262 research outputs found
Hole concentration and phonon renormalization in Ca-doped YBa_2Cu_3O_y (6.76 < y < 7.00)
In order to access the overdoped regime of the YBa_2Cu_3O_y phase diagram, 2%
Ca is substituted for Y in YBa_2Cu_3O_y (y = 7.00,6.93,6.88,6.76). Raman
scattering studies have been carried out on these four single crystals.
Measurements of the superconductivity-induced renormalization in frequency
(Delta \omega) and linewidth (\Delta 2\gamma) of the 340 cm^{-1} B_{1g} phonon
demonstrate that the magnitude of the renormalization is directly related to
the hole concentration (p), and not simply the oxygen content. The changes in
\Delta \omega with p imply that the superconducting gap (\Delta_{max})
decreases monotonically with increasing hole concentration in the overdoped
regime, and \Delta \omega falls to zero in the underdoped regime. The linewidth
renormalization \Delta 2\gamma is negative in the underdoped regime, crossing
over at optimal doping to a positive value in the overdoped state.Comment: 18 pages; 5 figures; submitted to Phys. Rev. B Oct. 24, 2002 (BX8292
Electronic signature of the vacancy ordering in NbO (Nb3O3)
We investigated the electronic structure of the vacancy-ordered 4d-transition
metal monoxide NbO (Nb3O3) using angle-integrated soft- and hard-x-ray
photoelectron spectroscopy as well as ultra-violet angle-resolved photoelectron
spectroscopy. We found that density-functional-based band structure
calculations can describe the spectral features accurately provided that
self-interaction effects are taken into account. In the angle-resolved spectra
we were able to identify the so-called vacancy band that characterizes the
ordering of the vacancies. This together with the band structure results
indicates the important role of the very large inter-Nb-4d hybridization for
the formation of the ordered vacancies and the high thermal stability of the
ordered structure of niobium monoxide
Nernst Effect and Superconducting Fluctuations in Zn-doped YBaCuO
We report the measurements of in-plane resistivity, Hall effect, and Nernst
effect in Zn doped YBaCuO epitaxial thin films grown
by pulsed laser deposition technique. The pseudogap temperature, ,
determined from the temperature dependence of resistivity, does not change
significantly with Zn doping. Meanwhile the onset temperature () of
anomalous Nernst signal above , which is interpreted as evidence for
vortex-like excitations, decreases sharply as the superconducting transition
temperature does. A significant decrease in the maximum of vortex
Nernst signal in mixed state is also observed, which is consistent with the
scenario that Zn impurities cause a decrease in the superfluid density and
therefore suppress the superconductivity. The phase diagram of ,
, and versus Zn content is presented and discussed.Comment: 6 pages, 5 figures, Latex; v2: to be published in PR
Epitaxial and layer-by-layer growth of EuO thin films on yttria-stabilized cubic zirconia (001) using MBE distillation
We have succeeded in growing epitaxial and highly stoichiometric films of EuO
on yttria-stabilized cubic zirconia (YSZ) (001). The use of the Eu-distillation
process during the molecular beam epitaxy assisted growth enables the
consistent achievement of stoichiometry. We have also succeeded in growing the
films in a layer-by-layer fashion by fine tuning the Eu vs. oxygen deposition
rates. The initial stages of growth involve the limited supply of oxygen from
the YSZ substrate, but the EuO stoichiometry can still be well maintained. The
films grown were sufficiently smooth so that the capping with a thin layer of
aluminum was leak tight and enabled ex situ experiments free from trivalent Eu
species. The findings were used to obtain recipes for better epitaxial growth
of EuO on MgO (001).Comment: 10 pages, 15 figure
Examining the impact of a symptom assessment application on patient-physician interaction among self-referred walk-in patients in the emergency department (AKUSYM): study protocol for a multi-center, randomized controlled, parallel-group superiority trial
Background: Due to the increasing use of online health information, symptom checkers have been developed to provide an individualized assessment of health complaints and provide potential diagnoses and an urgency estimation. It is assumed that they support patient empowerment and have a positive impact on patient-physician interaction and satisfaction with care. Particularly in the emergency department (ED), symptom checkers could be integrated to bridge waiting times in the ED, and patients as well as physicians could take advantage of potential positive effects. Our study therefore aims to assess the impact of symptom assessment application (SAA) usage compared to no SAA usage on the patient-physician interaction in self-referred walk-in patients in the ED population. Methods: In this multi-center, 1:1 randomized, controlled, parallel-group superiority trial, 440 self-referred adult walk-in patients with a non-urgent triage category will be recruited in three EDs in Berlin. Eligible participants in the intervention group will use a SAA directly after initial triage. The control group receives standard care without using a SAA. The primary endpoint is patients’ satisfaction with the patient-physician interaction assessed by the Patient Satisfaction Questionnaire. Discussion: The results of this trial could influence the implementation of SAA into acute care to improve the satisfaction with the patient-physician interaction. Trial registration: German Clinical Trials Registry DRKS00028598. Registered on 25.03.2022
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