167 research outputs found
Huge Seebeck coefficients in non-aqueous electrolytes
The Seeebeck coefficients of the non-aqueous electrolytes tetrabutylammonium
nitrate, tetraoctylphosphonium bromide and tetradodecylammonium nitrate in
1-octanol, 1-dodecanol and ethylene-glycol are measured in a temperature range
from T=30 to T=45 C. The Seebeck coefficient is generally of the order of a few
hundreds of microvolts per Kelvin for aqueous solution of inorganic ions. Here
we report huge values of 7 mV/K at 0.1M concentration for tetrabutylammonium
nitrate in 1-dodecanol. These striking results open the question of
unexpectedly large kosmotrope or "structure making" effects of
tetraalkylammonium ions on the structure of alcohols.Comment: Submitted to J. Chem. Phy
Non-generality of the Kadowaki-Woods ratio in correlated oxides
An explicit expression for the Kadowaki-Woods ratio in correlated metals is
derived by invoking saturation of the (high-frequency) Fermi-liquid scattering
rate at the Mott-Ioffe-Regel limit. Significant deviations observed in a number
of oxides are quantitatively explained due to variations in carrier density,
dimensionality, unit cell volume and the number of individual sheets in the
Brillouin zone. A generic re-scaling of the original Kadowaki-Woods plot is
also presented.Comment: 9 pages of text, 1 table, 2 figure
Optical and Thermal-Transport Properties of an Inhomogeneous d-Wave Superconductor
We calculate transport properties of disordered 2D d-wave superconductors
from solutions of the Bogoliubov-de Gennes equations, and show that weak
localization effects give rise to a finite frequency peak in the optical
conductivity similar to that observed in experiments on disordered cuprates. At
low energies, order parameter inhomogeneities induce linear and quadratic
temperature dependencies in microwave and thermal conductivities respectively,
and appear to drive the system towards a quasiparticle insulating phase.Comment: 5 pages,3 figure
Absence of residual quasiparticle conductivity in the underdoped cuprate YBa2Cu4O8
We report here measurements of the in-plane thermal conductivity K(T) of the
underdoped cuprate YBa2Cu4O8 (Y124) below 1K. K(T) is shown to follow a simple,
phononic T^3 dependence at the lowest temperatures for both current directions,
with a negligible linear, quasiparticle contribution. This observation is in
marked contrast with behavior reported in optimally doped cuprates, and implies
that extended zero-energy (or low energy) low-energy quasiparticles are absent
in YBa2Cu4O8 at low temperatures.Comment: RevTex, 4 pages, 2 figures, Revised versio
Low-temperature electronic heat transport in La_{2-x}Sr_{x}CuO_{4} single crystals: Unusual low-energy physics in the normal and superconducting states
The thermal conductivity \kappa is measured in a series of
La_{2-x}Sr_{x}CuO_{4} (x = 0 - 0.22) single crystals down to 90 mK to elucidate
the evolution of the residual electronic thermal conductivity \kappa_{res},
which probes the extended quasiparticle states in the d-wave gap. We found that
\kappa_{res}/T grows smoothly, except for a 1/8 anomaly, above x = 0.05 and
shows no discontinuity at optimum doping, indicating that the behavior of
\kappa_{res}/T is not governed by the metal-insulator crossover in the normal
state; as a result, \kappa_{res}/T is much larger than what the normal-state
resistivity would suggest in the underdoped region, which highlights the
peculiarities in the low-energy physics in the cuprates.Comment: 5 pages, 3 figures, final version published in PRL. Discussions have
been modified and an analysis of the phonon term has been adde
Double bundle arthroscopic Anterior Cruciate Ligament reconstruction with remnant preserving technique using a hamstring autograft
<p>Abstract</p> <p>Background</p> <p>Preservation of the Anterior Cruciate Ligament (ACL) remnant is important from the biological point of view as it enhances revascularization, and preserves the proprioceptive function of the graft construct. Additionally, it may have a useful biomechanical function. Double bundle ACL reconstruction has been shown to better replicate the native ACL anatomy and results in better restoration of the rotational stability than single bundle reconstruction.</p> <p>Methods</p> <p>We used the far anteromedial (FAM) portal for creation of the femoral tunnels, with a special technique for its preoperative localization using three dimensional (3D) CT. The central anteromedial (AM) portal was used to make a longitudinal slit in the ACL remnant to allow visualization of the tips of the guide pins during anatomical creation of the tibial tunnels within the native ACL tibial foot print. The use of curved hemostat allow retrieval of the wire loop from the apertures of the femoral tunnels through the longitudinal slit in the ACL remnant thereby, guarding against impingement of the reconstruction graft against the ACL remnant as well as the roof of the intercondylar notch.</p> <p>Conclusion</p> <p>Our technique allows for anatomical double bundle reconstruction of the ACL while maximally preserving the ACL remnant without the use of intra-operative image intensifier.</p
Thermal Conductivity across the Phase Diagram of Cuprates: Low-Energy Quasiparticles and Doping Dependence of the Superconducting Gap
Heat transport in the cuprate superconductors YBaCuO and
LaSrCuO was measured at low temperatures as a function of
doping. A residual linear term kappa_{0}/T is observed throughout the
superconducting region and it decreases steadily as the Mott insulator is
approached from the overdoped regime. The low-energy quasiparticle gap
extracted from kappa_{0}/T is seen to scale closely with the pseudogap. The
ubiquitous presence of nodes and the tracking of the pseudogap shows that the
overall gap remains of the pure d-wave form throughout the phase diagram, which
excludes the possibility of a complex component (ix) appearing at a putative
quantum phase transition and argues against a non-superconducting origin to the
pseudogap. A comparison with superfluid density measurements reveals that the
quasiparticle effective charge is weakly dependent on doping and close to
unity.Comment: 12 pages, 9 figure
Real spin glasses relax slowly in the shade of hierarchical trees
The Parisi solution of the mean-field spin glass has been widely accepted and
celebrated. Its marginal stability in 3d and its complexity however raised the
question of its relevance to real spin glasses. This paper gives a short
overview of the important experimental results which could be understood within
the mean-field solution. The existence of a true phase transition and the
particular behaviour of the susceptibility below the freezing temperature,
predicted by the theory, are clearly confirmed by the experimental results. The
behaviour of the complex order parameter and of the Fluctuation Dissipation
ratio are in good agreement with results of spontaneous noise measurements. The
very particular ultrametric symmetry, the key feature of the theory, provided
us with a simple description of the rejuvenation and memory effects observed in
experiment. Finally, going a step beyond mean-field, the paper shortly
discusses new analyses in terms of correlated domains characterized by their
length scales, as well as new experiments on superspin glasses which compare
well with recent theoretical simulations.Comment: To appear in the proceedings of "Wandering with Curiosity in Complex
Landscapes", a scientific conference in honour of Giorgio Parisi for his 60th
birthday, Roma, September 8-10 2008 (submitted for the special issue of the
Journal of Statistical Physics, 2009
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