Arctic in Rapid Transition (ART) : science plan

The Arctic is undergoing rapid transformations that have brought the Arctic Ocean to the top of international political agendas. Predicting future conditions of the Arctic Ocean system requires scientific knowledge of its present status as well as a process-based understanding of the mechanisms of change. The Arctic in Rapid Transition (ART) initiative is an integrative, international, interdisciplinary pan-Arctic program to study changes and feedbacks among the physical and biogeochemical components of the Arctic Ocean and their ultimate impacts on biological productivity. The goal of ART is to develop priorities for Arctic marine science over the next decade. Three overarching questions form the basis of the ART science plan: (1) How were past transitions in sea ice connected to energy flows, elemental cycling, biological diversity and productivity, and how do these compare to present and projected shifts? (2) How will biogeochemical cycling respond to transitions in terrestrial, gateway and shelf-to-basin fluxes? (3) How do Arctic Ocean organisms and ecosystems respond to environmental transitions including temperature, stratification, ice conditions, and pH? The integrated approach developed to answer the ART key scientific questions comprises: (a) process studies and observations to reveal mechanisms, (b) the establishment of links to existing monitoring programs, (c) the evaluation of geological records to extend time-series, and (d) the improvement of our modeling capabilities of climate-induced transitions. In order to develop an implementation plan for the ART initiative, an international and interdisciplinary workshop is currently planned to take place in Winnipeg, Canada in October 2010

XMM-Newton observation of the bright Seyfert 1 galaxy, MCG+8-11-11

We report on the XMM-Newton observation of the bright Seyfert 1 galaxy, MCG+8-11-11. Data from the EPIC/p-n camera, the Reflection Gratings Spectrometers (RGS) and the Optical Monitor (OM) have been analyzed. The p-n spectrum is well fitted by a power law, a spectrally unresolved Fe Kalpha line, a Compton reflection component (whose large value, when compared to the iron line equivalent width, suggests iron underabundance), and absorption by warm material. Absorption lines are apparent in the RGS spectra, but their identification is uncertain and would require large matter velocities. The UV fluxes measured by the OM are well above the extrapolation of the X-ray spectrum, indicating the presence of a UV bump.Comment: 7 pages. Accepted for publication in Astronomy & Astrophysic

The transcriptional landscape of αβ T cell differentiation

αβT cell differentiation from thymic precursors is a complex process, explored here with the breadth of ImmGen expression datasets, analyzing how differentiation of thymic precursors gives rise to transcriptomes. After surprisingly gradual changes though early T commitment, transit through the CD4+CD8+ stage involves a shutdown or rare breadth, and correlating tightly with MYC. MHC-driven selection promotes a large-scale transcriptional reactivation. We identify distinct signatures that mark cells destined for positive selection versus apoptotic deletion. Differential expression of surprisingly few genes accompany CD4 or CD8 commitment, a similarity that carries through to peripheral T cells and their activation, revealed by mass cytometry phosphoproteomics. The novel transcripts identified as candidate mediators of key transitions help define the “known unknown” of thymocyte differentiation

The Arctic in Rapid Transition (ART) Initiative: integrating priorities for Arctic marine science over the next decade

