Dust Echos from Gamma Ray Bursts

The deviation from the power-law decline of the optical flux observed in GRB 970228 and GRB 980326 has been used recently to argue in favor of the connection between GRBs and supernovae. We consider an alternative explanation for this phenomenon, based on the scattering of a prompt optical burst by 0.1 solar masses of dust located beyond its sublimation radius 0.1-1 pc from the burst. In both cases, the optical energy observed at the time of the first detection of the afterglow suffices to produce an echo after 20-30 days, as observed. Prompt optical monitoring of future bursts and multiband photometry of the afterglows will enable quantitative tests of simple models of dust reprocessing and a prediction of the source redshift.Comment: 4 pages including 3 postscript figures, LaTeX (emulateapj.sty; newapa.sty for bibliography definitions); accepted for publication in ApJ

On The Synchrotron Self-Compton Emission from Relativistic Shocks and Its Implications for Gamma-Ray Burst Afterglows

We consider the effects of inverse Compton scattering of synchrotron photons from relativistic electrons in GRB afterglows. We compute the spectrum of the inverse Compton emission and find that it can dominate the total cooling rate of the afterglow for several months or even years after the initial explosion. We demonstrate that the presence of strong inverse Compton cooling can be deduced from the effect it has on the time-evolution of the cooling break in the synchrotron spectral component, and therefore on the optical and X-ray afterglow lightcurves. We then show how the physical interpretation of the observed characteristics of the synchrotron spectrum must be modified to take into consideration this extra source of cooling, and give a revised prescription for computing physical parameters characterizing the expanding shock wave from the observed quantities. We find that for a given set of observables (synchrotron break frequencies and fluxes) there is either no consistent physical interpretation or two of them. Finally we discuss the prospects of directly detecting the inverse Compton emission with Chandra. We argue that such a detection is possible for GRBs exploding in a reasonably dense (n>1 cm^-3) medium.Comment: 21 pages, ApJ submitte

Discovery-led refinement in e-discovery investigations: sensemaking, cognitive ergonomics and system design.

Given the very large numbers of documents involved in e-discovery investigations, lawyers face a considerable challenge of collaborative sensemaking. We report findings from three workplace studies which looked at different aspects of how this challenge was met. From a sociotechnical perspective, the studies aimed to understand how investigators collectively and individually worked with information to support sensemaking and decision making. Here, we focus on discovery-led refinement; specifically, how engaging with the materials of the investigations led to discoveries that supported refinement of the problems and new strategies for addressing them. These refinements were essential for tractability. We begin with observations which show how new lines of enquiry were recursively embedded. We then analyse the conceptual structure of a line of enquiry and consider how reflecting this in e-discovery support systems might support scalability and group collaboration. We then focus on the individual activity of manual document review where refinement corresponded with the inductive identification of classes of irrelevant and relevant documents within a collection. Our observations point to the effects of priming on dealing with these efficiently and to issues of cognitive ergonomics at the human–computer interface. We use these observations to introduce visualisations that might enable reviewers to deal with such refinements more efficiently

Requirements of Time Management Tools for Outpatient Physiotherapy Practice

Abstract The effects of electronic appointment booking systems on the time management activities of health professionals have received little attention to date. We report on time management practices in three outpatient physiotherapy departments with different paper and electronic systems. The study has identified a set of time management activities and associated social behaviours common to physiotherapy departments. The convenience, flexibility and expressive nature of paper diary systems is of significant value to users, whilst the clarity and superior database functionality of electronic systems are valued by staff using this medium. The study highlights several potential barriers to the effective deployment of electronic booking systems in physiotherapy departments including poor resource and training provision, concerns regarding restrictive diary control measures, the continued reliance on burdensome duplication procedures and the need to coordinate multiple information artefacts, which need to be addressed if such technology is to be successfully designed and deployed

How external and internal resources influence user action: the case of infusion devices

Human error can have potentially devastating consequences in contexts such as healthcare, but there is a rarely a simple dichotomy between errors and correct behaviour. Furthermore, there has been little consideration of how the activities of users (erroneous and otherwise) relate to the conceptual fit between user and device, despite the fact that healthcare technologies are becoming increasingly prevalent and complex. In this article, we present a study in which nurses’ conceptions of infusion device practice were elicited to identify misfits. By focusing on key concepts that users work with when setting up infusions and the extent to which the system supports them, our analysis highlights how actions are influenced by the different resources available to users including: the device itself; supporting artefacts; the conceptual understanding of the user; and the community of practice the user is part of. The findings reveal the ways in which users are resourceful in their day-to-day activities and also suggest potential vulnerabilities within the wider system that could threaten patient safety. Our approach is able to make previously under-explored aspects of practice visible, thus enabling insight into how users act and why

The unseen and unacceptable face of digital libraries

The social and organizational aspects of digital libraries are often overlooked but this paper reviews how they can affect users' awareness and acceptance of digital libraries. An analysis of research conducted within two contrasting domains (Clinical and Academic) is presented which highlights issues of user interactions, work practices and the organizational social structures. The combined study comprises an analysis of 98 in-depth interviews and focus groups with lecturers, librarians and hospital clinicians. The importance of current and past roles of the library, and how users interacted with it, are revealed. Web-based digital libraries, while alleviating most library resource and interaction problems, require a change in librarians' and DL designers' roles and interaction patterns if they are to be implemented acceptably and effectively. Without this role change, users will at best be unaware of these digital resources and at worst feel threatened by them. The findings of this paper highlight the importance on DL design and implementation of the social context and supporting user communication (i.e. collaboration and consultation) in their information search and usage activities

Using machine learning to infer reasoning provenance from user interaction log data: based on the data/frame theory of sensemaking

The reconstruction of analysts’ reasoning processes (reasoning provenance) during complex sensemaking tasks can support reflection and decision making. One potential approach to such reconstruction is to automatically infer reasoning from low-level user interaction logs. We explore a novel method for doing this using machine learning. Two user studies were conducted in which participants performed similar intelligence analysis tasks. In one study, participants used a standard web browser and word processor; in the other, they used a system called INVISQUE (Interactive Visual Search and Query Environment). Interaction logs were manually coded for cognitive actions based on captured think-aloud protocol and posttask interviews based on Klein, Phillips, Rall, and Pelusos’s data/frame model of sensemaking as a conceptual framework. This analysis was then used to train an interaction frame mapper, which employed multiple machine learning models to learn relationships between the interaction logs and the codings. Our results show that, for one study at least, classification accuracy was significantly better than chance and compared reasonably to a reported manual provenance reconstruction method. We discuss our results in terms of variations in feature sets from the two studies and what this means for the development of the method for provenance capture and the evaluation of sensemaking systems

Strategies for conducting situated studies of technology use in hospitals

Ethnographic methods are widely used for understanding situated practices with technology. When authors present their data gathering methods, they almost invariably focus on the bare essentials. These enable the reader to comprehend what was done, but leave the impression that setting up and conducting the study was straightforward. Text books present generic advice, but rarely focus on specific study contexts. In this paper, we focus on lessons learnt by non-clinical researchers studying technology use in hospitals: gaining access; developing good relations with clinicians and patients; being outsiders in healthcare settings; and managing the cultural divide between technology human factors and clinical practice. Drawing on case studies across various hospital settings, we present a repertoire of ways of working with people and technologies in these settings. These include engaging clinicians and patients effectively, taking an iterative approach to data gathering and being responsive to the demands and opportunities provided by the situation. The main contribution of this paper is to make visible many of the lessons we have learnt in conducting technology studies in healthcare, using these lessons to present strategies that other researchers can take up