Star Cluster Formation and Disruption Time-Scales - II. Evolution of the Star Cluster System in M82's Fossil Starburst

ABRIDGED: We obtain new age and mass estimates for the star clusters in M82's fossil starburst region B, based on improved fitting methods. Our new age estimates confirm the peak in the age histogram attributed to the last tidal encounter with M81; we find a peak formation epoch at slightly older ages than previously published, log(t_peak / yr) = 9.04, with a Gaussian sigma of Delta log(t_width) = 0.273. Cluster disruption has removed a large fraction of the older clusters. Adopting the expression for the cluster disruption time-scale of t_dis(M)= t_dis^4 (M/10^4 Msun)^gamma with gamma = 0.62 (Paper I), we find that the ratios between the real cluster formation rates in the pre-burst phase (log(t/yr) <= 9.4), the burst-phase (8.4 < log(t/yr) < 9.4) and the post-burst phase (log(t/yr) <= 8.4) are about 1:2:1/40. The mass distribution of the clusters formed during the burst shows a turnover at log(M_cl/Msun) ~ 5.3 which is not caused by selection effects. This distribution can be explained by cluster formation with an initial power-law mass function of slope alpha=2 up to a maximum cluster mass of M_max = 3 x 10^6 Msun, and cluster disruption with a normalisation time-scale t_dis^4 / t_burst = (3.0 +/- 0.3) x 10^{-2}. For a burst age of 1 x 10^9 yr, we find that the disruption time-scale of a cluster of 10^4 Msun is t_dis^4 ~ 3 x 10^7 years, with an uncertainty of approximately a factor of two. This is the shortest disruption time-scale known in any galaxy.Comment: 14 pages including 8 postscript figures; accepted for publication in MNRA

Knowing like a Pilgrim

This article opens a special issue on ”Pilgrim Knowledge” with a programmatic argument for knowledge-gathering practices as an intrinsic part of pilgrimage in the early modern Mediterranean. It addresses the history of travel, on the one hand, and the history of science and knowledge, on the other. The article then suggests that Christian pilgrimage set a special value on bodily experience, which in turn demanded practices of witnessing, collecting, comparing, codifying, and authenticating, here worked out through a range of examples. Matters of faith were also matters of fact

Circumstellar grain extinction properties of recently discovered post AGB stars

The circumstellar grains of two hot evolved post asymptotic giant branch (post AGB) stars, HD 89353 and HD 213985 were examined. From ultraviolet spectra, energy balance of the flux, and Kurucz models, the extinction around 2175 A was derived. With visual spectra, an attempt was made to detect 6614 A diffuse band absorption arising from the circumstellar grains so that we could examine the relationship of these features to the infrared features. For both stars, we did not detect any diffuse band absorption at 6614 A, implying the carrier of this diffuse band is not the carrier of the unidentified infrared features not of the 2175 A bump. The linear ultraviolet extinction of the carbon-rich star HD 89353 was determined to continue across the 2175 A region with no sign of the bump; for HD 213985 it was found to be the reverse: a strong, wide bump in the mid-ultraviolet. The 213985 bump was found to be positioned at 2340 A, longward of its usual position in the interstellar medium. Since HD 213985 was determined to have excess carbon, the bump probably arises from a carbonaceous grain. Thus, in view of the ultraviolet and infrared properties of the two post AGB stars, ubiquitous interstellar infrared emission features do not seem to be associated with the 2175 A bump. Instead, the infrared features seem related to the linear ultraviolet extinction component: hydrocarbon grains of radius less than 300 A are present with the linear HD 89353 extinction; amorphous anhydrous carbonaceous grains of radius less than 50 A might cause the shifted ultraviolet extinction bump of HD 213985

The future for global water assessment

The global water cycle is a fundamental component of our climate and Earth system. Many, if not the majority, of the impacts of climate change are water related. We have an imperfect description and understanding of components of the water cycle. This arises from an incomplete observation of some of the stores and fluxes in the water cycle (in particular: precipitation, evaporation, soil moisture and groundwater), problems with the simulation of precipitation by global climate models and the wide diversity of global hydrological models currently in use. This paper discusses these sources of errors and, in particular, explores the errors and advantages of bias correcting climate model outputs for hydrological models using a single large catchment as an example (the Rhine). One conclusion from this analysis is that bias correction is necessary and has an impact on the mean flows and their seasonal cycle. However choice of hydrological model has an equal, if not larger effect on the quality of the simulation. The paper highlights the importance of improving hydrological models, which run at a continental and global scale, and the importance of quantifying uncertainties in impact studies

Natural Exon Skipping Sets the Stage for Exon Skipping as Therapy for Dystrophic Epidermolysis Bullosa

Contains fulltext : 214010.pdf (publisher's version ) (Open Access

O impacto, sobre estudantes brasileiros, de uma linguagem visual para aprender a aprender conjuntamente

Resumo Um dos temas mais importantes na aprendizagem colaborativa apoiada pelo computador é a autorregulação da aprendizagem sem o apoio de professores. A autorregulação da colaboração pode ser definida como o conjunto dos processos sociais que os alunos usam para coordenar o seu esforço conjunto em uma atividade. Este trabalho apresenta um estudo de caso brasileiro que examina o impacto da plataforma computacional Metafora para apoiar a regulação da colaboração entre os estudantes brasileiros. Nosso objetivo é investigar se o uso da linguagem visual Metafora ajuda os alunos a aprenderem a aprender em conjunto (learn to learn togueter – L2L2). L2L2 abrange o desenvolvimento da capacidade de coordenação da colaboração. Para perseguir esse objetivo, são fornecidas evidências de mecanismos de coordenação e as respostas emocionais subjacentes ao uso, pelos alunos, da ferramenta de planejamento Metafora. Os resultados deste estudo de caso demonstram que as interações dos alunos, ao usarem a ferramenta de planejamento Metafora, influenciaram o seu desenvolvimento de L2L2 de maneira natural e envolvente. A ferramenta de planejamento Metafora proporciona aos alunos um ambiente amigável para a regulação dos processos de grupo e tem potencial para modificar os pensamentos dos estudantes com respeito à coordenação de processos colaborativos

Palaeogenomics of Upper Palaeolithic to Neolithic European hunter-gatherers

: Modern humans have populated Europe for more than 45,000 years1,2. Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period3. Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe4, but resembles that of preceding individuals associated with the Aurignacian culture. This&nbsp;ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean&nbsp;culture, and with&nbsp;the following Magdalenian culture&nbsp;that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers,&nbsp;who were also characterized by marked differences in phenotypically relevant variants