194 research outputs found
Management of asymptomatic bacteriuria after kidney transplantation : what is the quality of the evidence behind the Infectious Diseases Society of America guidelines?
Local manifold learning and its link to domain-based physics knowledge
In many reacting flow systems, the thermo-chemical state-space is known or
assumed to evolve close to a low-dimensional manifold (LDM). Various approaches
are available to obtain those manifolds and subsequently express the original
high-dimensional space with fewer parameterizing variables. Principal component
analysis (PCA) is one of the dimensionality reduction methods that can be used
to obtain LDMs. PCA does not make prior assumptions about the parameterizing
variables and retrieves them empirically from the training data. In this paper,
we show that PCA applied in local clusters of data (local PCA) is capable of
detecting the intrinsic parameterization of the thermo-chemical state-space. We
first demonstrate that utilizing three common combustion models of varying
complexity: the Burke-Schumann model, the chemical equilibrium model and the
homogeneous reactor. Parameterization of these models is known a priori which
allows for benchmarking with the local PCA approach. We further extend the
application of local PCA to a more challenging case of a turbulent non-premixed
-heptane/air jet flame for which the parameterization is no longer obvious.
Our results suggest that meaningful parameterization can be obtained also for
more complex datasets. We show that local PCA finds variables that can be
linked to local stoichiometry, reaction progress and soot formation processes
The Trigonometric Rosen-Morse Potential in the Supersymmetric Quantum Mechanics and its Exact Solutions
The analytic solutions of the one-dimensional Schroedinger equation for the
trigonometric Rosen-Morse potential reported in the literature rely upon the
Jacobi polynomials with complex indices and complex arguments. We first draw
attention to the fact that the complex Jacobi polynomials have non-trivial
orthogonality properties which make them uncomfortable for physics
applications. Instead we here solve above equation in terms of real orthogonal
polynomials. The new solutions are used in the construction of the
quantum-mechanic superpotential.Comment: 16 pages 7 figures 1 tabl
Non-intersecting squared Bessel paths and multiple orthogonal polynomials for modified Bessel weights
We study a model of non-intersecting squared Bessel processes in the
confluent case: all paths start at time at the same positive value , remain positive, and are conditioned to end at time at . In
the limit , after appropriate rescaling, the paths fill out a
region in the -plane that we describe explicitly. In particular, the paths
initially stay away from the hard edge at , but at a certain critical
time the smallest paths hit the hard edge and from then on are stuck to
it. For we obtain the usual scaling limits from random matrix
theory, namely the sine, Airy, and Bessel kernels. A key fact is that the
positions of the paths at any time constitute a multiple orthogonal
polynomial ensemble, corresponding to a system of two modified Bessel-type
weights. As a consequence, there is a matrix valued
Riemann-Hilbert problem characterizing this model, that we analyze in the large
limit using the Deift-Zhou steepest descent method. There are some novel
ingredients in the Riemann-Hilbert analysis that are of independent interest.Comment: 59 pages, 11 figure
Cavity-induced coherence effects in spontaneous emission from pre-Selection of polarization
Spontaneous emission can create coherences in a multilevel atom having close
lying levels, subject to the condition that the atomic dipole matrix elements
are non-orthogonal. This condition is rarely met in atomic systems. We report
the possibility of bypassing this condition and thereby creating coherences by
letting the atom with orthogonal dipoles to interact with the vacuum of a
pre-selected polarized cavity mode rather than the free space vacuum. We derive
a master equation for the reduced density operator of a model four level atomic
system, and obtain its analytical solution to describe the interference
effects. We report the quantum beat structure in the populations.Comment: 6 pages in REVTEX multicolumn format, 5 figures, new references
added, journal reference adde
M\"ossbauer Antineutrinos: Recoilless Resonant Emission and Absorption of Electron Antineutrinos
Basic questions concerning phononless resonant capture of monoenergetic
electron antineutrinos (M\"ossbauer antineutrinos) emitted in bound-state
beta-decay in the 3H - 3He system are discussed. It is shown that lattice
expansion and contraction after the transformation of the nucleus will
drastically reduce the probability of phononless transitions and that various
solid-state effects will cause large line broadening. As a possible
alternative, the rare-earth system 163Ho - 163Dy is favoured.
M\"ossbauer-antineutrino experiments could be used to gain new and deep
insights into several basic problems in neutrino physics
A framework for increasing the value of predictive data-driven models by enriching problem domain characterization with novel features
The need to leverage knowledge through data mining has driven enterprises in a demand for more data. However, there is a gap between the availability of data and the application of extracted knowledge for improving decision support. In fact, more data do not necessarily imply better predictive data-driven marketing models, since it is often the case that the problem domain requires a deeper characterization. Aiming at such characterization, we propose a framework drawn on three feature selection strategies, where the goal is to unveil novel features that can effectively increase the value of data by providing a richer characterization of the problem domain. Such strategies involve encompassing context (e.g., social and economic variables), evaluating past history, and disaggregate the main problem into smaller but interesting subproblems. The framework is evaluated through an empirical analysis for a real bank telemarketing application, with the results proving the benefits of such approach, as the area under the receiver operating characteristic curve increased with each stage, improving previous model in terms of predictive performance.The work of P. Cortez was supported by FCT within the Project Scope
UID/CEC/00319/2013. The authors would like to thank the anonymous reviewers
for their helpful comments.info:eu-repo/semantics/publishedVersio
Medicinal herb extracts ameliorate impaired growth performance and intestinal lesion of newborn piglets challenged with the virulent porcine epidemic diarrhea virus
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