974 research outputs found
Visualising high-dimensional Pareto relationships in two-dimensional scatterplots
Copyright © 2013 Springer-Verlag Berlin Heidelberg. The final publication is availablevia the DOI in this recordBook title: Evolutionary Multi-Criterion Optimization7th International Conference on Evolutionary Multi-Criterion Optimization (EMO 2013), Sheffield, UK, March 19-22, 2013The codebase for this paper is available at https://github.com/fieldsend/emo_2013_vizIn this paper two novel methods for projecting high dimensional data into two dimensions for visualisation are introduced, which aim to limit the loss of dominance and Pareto shell relationships between solutions to multi-objective optimisation problems. It has already been shown that, in general, it is impossible to completely preserve the dominance relationship when mapping from a higher to a lower dimension – however, approaches that attempt this projection with minimal loss of dominance information are useful for a number of reasons. (1) They may represent the data to the user of a multi-objective optimisation problem in an intuitive fashion, (2) they may help provide insights into the relationships between solutions which are not immediately apparent through other visualisation methods, and (3) they may offer a useful visual medium for interactive optimisation. We are concerned here with examining (1) and (2), and developing relatively rapid methods to achieve visualisations, rather than generating an entirely new search/optimisation problem which has to be solved to achieve the visualisation– which may prove infeasible in an interactive environment for real time use. Results are presented on randomly generated data, and the search population of an optimiser as it progresses. Structural insights into the evolution of a set-based optimiser that can be derived from this visualisation are also discussed
Earliest hominin cancer: 1.7-million-year- old osteosarcoma from Swartkrans Cave, South Africa
The reported incidence of neoplasia in the extinct human lineage is rare, with only a few confirmed
cases of Middle or Later Pleistocene dates reported. It has generally been assumed that premodern
incidence of neoplastic disease of any kind is rare and limited to benign conditions,
but new fossil evidence suggests otherwise. We here present the earliest identifiable case of
malignant neoplastic disease from an early human ancestor dated to 1.8–1.6 million years old.
The diagnosis has been made possible only by advances in 3D imaging methods as diagnostic
aids. We present a case report based on re-analysis of a hominin metatarsal specimen (SK 7923)
from the cave site of Swartkrans in the Cradle of Humankind, South Africa. The expression
of malignant osteosarcoma in the Swartkrans specimen indicates that whilst the upsurge in
malignancy incidence is correlated with modern lifestyles, there is no reason to suspect that
primary bone tumours would have been any less frequent in ancient specimens. Such tumours
are not related to lifestyle and often occur in younger individuals. As such, malignancy has a
considerable antiquity in the fossil record, as evidenced by this specimen.NCS201
Statistics of Atmospheric Correlations
For a large class of quantum systems the statistical properties of their
spectrum show remarkable agreement with random matrix predictions. Recent
advances show that the scope of random matrix theory is much wider. In this
work, we show that the random matrix approach can be beneficially applied to a
completely different classical domain, namely, to the empirical correlation
matrices obtained from the analysis of the basic atmospheric parameters that
characterise the state of atmosphere. We show that the spectrum of atmospheric
correlation matrices satisfy the random matrix prescription. In particular, the
eigenmodes of the atmospheric empirical correlation matrices that have physical
significance are marked by deviations from the eigenvector distribution.Comment: 8 pages, 9 figs, revtex; To appear in Phys. Rev.
Ultra-High Energy Cosmic Rays from Neutrino Emitting Acceleration Sources?
