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Search Results: 1 - 10 of 22950 matches for " Fabricio Witzel;Souza "
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Evaluation of machine learning classifiers in keratoconus detection from orbscan II examinations
Souza, Murilo Barreto;Medeiros, Fabricio Witzel;Souza, Danilo Barreto;Garcia, Renato;Alves, Milton Ruiz;
Clinics , 2010, DOI: 10.1590/S1807-59322010001200002
Abstract: purpose: to evaluate the performance of support vector machine, multi-layer perceptron and radial basis function neural network as auxiliary tools to identify keratoconus from orbscan ii maps. methods: a total of 318 maps were selected and classified into four categories: normal (n = 172), astigmatism (n = 89), keratoconus (n = 46) and photorefractive keratectomy (n = 11). for each map, 11 attributes were obtained or calculated from data provided by the orbscan ii. ten-fold cross-validation was used to train and test the classifiers. besides accuracy, sensitivity and specificity, receiver operating characteristic (roc) curves for each classifier were generated, and the areas under the curves were calculated. results: the three selected classifiers provided a good performance, and there were no differences between their performances. the area under the roc curve of the support vector machine, multi-layer perceptron and radial basis function neural network were significantly larger than those for all individual orbscan ii attributes evaluated (p<0.05). conclusion: overall, the results suggest that using a support vector machine, multi-layer perceptron classifiers and radial basis function neural network, these classifiers, trained on orbscan ii data, could represent useful techniques for keratoconus detection.
Síndrome de Cogan: relato de caso
Medeiros, Fabricio Witzel de;Altieri, Rosana Aparecida Soares;Souza, Murilo Barreto;Milani, José Antonio de Almeida;Alves, Milton Ruiz;
Arquivos Brasileiros de Oftalmologia , 2005, DOI: 10.1590/S0004-27492005000600026
Abstract: non-luetic interstitial keratitis, deafness and vertigo characterize cogan's syndrome. the most common ocular findings in early cogan's syndrome are bilateral, peripheral, subepithelial numular corneal opacities. the report presents a patient with the evolution of the classic form of cogan's syndrome.
Spin-Dependent Ringing and Beats in a Quantum Dot System
Fabricio M. Souza
Physics , 2007, DOI: 10.1103/PhysRevB.76.205315
Abstract: We report spin-dependent quantum coherent oscillations (ringing) and beats of the total and spin currents flowing through a quantum dot with Zeeman split levels. The spin dependent transport is calculated via nonequilibrium Green function in the transient after a bias voltage is turned on at t=0. The dot is coupled to two electrodes that can be ferromagnetic or nonmagnetic. In the ferromagnetic case both parallel and antiparallel alignments are considered. The coherent oscillation and beat frequencies are controlled via the Zeeman energy E_Z. In particular, for E_Z=0 no beats are observed and the spin current is zero for nonmagnetic leads. In the ferromagnetic case a finite spin current is found for E_Z=0. The effects of temperature are also analyzed. We observe that with increasing temperature the ringing response and the beats tend to disappear. Additionally, the spin current goes to zero for nonmagnetic leads, remaining finite in the ferromagnetic case. The tunnel magnetoresistance (TMR) also reveals quantum coherent oscillations and beats, and it attains negative values for small enough temperatures and short times.
Bare LO-Phonon Peak in THz-Emission Signals: a Dielectric-Function Analysis
Fabricio M. Souza,J. C. Egues
Physics , 2002, DOI: 10.1590/S0103-97332002000200048
Abstract: We present a normal-mode analysis of coupled photocarrier-phonon dynamics in Te. We consider a dielectric function which accounts for LO phonons and the electron-hole gas within the Debye-Huckel model and RPA. Our main finding is the existence of a bare LO phonon mode in the system even at high carrier density. This oscillation is an unscreened L- mode arising from ineffective screening at large wave vectors. This mode is consistent with the bare LO-phonon peak in recent THz-emission spectra of Te.
