26 research outputs found
Temperature range of superconducting fluctuations above T_c in YBa_2Cu_3O_{7-\delta} single crystals
Microwave absorption measurements in magnetic fields from zero up to 16 T
were used to determine the temperature range of superconducting fluctuations
above the superconducting critical temperature T_c in YBa_2Cu_3O_{7-\delta}.
Measurements were performed on deeply underdoped, slightly underdoped, and
overdoped single crystals. The temperature range of the superconducting
fluctuations above T_c is determined by an experimental method which is free
from arbitrary assumptions about subtracting the nonsuperconducting
contributions to the total measured signal, and/or theoretical models to
extract the unknown parameters. The superconducting fluctuations are detected
in the ab-plane, and c-axis conductivity, by identifying the onset temperature
T'. Within the sensitivity of the method, this fluctuation regime is found only
within a fairly narrow region above T_c. Its width increases from 7 K in the
overdoped sample (T_c = 89 K), to at most 23 K in the deeply underdoped sample
(T_c = 57 K), so that T' falls well below the pseudogap temperature T*.
Implications of these findings are discussed in the context of other
experimental probes of superconducting fluctuations in the cuprates
Recent developments in the characterization of superconducting films by microwaves
We describe and analyze selected surface impedance data recently obtained by
different groups on cuprate, ruthenate and diboride superconducting films on
metallic and dielectric substrates for fundamental studies and microwave
applications. The discussion includes a first review of microwave data on MgB2,
the weak-link behaviour of RABiTS-type YBa2Cu3O7-d tapes, and the observation
of a strong anomalous power-dependence of the microwave losses in MgO at low
temperatures. We demonstrate how microwave measurements can be used to
investigate electronic, magnetic, and dielectric dissipation and relaxation in
the films and substrates. The impact of such studies reaches from the
extraction of microscopic information to the engineering of materials and
further on to applications in power systems and communication technology.Comment: Invited contribution to EUCAS2001, accepted for publication in
Physica C in its present for
Magneto-Transport Properties of Doped RuSrGdCuO
RuSrGdCuO, in which magnetic order and superconductivity coexist
with , is a complex material which poses new and
important questions to our understanding of the interplay between magnetic and
superconducting (SC) order. Resistivity, Hall effect and thermopower
measurements on sintered ceramic RuSrGdCuO are presented, together
with results on a broad range of substituted analogues. The Hall effect and
thermopower both show anomalous decreases below which may be
explained within a simple two-band model by a transition from localized to more
itinerant behavior in the RuO layer at .Comment: 10 pages, 7 figures, submitted to Phys. Rev. B., correspondence to
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The characteristics of the superconducting and magnetic phases in the polycrystalline samples of ruthenocuprates of nominal compositions RuSr2GdCu2O8, Ru0.98Sr2GdCu2O8 and Ru0.5Sr2GdCu2.5O8-d
The temperature dependencies of the resistivity for the superconducting
ruthenocuprates of nominal compositions RuSr2GdCu2O8, Ru0.98Sr2GdCu2O8 and
Ru0.5Sr2GdCu2.5O8-d were examined for the magnetic field dependent
characteristics of the superconducting transitions. The effect of the
insignificant diminishing of the Ru/Cu ratio in parent RuSr2GdCu2O8 was
confirmed as relevant for the stabilisation of the superconducting phase. Noted
differences in the compared characteristics are interpreted for possible
inhomogeneous nucleation of the superconducting phase in the parent
ruthenocuprate. The phase anisotropy in RuSr2GdCu2O8 and Ru0.98Sr2GdCu2O8 , in
presence of the compounds Ru magnetism, appears to be a cause of a significant
softening of the Hc2(T) phase line. An anomalous lowering of the
magneto-resistivity was observed in the approx. 10 K range above the onset of
the superconducting transition, which may suggest the presence of enhanced
superconducting fluctuations in the samples. The positive magnetic field shift
of the temperatures, which limit the magneto-resistivity and the specific heat
signatures of the magnetic ordered state of the Ru sub-lattice, suggests
probing the influence of the ferromagnetic Ru interactions in an effective
metallic-like conduction channel present in the samples. Superconducting
characteristics of the Ru0.5Sr2GdCu2.5O8-d reveal a significant contribution of
the Gd paramagnetic signal at low temperatures, interpreted for the presence of
a significant anisotropy of the superconducting phase. It is concluded that the
Ru-Cu substituted phases of ruthenocuprates may present an opportunity to
investigate the effectively anisotropic superconducting phase despite its
comparatively high Tc in the compounds related to the 123-type cuprate
superconductor.Comment: 12 pages, 9 figures, accepted for publicatio
Recommendations for effective documentation in regional anesthesia: an expert panel Delphi consensus project
Background and objectives: Documentation is important for quality improvement, education, and research. There is currently a lack of recommendations regarding key aspects of documentation in regional anesthesia. The aim of this study was to establish recommendations for documentation in regional anesthesia.
Methods: Following the formation of the executive committee and a directed literature review, a long list of potential documentation components was created. A modified Delphi process was then employed to achieve consensus amongst a group of international experts in regional anesthesia. This consisted of 2 rounds of anonymous electronic voting and a final virtual round table discussion with live polling on items not yet excluded or accepted from previous rounds. Progression or exclusion of potential components through the rounds was based on the achievement of strong consensus. Strong consensus was defined as ≥75% agreement and weak consensus as 50%-74% agreement.
Results: Seventy-seven collaborators participated in both rounds 1 and 2, while 50 collaborators took part in round 3. In total, experts voted on 83 items and achieved a strong consensus on 51 items, weak consensus on 3 and rejected 29.
Conclusion: By means of a modified Delphi process, we have established expert consensus on documentation in regional anesthesia
Depolarization crossovers in the microwave response of silicon crystals in slab geometry
Microwave cavity perturbation measurements have been performed on several n-type silicon samples with different depolarization factors due to sample geometries. The general solution for the complex frequency shift in slab geometry is discussed for the specific case of semiconductors. The depolarization crossovers predicted by the theory have been experimentally observed. Their relative intensities suggest that the imaginary part of the complex conductivity of semiconductors has to be taken into account. Electron scattering time has been inferred from the microwave measurements
NMR relaxometric properties and cytotoxicity of Gd2O3 nanoparticle suspensions in an organic liquid
Gd2O3 nanoparticles and their agglomerates from approximately 10 to 80 nm in size suspended in an organic liquid were synthesized via polyol route. The reaction between diethylene glycol and added acetic acid, which occurred simultaneously with the synthesis of Gd2O3 nanoparticles, was catalyzed by sodium bisulfate to transform as much as possible diethylene glycol in corresponding ester at the end of complete reaction. The produced nanosized material of gadolinium oxide was investigated by TEM, DLS, FTIR spectroscopy, and NMR relaxometry. Biological evaluation of this material was done by MTT and crystal violet assays to determine the cell viability. Longitudinal and transverse relaxivities of water-diluted Gd2O3 nanoparticle suspensions estimated to be r(1) = 13.6 and r(2) = 14.7 s(-1) mM(-1) are about three times higher compared to the relaxivities obtained for standard contrast agent Gd-DTPA (Magnevist). Good MRI signal intensities of the water-diluted Gd2O3 nanoparticle suspensions were recorded in the Gd concentration range 0.2-0.3 mM for which the suspensions were not toxic exhibiting simultaneously higher signal intensities than those for Magnevist in the Gd concentration range 0.4-1 mM for which this standard contrast agent was not toxic. These properties make the produced Gd2O3 nanoparticle material promising for potential application as MRI contrast agent