857 research outputs found
Ensemble of Example-Dependent Cost-Sensitive Decision Trees
Several real-world classification problems are example-dependent
cost-sensitive in nature, where the costs due to misclassification vary between
examples and not only within classes. However, standard classification methods
do not take these costs into account, and assume a constant cost of
misclassification errors. In previous works, some methods that take into
account the financial costs into the training of different algorithms have been
proposed, with the example-dependent cost-sensitive decision tree algorithm
being the one that gives the highest savings. In this paper we propose a new
framework of ensembles of example-dependent cost-sensitive decision-trees. The
framework consists in creating different example-dependent cost-sensitive
decision trees on random subsamples of the training set, and then combining
them using three different combination approaches. Moreover, we propose two new
cost-sensitive combination approaches; cost-sensitive weighted voting and
cost-sensitive stacking, the latter being based on the cost-sensitive logistic
regression method. Finally, using five different databases, from four
real-world applications: credit card fraud detection, churn modeling, credit
scoring and direct marketing, we evaluate the proposed method against
state-of-the-art example-dependent cost-sensitive techniques, namely,
cost-proportionate sampling, Bayes minimum risk and cost-sensitive decision
trees. The results show that the proposed algorithms have better results for
all databases, in the sense of higher savings.Comment: 13 pages, 6 figures, Submitted for possible publicatio
A survey of cost-sensitive decision tree induction algorithms
The past decade has seen a significant interest on the problem of inducing decision trees that take account of costs of misclassification and costs of acquiring the features used for decision making. This survey identifies over 50 algorithms including approaches that are direct adaptations of accuracy based methods, use genetic algorithms, use anytime methods and utilize boosting and bagging. The survey brings together these different studies and novel approaches to cost-sensitive decision tree learning, provides a useful taxonomy, a historical timeline of how the field has developed and should provide a useful reference point for future research in this field
Cosmology and Astrophysics from Relaxed Galaxy Clusters I: Sample Selection
This is the first in a series of papers studying the astrophysics and
cosmology of massive, dynamically relaxed galaxy clusters. Here we present a
new, automated method for identifying relaxed clusters based on their
morphologies in X-ray imaging data. While broadly similar to others in the
literature, the morphological quantities that we measure are specifically
designed to provide a fair basis for comparison across a range of data quality
and cluster redshifts, to be robust against missing data due to point-source
masks and gaps between detectors, and to avoid strong assumptions about the
cosmological background and cluster masses. Based on three morphological
indicators - Symmetry, Peakiness and Alignment - we develop the SPA criterion
for relaxation. This analysis was applied to a large sample of cluster
observations from the Chandra and ROSAT archives. Of the 361 clusters which
received the SPA treatment, 57 (16 per cent) were subsequently found to be
relaxed according to our criterion. We compare our measurements to similar
estimators in the literature, as well as projected ellipticity and other image
measures, and comment on trends in the relaxed cluster fraction with redshift,
temperature, and survey selection method. Code implementing our morphological
analysis will be made available on the web.Comment: MNRAS, in press. 43 pages in total, of which 17 are tables (please
think twice before printing). 18 figures, 4 tables. Machine-readable tables
will be available from the journal and at the url below; code will be posted
at http://www.slac.stanford.edu/~amantz/work/morph14
Mitochondrial reactive oxygen species are scavenged by Cockayne syndrome B protein in human fibroblasts without nuclear DNA damage
