Kathryns Wheel: A spectacular galaxy collision discovered in the Galactic neighbourhood

We report the discovery of the closest collisional ring galaxy to the Milky Way. Such rare systems occur due to "bulls-eye" encounters between two reasonably matched galaxies. The recessional velocity of about 840 km/s is low enough that it was detected in the AAO/UKST Survey for Galactic H$\alpha$ emission. The distance is only 10.0 Mpc and the main galaxy shows a full ring of star forming knots, 6.1 kpc in diameter surrounding a quiescent disk. The smaller assumed "bullet" galaxy also shows vigorous star formation. The spectacular nature of the object had been overlooked because of its location in the Galactic plane and proximity to a bright star and even though it is the 60$^{\rm th}$ brightest galaxy in the HI Parkes All Sky Survey (HIPASS) HI survey. The overall system has a physical size of $\sim$15 kpc, a total mass of $M_\ast = 6.6\times 10^9$ M$_\odot$ (stars + HI), a metallicity of [O/H]$\sim-0.4$, and a star formation rate of 0.2-0.5 M$_\odot$\,yr$^{-1}$, making it a Magellanic-type system. Collisional ring galaxies therefore extend to much lower galaxy masses than commonly assumed. We derive a space density for such systems of $7 \times 10^{-5}\,\rm Mpc^{-3}$, an order of magnitude higher than previously estimated. This suggests Kathryn's Wheel is the nearest such system. We present discovery images, CTIO 4-m telescope narrow-band follow-up images and spectroscopy for selected emission components. Given its proximity and modest extinction along the line of sight, this spectacular system provides an ideal target for future high spatial resolution studies of such systems and for direct detection of its stellar populations.Comment: 18 pages, 12 figures, accepted for publication in MNRA

Common genomic features of Campylobacter jejuni subsp. doylei strains distinguish them from C. jejuni subsp. jejuni

<p>Abstract</p> <p>Background</p> <p><it>Campylobacter jejuni </it>has been divided into two subspecies: <it>C. jejuni </it>subsp. <it>jejuni </it>(<it>Cjj</it>) and <it>C. jejuni </it>subsp. <it>doylei </it>(<it>Cjd</it>). Nearly all of the <it>C. jejuni </it>strains isolated are <it>Cjj</it>; nevertheless, although <it>Cjd </it>strains are isolated infrequently, they differ from <it>Cjj </it>in two key aspects: they are obtained primarily from human clinical samples and are associated often with bacteremia, in addition to gastroenteritis. In this study, we utilized multilocus sequence typing (MLST) and a DNA microarray-based comparative genomic indexing (CGI) approach to examine the genomic diversity and gene content of <it>Cjd </it>strains.</p> <p>Results</p> <p>A geographically diverse collection of eight <it>Cjd </it>strains was examined by MLST and determined to be phylogenetically distinct from <it>Cjj </it>strains. Microarray-based CGI approach also supported this. We were able to demonstrate that <it>Cjd </it>strains exhibited divergence from <it>Cjj </it>strains NCTC 11168 and RM1221 in many of the intraspecies hypervariable regions. Moreover, multiple metabolic, transport and virulence functions (e.g. cytolethal distending toxin) were shown to be absent in the <it>Cjd </it>strains examined.</p> <p>Conclusion</p> <p>Our data demonstrate that <it>Cjd </it>are phylogenetically distinct from <it>Cjj </it>strains. Using the CGI approach, we identified subsets of absent genes from amongst the <it>C. jejuni </it>genes that provide clues as to the potential evolutionary origin and unusual pathogenicity of <it>Cjd</it>.</p

Green's function for gravitational waves in FRW spacetimes

A method for calculating the retarded Green's function for the gravitational wave equation in Friedmann-Roberson-Walker spacetimes, within the formalism of linearized Einstein gravity is developed. Hadamard's general solution to Cauchy's problem for second-order, linear partial differential equations is applied to the FRW gravitational wave equation. The retarded Green's function may be calculated for any FRW spacetime, with curved or flat spatial sections, for which the functional form of the Ricci scalar curvature $R$ is known. The retarded Green's function for gravitational waves propagating through a cosmological fluid composed of both radiation and dust is calculated analytically for the first time. It is also shown that for all FRW spacetimes in which the Ricci scalar curvatures does not vanish, $R \neq 0$, the Green's function violates Huygens' principle; the Green's function has support inside the light-cone due to the scatter of gravitational waves off the background curvature.Comment: 9 pages, FERMILAB-Pub-93/189-

Collapsing granular suspensions

A 2D contact dynamics model is proposed as a microscopic description of a collapsing suspension/soil to capture the essential physical processes underlying the dynamics of generation and collapse of the system. Our physical model is compared with real data obtained from in situ measurements performed with a natural collapsing/suspension soil. We show that the shear strength behavior of our collapsing suspension/soil model is very similar to the behavior of this collapsing suspension soil, for both the unperturbed and the perturbed phases of the material.Comment: 7 pages, 5 figures, accepted for publication in EPJ

Stability of de Sitter spacetime under isotropic perturbations in semiclassical gravity

A spatially flat Robertson-Walker spacetime driven by a cosmological constant is non-conformally coupled to a massless scalar field. The equations of semiclassical gravity are explicitly solved for this case, and a self-consistent de Sitter solution associated with the Bunch-Davies vacuum state is found (the effect of the quantum field is to shift slightly the effective cosmological constant). Furthermore, it is shown that the corrected de Sitter spacetime is stable under spatially-isotropic perturbations of the metric and the quantum state. These results are independent of the free renormalization parameters.Comment: 19 pages, REVTeX

