Loki, Io: New groundbased observations and a model describing the change from periodic overturn

Loki Patera is the most powerful volcano in the solar system. We have obtained measurements of Loki's 3.5 micron brightness from NASA's Infrared Telescope Facility (IRTF) and have witnessed a change from the periodic behavior previously noted. While Loki brightened by a factor of several every 540 days prior to 2001, from 2001 through 2004 Loki remained at a constant, medium brightness. We have constructed a quantitative model of Loki as a basaltic lava lake whose solidified crust overturns when it becomes buoyantly unstable. By altering the speed at which the overturn propagates across the patera, we can match our groundbased brightness data. In addition, we can match other data taken at other times and wavelengths. By slowing the propagation speed dramatically, we can match the observations from 2001-2004. This slowing may be due to a small change in volatile content in the magma

Spectrum, Winter 1992

Spectrum was a newsletter for students, faculty, staff and alumni of the Henry M. Goldman School of Dental Medicine, published from 1983-1992

The SDVs Are Coming! An Examination of Minnesota Laws in Preparation for Self-Driving Vehicles

Self-driving vehicles (SDVs) are predicted to be the future of automotive transportation. The significant potential benefits of SDVs to safety, congestion reduction, land use, and productivity are hard to ignore. Although fully automated vehicles are still a ways away, the technology is rapidly advancing and becoming more legally accepted. For example, the National Highway Traffic Safety Administration (NHTSA) requires all newly manufactured cars to have at least a low-level of autonomous vehicle technology and suggests widespread adoption of more advanced technology by 2020. Four states and the District of Columbia have some form of legislation expressly allowing SDVs or the testing of such vehicles within state boundaries. In fact, two states—California and Nevada—have even issued comprehensive regulations for both private use and testing of SDVs. Several companies, most notably Google, are aggressively pursuing the technology and advocating for legal changes in support of SDVs. But what does this all mean for Minnesota drivers, laws and lawmakers, and local economies? This Article explores the development of SDVs and related technology and how states have responded to this development as context for more substantive discussion about why and how Minnesota might move to adopt and adapt to this transformative technology. Specifically, this Article will explore how current laws may already permit SDVs and how the law could be, or in some cases must be, modified to authorize testing and use of SDVs in the state. Finally, this Article will describe why SDVs and the related legal changes needed to support their development and adoption can greatly benefit Minnesota’s citizens and economy

CSSs in a sample of B2 radio sources of intermediate strength

We present radio observations of 19 candidate compact steep-spectrum (CSS) objects selected from a well-defined, complete sample of 52 B2 radio sources of intermediate strength. These observations were made with the VLA A-array at 4.835 GHz. The radio structures of the entire sample are summarised and the brightness asymmetries within the compact sources are compared with those of the more extended ones, as well as with those in the 3CRR sample and the CSSs from the B3-VLA sample. About 25 per cent of the CSS sources exhibit large brightness asymmetries, with a flux density ratio for the opposing lobes of $>$5, possibly due to interaction of the jets with infalling material. The corresponding percentage for the larger-sized objects is only about 5 per cent. We also investigate possible dependence of the flux density asymmetry of the lobes on redshift, since this might be affected by more interactions and mergers in the past. No such dependence is found. A few individual objects of interest are discussed in the paper.Comment: 10 pages, 7 figures, 2 tables; accepted for publication in Astronomy and Astrophysic

The Presence and Distribution of HI Absorbing Gas in Sub-galactic Sized Radio Sources

We consider the incidence of HI absorption in intrinsically small sub-galactic sized extragalactic sources selected from sources classified as Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources. We find that the smaller sources (<0.5 kpc) have larger HI column densities than the larger sources (>0.5 kpc). Both a spherical and an axi-symmetric gas distribution, with a radial power law density profile, can be used to explain this anti-correlation between projected linear size and HI column density. Since most detections occur in objects classified as galaxies, we argue that if the unified schemes apply to GPS/CSSs a disk distribution for the HI is more likely. The most favoured explanation for the compact sizes of the GPS/CSSs is that they are young sources evolving in a power law density medium. For the GPSs with measured expansion velocities, our derived densities are within an order of magnitude of those estimated from ram-pressure confinement of the lobes assuming equipartition. Our results therefore support the youth model.Comment: 12 pages, 8 figures, accepted for publication in A&

A 120-year record of resilience to environmental change in brachiopods.

