3,021 research outputs found
Preditores de fibrilação atrial de novo em unidade de cuidados intensivos não cardÃaca
OBJECTIVE:
To assess the predictors of de novo atrial fibrillation in patients in a non-cardiac intensive care unit.
METHODS:
A total of 418 hospitalized patients were analyzed between January and September 2016 in a non-cardiac intensive care unit. Clinical characteristics, interventions, and biochemical markers were recorded during hospitalization. In-hospital mortality and length of hospital stay in the intensive care unit were also evaluated.
RESULTS:
A total of 310 patients were included. The mean age of the patients was 61.0 ± 18.3 years, 49.4% were male, and 23.5% presented de novo atrial fibrillation. The multivariate model identified previous stroke (OR = 10.09; p = 0.016) and elevated levels of pro-B type natriuretic peptide (proBNP, OR = 1.28 for each 1,000pg/mL increment; p = 0.004) as independent predictors of de novo atrial fibrillation. Analysis of the proBNP receiver operating characteristic curve for prediction of de novo atrial fibrillation revealed an area under the curve of 0.816 (p 5,666pg/mL. There were no differences in mortality (p = 0.370), but the lengths of hospital stay (p = 0.002) and stay in the intensive care unit (p = 0.031) were higher in patients with de novo atrial fibrillation.
CONCLUSIONS:
A history of previous stroke and elevated proBNP during hospitalization were independent predictors of de novo atrial fibrillation in the polyvalent intensive care unit. The proBNP is a useful and easy- and quick-access tool in the stratification of atrial fibrillation risk.Objetivo:
Avaliar quais os preditores de fibrilação atrial de novo em doentes de uma unidade de cuidados intensivos não cardÃaca.
Métodos:
Foram analisados 418 doentes internados entre janeiro e setembro de 2016 em uma unidade de cuidados intensivos não cardÃaca. Registaram-se as caracterÃsticas clÃnicas, as intervenções efetuadas e os marcadores bioquÃmicos durante a internação. Avaliaram-se ainda a mortalidade hospitalar e o tempo de internação hospitalar e na unidade de cuidados intensivos.
Resultados:
Foram incluÃdos 310 doentes, com média de idades de 61,0 ± 18,3 anos, 49,4% do sexo masculino, 23,5% com fibrilação atrial de novo. O modelo multivariável identificou acidente vascular cerebral prévio (OR de 10,09; p = 0,016) e valores aumentados de proBNP (OR de 1,28 por cada aumento em 1.000pg/mL; p = 0,004) como preditores independentes de fibrilação atrial de novo. A análise por curva CaracterÃstica de Operação do Receptor do proBNP para predição de fibrilação atrial de novo revelou área sob a curva de 0,816 (p 5.666pg/mL. Não se verificaram diferenças na mortalidade (p = 0,370), porém a duração da internação hospitalar (p = 0,002) e na unidade de cuidados intensivos (p = 0,031) foi superior nos doentes com fibrilação atrial de novo.
Conclusões:
História de acidente vascular cerebral prévio e proBNP elevado em internação constituÃram preditores independentes de fibrilação atrial de novo na unidade de cuidados intensivos polivalente. O proBNP pode constituir ferramenta útil, de fácil e rápido acesso na estratificação do risco de fibrilação atrial.info:eu-repo/semantics/publishedVersio
Tuning edge state localization in graphene nanoribbons by in-plane bending
The electronic properties of graphene are influenced by both geometric
confinement and strain. We study the electronic structure of in-plane bent
graphene nanoribbons, systems where confinement and strain are combined. To
understand its electronic properties, we develop a tight-binding model that has
a small computational cost and is based on exponentially decaying hopping and
overlap parameters. Using this model, we show that the edge states in zigzag
graphene nanoribbons are sensitive to bending and develop an effective
dispersion that can be described by a one-dimensional atomic chain model.
