3,335 research outputs found
Retrospective Analysis of Clinical and Cost Outcomes Associated with Methicillin-Resistant Staphylococcus aureus Complicated Skin and Skin Structure Infections Treated with Daptomycin, Vancomycin, or Linezolid
Objective. The objective of this analysis was to compare clinical and cost outcomes associated with patients who had suspected or documented methicillin-resistant Staphylococcus aureus (MRSA) infections treated with daptomycin, vancomycin, or linezolid in complicated skin and skin structure infections (cSSSIs). Design. This was a retrospective analysis conducted from February to June of 2007. Appropriate data was collected, collated, and subsequently evaluated with the purpose of quantifying length of stay, antibiotic therapy duration, clinical cure rates, adverse drug events, and cost of hospitalization. Results. All 82 patients included in the analysis experienced clinical cure. The duration of antibiotic therapy was similar among the three groups yet the length of hospitalization was slightly shorter in the daptomycin group. Conclusions. The incidence of resistant staphylococcal infections is increasing; therefore, judicious use of MRSA active agents is paramount. Future studies are necessary to determine if MRSA treatment options can be stratified based on the severity of the infectious process
Evaluating the impact of a longitudinal patient case on the development of professionalism and professional identity
This article explores the student outcomes of a progressive case on the development of professional identity and professionalism within first-year student pharmacists
Nonequilibrium dynamics of vortex arrest in a finite-temperature Bose-Einstein condensate
We perform finite-temperature dynamical simulations of the arrest of a
rotating Bose-Einstein condensate by a fixed trap anisotropy, using a
Hamiltonian classical-field method. We consider a quasi-two-dimensional
condensate containing a single vortex in equilibrium with a rotating thermal
cloud. Introducing an elliptical deformation of the trapping potential leads to
the loss of angular momentum from the system. We identify the condensate and
the complementary thermal component of the nonequilibrium field, and compare
the evolution of their angular momenta and angular velocities. By varying the
trap anisotropy we alter the relative efficiencies of the vortex-cloud and
cloud-trap coupling. For strong trap anisotropies the angular momentum of the
thermal cloud may be entirely depleted before the vortex begins to decay. For
weak trap anisotropies, the thermal cloud exhibits a long-lived steady state in
which it rotates at an intermediate angular velocity.Comment: 10 pages, 6 figures. v2: Minor changes in response to referee's
comments. To appear in PR
Quantum state of two trapped Bose-Einstein condensates with a Josephson coupling
We consider the precise quantum state of two trapped, coupled Bose Einstein
condensates in the two-mode approximation. We seek a representation of the
state in terms of a Wigner-like distribution on the two-mode Bloch sphere. The
problem is solved using a self-consistent rotation of the unknown state to the
south pole of the sphere. The two-mode Hamiltonian is projected onto the
harmonic oscillator phase plane, where it can be solved by standard techniques.
Our results show how the number of atoms in each trap and the squeezing in the
number difference depend on the physical parameters. Considering negative
scattering lengths, we show that there is a regime of squeezing in the relative
phase of the condensates which occurs for weaker interactions than the
superposition states found by Cirac et al% (quant-ph/9706034, 13 June 1997).
The phase squeezing is also apparent in mildly asymmetric trap configurations.Comment: 26 pages, 11 figure
Characteristics of Two-Dimensional Quantum Turbulence in a Compressible Superfluid
Under suitable forcing a fluid exhibits turbulence, with characteristics
strongly affected by the fluid's confining geometry. Here we study
two-dimensional quantum turbulence in a highly oblate Bose-Einstein condensate
in an annular trap. As a compressible quantum fluid, this system affords a rich
phenomenology, allowing coupling between vortex and acoustic energy.
Small-scale stirring generates an experimentally observed disordered vortex
distribution that evolves into large-scale flow in the form of a persistent
current. Numerical simulation of the experiment reveals additional
characteristics of two-dimensional quantum turbulence: spontaneous clustering
of same-circulation vortices, and an incompressible energy spectrum with
dependence for low wavenumbers and dependence for high
.Comment: 7 pages, 7 figures. Reference [29] updated for v
Energies and collapse times of symmetric and symmetry-breaking states of finite systems with a U(1) symmetry
We study quantum systems of volume V, which will exhibit the breaking of a
U(1) symmetry in the limit of V \to \infty, when V is large but finite. We
estimate the energy difference between the `symmetric ground state' (SGS),
which is the lowest-energy state that does not breaks the symmetry, and a `pure
phase vacuum' (PPV), which approaches a symmetry-breaking vacuum as V \to
\infty. Under some natural postulates on the energy of the SGS, it is shown
that PPVs always have a higher energy than the SGS, and we derive a lower bound
of the excess energy. We argue that the lower bound is O(V^0), which becomes
much larger than the excitation energies of low-lying excited states for a
large V. We also discuss the collapse time of PPVs for interacting many bosons.
