338 research outputs found
Reflecting on the technical development of the Mapping Sculpture project
This paper explains, evaluates and reflects on the technical challenges and opportunities that underpin both the Mapping Sculpture project and its mobile interface. It provides insights into the development process as an integral component of the research methodology, and highlights the importance of meaningful collaboration between researchers and software developers. Just as the project questions the conventional notion of the lone sculpture practitioner, so the technical development needed to mirror the complex web of connections between people, places, objects, organizations and events through enabling large-scale, distributed and collaborative research. Enabling access to these rich resources on mobile devices was a further innovative and challenging development, but one that opens up the possibility for fresh modes of access and development of new audiences. The success of this technical development offers a model for representing complex relationships hidden in multiple sources, enabling innovative research and enhancing access
Adaptive Detection of Instabilities: An Experimental Feasibility Study
We present an example of the practical implementation of a protocol for
experimental bifurcation detection based on on-line identification and feedback
control ideas. The idea is to couple the experiment with an on-line
computer-assisted identification/feedback protocol so that the closed-loop
system will converge to the open-loop bifurcation points. We demonstrate the
applicability of this instability detection method by real-time,
computer-assisted detection of period doubling bifurcations of an electronic
circuit; the circuit implements an analog realization of the Roessler system.
The method succeeds in locating the bifurcation points even in the presence of
modest experimental uncertainties, noise and limited resolution. The results
presented here include bifurcation detection experiments that rely on
measurements of a single state variable and delay-based phase space
reconstruction, as well as an example of tracing entire segments of a
codimension-1 bifurcation boundary in two parameter space.Comment: 29 pages, Latex 2.09, 10 figures in encapsulated postscript format
(eps), need psfig macro to include them. Submitted to Physica
Description of a presumptive hepatopancreatic reovirus, and a putative gill parvovirus, in the freshwater crayfish Cherax quadricarinatus
The redclaw freshwater crayfish Cherax quadricarinatus has a reputation for being hardy and resistant to handling stress. However, in recent years, possibly since 1996, C. quadricarinatus farmers in northern Queensland have noted a decrease in stress resistance in their stock. A presumptive reovirus in the hepatopancreas, and a putative parvovirus in the gills, were associated with chronic mortalities in C. quadricarinatus at one northern Queensland farm. Hypertrophic nuclei with marginated chromatin were observed in gill epithelium in moribund crayfish which had recently been relocated to a laboratory from the holding tank facility on the farm. Affected nuclei appeared to be vacant or contained a faint granular basophilia in H&E stained sections. However, toluidine blue staining revealed a homogeneously granular appearance of the nuclei. Transmission electron microscopy revealed approximately 20 nm diameter virus-like particles within the nucleus. Eosinophilic, Feulgen-negative, cytoplasmic inclusions were observed in distal hepatopancreatocytes in 1 moribund C. quadricarinatus collected from the same on-farm holding tank approximately 6 mo later. This crayfish did not display the gill lesions. Transmission electron microscopy showed that the inclusions contained icosahedral virus particles 35 to 40 nm in diameter. The histopathology and preliminary virus morphology of the presumptive hepatopancreatic reovirus, and the histopathology, ultrastructural pathology and preliminary virus morphology of the putative gill parvovirus, are reported herein
Heat Kernel on Homogeneous Bundles over Symmetric Spaces
We consider Laplacians acting on sections of homogeneous vector bundles over
symmetric spaces. By using an integral representation of the heat semi-group we
find a formal solution for the heat kernel diagonal that gives a generating
function for the whole sequence of heat invariants. We show explicitly that the
obtained result correctly reproduces the first non-trivial heat kernel
coefficient as well as the exact heat kernel diagonals on two-dimensional
sphere and the hyperbolic plane . We argue that the obtained formal
solution correctly reproduces the exact heat kernel diagonal after a suitable
regularization and analytical continuation.Comment: 55 page
Vacuum polarization in the spacetime of charged nonlinear black hole
Building on general formulas obtained from the approximate renormalized
