A user evaluation of hierarchical phrase browsing

Phrase browsing interfaces based on hierarchies of phrases extracted automatically from document collections offer a useful compromise between automatic full-text searching and manually-created subject indexes. The literature contains descriptions of such systems that many find compelling and persuasive. However, evaluation studies have either been anecdotal, or focused on objective measures of the quality of automatically-extracted index terms, or restricted to questions of computational efficiency and feasibility. This paper reports on an empirical, controlled user study that compares hierarchical phrase browsing with full-text searching over a range of information seeking tasks. Users found the results located via phrase browsing to be relevant and useful but preferred keyword searching for certain types of queries. Users experiences were marred by interface details, including inconsistencies between the phrase browser and the surrounding digital library interface

The Vertical Structure of Planet-induced Gaps in Proto-Planetary Discs

Giant planets embedded in circumstellar discs are expected to open gaps in these discs. We examine the vertical structure of the gap edges. We find that the planet excites spiral arms with significant (Mach number of a half) vertical motion of the gas, and discuss the implications of these motions. In particular, the spiral arms will induce strong vertical stirring of the dust, making the edge appeared `puffed up' relative to the bulk of the disc. Infra-red observations (sensitive to dust) would be dominated by the light from the thick inner edge of the disc. Sub-millimetre observations (sensitive to gas velocities) would appear to be hot in `turbulent' motions (actually the ordered motion caused by the passage of the spiral arms), but cold in chemistry. Resolved sub-millimetre maps of circumstellar discs might even be able to detect the spiral arms directly.Comment: Revision adds new data, and corrects physical intepretatio

Design and experimental validation of a compact collimated Knudsen source

In this paper we discuss the design and performance of a collimated Knudsen source which has the benefit of a simple design over recirculating sources. Measurements of the flux, transverse velocity distribution and brightness at different temperatures were conducted to evaluate the performance. The scaling of the flux and brightness with the source temperature follow the theoretical predictions. The transverse velocity distribution in the transparent operation regime also agrees with the simulated data. The source was found able to produce a flux of $10^{14}$ s$^{-1}$ at a temperature of 433 K. Furthermore the transverse reduced brightness of an ion beam with equal properties as the atomic beam reads $1.7 \times 10^2$ A/(m${}^2$ sr eV) which is sufficient for our goal: the creation of an ultra-cold ion beam by ionization of a laser-cooled and compressed atomic rubidium beam

Knowledge and Perceptions of Agricultural Communications Pilot Curriculum in Arkansas Secondary Agricultural Classrooms

The purpose of this mixed-method study was to assess the effectiveness of agricultural communications curriculum developed and incorporated into a semester-long agricultural leadership and communications course for secondary agricultural education programs in Arkansas. Students (N = 297) participated in newly developed instructional modules addressing four categories of agriculture-themed curricula predetermined by a committee of agricultural education and communications faculty at the University of Arkansas (careers, writing, design, and multimedia). Student agricultural communications knowledge change was assessed using pre- and post-test instruments in each module of study. Additionally, content analysis of participating teachers’ journals was used to identify emergent themes related to teachers’ experiences teaching the curriculum throughout the semester. Overall, the findings from this study indicated students’ knowledge increased after instruction for each curriculum module: careers (16.2%), writing (23.1%), design (35.7%), and multimedia (31.3%). Lack of time, limited technology, teacher training, and curriculum content were the most common emergent themes among teachers. Based on findings from this study, it was concluded future efforts should be made to provide technology for agricultural education instructors to improve agricultural communications program effectiveness and reach

A local potential for the Weyl tensor in all dimensions

In all dimensions and arbitrary signature, we demonstrate the existence of a new local potential -- a double (2,3)-form -- for the Weyl curvature tensor, and more generally for all tensors with the symmetry properties of the Weyl curvature tensor. The classical four-dimensional Lanczos potential for a Weyl tensor -- a double (2,1)-form -- is proven to be a particular case of the new potential: its double dual.Comment: 7 pages; Late

Exploring Interactions Between Arkansas Urban Producers: Social Networks and Modes of Information Seeking