Because the velocity of the electrons at the edge is proportional to the slope
of the dispersion, the edge states become gradually delocalized upon increasing
the strength of bending.Comment: 11 pages, 8 figure
Magnetic susceptibility anisotropies in a two-dimensional quantum Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interactions
The magnetic and thermodynamic properties of the two-dimensional quantum
Heisenberg antiferromagnet that incorporates both a Dzyaloshinskii-Moriya and
pseudo-dipolar interactions are studied within the framework of a generalized
nonlinear sigma model (NLSM). We calculate the static uniform susceptibility
and sublattice magnetization as a function of temperature and we show that: i)
the magnetic-response is anisotropic and differs qualitatively from the
expected behavior of a conventional easy-axis QHAF; ii) the Neel second-order
phase transition becomes a crossover, for a magnetic field B perpendicular to
the CuO(2) layers. We provide a simple and clear explanation for all the
recently reported unusual magnetic anisotropies in the low-field susceptibility
of La(2)CuO(4), L. N. Lavrov et al., Phys. Rev. Lett. 87, 017007 (2001), and we
demonstrate explicitly why La(2)CuO(4) can not be classified as an ordinary
easy-axis antiferromagnet.Comment: 6 pages, 3 figures, Revtex4, accepted for publication in Phys. Rev.
Dynamics of topological defects in a spiral: a scenario for the spin-glass phase of cuprates
We propose that the dissipative dynamics of topological defects in a spiral
state is responsible for the transport properties in the spin-glass phase of
cuprates. Using the collective-coordinate method, we show that topological
defects are coupled to a bath of magnetic excitations. By integrating out the
bath degrees of freedom, we find that the dynamical properties of the
topological defects are dissipative. The calculated damping matrix is related
to the in-plane resistivity, which exhibits an anisotropy and linear
temperature dependence in agreement with experimental data.Comment: 4 pages, as publishe
Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields
The behavior of the nonlinear susceptibility and its relation to the
spin-glass transition temperature , in the presence of random fields, are
investigated. To accomplish this task, the Sherrington-Kirkpatrick model is
studied through the replica formalism, within a one-step
replica-symmetry-breaking procedure. In addition, the dependence of the
Almeida-Thouless eigenvalue (replicon) on the random fields
is analyzed. Particularly, in absence of random fields, the temperature
can be traced by a divergence in the spin-glass susceptibility ,
which presents a term inversely proportional to the replicon . As a result of a relation between and , the
latter also presents a divergence at , which comes as a direct consequence
of at . However, our results show that, in the
presence of random fields, presents a rounded maximum at a temperature
, which does not coincide with the spin-glass transition temperature
(i.e., for a given applied random field). Thus, the maximum
value of at reflects the effects of the random fields in the
paramagnetic phase, instead of the non-trivial ergodicity breaking associated
with the spin-glass phase transition. It is also shown that still
maintains a dependence on the replicon , although in a more
complicated way, as compared with the case without random fields. These results
are discussed in view of recent observations in the LiHoYF
compound.Comment: accepted for publication in PR
Derivation of the generalized Non Linear Sigma Model in the presence of the Dzyaloshinskii-Moriya interaction
We derive the long-wavelength non-linear sigma model for a two-dimensional
Heisenberg system in the presence of the Dzyaloshinskii-Moriya and
pseudodipolar interactions. We show that the system is a non-conventional
easy-axis antiferromagnet, displaying an anomalous coupling between the
magnetic field and the staggered order parameter. Our results are in good
agreement with recent experimental data for undoped La2CuO4 compounds.Comment: Proceedings of SCES05, to appear on Physica
Role of the transverse field in inverse freezing in the fermionic Ising spin-glass model
We investigate the inverse freezing in the fermionic Ising spin-glass (FISG)
model in a transverse field . The grand canonical potential is
calculated in the static approximation, replica symmetry and one-step replica
symmetry breaking Parisi scheme. It is argued that the average occupation per
site is strongly affected by . As consequence, the boundary phase
is modified and, therefore, the reentrance associated with the inverse freezing
is modified too.Comment: 6 pages, 3 figures, accepted for publication in PR
Finite-momentum Bose-Einstein condensates in shaken 2D square optical lattices
We consider ultracold bosons in a 2D square optical lattice described by the
Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is
applied to the system, which shakes the lattice along one of the diagonals. The
effect of the shaking is to renormalize the nearest-neighbor hopping
coefficients, which can be arbitrarily reduced, can vanish, or can even change
sign, depending on the shaking parameter. It is therefore necessary to account
for higher-order hopping terms, which are renormalized differently by the
shaking, and introduce anisotropy into the problem. We show that the
competition between these different hopping terms leads to finite-momentum
condensates, with a momentum that may be tuned via the strength of the shaking.
We calculate the boundaries between the Mott-insulator and the different
superfluid phases, and present the time-of-flight images expected to be
observed experimentally. Our results open up new possibilities for the
realization of bosonic analogs of the FFLO phase describing inhomogeneous
superconductivity.Comment: 7 pages, 7 figure
- …