9,426 research outputs found
Erupted Complex Odontoma Mimicking a Mandibular Second Molar
Complex odontoma (CO) is considered one of the most common odontogenic lesions, composed by a miscellaneous of dental tissue such as enamel, dentin, pulp and sometimes cementum. They may interfere with the eruption of an associated tooth, being more prevalent in the posterior mandible. CO has been rarely reported as erupted, being considered an intraosseous lesion. This is a case report of a 17-year-old male with a benign fibro-osseous lesion consistent with CO that was located at the left second molar region, above the crown of the impacted mandibular second molar tooth. The lesion was surgically removed, and the tooth had to be extracted, since there was no indication that it could erupt naturally or with orthodontic traction. The histopathological examination confirmed the diagnosis of CO and after 6 months complete bone formation was observed radiographically. An early diagnosis will provide a better treatment option, avoiding tooth extraction or a more damaging surgery
Semiclassical Evolution of Dissipative Markovian Systems
A semiclassical approximation for an evolving density operator, driven by a
"closed" hamiltonian operator and "open" markovian Lindblad operators, is
obtained. The theory is based on the chord function, i.e. the Fourier transform
of the Wigner function. It reduces to an exact solution of the Lindblad master
equation if the hamiltonian operator is a quadratic function and the Lindblad
operators are linear functions of positions and momenta.
Initially, the semiclassical formulae for the case of hermitian Lindblad
operators are reinterpreted in terms of a (real) double phase space, generated
by an appropriate classical double Hamiltonian. An extra "open" term is added
to the double Hamiltonian by the non-hermitian part of the Lindblad operators
in the general case of dissipative markovian evolution. The particular case of
generic hamiltonian operators, but linear dissipative Lindblad operators, is
studied in more detail. A Liouville-type equivariance still holds for the
corresponding classical evolution in double phase, but the centre subspace,
which supports the Wigner function, is compressed, along with expansion of its
conjugate subspace, which supports the chord function.
Decoherence narrows the relevant region of double phase space to the
neighborhood of a caustic for both the Wigner function and the chord function.
This difficulty is avoided by a propagator in a mixed representation, so that a
further "small-chord" approximation leads to a simple generalization of the
quadratic theory for evolving Wigner functions.Comment: 33 pages - accepted to J. Phys.
On the classical-quantum correspondence for the scattering dwell time
Using results from the theory of dynamical systems, we derive a general
expression for the classical average scattering dwell time, tau_av. Remarkably,
tau_av depends only on a ratio of phase space volumes. We further show that,
for a wide class of systems, the average classical dwell time is not in
correspondence with the energy average of the quantum Wigner time delay.Comment: 5 pages, 1 figur
Teleportation of entangled states without Bell-state measurement
In a recent paper [Phys. Rev. A 70, 025803 (2004)] we presented a scheme to
teleport an entanglement of zero- and one-photon states from a bimodal cavity
to another one, with 100% success probability. Here, inspired on recent results
in the literature, we have modified our previous proposal to teleport the same
entangled state without using Bell-state measurements. For comparison, the time
spent, the fidelity, and the success probability for this teleportation are
considered.Comment: 4 pages, 1 figure, published in Phys. Rev. A 72, 045802 (2005
Design of an artificial neural network and feature extraction to identify arrhythmias from ECG
This paper presents a design of an artificial neural network (ANN) and feature extraction methods to identify two types of arrhythmias in datasets obtained through electrocardiography (ECG) signals, namely arrhythmia dataset (AD) and supraventricular arrhythmia dataset (SAD). No special ANN toolkit was used; instead, each neuron and necessary calculus were modeled and individually programmed. Thus, four temporal-based features are used: heart rate (HR), R-peaks root mean square (R-RMS), RR-peaks variance (RR-VAR), and QSR-complex standard deviation (QSR-SD). The network architecture presents four neurons in the input layer, eight in hidden layer and an output layer with two neurons. The proposed classification method uses the MIT-BIH Dataset (Massachusetts Institute of Technology-Beth Israel Hospital) for training, validation and execution or test phases. Preliminary results show the high efficiency of the proposed ANN design and its classification method, reaching accuracies between 98.76% and 98.91%, when in the identification of NSRD and arrhythmic ECG; and accuracies of 86.37% (AD) and 76.35% (SAD), when analyzing only classifications between both arrhythmias.info:eu-repo/semantics/acceptedVersio
Diluted antiferromagnet in a ferromagnetic enviroment
The question of robustness of a network under random ``attacks'' is treated
in the framework of critical phenomena. The persistence of spontaneous
magnetization of a ferromagnetic system to the random inclusion of
antiferromagnetic interactions is investigated. After examing the static
properties of the quenched version (in respect to the random antiferromagnetic
interactions) of the model, the persistence of the magnetization is analysed
also in the annealed approximation, and the difference in the results are
discussed
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