15,962 research outputs found
Floquet topological transitions in extended Kane-Mele models with disorder
In this work we use Floquet theory to theoretically study the influence of
circularly polarized light on disordered two-dimensional models exhibiting
topological transitions. We find circularly polarized light can induce a
topological transition in extended Kane-Mele models that include additional
hopping terms and on-site disorder. The topological transitions are understood
from the Floquet-Bloch band structure of the clean system at high symmetry
points in the first Brillouin zone. The light modifies the equilibrium band
structure of the clean system in such a way that the smallest gap in the
Brillouin zone can be shifted from the points to the points, the
point, or even other lower symmetry points. The movement of the
minimal gap point through the Brillouin zone as a function of laser parameters
is explained in the high frequency regime through the Magnus expansion. In the
disordered model, we compute the Bott index to reveal topological phases and
transitions. The disorder can induce transitions from topologically non-trivial
states to trivial states or vice versa, both examples of Floquet topological
Anderson transitions. As a result of the movement of the minimal gap point
through the Brillouin zone as a function of laser parameters, the nature of the
topological phases and transitions is laser-parameter dependent--a contrasting
behavior to the Kane-Mele model.Comment: 10 pages, 7 figure
Community learning and development training for professionals engaged in community regeneration and community planning
The study was commissioned by the Scottish Executive Development Department to identify training needs and current provision of community learning and development (CLD) training for a range of professionals (other than those formally qualified in CLD) who are engaged in community regeneration and community planning (Local Government in Scotland Act 2003). It was one of a series of studies emanating from the Scottish Executive response to the review: âEmpowered to Practice â the future of community learning and development training in Scotlandâ. One of the themes of the report taken up by the Scottish Executive was the need for; âwider opportunities for joint training with other disciplines such as teachers, librarians, college lecturers, health workers and social workersâ
A flow equation approach to periodically driven quantum systems
We present a theoretical method to generate a highly accurate {\em
time-independent} Hamiltonian governing the finite-time behavior of a
time-periodic system. The method exploits infinitesimal unitary transformation
steps, from which renormalization group-like flow equations are derived to
produce the effective Hamiltonian. Our tractable method has a range of validity
reaching into frequency regimes that are usually inaccessible via high
frequency expansions in the parameter , where is the
upper limit for the strength of local interactions. We demonstrate our approach
on both interacting and non-interacting many-body Hamiltonians where it offers
an improvement over the more well-known Magnus expansion and other high
frequency expansions. For the interacting models, we compare our approximate
results to those found via exact diagonalization. While the approximation
generally performs better globally than other high frequency approximations,
the improvement is especially pronounced in the regime of lower frequencies and
strong external driving. This regime is of special interest because of its
proximity to the resonant regime where the effect of a periodic drive is the
most dramatic. Our results open a new route towards identifying novel
non-equilibrium regimes and behaviors in driven quantum many-particle systems.Comment: 25 pages, 14 figure
An investigation of pulsar searching techniques with the Fast Folding Algorithm
Here we present an in-depth study of the behaviour of the Fast Folding
Algorithm, an alternative pulsar searching technique to the Fast Fourier
Transform. Weaknesses in the Fast Fourier Transform, including a susceptibility
to red noise, leave it insensitive to pulsars with long rotational periods (P >
1 s). This sensitivity gap has the potential to bias our understanding of the
period distribution of the pulsar population. The Fast Folding Algorithm, a
time-domain based pulsar searching technique, has the potential to overcome
some of these biases. Modern distributed-computing frameworks now allow for the
application of this algorithm to all-sky blind pulsar surveys for the first
time. However, many aspects of the behaviour of this search technique remain
poorly understood, including its responsiveness to variations in pulse shape
and the presence of red noise. Using a custom CPU-based implementation of the
Fast Folding Algorithm, ffancy, we have conducted an in-depth study into the
behaviour of the Fast Folding Algorithm in both an ideal, white noise regime as
well as a trial on observational data from the HTRU-S Low Latitude pulsar
survey, including a comparison to the behaviour of the Fast Fourier Transform.
We are able to both confirm and expand upon earlier studies that demonstrate
the ability of the Fast Folding Algorithm to outperform the Fast Fourier
Transform under ideal white noise conditions, and demonstrate a significant
improvement in sensitivity to long-period pulsars in real observational data
through the use of the Fast Folding Algorithm.Comment: 19 pages, 15 figures, 3 table
Ruling out a higher spin field solution to the cosmological constant problem
We consider the modification of Newton's gravity law in Dolgov's higher spin
models designed to compensate the cosmological constant. We find that the
effective Planck mass is unacceptably large in these models. We also point out
that the properties of gravitational waves are entirely different in these
models as compared to general relativity.Comment: 7 pages, LaTe
Risk factors for failure of outpatient parenteral antibiotic therapy (OPAT) in infective endocarditis
Objectives:
To identify risk factors for failure of outpatient antibiotic therapy (OPAT) in infective endocarditis (IE).
Patients and methods:
We identified IE cases managed at a single centre over 12 years from a prospectively maintained database. âOPAT failureâ was defined as unplanned readmission or antibiotic switch due to adverse drug reaction or antibiotic resistance. We analysed patient and disease-related risk factors for OPAT failure by univariate and multivariate logistic regression. We also retrospectively collected follow-up data on adverse disease outcome (defined as IE-related death or relapse) and performed KaplanâMeier survival analysis up to 36 months following OPAT.
Results:
We identified 80 episodes of OPAT in IE. Failure occurred in 25/80 episodes (31.3%). On multivariate analysis, cardiac or renal failure [pooled OR 7.39 (95% CI 1.84â29.66), Pâ=â0.005] and teicoplanin therapy [OR 8.69 (95% CI 2.01â37.47), Pâ=â0.004] were independently associated with increased OPAT failure. OPAT failure with teicoplanin occurred despite therapeutic plasma levels. OPAT failure predicted adverse disease outcome up to 36 months (Pâ=â0.016 log-rank test).
Conclusions:
These data caution against selecting patients with endocarditis for OPAT in the presence of cardiac or renal failure and suggest teicoplanin therapy may be associated with suboptimal OPAT outcomes. Alternative regimens to teicoplanin in the OPAT setting should be further investigated
Visualisation Tools for Multi-Perspective, Cross-Sector, Long-Term Infrastructure Performance Evaluation
Across different infrastructure sectors there are systems that help to monitor the current and near-future operation
and performance of a particular system. Whilst Supervisory Control and Data Acquisition (SCADA) systems are critical
to maintaining acceptable levels of functionality, they do not provide insights over the longer timescales across which
strategic investment decisions play out. To understand how individual or multiple, interdependent, infrastructure
sectors perform over longer timescales, capacity/demand modelling is required. However, the outputs of such
models are often a complex high-dimensionality result-set, and this complexity is further compounded when crosssector
evaluation is required. To maximise utility of such models, tools are required that can process and present
key outputs. In this paper we describe the development of prototype tools for infrastructure performance evaluation
in relation to different strategic decisions and the complex outputs generated from capacity and demand models of
five infrastructure sectors (energy, water, waste water, solid waste, transport) investigated within the UK Infrastructure
Transitions Research Consortium (ITRC). By constructing tools that expose various dimensions of the model outputs,
a user is able to take greater control over the knowledge discovery process
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