The purpose of this study was to explore the social networks and interactions between urban producers in Arkansas through a social network analysis. Using a mixed-methods approach, the current study collected data about participants’ social network interactions and methods of seeking information for urban farming. Results indicated how and where participants preferred to obtain information, peer-to-peer interactions within the network, and key players or opinion leaders in the network. The methods used in the current study may serve as an example of social network articulation for populations without a formal network to assist with outreach to communities potentially underserved by Extension

Description of the fluctuating colloid-polymer interface

To describe the full spectrum of surface fluctuations of the interface between phase-separated colloid-polymer mixtures from low scattering vector q (classical capillary wave theory) to high q (bulk-like fluctuations), one must take account of the interface's bending rigidity. We find that the bending rigidity is negative and that on approach to the critical point it vanishes proportionally to the interfacial tension. Both features are in agreement with Monte Carlo simulations.Comment: 5 pages, 3 figures, 1 table. Accepted for publication in Phys. Rev. Let

Exploring Communication Tendencies of Program Facilitators

Audience analysis is a critical skill to forge relationships and develop effective communications. Programs provided by the Cooperative Extension Service must be aware of external and internal audiences to provide relevant information and evoke impacts. Berlo’s (1960) Source-Message-Channel-Receiver Model of Communications guided this formative evaluation of Extension staff, and horse 4-H club volunteer leaders (program facilitators) to expose internal communication tendencies in Arkansas. Findings identified that program facilitators seek horse-related information from a variety of sources, most frequently relying on personal connections and least frequently seeking Extension sources. Program facilitators share a variety of messages and most frequently relay information about deadlines to club members. Messages about recruitment and fundraising were shared least often. Program facilitators described utilizing a variety of personal and electronic channels to share messages with the greatest frequency for in-person communications. Incoming channels were less diverse than outgoing channels and primarily featured email, which program facilitators preferred. Program facilitators are primarily female, aged in their thirties, described lifetime involvement with 4-H and the horse industry, and most frequently reported having less than five years’ experience in their current position. The ground-level perspective of facilitators’ demographics and communication tendencies was evident in results of this study. In application, practitioners must continue to actively seek relationships with audiences, remain cognizant of communication factors, and provide accurate messaging through preferred channels

Invariant classification and the generalised invariant formalism: conformally flat pure radiation metrics, with zero cosmological constant

Metrics obtained by integrating within the generalised invariant formalism are structured around their intrinsic coordinates, and this considerably simplifies their invariant classification and symmetry analysis. We illustrate this by presenting a simple and transparent complete invariant classification of the conformally flat pure radiation metrics (except plane waves) in such intrinsic coordinates; in particular we confirm that the three apparently non-redundant functions of one variable are genuinely non-redundant, and easily identify the subclasses which admit a Killing and/or a homothetic Killing vector. Most of our results agree with the earlier classification carried out by Skea in the different Koutras-McIntosh coordinates, which required much more involved calculations; but there are some subtle differences. Therefore, we also rework the classification in the Koutras-McIntosh coordinates, and by paying attention to some of the subtleties involving arbitrary functions, we are able to obtain complete agreement with the results obtained in intrinsic coordinates. In particular, we have corrected and completed statements and results by Edgar and Vickers, and by Skea, about the orders of Cartan invariants at which particular information becomes available.Comment: Extended version of GRG publication, with some typos etc correcte

Radiative Transfer in Star Formation: Testing FLD and Hybrid Methods

We perform a comparison between two radiative transfer algorithms commonly employed in hydrodynamical calculations of star formation: grey flux limited diffusion and the hybrid scheme, in addition we compare these algorithms to results from the Monte-Carlo radiative transfer code MOCASSIN. In disc like density structures the hybrid scheme performs significantly better than the FLD method in the optically thin regions, with comparable results in optically thick regions. In the case of a forming high mass star we find the FLD method significantly underestimates the radiation pressure by a factor of ~100.Comment: 4 Pages; to appear in the proceedings of 'The Labyrinth of Star Formation', Crete, 18-22 June 201