The Resolved Outer Population of NGC6822 with WFPC2

We present F336W (U), F439W (B), F555W (V), and F675W (R) Wide Field Planetary Camera 2 (WFPC2) photometry of two outer regions of the Local Group dwarf irregular galaxy NGC6822. The NE region is ~13 arcmin from the galaxy centre, while the W region lies 10 arcmin out, and within the wispy low surface brightness outer regions of the galaxy. The fields are not crowded and contain few NGC 6822 stars. We discuss errors and uncertainties and find that the W region contains a main sequence that extends to stars of about 2 solar masses, with an age of about 200 Myr. The NE region has no main sequence or stars younger than 1 Gyr, but does contain some luminous red stars that are not matched in the W field. These stars are not clumped in the field. The results suggest that the W region may be a trace of a tidal event that triggered the current star-formation in this isolated galaxy.Comment: 12 pages including 2 tables, plus 4 figures (#1 omitted) To appear in PAS

Rapid flow cytometric measurement of protein inclusions and nuclear trafficking.

Proteinaceous cytoplasmic inclusions are an indicator of dysfunction in normal cellular proteostasis and a hallmark of many neurodegenerative diseases. We describe a simple and rapid new flow cytometry-based method to enumerate, characterise and, if desired, physically recover protein inclusions from cells. This technique can analyse and resolve a broad variety of inclusions differing in both size and protein composition, making it applicable to essentially any model of intracellular protein aggregation. The method also allows rapid quantification of the nuclear trafficking of fluorescently labelled molecules

Variable stars in the dwarf irregular galaxy NGC 6822: the photometric catalogue

Deep B,V time-series photometry obtained with the ESO Very Large Telescope has been used to identify variable stars in the dwarf irregular galaxy NGC 6822. We surveyed a 6.8x6.8 arcmin area of the galaxy and detected a total number of 390 candidate variables with the optimal image subtraction technique (Alard 2000). Light curves on a magnitude scale were obtained for 262 of these variables. Differential flux light curves are available for the remaining sample. In this paper we present the photometric catalogue of calibrated light curves and time-series data, along with coordinates and classification of the candidate variables. A detailed description is provided of the procedures used to identify the variable stars and calibrate their differential flux light curves on a magnitude scale.Comment: 22 pages, 19 figures only as JPEG. Revised version with corrected eq. 5. Full text with better resolution .ps figures available upon request from the authors. Uses aa.cls (included), in press on A&A. Table 2 will only be published at the CDS, Appendix A, Tables 4,5,6 will only be available in the electronic edition of the Journa

The trajectory taken by dimeric Cu/Zn superoxide dismutase through the protein unfolding and dissociation landscape is modulated by salt-bridge formation

Native mass spectrometry (MS) is a powerful means for studying macromolecular protein assemblies, including accessing activated states. However, much remains to be understood about what governs which regions of the protein (un)folding funnel are explored by activation of protein ions in vacuum. Here we examine the trajectory that Cu/Zn superoxide dismutase (SOD1) dimers take over the unfolding and dissociation free energy landscape in vacuum. We examined wild-type SOD1 and six disease-related point-mutants by using tandem MS and ion-mobility MS as a function of collisional activation. For six of the seven SOD1 variants, increasing activation prompted dimers to transition through two unfolding events and dissociate symmetrically into monomers with (as near as possible) equal charges. The exception was G37R, which proceeded only through the first unfolding transition, and displayed a much higher abundance of asymmetric products. Supported by the observation that ejected asymmetric G37R monomers were more compact than symmetric G37R ones, we localised this effect to the formation of a gas-phase salt-bridge in the first activated conformation. To examine the data quantitatively, we applied Arrhenius-type analysis to estimate the barriers on the corresponding free energy landscape. This reveals a heightening of the barrier to unfolding in G37R >5 kJmol-1 over the other variants, consistent with expectations for the strength of a salt-bridge. Our work demonstrates weaknesses in the simple general framework for understanding protein complex dissociation in vacuum, and highlights the importance of individual residues, their local environment, and specific interactions in governing product formation

Flow cytometric measurement of the cellular propagation of TDP-43 aggregation

Amyotrophic lateral sclerosis is a devastating neuromuscular degenerative disease characterized by a focal onset of motor neuron loss, followed by contiguous outward spreading of pathology including TAR DNA-binding protein of 43 kDa (TDP-43) aggregates. Previous work suggests that TDP-43 can move between cells. Here we used a novel flow cytometry technique (FloIT) to analyze TDP-43 inclusions and propagation. When cells were transfected to express either mutant G294A TDP-43 fused to GFP or wild type TDP-43fused to tomato red and then co-cultured, flow cytometry detected intact cells containing both fusion proteins and using FloIT detected an increase in the numbers of inclusions in lysates from cells expressing wild type TDP-43-tomato. Furthermore, in this same model, FloIT analyses detected inclusions containing both fusion proteins. These results imply the transfer of TDP-43 fusion proteins between cells and that this process can increase aggregation of wild-type TDP-43 by a mechanism involving co-aggregation with G294A TDP-43.This work was supported by the NHMRC under Grant 1084144 and 1095215

