860 research outputs found
Microarray-based method for detection of unknown genetic modifications
<p>Abstract</p> <p>Background</p> <p>Due to the increased use of genetic modifications in crop improvement, there is a need to develop effective methods for the detection of both known and unknown transgene constructs in plants. We have developed a strategy for detection and characterization of unknown genetic modifications and we present a proof of concept for this method using <it>Arabidopsis thaliana </it>and <it>Oryza sativa </it>(rice). The approach relies on direct hybridization of total genomic DNA to high density microarrays designed to have probes tiled throughout a set of reference sequences.</p> <p>Results</p> <p>We show that by using arrays with 25 basepair probes covering both strands of a set of 235 vectors (2 million basepairs) we can detect transgene sequences in transformed lines of <it>A. thaliana </it>and rice without prior knowledge about the transformation vectors or the T-DNA constructs used to generate the studied plants.</p> <p>Conclusion</p> <p>The approach should allow the user to detect the presence of transgene sequences and get sufficient information for further characterization of unknown genetic constructs in plants. The only requirements are access to a small amount of pure transgene plant material, that the genetic construct in question is above a certain size (here ⼠140 basepairs) and that parts of the construct shows some degree of sequence similarity with published genetic elements.</p
Disk Detective: Discovery of New Circumstellar Disk Candidates through Citizen Science
The Disk Detective citizen science project aims to find new stars with 22
micron excess emission from circumstellar dust using data from NASA's WISE
mission. Initial cuts on the AllWISE catalog provide an input catalog of
277,686 sources. Volunteers then view images of each source online in 10
different bands to identify false-positives (galaxies, background stars,
interstellar matter, image artifacts, etc.). Sources that survive this online
vetting are followed up with spectroscopy on the FLWO Tillinghast telescope.
This approach should allow us to unleash the full potential of WISE for finding
new debris disks and protoplanetary disks. We announce a first list of 37 new
disk candidates discovered by the project, and we describe our vetting and
follow-up process. One of these systems appears to contain the first debris
disk discovered around a star with a white dwarf companion: HD 74389. We also
report four newly discovered classical Be stars (HD 6612, HD 7406, HD 164137,
and HD 218546) and a new detection of 22 micron excess around a previously
known debris disk host star, HD 22128.Comment: 50 pages, accepted for publication in the Astrophysical Journa
Debris Disks: Probing Planet Formation
Debris disks are the dust disks found around ~20% of nearby main sequence
stars in far-IR surveys. They can be considered as descendants of
protoplanetary disks or components of planetary systems, providing valuable
information on circumstellar disk evolution and the outcome of planet
formation. The debris disk population can be explained by the steady
collisional erosion of planetesimal belts; population models constrain where
(10-100au) and in what quantity (>1Mearth) planetesimals (>10km in size)
typically form in protoplanetary disks. Gas is now seen long into the debris
disk phase. Some of this is secondary implying planetesimals have a Solar
System comet-like composition, but some systems may retain primordial gas.
Ongoing planet formation processes are invoked for some debris disks, such as
the continued growth of dwarf planets in an unstirred disk, or the growth of
terrestrial planets through giant impacts. Planets imprint structure on debris
disks in many ways; images of gaps, clumps, warps, eccentricities and other
disk asymmetries, are readily explained by planets at >>5au. Hot dust in the
region planets are commonly found (<5au) is seen for a growing number of stars.
This dust usually originates in an outer belt (e.g., from exocomets), although
an asteroid belt or recent collision is sometimes inferred.Comment: Invited review, accepted for publication in the 'Handbook of
Exoplanets', eds. H.J. Deeg and J.A. Belmonte, Springer (2018
Millimeter Dust Emission and Planetary Dynamics in the HD 106906 System
Debris disks are dusty, optically thin structures around main sequence stars.
HD 106906AB is a short-period stellar binary, host to a wide separation planet,
HD 106906b, and a debris disk. Only a few known systems include a debris disk
and a directly imaged planet, and HD 106906 is the only one in which the planet
is exterior to the disk. The debris disk is edge-on and highly asymmetric in
scattered light. Here we resolve the disk structure at a resolution of 0.38"
(39 au) with the Atacama Large Millimeter/submillimeter Array (ALMA) at a
wavelength of 1.3 mm. We model the disk with both a narrow and broad ring of
material, and find that a radially broad, axisymmetric disk between radii of
50100 au is able to capture the structure of the observations without
evidence of any asymmetry or eccentricity, other than a tentative stellocentric
offset. We place stringent upper limits on both the gas and dust content of a
putative circumplanetary disk. We interpret the ALMA data in concert with
scattered light observations of the inner ring and astrometric constraints on
the planet's orbit, and find that the observations are consistent with a
large-separation, low-eccentricity orbit for the planet. A dynamical analysis
indicates that the central binary can efficiently stabilize planetesimal orbits
interior to 100 au, which relaxes the constraints on eccentricity and
semimajor axis somewhat. The observational constraints are consistent with in
situ formation via gravitational instability, but cannot rule out a scattering
event as the origin for HD 106906b's current orbit
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Precise measurement of the W-boson mass with the CDF II detector
We have measured the W-boson mass MW using data corresponding to 2.2/fb of
integrated luminosity collected in proton-antiproton collisions at 1.96 TeV
with the CDF II detector at the Fermilab Tevatron collider. Samples consisting
of 470126 W->enu candidates and 624708 W->munu candidates yield the measurement
MW = 80387 +- 12 (stat) +- 15 (syst) = 80387 +- 19 MeV. This is the most
precise measurement of the W-boson mass to date and significantly exceeds the
precision of all previous measurements combined
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
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