142 research outputs found
Is LiPdB a self-doped hole superconductor ?
We propose that the electrons responsible for superconductivity in Li2Pd3B
come from the palladium 4d-electrons. So, its electronic properties are likely
to be dominated by strong electronic correlations. The basic unit in this
material are PdB octahedra which share vertices to form a 3-dimensional
network. Due to the highly distorted nature of the PdB octahedron, one far
stretched Pd atom per octahedra becomes almost inactive for electronic
conduction. Thus, the material escapes the fate of becoming a half- filled
insulating Mott antiferromagnet by hiding extra charges at these inactive Pd
sites and becomes a self-doped correlated metal. We propose a 3-dimensional
single band t-J model which could be the correct minimal model for this
material.Comment: 4 pages Revtex, 2 figures included in the text, some typos corrected,
some text and references adde
Raman scattering in high temperature superconductors : An integrated view
The common features in the Raman data of high temperature superconductors:
(the cuprates, bismathates, alkali doped fullerides and some organic
superconductors), are analyzed. It was shown that qualitative understanding of
the data can be achieved in terms of non-Fermi liquid models for their normal
state, with appropiate bag mechanisms for the superconducting state.Comment: To appear in Physica B (1996). Invited talk presented by S. N.
Behera, Latex file in revtex style, six figures available on request to first
author (e-mail : [email protected]
The Singapore Asymptomatic Narrow Angles Laser Iridotomy Study (ANA-LIS): 5 year results of a Randomized Controlled Trial
PURPOSE: To examine the efficacy of laser peripheral iridotomy (LPI) in subjects diagnosed as primary angle closure suspects (PACS) DESIGN: Prospective, randomized controlled trial PARTICIPANTS: This multi-center, randomized controlled trial (NCT00347178, Clinical trials.gov) enrolled 480 subjects over the age of 50 years from glaucoma clinics in Singapore with bilateral asymptomatic PACS (defined as having ≥2 quadrants of appositional angle closure on gonioscopy). METHODS: Each subject underwent prophylactic LPI in one randomly selected eye, while the fellow eye served as control. Subjects were followed up yearly for 5 years. MAIN OUTCOME MEASURES: The primary outcome measure was development of primary angle closure (PAC, defined as presence of peripheral anterior synechiae, and/or intraocular pressure>21 mmHg or acute angle closure [AAC]) or PACG over 5 years. RESULTS: Of the 480 randomized subjects, the majority were Chinese (92.7%) and female (75.8%) with mean age of 62.8±6.9 years. LPI-treated eyes reached endpoint less frequently after five years (24, 5.0%, incidence rate [IR]=11.65 per 1000 eye-years) compared to control eyes (45, 9.4%, IR=21.84 per 1000 eye-years, p=0.001). The adjusted hazards ratio (HR) for progression to PAC was 0.55 (95%CI: 0.37-0.83, p=0.004) in LPI-treated eyes compared to control eyes. Older subjects (per year, HR=1.06, 95%CI: 1.03-1.10, p<0.001) and eyes with higher baseline IOP (per mm Hg, HR=1.35, 95%CI: 1.22-1.50, p<0.0001) were more likely to reach an endpoint. The number needed to treat in order to prevent an endpoint was 22 (95%CI: 12.8-57.5). CONCLUSIONS: In subjects with bilateral asymptomatic PACS, eyes that underwent prophylactic LPI had significantly fewer endpoints compared to control eyes over 5 years. However, the overall incidence of PAC or PACG was low
Multidisciplinary Ophthalmic Imaging Automated Analysis of Angle Closure From Anterior Chamber Angle Images
PURPOSE. To evaluate a novel software capable of automatically grading angle closure on EyeCam angle images in comparison with manual grading of images, with gonioscopy as the reference standard. METHODS. In this hospital-based, prospective study, subjects underwent gonioscopy by a single observer, and EyeCam imaging by a different operator. The anterior chamber angle in a quadrant was classified as closed if the posterior trabecular meshwork could not be seen. An eye was classified as having angle closure if there were two or more quadrants of closure. Automated grading of the angle images was performed using customized software. Agreement between the methods was ascertained by j statistic and comparison of area under receiver operating characteristic curves (AUC). RESULTS. One hundred forty subjects (140 eyes) were included, most of whom were Chinese (102/140, 72.9%) and women (72/140, 51.5%). Angle closure was detected in 61 eyes (43.6%) with gonioscopy in comparison with 59 eyes (42.1%, P ¼ 0.73) using manual grading, and 67 eyes (47.9%, P ¼ 0. CONCLUSIONS. Customized software for automated grading of EyeCam angle images was found to have good agreement with gonioscopy. Human observation of the EyeCam images may still be needed to avoid gross misclassification, especially in eyes with extensive angle closure
