6,255 research outputs found
'The show must go on': Event dramaturgy as consolidation of community
Event dramaturgy and cultural performance have not been examined in the literature from a strategic standpoint of fostering the social value of events. Thus, the purpose of this study was to explore the case of the Water Carnival, a celebratory event in a rural community of Southwest Texas, demonstrating the essence of this event as a symbolic social space, wherein event participants instantiate a shared and valued sense of community. A hermeneutical approach was employed, interpreting the event and its symbolisms as a text, combined with findings from ethnographic fieldwork, including participant observation, in-depth interviews and analysis of archival documents. The study examines the ways that dramaturgy in the Water Carnival helps frame the ongoing public discourse for community improvement and enhances social capital. The implications of the study for social leverage of events are discussed. It is suggested that a foundation for strategic social planning is the understanding of events as symbolic social spaces and their embeddedness in community development, which can be accomplished when events are pertinent to public discourse, address community issues, represent an inclusive range of stakeholders, and promote cooperation
Solvegeometry gravitational waves
In this paper we construct negatively curved Einstein spaces describing
gravitational waves having a solvegeometry wave-front (i.e., the wave-fronts
are solvable Lie groups equipped with a left-invariant metric). Using the
Einstein solvmanifolds (i.e., solvable Lie groups considered as manifolds)
constructed in a previous paper as a starting point, we show that there also
exist solvegeometry gravitational waves. Some geometric aspects are discussed
and examples of spacetimes having additional symmetries are given, for example,
spacetimes generalising the Kaigorodov solution. The solvegeometry
gravitational waves are also examples of spacetimes which are indistinguishable
by considering the scalar curvature invariants alone.Comment: 10 pages; v2:more discussion and result
Finite Temperature Models of Bose-Einstein Condensation
The theoretical description of trapped weakly-interacting Bose-Einstein
condensates is characterized by a large number of seemingly very different
approaches which have been developed over the course of time by researchers
with very distinct backgrounds. Newcomers to this field, experimentalists and
young researchers all face a considerable challenge in navigating through the
`maze' of abundant theoretical models, and simple correspondences between
existing approaches are not always very transparent. This Tutorial provides a
generic introduction to such theories, in an attempt to single out common
features and deficiencies of certain `classes of approaches' identified by
their physical content, rather than their particular mathematical
implementation.
This Tutorial is structured in a manner accessible to a non-specialist with a
good working knowledge of quantum mechanics. Although some familiarity with
concepts of quantum field theory would be an advantage, key notions such as the
occupation number representation of second quantization are nonetheless briefly
reviewed. Following a general introduction, the complexity of models is
gradually built up, starting from the basic zero-temperature formalism of the
Gross-Pitaevskii equation. This structure enables readers to probe different
levels of theoretical developments (mean-field, number-conserving and
stochastic) according to their particular needs. In addition to its `training
element', we hope that this Tutorial will prove useful to active researchers in
this field, both in terms of the correspondences made between different
theoretical models, and as a source of reference for existing and developing
finite-temperature theoretical models.Comment: Detailed Review Article on finite temperature theoretical techniques
for studying weakly-interacting atomic Bose-Einstein condensates written at
an elementary level suitable for non-experts in this area (e.g. starting PhD
students). Now includes table of content
Early Universe Quantum Processes in BEC Collapse Experiments
We show that in the collapse of a Bose-Einstein condensate (BEC) {For an
excellent introduction to BEC theory, see C. Pethick and H. Smith,
Bose-Einstein condensation in dilute gases (Cambridge University Press,
Cambridge, England, 2002)} certain processes involved and mechanisms at work
share a common origin with corresponding quantum field processes in the early
universe such as particle creation, structure formation and spinodal
instability. Phenomena associated with the controlled BEC collapse observed in
the experiment of Donley et al E. Donley et. al., Nature 412, 295 (2001)(they
call it `Bose-Nova', see also J. Chin, J. Vogels and W. Ketterle, Phys. Rev.
