Directed self-assembly of quantum structures by nanomechanical stamping using probe tips

We demonstrate that nanomechanically stamped substrates can be used as templates to pattern and direct the self-assembly of epitaxial quantum structures such as quantum dots. Diamond probe tips are used to indent or stamp the surface of GaAs( 100) to create nanoscale volumes of dislocation-mediated deformation, which alter the growth surface strain. These strained sites act to bias nucleation, hence allowing for selective growth of InAs quantum dots. Patterns of quantum dots are observed to form above the underlying nanostamped template. The strain state of the patterned structures is characterized by micro-Raman spectroscopy. The potential of using nanoprobe tips as a quantum dot nanofabrication technology are discussed.

Confinamento de fónons ópticos em estruturas piezoelétricas periódicas e quasiperiódicas

We study the optical-phonon spectra in periodic and quasiperiodic (Fibonacci type) superlattices made up from III-V nitride materials (GaN and AlN) intercalated by a dielectric material (silica - SiO2). Due to the misalignments between the silica and the GaN, AlN layers that can lead to threading dislocation of densities as high as 1010 cm−1, and a significant lattice mismatch (_ 14%), the phonon dynamics is described by a coupled elastic and electromagnetic equations beyond the continuum dielectric model, stressing the importance of the piezoelectric polarization field in a strained condition. We use a transfer-matrix treatment to simplify the algebra, which would be otherwise quite complicated, allowing a neat analytical expressions for the phonon dispersion relation. Furthermore, a quantitative analysis of the localization and magnitude of the allowed band widths in the optical phonon s spectra, as well as their scale law are presented and discussed

Tratamento médico e fonoaudiológico da disfonia espasmódica: uma revisão bibliográfica

A disfonia espasmódica (DE) é um distúrbio vocal caracterizado por voz tensa-estrangulada, com quebras de sonoridade e que compromete a comunicação do indivíduo. O objetivo deste estudo é apresentar uma revisão bibliográfica dos tratamentos médico e fonoaudiológico proposto para a DE no período entre 2006 e 2010. Os tratamentos descritos foram: injeção de toxina botulínica (TB), miectomia, neurectomia, denervação e reinervação laríngea seletiva adutora, tireoplastia, miotermia tiroaritenóidea com radiofrequência, injeção de lidocaína, homeopatia e tratamento fonoaudiológico (fonoterapia). O uso de injeção de TB mostrou resultados que indicaram a satisfação dos pacientes tratados, embora alguns dos artigos apontassem a necessidade de reaplicação da toxina frequentemente, como desvantagem. Os procedimentos cirúrgicos foram considerados duradouros e indicados para os pacientes que não quiseram se submeter às aplicações de TB. Tais estudos, no entanto, apresentaram contingência de pacientes restrita e os resultados foram baseados, na maioria das investigações, no julgamento dos próprios pacientes sobre a sua qualidade vocal. Os tratamentos, com uso de lidocaína e homeopatia, mostraram resultados positivos em relação à qualidade vocal dos pacientes e foram sugeridos como uma opção, também, para aqueles que não gostariam de ser submetidos ao tratamento cirúrgico ou à aplicação de TB. Os poucos estudos que reportam fonoterapia assinalaram bons resultados quando a mesma foi associada à injeção de TB, mostrando a escassez de informações nesta área. Futuras pesquisas envolvendo a fonoterapia no tratamento da DE são necessárias.

Low temperature annealing of amorphous gallium arsenide films

This work reports the changes in the optical properties produced by annealing of amorphous GaAs at temperatures smaller than or just sufficient to produce crystallization of the material. The films were grown by the flash evaporation technique on glass substrates at room temperature. Optical and structural changes of our samples were monitored through photothermal deflection spectroscopy, optical transmittance and reflectance and X-ray diffraction (XRD). The structural results from XRD detected no crystallization of the films for temperatures up to 240 degreesC. We have observed consistent changes in the optical gap and Urbach energy of the annealed film. The optical gap increases with increasing annealing temperature from 1.17 to 1.32 eV. The Urbach energy decrease from 120 meV (as-grown film) to 105 meV (anneal at 200 degreesC). We propose that these changes are due to a diminution of the tail state defects and/or the relaxation of strained bonds. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Effect of temperature on the optical properties of GaAsSbN/GaAs single quantum wells grown by molecular-beam epitaxy

GaAsSbN/GaAs strained-layer single quantum wells grown on a GaAs substrate by molecular-beam epitaxy with different N concentrations were studied using the photoluminescence (PL) technique in the temperature range from 9 to 296 K. A strong redshift in optical transition energies induced by a small increase in N concentration has been observed in the PL spectra. This effect can be explained by the interaction between a narrow resonant band formed by the N-localized states and the conduction band of the host semiconductor. Excitonic transitions in the quantum wells show a successive red/blue/redshift with increasing temperature in the 2-100 K range. The activation energies of nonradiative channels responsible for a strong thermal quenching are deduced from an Arrhenius plot of the integrated PL intensity. (C) 2003 American Institute of Physics.

