831 research outputs found
Facing the Crises of Higher Education: Reflections on a State University’s Experiment with TILT
Facing the Crises of Higher Education:
Reflections on a State University’s Experiment with TIL
Multi-Agent Search for a Moving and Camouflaging Target
In multi-agent search planning for a randomly moving and camouflaging target,
we examine heterogeneous searchers that differ in terms of their endurance
level, travel speed, and detection ability. This leads to a convex
mixed-integer nonlinear program, which we reformulate using three linearization
techniques. We develop preprocessing steps, outer approximations via lazy
constraints, and bundle-based cutting plane methods to address large-scale
instances. Further specializations emerge when the target moves according to a
Markov chain. We carry out an extensive numerical study to show the
computational efficiency of our methods and to derive insights regarding which
approach should be favored for which type of problem instance
The CORALIE survey for southern extra-solar planets XV. Discovery of two eccentric planets orbiting HD4113 and HD156846
We report the detection of two very eccentric planets orbiting HD4113 and
HD156846 with the CORALIE Echelle spectrograph mounted on the 1.2-m Euler Swiss
telescope at La Silla. The first planet, HD4113b, has minimum mass of
, a period of days and an
eccentricity of . It orbits a metal rich G5V star at
AU which displays an additional radial velocity drift of 28 m s/yr
observed during 8 years. The combination of the radial-velocity data and the
non-detection of any main sequence stellar companion in our high contrast
images taken at the VLT with NACO/SDI, characterizes the companion as a
probable brown dwarf or as a faint white dwarf. The second planet, \object{HD
156846 b}, has minimum mass of M, a period
of days, an eccentricity of and is located
at AU from its parent star. HD156846 is a metal rich G0 dwarf and is
also the primary of a wide binary system ( AU, years). Its
stellar companion, \object{IDS 17147-1914 B}, is a M4 dwarf. The very high
eccentricities of both planets can be explained by Kozai oscillations induced
by the presence of a third object.Comment: 4 pages, 5 figures, A&A Letter accepte
Dealing with paralogy in RADseq data: in silico detection and single nucleotide polymorphism validation in Robinia pseudoacacia L.
peer reviewedThe RADseq technology allows researchers to efficiently develop thousands of polymorphic
loci across multiple individuals with little or no prior information on the genome.
However, many questions remain about the biases inherent to this technology.
Notably, sequence misalignments arising from paralogy may affect the development of
single nucleotide polymorphism (SNP) markers and the estimation of genetic diversity.
We evaluated the impact of putative paralog loci on genetic diversity estimation during
the development of SNPs from a RADseq dataset for the nonmodel tree species Robinia
pseudoacacia L. We sequenced nine genotypes and analyzed the frequency of putative
paralogous RAD loci as a function of both the depth of coverage and the mismatch
threshold allowed between loci. Putative paralogy was detected in a very variable
number of loci, from 1% to more than 20%, with the depth of coverage having a major
influence on the result. Putative paralogy artificially increased the observed degree of
polymorphism and resulting estimates of diversity. The choice of the depth of coverage
also affected diversity estimation and SNP validation: A low threshold decreased
the chances of detecting minor alleles while a high threshold increased allelic dropout.
SNP validation was better for the low threshold (4×) than for the high threshold (18×)
we tested. Using the strategy developed here, we were able to validate more than 80%
of the SNPs tested by means of individual genotyping, resulting in a readily usable set
of 330 SNPs, suitable for use in population genetics applications
Association of plasma Aβ40/Aβ42 ratio and brain Aβ accumulation: testing a whole-brain PLS-VIP in individuals at risk of Alzheimer's disease
Molecular and brain regional/network-wise pathophysiological changes at preclinical stages of Alzheimer's disease (AD) have primarily been found through knowledge-based studies conducted in late-stage mild cognitive impairment/dementia populations. However, such an approach may compromise the objective of identifying the earliest spatial-temporal pathophysiological processes.
We investigated 261 individuals with subjective memory complaints, a condition at increased risk of AD, to test a whole-brain, non-a-priori method based on partial least squares, in unraveling the association between plasma Aβ42/Aβ40 ratio and an extensive set of brain regions characterized through molecular imaging of Aβ accumulation and cortical metabolism. Significant associations were mapped onto large-scale networks, identified through an atlas and by knowledge, to elaborate on the reliability of the results.