Connecting the cosmic infrared background to the X-ray background

We estimate the contribution of AGNs and of their host galaxies to the infrared background. We use the luminosity function and evolution of AGNs recently determined by the hard X-ray surveys, and new Spectral Energy Distributions connecting the X-ray and the infrared emission, divided in intervals of absorption. These two ingredients allow us to determine the contribution of AGNs to the infrared background by using mostly observed quantities, with only minor assumptions. We obtain that AGN emission contributes little to the infrared background ($<$5% over most of the infrared bands), implying that the latter is dominated by star formation. However, AGN host galaxies may contribute significantly to the infrared background, and more specifically 10--20% in the 1--20$\mu$m range and $\sim$5% at $\lambda<60\mu m$. We also give the contribution of AGNs and of their host galaxies to the source number counts in various infrared bands, focusing on those which will be observed with Spitzer. We also report a significant discrepancy between the expected contribution of AGN hosts to the submm background and bright submm number counts with the observational constraints. We discuss the causes and implications of this discrepancy and the possible effects on the Spitzer far-IR bands.Comment: to appear in MNRAS, replaced with accepted version, paper shortened, results unchange

Young and Intermediate-age Distance Indicators

Distance measurements beyond geometrical and semi-geometrical methods, rely mainly on standard candles. As the name suggests, these objects have known luminosities by virtue of their intrinsic proprieties and play a major role in our understanding of modern cosmology. The main caveats associated with standard candles are their absolute calibration, contamination of the sample from other sources and systematic uncertainties. The absolute calibration mainly depends on their chemical composition and age. To understand the impact of these effects on the distance scale, it is essential to develop methods based on different sample of standard candles. Here we review the fundamental properties of young and intermediate-age distance indicators such as Cepheids, Mira variables and Red Clump stars and the recent developments in their application as distance indicators.Comment: Review article, 63 pages (28 figures), Accepted for publication in Space Science Reviews (Chapter 3 of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age

Nest-building males trade-off material collection costs with territory value

This work was supported by the BBSRC (BB/I019502/1 to SDH and SLM) and Roslin Institute Strategic Grant funding from the BBSRC (SLM).Building a structurally robust nest is crucial for reproductive success in many birds. However, we know little about the criteria birds use to select material or where they go to collect it. Here we observed the material collection of male Cape Weavers (Ploceus capensis). Males typically selected long, strong material to build their nests and each male collected material from different locations. Males that built more nests nested in a different area of the colony and flew further to collect nest material than did males that built fewer nests. As these males that flew further to collect material had longer tails and wings and attracted more females to their territories than did males that flew shorter distances, they may have traded off the travel costs of collecting nest materials with benefits gained from holding a territory in a more 'desirable' part of the colony. Nest construction, then, appears to be a multi-dimensional task whereby birds take into account material's structural properties, material proximity to the nest site and territory quality. Males that do this effectively both attract more mates and provide structurally sound nests for their young.Publisher PDFPeer reviewe

Challenging the holy grail of hospital accreditation: A cross sectional study of inpatient satisfaction in the field of cardiology

Extent: 7p.Background: Subjective parameters such as quality of life or patient satisfaction gain importance as outcome parameters and benchmarks in health care. In many countries hospitals are now undergoing accreditation as mandatory or voluntary measures. It is believed but unproven that accreditations positively influence quality of care and patient satisfaction. The present study aims to assess in a defined specialty (cardiology) the relationship between patient satisfaction (as measured by the recommendation rate) and accreditation status. Methods: Consecutive patients discharged from 25 cardiology units received a validated patient satisfaction questionnaire. Data from 3,037 patients (response rate > 55%) became available for analysis. Recommendation rate was used as primary endpoint. Different control variables such as staffing level were considered. Results: The 15 accredited units did not differ significantly from the 10 non-accredited units regarding main hospital (i.e. staffing levels, no. of beds) and patient (age, gender) characteristics. The primary endpoint "recommendation rate of a given hospital" for accredited hospitals (65.6%, 95% Confidence Interval (CI) 63.4 - 67.8%) and hospitals without accreditation (65.8%, 95% CI 63.1 - 68.5%) was not significantly different. Conclusion: Our results support the notion that - at least in the field of cardiology - successful accreditation is not linked with measurable better quality of care as perceived by the patient and reflected by the recommendation rate of a given institution. Hospital accreditation may represent a step towards quality management, but does not seem to improve overall patient satisfaction.Cornelia Sack, Peter Lütkes, Wolfram Günther, Raimund Erbel, Karl-Heinz Jöckel and Gerald J Holtman

Binarity and multiperiodicity in high-amplitude delta Scuti stars

We have carried out a photometric and spectroscopic survey of bright high-amplitude delta Scuti (HADS) stars. The aim was to detect binarity and multiperiodicity (or both) in order to explore the possibility of combining binary star astrophysics with stellar oscillations. Here we present the first results for ten, predominantly southern, HADS variables. We detected the orbital motion of RS Gru with a semi-amplitude of ~6.5 km/s and 11.5 days period. The companion is inferred to be a low-mass dwarf star in a close orbit around RS Gru. We found multiperiodicity in RY Lep both from photometric and radial velocity data and detected orbital motion in the radial velocities with hints of a possible period of 500--700 days. The data also revealed that the amplitude of the secondary frequency is variable on the time-scale of a few years, whereas the dominant mode is stable. Radial velocities of AD CMi revealed cycle-to-cycle variations which might be due to non-radial pulsations. We confirmed the multiperiodic nature of BQ Ind, while we obtained the first radial velocity curves of ZZ Mic and BE Lyn. The radial velocity curve and the O-C diagram of CY Aqr are consistent with the long-period binary hypothesis. We took new time series photometry on XX Cyg, DY Her and DY Peg, with which we updated their O-C diagrams.Comment: 15 pages, 16 pages, accepted for publication in MNRA