518 research outputs found
Working with and for social enterprises: the role of the volunteer ethnographer
Purpose â This paper considers the specific opportunities and challenges of engaging in ethnographic research with organisations in which the researcher participates as a volunteer ethnographer. Design/methodology/approach â The findings in this paper are based on four years of ethnographic research within a social enterprise. Findings â This paper finds that there are significant benefits of the role of the volunteer ethnographer and suggests ways to address some of the challenges. Research limitations/implications â As the field of social enterprise and ethnography grows and researchers engage with methodological discussions about participant observation, the authors suggest that attention should also be paid to the specifics of the role of the volunteer ethnographer. Originality/value â There is growing interest in the use of ethnography in social enterprises. This paper offers unique insight into how this methodology has been applied in the context of self-reliant groups and the importance of the engaging with discussion about the specific role of the volunteer ethnographer
A Singular Conformal Spacetime
The infinite cosmological "constant" limit of the de Sitter solutions to
Einstein's equation is studied. The corresponding spacetime is a singular,
four-dimensional cone-space, transitive under proper conformal transformations,
which constitutes a new example of maximally-symmetric spacetime. Grounded on
its geometric and thermodynamic properties, some speculations are made in
connection with the primordial universe.Comment: RevTeX4, 10 pages, 1 eps figure. Presentation changes, including a
new title; section II.E, on the thermodynamic properties of the de Sitter
horizon, completely revised. Version to be published in Journal of Geometry
and Physic
Galaxy rotation curves: the effect of j x B force
Using the Galaxy as an example, we study the effect of j x B force on the
rotational curves of gas and plasma in galaxies. Acceptable model for the
galactic magnetic field and plausible physical parameters are used to fit the
flat rotational curve for gas and plasma based on the observed baryonic
(visible) matter distribution and j x B force term in the static MHD equation
of motion. We also study the effects of varied strength of the magnetic field,
its pitch angle and length scale on the rotational curves. We show that j x B
force does not play an important role on the plasma dynamics in the
intermediate range of distances 6-12 kpc from the centre, whilst the effect is
sizable for larger r (r > 15 kpc), where it is the most crucial.Comment: Accepted for publication in Astrophysics & Space Science (final
printed version, typos in proofs corrected
A search for new members of the ÎČPictoris, Tucana-Horologium and ÉCha moving groups in the RAVE data base
We report on the discovery of new members of nearby young moving groups, exploiting the full power of combining the Radial Velocity Experiment (RAVE) survey with several stellar age diagnostic methods and follow-up high-resolution optical spectroscopy. The results include the identification of one new and five likely members of the ÎČPictoris moving group, ranging from spectral types F9 to M4 with the majority being M dwarfs, one K7 likely member of the ΔCha group and two stars in the Tucana-Horologium association. Based on the positive identifications, we foreshadow a great potential of the RAVE data base in progressing towards a full census of young moving groups in the solar neighbourhood
Volcanic and Tectonic Constraints on the Evolution of Venus
Surface geologic features form a detailed record of Venusâ evolution. Venus displays a profusion of volcanic and tectonics features, including both familiar and exotic forms. One challenge to assessing the role of these features in Venusâ evolution is that there are too few impact craters to permit age dates for specific features or regions. Similarly, without surface water, erosion is limited and cannot be used to evaluate age. These same observations indicate Venus has, on average, a very young surface (150â1000 Ma), with the most recent surface deformation and volcanism largely preserved on the surface except where covered by limited impact ejecta. In contrast, most geologic activity on Mars, the Moon, and Mercury occurred in the 1st billion years. Earthâs geologic processes are almost all a result of plate tectonics. Venusâ lacks such a network of connected, large scale plates, leaving the nature of Venusâ dominant geodynamic process up for debate. In this review article, we describe Venusâ key volcanic and tectonic features, models for their origin, and possible links to evolution. We also present current knowledge of the composition and thickness of the crust, lithospheric thickness, and heat flow given their critical role in shaping surface geology and interior evolution. Given Venusâ hot lithosphere, abundant activity and potential analogues of continents, roll-back subduction, and microplates, it may provide insights into early Earth, prior to the onset of true plate tectonics. We explore similarities and differences between Venus and the Proterozoic or Archean Earth. Finally, we describe the future measurements needed to advance our understanding of volcanism, tectonism, and the evolution of Venus
Charged AdS Black Holes and Catastrophic Holography
We compute the properties of a class of charged black holes in anti-de Sitter
space-time, in diverse dimensions. These black holes are solutions of
consistent Einstein-Maxwell truncations of gauged supergravities, which are
shown to arise from the inclusion of rotation in the transverse space. We
uncover rich thermodynamic phase structures for these systems, which display
classic critical phenomena, including structures isomorphic to the van der
Waals-Maxwell liquid-gas system. In that case, the phases are controlled by the
universal `cusp' and `swallowtail' shapes familiar from catastrophe theory. All
of the thermodynamics is consistent with field theory interpretations via
holography, where the dual field theories can sometimes be found on the world
volumes of coincident rotating branes.Comment: 19 pages, revtex, psfig, 6 multicomponent figures, typos, references
and a few remarks have been repaired, and adde
A Unified Tool for Performance Modelling and Prediction
Abstract. We describe a novel performability modelling approach which facilitates the efficient solution of performance models extracted from high-level descriptions of systems. The notation which we use for our high-level designs is the UML graphical modelling language. The technology which provides the efficient representation capability for the underlying performance model is the MTBDD-based PRISM probabilistic model checker. The UML models are compiled through an intermediate language, the stochastic process algebra PEPA, before translation into MTBDDs for solution. We illustrate our approach on a real-world analysis problem from the domain of mobile telephony. 1 Introduction Distributed, mobile and global computing environments provide robust development challenges to practising software system developers. Working with rapidlychanging implementation technology means that developers often must spend some of their development time finding and correcting errors in the software libraries and APIs which they use. Fortifying this difficulty is the arduous terrain of dynamic distributed systems where the difficulty of replaying a communication sequence which led to a system fault confounds the process of detecting and correcting implementation errors. In this setting, application developers rarely wish to expend the investment of time which would be needed to build and analyse a performance model of the system which they are developing. The concepts and the modelling languages of performance analysis are relatively unfamiliar to software developers and when already faced with a generous range of other difficulties in the development process, early predictive performance analysis can easily be overlooked
Diving deep into digital literacy:emerging methods for research
Literacy studies approaches have tended to adopt a position which enables ethnographic explorations of a wide range of âliteraciesâ. An important issue arising is the new challenge required for researchers to capture, manage, and analyse data that highlight the unique character of practices around texts in digital environments. Such inquiries, we argue, require multiple elements of data to be captured and analysed as part of effective literacy ethnographies. These include such things as the unfolding of digital texts, the activities around them, and features of the surrounding social and material environment. This paper addresses these methodological issues drawing from three educationally focused studies, and reporting their experiences and insights within uniquely different contexts. We deal with the issue of adopting new digital methods for literacy research through the notion of a âdeep diveâ to explore educational tasks in classrooms. Through a discussion of how we approached the capture and analysis of our data, we present methods to better understand digital literacies in education. We then outline challenges posed by our methods, how they can be used more broadly for researching interaction in digital environments, and how they augment transdisciplinary debates and trends in research methods
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
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