14,330 research outputs found
Learning Membership Functions in a Function-Based Object Recognition System
Functionality-based recognition systems recognize objects at the category
level by reasoning about how well the objects support the expected function.
Such systems naturally associate a ``measure of goodness'' or ``membership
value'' with a recognized object. This measure of goodness is the result of
combining individual measures, or membership values, from potentially many
primitive evaluations of different properties of the object's shape. A
membership function is used to compute the membership value when evaluating a
primitive of a particular physical property of an object. In previous versions
of a recognition system known as Gruff, the membership function for each of the
primitive evaluations was hand-crafted by the system designer. In this paper,
we provide a learning component for the Gruff system, called Omlet, that
automatically learns membership functions given a set of example objects
labeled with their desired category measure. The learning algorithm is
generally applicable to any problem in which low-level membership values are
combined through an and-or tree structure to give a final overall membership
value.Comment: See http://www.jair.org/ for any accompanying file
FearNot! An Anti-Bullying Intervention: Evaluation of an Interactive Virtual Learning Environment
Original paper can be found at: http://www.aisb.org.uk/publications/proceedings.shtm
Non Local Electron-Phonon Correlations in a Dispersive Holstein Model
Due to the dispersion of optical phonons, long range electron-phonon
correlations renormalize downwards the coupling strength in the Holstein model.
We evaluate the size of this effect both in a linear chain and in a square
lattice for a time averaged {\it e-ph} potential, where the time variable is
introduced according to the Matsubara formalism. Mapping the Holstein
Hamiltonian onto the time scale we derive the perturbing source current which
appears to be non time retarded. This property permits to disentangle phonon
and electron coordinates in the general path integral for an electron coupled
to dispersive phonons. While the phonon paths can be integrated out
analytically, the electron path integrations have to be done numerically. The
equilibrium thermodynamic properties of the model are thus obtained as a
function of the electron hopping value and of the phonon spectrum parameters.
We derive the {\it e-ph} corrections to the phonon free energy and show that
its temperature derivatives do not depend on the {\it e-ph} effective coupling
hence, the Holstein phonon heat capacity is strictly harmonic. A significant
upturn in the low temperature total heat capacity over ratio is attributed
to the electron hopping which largely contributes to the action.Comment: Phys.Rev.B (2005
Patient obesity and the practical experience of the plain radiography professional: on everyday ethics, patient positioning and infelicitous equipment
Patient obesity is increasingly placing significant and multifaceted strain upon medical imaging departments, and professionals, in (particularly Western) healthcare systems. The majority of obesity-related studies in radiology are, however, primarily focused only upon the technical business of collecting diagnostically-efficacious images. This study, using Interpretative Phenomenological Analysis (IPA), qualitatively explores the everyday clinical experiences of eight expert UK diagnosticians working in plain radiography. Focus herein falls particularly upon (a) problems with patient positioning during examination, and (b) challenges arising around available equipment. In line with extant research, participants reported that difficulties with positioning obese patients could have negative impacts on image quality, and that insufficient table weight limits and widths, and inadequate detector sizes, can adversely affect examination. They also raised some more novel issues, such as how the impact of available gown sizes upon a patient’s sense of dignity can cause practical and ethical dilemmas for a clinician in situ. The issue of how one might ‘train’ experience in positioning patients without bony landmarks as a reference point was also made salient, with strong implications for undergraduate radiography curricula. It is finally highlighted how the participating radiographers themselves seldom conceptualised any given problem as a purely ‘technical’ one, instead recurrently recognising the interlinking of material, socio-economic and moral matters in real healthcare contexts. By better understanding such nuance and complexity as lived by real radiographers, it is contended, a more context-sensitive and flexible path to effective training and guideline-production can be mapped
Strong exciton-plasmon coupling in semiconducting carbon nanotubes
We study theoretically the interactions of excitonic states with surface
electromagnetic modes of small-diameter (~1 nm) semiconducting single-walled
carbon nanotubes. We show that these interactions can result in strong
exciton-surface-plasmon coupling. The exciton absorption line shape exhibits
Rabi splitting ~0.1 eV as the exciton energy is tuned to the nearest interband
surface plasmon resonance of the nanotube. We also show that the quantum
confined Stark effect may be used as a tool to control the exciton binding
energy and the nanotube band gap in carbon nanotubes in order, e.g., to bring
the exciton total energy in resonance with the nearest interband plasmon mode.
The exciton-plasmon Rabi splitting we predict here for an individual carbon
nanotube is close in its magnitude to that previously reported for hybrid
plasmonic nanostructures artificially fabricated of organic semiconductors on
metallic films. We expect this effect to open up paths to new tunable
optoelectronic device applications of semiconducting carbon nanotubes.Comment: 22 pages, 8 figures, accepted for PR
Cell cycle-dependent phosphorylation of Theileria annulata schizont surface proteins
The invasion of Theileria sporozoites into bovine leukocytes is rapidly followed by the destruction of the surrounding host cell membrane, allowing the parasite to establish its niche within the host cell cytoplasm. Theileria infection induces host cell transformation, characterised by increased host cell proliferation and invasiveness, and the activation of anti-apoptotic genes. This process is strictly dependent on the presence of a viable parasite. Several host cell kinases, including PI3-K, JNK, CK2 and Src-family kinases, are constitutively activated in Theileria-infected cells and contribute to the transformed phenotype. Although a number of host cell molecules, including IkB kinase and polo-like kinase 1 (Plk1), are recruited to the schizont surface, very little is known about the schizont molecules involved in host-parasite interactions. In this study we used immunofluorescence to detect phosphorylated threonine (p-Thr), serine (p-Ser) and threonine-proline (p-Thr-Pro) epitopes on the schizont during host cell cycle progression, revealing extensive schizont phosphorylation during host cell interphase. Furthermore, we established a quick protocol to isolate schizonts from infected macrophages following synchronisation in S-phase or mitosis, and used mass spectrometry to detect phosphorylated schizont proteins. In total, 65 phosphorylated Theileria proteins were detected, 15 of which are potentially secreted or expressed on the surface of the schizont and thus may be targets for host cell kinases. In particular, we describe the cell cycle-dependent phosphorylation of two T. annulata surface proteins, TaSP and p104, both of which are highly phosphorylated during host cell S-phase. TaSP and p104 are involved in mediating interactions between the parasite and the host cell cytoskeleton, which is crucial for the persistence of the parasite within the dividing host cell and the maintenance of the transformed state
Prediction of strong shock structure using the bimodal distribution function
A modified Mott-Smith method for predicting the one-dimensional shock wave
solution at very high Mach numbers is constructed by developing a system of
fluid dynamic equations. The predicted shock solutions in a gas of Maxwell
molecules, a hard sphere gas and in argon using the newly proposed formalism
are compared with the experimental data, direct-simulation Monte Carlo (DSMC)
solution and other solutions computed from some existing theories for Mach
numbers M<50. In the limit of an infinitely large Mach number, the predicted
shock profiles are also compared with the DSMC solution. The density,
temperature and heat flux profiles calculated at different Mach numbers have
been shown to have good agreement with the experimental and DSMC solutionsComment: 22 pages, 9 figures, Accepted for publication in Physical Review
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