Coupled dark matter-dark energy in light of near Universe observations

Cosmological analysis based on currently available observations are unable to rule out a sizeable coupling among the dark energy and dark matter fluids. We explore a variety of coupled dark matter-dark energy models, which satisfy cosmic microwave background constraints, in light of low redshift and near universe observations. We illustrate the phenomenology of different classes of dark coupling models, paying particular attention in distinguishing between effects that appear only on the expansion history and those that appear in the growth of structure. We find that while a broad class of dark coupling models are effectively models where general relativity (GR) is modified --and thus can be probed by a combination of tests for the expansion history and the growth of structure--, there is a class of dark coupling models where gravity is still GR, but the growth of perturbations is, in principle modified. While this effect is small in the specific models we have considered, one should bear in mind that an inconsistency between reconstructed expansion history and growth may not uniquely indicate deviations from GR. Our low redshift constraints arise from cosmic velocities, redshift space distortions and dark matter abundance in galaxy voids. We find that current data constrain the dimensionless coupling to be |xi|<0.2, but prospects from forthcoming data are for a significant improvement. Future, precise measurements of the Hubble constant, combined with high-precision constraints on the growth of structure, could provide the key to rule out dark coupling models which survive other tests. We shall exploit as well weak equivalence principle violation arguments, which have the potential to highly disfavour a broad family of coupled models.Comment: 34 pages, 6 figures; changes to match published versio

Water-induced modulation of Helicobacter pylori virulence properties

While the influence of water in Helicobacter pylori culturability and membrane integrity has been extensively studied, there are little data concerning the effect of this environment on virulence properties. Therefore, we studied the culturability of water-exposed H. pylori and determined whether there was any relation with the bacterium’s ability to adhere, produce functional components of pathogenicity and induce inflammation and alterations in apoptosis in an experimental model of human gastric epithelial cells. H. pylori partially retained the ability to adhere to epithelial cells even after complete loss of culturability. However, the microorganism is no longer effective in eliciting in vitro host cell inflammation and apoptosis, possibly due to the non-functionality of the cag type IV secretion system. These H. pylori-induced host cell responses, which are lost along with culturability, are known to increase epithelial cell turnover and, consequently, could have a deleterious effect on the initial H. pylori colonisation process. The fact that adhesion is maintained by H. pylori to the detriment of other factors involved in later infection stages appears to point to a modulation of the physiology of the pathogen after water exposure and might provide the microorganism with the necessary means to, at least transiently, colonise the human stomach.FCT (SFRH/BD/24579/2005) (to NMG

Debating dams: The World Commission on Dams 20 years on

The World Commission on Dams (WCD) was a global environmental governance forum that worked between 1998 and 2000 to try to resolve long-standing controversies between supporters and opponents of large dams. Its objectives were to assess the development effectiveness of large dams and to develop best practice guidelines for large dam construction and management, based on an extensive review of scientific evidence and wide-ranging stakeholder consultation. This paper reviews literature discussing the WCD, to understand its influence on the debate on large dams and beyond. We find that its influence is debated within four main contexts: (i) interpretations of stakeholder responses to the WCD report and recommendations; (ii) the persistence of the kinds of impacts of large dams that gave rise to the Commission’s work; (iii) the different visions for appropriate follow-up strategies; (iv) insights from the WCD experience in the context of global environmental governance. Within these four contexts, we identify diverse opinions and directions of post-WCD development and sources of disagreement on its merits and legacy, ranging from calls for its full implementation to dismissal and opposition. Commentators also differ in their assessment of whether the WCD sparked truly novel insights and propositions for dam decision-making or whether it simply represented one among many other elements in the broader debate on dams. Most commonly, the WCD’s work is cited in the context of persistent negative social and environmental impacts of dams: neither the impacts nor the controversy over large dams have ended