132 research outputs found
Inferring meta-covariates in classification
This paper develops an alternative method for gene selection that combines model based clustering and binary classification. By averaging the covariates within the clusters obtained from model based clustering, we define “meta-covariates” and use them to build a probit regression model, thereby selecting clusters of similarly behaving genes, aiding interpretation. This simultaneous learning task is accomplished by an EM algorithm that optimises a single likelihood function which rewards good performance at both classification and clustering. We explore the performance of our methodology on a well known leukaemia dataset and use the Gene Ontology to interpret our results
Morphological characteristics of ant assemblages (Hymenoptera: Formicidae) differ among contrasting biomes
The environment is thought to strongly shape the ecology and evolution of species. Similar environments may cause species to look the same or converge upon particular traits. Dissimilar environments can cause species to look different or to diverge in their traits. These ideas have been explored at the single species level or within restricted geographic areas for ants. We ask whether the signature of environmental filtering can be detected within ant faunas at the biogeographic scale. We quantify differences in the morphological traits of ant faunas between two contrasting biomes: a
rainforest in Costa Rica and a desert in Iran. Lists of species from each habitat type were compiled, and measurements
of ten functional traits were taken from scaled images. Body size, relative femur length, and tibia length were significantly
smaller in Costa Rica suggesting species in more complex environments are smaller in response to environmental complexity. Relative eye width was also smaller in Costa Rica, and individuals were lighter in colour. Eye size and body pigmentation showed differences which may be a result of altered foraging patterns or protection against UV-B irradiance. The Costa Rican fauna also had a much wider trait space (higher functional richness), and Iranian species occupied a narrow range in terms of mandible and leg size suggesting species invest less in foraging specialism in unproductive environments. Significant differences in morphological traits and their degree of overlap can therefore be
observed in ant faunas occupying contrasting biomes. We suggest that this is due to the environment influencing the trait composition of these faunas at biogeographic scales
Hydrodynamics of Spatially Ordered Superfluids
We derive the hydrodynamic equations for the supersolid and superhexatic
phases of a neutral two-dimensional Bose fluid. We find, assuming that the
normal part of the fluid is clamped to an underlying substrate, that both
phases can sustain third-sound modes and that in the supersolid phase there are
additional modes due to the superfluid motion of point defects (vacancies and
interstitials).Comment: 24 pages of ReVTeX and 7 uuencoded figures. Submitted for publication
in Phys. Rev.
The Hamiltonian limit of (3+1)D SU(3) lattice gauge theory on anisotropic lattices
The extreme anisotropic limit of Euclidean SU(3) lattice gauge theory is
examined to extract the Hamiltonian limit, using standard path integral Monte
Carlo (PIMC) methods. We examine the mean plaquette and string tension and
compare them to results obtained within the Hamiltonian framework of Kogut and
Susskind. The results are a significant improvement upon previous Hamiltonian
estimates, despite the extrapolation procedure necessary to extract
observables. We conclude that the PIMC method is a reliable method of obtaining
results for the Hamiltonian version of the theory. Our results also clearly
demonstrate the universality between the Hamiltonian and Euclidean formulations
of lattice gauge theory. It is particularly important to take into account the
renormalization of both the anisotropy, and the Euclidean coupling ,
in obtaining these results.Comment: 10 pages, 11 figure
Early- Onset Stroke and Vasculopathy Associated with Mutations in ADA2
Adenosine deaminase 2 (ADA2) is an enzyme involved in purine metabolism and a growth factor that influences the development of endothelial cells and leukocytes. This study shows that defects in ADA2 cause recurrent fevers, vascular pathologic features, and mild immunodeficiency. Patients with autoinflammatory disease sometimes present with clinical findings that encompass multiple organ systems.(1) Three unrelated children presented to the National Institutes of Health (NIH) Clinical Center with intermittent fevers, recurrent lacunar strokes, elevated levels of acute-phase reactants, livedoid rash, hepatosplenomegaly, and hypogammaglobulinemia. Collectively, these findings do not easily fit with any of the known inherited autoinflammatory diseases. Hereditary or acquired vascular disorders can have protean manifestations yet be caused by mutations in a single gene. Diseases such as the Aicardi-Goutieres syndrome,(2),(3) polypoidal choroidal vasculopathy,(4) sickle cell anemia,(5) livedoid vasculopathy,(6) and the small-vessel vasculitides(7),(8) are examples of systemic ...</p
b-Jet Identification in the D0 Experiment
Algorithms distinguishing jets originating from b quarks from other jet
flavors are important tools in the physics program of the D0 experiment at the
Fermilab Tevatron p-pbar collider. This article describes the methods that have
been used to identify b-quark jets, exploiting in particular the long lifetimes
of b-flavored hadrons, and the calibration of the performance of these
algorithms based on collider data.Comment: submitted to Nuclear Instruments and Methods in Physics Research
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