Large-signal dynamic behavior of distributed-feedback lasers including lateral effects

The large-signal behavior of DFB lasers is analyzed, including lateral as well as longitudinal variations in carrier density, photon density, and refractive index. The effective index method and other approximations are used to reduce the complex three-dimensional problem to one dimension. The coupled wave and carrier rate equations are then solved in a self-consistent manner. Lateral spatial carrier hole burning and lateral diffusion are found to affect the relaxation oscillation frequency and damping rate of DFB lasers, depending on their detailed structure. The effective time-averaged linewidth enhancement factor is also affected. In symmetric AR-coated λ/4 phase-shifted lasers the side mode suppression ratio can be deteriorated significantly by lateral spatial hole burning when kL is large.published_or_final_versio

STM and RHEED study of the Si(001)-c(8x8) surface

The Si(001) surface deoxidized by short annealing at T~925C in the ultrahigh vacuum molecular beam epitaxy chamber has been in situ investigated by high resolution scanning tunnelling microscopy (STM) and reflected high energy electron diffraction (RHEED). RHEED patterns corresponding to (2x1) and (4x4) structures were observed during sample treatment. The (4x4) reconstruction arose at T<600C after annealing. The reconstruction was observed to be reversible: the (4x4) structure turned into the (2x1) one at T>600C, the (4x4) structure appeared again at recurring cooling. The c(8x8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8x8) structure decreased as the sample cooling rate was reduced. The (2x1) structure was observed on the surface free of the c(8x8) one. The c(8x8) structure has been evidenced to manifest itself as the (4x4) one in the RHEED patterns. A model of the c(8x8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.Comment: 26 pages, 12 figure

The Jurassic–Cretaceous depositional and tectonic evolution of the southernwestern margin of the Neotethys Ocean, Northern Oman and United Arab Emirates

The concept that the autochthonous, parautochthonous and allochthonous Permian–Cretaceous sequences in the United Arab Emirates (UAE) and Oman record the transition from platform, slope to basin sedimentation within the southern part of Neotethys has been fundamental to the interpretation of the geological history of the region. The results of a major geological mapping programme of the UAE, carried out by the British Geological Survey for the Federal Government of the UAE, coupled with the detailed examination of key sections within northern Oman has led to a re-evaluation of the geological evolution of this region. This detailed study has led to a greater appreciation of the sedimentology and depositional setting of the sediments laid down along the northeastern Arabian continental margin during the Jurassic to Cretaceous, allowing a more refined model of Neotethys Ocean basin evolution to be established. The model charts the progressive breakup of the Arabian continental margin and closure of Neotethys during the mid to late Cretaceous and is divided into three main stages: Stage 1—Initial rifting and formation of the Neotethys Ocean, followed by a prolonged period of stable, passive margin sedimentation which extended from the Permian to Late Jurassic times; Stage 2—Uplift and erosion of the shelf margin during the Late Jurassic to Early Cretaceous, coincident with increased carbonate-clastic sedimentation in the outer ramp, distal slope and basinal areas; Stage 3—Increased instability during the Late Cretaceous leading to the breakup of the platform margin and foreland basin sedimentation accompanying the obduction of the Oman-UAE ophiolite. Data obtained for the upper part of the platform and platform margin to slope successions has revealed that the topography of the “shelf”-slope-basinal margin was more subdued than previously thought, with this more gentle ramp margin morphology persisting until early to mid-Cretaceous times when the platform margin started to become unstable during ophiolite obduction. The thrust-repeated allochthonous sedimentary rocks of the Hamrat Duru Group were deposited on the outer platform margin/lower slope rise to basinal plain of this basin margin and includes the dismembered remains of two turbidite fan systems which fed carbonate-rich detritus into deeper parts of the ocean. A re-evaluation of the chert-rich sequences, previously equated with deposition on the abyssal plain of Neotethys, has led to the conclusion that they may record sedimentation at a much shallower level within a starved ocean basin, possibly in a mid-ramp (above storm wave base) to outer ramp setting. A marked change in basin dynamics occurred during the mid-Cretaceous leading to the development of a shallow ramp basin margin in Oman with terrestrial to shallow marine sedimentary rocks interdigitating with red siliceous mudstones. By contrast, the contemporaneous succession in the Dibba Zone of the UAE indicates considerable instability on a steep shelf break. This instability is recorded by the presence of several major olistostrome deposits within the Aruma Group of the UAE which are thought to have been generated in advance of the rapidly obducting Oman-UAE ophiolite

O viés político-alegórico no romance sul-rio-grandense: Mês de cães danados, de Moacyr Scliar

