202 research outputs found
Morphological Classification of Galaxies by Shapelet Decomposition in the Sloan Digital Sky Survey II: Multiwavelength Classification
We describe the application of the `shapelet' linear decomposition of galaxy
images to multi-wavelength morphological classification using the
and -band images of 1519 galaxies from the Sloan Digital Sky Survey. We
utilize elliptical shapelets to remove to first-order the effect of inclination
on morphology. After decomposing the galaxies we perform a principal component
analysis on the shapelet coefficients to reduce the dimensionality of the
spectral morphological parameter space. We give a description of each of the
first ten principal component's contribution to a galaxy's spectral morphology.
We find that galaxies of different broad Hubble type separate cleanly in the
principal component space. We apply a mixture of Gaussians model to the
2-dimensional space spanned by the first two principal components and use the
results as a basis for classification. Using the mixture model, we separate
galaxies into three classes and give a description of each class's physical and
morphological properties. We find that the two dominant mixture model classes
correspond to early and late type galaxies, respectively. The third class has,
on average, a blue, extended core surrounded by a faint red halo, and typically
exhibits some asymmetry. We compare our method to a simple cut on color
and find the shapelet method to be superior in separating galaxies.
Furthermore, we find evidence that the decision boundary may not be
optimal for separation between early and late type galaxies, and suggest that
the optimal cut may be .Comment: 42 pages, 18 figs, revised version in press at AJ. Some modification
to the technique, more discussion, addition/deletion/modification of several
figures, color figures have been added. A high resolution version may be
obtained at
http://bllac.as.arizona.edu/~bkelly/shapelets/shapelets_ugriz.ps.g
A 2dF spectroscopic study of globular clusters in NGC 5128: Probing the formation history of the nearest giant Elliptical
We have performed a spectroscopic study of globular clusters (GCs) in the
giant elliptical NGC 5128 using the 2dF facility at the Anglo-Australian
telescope. We obtained integrated optical spectra for a total of 254 GCs, 79 of
which are newly confirmed on the basis of their radial velocities and spectra.
In addition, we obtained an integrated spectrum of the galaxy starlight along
the southern major axis. We derive an empirical metallicity distribution
function (MDF) for 207 GCs (~14 of the estimated total GC system) based upon
Milky Way GCs. This MDF is multimodal at high statistical significance with
peaks at [Z/H]~-1.3 and -0.5. A comparison between the GC MDF and that of the
stellar halo at 20 kpc (~4 Reff) reveals close coincidence at the metal-rich
ends of the distributions. However, an inner 8 kpc stellar MDF shows a clear
excess of metal-rich stars when compared to the GCs. We compare a higher S/N
subsample (147 GCs) with two stellar population models which include non-solar
abundance ratio corrections. The vast majority of our sample (~90%) appears
old, with ages similar to the Milky Way GC system. There is evidence for a
population of intermediate-age (~4-8 Gy) GCs (<15% of the sample) which are on
average more metal-rich than the old GCs. We also identify at least one younger
cluster (~1-2 Gy) in the central regions of the galaxy. Our observations are
consistent with a picture where NGC 5128 has undergone at least two mergers
and/or interactions involving star formation and limited GC formation since
z=1, however the effect of non-canonical hot stellar populations on the
integrated spectra of GCs remains an outstanding uncertainty in our GC age
estimates.Comment: 17 figures, some long table
Involving older people in the preparedness, response, and recovery phases in humanitarian emergencies: a theoretical framework on ageism, epistemic injustice, and participation
Humanitarian emergencies disproportionally affect older people. Although defining an older person by an age range can help alert us to emerging or changing needs and potential vulnerabilities during humanitarian emergencies, ageing is not necessarily synonymous with increasing vulnerability, and individual variations exist due to the heterogeneity of older people. In general, reduced access to safety, health services, clean water, and appropriate food puts older people at increased risk of poor health outcomes during humanitarian emergencies, including disability, injury, malnutrition, and mental health issues. The theoretical framework presented in this Personal View explains how ageism, further compounded by intersecting oppression, leads to the exclusion of older people from the preparedness, response, and recovery phases of humanitarian emergencies. The exclusion of older people is discriminatory, violates core humanitarian and bioethical principles, and leads to an epistemic injustice. We suggest that humanitarian actors implement participatory approaches with older people in humanitarian contexts. Through these approaches, solutions will be identified by and together with older people, leading to community-driven and context-appropriate ways to include the needs and strengths of older people in the preparedness, response, and recovery phases of humanitarian emergencies
Characterizing genomic alterations in cancer by complementary functional associations.
