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21.
K-doping dependence of the Fermi surface of the iron-arsenic Ba1-xKxFe2As2 superconductor using angle-resolved photoemission spectroscopy 总被引:1,自引:0,他引:1
Liu C Samolyuk GD Lee Y Ni N Kondo T Santander-Syro AF Bud'ko SL McChesney JL Rotenberg E Valla T Fedorov AV Canfield PC Harmon BN Kaminski A 《Physical review letters》2008,101(17):177005
We use angle-resolved photoemission spectroscopy to investigate the electronic properties of the newly discovered iron-arsenic superconductor Ba_(1-x)K_(x)Fe_(2)As_(2) and nonsuperconducting BaFe_(2)As_(2). Our study indicates that the Fermi surface of the undoped, parent compound BaFe_(2)As_(2) consists of hole pocket(s) at Gamma (0,0) and larger electron pocket(s) at X (1,0), in general agreement with full-potential linearized plane wave calculations. Upon doping with potassium, the hole pocket expands and the electron pocket becomes smaller with its bottom approaching the chemical potential. Such an evolution of the Fermi surface is consistent with hole doping within a rigid-band shift model. Our results also indicate that the full-potential linearized plane wave calculation is a reasonable approach for modeling the electronic properties of both undoped and K-doped iron arsenites. 相似文献
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Mark T McAuley Rose Anne Kenny Thomas BL Kirkwood Darren J Wilkinson Janette JL Jones Veronica M Miller 《BMC neuroscience》2009,10(1):26
Background
The hippocampus is essential for declarative memory synthesis and is a core pathological substrate for Alzheimer's disease (AD), the most common aging-related dementing disease. Acute increases in plasma cortisol are associated with transient hippocampal inhibition and retrograde amnesia, while chronic cortisol elevation is associated with hippocampal atrophy. Thus, cortisol levels could be monitored and managed in older people, to decrease their risk of AD type hippocampal dysfunction. We generated an in silicomodel of the chronic effects of elevated plasma cortisol on hippocampal activity and atrophy, using the systems biology mark-up language (SBML). We further challenged the model with biologically based interventions to ascertain if cortisol associated hippocampal dysfunction could be abrogated. 相似文献27.
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Relevant equivalent circuit parameters and values of material constants of a piezoelectric resonator can be determined from measurements of its electrical input impedance as a function of frequency. The complex electrical impedance curves and the associated critical frequencies are the basis of this characterization by the piezoelectric resonance method. In this paper, the previously introduced concept of normalized electrical impedance of the lossy resonator, extended to include piezoelectric losses, is applied to the analysis of the effects of different types of intrinsic losses on peak values, bandwidths and characteristic frequencies. The resulting impedance patterns depend solely on the electromechanical coupling coefficient and the loss tangents, providing a useful tool for the analysis of low-Q resonators. The normalized impedance is experimentally evaluated from the basic data provided by an HP 4194A impedance analyser by means of specifically developed ASP programs. 相似文献
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A. Bostwick T. Ohta J. L. McChesney T. Seyller K. Horn E. Rotenberg 《The European physical journal. Special topics》2007,148(1):5-13
We have determined the electronic bandstructure of clean and potassium-doped single layer graphene, and fitted the
graphene π
bands to a one- and three-near-neighbor tight binding model. We characterized the quasiparticle dynamics using angle resolved
photoemission spectroscopy. The dynamics reflect the interaction between holes and collective excitations, namely plasmons,
phonons, and electron-hole pairs. Taking the topology of the bands around the Dirac energy for n-doped graphene into account,
we compute the contribution to
the scattering lifetimes due to electron-plasmon and electron phonon coupling. 相似文献
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Three known furanocoumarins, imperatorin (1), wampetin (dehydroindicolactone) (2) and 8-geranoxypsoralen (3) and a new sesquiterpene ketone, (+)-oplopanone (4), were isolated from Clausena lansium Skeels. The stereochemistry of the last two coumarins was determined by NOESY experiments. The idendity of (+)-oplopanone was established by comparison of its physical constants and spectroscopic data with those reported for its enantiomer as well as a comparison of its' TLC behavior with that of an authentic sample. 相似文献