26,743 research outputs found
Locally Estimating Core Numbers
Graphs are a powerful way to model interactions and relationships in data
from a wide variety of application domains. In this setting, entities
represented by vertices at the "center" of the graph are often more important
than those associated with vertices on the "fringes". For example, central
nodes tend to be more critical in the spread of information or disease and play
an important role in clustering/community formation. Identifying such "core"
vertices has recently received additional attention in the context of {\em
network experiments}, which analyze the response when a random subset of
vertices are exposed to a treatment (e.g. inoculation, free product samples,
etc). Specifically, the likelihood of having many central vertices in any
exposure subset can have a significant impact on the experiment.
We focus on using -cores and core numbers to measure the extent to which a
vertex is central in a graph. Existing algorithms for computing the core number
of a vertex require the entire graph as input, an unrealistic scenario in many
real world applications. Moreover, in the context of network experiments, the
subgraph induced by the treated vertices is only known in a probabilistic
sense. We introduce a new method for estimating the core number based only on
the properties of the graph within a region of radius around the
vertex, and prove an asymptotic error bound of our estimator on random graphs.
Further, we empirically validate the accuracy of our estimator for small values
of on a representative corpus of real data sets. Finally, we evaluate
the impact of improved local estimation on an open problem in network
experimentation posed by Ugander et al.Comment: Main paper body is identical to previous version (ICDM version).
Appendix with additional data sets and enlarged figures has been added to the
en
Shuttle electrical environment
Part of an AFGL payload flown on the STS-4 mission consisted of experiments to measure in-situ electric fields, electron densities, and vehicle charging. During this flight some 11 hours of data were acquired ranging from 5 minute snapshots up to continuous half-orbits. These experiments are described and results presented for such vehicle induced events as a main engine burn, thruster firings and water dumps in addition to undisturbed periods. The main characteristic of all the vehicle induced events is shown to be an enhancement in the low frequency noise (less than 2 kHz), in both the electrostatic and electron irregularity (delta N/N) spectra. The non-event results indicate that the electrostatic broadband emissions show a white noise characteristic in the low frequency range up to 2 kHz at an amplitude of 10 db above the shuttle design specification limit, falling below that limit above 10 kHz. The vehicle potential remained within the range of -3 to +1 volt throughout the flight which exhibits normal behavior for a satellite in a low equatorial orbit
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Shared geriatric mental health care in a rural community
Introduction: A pilot project in shared mental health care was initiated to explore opportunities to increase the capacity of the rural primary care system as a resource for older people with mental health needs. This was done within a framework for the delivery of best practices in geriatric mental health outreach. Methods: Shared-care strategies combining education and clinical consultation between mentor psychiatrists and family physicians were implemented and then evaluated after one year to identify key factors in the success of approaches to shared mental health care for older people in a rural setting. Results: Results provided new insights into shared care between primary care and specialty geriatric mental health services, rural geriatric mental health service delivery, developmental phases in service learning approaches, and building knowledge networks to promote continuing best practices. Conclusion: The results from the project's process evaluation have been integrated into the development of a permanent shared geriatric mental health care service for the rural setting. Preparation for an outcome evaluation that will focus on the impact on patient care has also been initiated
Bose-Einstein Correlations and the Equation of State of Nuclear Matter
Within a relativistic hydrodynamic framework, we use four different equations
of state of nuclear matter to compare to experimental spectra from CERN/SPS
experiments NA44 and NA49. Freeze-out hypersurfaces and Bose-Einstein
correlation functions for identical pion pairs are discussed. We find that
two-pion Bose-Einstein interferometry measures the relationship between the
temperature and the energy density in the equation of state during the late
hadronic stage of the fireball expansion. Little sensitivity of the
light-hadron data to a quark-gluon plasma phase-transition is seen.Comment: 4 pages, including 4 figures. You can also download a PostScript file
of the manuscript from http://p2hp2.lanl.gov/people/schlei/eprint.htm
Ramsey interferometry with oppositely detuned fields
We report a narrowing of the interference pattern obtained in an atomic
Ramsey interferometer if the two separated fields have different frequency and
their phase difference is controlled. The width of the Ramsey fringes depends
inversely on the free flight time of ground state atoms before entering the
first field region in addition to the time between the fields. The effect is
stable also for atomic wavepackets with initial position and momentum
distributions and for realistic mode functions.Comment: 6 pages, 6 figure
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