Gas network development in a precompacted bentonite experiment: evidence of generation and evolution

In a deep geological disposal facility for radioactive waste, precompacted bentonite is proposed as a sealing material for the isolation of boreholes, disposal galleries and deposition holes. The advective movement of repository gas in bentonite has been linked to the development of new porosity and propagation of dilatant pathways. For the first time we present a detailed analysis of stress field data during the generation and evolution of a gas network. A new experimental dataset, from a highly instrumented test, clearly shows the strong coupling between stress, gas pressure and flow in bentonite. Multiple discrete propagation events are observed, demonstrating spatial variability and time-dependency as permeability within the clay develops. Analysis of the stress data before, during and after gas entry indicates a heterogeneous stress field initially develops, resulting from the development of these pathways. The flow network is dynamic and continues to spatially evolve after gas entry, such that permeability under these conditions must be time-dependent in nature. Perturbation of the stress field is significant before all major gas outflow events, presumably resulting from the requirement to propagate an effective gas network before outflow is possible. In contrast, no major flow perturbations are detected which did not correlate with fluctuations in the stress field. The controls on the distribution and geometry of the resulting flow network are unclear, as well as its long-term evolution and stability. These will be beneficial in the assessment of gas pressure evolution as part of safety case development

Realizing a Deterministic Source of Multipartite-Entangled Photonic Qubits

Sources of entangled electromagnetic radiation are a cornerstone in quantum information processing and offer unique opportunities for the study of quantum many-body physics in a controlled experimental setting. While multi-mode entangled states of radiation have been generated in various platforms, all previous experiments are either probabilistic or restricted to generate specific types of states with a moderate entanglement length. Here, we demonstrate the fully deterministic generation of purely photonic entangled states such as the cluster, GHZ, and W state by sequentially emitting microwave photons from a controlled auxiliary system into a waveguide. We tomographically reconstruct the entire quantum many-body state for up to $N=4$ photonic modes and infer the quantum state for even larger $N$ from process tomography. We estimate that localizable entanglement persists over a distance of approximately ten photonic qubits, outperforming any previous deterministic scheme

The NOAO Data Lab virtual storage system

Collaborative research/computing environments are essential for working with the next generations of large astronomical data sets. A key component of them is a distributed storage system to enable data hosting, sharing, and publication. VOSpace is a lightweight interface providing network access to arbitrary backend storage solutions and endorsed by the International Virtual Observatory Alliance (IVOA). Although similar APIs exist, such as Amazon S3, WebDav, and Dropbox, VOSpace is designed to be protocol agnostic, focusing on data control operations, and supports asynchronous and third-party data transfers, thereby minimizing unnecessary data transfers. It also allows arbitrary computations to be triggered as a result of a transfer operation: for example, a file can be automatically ingested into a database when put into an active directory or a data reduction task, such as Sextractor, can be run on it. In this paper, we shall describe the VOSpace implementations that we have developed for the NOAO Data Lab. These offer both dedicated remote storage, accessible as a local file system via FUSE, and a local VOSpace service to easily enable data synchronization

The NOAO Data Lab: Science-Driven Development

The NOAO Data Lab aims to provide infrastructure to maximize community use of the high-value survey datasets now being collected with NOAO telescopes and instruments. As a science exploration framework, the Data Lab allow users to access and search databases containing large (i.e. terabyte-scale) catalogs, visualize, analyze, and store the results of these searches, combine search results with data from other archives or facilities, and share these results with collaborators using a shared workspace and/or data publication service. In the process of implementing the needed tools and services, specific science cases are used to guide development of the system framework and tools. The result is a Year-1 capability demonstration that (fully or partially) implements each of the major architecture components in the context of a real-world science use-case. In this paper, we discuss how this model of science-driven development helped us to build a fully functional system capable of executing the chosen science case, and how we plan to scale this system to support general use in the next phase of the project