It is shown that the wave function collapses in a microscopic time scale,
because PPVs are not energy eigenstates. We show, however, that for PPVs the
expectation value of any observable, which is a finite polynomial of boson
operators and their derivatives, does not collapse for a macroscopic time
scale. In this sense, the collapse time of PPVs is macroscopically long.Comment: In the revised manuscript, Eq. (22), Ref. [8], and Notes [13], [15]
and [17] have been adde
C-Field Methods for Non-Equilibrium Bose Gases
We review c-field methods for simulating the non-equilibrium dynamics of
degenerate Bose gases beyond the mean-field Gross-Pitaevskii approximation. We
describe three separate approaches that utilise similar numerical methods, but
have distinct regimes of validity. Systems at finite temperature can be treated
with either the closed-system projected Gross-Pitaevskii equation (PGPE), or
the open-system stochastic projected Gross-Pitaevskii equation (SPGPE). These
are both applicable in quantum degenerate regimes in which thermal fluctuations
are significant. At low or zero temperature, the truncated Wigner projected
Gross-Pitaevskii equation (TWPGPE) allows for the simulation of systems in
which spontaneous collision processes seeded by quantum fluctuations are
important. We describe the regimes of validity of each of these methods, and
discuss their relationships to one another, and to other simulation techniques
for the dynamics of Bose gases. The utility of the SPGPE formalism in modelling
non-equilibrium Bose gases is illustrated by its application to the dynamics of
spontaneous vortex formation in the growth of a Bose-Einstein condensate.Comment: 7 pages, 1 figure. Unedited version of chapter to appear in Quantum
Gases: Finite Temperature and Non-Equilibrium Dynamics (Vol. 1 Cold Atoms
Series). N.P. Proukakis, S.A. Gardiner, M.J. Davis and M.H. Szymanska, eds.
Imperial College Press, London (in press). See
http://www.icpress.co.uk/physics/p817.html v2: Added arXiv cross-reference
Quantum Dynamics of Three Coupled Atomic Bose-Einstein Condensates
The simplest model of three coupled Bose-Einstein Condensates (BEC) is
investigated using a group theoretical method. The stationary solutions are
determined using the SU(3) group under the mean field approximation. This
semiclassical analysis using the system symmetries shows a transition in the
dynamics of the system from self trapping to delocalization at a critical value
for the coupling between the condensates. The global dynamics are investigated
by examination of the stable points and our analysis shows the structure of the
stable points depends on the ratio of the condensate coupling to the
particle-particle interaction, undergoes bifurcations as this ratio is varied.
This semiclassical model is compared to a full quantum treatment, which also
displays the dynamical transition. The quantum case has collapse and revival
sequences superposed on the semiclassical dynamics reflecting the underlying
discreteness of the spectrum. Non-zero circular current states are also
demonstrated as one of the higher dimensional effects displayed in this system.Comment: Accepted to PR
Microbial dynamics in a High Arctic glacier forefield: A combined field, laboratory, and modelling approach
Modelling the development of soils in glacier forefields is necessary in order to assess how microbial and geochemical processes interact and shape soil development in response to glacier retreat. Furthermore, such models can help us predict microbial growth and the fate of Arctic soils in an increasingly ice-free future. Here, for the first time, we combined field sampling with laboratory analyses and numerical modelling to investigate microbial community dynamics in oligotrophic proglacial soils in Svalbard. We measured low bacterial growth rates and growth efficiencies (relative to estimates from Alpine glacier forefields) and high sensitivity of bacterial growth rates to soil temperature (relative to temperate soils). We used these laboratory measurements to inform parameter values in a new numerical model and significantly refined predictions of microbial and biogeochemical dynamics of soil development over a period of roughly 120 years. The model predicted the observed accumulation of autotrophic and heterotrophic biomass. Genomic data indicated that initial microbial communities were dominated by bacteria derived from the glacial environment, whereas older soils hosted a mixed community of autotrophic and heterotrophic bacteria. This finding was simulated by the numerical model, which showed that active microbial communities play key roles in fixing and recycling carbon and nutrients. We also demonstrated the role of allochthonous carbon and microbial necromass in sustaining a pool of organic material, despite high heterotrophic activity in older soils. This combined field, laboratory, and modelling approach demonstrates the value of integrated model-data studies to understand and quantify the functioning of the microbial community in an emerging High Arctic soil ecosystem
Measurements of Relative Phase in Binary Mixtures of Bose-Einstein Condensates
We have measured the relative phase of two Bose-Einstein condensates (BEC)
using a time-domain separated-oscillatory-field condensate interferometer. A
single two-photon coupling pulse prepares the double condensate system with a
well-defined relative phase; at a later time, a second pulse reads out the
phase difference accumulated between the two condensates. We find that the
accumulated phase difference reproduces from realization to realization of the
experiment, even after the individual components have spatially separated and
their relative center-of-mass motion has damped.Comment: 12 pages, 3 figure
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