6,712 research outputs found
Static and Dynamic Properties of Trapped Fermionic Tonks-Girardeau Gases
We investigate some exact static and dynamic properties of one-dimensional
fermionic Tonks-Girardeau gases in tight de Broglie waveguides with attractive
p-wave interactions induced by a Feshbach resonance. A closed form solution for
the one-body density matrix for harmonic trapping is analyzed in terms of its
natural orbitals, with the surprising result that for odd, but not for even,
numbers of fermions the maximally occupied natural orbital coincides with the
ground harmonic oscillator orbital and has the maximally allowed fermionic
occupancy of unity. The exact dynamics of the trapped gas following turnoff of
the p-wave interactions are explored.Comment: 4 pages, 2 figures, submitted to PR
Theory of spinor Fermi and Bose gases in tight atom waveguides
Divergence-free pseudopotentials for spatially even and odd-wave interactions
in spinor Fermi gases in tight atom waveguides are derived. The Fermi-Bose
mapping method is used to relate the effectively one-dimensional fermionic
many-body problem to that of a spinor Bose gas. Depending on the relative
magnitudes of the even and odd-wave interactions, the N-atom ground state may
have total spin S=0, S=N/2, and possibly also intermediate values, the case
S=N/2 applying near a p-wave Feshbach resonance, where the N-fermion ground
state is space-antisymmetric and spin-symmetric. In this case the fermionic
ground state maps to the spinless bosonic Lieb-Liniger gas. An external
magnetic field with a longitudinal gradient causes a Stern-Gerlach spatial
separation of the corresponding trapped Fermi gas with respect to various
values of .Comment: 4+ pages, 1 figure, revtex4. Submitted to PRA. Minor corrections of
typos and notatio
Coherence properties of the microcavity polariton condensate
A theoretical model is presented which explains the dominant decoherence
process in a microcavity polariton condensate. The mechanism which is invoked
is the effect of self-phase modulation, whereby interactions transform
polariton number fluctuations into random energy variations. The model shows
that the phase coherence decay, g1(t), has a Kubo form, which can be Gaussian
or exponential, depending on whether the number fluctuations are slow or fast.
This fluctuation rate also determines the decay time of the intensity
correlation function, g2(t), so it can be directly determined experimentally.
The model explains recent experimental measurements of a relatively fast
Gaussian decay for g1(t), but also predicts a regime, further above threshold,
where the decay is much slower.Comment: 5 pages, 1 figur
Saddle Points and Stark Ladders: Exact Calculations of Exciton Spectra in Superlattices
A new, exact method for calculating excitonic absorption in superlattices is
described. It is used to obtain high resolution spectra showing the saddle
point exciton feature near the top of the miniband. The evolution of this
feature is followed through a series of structures with increasing miniband
width. The Stark ladder of peaks produced by an axial electric field is
investigated, and it is shown that for weak fields the line shapes are strongly
modified by coupling to continuum states, taking the form of Fano resonances.
The calculated spectra, when suitably broadened, are found to be in good
agreement with experimental results.Comment: 9 pages Revtex v3.0, followed by 4 uuencoded postscript figures,
SISSA-CM-94-00
The Population Biology and Transmission Dynamics of Loa loa
Endemic to Central Africa, loiasis – or African eye worm (caused by the filarial nematode Loa loa) – affects more than 10 million people. Despite causing ocular and systemic symptoms, it has typically been considered a benign condition, only of public health relevance because it impedes mass drug administration-based interventions against onchocerciasis and lymphatic filariasis in co-endemic areas. Recent research has challenged this conception, demonstrating excess mortality associated with high levels of infection, implying that loiasis warrants attention as an intrinsic public health problem. This review summarises available information on the key parasitological, entomological, and epidemiological characteristics of the infection and argues for the mobilisation of resources to control the disease, and the development of a mathematical transmission model to guide deployment of interventions
How can we help novice child protection social workers to see situations like experienced practitioners? A randomised controlled trial evaluation of the ShadowBox™ method using pre-recorded video feedback
Background
Protecting children for abuse and neglect is a complex area of decision-making but frequent staff turnover has meant that many frontline child protection social workers are often relatively inexperienced. The ShadoxBoxTM method is an educational intervention that enables novice practitioners to gain decision-making skills quickly.
Aim:
This study was an RCT evaluation of an educational intervention for novice social workers that used the ShadoxBoxTM method adapted to include pre-recorded video feedback from an expert panel to test whether novice decision making would become more similar to experienced practitioners.
Methods:
The study was an RCT in which participants completed complex scenarios in a computer lab in control and intervention groups. The training method involved participants receiving feedback from highly experienced practitioners at each decision point within the scenarios. The intervention group received pre-recorded video feedback from a panel of highly experienced practitioners while the control group received no feedback.
Participants and Setting
Participants (n=83) were trainee social workers from a London university randomly allocated to control and intervention groups. Data was collected on computer stations using Qualtrics.
Results
Undertaking the scenarios improved both groups but greater improvement was seen in participants who had received video feedback from a panel of experienced practitioners. The results were promising, with participant accuracy increasing by 44% (from 31% to 75%) in the intervention group compared to an increase of 31% (from 32% to 63%) in the control group.
Considerable improvements were noted in both intervention and control groups, which suggest that scenario-based interventions can be a promising educational method as learning is rooted in real life scenarios and participants have the opportunity to reflect upon their decisions.
The qualitative findings are that novice participants make predictable errors, including:
• Making shallow assumptions
• Focusing exclusively on the parents rather than the child.
• Jumping to early conclusions with insufficient information.
Conclusions
• ShadoxBoxTM training appears to be a promising intervention for improving decision making.
• Novices benefitted from having concentrated exposure to complex scenarios focused on assessing risk and making professional judgements.
• When this was augmented by direct feedback from a panel of highly experienced practitioners, these benefits were increased considerably.
• The complexity of the scenarios also exposed the novices to real life pressures rather than the simplified versions used in decision research
Two-dimensional metric and tetrad gravities as constrained second order systems
Using the Gitman-Lyakhovich-Tyutin generalization of the Ostrogradsky method
for analyzing singular systems, we consider the Hamiltonian formulation of
metric and tetrad gravities in two-dimensional Riemannian spacetime treating
them as constrained higher-derivative theories. The algebraic structure of the
Poisson brackets of the constraints and the corresponding gauge transformations
are investigated in both cases.Comment: replaced with revised version published in
Mod.Phys.Lett.A22:17-28,200
Family memories in the home: contrasting physical and digital mementos
We carried out fieldwork to characterise and compare physical and digital mementos in the home. Physical mementos are highly valued, heterogeneous and support different types of recollection. Contrary to expectations, we found physical mementos are not purely representational, and can involve appropriating common objects and more idiosyncratic forms. In contrast, digital mementos were initially perceived as less valuable, although participants later reconsidered this. Digital mementos were somewhat limited in function and expression, largely involving representational photos and videos, and infrequently accessed. We explain these digital limitations and conclude with design guidelines for digital mementos, including better techniques for accessing and integrating these into everyday life, allowing them to acquire the symbolic associations and lasting value that characterise their physical counterparts
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