The European Union, borders and conflict transformation: the case of Cyprus

Much of the existing literature on the European Union (EU), conflict transformation and border dynamics has been premised on the assumption that the nature of the border determines EU intervention and the consequences that flow from this in terms of EU impact. The article aims to transcend this literature through assessing how domestic interpretations influence EU border transformation in conflict situations, taking Cyprus as a case study. Moreover, the objective is to fuse the literature on EU bordering impact and perceptions of the EU’s normative projection in conflict resolution. Pursuing this line of inquiry is an attempt to depart from the notion of borders being constructed solely by unidirectional EU logics of engagement or bordering practices to a conceptualization of the border as co-constituted space, where the interpretations of the EU’s normative projections by conflict parties, and the strategies that they pursue, can determine the relative openness of the EU border

Community Engaged Cumulative Risk Assessment of Exposure to Inorganic Well Water Contaminants, Crow Reservation, Montana

An estimated 11 million people in the US have home wells with unsafe levels of hazardous metals and nitrate. The national scope of the health risk from consuming this water has not been assessed as home wells are largely unregulated and data on well water treatment and consumption are lacking. Here, we assessed health risks from consumption of contaminated well water on the Crow Reservation by conducting a community-engaged, cumulative risk assessment. Well water testing, surveys and interviews were used to collect data on contaminant concentrations, water treatment methods, well water consumption, and well and septic system protection and maintenance practices. Additive Hazard Index calculations show that the water in more than 39% of wells is unsafe due to uranium, manganese, nitrate, zinc and/or arsenic. Most families’ financial resources are limited, and 95% of participants do not employ water treatment technologies. Despite widespread high total dissolved solids, poor taste and odor, 80% of families consume their well water. Lack of environmental health literacy about well water safety, pre-existing health conditions and limited environmental enforcement also contribute to vulnerability. Ensuring access to safe drinking water and providing accompanying education are urgent public health priorities for Crow and other rural US families with low environmental health literacy and limited financial resources

Temporal trends (2000–2011) and influences on fishery-independent catch rates for loggerhead sea turtles (Caretta caretta) at an important coastal foraging region in the southeastern United States

Seasonal trawling was conducted randomly in coastal (depths of 4.6–17 m) waters from St. Augustine, Florida, (29.9°N) to Winyah Bay, South Carolina (33.1°N), during 2000–03, 2008–09, and 2011 to assess annual trends in the relative abundance of sea turtles. A total of 1262 loggerhead sea turtles (Caretta caretta) were captured in 23% (951) of 4207 sampling events. Capture rates (overall and among prevalent 5-cm size classes) were analyzed through the use of a generalized linear model with log link function for the 4097 events that had complete observations for all 25 model parameters. Final models explained 6.6% (70.1–75.0 cm minimum straight-line carapace length [SCLmin]) to 14.9% (75.1–80.0 cm SCLmin) of deviance in the data set. Sampling year, geographic subregion, and distance from shore were retained as significant terms in all final models, and these terms collectively accounted for 6.2% of overall model deviance (range: 4.5–11.7% of variance among 5-cm size classes). We retained 18 parameters only in a subset of final models: 4 as exclusively significant terms, 5 as a mixture of significant or nonsignificant terms, and 9 as exclusively nonsignificant terms. Four parameters also were dropped completely from all final models. The generalized linear model proved appropriate for monitoring trends for this data set that was laden with zero values for catches and was compiled for a globally protected species. Because we could not account for much model deviance, metrics other than those examined in our study may better explain catch variability and, once elucidated, their inclusion in the generalized linear model should improve model fits

Interlaboratory study for the evaluation of three microtiter plate-based biofilm quantification methods

Microtiter plate methods are commonly used for biofilm assessment. However, results obtained with these methods have often been difficult to reproduce. Hence, it is important to obtain a better understanding of the repeatability and reproducibility of these methods. An interlaboratory study was performed in five different laboratories to evaluate the reproducibility and responsiveness of three methods to quantify Staphylococcus aureus biofilm formation in 96-well microtiter plates: crystal violet, resazurin, and plate counts. An inter-lab protocol was developed for the study. The protocol was separated into three steps: biofilm growth, biofilm challenge, biofilm assessment. For control experiments participants performed the growth and assessment steps only. For treatment experiments, all three steps were performed and the efficacy of sodium hypochlorite (NaOCl) in killing S. aureus biofilms was evaluated. In control experiments, on the log(10)-scale, the reproducibility SD (S-R) was 0.44 for crystal violet, 0.53 for resazurin, and 0.92 for the plate counts. In the treatment experiments, plate counts had the best responsiveness to different levels of efficacy and also the best reproducibility with respect to responsiveness (Slope/S-R=1.02), making it the more reliable method to use in an antimicrobial efficacy test. This study showed that the microtiter plate is a versatile and easy-to-use biofilm reactor, which exhibits good repeatability and reproducibility for different types of assessment methods, as long as a suitable experimental design and statistical analysis is applied.Peer reviewe

A virtual reality and retailing literature review: Current focus, underlying themes and future directions

This literature review reveals the current research focus, underlying themes and prominent research gaps in the Virtual Reality (VR) literature. 89 journal articles from the 22 years are thematically analysed in order to non-obvious reveal interconnections and themes, including research focus over time and underlying themes by research discipline. Over half of all papers focus on the need to understand the VR shopping consumer, yet no consensus exists as to what the optimal experience is or how to design effective v-Commerce stores. The most prominent research gaps are related to the unique HCI aspects in v-Commerce that influence shopping behaviours. The impact of this review is establishing the current challenges and future directions for academia in order to make v-Commerce a viable reality. Specifically, future research should focus on develop human factor theory in VR shop design (i.e. social dimension, eye-tracking etc.)