On the space of ergodic measures for the horocycle flow on strata of abelian differentials

We study the horocycle flow on the stratum of abelian differentials H(2). We show that there is a sequence of horocycle ergodic measures, each supported on a periodic horocycle orbit, which weakly converges to an invariant, but non-ergodic, measure by SL2(R). As a consequence, we show that there are points in H(2) whose horocycle flow orbits do not equidistribute towards any invariant measure

SkyMapper Southern Survey: First Data Release (DR1)

We present the first data release (DR1) of the SkyMapper Southern Survey, a hemispheric survey carried out with the SkyMapper Telescope at Siding Spring Observatory in Australia. Here, we present the survey strategy, data processing, catalogue construction and database schema. The DR1 dataset includes over 66,000 images from the Shallow Survey component, covering an area of 17,200 deg$^2$ in all six SkyMapper passbands $uvgriz$, while the full area covered by any passband exceeds 20,000 deg$^2$. The catalogues contain over 285 million unique astrophysical objects, complete to roughly 18 mag in all bands. We compare our $griz$ point-source photometry with PanSTARRS1 DR1 and note an RMS scatter of 2%. The internal reproducibility of SkyMapper photometry is on the order of 1%. Astrometric precision is better than 0.2 arcsec based on comparison with Gaia DR1. We describe the end-user database, through which data are presented to the world community, and provide some illustrative science queries.Comment: 31 pages, 19 figures, 10 tables, PASA, accepte

Expression of α7 neuronal nicotinic receptors during postnatal development of the rat cerebellum

Several lines of evidence suggest that α-bungarotoxin-sensitive neuronal nicotinic acetylcholine receptors may play a developmental role by modulating plasticity in neuronal circuits. The α7 subunit, a main component of these receptors, is expressed in most regions of the brain, including the cerebellum, where it is present almost exclusively in Purkinje cells and deep cerebellar nuclei. Purkinje cells constitute the only efferent pathway of the cerebellum and their development involves complex interactions, which have been extensively studied. They therefore provide a potentially useful model for analysis of developmental plasticity which could be influenced by α7 neuronal nicotinic receptors. In the present study a previously characterized monoclonal antibody (mAb 307) has been used to determine the temporal pattern of expression of the α7 subunit in the developing rat cerebellum. No detectable α7 immunoreactivity is found between P0 and P2. Between P3 and P5, however, the Purkinje cell layer shows moderate immunolabeling. α7 expression in this layer increases rapidly between P8 and P15. This increase in α7 staining, which overlaps in time with important developmental and synaptogenic events, is not uniform throughout the cerebellar cortex. Thus, between P3 and P5 all Purkinje cells are weakly labeled, while at later stages (P8–P15) immunolabeling becomes more intense but, at the same time, disappears from Purkinje cells in rostral lobules. In addition, a very well defined pattern of discontinuous or columnar labeling is detected in regions of the Purkinje cell layer where α7 subunits are being expressed. Finally, at P20, α7 subunit labeling is found again in all Purkinje cells, although with lower intensity. These results suggest that α7 receptor expression is developmentally regulated, with a time course that parallels the final differentiation of Purkinje cells. In addition, the heterogeneous spatial distribution of α7-containing nicotinic receptors indicates that, during cerebellar maturation, these cells may receive different signals that modulate receptor gene expression in a very specific way.This work was supported by grants from the Ministries of Education (DGICYT, PB92-0346 and PB93-0931) and Health (Fis 95-1672) of Spain, the Commission of the European Economic Community (SC1*CT91-0666) and the Wellcome Trust (039284). E.D. del T. was the recipient of a predoctoral fellowship from the Ministry of Education of Spain. F.I.S. was a postdoctoral fellow of the Wellcome Trust. J.L. is supported by grants from the NIH (NS11323), the MDA, the Council for Tobacco Research, Inc., and the Council for Smokeless Tobacco Research, Inc.Peer reviewe

Unraveling the processes shaping mammalian gut microbiomes over evolutionary time

