The rotation curves shapes of late-type dwarf galaxies

We present rotation curves derived for a sample of 62 late-type dwarf galaxies that have been observed as part of the Westerbork HI Survey of Spiral and Irregular Galaxies (WHISP) project. The rotation curves were derived by interactively fitting model data cubes to the observed cubes, taking rotation curve shape, HI distribution, inclination, and the size of the beam into account. This makes it possible to correct for the effects of beam smearing. The dwarf galaxies in our sample have rotation-curve shapes that are similar to those of late-type spiral galaxies, in the sense that their rotation curves, when expressed in units of disk scale lengths, rise as steeply in the inner parts and start to flatten at two disk scale lengths. None of the galaxies in our sample have solid-body rotation curves that extend beyond three scale lengths. The logarithmic outer rotation curve slopes are similar between late-type dwarf and spiral galaxies. Thus, whether the flat part of the rotation curve is reached seems to depend more on the extent of the rotation curve than on its amplitude. We also find that the outer rotation curve shape does not strongly depend on luminosity, at least for galaxies fainter than M_R~-19. We find that in spiral galaxies and in the central regions of late-type dwarf galaxies, the shape of the central distribution of light and the inner rise of the rotation curve are related. This implies that galaxies with stronger central concentrations of light also have higher central mass densities, and it suggests that the luminous mass dominates the gravitational potential in the central regions, even in low surface brightness dwarf galaxies.Comment: 22 pages, 2009 A&A 493, 87

A emergência do planejamento cognitivo a curto prazo: Desempenho de crianças pré-escolares em uma tarefa de resolução de problemas] [La emergencia de la planificación cognitiva a corto plazo: Desempeño de niños preescolares en una tarea de resolución de problemas

The aim of this study is to identify patterns of the cognitive planning process of young children emerging in the context of a problem solving task. Using a complex dynamic systems approach, this paper depicts the main features of cognitive planning in the short term. Participants were 45 preschool children (aged 3.5 and 3.6 years) of which two case studies are described in detail. The microgenetic method was used to capture, in two months, the planning process in real time during six sessions of data collection. Thus, 96 measuring points were obtained for each child of the sample. The instrument used was a problem solving task in a virtual format, which requires the development of a plan to attain the goal. The first part of the analysis characterizes the children’s planning performance by means of cluster analysis. Two clusters were identified as a result of this analysis. In order to illustrate the performance of the sample, one child from each cluster was randomly selected as a case study. The second part of the analysis describes the two case studies. The State Space Grids (SSG) technique was used to show the short-term emergence of cognitive planning. Results of the case studies revealed two types of performance: a reduction pattern and a stable pattern of cognitive planning. These patterns indicate the ability of children to integrate the constraints of the task and consider future states in their actions. In contrast to the literature, the findings of this study reveal the resources in planning skills of preschoolers, such as self-regulation of actions aimed at attaining a goal and anticipation of future states. © 2015, Universidad Catolica de Colombia. All rights reserved

Particularities and Universalities of the Emergence of Inductive Generalization

21 páginaInductive generalization is the primary way by which human beings arrive at the construction of knowledge. Usually, it is assumed that it operates in a linear manner—each new feature becomes “piled up” in the inductive accumulation of evidence. We question this view, and otherwise claim that inductive generalization is essentially a non-linear dynamic process that fits the theoretical premises of the Dynamic Systems Theory. In our study, we explore the ability that young infants have when making inductive generalizations -previous studies show the existence of this capacity not earlier than at the age of 14 months. These studies have been cross-sectional in nature, but they do not offer an answer to the question of emergence of cognitive capabilities, therefore, a short-term longitudinal study is needed. Based on 3 case studies carried out longitudinally in infants ranging from 9 to 14 months, we demonstrate how the process of inductive generalization occurs from a conceptualization of nonlinear dynamic systems. We use Min – Max and State Space techniques, which allow us to show how the infant uses diverse pathways of actions with everyday objects to facilitate inductive generalization. The identified paths are not the same, they present differential and common moments that confirm the dynamic nature of development, and provide empirical evidence on the emergence of non-linear, non-sequential or inductive generalization