Systematic efforts to sequence the cancer genome have identified large numbers of mutations and copy number alterations in human cancers. However, elucidating the functional consequences of these variants, and their interactions to drive or maintain oncogenic states, remains a challenge in cancer research. We developed REVEALER, a computational method that identifies combinations of mutually exclusive genomic alterations correlated with functional phenotypes, such as the activation or gene dependency of oncogenic pathways or sensitivity to a drug treatment. We used REVEALER to uncover complementary genomic alterations associated with the transcriptional activation of β-catenin and NRF2, MEK-inhibitor sensitivity, and KRAS dependency. REVEALER successfully identified both known and new associations, demonstrating the power of combining functional profiles with extensive characterization of genomic alterations in cancer genomes
Contingent Kernel Density Estimation
Kernel density estimation is a widely used method for estimating a distribution based on a sample of points drawn from that distribution. Generally, in practice some form of error contaminates the sample of observed points. Such error can be the result of imprecise measurements or observation bias. Often this error is negligible and may be disregarded in analysis. In cases where the error is non-negligible, estimation methods should be adjusted to reduce resulting bias. Several modifications of kernel density estimation have been developed to address specific forms of errors. One form of error that has not yet been addressed is the case where observations are nominally placed at the centers of areas from which the points are assumed to have been drawn, where these areas are of varying sizes. In this scenario, the bias arises because the size of the error can vary among points and some subset of points can be known to have smaller error than another subset or the form of the error may change among points. This paper proposes a “contingent kernel density estimation” technique to address this form of error. This new technique adjusts the standard kernel on a point-by-point basis in an adaptive response to changing structure and magnitude of error. In this paper, equations for our contingent kernel technique are derived, the technique is validated using numerical simulations, and an example using the geographic locations of social networking users is worked to demonstrate the utility of the method
Markov models for ocular fixation locations in the presence and absence of colour
In response to the 2015 Royal Statistical Society's statistical analytics challenge, we propose to model the fixation locations of the human eye when observing a still image by a Markov point process in R. Our approach is data driven using -means clustering of the fixation locations to identify distinct salient regions of the image, which in turn correspond to the states of our Markov chain. Bayes factors are computed as the model selection criterion to determine the number of clusters. Furthermore, we demonstrate that the behaviour of the human eye differs from this model when colour information is removed from the given image.This work was supported by UK Engineering and Physical Sciences Research Council grant EP/H023348/1 for the University of Cambridge Centre for Doctoral Training, Cambridge Centre for Analysis
Brood parasitism, provisioning rates and breeding phenology of male and female magpie hosts
Parental care is a costly behaviour that raises the prospects of offspring survival. In
species with biparental care these costs are shared by both parents, although there
may be a conflict regarding the relative investment of each sex. Avian brood parasites
leave all the costs of rearing offspring to their hosts. The magnitude of these costs
and their consequences on the relative role of both sexes in parental care and future
reproduction remain mostly unknown. Here, we investigate whether provisioning rate
of nestlings by magpie hosts Pica pica differs between broods parasitized by the great
spotted cuckoo Clamator glandarius and non-parasitized broods, and whether the relative
contribution of each sex to provisioning is affected by parasitism. Furthermore, we
explore the effect of parasitism on magpie’s future reproduction. We found that provisioning
rate was similar in parasitized and non-parasitized broods, and that the relative
contribution of males and females was also similar, irrespectively of the parasitism
status. However, rearing parasitic offspring seems to have a negative long-term effect
on magpie’s breeding phenology in the following breeding season. Our results suggest
that, although brood parasitism by great spotted cuckoos does not seem to influence
the relative contribution of both sexes to parental care, it may entail long-term extra
costs in terms of breeding delay for magpies.Junta de Andalucía (Proyecto P06-RNM-01862)Ministerio de Ciencia (proyecto CGL2014-55362-P)Programa Juan de la Cierva –Incorporación (IJC2018-036411-I)German Research Foundation (SFB TRR 212 (NC3) – Projectos n. 316099922 y 396782608
The LabelHash algorithm for substructure matching
Background: There is an increasing number of proteins with known structure but unknown function. Determining their function would have a significant impact on understanding diseases and designing new therapeutics. However, experimental protein function determination is expensive and very time-consuming. Computational methods can facilitate function determination by identifying proteins that have high structural and chemical similarity. Results: We present LabelHash, a novel algorithm for matching substructural motifs to large collections of protein structures. The algorithm consists of two phases. In the first phase the proteins are preprocessed in a fashion that allows for instant lookup of partial matches to any motif. In the second phase, partial matches for a given motif are expanded to complete matches. The general applicability of the algorithm is demonstrated with three different case studies. First, we show that we can accurately identify members of the enolase superfamily with a single motif. Next, we demonstrate how LabelHash can complement SOIPPA, an algorithm for motif identification and pairwise substructure alignment. Finally, a large collection of Catalytic Site Atlas motifs is used to benchmark the performance of the algorithm. LabelHash runs very efficiently in parallel; matching a motif against all proteins in the 95 % sequence identity filtered non-redundant Protein Data Bank typically takes no more than a few minutes. The LabelHash algorithm is available through a web server and as a suite of standalone programs a
Cryptosporidium sp. in children suffering from acute diarrhea at Uberlândia City, State of Minas Gerais, Brazil
This study's objective was to search for Cryptosporidium sp. in diarrheic feces from children aged zero to 12 years and cared for at medical units within Universidade Federal de Uberlândia or at a private practice in Uberlândia, State of Minas Gerais, Brazil, from September 1992 to August 1993. Three fecal samples preserved in 10% formalin, were collected from 94 children. Oocyst concentration was performed through Ritchie's (modified) method and staining of fecal smears for each sample (total of 1128 slides) was done by the "Safranin/Methylene Blue" and the "Kinyoun (modified)" techniques. The Hoffmann, Pons & Janer method was also employed to look for other enteroparasites. From 94 children, 4.26% excreted fecal Cryptosporidium oocysts. The infection seemed to vary according to age: 5.08% of patients aged zero to two years old; 33.33% of those aging eight to ten years (P>0.05). Cryptosporidium appeared in November, December and March, during the rainy season. 20.21% of the children harbored at least one enteroparasite different from Cryptosporidium, mainly Giardia intestinalis (12.77%). From Cryptosporidium infected patients, two had only this kind, another harbored Giardia intestinalis; the last one hosted Strongyloides stercoralis
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