Whether mammal–microbiome interactions are persistent and specific over evolutionary time is controversial. Here we show that host phylogeny and major dietary shifts have affected the distribution of different gut bacterial lineages and did so on vastly different bacterial phylogenetic resolutions. Diet mostly influences the acquisition of ancient and large microbial lineages. Conversely, correlation with host phylogeny is mostly seen among more recently diverged bacterial lineages, consistent with processes operating at similar timescales to host evolution. Considering microbiomes at appropriate phylogenetic scales allows us to model their evolution along the mammalian tree and to infer ancient diets from the predicted microbiomes of mammalian ancestors. Phylogenetic analyses support co-speciation as having a significant role in the evolution of mammalian gut microbiome compositions. Highly co-speciating bacterial genera are also associated with immune diseases in humans, laying a path for future studies that probe these co-speciating bacteria for signs of co-evolution.National Science Foundation (U.S.) (0821391

The NCI High Performance Computing and High Performance Data Platform to Support the Analysis of Petascale Environmental Data Collections

Part 8: High Performance Computing and BigDataInternational audienceThe National Computational Infrastructure (NCI) at the Australian National University (ANU) has co-located a priority set of over 10 PetaBytes (PBytes) of national data collections within a HPC research facility. The facility provides an integrated high-performance computational and storage platform, or a High Performance Data (HPD) platform, to serve and analyse the massive amounts of data across the spectrum of environmental collections – in particular from the climate, environmental and geoscientific domains. The data is managed in concert with the government agencies, major academic research communities and collaborating overseas organisations. By co-locating the vast data collections with high performance computing environments and harmonising these large valuable data assets, new opportunities have arisen for Data-Intensive interdisciplinary science at scales and resolutions not hitherto possible

SkyMapper's Southern Sky Survey : Early Data Release (EDR)

The SkyMapper Early Data Release (EDR) is the initial data release from the SkyMapper Southern Survey, which aims to create a deep, multi-epoch, multi-band photometric data set for the entire southern sky. EDR covers approximately 6700 sq. deg. (one-third) of the southern sky as obtained by the Short Survey component of the project. All included fields have at least two visits in good conditions in all six SkyMapper filters (uvgriz). Object catalogues are complete to magnitude 17-18, depending on filter. IVOA-complaint table access protocol (TAP), cone search and simple image access protocol (SIAP) services are available from the SkyMapper website (http://skymapper.anu.edu.au/), as well as through tools such as TOPCAT. Data are restricted to Australian astronomers and their collaborators for twelve months from the release date. Further details on the reduction of SkyMapper data, along with data quality improvements, will be released in late 2016 as part of SkyMapper Data Release 1 (DR1

SkyMapper Main Survey

Most of SkyMapper's observing time is now dedicated to the Main Survey. The survey scheduler aims to finish a field mostly within one moon period. A first visit in dark conditions establishes a colour sequence with all six bands observed in the space of 20 minutes. Further visits in subsequent nights under dark or grey sky conditions add exposure pairs in g- and r-band, while in grey or bright conditions pairs in i- and z-band are added. A second colour sequence in dark conditions finishes the set. Further pairs in i- and z-band are also observed during astronomical twilight. These twilight observations may be separated by many months from the night-time visits

SkyMapper's Southern Sky Survey : First Data Release (DR1)

The SkyMapper First Data Release provides data from the Shallow Survey across >98% of the southern sky, mostly covering the range from the South Celestial Pole to +2 deg in declination, with some extra coverage reaching +10 deg. Included are fields observed between March 2014 and September 2015, with a number of quality cuts applied. Each visit to a given field includes an exposure in all six filters, uvgriz, although on some fields (12%) not all filter images passed the quality cuts. Measurements from over 2.3 billion detections covering over 20,200 deg2 of sky are available. They correspond to ~300 million unique astrophysical objects from magnitude 8 to 18 (complete to ~17.5 mag, depending on the filter). All magnitudes reported on this site are AB mags