447 research outputs found
Conceptual knowledge acquisition in biomedicine: A methodological review
AbstractThe use of conceptual knowledge collections or structures within the biomedical domain is pervasive, spanning a variety of applications including controlled terminologies, semantic networks, ontologies, and database schemas. A number of theoretical constructs and practical methods or techniques support the development and evaluation of conceptual knowledge collections. This review will provide an overview of the current state of knowledge concerning conceptual knowledge acquisition, drawing from multiple contributing academic disciplines such as biomedicine, computer science, cognitive science, education, linguistics, semiotics, and psychology. In addition, multiple taxonomic approaches to the description and selection of conceptual knowledge acquisition and evaluation techniques will be proposed in order to partially address the apparent fragmentation of the current literature concerning this domain
A comparison of statistical machine learning methods in heartbeat detection and classification
In health care, patients with heart problems require quick responsiveness in a clinical setting or in the operating theatre. Towards that end, automated classification of heartbeats is vital as some heartbeat irregularities are time consuming to detect. Therefore, analysis of electro-cardiogram (ECG) signals is an active area of research. The methods proposed in the literature depend on the structure of a heartbeat cycle. In this paper, we use interval and amplitude based features together with a few samples from the ECG signal as a feature vector. We studied a variety of classification algorithms focused especially on a type of arrhythmia known as the ventricular ectopic fibrillation (VEB). We compare the performance of the classifiers against algorithms proposed in the literature and make recommendations regarding features, sampling rate, and choice of the classifier to apply in a real-time clinical setting. The extensive study is based on the MIT-BIH arrhythmia database. Our main contribution is the evaluation of existing classifiers over a range sampling rates, recommendation of a detection methodology to employ in a practical setting, and extend the notion of a mixture of experts to a larger class of algorithms
Extreme Ultra-Violet Spectroscopy of the Lower Solar Atmosphere During Solar Flares
The extreme ultraviolet portion of the solar spectrum contains a wealth of
diagnostic tools for probing the lower solar atmosphere in response to an
injection of energy, particularly during the impulsive phase of solar flares.
These include temperature and density sensitive line ratios, Doppler shifted
emission lines and nonthermal broadening, abundance measurements, differential
emission measure profiles, and continuum temperatures and energetics, among
others. In this paper I shall review some of the advances made in recent years
using these techniques, focusing primarily on studies that have utilized data
from Hinode/EIS and SDO/EVE, while also providing some historical background
and a summary of future spectroscopic instrumentation.Comment: 34 pages, 8 figures. Submitted to Solar Physics as part of the
Topical Issue on Solar and Stellar Flare
Pattern selection in a lattice of pulse-coupled oscillators
We study spatio-temporal pattern formation in a ring of N oscillators with
inhibitory unidirectional pulselike interactions. The attractors of the
dynamics are limit cycles where each oscillator fires once and only once. Since
some of these limit cycles lead to the same pattern, we introduce the concept
of pattern degeneracy to take it into account. Moreover, we give a qualitative
estimation of the volume of the basin of attraction of each pattern by means of
some probabilistic arguments and pattern degeneracy, and show how are they
modified as we change the value of the coupling strength. In the limit of small
coupling, our estimative formula gives a perfect agreement with numerical
simulations.Comment: 7 pages, 8 figures. To be published in Physical Review
Virtually abelian K\"ahler and projective groups
We characterise the virtually abelian groups which are fundamental groups of
compact K\"ahler manifolds and of smooth projective varieties. We show that a
virtually abelian group is K\"ahler if and only if it is projective. In
particular, this allows to describe the K\"ahler condition for such groups in
terms of integral symplectic representations
Oscillator strengths with pseudopotentials
The time-dependent local-density approximation (TDLDA) is shown to remain
accurate in describing the atomic response of IB elements under the additional
approximation of using pseudopotentials to treat the effects of core electrons.
This extends the work of Zangwill and Soven who showed the utility of the
all-electron TDLDA in the atomic response problem.Comment: 13 pages including 3 Postscript figure
The impact of the oblateness of Regulus on the motion of its companion
The fast spinning B-star Regulus has recently been found to be orbited by a
fainter companion in a close circular path with orbital period P_b = 40.11(2)
d. Being its equatorial radius R_e 32% larger than the polar one R_p, Regulus
possesses a remarkable quadrupole mass moment Q. We investigate the effects of
Q on the orbital period P_b of its companion in order to see if they are
measurable, given the present-day level of accuracy in measuring P_b.
Conversely, we will look for deviations from the third Kepler law, attributed
to the quadrupole mass moment Q of Regulus, to constrain the ratio \gamma=m/M
of the system's masses.Comment: LaTex, 6 pages, 5 figures, 1 table. Accepted by Astrophysics and
Space Scienc
Electromagnetic transitions of the helium atom in superstrong magnetic fields
We investigate the electromagnetic transition probabilities for the helium
atom embedded in a superstrong magnetic field taking into account the finite
nuclear mass. We address the regime \gamma=100-10000 a.u. studying several
excited states for each symmetry, i.e. for the magnetic quantum numbers
0,-1,-2,-3, positive and negative z parity and singlet and triplet symmetry.
The oscillator strengths as a function of the magnetic field, and in particular
the influence of the finite nuclear mass on the oscillator strengths are shown
and analyzed.Comment: 10 pages, 8 figure
A Comparison of Statistical Machine Learning Methods in Heartbeat Detection and Classification
Helium in superstrong magnetic fields
We investigate the helium atom embedded in a superstrong magnetic field
gamma=100-10000 au. All effects due to the finite nuclear mass for vanishing
pseudomomentum are taken into account. The influence and the magnitude of the
different finite mass effects are analyzed and discussed. Within our full
configuration interaction approach calculations are performed for the magnetic
quantum numbers M=0,-1,-2,-3, singlet and triplet states, as well as positive
and negative z parities. Up to six excited states for each symmetry are
studied. With increasing field strength the number of bound states decreases
rapidly and we remain with a comparatively small number of bound states for
gamma=10^4 au within the symmetries investigated here.Comment: 16 pages, including 14 eps figures, submitted to Phys. Rev.
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