327 research outputs found
A Decomposition Approach to Multi-Vehicle Cooperative Control
We present methods that generate cooperative strategies for multi-vehicle
control problems using a decomposition approach. By introducing a set of tasks
to be completed by the team of vehicles and a task execution method for each
vehicle, we decomposed the problem into a combinatorial component and a
continuous component. The continuous component of the problem is captured by
task execution, and the combinatorial component is captured by task assignment.
In this paper, we present a solver for task assignment that generates
near-optimal assignments quickly and can be used in real-time applications. To
motivate our methods, we apply them to an adversarial game between two teams of
vehicles. One team is governed by simple rules and the other by our algorithms.
In our study of this game we found phase transitions, showing that the task
assignment problem is most difficult to solve when the capabilities of the
adversaries are comparable. Finally, we implement our algorithms in a
multi-level architecture with a variable replanning rate at each level to
provide feedback on a dynamically changing and uncertain environment.Comment: 36 pages, 19 figures, for associated web page see
http://control.mae.cornell.edu/earl/decom
Label-free segmentation of co-cultured cells on a nanotopographical gradient
The function and fate of cells is influenced by many different factors, one of which is surface topography of the support culture substrate. Systematic studies of nanotopography and cell response have typically been limited to single cell types and a small set of topographical variations. Here, we show a radical expansion of experimental throughput using automated detection, measurement, and classification of co-cultured cells on a nanopillar array where feature height changes continuously from planar to 250 nm over 9 mm. Individual cells are identified and characterized by more than 200 descriptors, which are used to construct a set of rules for label-free segmentation into individual cell types. Using this approach we can achieve label-free segmentation with 84% confidence across large image data sets and suggest optimized surface parameters for nanostructuring of implant devices such as vascular stents
The SDSS-III Baryon Oscillation Spectroscopic Survey: Quasar Target Selection for Data Release Nine
The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year
spectroscopic survey of 10,000 deg^2, achieved first light in late 2009. One of
the key goals of BOSS is to measure the signature of baryon acoustic
oscillations in the distribution of Ly-alpha absorption from the spectra of a
sample of ~150,000 z>2.2 quasars. Along with measuring the angular diameter
distance at z\approx2.5, BOSS will provide the first direct measurement of the
expansion rate of the Universe at z > 2. One of the biggest challenges in
achieving this goal is an efficient target selection algorithm for quasars over
2.2 < z < 3.5, where their colors overlap those of stars. During the first year
of the BOSS survey, quasar target selection methods were developed and tested
to meet the requirement of delivering at least 15 quasars deg^-2 in this
redshift range, out of 40 targets deg^-2. To achieve these surface densities,
the magnitude limit of the quasar targets was set at g <= 22.0 or r<=21.85.
While detection of the BAO signature in the Ly-alpha absorption in quasar
spectra does not require a uniform target selection, many other astrophysical
studies do. We therefore defined a uniformly-selected subsample of 20 targets
deg^-2, for which the selection efficiency is just over 50%. This "CORE"
subsample will be fixed for Years Two through Five of the survey. In this paper
we describe the evolution and implementation of the BOSS quasar target
selection algorithms during the first two years of BOSS operations. We analyze
the spectra obtained during the first year. 11,263 new z>2.2 quasars were
spectroscopically confirmed by BOSS. Our current algorithms select an average
of 15 z > 2.2 quasars deg^-2 from 40 targets deg^-2 using single-epoch SDSS
imaging. Multi-epoch optical data and data at other wavelengths can further
improve the efficiency and completeness of BOSS quasar target selection.
[Abridged]Comment: 33 pages, 26 figures, 12 tables and a whole bunch of quasars.
Submitted to Ap
Environmental and Parental Influences on Offspring Health and Growth in Great Tits (Parus major)
PMCID: PMC3728352This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic
data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data
release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median
z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar
spectra, along with the data presented in previous data releases. These spectra
were obtained with the new BOSS spectrograph and were taken between 2009
December and 2011 July. In addition, the stellar parameters pipeline, which
determines radial velocities, surface temperatures, surface gravities, and
metallicities of stars, has been updated and refined with improvements in
temperature estimates for stars with T_eff<5000 K and in metallicity estimates
for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars
presented in DR8, including stars from SDSS-I and II, as well as those observed
as part of the SDSS-III Sloan Extension for Galactic Understanding and
Exploration-2 (SEGUE-2).
