin secretion is an endogenous synchronizer, and it may possess some anti-aging properties. Thus we examined melatonin levels in physiological aging, in extreme senescence and in senile dementia. In healthy old (age 66-94 yr) and young subjects (age 23-39 yr) and in demented patients (age 68-91 yr) plasma melatonin was measured by radioimmunoassay in eight serial blood samples. In centenarians (age 100-107 yr) melatonin levels were estimated by assaying urinary 6-hydroxymelatonin sulfate (aMT6s) in two different urine samples collected from 08:00 to 20:00 hours and from 20:00 to 08:00 hours. These data were compared with the aMT6s excretion of old and young controls. Elderly subjects, demented or not, exhibited a flattened circadian profile of plasma melatonin, because of the suppression of the nocturnal peak. An age-related decline of the circadian amplitude of the melatonin rhythm occurred in old subjects, especially in demented individuals. Furthermore, the melatonin nocturnal peak was significantly correlated with the severity of the cognitive impairment. aMT6s urinary excretion also declined with age. However, as in young controls, in centenarians the aMT6s excretion was significantly higher at night than during the day. In conclusion, pineal melatonin secretion is affected by age and by the degree of cognitive impairment. In centenarians the maintenance of the circadian organization of melatonin secretion may suggest that the amplitude of the nocturnal peak and/or the persistence of a prevalent nocturnal secretion may be an important marker of biological age and of health statu
Ultrafast Amplification and Nonlinear Magnetoelastic Coupling of Coherent Magnon Modes in an Antiferromagnet
No full textWe investigate the role of domain walls in the ultrafast magnon dynamics of an antiferromagnetic NiO single crystal in a pump-probe experiment with variable pump photon energy. Analyzing the amplitude of the energy-dependent photoinduced ultrafast spin dynamics, we detect a yet unreported coupling between the material’s characteristic terahertz- and gigahertz-magnon modes. We explain this unexpected coupling between two orthogonal eigenstates of the corresponding Hamiltonian by modeling the magnetoelastic interaction between spins in different domains. We find that such interaction, in the nonlinear regime, couples the two different magnon modes via the domain walls and it can be optically exploited via the exciton-magnon resonance
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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