Effect of Mg-Ga powder addition on the superconducting properties of MgB2 samples

MgB2 bulk samples containing different proportions of Mg-Ga powder were prepared by an in situ reaction technique. The Mg-Ga powder was obtained via high energy ball milling of a Mg-10 at.% Ga composite, which was fabricated by melting of pure magnesium and gallium metals inside encapsulated stainless steel tube at 655 °C in a controlled atmosphere. The MgB2 samples containing 0, 1, 3, 5 and 7 wt.% of MgGa addition were sintered at 650 °C for 30 min in argon atmosphere. Magnetic measurements performed at 5 K and 20 K showed improved critical current density, Jc, in the low magnetic field range for samples with MgGa addition. The critical temperature, Tc, for all samples with gallium additions is consistently higher when compared to the pure MgB2. © 2007 Elsevier B.V. All rights reserved.

Effect of the Rashba and Dresselhaus spin-splitting terms on the electron g factor in semiconductor quantum wells under applied magnetic fields

We use the Ogg-McCombe Hamiltonian together with the Dresselhaus and Rashba spin-splitting terms to find the g factor of conduction electrons in GaAs-(Ga,Al)As semiconductor quantum wells (QWS) (either symmetric or asymmetric) under a magnetic field applied along the growth direction. The combined effects of non-parabolicity, anisotropy and spin-splitting terms are taken into account. Theoretical results are given as functions of the QW width and compared with available experimental data and previous theoretical works. © 2007 Elsevier B.V. All rights reserved.

Conceptual spaces and consciousness: Integrating cognitive and affective processes

In the book Conceptual Spaces: the Geometry of Thought [2000] Peter Gärdenfors proposes a new framework for cognitive science. Complementary to symbolic and subsymbolic [connectionist] descriptions, conceptual spaces are semantic structures constructed from empirical data representing the universe of mental states. We argue that Gärdenfors' modeling can be used in consciousness research to describe the phenomenal conscious world, its elements and their intrinsic relations. The conceptual space approach affords the construction of a universal state space of human consciousness, where all possible kinds of human conscious states could be mapped. Starting from this approach, we discuss the inclusion of feelings and emotions in conceptual spaces, and their relation to perceptual and cognitive states. Current debate on integration of affect/emotion and perception/cognition allows three possible descriptive alternatives: emotion resulting from basic cognition; cognition resulting from basic emotion, and both as relatively independent functions integrated by brain mechanisms. Finding a solution for this issue is an important step in any attempt of successful modeling of natural or artificial consciousness. After making a brief review of proposals in this area, we summarize the essentials of a new model of consciousness based on neuro-astroglial interactions. © 2011 World Scientific Publishing Company.

Treatment of experimental periodontitis in rats using repeated adjunctive antimicrobial photodynamic therapy

The aim of this study was to histologically and histometrically evaluate the influence of repeated adjunctive antimicrobial photodynamic therapy (aPDT) on bone loss (BL) in furcation areas in rats. Periodontitis was induced by placing a ligature around the mandibular molar in 75 rats. The animals were divided into five groups: the SS group was treated with saline solution (SS); the SRP group received scaling and root planing (SRP); the aPDT1 group received SRP as well as toluidine blue (TBO) and low-level laser therapy (LLLT; InGaAlP, 660 nm; 4.94 J/cm2/point) postoperatively at 0 h; the aPDT2 group received SRP as well as TBO and LLLT postoperatively at 0, 24, 28, and 72 h; and the aPDT3 group received SRP, TBO, and LLLT postoperatively at 0, 48, 96, and 144 h. The area of BL in the furcation region of the molar was histometrically analyzed. Data were analyzed statistically (P < 0.05). Animals treated with a single episode of aPDT showed less BL at days 7 and 30 than those who received only SRP treatment. No significant differences were found among the aPDT groups (P > 0.05). Repeated aPDT did not improve BL reduction when compared to a single episode of aPDT. © 2012 Springer-Verlag London Ltd.

Magnetic characteristics of nanocrystalline GaMnN films deposited by reactive sputtering

The magnetic characteristics of Ga1-xMnxN nanocrystalline films (x = 0.08 and x = 0.18), grown by reactive sputtering onto amorphous silica substrates (a-SiO2), are shown. Further than the dominant paramagnetic-like behaviour, both field- and temperature-dependent magnetization curves presented some particular features indicating the presence of secondary magnetic phases. A simple and qualitative analysis based on the Brillouin function assisted the interpretation of these secondary magnetic contributions, which were tentatively attributed to antiferromagnetic and ferromagnetic phases. © 2012 Elsevier Masson SAS. All rights reserved.

Strain- and electric field-induced band gap modulation in nitride nanomembranes

The hexagonal nanomembranes of the group III-nitrides are a subject of interest due to their novel technological applications. In this paper, we investigate the strain- and electric field-induced modulation of their band gaps in the framework of density functional theory. For AlN, the field-dependent modulation of the bandgap is found to be significant whereas the strain-induced semiconductor-metal transition is predicted for GaN. A relatively flat conduction band in AlN and GaN nanomembranes leads to an enhancement of their electronic mobility compared to that of their bulk counterparts. © 2013 IOP Publishing Ltd.

Efeitos estruturais e ópticos da incorporação de Mn em filmes nanocristalinos de 'Ga IND. 1-x Mn IND. xAs' preparados por sputtering

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preparação de filmes policristalinos de GaN pela técnica de sputtering reativo a baixas temperaturas de substrato

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Influência da Superfície do implante e da laserterapia na osseointegração, em ratas osteopênicas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigação óptica de pontos quânticos de InAs confinados em poços quânticos de In0,15Ga0,85As

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Cálculo e análise de efeitos de campo magnético nos estados eletrônicos de impurezas rasas em materiais semicondutores

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Efeito de vacâncias de nitrogênio, gálio e outros parâmetros da célula unitária nas propriedades eletrônicas do GaN

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Preparação e estudo termoanalítico dos 2-clorobenzalpiruvatos de alumínio, de gálio, de índio e de escândio no estado sólido

Pós-graduação em Química - IQ

Efeito do tratamento térmico nas propriedades ópticas de pontos quânticos emitindo na faixa espectral de 1,3 a 1,5 üm

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Análise da ação do laser em baixa intensidade sobre o processo de reparo após reimplante dentário: estudo histomorfométrico e imunoistoquímico

Pós-graduação em Odontologia - FOA