Cockayne syndrome (CS) is a human DNA repair-deficient disease that involves transcription coupled repair (TCR), in which three gene products, Cockayne syndrome A (CSA), Cockayne syndrome B (CSB), and ultraviolet stimulated scaffold protein A (UVSSA) cooperate in relieving RNA polymerase II arrest at damaged sites to permit repair of the template strand. Mutation of any of these three genes results in cells with increased sensitivity to UV light and defective TCR. Mutations in CSA or CSB are associated with severe neurological disease but mutations in UVSSA are for the most part only associated with increased photosensitivity. This difference raises questions about the relevance of TCR to neurological disease in CS. We find that CSB-mutated cells, but not UVSSA-deficient cells, have increased levels of intramitochondrial reactive oxygen species (ROS), especially when mitochondrial complex I is inhibited by rotenone. Increased ROS would result in oxidative damage to mitochondrial proteins, lipids, and DNA. CSB appears to behave as an electron scavenger in the mitochondria whose absence leads to increased oxidative stress. Mitochondrial ROS, however, did not cause detectable nuclear DNA damage even when base excision repair was blocked by an inhibitor of polyADP ribose polymerase. Neurodegeneration in Cockayne syndrome may therefore be associated with ROS-induced damage in the mitochondria, independent of nuclear TCR. An implication of our present results is that mitochondrial dysfunction involving ROS has a major impact on CS-B pathology, whereas nuclear TCR may have a minimal role
Correlations in the (Sub)millimeter Background from ACT × BLAST
We present measurements of the auto- and cross-frequency correlation power spectra of the cosmic (sub)millimeter background at 250, 350, and 500 μm (1200, 860, and 600 GHz) from observations made with the Balloon-borne Large Aperture Submillimeter Telescope (BLAST); and at 1380 and 2030 μm (218 and 148 GHz) from observations made with the Atacama Cosmology Telescope (ACT). The overlapping observations cover 8.6 deg^2 in an area relatively free of Galactic dust near the south ecliptic pole. The ACT bands are sensitive to radiation from the cosmic microwave background, to the Sunyaev-Zel'dovich effect from galaxy clusters, and to emission by radio and dusty star-forming galaxies (DSFGs), while the dominant contribution to the BLAST bands is from DSFGs. We confirm and extend the BLAST analysis of clustering with an independent pipeline and also detect correlations between the ACT and BLAST maps at over 25σ significance, which we interpret as a detection of the DSFGs in the ACT maps. In addition to a Poisson component in the cross-frequency power spectra, we detect a clustered signal at 4σ, and using a model for the DSFG evolution and number counts, we successfully fit all of our spectra with a linear clustering model and a bias that depends only on redshift and not on scale. Finally, the data are compared to, and generally agree with, phenomenological models for the DSFG population. This study demonstrates the constraining power of the cross-frequency correlation technique to constrain models for the DSFGs. Similar analyses with more data will impose tight constraints on future models
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THE SANTA ANA SPECKLED DACE (RHINICHTHYS OSCULUS): PHYLOGEOGRAPHY AND MOLECULAR EVOLUTION OF THE MITOCHONDRIAL DNA CONTROL REGION
The purpose of this genetic study of the Santa Ana Speckled Dace Rhinichthys osculus was three-fold. The first goal was to characterize the molecular structure of the mtDNA control region of R. osculus. An 1143 base-pair region of the mitochondrial DNA genome, which included the complete control region was sequenced for all individuals. Analysis of the sequence data revealed that the molecular structure of the speckled dace control region was similar to the molecular structure described for other vertebrate taxa. The speckled dace control region contains three major domains, which vary in base frequency as well as in the frequency of nucleotide polymorphisms. Domain II was observed to be the most conserved, and Domain I was the most variable domain of the control region, in agreement with studies of other vertebrate control regions. The second goal of this study was to ascertain the phylogeny of R. osculus in Southern California in relation to other speckled dace in California. Seventy-four specimens of R. osculus were collected from five different watersheds located in three geographic regions of California: Southern California, the Central California Coast, and the Eastern Desert of the Owens River valley. Phylogenetic analysis of sequence data revealed that the Santa Ana Speckled Dace is a genetically distinct population from R. osculus inhabiting the Central Coast or Eastern Desert regions, which both differ from the Santa Ana Speckled Dace by a genetic distance of more than 7 percent. The Santa Ana Speckled Dace inhabiting the watersheds of Southern California form a reciprocally monophyletic clade with respect to the Central Coast dace and the Eastern Desert dace, which are sister clades to one another. The third goal of this study was to describe the population genetics of R. osculus in Southern California. Population genetic analysis demonstrated that a high degree of geographic population structure exists for the Speckled Dace in