The final two redshifts for radio sources from the equatorial BRL sample

Best, Rottgering and Lehnert (1999, 2000a) defined a new sample of powerful radio sources from the Molonglo Reference Catalogue, for which redshifts were compiled or measured for 177 of the 178 objects. For the final object, MRC1059-010 (3C249), the host galaxy is here identified using near-infrared imaging, and the redshift is determined from VLT spectroscopy. For one other object in the sample, MRC0320+053 (4C05.14), the literature redshift has been questioned: new spectroscopic observations of this object are presented, deriving a corrected redshift. With these two results, the spectroscopic completeness of this sample is now 100%. New redshifts are also presented for PKS0742+10 from the Wall & Peacock 2.7 GHz catalogue, and PKS1336+003 from the Parkes Selected Regions. PKS0742+10 shows a strong neutral hydrogen absorption feature in its Lyman-alpha emission profile.Comment: 4 pages. LaTeX. Accepted for publication in MNRA

Conventions spreading in open-ended systems

We introduce a simple open-ended model that describes the emergence of a shared vocabulary. The ordering transition toward consensus is generated only by an agreement mechanism. This interaction defines a finite and small number of states, despite each individual having the ability to invent an unlimited number of new words. The existence of a phase transition is studied by analyzing the convergence times, the cognitive efforts of the agents and the scaling behavior in memory and timeComment: 11 pages, 5 figure

The impact of significant input of fine sediment on benthic fauna at tributary junctions: a case study of the Bermejo-Paraguay River confluence, Argentina

This study examines the morphological features, suspended sediment inputs and hydraulic conditions within a large river in association with ecological patterns before and after a tributary confluence. In order to examine these effects, the macroinvertebrate distributions from three reaches of the Paraguay and Bermejo Rivers (Paraguay-Argentina) are investigated. The Bermejo River is a tributary that supplies significant quantities of fine sediment to the Paraguay River, primarily in suspension. Two reaches were examined on the Paraguay River, upstream and downstream of the Bermejo River junction, with the third study reach located on the Bermejo River, upstream of the confluence with the Paraguay River. The results provide clear evidence that a significantly increased loading of fine sediment at a river confluence has effects on the distribution and potential movement of benthic invertebrates in the lotic environment by representing physical barriers at affected sites. These effects may be important at both local and regional scales, and such increases in suspended sediment (especially associated with anthropogenic change) may thus pose a major threat to ecosystem integrity that has been historically underestimated

Radio galaxy evolution: what you can learn from a Brief Encounter

We describe the pitfalls encountered in deducing from classical double radio source observables (luminosity, spectral index, redshift and linear size) the essential nature of how these objects evolve. We discuss the key role played by hotspots in governing the energy distribution of the lobes they feed, and subsequent spectral evolution. We present images obtained using the new 74 MHz receivers on the VLA and discuss constraints which these enforce on models of the backflow and ages in classical doubles.Comment: invited talk at `Lifecycles of Radio Galaxies' workshop; eds John Biretta et a

Simulation of cloud data security processes and performance

In the world of cloud computing, millions of people are using cloud computing for the purpose of business, education and socialization. Examples of cloud applications are: Google Drive for storage, Facebook for social networks, etc. Cloud users use the cloud computing infrastructure thinking that these services are easy and safe to use. However, there are security and performance issues to be addressed. This paper discusses how cloud users and cloud providers address performance and security issues. In this research, we have used business process modelling and simulation to explore the performance characteristics and security concerns in the service development life cycle. The results show that Business Process Modelling Notations (BPMN) simulation is effective for the study of cloud security process in detail before actual implementation. The total simulation duration time was 51 days and 9 hours 40 minutes but the results are displayed in 7 seconds only