A literatura do Rio Grande do Sul não foge à polêmica relação entre literatura e política. No sistema literário gaúcho também se questiona se é possível ao escritor isentar-se da política. Ao lado dessa questão, ainda há outra: a politização da literatura não envolve o perigo do seu empobrecimento estético e da sua redução à forma panfletária? Nem todo autor politicamente engajado produz boas obras literárias; por outro lado, autores que não tiveram a pretensão de escrever romances políticos, terminaram por nos legar obras essenciais. Considerando esses pressupostos, este artigo contempla reflexões sobre Mês de cães danados, publicado em 1977, por Moacyr Scliar, no qual o autor lança um olhar mais aguçado para a moderna história política brasileira, mais especificamente para a questão da dessacralização da tradição do passado sulino, por meio do episódio da Legalidade – movimento liderado pelo então governador do Rio Grande do Sul, Leonel Brizola, em favor da posse legítima de João Goulart, após a renúncia do presidente Jânio Quadros, em agosto de 1961.PALAVRAS-CHAVE: Alegoria; romance; Mês dos cães danados

A Senhorita Simpson, de Sérgio Sant’Anna, e Bossa nova, de Bruno Barreto: diálogos entre literatura e cinema

O objetivo principal deste artigo é refletir sobre diálogos entre literatura e cinema, amparando-se nos pressupostos metodológicos da Literatura Comparada, para discutir a adaptação cinematográfica da obra literária A senhorita Simpson, de Sérgio Sant’Anna para a película Bossa Nova, de Bruno Barreto. A análise da composição e dos eixos temáticos do filme permite o reconhecimento de suas semelhanças e divergências em relação ao texto literário, acentuando que o filme, embora se inspire no romance, é uma criação pessoal do cineasta, que, no caso de Bruno Barreto, não demonstra preocupação em reproduzir (fielmente), em uma outra linguagem (a cinematográfica), a obra original.PALAVRAS-CHAVE: Literatura; cinema; adaptação

Atomic-scale structure and properties of highly stable antiphase boundary defects in Fe3O4

The complex and intriguing properties of the ferrimagnetic half metal magnetite (Fe3O4) are of continuing fundamental interest as well as being important for practical applications in spintronics, magnetism, catalysis and medicine. There is considerable speculation concerning the role of the ubiquitous antiphase boundary (APB) defects in magnetite, however, direct information on their structure and properties has remained challenging to obtain. Here we combine predictive first principles modelling with high-resolution transmission electron microscopy to unambiguously determine the three-dimensional structure of APBs in magnetite. We demonstrate that APB defects on the {110} planes are unusually stable and induce antiferromagnetic coupling between adjacent domains providing an explanation for the magnetoresistance and reduced spin polarization often observed. We also demonstrate how the high stability of the {110} APB defects is connected to the existence of a metastable bulk phase of Fe3O4, which could be stabilized by strain in films or nanostructures

Desinfecção de moldes e modelos: avaliação da prática de biossegu-rança dos consultórios particulares no município de Vassouras-RJ

É importante estabelecer medidas preventivas para evitar a contaminação cruzada, sendo a desinfecção de moldes e modelos um dos procedimentos indispensáveis para a biossegurança na prática clínica. O objetivo deste trabalho foi avaliar o grau de informação que os cirurgiões-dentistas do município de Vassouras têm sobre a importância da desinfecção de moldes e modelos. Como fatores de estudo, foram selecionados os consultórios particulares com uma consulta à Secretaria Municipal de Saúde. Acadêmicos do Curso de Odontologia da Universidade Severino Sombra, previamente calibrados, realizaram as visitas aos consultórios com um questionário pontuando dados como a freqüência de desinfecção e substâncias químicas utilizadas. Observou-se que 100% dos cirurgiões-dentistas já ouviram falar sobre a desinfecção de moldes e modelos, e 92,86% consideraram um procedimento importante e ainda 64,28% realizam a desinfecção de moldes e modelos. O hipoclorito de sódio foi citado em 76,92% e o glutaraldeído em 30,76%, porém todos utilizavam estas substâncias químicas em concentrações e métodos inadequados. Concluiu-se que a maioria dos cirurgiões-dentistas do município de Vassouras realiza os procedimentos de desinfecção de moldes e modelos, porém, utilizam substâncias químicas e métodos de desinfecção inadequados

Shwachman-Bodian-Diamond syndrome (SBDS) protein is a direct inhibitor of protein phosphatase 2A (PP2A) activity and overexpressed in acute myeloid leukaemia.

Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase inactivated in many cancers including acute myeloid leukaemia (AML). Activation of PP2A is emerging as a therapeutic strategy, however the mechanisms underpinning PP2A inhibition are not well understood. Using myeloid progenitor cells harbouring oncogenic mutant c-KIT and characterised by PP2A inhibition, we have identified the ribosome biogenesis protein SBDS, as a target of the PP2A activating drugs FTY720 and AAL(S). We show SBDS binds to PP2A complexes comprised of the B55α regulatory subunit of PP2A. shRNA mediated knockdown of SBDS increased PP2A activity and induced apoptosis. At diagnosis, AML patients expressed significantly more SBDS mRNA than healthy controls, with relapsed patients expressing significantly more SBDS mRNA than both healthy controls and patients at diagnosis. Together, our data presents a role for SBDS in the dysregulation of PP2A in AML