California, with 96% of molecular variance attributable to regional differences through isolation by distance. A high degree of population structure also exists among populations within the Southern California region as well. It was found that 45% of molecular variance in the Santa Ana Speckled Dace is attributable to differences among tributaries. This study finds that the distribution of speckled dace in Southern California best fits a model of population structure by individual tributary, with episodes of localized population bottlenecks followed by sudden population expansion, most likely linked to climatic variation. It is proposed the Santa Ana Speckled Dace constitutes an Evolutionarily Significant Unit (ESU) that qualifies it as a separate subspecies on the basis that it is geographically separated from other populations, genetically distinct from other dace populations due to restricted gene flow, and possesses unique phenotypic characteristics. This information suggests conservation and management strategies for the speckled dace populations which remain in existence in Southern California
Correlations in the (Sub)millimeter background from ACTxBLAST
We present measurements of the auto- and cross-frequency correlation power
spectra of the cosmic (sub)millimeter background at: 250, 350, and 500 um
(1200, 860, and 600 GHz) from observations made with the Balloon-borne Large
Aperture Submillimeter Telescope, BLAST; and at 1380 and 2030 um (218 and 148
GHz) from observations made with the Atacama Cosmology Telescope, ACT. The
overlapping observations cover 8.6 deg^2 in an area relatively free of Galactic
dust near the south ecliptic pole (SEP). The ACT bands are sensitive to
radiation from the CMB, the Sunyaev-Zel'dovich (SZ) effect from galaxy
clusters, and to emission by radio and dusty star-forming galaxies (DSFGs),
while the dominant contribution to the BLAST bands is from DSFGs. We confirm
and extend the BLAST analysis of clustering with an independent pipeline, and
also detect correlations between the ACT and BLAST maps at over 25sigma
significance, which we interpret as a detection of the DSFGs in the ACT maps.
In addition to a Poisson component in the cross-frequency power spectra, we
detect a clustered signal at >4sigma, and using a model for the DSFG evolution
and number counts, we successfully fit all our spectra with a linear clustering
model and a bias that depends only on redshift and not on scale. Finally, the
data are compared to, and generally agree with, phenomenological models for the
DSFG population. This study represents a first of its kind, and demonstrates
the constraining power of the cross-frequency correlation technique to
constrain models for the DSFGs. Similar analyses with more data will impose
tight constraints on future models.Comment: 17 pages, 11 figure
QCD and Light-Front Holography
The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric,
leads to a remarkable one-parameter description of nonperturbative hadron
dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge
spectrum of linear trajectories with the same slope in the leading orbital
angular momentum of hadrons and the radial quantum number . Light-Front
Holography maps the amplitudes which are functions of the fifth dimension
variable of anti-de Sitter space to a corresponding hadron theory quantized
on the light front. The resulting Lorentz-invariant relativistic light-front
wave equations are functions of an invariant impact variable which
measures the separation of the quark and gluonic constituents within the hadron
at equal light-front time. The result is a semi-classical frame-independent
first approximation to the spectra and light-front wavefunctions of meson and
baryon light-quark bound states, which in turn predict the behavior of the pion
and nucleon form factors. The effects of chiral symmetry breaking increase as
one goes toward large interquark separation, consistent with spectroscopic
data, and the hadron eigenstates generally have components with different
orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless
quarks has L=0 and L=1 light-front Fock components with equal probability. The
soft-wall model also predicts the form of the non-perturbative effective
coupling which agrees with the effective coupling extracted
from the Bjorken sum rule. The AdS/QCD model can be systematically improved by
using its complete orthonormal solutions to diagonalize the full QCD
light-front Hamiltonian or by applying the Lippmann-Schwinger method in order
to systematically include the QCD interaction terms. A new perspective on quark
and gluon condensates is also reviewed.Comment: Invited talk, presented by SJB at the 50th Crakow School, Zakopane,
Poland; final version to appear in proceeding
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