effective action, the approximate stress-energy tensor of the quantized massive
scalar field with arbitrary curvature coupling in the spacetime of charged
black hole being a solution of coupled equations of nonlinear electrodynamics
and general relativity is constructed and analysed. It is shown that in a few
limiting cases, the analytical expressions relating obtained tensor to the
general renormalized stress-energy tensor evaluated in the geometry of the
Reissner-Nordstr\"{o}m black hole could be derived. A detailed numerical
analysis with special emphasis put on the minimal coupling is presented and the
results are compared with those obtained earlier for the conformally coupled
field. Some novel features of the renormalized stress-energy tensor are
discussed
Quantum backreaction of massive fields and self-consistent semiclassical extreme black holes and acceleration horizons
We consider the effect of backreaction of quantized massive fields on the
metric of extreme black holes (EBH). We find the analytical approximate
expression for the stress-energy tensor for a scalar (with an arbitrary
coupling), spinor and vector fields near an event horizon. We show that,
independent of a concrete type of EBH, the energy measured by a freely falling
observer is finite on the horizon, so that quantum backreaction is consistent
with the existence of EBH. For the Reissner-Nordstrom EBH with a total mass
M_{tot} and charge Q we show that for all cases of physical interest M_{tot}<
Q. We also discuss different types of quantum-corrected Bertotti-Robinson
spacetimes, find for them exact self-consistent solutions and consider
situations in which tiny quantum corrections lead to the qualitative change of
the classical geometry and topology. In all cases one should start not from a
classical background with further adding quantum corrections but from the
quantum-corrected self-consistent geometries from the very beginning.Comment: Minor corrections. To appear in Phys. Rev.
Exact perturbative solution of the Kondo problem
We explicitly evaluate the infinite series of integrals that appears in the
"Anderson-Yuval" reformulation of the anisotropic Kondo problem in terms of a
one-dimensional Coulomb gas. We do this by developing a general approach
relating the anisotropic Kondo problem of arbitrary spin with the boundary
sine-Gordon model, which describes impurity tunneling in a Luttinger liquid and
in the fractional quantum Hall effect. The Kondo solution then follows from the
exact perturbative solution of the latter model in terms of Jack polynomials.Comment: 4 pages in revtex two-colum
Technological Devices in the Archives: A Policy Analysis
Doing research in the archive is the cornerstone of humanities scholarship.
Various archives institute policies regarding the use of technological
devices, such as mobile phones, laptops, and cameras in their reading rooms.
Such policies directly affect the scholars as the devices mediate the nature of
their interaction with the source materials in terms of capturing, organizing,
note taking, and record keeping for future use of found materials. In this paper,
we present our analysis of the policies of thirty archives regarding the use of
technology in their reading rooms. This policy analysis, along with data from
interviews of scholars and archivists, is intended to serve as a basis for developing
mobile applications for assisting scholars in their research activities. In this
paper we introduce an early prototype of such a mobile application—
AMTracker.Informatio
An adaptive inelastic magnetic mirror for Bose-Einstein condensates
We report the reflection and focussing of a Bose-Einstein condensate by a new
pulsed magnetic mirror. The mirror is adaptive, inelastic, and of extremely
high optical quality. The deviations from specularity are less than 0.5 mrad
rms, making this the best atomic mirror demonstrated to date. We have also used
the mirror to realize the analog of a beam-expander, producing an ultra-cold
collimated fountain of matter wavesComment: 4 pages, 4 figure
Renormalization Group and Decoupling in Curved Space: II. The Standard Model and Beyond
We continue the study of the renormalization group and decoupling of massive
fields in curved space, started in the previous article and analyse the higher
derivative sector of the vacuum metric-dependent action of the Standard Model.
The QCD sector at low-energies is described in terms of the composite effective
fields. For fermions and scalars the massless limit shows perfect
correspondence with the conformal anomaly, but similar limit in a massive
vector case requires an extra compensating scalar. In all three cases the
decoupling goes smoothly and monotonic. A particularly interesting case is the
renormalization group flow in the theory with broken supersymmetry, where the
sign of one of the beta-functions changes on the way from the UV to IR.Comment: 27 pages, 8 figure
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