ICTs and ethical consumption: the political and market futures of fair trade

This paper addresses the relationship between information and communication technologies (ICTs) and ethical consumption as part of a cause for the insurance of a sustainable future. It homes in on fair trade as an ethical market, politically progressive cause and, crucially, form of participation where citizens can engage in the formation of an alternative future and the broader issue of food security. An three-dimensional analysis of agencies and uses of digital structures and content is informed by a case study approach, as well as interviews with fair trade activists, and ethically consuming citizens in the British metropolis. Through this, the argument which primarily rises distinguishes between the dimensions of durability (in terms of time and duration) and sustainability (in terms of time, duration and environmental concerns) of engagement in fair trade as a form of participation. Ethical consumption, then, is part of a durable market which has developed despite general market fluctuation, but is still very much bound in traditional physical economic spaces; in other words, ethical consumption has been integrated in the business as usual paradigm. Additionally, ICTs have not challenged the way in which information about ethical consumption is communicated or the spaces in which it is conducted. ICTs have been employed by fair trade activists, but they have not contributed to the development of fair trade as a political or economic project. Over a period of over five decades since the inception of the cause, their use has not significantly altered the way in which citizens engage with fair trade in the alternative or mainstream marketplace

Software-sorted geographies.

This paper explores the central role of computerized code in shaping the social and geographical politics of inequality in advanced societies. The central argument is that, while such processes are necessarily multifaceted, multiscaled, complex and ambivalent, a great variety of ‘software-sorting’ techniques is now being widely applied in efforts to try to separate privileged and marginalized groups and places across a wide range of sectors and domains. This paper’s central demonstration is that the overwhelming bulk of software-sorting applications is closely associated with broader transformations from Keynesian to neoliberal service regimes. To illustrate such processes of software-sorting, the paper analyses recent research addressing three examples of software-sorting in practice. These address physical and electronic mobility systems, online geographical information systems (GIS), and face-recognition closed circuit television (CCTV) systems covering city streets. The paper finishes by identifying theoretical, research and policy implications of the diffusion of software-sorted geographies within which computerized code continually orchestrates inequalities through technological systems embedded within urban environments

Hubble Space Telescope survey of the Perseus Cluster -IV: Compact stellar systems in the Perseus Cluster core and Ultra Compact Dwarf formation in star forming filaments

We present the results of the first search for Ultra Compact Dwarfs (UCDs) in the Perseus Cluster core, including the region of the cluster around the unusual Brightest Cluster Galaxy (BCG) NGC 1275. Utilising Hubble Space Telescope Advanced Camera for Surveys imaging, we identify a sample of 84 UCD candidates with half-light radii 10 pc < r_e < 57 pc out to a distance of 250 kpc from the cluster centre, covering a total survey area of ~70 armin^2. All UCDs in Perseus lie in the same size-luminosity locus seen for confirmed UCDs in other regions of the local Universe. The majority of UCDs are brighter than M_R = -10.5, and lie on an extrapolation of the red sequence followed by the Perseus Cluster dwarf elliptical population to fainter magnitudes. However, three UCD candidates in the vicinity of NGC 1275 are very blue, with colours (B-R)_0 < 0.6 implying a cessation of star formation within the past 100 Myr. Furthermore, large blue star clusters embedded in the star forming filaments are highly indicative that both proto-globular clusters (GCs) and proto-UCDs are actively forming at the present day in Perseus. We therefore suggest star forming filaments as a formation site for some UCDs, with searches necessary in other low redshift analogues of NGC 1275 necessary to test this hypothesis. We also suggest that tidal disruption of dwarf galaxies is another formation channel for UCD formation in the core of Perseus as tidal disruption is ongoing in this region as evidenced by shells around NGC 1275. Finally, UCDs may simply be massive GCs based on strong similarities in the colour trends of the two populations.Comment: 18 pages, 20 figures, 3 tables. Accepted for publication in MNRA

Geochemical analysis of bulk marine sediment by Inductively Coupled Plasma–Atomic Emission Spectroscopy on board the JOIDES Resolution

