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Search Results: 1 - 10 of 223967 matches for " R. Magalhaes-Paniago "
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X-ray method to study temperature-dependent stripe domains in MnAs/GaAs(001)
R. Magalhaes-Paniago,L. N. Coelho,B. R. A. Neves,H. Westfahl Jr.,F. Iikawa,L. Daweritz,C. Spezzani,M. Sacchi
Physics , 2004, DOI: 10.1063/1.1844599
Abstract: MnAs films grown on GaAs (001) exhibit a progressive transition between hexagonal (ferromagnetic) and orthorhombic (paramagnetic) phases at wide temperature range instead of abrupt transition during the first-order phase transition. The coexistence of two phases is favored by the anisotropic strain arising from the constraint on the MnAs films imposed by the substrate. This phase coexistence occurs in ordered arrangement alternating periodic terrace steps. We present here a method to study the surface morphology throughout this transition by means of specular and diffuse scattering of soft x-rays, tuning the photon energy at the Mn 2p resonance. The results show the long-range arrangement of the periodic stripe-like structure during the phase coexistence and its period remains constant, in agreement with previous results using other techniques.
Atomic ordering in self-assembled Ge:Si(001) islands observed by X-ray scattering
A. Malachias,T. U. Schulli,G. Medeiros-Ribeiro,M. Stoffel,O. G. Schmidt,T. H. Metzger,R. Magalhaes-Paniago
Physics , 2004,
Abstract: X-ray diffuse scattering in the vicinity of a basis-forbidden (200) Bragg reflection was measured for a sample with uncapped self-assembled Ge islands epitaxially grown on Si(001). Our results provide evidence of atomically ordered SiGe domains in both islands and wetting layer. The modeling of x-ray profiles reveals the presence of antiphase boundaries separating the ordered domains in a limited region of the islands where the stoichiometry is close to Si0.5Ge0.5.
M?ssbauer spectroscopy, superparamagnetism and ferrofluids
Pfannes, H.-D.;Dias Filho, J. H.;Magalh?es-Paniago, R.;López, J. L.;Paniago, R.;
Brazilian Journal of Physics , 2001, DOI: 10.1590/S0103-97332001000300011
Abstract: some fundamentals of m?ssbauer spectroscopy and of fluctuating magnetic hyperfine interactions are reviewed. an expression for calculation of spin-phonon interaction transition probabilities on the ground of a debye model is given. basic ideas of superparamagnetism and classical results for low-temperature relaxation rates are presented. a theory of superparamagnetism based on spin-phonon interaction is introduced. it is shown how to calculate from this m?ssbauer spectra taking all spin-levels into account. experimental spectra of ferrofluids are compared with simulated spectra and found in good accordance.
Influence of the Sol-Gel pH Process and Compact Film on the Efficiency of -Based Dye-Sensitized Solar Cells
A. O. T. Patrocinio,A. S. El-Bachá,E. B. Paniago,R. M. Paniago,N. Y. Murakami Iha
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/638571
Abstract: The influence of pH during hydrolysis of titanium(IV) isopropoxide on the morphological and electronic properties of TiO2 nanoparticles prepared by the sol-gel method is investigated and correlated to the photoelectrochemical parameters of dye-sensitized solar cells (DSCs) based on TiO2 films. Nanoparticles prepared under acid pH exhibit smaller particle size and higher surface area, which result in higher dye loadings and better short-circuit current densities than DSCs based on alkaline TiO2-processed films. On the other hand, the product of charge collection and separation quantum yields in films with TiO2 obtained by alkaline hydrolysis is c.a. 27% higher than for the acid TiO2 films. The combination of acid and alkaline TiO2 nanoparticles as mesoporous layer in DSCs results in a synergic effect with overall efficiencies up to 6.3%, which is better than the results found for devices employing one of the nanoparticles separately. These distinct nanoparticles can be also combined by using the layer-by-layer technique (LbL) to prepare compact TiO2 films applied before the mesoporous layer. DSCs employing photoanodes with 30 TiO2 bilayers have shown efficiencies up to 12% higher than the nontreated photoanode ones. These results can be conveniently used to develop optimized synthetic procedures of TiO2 nanoparticles for several dye-sensitized solar cell applications.
