9,796 research outputs found
Graviton resonances on two-field thick branes
This work presents new results about the graviton massive spectrum in
two-field thick branes. Analyzing the massive spectra with a relative
probability method we have firstly showed the presence of resonance structures
and obtained a connection between the thickness of the defect and the lifetimes
of such resonances. We obtain another interesting results considering the
degenerate Bloch brane solutions. In these thick brane models, we have the
emergence of a splitting effect controlled by a degeneracy parameter. When the
degeneracy constant tends to a critical value, we have found massive resonances
to the gravitational field indicating the existence of modes highly coupled to
the brane. We also discussed the influence of the brane splitting effect over
the resonance lifetimes.Comment: 15 pages, 8 figure
Exchange stiffness in ultrathin perpendicularly-magnetized CoFeB layers determined using spin wave spectroscopy
We measure the frequencies of spin waves in nm-thick perpendicularly
magnetized FeCoB systems, and model the frequencies to deduce the exchange
stiffness of this material in the ultrathin limit. For this, we embody the
layers in magnetic tunnel junctions patterned into circular nanopillars of
diameters ranging from 100 to 300 nm and we use magneto-resistance to determine
which rf-current frequencies are efficient in populating the spin wave modes.
Micromagnetic calculations indicate that the ultrathin nature of the layer and
the large wave vectors used ensure that the spin wave frequencies are
predominantly determined by the exchange stiffness, such that the number of
modes in a given frequency window can be used to estimate the exchange. For 1
nm layers the experimental data are consistent with an exchange stiffness A= 20
pJ/m, which is slightly lower that its bulk counterpart. The thickness
dependence of the exchange stiffness has strong implications for the numerous
situations that involve ultrathin films hosting strong magnetization gradients,
and the micromagnetic description thereof.Comment: 5 pages, 4 figures, submitted to PR
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FOREVER: Fault/intrusiOn REmoVal through Evolution & Recovery
The goal of the FOREVER project is to develop a service for Fault/intrusiOn REmoVal through Evolution & Recovery. In order to achieve this goal, our work addresses three main tasks: the definition of the FOREVER service architecture; the analysis of how diversity techniques can improve resilience; and the evaluation of the FOREVER service. The FOREVER service is an important contribution to intrustion-tolerant replication middleware and significantly enhances the resilience
A pragmatic approach to the problem of the self-adjoint extension of Hamilton operators with the Aharonov-Bohm potential
We consider the problem of self-adjoint extension of Hamilton operators for
charged quantum particles in the pure Aharonov-Bohm potential (infinitely thin
solenoid). We present a pragmatic approach to the problem based on the
orthogonalization of the radial solutions for different quantum numbers. Then
we discuss a model of a scalar particle with a magnetic moment which allows to
explain why the self-adjoint extension contains arbitrary parameters and give a
physical interpretation.Comment: 8 pages, LaTeX, to appear in J. Phys.
Atividade antimicrobiana do óleo essencial do capim-limão.
bitstream/item/79658/1/ESSENCIAL-DE-CAPIM-LIMAO.pd
Electric-field control of spin waves at room temperature in multiferroic BiFeO3
To face the challenges lying beyond current CMOS-based technology, new
paradigms for information processing are required. Magnonics proposes to use
spin waves to carry and process information, in analogy with photonics that
relies on light waves, with several advantageous features such as potential
operation in the THz range and excellent coupling to spintronics. Several
magnonic analog and digital logic devices have been proposed, and some
demonstrated. Just as for spintronics, a key issue for magnonics is the large
power required to control/write information (conventionally achieved through
magnetic fields applied by strip lines, or by spin transfer from large
spin-polarized currents). Here we show that in BiFeO3, a room-temperature
magnetoelectric material, the spin wave frequency (>600 GHz) can be tuned
electrically by over 30%, in a non-volatile way and with virtually no power
dissipation. Theoretical calculations indicate that this effect originates from
a linear magnetoelectric effect related to spin-orbit coupling induced by the
applied electric field. We argue that these properties make BiFeO3 a promising
medium for spin wave generation, conversion and control in future magnonics
architectures.Comment: 3 figure
A Comparative Study of Onychomycosis and Traumatic Toenail Onychodystrophy Dermoscopic Patterns
Background: Onychomycosis (OM) and traumatic onychodystrophy (OD) are common causes of toenail changes. A clinical diagnosis is often impossible without mycology. Dermoscopy is helpful in this setting but yet underexplored. Prospective comparative studies between OM and OD onychoscopic findings have not been previously performed.
Objectives: We sought to determine distinguishing dermoscopic presentations of OM and traumatic OD.
Methods: We performed a prospective, observational study including patients presenting with ≥1 toenail onychodystrophy. All underwent onychoscopy, clinical and mycological examination. Based on these results, patients received a final diagnosis of OM or OD. Dermoscopic presentations of OM and OD patients were classified in patterns and compared.
Results: In all, 110 cases of OM and 82 of traumatic OD were compared. Statistical analyses revealed that the distal pulverized and the irregular spiked macular dermoscopic patterns were predictors of an OM diagnosis. The regular macular, the non-classifiable, the total and partial homogeneous background dermoscopic patterns correlated with traumatic OD diagnosis.
Conclusions: We demonstrated that OM and traumatic OD have distinctive onychoscopic presentations. Dermoscopy may be an important ancillary tool to guide their differential.info:eu-repo/semantics/publishedVersio
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