Lateral Expansion of the Bridges of Cygnus A and other Powerful Radio Sources

Measurements of the width of the radio bridge at several locations along the bridge for each of four powerful extended radio sources are presented. Adopting a few simple assumptions, these measurements may be used to predict the radio surface brightness as a function of position across the radio bridge. The predicted and observed surface brightnesses across the bridges are compared and found to agree fairly well. The results are consistent with a simple picture in which the radio power and size of the radio lobe at the forward edge of the radio bridge are roughly time-independent for a given source, and the expansion of the bridge in the lateral direction is adiabatic. There is no indication that reacceleration or energy transport is important in the bridges of these sources. The rate of lateral expansion of the bridge just behind the radio lobe and hotspot in terms of the rate of forward propagation is compared with that predicted, and found to be in good agreement with the predicted value.Comment: 7 pages, uuencoded compressed postscript. To appear in the Proceding of the Cygnus A workshop, May 1-4, Green Bank, W

The use of radio observations to probe ambient gas densities

The radio properties of powerful extended radio sources may be used to estimate the ambient gas density in the vicinity of radio lobes. A sample of 27 radio lobes from 14 radio galaxies and of 14 radio lobes from 8 radio loud quasars was constructed using sources from the published literature with sufficient radio information to allow an estimate of the ambient gas density. The ambient gas density as a function of separation of the lobe from the center of the parent galaxy indicates a composite density profile, where Cygnus A plays the key role of determining the normalization for the ambient gas density. The composite density profile of the galaxies and quasars studied here is similar to the density profile of gas in low-redshift clusters of galaxies, which confirms the result obtained by Daly [1] using a somewhat smaller sample of radio sources. The data presented here allow an estimate of the core gas density, core radius, and slope of the density profile assuming that the gas density can be fit by a King model. The data suggest that the core gas density decreases as the redshift of the source increases, and is consistent with either a roughly constant core radius, or a core radius that increases with increasing source redshift. Thus, our results are completely consistent with observations indicating negative evolution of the cluster X-ray luminosity function. (truncated to <24 lines

Science, Policy and Partnerships

Successful recovery of the Salish Sea requires collaboration between scientists (both biophysical and social) and policy/decision makers. Without this relationship we find ourselves with scientific research that is not relevant to decision making and decisions made without a strong scientific foundation, and without the support of the science community. While there is a great deal of good scientific work currently available to enhance ecosystem recovery decision-making, many of the questions that decision makers currently face require further investigation to address critical uncertainties, or at minimum, collection of data through environmental monitoring or social surveys to fill important gaps. However, it is critical that science does not impede early ecosystem-scale recovery actions; we do have sufficient knowledge to take action. In this panel session we will discuss the relationships between science and policy communities in ecosystem recovery efforts in the Salish Sea, including the science foundation for early action and the science and policy knowledge gaps for recovery at the scale of the Salish Sea. Panel members will include both US and Canadian professionals involved in the science and policy of ecosystem-based management for the Salish Sea. Panelists will consider and discuss such topics as:• An overview of Salish Sea status and trends and what they are really telling us and how should the status and trends influence policy and science• Examples of successes and challenges in science/policy collaboration. • Social constructs and behaviors needed for successful ecosystem recovery• Identified opportunities, specific approaches, and current challenges for science to more effectively inform policy decision-making. Panelists:Katharine Wellman –Moderator, Vice Chair Puget Sound Partnership Science Panel John Stein, Chair Puget Sound Partnership Science Panel Joel Baker, Puget Sound Institute, University of Washington Angela Bonifaci, US Environmental Protection Agency Tracy Collier, Puget Sound Partnership Thomas Leschine, School of Marine and Environmental Affairs, University of WashingtonIan Perry, Department of Fish and Oceans, Canada Terre Satterfield, University of British Columbi

An introduction to spacecraft thermal control

External and internal passive and active methods for spacecraft thermal control - material insulation and structural propertie

Cottage By The Lake : Aggie Lane

https://digitalcommons.library.umaine.edu/mmb-vp/1245/thumbnail.jp

Structural changes of thermal sprayed graphene nano platelets film into amorphous carbon under sliding wear

© 2020 The Authors Graphene has become a promising candidate to protect surfaces against friction due to its strength and lubricating ability. In this study, graphene nano platelets (GNP) thin films have been deposited onto stainless steel substrates by axially injecting GNP suspension through high velocity oxy fuel thermal spray gun. The tribological performance of the films under dry sliding wear was investigated through unlubricated ball on disc sliding wear test against a sintered alumina counter body ball under 5 N load. The understanding of the behaviour of the GNPs under sliding wear will be useful for improving the performance of graphene-based coatings which are in demand for wear resistant applications. A film was deposited showing significant improvements in friction with coefficient of friction value reduced by 7 times compared to uncoated stainless steel, even for a discontinuous film. A morphological analysis shows sliding wear led to change in particle shape from angular flakes into randomly oriented circles. Interatomic bonding and structural analysis performed reveals oxidation defect formations during wear test. Structural degradation and oxidation of GNPs during the process led to formation of amorphous carbon from graphene. Amorphous carbon formation reduces the lubricating ability and strength of the film, leading to failure

Does \u2018bigger\u2019mean \u2018better\u2019? Pitfalls and shortcuts associated with big data for social research

\u2018Big data is here to stay.\u2019 This key statement has a double value: is an assumption as well as the reason why a theoretical reflection is needed. Furthermore, Big data is something that is gaining visibility and success in social sciences even, overcoming the division between humanities and computer sciences. In this contribution some considerations on the presence and the certain persistence of Big data as a socio-technical assemblage will be outlined. Therefore, the intriguing opportunities for social research linked to such interaction between practices and technological development will be developed. However, despite a promissory rhetoric, fostered by several scholars since the birth of Big data as a labelled concept, some risks are just around the corner. The claims for the methodological power of bigger and bigger datasets, as well as increasing speed in analysis and data collection, are creating a real hype in social research. Peculiar attention is needed in order to avoid some pitfalls. These risks will be analysed for what concerns the validity of the research results \u2018obtained through Big data. After a pars distruens, this contribution will conclude with a pars construens; assuming the previous critiques, a mixed methods research design approach will be described as a general proposal with the objective of stimulating a debate on the integration of Big data in complex research projecting