Intrinsic dielectric properties of magnetodielectric La$_2$CoMnO$_6$
R. X. Silva,R. L. Moreira,R. M. Almeida,R. Paniago,C. W. A. Paschoal
Physics , 2014,
Abstract: Manganites with double perovskite structure are being attractive because of their interesting magnetoelectric and dielectric responses. Particularly, colossal dielectric constant (CDC) behavior has been observed in La$_2$CoMnO$_6$ (LCMO), at radio frequencies and room temperature. In this paper, we employed infrared-reflectivity spectroscopy onto a LCMO ceramic obtained through a modified Pechini's method to determine the phonon contribution to the intrinsic dielectric response of the system and to investigate the CDC origin. The analysis of the main polar modes and of the obtained phonon parameters show that CDC effect of LCMO is of pure extrinsic origin. In addition, we have estimated the dielectric constant and quality factor of the material in microwave region, $e'_s \sim 16$ and $Q_u \times f \sim 124$ THz, which shows that LCMO is appropriate for applications into microwave devices and circuitry.
The relationship between the thyroid hormone (or its lack) and dysplastic hematopoiesis
Magalhaes SMM,Pinheiro D,Souza M,Pinheiro R
Journal of Cancer Research and Therapeutics , 2008,
Abstract:
Estereoscopio com tela holografica para ver tomografias
J. J. Lunazzi,R. L. Serra,D. S. F. Magalhaes
Physics , 2010,
Abstract: A estereoscopia eh uma tecnica que permite a observacao de imagens tridimensionais, mas estah sempre associada com o uso de algum equipamento especial para visualizacao, como oculos bicolores ou polarizados. Para o uso em aplicacoes medicas o emprego de tais equipamentos pode inviabilizar sua utilizacao durante procedimentos cirurgicos, por exemplo. Neste trabalho apresentamos um novo tipo de estereoscopio que utiliza uma tela holografica para geracao de imagens tridimensionais sem o uso de qualquer equipamento adicional. Apresentamos a descricao do equipamento utilizado e resultados das imagens visualizadas.
Decoherence and Irreversibility: the role of the reservoir effective Hilbert space size
Adelcio C. Oliveira,A. R. Bosco de Magalhaes
Physics , 2008,
Abstract: We show that decoherence is determined by the effective Hilbert space size, and demonstrate that a few degrees of freedom system can simulate a "N" degrees of freedom environment if they have the same effective Hilbert space. The effective Hilbert space size of the environment also determines its long time efficiency as generator of irreversible coherence loss.
Prostatic cryptococcosis: a case report
Chang, M. R.;Paniago, A. M. M.;Silva, M. M.;Lazéra, M. S.;Wanke, B.;
Journal of Venomous Animals and Toxins including Tropical Diseases , 2008, DOI: 10.1590/S1678-91992008000200015
Abstract: cryptococcosis is a systemic mycosis usually affecting immunodeficient individuals. in contrast, immunologically competent patients are rarely affected. dissemination of cryptococcosis usually involves the central nervous system, manifesting as meningitis or meningoencephalitis. prostatic lesions are not commonly found. a case of prostate cryptococcal infection is presented and cases of prostatic cryptococcosis in normal and immunocompromised hosts are reviewed. a fifty-year-old hiv-negative man with urinary retention and renal insufficiency underwent prostatectomy due to massive enlargement of the organ. prostate histopathologic examination revealed encapsulated yeast-like structures. after 30 days, the patient's clinical manifestations worsened, with headache, neck stiffness, bradypsychia, vomiting and fever. direct microscopy of the patient's urine with china ink preparations showed capsulated yeasts, and positive culture yielded cryptococcus neoformans. this fungus was later isolated from cerebrospinal fluid and blood cultures, demonstrating thus its dissemination. the patient was discharged after 27 days in hospital and, despite a regimen of amphotericin b, he died four months later. this case points to cryptococcosis as a possible cause of prostatic disease and reinforces the importance of communication between the medical team and pathology and microbiology laboratories aiming at a more accurate diagnosis and successful treatment.
Bilateral ventricular myocardial dysplasia in a Shar-Pei dog
Ocarino, N.M.;Nascimento, E.F.;Paniago, J.D.G.;Serakides, R.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2011, DOI: 10.1590/S0102-09352011000300034
Abstract: um c?o shar-pei de cinco anos de idade foi encaminhado para exame de necropsia com histórico de morte súbita. ao exame macroscópico foram observadas, no cora??o, áreas pálidas extensas envolvendo o miocárdio do ventrículo direito e esquerdo. ao exame histológico foi observada infiltra??o intensa de células adiposas bem diferenciadas no miocárdio de ambos os ventrículos associada à moderada atrofia e degenera??o de cardiomiócitos. os achados microscópicos foram compatíveis com diagnóstico de displasia miocardial ventricular bilateral.
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