16,337 research outputs found
Majorana Fermions Signatures in Macroscopic Quantum Tunneling
Thermodynamic measurements of magnetic fluxes and I-V characteristics in
SQUIDs offer promising paths to the characterization of topological
superconducting phases. We consider the problem of macroscopic quantum
tunneling in an rf-SQUID in a topological superconducting phase. We show that
the topological order shifts the tunneling rates and quantum levels, both in
the parity conserving and fluctuating cases. The latter case is argued to
actually enhance the signatures in the slowly fluctuating limit, which is
expected to take place in the quantum regime of the circuit. In view of recent
advances, we also discuss how our results affect a -junction loop.Comment: 10 pages, 11 figure
Gravitational Wave Signatures of Highly Magnetized Neutron Stars
Motivated by the recent gravitational wave detection by the LIGO-VIRGO
observatories, we study the Love number and dimensionless tidal polarizability
of highly magnetized stars. We also investigate the fundamental quasi-normal
mode of neutron stars subject to high magnetic fields. To perform our
calculations we use the chaotic field approximation and consider both nucleonic
and hyperonic stars. As far as the fundamental mode is concerned, we conclude
that the role played by the constitution of the stars is far more relevant than
the intensity of the magnetic field and if massive stars are considered, the
ones constituted by nucleons only present frequencies somewhat lower than the
ones with hyperonic cores, a feature that can be used to point out the real
internal structure of neutron stars. Moreover, our studies clearly indicate
that strong magnetic fields play a crucial role in the deformability of low
mass neutron stars, with possible consequences on the interpretation of the
detected gravitational waves signatures.Comment: 24 pages, 4 figures, 6 table
Development of liquid xenon detectors for medical imaging
In the present paper, we report on our developments of liquid xenon detectors
for medical imaging, positron emission tomography and single photon imaging, in
particular. The results of the studies of several photon detectors
(photomultiplier tubes and large area avalanche photodiode) suitable for
detection of xenon scintillation are also briefly described.Comment: 13 pages, 5 figures, presented on the International Workshop on
Techniques and Applications of Xenon Detectors (Xenon01), ICRR, Univ. of
Tokyo, Kashiwa, Japan, December 3-4, 2001 (submitted to proceedings
Experimental determination of the non-extensive entropic parameter
We show how to extract the parameter from experimental data, considering
an inhomogeneous magnetic system composed by many Maxwell-Boltzmann homogeneous
parts, which after integration over the whole system recover the Tsallis
non-extensivity. Analyzing the cluster distribution of
LaSrMnO manganite, obtained through scanning tunnelling
spectroscopy, we measure the parameter and predict the bulk magnetization
with good accuracy. The connection between the Griffiths phase and
non-extensivity is also considered. We conclude that the entropic parameter
embodies information about the dynamics, the key role to describe complex
systems.Comment: Submitted to Phys. Rev. Let
Há alguma diferença entre as próteses de disco cervicais?
Objetivo: A artroplastia cervical na patologia degenerativa surgiu como alternativa à artrodese anterior com o objetivo de eliminar a “doença do nível adjacente”. As próteses de disco apresentam diferentes materiais, design, técnica e mobilidade. Os autores avaliaram dor, disfunção e complicações para comparar a eficácia de diferentes próteses de disco.Material e Métodos: Foram analisadas retrospectivamente as próteses de disco cervical realizadas entre 2004 e 2010, com o total de 26 próteses em 22 doentes.
Os resultados de 5 próteses Baguera® foram comparados com 14 próteses Prestige®, 4 PCM® e 3 Bryan®.
Foi utilizada a escala visual analógica da dor (VAS), Neck Disability Index (NDI) e inquirido o grau de satisfação. Imagiologicamente foi determinada estabilidade, mobilidade e alterações degenerativas.Resultados: O follow-up das 5 próteses Baguera® foi 20.2±13.7 meses e nas restantes 21 próteses foi 55.2±15.8 meses (p=0.02).
A avaliação da dor não foi diferente. O grupo Baguera® apresenta superioridade na mobilidade (p=0.045), NDI pós-operatório (p=0.009) e melhoria do NDI global (p=0.01). Comparando doentes com disfunção nula/ligeira e severa/completa, a prótese Baguera® tem vantagem sobre as restantes 3 (p=0.04).
Ocorreram complicações em 4 (9.5%) doentes do grupo misto, com 2 reintervenções e 2 doentes com ossificação heterotrópica e perda total de mobilidade da prótese.Conclusão: A prótese de disco Baguera® apresenta superioridade em mobilidade e função, e apesar de diferente follow-up não apresenta complicações enquanto as restantes 3 próteses apresentam complicações e perda de mobilidade.
Estudos a longo prazo vão determinar se as vantagens teóricas continuam a traduzir benefícios clínicos
Dynamic Provenance for SPARQL Update
While the Semantic Web currently can exhibit provenance information by using
the W3C PROV standards, there is a "missing link" in connecting PROV to storing
and querying for dynamic changes to RDF graphs using SPARQL. Solving this
problem would be required for such clear use-cases as the creation of version
control systems for RDF. While some provenance models and annotation techniques
for storing and querying provenance data originally developed with databases or
workflows in mind transfer readily to RDF and SPARQL, these techniques do not
readily adapt to describing changes in dynamic RDF datasets over time. In this
paper we explore how to adapt the dynamic copy-paste provenance model of
Buneman et al. [2] to RDF datasets that change over time in response to SPARQL
updates, how to represent the resulting provenance records themselves as RDF in
a manner compatible with W3C PROV, and how the provenance information can be
defined by reinterpreting SPARQL updates. The primary contribution of this
paper is a semantic framework that enables the semantics of SPARQL Update to be
used as the basis for a 'cut-and-paste' provenance model in a principled
manner.Comment: Pre-publication version of ISWC 2014 pape
Percolative phase transition on ferromagnetic insulator manganites: uncorrelated to correlated polaron clusters
In this work, we report an atomic scale study on the ferromagnetic insulator
manganite LaMnO using PAC spectroscopy. Data analysis
reveals a nanoscopic transition from an undistorted to a Jahn-Teller-distorted
local environment upon cooling. The percolation thresholds of the two local
environments enclose a macroscopic structural transition
(Rhombohedric-Orthorhombic). Two distinct regimes of JT-distortions were found:
a high temperature regime where uncorrelated polaron clusters with severe
distortions of the MnO octahedra survive up to
and a low temperature regime where correlated regions have a weaker
JT-distorted symmetry.Comment: 4 pages, 4 Figures, submitted to PRL, new version with more data,
text reformulate
Spherical harmonic decomposition applied to spatial-temporal analysis of human high-density EEG
We demonstrate an application of spherical harmonic decomposition to analysis
of the human electroencephalogram (EEG). We implement two methods and discuss
issues specific to analysis of hemispherical, irregularly sampled data.
Performance of the methods and spatial sampling requirements are quantified
using simulated data. The analysis is applied to experimental EEG data,
confirming earlier reports of an approximate frequency-wavenumber relationship
in some bands.Comment: 12 pages, 8 figures, submitted to Phys. Rev. E, uses APS RevTeX
style
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