We demonstrate by numerical flux calculations that neutrino beams producing
the observed highest energy cosmic rays by weak interactions with the relic
neutrino background require a non-uniform distribution of sources. Such sources
have to accelerate protons at least up to 10^{23} eV, have to be opaque to
their primary protons, and should emit the secondary photons unavoidably
produced together with the neutrinos only in the sub-MeV region to avoid
conflict with the diffuse gamma-ray background measured by the EGRET
experiment. Even if such a source class exists, the resulting large
uncertainties in the parameters involved in this scenario does currently not
allow to extract any meaningful information on absolute neutrino masses.Comment: 6 pages, 4 figures, RevTeX styl
Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes
We study the spectra of neutron-rich oxygen isotopes based on chiral two- and
three-nucleon interactions. First, we benchmark our many-body approach by
comparing ground-state energies to coupled-cluster results for the same
two-nucleon interaction, with overall good agreement. We then calculate bound
excited states in 21,22,23O, focusing on the role of three-nucleon forces, in
the standard sd shell and an extended sdf7/2p3/2 valence space. Chiral
three-nucleon forces provide important one- and two-body contributions between
valence neutrons. We find that both these contributions and an extended valence
space are necessary to reproduce key signatures of novel shell evolution, such
as the N = 14 magic number and the low-lying states in 21O and 23O, which are
too compressed with two-nucleon interactions only. For the extended space
calculations, this presents first work based on nuclear forces without
adjustments. Future work is needed and open questions are discussed.Comment: 6 pages, 4 figures, published versio
Linear Responses in Time-dependent Hartree-Fock-Bogoliubov Method with Gogny Interaction
A numerical method to integrate the time-dependent Hartree-Fock Bogoliubov
(TDHFB) equations with Gogny interaction is proposed. The feasibility of the
TDHFB code is illustrated by the conservation of the energy, particle numbers,
and center-of-mass in the small amplitude vibrations of oxygen 20. The TDHFB
code is applied to the isoscalar quadrupole and/or isovector dipole vibrations
in the linear (small amplitude) region in oxygen isotopes (masses A = 18,20,22
and 24), titanium isotopes (A = 44,50,52 and 54), neon isotope (A = 26), and
magnesium isotopes (A = 24 and 34). The isoscalar quadrupole and isovector
dipole strength functions are calculated from the expectation values of the
isoscalar quadrupole and isovector dipole moments.Comment: 10 pages, 13 figure
A Measurement of Time-Averaged Aerosol Optical Depth using Air-Showers Observed in Stereo by HiRes
Air fluorescence measurements of cosmic ray energy must be corrected for
attenuation of the atmosphere. In this paper we show that the air-showers
themselves can yield a measurement of the aerosol attenuation in terms of
optical depth, time-averaged over extended periods. Although the technique
lacks statistical power to make the critical hourly measurements that only
specialized active instruments can achieve, we note the technique does not
depend on absolute calibration of the detector hardware, and requires no
additional equipment beyond the fluorescence detectors that observe the air
showers. This paper describes the technique, and presents results based on
analysis of 1258 air-showers observed in stereo by the High Resolution Fly's
Eye over a four year span.Comment: 7 pages, 3 figures, accepted for publication by Astroparticle Physics
Journa
Search for Global Dipole Enhancements in the HiRes-I Monocular Data above 10^{18.5} eV
Several proposed source models for Ultra-High Energy Cosmic Rays (UHECRs)
consist of dipole distributions oriented towards major astrophysical landmarks
such as the galactic center, M87, or Centaurus A. We use a comparison between
real data and simulated data to show that the HiRes-I monocular data for
energies above 10^{18.5} eV is, in fact, consistent with an isotropic source
model. We then explore methods to quantify our sensitivity to dipole source
models oriented towards the Galactic Center, M87, and Centaurus A.Comment: 17 pages, 31 figure
The clustering of ultra-high energy cosmic rays and their sources
The sky distribution of cosmic rays with energies above the 'GZK cutoff'
holds important clues to their origin. The AGASA data, although consistent with
isotropy, shows evidence for small-angle clustering, and it has been argued
that such clusters are aligned with BL Lacertae objects, implicating these as
sources. It has also been suggested that clusters can arise if the cosmic rays
come from the decays of very massive relic particles in the Galactic halo, due
to the expected clumping of cold dark matter. We examine these claims and show
that both are in fact not justified.Comment: 13 pages, 8 figures, version in press at Phys. Rev.
Ultra-High Energy Neutrino Fluxes and Their Constraints
Applying our recently developed propagation code we review extragalactic
neutrino fluxes above 10^{14} eV in various scenarios and how they are
constrained by current data. We specifically identify scenarios in which the
cosmogenic neutrino flux, produced by pion production of ultra high energy
cosmic rays outside their sources, is considerably higher than the
"Waxman-Bahcall bound". This is easy to achieve for sources with hard injection
spectra and luminosities that were higher in the past. Such fluxes would
significantly increase the chances to detect ultra-high energy neutrinos with
experiments currently under construction or in the proposal stage.Comment: 11 pages, 15 figures, version published in Phys.Rev.
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