10,352 research outputs found
The Distribution of ALFALFA Galaxies
The ALFALFA blind HI survey will enable a census of the distribution of
gas-rich galaxies in the local Universe. Sensitive to an HI mass of 10**7 solar
masses at the distance of the Virgo cluster, ALFALFA will probe the smallest
objects locally and provide a new consideration of near-field cosmology.
Additionally, with a larger, cosmologically significant sample volume and wider
bandwidth than previous blind surveys, a much larger number of detections in
each mass bin is possible, with adequate angular resolution to eliminate the
need for extensive follow-up observations. This increased sensitivity will
greatly enhance the utility of cosmological probles in HI. ALFALFA will
eventually measure the correlation function of HI selected galaxies in a large
local volume. The larger sample and volume size of the ALFALFA dataset will
also robustly measure the HI mass function (HIMF). Here, we present the
preliminary results on the distribution of local gas-rich galaxies from a first
ALFALFA catalog covering 540 deg**2.Comment: To appear in Proceedings of IAU Symp. Number 244, "Dark Galaxies and
Lost Baryons", June 2007, 2 pages including 1 figur
Research, Analysis and Insight into National Standards (RAINS) Project. First Report: Researching Schoolsā Enactments of New Zealandās National Standards Policy
This is the first report of the Research, Analysis and Insight into National Standards (RAINS) project, one year into a three-year study of the introduction of National Standards into New Zealand primary and intermediate schools
Markov chain comparison
This is an expository paper, focussing on the following scenario. We have two
Markov chains, and . By some means, we have
obtained a bound on the mixing time of . We wish to compare
with in order to derive a corresponding bound on
the mixing time of . We investigate the application of the
comparison method of Diaconis and Saloff-Coste to this scenario, giving a
number of theorems which characterize the applicability of the method. We focus
particularly on the case in which the chains are not reversible. The purpose of
the paper is to provide a catalogue of theorems which can be easily applied to
bound mixing times.Comment: Published at http://dx.doi.org/10.1214/154957806000000041 in the
Probability Surveys (http://www.i-journals.org/ps/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Developing a Performance Assessment System From the Ground Up: Lessons Learned From Three Linked Learning Pathways
This document is designed to offer practitioners -- teachers, principals, and central office administrators -- models, tools, and examples from the Linked Learning field for developing a performance assessment system. This document describes the challenges and successes practitioners encountered when developing and implementing authentic performance-based assessment practices and systems in Linked Learning pathways as well as the conditions that enabled this work. It is the product of a 1-year study of three grade-level teams, located in three different Linked Learning pathways across California. These teams participated in a 2-year performance assessment demonstration project led by ConnectEd and Envision
The Complexity of Approximately Counting Stable Matchings
We investigate the complexity of approximately counting stable matchings in
the -attribute model, where the preference lists are determined by dot
products of "preference vectors" with "attribute vectors", or by Euclidean
distances between "preference points" and "attribute points". Irving and
Leather proved that counting the number of stable matchings in the general case
is #P-complete. Counting the number of stable matchings is reducible to
counting the number of downsets in a (related) partial order and is
interreducible, in an approximation-preserving sense, to a class of problems
that includes counting the number of independent sets in a bipartite graph
(#BIS). It is conjectured that no FPRAS exists for this class of problems. We
show this approximation-preserving interreducibilty remains even in the
restricted -attribute setting when (dot products) or
(Euclidean distances). Finally, we show it is easy to count the number of
stable matchings in the 1-attribute dot-product setting.Comment: Fixed typos, small revisions for clarification, et
Matrix norms and rapid mixing for spin systems
We give a systematic development of the application of matrix norms to rapid
mixing in spin systems. We show that rapid mixing of both random update Glauber
dynamics and systematic scan Glauber dynamics occurs if any matrix norm of the
associated dependency matrix is less than 1. We give improved analysis for the
case in which the diagonal of the dependency matrix is (as in heat
bath dynamics). We apply the matrix norm methods to random update and
systematic scan Glauber dynamics for coloring various classes of graphs. We
give a general method for estimating a norm of a symmetric nonregular matrix.
This leads to improved mixing times for any class of graphs which is hereditary
and sufficiently sparse including several classes of degree-bounded graphs such
as nonregular graphs, trees, planar graphs and graphs with given tree-width and
genus.Comment: Published in at http://dx.doi.org/10.1214/08-AAP532 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
An approximation trichotomy for Boolean #CSP
We give a trichotomy theorem for the complexity of approximately counting the
number of satisfying assignments of a Boolean CSP instance. Such problems are
parameterised by a constraint language specifying the relations that may be
used in constraints. If every relation in the constraint language is affine
then the number of satisfying assignments can be exactly counted in polynomial
time. Otherwise, if every relation in the constraint language is in the
co-clone IM_2 from Post's lattice, then the problem of counting satisfying
assignments is complete with respect to approximation-preserving reductions in
the complexity class #RH\Pi_1. This means that the problem of approximately
counting satisfying assignments of such a CSP instance is equivalent in
complexity to several other known counting problems, including the problem of
approximately counting the number of independent sets in a bipartite graph. For
every other fixed constraint language, the problem is complete for #P with
respect to approximation-preserving reductions, meaning that there is no fully
polynomial randomised approximation scheme for counting satisfying assignments
unless NP=RP
Seeding without leading: making space for participant contribution in design elicitation techniques
As HCI embraces experience design, it will increasingly rely
on new elicitation methods that are capable of drawing out the multi-faceted subjectivities of individuals without being overly prescriptive as to the final design or experience outcome. In this panel we wish to describe and discuss subtle elicitation techniques that allow the elicitation of participant ideas and interests with minimum prejudicing by the researcher. We argue that leaving space for meaning to be made by project nformants is a valuable approach to understanding both design requirements and use issues. We show work that has come from taking this approach and discuss why we have been concerned to keep a creative space open in our research and how we invite people into i
Contact-mediated control of radial migration of corneal epithelial cells
We thank Darrin Sheppard and other staff at the University of Aberdeen Medical Research Facility for specialist technical assistance. We thank Patsy D. Goast for overnight microscope monitoring. This work was performed under the Biotechnology and Bioscience Research Council Grant number BB/E015840/1 to JMC.Peer reviewedPublisher PD
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