284 research outputs found
Bose-Einstein condensation of excitons in CuO
We present a parameter-free model which estimates the density of excitons in
CuO, related to experiments that have tried to create an excitonic
Bose-Einstein condensate. Our study demonstrates that the triplet-state
excitons move along adiabats and obey classical statistics, while the
singlet-state excitons are a possible candidate for forming a Bose-Einstein
condensate. Finally we show that the results of this study do not change
qualitatively in a two-dimensional exciton gas, which can be realized in a
quantum well.Comment: 6 pages, RevTex, 1 ps figur
Metabolite changes in blood predict the onset of tuberculosis
Immunogenetics and cellular immunology of bacterial infectious disease
Forging Partnerships in Health Care: Process and Measuring Benefits
Universally, there is concern that much academic learning has dealt mainly in theory, removing knowledge from context with a resultant lack of practical experience. Here, the catalyst for strengthening university-community engagement, emanated from a desire to foster greater propensity within students to make connections between their academic courses and responsibility toward the community and people in need, and thus develop enhanced skills in social interaction, teamwork and effectiveness. This paper explores a variety of models of university-community engagement that aim to achieve and model good practice in policy making and planning around healthcare education and service development. Ways of integrating teaching and learning with community engagement, so there is reciprocal learning with significant benefits to the community, students, the university and industry are described. The communities of engagement for a transdisciplinary approach in healthcare are defined and the types of collaborative partnerships are outlined, including public/private partnerships, service learning approaches and regional campus engagement. The processes for initiating innovation in this field, forging sustainable partnerships, providing cooperative leadership and building shared vision are detailed. Measuring shared and sustained benefits for all participants is examined in the context of effecting changes in working relationships as well as the impact on students in terms of increased personal and social responsibility, confidence and competence. For the health professions, it is considered vital to adopt this approach in order to deliver graduates who feel aware of community needs, believe they can make a difference, and have a greater sense of community responsibility, ethic of service and more sophisticated understandings of social contexts. In the longer term, it is proposed the strategy will deliver a future healthcare workforce that is more likely to have a strengthened sense of community, social and personal responsibility and thus effect positive social change
Stress Dependence of Exciton Relaxation Processes in Cu2O
A comprehensive study of the exciton relaxation processes in Cu2O has led to
some surprises. We find that the ortho-para conversion rate becomes slower at
high stress, and that the Auger nonradiative recombination rate increases with
stress, with apparently no Auger recombination at zero stress. These results
have important consequences for the pursuit of Bose-Einstein condensation of
excitons in a harmonic potential.Comment: 10 figures, 1 tabl
Quantum saturation and condensation of excitons in CuO: a theoretical study
Recent experiments on high density excitons in CuO provide evidence for
degenerate quantum statistics and Bose-Einstein condensation of this nearly
ideal gas. We model the time dependence of this bosonic system including
exciton decay mechanisms, energy exchange with phonons, and interconversion
between ortho (triplet-state) and para (singlet-state) excitons, using
parameters for the excitonic decay, the coupling to acoustic and low-lying
optical phonons, Auger recombination, and ortho-para interconversion derived
from experiment. The single adjustable parameter in our model is the
optical-phonon cooling rate for Auger and laser-produced hot excitons. We show
that the orthoexcitons move along the phase boundary without crossing it (i.e.,
exhibit a ``quantum saturation''), as a consequence of the balance of entropy
changes due to cooling of excitons by phonons and heating by the non-radiative
Auger two-exciton recombination process. The Auger annihilation rate for
para-para collisions is much smaller than that for ortho-para and ortho-ortho
collisions, explaining why, under the given experimental conditions, the
paraexcitons condense while the orthoexcitons fail to do so.Comment: Revised to improve clarity and physical content 18 pages, revtex,
figures available from G. Kavoulakis, Physics Department, University of
Illinois, Urban
Geometric Spin Hall Effect of Light at Polarizing Interfaces
The geometric Spin Hall Effect of Light (geometric SHEL) amounts to a
polarization-dependent positional shift when a light beam is observed from a
reference frame tilted with respect to its direction of propagation. Motivated
by this intriguing phenomenon, the energy density of the light beam is
decomposed into its Cartesian components in the tilted reference frame. This
illustrates the occurrence of the characteristic shift and the significance of
the effective response function of the detector.
We introduce the concept of a tilted polarizing interface and provide a
scheme for its experimental implementation. A light beam passing through such
an interface undergoes a shift resembling the original geometric SHEL in a
tilted reference frame. This displacement is generated at the polarizer and its
occurrence does not depend on the properties of the detection system. We give
explicit results for this novel type of geometric SHEL and show that at grazing
incidence this effect amounts to a displacement of multiple wavelengths, a
shift larger than the one introduced by Goos-H\"anchen and Imbert-Fedorov
effects.Comment: 6 pages, 4 figure
Spin-based all-optical quantum computation with quantum dots: understanding and suppressing decoherence
We present an all-optical implementation of quantum computation using
semiconductor quantum dots. Quantum memory is represented by the spin of an
excess electron stored in each dot. Two-qubit gates are realized by switching
on trion-trion interactions between different dots. State selectivity is
achieved via conditional laser excitation exploiting Pauli exclusion principle.
Read-out is performed via a quantum-jump technique. We analyze the effect on
our scheme's performance of the main imperfections present in real quantum
dots: exciton decay, hole mixing and phonon decoherence. We introduce an
adiabatic gate procedure that allows one to circumvent these effects, and
evaluate quantitatively its fidelity
A theoretical framework and research agenda for studying team attributions in sport
The attributions made for group outcomes have attracted a great deal of interest in recent years. In this article we bring together much of the current research on attribution theory in sport and outline a new conceptual framework and research agenda for investigating the attributions of team members. The proposed framework draws on multiple conceptual approaches including models of attribution, group dynamics and stress responses to provide a detailed hypothetical description of athletes' physiological, cognitive and affective responses to group competition. In describing this model we outline important antecedents of team attributions before hypothesising how attributions can impact hormonal and cardiovascular responses of athletes, together with cognitive (goals, choices, expectations), affective (self-esteem, emotions), and behavioural (approach-avoidance actions) responses of groups and group members. We conclude by outlining important methodological considerations and implications for structured context specific attribution-based interventions
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