Holographic Superconductors
A holographic model of superconductors based on the action proposed by
Benini, Herzog, and Yarom [arXiv:1006.0731] is studied. This model has a
charged spin two field in an AdS black hole spacetime. Working in the probe
limit, the normalizable solution of the spin two field in the bulk gives rise
to a superconducting order parameter at the boundary of the AdS. We
calculate the fermion spectral function in this\ superconducting background and
confirm the existence of fermi arcs for non-vanishing Majorana couplings. By
changing the relative strength of the and condensations, the
position and the size of the fermi arcs are changed. When , the
spectrum becomes isotropic and the spectral function is s-wave like. By
changing the fermion mass, the fermi momentum is changed. We also calculate the
conductivity for these holographic superconductors where time reversal
symmetry has been broken spontaneously. A non-vanishing Hall conductivity is
obtained even without an external magnetic field.Comment: 24 pages,17 figures, Add more discussions on hall conductivity, two
new figures, Matched with published versio
Effect of Na content and hydration on the excitation spectrum of the cobaltite Na_xCoO_2 yH_2O
We report on a Raman scattering study on the superconducting cobaltite
as function of Na content and hydration (x1/3,
3/4 and y0, 2/3, 4/3). The observed phonon scattering and scattering
continua are analyzed in terms of lattice strain due to the structural misfit
and disorder. Hydration, due to the intercalation of one or two layers,
releases a part of this strain. Our Raman data suggest a connection between
disorder on the partly occupied Na sites, the split off of the level
from the other states of and superconductivity.Comment: 10 pages, 4 figures, for further information see
http://www.peter-lemmens.d
The pseudogap: friend or foe of high Tc?
Although nineteen years have passed since the discovery of high temperature
superconductivity, there is still no consensus on its physical origin. This is
in large part because of a lack of understanding of the state of matter out of
which the superconductivity arises. In optimally and underdoped materials, this
state exhibits a pseudogap at temperatures large compared to the
superconducting transition temperature. Although discovered only three years
after the pioneering work of Bednorz and Muller, the physical origin of this
pseudogap behavior and whether it constitutes a distinct phase of matter is
still shrouded in mystery. In the summer of 2004, a band of physicists gathered
for five weeks at the Aspen Center for Physics to discuss the pseudogap. In
this perspective, we would like to summarize some of the results presented
there and discuss its importance in the context of strongly correlated electron
systems.Comment: expanded version, 20 pages, 11 figures, to be published, Advances in
Physic
Physics, Astrophysics and Cosmology with Gravitational Waves
Gravitational wave detectors are already operating at interesting sensitivity
levels, and they have an upgrade path that should result in secure detections
by 2014. We review the physics of gravitational waves, how they interact with
detectors (bars and interferometers), and how these detectors operate. We study
the most likely sources of gravitational waves and review the data analysis
methods that are used to extract their signals from detector noise. Then we
consider the consequences of gravitational wave detections and observations for
physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version
<http://www.livingreviews.org/lrr-2009-2
Autozygosity influences cardiometabolic disease-associated traits in the AWI-Gen sub-Saharan African study
Pressure is not a state function for generic active fluids
Pressure is the mechanical force per unit area that a confined system exerts
on its container. In thermal equilibrium, it depends only on bulk properties
(density, temperature, etc.) through an equation of state. Here we show that in
a wide class of active systems the pressure depends on the precise interactions
between the active particles and the confining walls. In general, therefore,
active fluids have no equation of state, their mechanical pressures exhibit
anomalous properties that defy the familiar thermodynamic reasoning that holds
in equilibrium. The pressure remains a function of state, however, in some
specific and well-studied active models that tacitly restrict the character of
the particle-wall and/or particle-particle interactions.Comment: 8 pages + 9 SI pages, Nature Physics (2015
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