2,650 research outputs found
Effects of Superconductivity and Charge Order on the sub-Terahertz reflectivity of LaBaSrCuO
The reflectivity of both the plane and the c axis of two
single crystals of LaBaSrCuO has been measured
down to 5 cm, using coherent synchrotron radiation below 30 cm.
For = 0.085, a Josephson Plasma Resonance is detected at = 31 K
in , and a far-infrared peak (FIP) appears in the optical
conductivity below 50 K, where non-static charge ordering (CO) is reported by
X-ray scattering. For = 0.05 ( = 10 K), a FIP is observed in the
low-temperature tetragonal phase below the ordering temperature . At
1/8 doping the peak frequency scales linearly with , confirming that
the FIP is an infrared signature of CO, either static or fluctuating.Comment: v2: longer version, 9 pages, 6 color figure
The Spatial and Kinematic Distributions of Cluster Galaxies in a LCDM Universe -- Comparison with Observations
We combine dissipationless N-body simulations and semi-analytic models of
galaxy formation to study the spatial and kinematic distributions of cluster
galaxies in a LCDM cosmology. We investigate how the star formation rates,
colours and morphologies of galaxies vary as a function of distance from the
cluster centre and compare our results with the CNOC1 survey of galaxies from
15 X-ray luminous clusters in the redshift range 0.18 to 0.55. In our model,
gas no longer cools onto galaxies after they fall into the cluster and their
star formation rates decline on timescales of 1-2 Gyr. Galaxies in cluster
cores have lower star formation rates and redder colours than galaxies in the
outer regions because they were accreted earlier. Our colour and star formation
gradients agree with those those derived from the data. The difference in
velocity dispersions between red and blue galaxies observed in the CNOC1
clusters is also well reproduced by the model. We assume that the morphologies
of cluster galaxies are determined solely by their merging histories.
Morphology gradients in clusters arise naturally, with the fraction of bulge-
dominated galaxies highest in cluster cores. We compare these gradients with
the CNOC1 data and find excellent agreement for bulge-dominated galaxies. The
simulated clusters contain too few galaxies of intermediate bulge-to-disk
ratio, suggesting that additional processes may influence the morphological
evolution of disk-dominated galaxies in clusters. Although the properties of
the cluster galaxies in our model agree extremely well with the data, the same
is not true of field galaxies. Both the star formation rates and the colours of
bright field galaxies appear to evolve much more strongly from redshift 0.2 to
0.4 in the CNOC1 field sample than in our simulations.Comment: 17 pages, sumitted to MNRAS. Simulation outputs, halo catalogs,
merger trees and galaxy catalogs are now available at
http://www.mpa-garching.mpg.de/GIF
Low-energy electrodynamics of superconducting diamond
Heavily-boron-doped diamond films become superconducting with critical
temperatures well above 4 K. Here we first measure the reflectivity of
such a film down to 5 cm, by also using Coherent Synchrotron Radiation.
We thus determine the optical gap, the field penetration depth, the range of
action of the Ferrell-Glover-Tinkham sum rule, and the electron-phonon spectral
function. We conclude that diamond behaves as a dirty BCS superconductor.Comment: 4 pages including 3 figure
Liver Transplantation in Adults
Human liver transplantation has been possible since 1967. We report our experience in 32 adult patients who received liver transplants at the University of Pittsburgh over a 16‐month period. Survival data, method utilized for patient selection, costs, and morbidity of the procedure are discussed. Copyright © 1982 American Association for the Study of Liver Disease
Observation of charge-density-wave excitations in manganites
In the optical conductivity of four different manganites with commensurate
charge order (CO), strong peaks appear in the meV range below the ordering
temperature T_{CO}. They are similar to those reported for one-dimensional
charge density waves (CDW) and are assigned to pinned phasons. The peaks and
their overtones allow one to obtain, for La{1-n/8}Ca{n/8}$MnO{3} with n = 5, 6,
the electron-phonon coupling, the effective mass of the CO system, and its
contribution to the dielectric constant. These results support a description of
the CO in La-Ca manganites in terms of moderately weak-coupling and of the CDW
theory.Comment: To be published on Phys. Rev. Let
Phase diagram and optical conductivity of La1.8-xEu0.2SrxCuO4
La1.8-xEu0.2SrxCuO4 (LESCO) is the member of the 214 family which exhibits
the largest intervals among the structural, charge ordering (CO), magnetic, and
superconducting transition temperatures. By using new dc transport measurements
and data in the literature we construct the phase diagram of LESCO between x =
0.8 and 0.20. This phase diagram has been further probed in ac, by measuring
the optical conductivity {\sigma}1({\omega}) of three single crystals with x =
0.11, 0.125, and 0.16 between 10 and 300 K in order to associate the
extra-Drude peaks often observed in the 214 family with a given phase. The
far-infrared peak we detect in underdoped LESCO is the hardest among them,
survives up to room temperature and is associated with charge localization
rather than with ordering. At the CO transition for the commensurate doping x =
0.125 instead the extra-Drude peak hardens and a pseudogap opens in
{\sigma}1({\omega}), approximately as wide as the maximum superconducting gap
of LSCO.Comment: 6 pages, 6 figure
When Concerned People Produce Environmental Information: A Need to Re-Think Existing Legal Frameworks and Governance Models?
When faced with an environmental problem, locals are often among the first to act. Citizen science is increasingly one of the forms of participation in which people take action to help solve environmental problems that concern them. This implies, for example, using methods and instruments with scientific validity to collect and analyse data and evidence to understand the problem and its causes. Can the contribution of environmental data by citizens be articulated as a right? In this article, we explore these forms of productive engagement with a local matter of concern, focussing on their potential to challenge traditional allocations of responsibilities. Taking mostly the perspective of the European legal context, we identify an existing gap between the right to obtain environmental information, granted at present by the Aarhus Convention, and “a right to contribute information” and have that information considered by appointed institutions. We also explore what would be required to effectively practise this right in terms of legal and governance processes, capacities, and infrastructures, and we propose a flexible framework to implement it. Situated at the intersection of legal and governance studies, this article builds on existing literature on environmental citizen science, and on its interplay with law and governance. Our methodological approach combines literature review with legal analysis of the relevant conventions and national rules. We conclude by reflecting on the implications of our analysis, and on the benefits of this legal innovation, potentially fostering data altruism and an active citizenship, and shielding ordinary people against possible legal risks
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