The rotation of the Earth around its own axis and around the sun determines the characteristics of the light/dark cycle, the most stable and ancient 24 h temporal cue for all organisms. Due to the tilt in the earth’s axis in relation to the plane of the earth’s orbit around the sun, sunlight reaches the Earth differentially depending on the latitude. The timing of circadian rhythms varies among individuals of a given population and biological and environmental factors underlie this variability. In the present study, we tested the hypothesis that latitude is associated to the regulation of circadian rhythm in humans. We have studied chronotype profiles across latitudinal cline from around 0° to 32° South in Brazil in a sample of 12,884 volunteers living in the same time zone. The analysis of the results revealed that humans are sensitive to the different sunlight signals tied to differences in latitude, resulting in a morning to evening latitudinal cline of chronotypes towards higher latitudes.

ResumoEste trabalho expande a normatização brasileira do International Affective Picture System (IAPS), um instrumento de imagens afetivas, amplamente utilizado em pesquisas, com valores normativos para 240 novos estímulos, e confirma as categorias de imagens "agradáveis", "neutras" e "desagradáveis". Também são apresentados os resultados comparando os padrões de respostas de homens e mulheres. No total, participaram 448 estudantes universitários brasileiros (179 homens e 269 mulheres), que avaliaram as fotografias em termos de prazer, alerta e dominância, através da escala Self Assessment Manikin (SAM). O procedimento adotado foi o mesmo de outro estudo já desenvolvido para as normas norte-americanas. Descritores: IAPS, emoção, diferenças sexuais, prazer, alerta. AbstractThis study includes the standardization of 240 new stimuli in the Brazilian norms for the International Affective Picture System (IAPS), an instrument of affective images widely used in research, and confirms the validity of the categories of "pleasant," "neutral" and "unpleasant" pictures. A comparison was performed of the scores of affective ratings between the male and female samples of university students (179 males, and 269 females), who assessed the affective content of photographs in terms of valence, arousal and dominance using the Self Assessment Manikin (SAM) scale. The methods were the same used in a study conducted for the American norms. Keywords: IAPS, emotion, sex differences, valence, arousal. IntroduçãoO International Affective Picture System (IAPS) 1 é um instrumento de imagens afetivas que abordam diferentes eventos da vida e valores veiculados pela mídia presentes na cultura geral de muitos países (como família, esporte, sexualidade, violência, saúde, etc.). Por ser um instrumento eficiente na indução de diferentes estados emocionais e permitir grande nível de controle dos parâmetros de exposição e mensuração em contextos experimentais, o IAPS tem sido amplamente utilizado em pesquisas na área da cognição, do afeto, do comportamento, das atitudes sociais, da psicofisiologia, entre outras, tanto para estudar pacientes com distúrbios neuropsiquiátricos quanto populações saudáveis.Estudos têm demonstrado que os principais fatores implicados na experiência emocional são o prazer e o Rev Psiquiatr RS. 2008;30(3):230-235

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Let $\Xi$ be the set of points (we call the elements of $\Xi$ centers) of Poisson process in $\R^d$, $d\geq 2$, with unit intensity. Consider the allocation of $\R^d$ to $\Xi$ which is stable in the sense of Gale-Shapley marriage problem and in which each center claims a region of volume $\alpha\leq 1$. We prove that there is no percolation in the set of claimed sites if $\alpha$ is small enough, and that, for high dimensions, there is percolation in the set of claimed sites if $\alpha<1$ is large enough.Comment: revised version (only minor correction since v2), 16 pages, 3 figure

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