Geodynamics and Rate of Volcanism on Massive Earth-like Planets

We provide estimates of volcanism versus time for planets with Earth-like composition and masses from 0.25 to 25 times Earth, as a step toward predicting atmospheric mass on extrasolar rocky planets. Volcanism requires melting of the silicate mantle. We use a thermal evolution model, calibrated against Earth, in combination with standard melting models, to explore the dependence of convection-driven decompression mantle melting on planet mass. Here we show that (1) volcanism is likely to proceed on massive planets with plate tectonics over the main-sequence lifetime of the parent star; (2) crustal thickness (and melting rate normalized to planet mass) is weakly dependent on planet mass; (3) stagnant lid planets live fast (they have higher rates of melting than their plate tectonic counterparts early in their thermal evolution) but die young (melting shuts down after a few Gyr); (4) plate tectonics may not operate on high mass planets because of the production of buoyant crust which is difficult to subduct; and (5) melting is necessary but insufficient for efficient volcanic degassing - volatiles partition into the earliest, deepest melts, which may be denser than the residue and sink to the base of the mantle on young, massive planets. Magma must also crystallize at or near the surface, and the pressure of overlying volatiles must be fairly low, if volatiles are to reach the surface. If volcanism is detected in the Tau Ceti system, and tidal forcing can be shown to be weak, this would be evidence for plate tectonics.Comment: Revised version, accepted by Astrophysical Journa

Estimates of unresolved point sources contribution to WMAP 5

We present an alternative estimate of the unresolved point source contribution to the WMAP temperature power spectrum based on current knowledge of sources from radio surveys in the 1.4-90 GHz range. We implement a stochastic extrapolation of radio point sources in the NRAO-VLA Sky Survey (NVSS) catalog, from the original 1.4 GHz to the ~ 100 GHz frequency range relevant for CMB experiments. With a bootstrap approach, we generate an ensemble of realizations that provides the probability distribution for the flux of each NVSS source at the final frequency. The predicted source counts agree with WMAP results for S > 1 Jy and the corresponding sky maps correlate with WMAP observed maps in Q-, V- and W- bands, for sources with flux S > 0.2 Jy. The low-frequency radio surveys found a steeper frequency dependence for sources just below the WMAP nominal threshold than the one estimated by the WMAP team. This feature is present in our simulations and translates into a shift of 0.3-0.4 \sigma in the estimated value of the tilt of the power spectrum of scalar perturbation, n_s, as well as \omega_c. This approach demonstrates the use of external point sources datasets for CMB data analysis.Comment: 12 pages, 8 figures, to be published on MNRA

The optical spectra of X-shaped radio galaxies

X-shaped radio galaxies are defined by their peculiar large-scale radio morphology. In addition to the classical double-lobed structure they have a pair of low-luminosity wings that straddles the nucleus at almost right angles to the active lobes, thus giving the impression of an 'X'. In this paper we study for the first time the optical spectral properties of this object class using a large sample (~50 sources). We find that the X-shaped radio population is composed roughly equally of sources with weak and strong emission line spectra, which makes them, in combination with the well-known fact that they preferentially have radio powers intermediate between those of Fanaroff-Riley type I (FR I) and type II (FR II) radio galaxies, the archetypal transition population. We do not find evidence in support of the proposition that the X-shape is the result of a recent merger: X-shaped radio sources do not have unusually broad emission lines, their nuclear environments are in general not dusty, and their host galaxies do not show signs of enhanced star formation. Instead, we observe that the nuclear regions of X-shaped radio sources have relatively high temperatures. This finding favours models, which propose that the X-shape is the result of an overpressured environment.Comment: 12 pages, 8 figures, accepted by MNRA

Celebrity advocacy and public engagement: the divergent uses of celebrity

This article sounds a cautionary note about the instrumental use of celebrity advocacy to (re)engage audiences in public life. It begins by setting out the steps necessary to achieve public recognition of a social problem requiring a response. It then presents empirical evidence which suggests that those most interested in celebrity, while also paying attention to the main stories of the day, are also least likely to participate in any form of politics. However, this does not rule out the possibility of forging a link between celebrity and public engagement, raising questions about what would potentially sustain such an articulation. After discussing the broader cultural context of celebrity advocacy in which perceived authenticity functions valorised form of symbolic capital, the article outlines a phenomenological approach to understanding the uses audiences make of celebrity advocacy, using the example of a Ewan McGregor UNICEF appeal for illustration. It concludes that while media encounters with celebrities can underpin a viewer’s sense of self, this is as likely to lead to the rationalisation of inaction as a positive response to a charity appeal