The astrometry error introduced in the DR8 imaging catalogs has been
corrected in the DR9 data products. The next data release for SDSS-III will be
in Summer 2013, which will present the first data from the Apache Point
Observatory Galactic Evolution Experiment (APOGEE) along with another year of
data from BOSS, followed by the final SDSS-III data release in December 2014.Comment: 9 figures; 2 tables. Submitted to ApJS. DR9 is available at
http://www.sdss3.org/dr
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in
operation since July 2014. This paper describes the second data release from
this phase, and the fourteenth from SDSS overall (making this, Data Release
Fourteen or DR14). This release makes public data taken by SDSS-IV in its first
two years of operation (July 2014-2016). Like all previous SDSS releases, DR14
is cumulative, including the most recent reductions and calibrations of all
data taken by SDSS since the first phase began operations in 2000. New in DR14
is the first public release of data from the extended Baryon Oscillation
Spectroscopic Survey (eBOSS); the first data from the second phase of the
Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2),
including stellar parameter estimates from an innovative data driven machine
learning algorithm known as "The Cannon"; and almost twice as many data cubes
from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous
release (N = 2812 in total). This paper describes the location and format of
the publicly available data from SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken (both
targeting and observation details) and processed for scientific use. The SDSS
website (www.sdss.org) has been updated for this release, and provides links to
data downloads, as well as tutorials and examples of data use. SDSS-IV is
planning to continue to collect astronomical data until 2020, and will be
followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14
happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov
2017 (this is the "post-print" and "post-proofs" version; minor corrections
only from v1, and most of errors found in proofs corrected
The state of the Martian climate
60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
Genome-Wide Tissue-Specific Occupancy of the Hox Protein Ultrabithorax and Hox Cofactor Homothorax in Drosophila
The Hox genes are responsible for generating morphological diversity along the
anterior-posterior axis during animal development. The
Drosophila Hox gene Ultrabithorax
(Ubx), for example, is required for specifying the identity
of the third thoracic (T3) segment of the adult, which includes the dorsal
haltere, an appendage required for flight, and the ventral T3 leg.
Ubx mutants show homeotic transformations of the T3 leg
towards the identity of the T2 leg and the haltere towards the wing. All Hox
genes, including Ubx, encode homeodomain containing
transcription factors, raising the question of what target genes
Ubx regulates to generate these adult structures. To
address this question, we carried out whole genome ChIP-chip studies to identify
all of the Ubx bound regions in the haltere and T3 leg imaginal discs, which are
the precursors to these adult structures. In addition, we used ChIP-chip to
identify the sites bound by the Hox cofactor, Homothorax (Hth). In contrast to
previous ChIP-chip studies carried out in Drosophila embryos,
these binding studies reveal that there is a remarkable amount of tissue- and
transcription factor-specific binding. Analyses of the putative target genes
bound and regulated by these factors suggest that Ubx regulates many downstream
transcription factors and developmental pathways in the haltere and T3 leg.
Finally, we discovered additional DNA sequence motifs that in some cases are
specific for individual data sets, arguing that Ubx and/or Hth work together
with many regionally expressed transcription factors to execute their functions.
Together, these data provide the first whole-genome analysis of the binding
sites and target genes regulated by Ubx to specify the morphologies of the adult
T3 segment of the fly
Spectral Classification and Redshift Measurement for the SDSS-III Baryon Oscillation Spectroscopic Survey
(abridged) We describe the automated spectral classification, redshift
determination, and parameter measurement pipeline in use for the Baryon
Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III
(SDSS-III) as of Data Release 9, encompassing 831,000 moderate-resolution
optical spectra. We give a review of the algorithms employed, and describe the
changes to the pipeline that have been implemented for BOSS relative to
previous SDSS-I/II versions, including new sets of stellar, galaxy, and quasar
redshift templates. For the color-selected CMASS sample of massive galaxies at
redshift 0.4 <~ z <~ 0.8 targeted by BOSS for the purposes of large-scale
cosmological measurements, the pipeline achieves an automated classification
success rate of 98.7% and confirms 95.4% of unique CMASS targets as galaxies
(with the balance being mostly M stars). Based on visual inspections of a
subset of BOSS galaxies, we find that ~0.2% of confidently reported CMASS
sample classifications and redshifts are incorrect, and ~0.4% of all CMASS
spectra are objects unclassified by the current algorithm which are potentially
recoverable. The BOSS pipeline confirms that ~51.5% of the quasar targets have
quasar spectra, with the balance mainly consisting of stars. Statistical (as
opposed to systematic) redshift errors propagated from photon noise are
typically a few tens of km/s for both galaxies and quasars, with a significant
tail to a few hundreds of km/s for quasars. We test the accuracy of these
statistical redshift error estimates using repeat observations, finding them
underestimated by a factor of 1.19 to 1.34 for galaxies, and by a factor of 2
for quasars. We assess the impact of sky-subtraction quality, S/N, and other
factors on galaxy redshift success. Finally, we document known issues, and
describe directions of ongoing development.Comment: 20 pages, multiple figures. Minor changes relative to version 1.
Accepted for publication in The Astronomical Journa
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