Lett. 90, 160405 (2003)) such as the appearance of bursts and jets can be
explained as a consequence of the squeezing and amplification of quantum
fluctuations above the condensate by the dynamics of the condensate. Using the
physical insight gained in depicting these cosmological processes, our analysis
of the changing amplitude and particle contents of quantum excitations in these
BEC dynamics provides excellent quantitative fits with the experimental data on
the scaling behavior of the collapse time and the amount of particles emitted
in the jets. Because of the coherence properties of BEC and the high degree of
control and measurement precision in atomic and optical systems, we see great
potential in the design of tabletop experiments for testing out general ideas
and specific (quantum field) processes in the early universe, thus opening up
the possibility for implementing `laboratory cosmology'.Comment: 7 pages, 3 figures. Invited Talk presented at the Peyresq Meetings of
Gravitation and Cosmology, 200
Electrically-driven phase transition in magnetite nanostructures
Magnetite (FeO), an archetypal transition metal oxide, has been
used for thousands of years, from lodestones in primitive compasses[1] to a
candidate material for magnetoelectronic devices.[2] In 1939 Verwey[3] found
that bulk magnetite undergoes a transition at T 120 K from a
high temperature "bad metal" conducting phase to a low-temperature insulating
phase. He suggested[4] that high temperature conduction is via the fluctuating
and correlated valences of the octahedral iron atoms, and that the transition
is the onset of charge ordering upon cooling. The Verwey transition mechanism
and the question of charge ordering remain highly controversial.[5-11] Here we
show that magnetite nanocrystals and single-crystal thin films exhibit an
electrically driven phase transition below the Verwey temperature. The
signature of this transition is the onset of sharp conductance switching in
high electric fields, hysteretic in voltage. We demonstrate that this
transition is not due to local heating, but instead is due to the breakdown of
the correlated insulating state when driven out of equilibrium by electrical
bias. We anticipate that further studies of this newly observed transition and
its low-temperature conducting phase will shed light on how charge ordering and
vibrational degrees of freedom determine the ground state of this important
compound.Comment: 17 pages, 4 figure
Endomicroscopic and transcriptomic analysis of impaired barrier function and malabsorption in environmental enteropathy
Introduction: Environmental enteropathy (EE) is associated with growth failure, micronutrient malabsorption and impaired responses to oral vaccines. We set out to define cellular mechanisms of impaired barrier function in EE and explore protective mechanisms. Methods: We studied 49 adults with environmental enteropathy in Lusaka, Zambia using confocal laser endomicroscopy (CLE); histology, immunohistochemistry and mRNA sequencing of small intestinal biopsies; and correlated these with plasma lipopolysaccharide (LPS) and a zinc uptake test. Results: CLE images (median 134 for each study) showed virtually ubiquitous small intestinal damage. Epithelial defects, imaged by histology and claudin 4 immunostaining, were predominantly seen at the tips of villi and corresponded with leakage imaged in vivo by CLE. In multivariate analysis, circulating log-transformed LPS was correlated with cell shedding events (β = 0.83; P = 0.035) and with serum glucagon-like peptide-2 (β = -0.13; P = 0.007). Zinc uptake from a test dose of 25mg was attenuated in 30/47 (64%) individuals and in multivariate analysis was reduced by HIV, but positively correlated with GLP-2 (β = 2.72; P = 0.03). There was a U-shaped relationship between circulating LPS and villus surface area. Transcriptomic analysis identified 23 differentially expressed genes in severe enteropathy, including protective peptides and proteins. Conclusions: Confocal endomicroscopy, claudin 4 immunostaining and histology identify epithelial defects which are probably sites of bacterial translocation, in the presence of which increased epithelial surface area increases the burden of translocation. GLP 2 and other protective peptides may play an important role in mucosal protection in EE
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