6,770 research outputs found
Proposal for an IMLS Collection Registry and Metadata Repository
The University of Illinois at Urbana-Champaign proposes to design, implement, and research a collection-level registry and item-level metadata repository service that will aggregate information about digital collections and items of digital content created using funds from Institute of Museum and Library Services (IMLS) National Leadership Grants. This work will be a collaboration by the University Library and the Graduate School of Library and Information Science. All extant digital collections initiated or augmented under IMLS aegis from 1998 through September 30, 2005 will be included in the proposed collection registry. Item-level metadata will be harvested from collections making such content available using the Open Archives Initiative Protocol for Metadata Harvesting (OAI PMH). As part of this work, project personnel, in cooperation with IMLS staff and grantees, will define and document appropriate metadata schemas, help create and maintain collection-level metadata records, assist in implementing OAI compliant metadata provider services for dissemination of item-level metadata records, and research potential benefits and issues associated with these activities. The immediate outcomes of this work will be the practical demonstration of technologies that have the potential to enhance the visibility of IMLS funded online exhibits and digital library collections and improve discoverability of items contained in these resources. Experience gained and research conducted during this project will make clearer both the costs and the potential benefits associated with such services. Metadata provider and harvesting service implementations will be appropriately instrumented (e.g., customized anonymous transaction logs, online questionnaires for targeted user groups, performance monitors). At the conclusion of this project we will submit a final report that discusses tasks performed and lessons learned, presents business plans for sustaining registry and repository services, enumerates and summarizes potential benefits of these services, and makes recommendations regarding future implementations of these and related intermediary and end user interoperability services by IMLS projects.unpublishednot peer reviewe
Dwarf galaxies beyond our doorstep: the Centaurus A group
The study of dwarf galaxies in groups is a powerful tool for investigating
galaxy evolution, chemical enrichment and environmental effects on these
objects. Here we present results obtained for dwarf galaxies in the Centaurus A
complex, a dense nearby (~4 Mpc) group that contains two giant galaxies and
about 30 dwarf companions of different morphologies and stellar contents. We
use archival optical (HST/ACS) and near-infrared (VLT/ISAAC) data to derive
physical properties and evolutionary histories from the resolved stellar
populations of these dwarf galaxies. In particular, for early-type dwarfs we
are able to construct metallicity distribution functions, find population
gradients and quantify the intermediate-age star formation episodes. For
late-type dwarfs, we compute recent (~1 Gyr) star formation histories and study
their stellar distribution. We then compare these results with properties of
the dwarfs in our Milky Way and in other groups. Our work will ultimately lead
to a better understanding of the evolution of dwarf galaxies.Comment: 6 pages, 5 figures; to appear in the proceedings of the conference "A
Universe of dwarf galaxies" (Lyon, June 14-18, 2010
Cluster Geometry & Inclinations from Deprojection Uncertainties
{The determination of cluster masses is a complex problem that would be aided
by information about the cluster shape and orientation (along the
line-of-sight).} {It is in this context, that we have developed a scheme for
identifying the intrinsic morphology and inclination of a cluster, by looking
for the signature of the true cluster characteristics in the inter-comparison
of the different deprojected emissivity profiles (that all project to the same
X-ray brightness distribution) and by using SZe data when available.} {We
deproject the cluster X-ray surface brightness profile under the assumptions of
four different geometry and inclination configurations for the observed system;
these 4 configurations correspond to four extreme geometry+inclination
scenarios. The deprojection in question is performed by the non-parametric
algorithm DOPING. The formalism is tested with model systems and then is
applied to a sample of 24 clusters. While the shape determination is possible
by implementing the X-ray brightness alone, the estimation of the inclination
is usually markedly improved by the usage of SZe data that is available for the
considered sample.}{We spot 8 prolate systems, 1 oblate and 15 of the clusters
in our sample as triaxial. In fact, for systems identified as triaxial, we are
able to discern how the three semi-axes lengths compare with each other. This,
when compounded by the information about the line-of-sight extent, allows us to
constrain the inclination quite tightly and offers the two intrinsic axial
ratios of the triaxial systems.}{}Comment: 15 pages of text, 6 figures, 4 tables, 1` appendix, accepted for
publication in A&
The value of standards for health datasets in artificial intelligence-based applications
Artificial intelligence as a medical device is increasingly being applied to healthcare for diagnosis, risk stratification and resource allocation. However, a growing body of evidence has highlighted the risk of algorithmic bias, which may perpetuate existing health inequity. This problem arises in part because of systemic inequalities in dataset curation, unequal opportunity to participate in research and inequalities of access. This study aims to explore existing standards, frameworks and best practices for ensuring adequate data diversity in health datasets. Exploring the body of existing literature and expert views is an important step towards the development of consensus-based guidelines. The study comprises two parts: a systematic review of existing standards, frameworks and best practices for healthcare datasets; and a survey and thematic analysis of stakeholder views of bias, health equity and best practices for artificial intelligence as a medical device. We found that the need for dataset diversity was well described in literature, and experts generally favored the development of a robust set of guidelines, but there were mixed views about how these could be implemented practically. The outputs of this study will be used to inform the development of standards for transparency of data diversity in health datasets (the STANDING Together initiative)
The Average Mass-to-Light Profile of Galaxy Clusters
The systematic errors in the virial mass-to-light ratio, M_v/L, of galaxy
clusters as an estimator of the field M/L value are assessed. We overlay 14
clusters in redshift space to create an ensemble cluster which averages over
substructure and asymmetries. The combined sample, including background,
contains about 1150 galaxies, extending to a projected radius of about twice
r_200. The radius r_200, defined as where the mean interior density is 200
times the critical density, is expected to contain the bulk of the virialized
cluster mass. The dynamically derived M(r_200)/L(r_200) of the ensemble is
0.82+/-0.14 . The M_v/L overestimate is attributed to not taking into
account the surface pressure term in the virial equation. Under the assumption
that the velocity anisotropy parameter is in the range 0<=\beta<=2/3, the
galaxy distribution accurately traces the mass profile beyond about the central
0.3r_200. There are no color or luminosity gradients in the galaxy population
beyond 2r_200, but there is 0.11+/-0.05 mag fading in the r band luminosities
between the field and cluster galaxies. We correct the cluster virial
mass-to-light ratio, M_v/L=289+/-50 h\msun/\lsun (calculated assuming q_0=0.1),
for the biases in M_v and mean luminosity to estimate the field M/L=213+/-59
h\msun/\lsun. With our self-consistently derived field luminosity density,
j/\rho_c=1136+/-138 h\msun/\lsun (at z~1/3), the corrected M/L indicates
\Omega_0=0.19+/-0.06+/-0.04 (formal 1\sigma random error and estimated
potential systematic errors).Comment: revised version accepted for publication in the ApJ, April 1, 1997
Also available at http://manaslu.astro.utoronto.ca/~carlberg/cnoc/profil
Intrauterine environment, mammary gland mass and breast cancer risk
Two intimately linked hypotheses on breast cancer etiology are described. The main postulate of the first hypothesis is that higher levels of pregnancy estrogens and other hormones favor the generation of a higher number of susceptible stem cells with compromised genomic stability. The second hypothesis postulates that the mammary gland mass, as a correlate of the number of cells susceptible to transformation, is an important determinant of breast cancer risk. A simple integrated etiological model for breast cancer is presented and it is indicated that the model accommodates most epidemiological aspects of breast cancer occurrence and natural history
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector
The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30
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