A Toy Model of Colour Screening in the Proton

In hadronic collisions, the mini-jet cross section is formally divergent in the limit pT -> 0. We argue that this divergence is tamed by some effective colour correlation length scale of the hadron. A toy model of the hadronic structure is introduced, that allows an estimate of the screening effects, and especially their energy dependence.Comment: LaTeX2e, 9 pages, 2 eps figure

Análise dos comportamentos sociais e não-sociais de crianças em idade pré-escolar: um olhar sobre as caraterísticas da criança

Domínio Científico: 2800 Developmental Psychology / 3020 Group & Interpersonal ProcessesA interação e as relações estabelecidas com os pares, durante o pré-escolar, têm um papel central no desenvolvimento da criança. O presente estudo teve como objetivo analisar a perceção que as educadoras, de crianças a frequentar o ensino pré-escolar, têm dos seus comportamentos sociais e não-sociais durante a brincadeira livre. Foram analisadas variáveis como: sexo e idade da criança, existência ou não de irmãos, idade de entrada no pré-escolar e horas diárias passadas na escola. Procurou-se, ainda, analisar de que modo caraterísticas do temperamento das crianças (descrito pela mãe) estavam ou não associadas com os seus comportamentos no contexto escolar. Vinte e sete educadoras e 105 mães de crianças entre os 23 meses e os 6 anos participaram no estudo. As educadoras responderam ao Preschool Play Behavior Scale (versão portuguesa) e as mães ao Children Behavior Questionnaire (CBQ) - versão Reduzida (versão portuguesa). Os resultados obtidos indicam que os comportamentos de Brincadeira Social são mais frequentes e aumentam com a idade, enquanto os Comportamentos Solitário-Ativo e Reticente diminuem. O Comportamento Solitário-Ativo é mais frequente nas crianças que não têm irmãos e menos frequente nas crianças que passam mais horas diárias na escola. A Brincadeira de Lutas é mais frequente no sexo masculino e nas crianças que passam mais horas diárias no pré-escolar. Relativamente às associações com as caraterísticas do temperamento, por e.g., as crianças com níveis mais elevados de Sensibilidade Percetiva, Aproximação/Entusiasmo e Extroversão apresentam mais comportamentos de Brincadeira Social. Palavras-chave: comportamentos sociais e não-sociais, pré-escolar, temperamentoThe interaction and the relationships established with peers during the preschool, play a central role in child development. This study aimed to analyze the perception that the educators of children attending preschool, have their social and non-social behavior during free play. Variables were analyzed as sex and age of the child, whether or not brothers, entry age in preschool and spent hours every day in school. It was intended to also analyze how different features of the temperament of children, described by their mothers, are associated with their behavior in school. Twenty-seven teachers and 105 mothers of children between 23 months and 6 years participated in the study. The teachers responded to Preschool Play Behavior Scale (portuguese version) and mothers to Children Behavior Questionnaire (CBQ) – “Short” version (portuguese version). The results indicate that the behavior of Social Play are more frequent and increase with age while Solitary-Active Behavior and Reticent tend to decrease. The Solitary-Active behavior is more common in children who have brothers and less frequent in children who spend more hours per day in school. Rough- Play is more frequent in males and children who spend more hours per day in preschool. About associations with the characteristics of temperament, for eg., children with higher levels of Perceptual Sensitivity, Positive Anticipation and Surgency have more social play behavior

Eclipsing binary statistics - theory and observation

The expected distributions of eclipse-depth versus period for eclipsing binaries of different luminosities are derived from large-scale population synthesis experiments. Using the rapid Hurley et al. BSE binary evolution code, we have evolved several hundred million binaries, starting from various simple input distributions of masses and orbit-sizes. Eclipse probabilities and predicted distributions over period and eclipse-depth (P/dm) are given in a number of main-sequence intervals, from O-stars to brown dwarfs. The comparison between theory and Hipparcos observations shows that a standard (Duquennoy & Mayor) input distribution of orbit-sizes (a) gives reasonable numbers and P/dm-distributions, as long as the mass-ratio distribution is also close to the observed flat ones. A random pairing model, where the primary and secondary are drawn independently from the same IMF, gives more than an order of magnitude too few eclipsing binaries on the upper main sequence. For a set of eclipsing OB-systems in the LMC, the observed period-distribution is different from the theoretical one, and the input orbit distributions and/or the evolutionary environment in LMC has to be different compared with the Galaxy. A natural application of these methods are estimates of the numbers and properties of eclipsing binaries observed by large-scale surveys like Gaia.Comment: 11 pages, 16 figures, accepted for publication in A&

Lazy Solid Texture Synthesis

International audienceExisting solid texture synthesis algorithms generate a full volume of color content from a set of 2D example images. We introduce a new algorithm with the unique ability to restrict synthesis to a subset of the voxels, while enforcing spatial determinism. This is especially useful when texturing objects, since only a thick layer around the surface needs to be synthesized. A major difficulty lies in reducing the dependency chain of neighborhood matching, so that each voxel only depends on a small number of other voxels. Our key idea is to synthesize a volume from a set of pre-computed 3D candidates, each being a triple of interleaved 2D neighborhoods. We present an efficient algorithm to carefully select in a pre-process only those candidates forming consistent triples. This significantly reduces the search space during subsequent synthesis. The result is a new parallel, spatially deterministic solid texture synthesis algorithm which runs efficiently on the GPU. Our approach generates high resolution solid textures on surfaces within seconds. Memory usage and synthesis time only depend on the output textured surface area. The GPU implementation of our method rapidly synthesizes new textures for the surfaces appearing when interactively breaking or cutting objects

Photo-physical properties of He-related color centers in diamond

Diamond is a promising platform for the development of technological applications in quantum optics and photonics. The quest for color centers with optimal photo-physical properties has led in recent years to the search for novel impurity-related defects in this material. Here, we report on a systematic investigation of the photo-physical properties of two He-related (HR) emission lines at 535 nm and 560 nm created in three different diamond substrates upon implantation with 1.3 MeV He+ ions and subsequent annealing. The spectral features of the HR centers were studied in an "optical grade" diamond substrate as a function of several physical parameters, namely the measurement temperature, the excitation wavelength and the intensity of external electric fields. The emission lifetimes of the 535 nm and 560 nm lines were also measured by means of time-gated photoluminescence measurements, yielding characteristic decay times of (29 +- 5) ns and (106 +- 10) ns, respectively. The Stark shifting of the HR centers under the application of an external electrical field was observed in a CVD diamond film equipped with buried graphitic electrodes, suggesting a lack of inversion symmetry in the defects' structure. Furthermore, the photoluminescence mapping under 405 nm excitation of a "detector grade" diamond sample implanted at a 1x1010 cm-2 He+ ion fluence enabled to identify the spectral features of both the HR emission lines from the same localized optical spots. The reported results provide a first insight towards the understanding of the structure of He-related defects in diamond and their possible utilization in practical applicationsComment: 9 pages, 3 figure

Interactive out-of-core visualisation of 4-D+t plasma data

This research report presents a new interactive visualisation technique for exploring plasma behaviors resulting from 4-D+t numerical simulations on regular grids. Therefore, a new out-of-core 4-D+t scalar field visualisation technique, based on a « focus and context » approach is presented. The latter uses a hybrid data compression method. The originality of this work precisely consists in coupling the 3-D visualization with the progressive load and decompression of data in such a way that it still guarantees real-time framerates even on low-end PCs while maintaining a high degree of numerical precision