Geochemical analyses on board the JOIDES Resolution have been enhanced with the addition of a Jobin-Yvon Ultrace inductively coupled plasma-atomic emission spectrometer (ICP-AES) as an upgrade from the previous X-ray fluorescence facility. During Leg 199, we sought to both challenge and utilize the capabilities of the ICP-AES in order to provide an extensive bulk-sediment geochemical database during the cruise. These near real-time analyses were then used to help characterize the recovered sedimentary sequences, calculate mass accumulation rates of the different sedimentary components, and assist with cruise and postcruise sampling requests. The general procedures, sample preparation techniques, and basic protocol for ICP-AES analyses on board ship are outlined by Murray et al. (2000) in Ocean Drilling Program Tech Note, 29. We expand on those concepts and offer suggestions for ICP-AES methodology, calibration by standard reference materials, data reduction procedures, and challenges that are specific to the analysis of bulk-sediment samples. During Leg 199, we employed an extensive bulk-sediment analytical program of ~600 samples of varying lithologies, thereby providing several opportunities for refinement of techniques. We also discuss some difficulties and challenges that were faced and suggest how to alleviate such occurrences for sedimentary chemical analyses during future legs

Growth of Galactic Bulges by Mergers: I. Dense Satellites

Andredakis, Peletier & Balcells (1995) fit Sersic's law $\mu(r) \sim r^{1/n}$ to the bulges of the Balcells & Peletier (1994) galaxy sample, and infer that $n$ drops with morphological type T from $n \approx$ 4--6 for S0 to $n=1$ (exponential) for Sc's. We use collisionless N body simulations to test the assumption that initially the surface brightness profiles of all bulges were exponential, and that the steepening of the profiles toward the early-types is due to satellite accretion. The results are positive. After the accretion of a satellite, bulge-disk fits show that the bulge grows and that the bulge profile index $n$ increases proportional to the satellite mass. For a satellite as massive as the bulge, $n$ rises from 1 to 4. We present kinematic diagnostics on the remnants and disk thickening. The latter suggests that the bulge growth must have occurred before the last formation of a thin disk in the galaxy. The thick disks created by the merger are reminiscent of thick disks seen in early-type edge-on galaxies. The efficiency of the process suggests that present day bulges of late-type spirals showing exponential profiles cannot have grown significantly by collisionless mergers.Comment: 10 figures (8 poscript and 2 gif). accepted for publication in A&

"Galaxy," Defined

A growing number of low luminosity and low surface brightness astronomical objects challenge traditional notions of both galaxies and star clusters. To address this, we propose a definition of galaxy independent of the cold dark matter model of the universe: A galaxy is a gravitationally bound set of stars whose properties cannot be explained by a combination of baryons and Newton's laws of gravity. After exploring observational diagnostics of this definition, we examine the classification of ultra-faint dwarfs, globular clusters, ultra-compact dwarfs, and tidal dwarfs. While kinematic studies provide an effective galaxy diagnostic in many regimes, they can be less useful for compact or faint systems. To explore the use of [Fe/H] spread as a complementary diagnostic, we use published spectroscopic [Fe/H] measurements of 16 Milky Way dwarfs and 24 globular clusters to calculate their [Fe/H] spreads and uncertainties. Our principal results are: (i) no old star cluster less luminous then M_V = -10 has a significant (> 0.1 dex) spread in iron; (ii) known ultra-faint dwarfs can be classified with a combination of kinematics and [Fe/H]; (iii) the observed [Fe/H] spreads in massive (> 10^6 M_Sun) globular clusters do not necessarily imply they are the stripped nuclei of dwarfs, nor a need for dark matter; and (iv) if ultra-compact dwarfs reside in dark matter halos akin to those of ultra-faint dwarfs of the same half-light radii, then they will show no clear dynamical signature of dark matter. We suggest measurements that may assist future classification of massive globular clusters, ultra-compact dwarfs, and ultra-faint galaxies. Our galaxy definition is designed to be independent of the details of current observations and models, while our proposed diagnostics can be refined or replaced as our understanding of the universe evolves.Comment: Accepted by AJ; This updated version includes several new references, as well as improvements throughout the text for clarity - in particular clarifying our intended distinction between galaxy "definition" and "diagnostics