1,274 research outputs found
Charge dynamics of the Co-doped BaFeAs
We report on a thorough optical investigation over a broad spectral range and
as a function of temperature of the charge dynamics in
Ba(CoFe)As compounds for Co-doping ranging between 0 and
18%. For the parent compound as well as for =0.025 we observe the opening of
a pseudogap, due to the spin-density-wave phase transition and inducing a
reshuffling of spectral weight from low to high frequencies. For compounds with
0.051 0.11 we detect the superconducting gap, while at =0.18 the
material stays metallic at all temperatures. We describe the effective metallic
contribution to the optical conductivity with two Drude terms, representing the
combination of a coherent and incoherent component, and extract the respective
scattering rates. We establish that the transport properties in the normal
phase are dominated by the coherent Drude term for 00.051 and by the
incoherent one for 0.0610.18, respectively. Finally through spectral
weight arguments, we give clear-cut evidence for moderate electronic
correlations for 00.061, which then crossover to values appropriate
for a regime of weak interacting and nearly-free electron metals for
0.11
Unerwünschte Arzneimittelwirkungen in der Heroin-gestützten Behandlung (HeGeBe) im Zusammenhang mit verschiedenen Applikationsformen in den Jahren 2001-2002
Functional renormalization group in the broken symmetry phase: momentum dependence and two-parameter scaling of the self-energy
We include spontaneous symmetry breaking into the functional renormalization
group (RG) equations for the irreducible vertices of Ginzburg-Landau theories
by augmenting these equations by a flow equation for the order parameter, which
is determined from the requirement that at each RG step the vertex with one
external leg vanishes identically. Using this strategy, we propose a simple
truncation of the coupled RG flow equations for the vertices in the broken
symmetry phase of the Ising universality class in D dimensions. Our truncation
yields the full momentum dependence of the self-energy Sigma (k) and
interpolates between lowest order perturbation theory at large momenta k and
the critical scaling regime for small k. Close to the critical point, our
method yields the self-energy in the scaling form Sigma (k) = k_c^2 sigma^{-}
(k | xi, k / k_c), where xi is the order parameter correlation length, k_c is
the Ginzburg scale, and sigma^{-} (x, y) is a dimensionless two-parameter
scaling function for the broken symmetry phase which we explicitly calculate
within our truncation.Comment: 9 pages, 4 figures, puplished versio
Wanted dead or alive? The tradeoff between in-vivo versus ex-vivo MR brain imaging in the mouse
High-resolution MRI of the mouse brain is gaining prominence in estimating changes in neuroanatomy over time to understand both normal developmental as well as disease processes and mechanisms. These types of experiments, where a change in time is to be captured as accurately as possible using imaging, face multiple experimental design choices. Chief amongst these choices is whether to image ex-vivo, where superior resolution and contrast are available, or in-vivo, where resolution and contrast are lower but the animal can be followed longitudinally. Here we explore this tradeoff by first estimating the sources of variability in anatomical mouse MRI and then, using statistical simulations, provide power analyses of these experiment design choices
Temperature dependence of the excitation spectrum in the charge-density-wave ErTe and HoTe systems
We provide optical reflectivity data collected over a broad spectral range
and as a function of temperature on the ErTe and HoTe materials, which
undergo two consecutive charge-density-wave (CDW) phase transitions at
= 265 and 288 K and at = 157 and 110 K, respectively. We
observe the temperature dependence of both the Drude component, due to the
itinerant charge carriers, and the single-particle peak, ascribed to the
charge-density-wave gap excitation. The CDW gap progressively opens while the
metallic component gets narrow with decreasing temperature. An important
fraction of the whole Fermi surface seems to be affected by the CDW phase
transitions. It turns out that the temperature and the previously investigated
pressure dependence of the most relevant CDW parameters share several common
features and behaviors. Particularly, the order parameter of the CDW state is
in general agreement with the predictions of the BCS theory
Delayed severe bleeding complications after treatment of pancreatic fluid collections with lumen-apposing metal stents
Effect of altered loading conditions during haemodialysis on left ventricular filling pattern
Changes in the circulating volume associated with haemodialysis result in modification of left ventricular loading conditions. To determine the influence of haemodialysis on Doppler indices of left ventricular filling, 12 patients (mean age 40.8 ±2.7 (SEM) years) with renal insufficiency but without overt heart disease were studied by Doppler-echocardiography immediately before and after haemodialysis. Haemodialysis resulted in a decrease in body weight from 68.0±3.8 kg to 65.0 ±3.7 kg (P< 0.01). Heart rate and blood pressure did not change significantly during haemodialysis. Left ventricular diastolic dimension (M-mode) decreased from 53.5±1.1 mm to 49.5±1.9 mm (P < 0.05), whereas the shortening fraction did not change. Haemodialysis elicited marked changes in the early diastolic rapid filling wave (E wave) recorded by pulsed Doppler at the level of the mitral annulus. Peak velocity of the early rapid filling phase (peak E) decreased significantly from 95.3 ± 8.2 cm .s−1 to 63.0 ±5.7cm .s−1 (P< 0.001) and mid-diastolic deceleration of transmitral velocity decreased from 437.3 ±54.2 cm . s−2 to 239.7 ±54.4 cm . s−2 (P<0.01). The peak filling velocity during atrial contraction (peak A) did not change (79.7 ±6.3 cm .s−1 vs 74.1±4.7 cm.s−1;P=NS). The ratio peak E/peak A decreasedfrom 1.19±0.06 to 0.85 ± 0.04 (P < 0.01) during haemodialysis. The results provide further evidence for the pronounced preload-dependence of Doppler indices of left ventricular diastolic functio
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