Nucleation and growth evolution of InP dots on InGaP/GaAs

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

Microstructure evolution during warm deformation of low carbon steel with dispersed cementite

The microstructure evolution and mechanical behavior during large strain of a 0.16%C-Mn steel has been investigated by warm torsion tests. These experiments were carried out at 685°C at equivalent strain rate of 0.1 s . The initial microstructure composed of a martensite matrix with uniformly dispersed fine cementite particles was attained by quenching and tempering. The microstructure evolution during tempering and straining was performed through interrupted tests. As the material was reheated to testing temperature, well-defined cell structure was created and subgrains within lath martensite were observed by TEM; strong recovery took place, decreasing the dislocation density. After 1 hour at the test temperature and without straining, EBSD technique showed the formation of new grains. The flow stress curves measured had a peculiar shape: rapid work hardening to a hump, followed by an extensive flow-softening region. 65% of the boundaries observed in the sample strained to ε = 1.0 were high angle grain boundaries. After straining to ε = 5.0, average ferrite grain size close to 1.5 μm was found, suggesting that dynamic recrystallization took place. Also, two sets of cementite particles were observed: large particles aligned with straining direction and smaller particles more uniformly dispersed. The fragmentation or grain subdivision that occurred during reheating and tempering time was essential for the formation of ultrafine grained microstructure.

Modelo AC para el despacho combinado de contratos bilaterales y bolsa de energía considerando restricciones de seguridad

Reliability is a key aspect in power system design and planning. Maintaining a reliable power system is a very important issue for their design and operation. Under the new competitive framework of the electricity sector, power systems find ever more and more strained to operate near their limits. Under this new scenario, it is crucial for the system operator to use tools that facilitate an energy dispatch that minimizes possible power cuts. This paper presents a mathematical model to calculate an energy dispatch that considers security constraints (single contingencies in transmission lines and transformers). The model involves pool markets and fixed bilateral contracts. Traditional methodologies that include security constraints are usually based in multistage dispatch processes. In this case, we propose a single-stage model that avoids the economic inefficiencies which result when conventional multi-stage dispatch approaches are applied. The proposed model includes an AC representation of the transport system and allows calculating the cost overruns incurred in due to reliability restrictions. We found that complying with fixed bilateral contracts, when they go above certain levels, might lead to congestion problems in transmission lines.

Avaliação de instrumentos para inserção de ligaduras elásticas em aparelho ortodôntico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

As representações sociais dos jovens do campo acerca de suas escolas

Neste trabalho objetivou-se estudar as representações sociais dos jovens do campo acerca de suas escolas no município de Bragança, Estado do Pará. Como questão central analisar as formas pelas quais acontec(;(m interferências dessas representações sociais dos jovens do campo, acerca de suas escolas,para com as práticas de inclusão-exclusão da ação educativa desencadeada nas escolas no campo. Para tanto, esta pesquisa balizou-se metodologicamente pela teoria das representações sociais para a estruturação de seu referendal teórico-metodológico de coleta e tratamento de dados e dos estudos de currículo, em uma concepção progressista, preconizada pelos movimentos sociais ligados atualmente à luta pela terra. Nesta produção, também há uma incursão acerca das condições estruturais de vivência e definição de ser jovem no campo; bem como há levantamentos conceituais relativos à educação do campo e, por conseguinte, da função social necessária às escolas do campo. As limitações curriculares, infra-estruturais e de gestão pública das unidades educacionais no campo é uma das questões transversalizadas nessa produção por se apresentar como um elemento de constituição das representações sociais dos jovens do campo acerca de suas escolas. Este estudo desdobrou-se no propósito de contribuir para com as bases de melhoria das condições de vida dos povos do campo, tendo em vista a ressignificação de algumas práticas curriculares tensionadas nas relações de inclusão-exclusão, deflagradas na ação educativa dispensada aos jovens do campo.