The inability of organisms to cope in changing environments poses a major threat to their survival. Rising carbon dioxide concentrations, recently exceeding 400 μatm, are rapidly warming and acidifying our oceans. Current understanding of organism responses to this environmental phenomenon is based mainly on relatively short- to medium-term laboratory and field experiments, which cannot evaluate the potential for long-term acclimation and adaptation, the processes identified as most important to confer resistance. Here, we present data from a novel approach that assesses responses over a centennial timescale showing remarkable resilience to change in a species predicted to be vulnerable. Utilising museum collections allows the assessment of how organisms have coped with past environmental change. It also provides a historical reference for future climate change responses. We evaluated a unique specimen collection of a single species of brachiopod (Calloria inconspicua) collected every decade from 1900 to 2014 from one sampling site. The majority of brachiopod shell characteristics remained unchanged over the past century. One response, however, appears to reinforce their shell by constructing narrower punctae (shell perforations) and laying down more shell. This study indicates one of the most calcium-carbonate-dependent species globally to be highly resilient to environmental change over the last 120 years and provides a new insight for how similar species might react and possibly adapt to future change

State, community and the negotiated construction of energy markets: Community energy policy in England

This article provides fresh insight on the political construction of markets through empirical analysis of community energy in the UK. It considers the diverse actors, understandings, processes and technologies enrolled in market creation, stabilisation and correction, while emphasising how negotiation, mediation and translation are pervasive throughout. Our starting point is an exploration of the role of the state in managing processes of socially embedding and disembedding markets, and how tensions between ideological commitments to deregulation and the social necessity of intervention are addressed by governing at a distance, in this example through the conveniently malleable notion of ‘community’. We draw attention in particular to the variegated manifestations of these processes and the plurality of actors and logics operating within the ‘black box’ of the state, as well as within and between markets and civil society. We reveal how negotiation between competing logics – the impulse to marketise and its diverse others – can be observed across different forms of organisation and action. We argue that such deliberations can be seen as fractal patterns throughout contemporary socioeconomic arrangements, emphasising how the Polanyian concept of the ‘double movement’ can be deepened through analysis of the heterogeneous associations and logics at work in ‘actually existing’ instituted action, understanding political processes as ontologically performative. Empirical material is drawn from across four research projects, each focusing on different aspects of the UK government's Community Energy Strategy, exploring the varying ways marketisation plays out through different governmental programmes

Samples and statistics of CSS and GPS sources

Several samples have been proposed in the last years in order to study the properties of intrinsically small sources. In this paper, we review the properties of the main samples that are currently available, both selected on the basis of spectral index and of morphology. As a result of the work in this area, large numbers of intrinsically small sources have been found. We summarize the present status of hot spot advance measurements, listing 18 sources with available VLBI data. The mean hot spot separation velocity is v_{sep} = (0.19 +/- 0.11)h^{-1}c and the kinematic ages span the range from 20 to 3000 years. Finally, we present a brief outlook on the use of future instrumentation in order to improve our understanding of radio source evolution. Prospects for VSOP2, e-VLA, e-MERLIN, LOFAR, ALMA, and Fermi are suggested.Comment: 6 pages, invited talk at "The Fourth Workshop on Compact Steep Spectrum and GHz-Peaked Spectrum Radio Sources

Radio properties of Compact Steep Spectrum and GHz-Peaked Spectrum radio sources

Compact steep spectrum (CSS) and GHz-peaked spectrum (GPS) radio sources represent a large fraction of the extragalactic objects in flux density-limited samples. They are compact, powerful radio sources whose synchrotron peak frequency ranges between a few hundred MHz to several GHz. CSS and GPS radio sources are currently interpreted as objects in which the radio emission is in an early evolutionary stage. In this contribution I review the radio properties and the physical characteristics of this class of radio sources, and the interplay between their radio emission and the ambient medium of the host galaxy.Comment: 9 pages, 4 figures. Accepted for publication in Astronomische Nachrichten. Review presented at the 5th Workshop on CSS and GPS radio sources, held in Rimini (Italy) in May 201