Deconstructing double-barred galaxies in 2D and 3D. II. Two distinct groups of inner bars

The intrinsic photometric properties of inner and outer stellar bars within 17 double-barred galaxies are thoroughly studied through a photometric analysis consisting of: i) two-dimensional multi-component photometric decompositions, and ii) three-dimensional statistical deprojections for measuring the thickening of bars, thus retrieving their 3D shape. The results are compared with previous measurements obtained with the widely used analysis of integrated light. Large-scale bars in single- and double-barred systems show similar sizes, and inner bars may be longer than outer bars in different galaxies. We find two distinct groups of inner bars attending to their in-plane length and ellipticity, resulting in a bimodal behaviour for the inner/outer bar length ratio. Such bimodality is related neither to the properties of the host galaxy nor the dominant bulge, and it does not show a counterpart in the dimension off the disc plane. The group of long inner bars lays at the lower end of the outer bar length vs. ellipticity correlation, whereas the short inner bars are out of that relation. We suggest that this behaviour could be due to either a different nature of the inner discs from which the inner bars are dynamically formed, or a different assembly stage for the inner bars. This last possibility would imply that the dynamical assembly of inner bars is a slow process taking several Gyr to happen. We have also explored whether all large-scale bars are prone to develop an inner bar at some stage of their lives, possibility we cannot fully confirm or discard.Comment: 14 pages, 8 figures, 1 table. Accepted for publication in MNRA

Compostagem laminar em sistema orgânico de banana.

A utilização de práticas agrícolas não convencionais capazes de melhorar os atributos físicos, químicos e biológicos do solo é fundamental no sistema orgânico. A compostagem laminar, com o aproveitamento de resíduos orgânicos de baixo custo e fácil disponibilidade, é uma alternativa que pode ser viável.PDF. 139_11

Ecologização da agricultura e das relações inovadoras com o mercado: situação atual e perspectivas no Brasil.

Este texto analisa o desenvolvimento da agricultura agroecológica e orgânica no Brasil. Apresenta uma grande diversidade social e de modelos de produção reconhecidos pela legislação brasileira: orgânica, agroecológica, ecológica, biodinâmica, permacultura, etc. Descreve sinteticamente como as políticas e os interesses sociais ligados às questões da agricultura familiar e do meio ambiente causaram a reorganização dos sistemas de produção, em termos de práticas agrícolas e de novas relações com mercados e com os recursos naturais. A análise foi baseada em entrevistas com agricultores e agentes envolvidos no desenvolvimento de vários modelos orgânicos; qualifica os modelos de produção assim como os valores socioculturais relacionados. Apresenta também alguns aspectos das raízes históricas do movimento agroecológico brasileiro e as maneiras como os agricultores familiares se adaptam aos novos interesses da produção ecológica

Young peoples’ reflections on what teachers think about family obligations that conflict with school: A focus on the non-normative roles of young caring and language brokering

In “Western” contexts school attendance is central for an ‘ideal’ childhood. However, many young people engage with home roles that conflict with school expectations. This paper explores perceptions of that process in relation two home activities - language brokering and young caring. We interviewed 46 young people and asked them to reflect on what the teacher would think when a child had to miss school to help a family member. This paper discusses the young people’s overall need to keep their out-of-school lives private from their teachers

Sound Speeds, Cracking and Stability of Self-Gravitating Anisotropic Compact Objects

Using the the concept of cracking we explore the influence of density fluctuations and local anisotropy have on the stability of local and non-local anisotropic matter configurations in general relativity. This concept, conceived to describe the behaviour of a fluid distribution just after its departure from equilibrium, provides an alternative approach to consider the stability of selfgravitating compact objects. We show that potentially unstable regions within a configuration can be identify as a function of the difference of propagations of sound along tangential and radial directions. In fact, it is found that these regions could occur when, at particular point within the distribution, the tangential speed of sound is greater than radial one.Comment: 17 pages, 8 figures, 4 new references added. typos correcte