Effects of substrate temperature, substrate orientation, and energetic atomic collisions on the structure of GaN films grown by reactive sputtering

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

Os efeitos da matriz bioparental nos processos de adoção de crianças e adolescentes

This paper is the result of a homonymous scientific research, funded by CNPq-PIBIC where we understand the adoption process as a process of dissidence in relation to the bio-parental matrix. Founded on a heteronormative naturalization of human sexuality - which presupposes a continuum and naturalized organization among sex / gender / desire – this bioparental matrix sets the binary relation of distinction between the legitimate/illegitimate child as their origin or not arising from “blood ties”. Considering our experience in the Project developed at the Department of Clinical Psychology at UNESP, Assis, SP called “Ties of love: Adoption, Gender, Citizenship and Rights”, we prepared a content analysis - as proposed by Bardin (1977) -, of transcripts of psychological sessions that were made from 2005 to 2012 in the "Center for Research and Applied Psychology “Dra. Betti Katzenstein. Our general objective was to analyze the effects of the bioparental matrix and its impact on children/adolescents and their families as well as estimate the possibilities of escape to the subjection to this bioparental matrix. The results showed us several aspects that may be significant for understanding the discursive crossings related to the practice of adoption. It was observed that there is still a great ambivalence pervading this theme, revealing that there is a discrepancy between what we say and what we do in relation to practices of caring among the adopted children. On the one hand, it was noticed that relatives rationally seek to enhance the bonding of the “emotional ties”, but their practices and beliefs, are still supported in modes of subjectivation that prioritize the biological discourse. This fact reveals a strained and conflictive field that probably weaknesses those families seeking to prioritize the ties of affection. However, as can be seen in this study, it is comforting and motivating to realize the power of resistance of individuals to absolute truths that govern their ways of feeling, affiliating and/ or exert their parenting.

Endoscopic Laser Thyroarytenoid Myoneurectomy in Patients with Adductor Spasmodic Dysphonia: A Pilot Study on Long-Term Outcome on Voice Quality

Objectives. Adductor spasmodic dysphonia (ADSD) is a focal laryngeal dystonia, which compromises greatly the quality of life of the patients involved. It is a severe vocal disorder characterized by spasms of laryngeal muscles during speech, producing phonatory breaks, forced, strained and strangled voice. Its symptoms result from involuntary and intermittent contractions of thyroarytenoid muscle during speech, which causes vocal fold to strain, pressing each vocal fold against the other and increasing glottic resistance. Botulinum toxin injection remains the gold-standard treatment. However, as injections should be repeated periodically leading to voice quality instability, a more definitive procedure would be desirable. In this pilot study we report the long-term vocal quality results of endoscopic laser thyroarytenoid myoneurectomy. Study Design. Prospective study. Methods. Surgery was performed in 15 patients (11 females and four males), aged between 29 and 73 years, diagnosed with ADSD. Voice Handicap Index (VHI) was obtained before and after surgery (median 31 months postoperatively). Results. A significant improvement in VHI was observed after surgery, as compared with baseline values (P = 0.001). The median and interquartile range for preoperative VHI was 99 and 13, respectively and 24 and 42, for postoperative VHI. Subjective improvement of voice as assessed by the patients showed median improvement of 80%. Conclusions. Because long-term follow-up showed significant improvement of voice quality, this innovative surgical technique seems a satisfactory alternative treatment of ADSD patients who seek a definite improvement of their condition.

CdSe/CdTe interface band gaps and band offsets calculated using spin-orbit and self-energy corrections

We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane lattice parameters. For this, we employed the LDA-1/2 self-energy correction scheme [L.G. Ferreira, M. Marques, L.K. Teles, Phys. Rev. B 78 (2008) 125116] to obtain corrected band gaps and band offsets. Our calculations include the spin-orbit effects for the bulk cases, which have shown to be of importance for the equilibrium systems and are possibly degraded in these strained semiconductors. Therefore, the SO showed reduced importance for the band alignment of this particular system. Moreover, the electronic structure calculated along the transition region across the CdSe/CdTe interface shows an interesting non-monotonic variation of the band gap in the range 0.8-1.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications. (C) 2012 Elsevier B.V. All rights reserved.

In-plane mapping of buried InGaAs quantum rings and hybridization effects on the electronic structure

This work reports the investigation on the structural differences between InAs quantum rings and their precursor quantum dots species as well as on the presence of piezoelectric fields and asymmetries in these nanostructures. The experimental results show significant reduction in the ring dimensions when the sizes of capped and uncapped ring and dot samples are compared. The iso-lattice parameter mapped by grazing-incidence x-ray diffraction has revealed the lateral extent of strained regions in the buried rings. A comparison between strain and composition of dot and ring structures allows inferring on how the ring formation and its final configuration may affect optical response parameters. Based on the experimental observations, a discussion has been introduced on the effective potential profile to emulate theoretically the ring-shape confinement. The effects of confinement and strain field modulation on electron and hole band structures are simulated by a multiband k.p calculation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733964]