Análise da ceratometria corneana em pacientes portadores de espasmo hemifacial
Pereira, Ivana Cardoso;Saraiva, Patrícia Grativol Costa;Saraiva, Fabio Petersen;Medeiros, Fabricio Witzel de;Miki, Gustavo;Matayoshi, Suzana;
Revista Brasileira de Oftalmologia , 2011, DOI: 10.1590/S0034-72802011000600005
Abstract: purpose: to determine the corneal keratometric variation in patients' eyes with unilateral hemifacial spasm which underwent treatment with botulinum toxin and set against control group. methods: eighteen patients with hemifacial spasm were submitted to complete ophthalmologic exam, corneal topography and orbscan previously botulinum toxin application and one month afterwards. they were evaluated for keratometry, bfs (anterior and posterior) and roush value. results: there were no statistical differences between eyes with hemi facial spasm and normal eyes related to keratometric values by topography and in the parameters evaluated by orbscan as roush and best fit sphere (anterior or posterior) prior to or after treatment with botulinum toxin. conclusion: this study has not shown statistical difference between the corneal curvatures when compared eyes with hemi facial spasm with the opposite normal eyes.
Angioplastia subintimal após trombose tardia de stent implantado em artéria hepática de fígado transplantado
Oliveira, Fabricio Mascarenhas de;Mour?o, Guilherme de Souza;
Jornal Vascular Brasileiro , 2012, DOI: 10.1590/S1677-54492012000100009
Abstract: the present study reports a case of hepatic artery stenosis treated by percutaneous transluminal angioplasty and stent. after 30 days, this artery occluded and the patient was submitted successfully to thrombolysis and subintimal percutaneous angioplasty. ninety days after the procedure a computed tomography showed patency of hepatic artery.
Enhanced photon-assisted spin transport in a quantum dot attached to ferromagnetic leads
Fabricio M. Souza,Thiago L. Carrara,E. Vernek
Physics , 2011, DOI: 10.1103/PhysRevB.84.115322
Abstract: We investigate real-time dynamics of spin-polarized current in a quantum dot coupled to ferromagnetic leads in both parallel and antiparallel alignments. While an external bias voltage is taken constant in time, a gate terminal, capacitively coupled to the quantum dot, introduces a periodic modulation of the dot level. Using non equilibrium Green's function technique we find that spin polarized electrons can tunnel through the system via additional photon-assisted transmission channels. Owing to a Zeeman splitting of the dot level, it is possible to select a particular spin component to be photon-transfered from the left to the right terminal, with spin dependent current peaks arising at different gate frequencies. The ferromagnetic electrodes enhance or suppress the spin transport depending upon the leads magnetization alignment. The tunnel magnetoresistance also attains negative values due to a photon-assisted inversion of the spin-valve effect.
Doen?as do segmento anterior ocular associadas a lentes de contato
Souza, Murilo Barreto;Alves, Milton Ruiz;Medeiros, Fabrício Witzel de;Yamane, íris de Souza;
Arquivos Brasileiros de Oftalmologia , 2008, DOI: 10.1590/S0004-27492008000700004
Abstract: nowadays, contact lenses have shown a larger variety of options in order to meet the needs of different patients. they have become more frequent in the clinical practice and, consequently, the complications related to contact lenses have been more common. this review attempted to describe the main alterations and diseases of the cornea and anterior segment associated with contact lens wearers.
Diagnóstico do ceratocone baseado no Orbscan com o auxílio de uma rede neural
Souza, Murilo Barreto;Medeiros, Fabrício Witzel de;Souza, Danilo Barreto;Alves, Milton Ruiz;
Arquivos Brasileiros de Oftalmologia , 2008, DOI: 10.1590/S0004-27492008000700013
Abstract: purpose: to evaluate an artificial neural network in order to correctly identify orbscan iitm tests of patients with normal and keratoconus corneas. methods: a retrospective analysis included 98 orbscan iitm tests of 59 subjects and an artificial neural network was created and trained based on the java neural network 1.1 software. seventy-three tests (59 normal tests and 14 keratoconus examinations) were applied to train the neural network and 25 eyes were used to test the method (19 normal eyes and 6 cases of keratoconus corneas). results: backpropagation method was performed to train the neural network to 5% error and 0.2 learning rate. the trained neural network presented sensibility and specificity of 83 and 100% respectively. conclusion: artificial neural network can accurately help clinicians to classify keratoconus in orbscan iitm tests.
Archiv für Lebenslaufforschung", Universit t Bremen, Deutschland Archive for Life Course Research, University of Bremen, Germany Archive for Life Course Research, University of Bremen, Alemania
Andreas Witzel
Forum : Qualitative Social Research , 2000,
Abstract: URN: urn:nbn:de:0114-fqs0003288 URN: urn:nbn:de:0114-fqs0003288 URN: urn:nbn:de:0114-fqs0003288
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