The Arctic is currently undergoing rapid environmental and economic transformations. Recent and ongoing climate warming which is simplifying access to oil and gas resources, enabling trans-Arctic shipping and shifting the distribution of harvestable resources, has brought the Arctic Ocean to the top of national and international political agendas. Scientific knowledge of the present status of the Arctic Ocean and the process-based understanding needed to make predictions throughout the arctic region are thus urgently required. A step towards improving our capacity to predict future arctic change was undertaken with the Second International Conference on Arctic Research Planning (ICARP II) meetings in 2005 and 2006 which brought together scientists, policymakers, research managers, arctic residents and other stakeholders interested in the future of arctic climate change research. The Arctic in Rapid Transition (ART) Initiative developed out of an effort to synthesize the several resulting ICARP II science plans specific to the marine environment and has been a process driven by the early career scientists of the ICARP II Marine Roundtable. To this end, the ART Initiative is an integrative, international, multi-disciplinary, long-term pan-Arctic program to study changes and feedbacks among the physical characteristics and biogeochemical cycles of the Arctic Ocean and its' resulting capacity for biological productivity. The first ART workshop was held in Fairbanks, Alaska in November 2009 with 58 participants, the results of which will help to develop a science and implementation plan that integrates, updates and develops priorities for arctic marine science over the next decade. Our focus within the ART Initiative will be to bridge gaps in knowledge not only across disciplinary boundaries (e.g., geology, biology, physical oceanography, geochemistry and meteorology), but also across geographic boundaries (e.g., shelves, margins and the central Arctic Ocean) and temporal boundaries (e.g., paleo/geologic records, current process observations and future modeling studies). This interdisciplinary, international and integrated temporal approach of the ART Initiative will provide a means to better understand and predict change and ultimate responses in the Arctic Ocean system. More information about the ART Initiative can be found at www.aosb.org/art.html

RACE-OC Project: Rotation and variability in the epsilon Chamaeleontis, Octans, and Argus stellar associations

We aim at determining the rotational and magnetic-related activity properties of stars at different stages of evolution. We focus our attention primarily on members of young stellar associations of known ages. Specifically, we extend our previous analysis in Paper I (Messina et al. 2010, A&A 520, A15) to 3 additional young stellar associations beyond 100 pc and with ages in the range 6-40 Myr: epsilon Chamaeleontis (~6 Myr), Octans (~20 Myr), and Argus (~40 Myr). Additional rotational data of eta Chamaeleontis and IC2391 clusters are also considered. Rotational periods were determined from photometric time-series data obtained by the All Sky Automated Survey (ASAS) and the Wide Angle Search for Planets (SuperWASP) archives. With the present study we have completed the analysis of the rotational properties of the late-type members of all known young loose associations in the solar neighborhood. Considering also the results of Paper I, we have derived the rotation periods of 241 targets: 171 confirmed, 44 likely, 26 uncertain. The period of the remaining 50 stars known to be part of loose associations still remains unknown. This rotation period catalogue, and specifically the new information presented in this paper at ~6, 20, and 40 Myr, contributes significantly to a better observational description of the angular momentum evolution of young stars.Comment: Accepted by Astronomy & Astrophysics. Onlines figures will be available at CD

On the Location and Composition of the Dust in the MCG-6-30-15 Warm Absorber

Hubble Space Telescope images of MCG-6-30-15 show a dust lane crossing the galaxy just below the nucleus. In this paper, we argue that this dust lane is responsible for the observed reddening of the nuclear emission and the Fe I edge hinted at in the Chandra spectrum of MCG-6-30-15. We further suggest that the gas within the dust lane can comprise much of the low ionization component (i.e., the one contributing the O VII edge) of the observed warm absorber. Moreover, placing the warm absorbing material at such distances (hundreds of pc) can account for the small outflow velocities of the low ionization absorption lines as well as the constancy of the O VIII edge. Photoionization models of a dusty interstellar gas cloud (with a column appropriate for the reddening toward MCG-6-30-15) using a toy Seyfert 1 spectral energy distribution show that it is possible to obtain a significant O VII edge (\tau~0.2) if the material is ~150 pc from the ionizing source. For MCG-6-30-15, such a distance is consistent with the observed dust lane. The current data on MCG-6-30-15 is unable to constrain the dust composition within the warm absorber. Astronomical silicate is a viable candidate, but there are indications of a very low O abundance in the dust, which is inconsistent with a silicate origin. If true, this may indicate that there were repeated cycles of grain destruction and growth from shocks in the interstellar medium of MCG-6-30-15. Pure iron grains are an unlikely dust constituent due to the limit on their abundance in the Galaxy, yet they cannot be ruled out. The high column densities inferred from the highly ionized zone of the warm absorber implies that this gas is dust-free.Comment: 7 pages, 3 Figures, A&A accepte