Plasma Aβ42/40 ratio was associated with Aβ-PET uptake (but not FDG-PET) in regions generally investigated in preclinical AD such as those belonging to the default mode network, but also in regions/networks normally not accounted - including the central executive and salience networks - which likely have a selective vulnerability to incipient Aβ accumulation.
The present whole-brain approach is promising to investigate early pathophysiological changes of AD to fully capture the complexity of the disease, which is essential to develop timely screening, detection, diagnostic, and therapeutic interventions
The Nucleon Spectral Function at Finite Temperature and the Onset of Superfluidity in Nuclear Matter
Nucleon selfenergies and spectral functions are calculated at the saturation
density of symmetric nuclear matter at finite temperatures. In particular, the
behaviour of these quantities at temperatures above and close to the critical
temperature for the superfluid phase transition in nuclear matter is discussed.
It is shown how the singularity in the thermodynamic T-matrix at the critical
temperature for superfluidity (Thouless criterion) reflects in the selfenergy
and correspondingly in the spectral function. The real part of the on-shell
selfenergy (optical potential) shows an anomalous behaviour for momenta near
the Fermi momentum and temperatures close to the critical temperature related
to the pairing singularity in the imaginary part. For comparison the selfenergy
derived from the K-matrix of Brueckner theory is also calculated. It is found,
that there is no pairing singularity in the imaginary part of the selfenergy in
this case, which is due to the neglect of hole-hole scattering in the K-matrix.
From the selfenergy the spectral function and the occupation numbers for finite
temperatures are calculated.Comment: LaTex, 23 pages, 21 PostScript figures included (uuencoded), uses
prc.sty, aps.sty, revtex.sty, psfig.sty (last included
Testing intermediate-age stellar evolution models with VLT photometry of LMC clusters. I. The data
This is the first of a series of three papers devoted to the calibration of a
few parameters of crucial importance in the modeling of the evolution of
intermediate-mass stars, with special attention to the amount of convective
core overshoot. To this end we acquired deep V and R photometry for three
globular clusters of the Large Magellanic Cloud (LMC), namely NGC 2173, SL 556
and NGC 2155, in the age interval 1-3 Gyr. In this first paper, we describe the
aim of the project, the VLT observations and data reduction, and we make
preliminary comparisons of the color-magnitude diagrams with both Padova and
Yonsei-Yale isochrones. Two following papers in this series present the results
of a detailed analysis of these data, independently carried out by members of
the Yale and Padova stellar evolution groups. This allows us to compare both
sets of models and discuss their main differences, as well as the systematic
effects that they would have to the determination of the ages and metallicities
of intermediate-age single stellar populations.Comment: 27 pages with 10 figures. Accepted by the Astronomical Journa
The COSMOS-WIRCam near-infrared imaging survey: I: BzK selected passive and star forming galaxy candidates at z>1.4
(abridged) We present a new near-infrared survey covering the 2 deg sq COSMOS
field. Combining our survey with Subaru B and z images we construct a deep,
wide-field optical-infrared catalogue. At Ks<23 (AB magnitudes) our survey
completeness is greater than 90% and 70% for stars and galaxies respectively
and contains 143,466 galaxies and 13,254 stars. At z~2 our catalogues contain
3931 quiescent and 25,757 star-forming BzK-selected galaxies representing the
largest and most secure sample of these objects to date. Our counts of
quiescent galaxies turns over at Ks~22 an effect which we demonstrate cannot be
due to sample incompleteness. In our survey both the number of faint and bright
quiescent objects exceeds the predictions of a semi-analytic galaxy formation
model, indicating potentially the need for further refinements in the amount of
merging and AGN feedback at z~2 in these models. We measure the angular
correlation function for each sample and find that at small scales the
correlation function for passive BzK galaxies exceeds the clustering of dark
matter. We use 30-band photometric redshifts to derive the spatial correlation
length and the redshift distributions for each object class. At Ks<22 we find
r_0^{\gamma/1.8}=7.0 +/-0.5h^{-1} Mpc for the passive BzK candidates and
4.7+/-0.8h^{-1} Mpc for the star-forming BzK galaxies. Our pBzK galaxies have
an average photometric redshift of z_p~1.4, in approximate agreement with the
limited spectroscopic information currently available. The stacked Ks image
will be made publicly available from IRSA.Comment: Accepted for publication in Astrophysical Journal. 17 pages, 17
figures, minor revisions to match published version available at
http://adsabs.harvard.edu/abs/2010ApJ...708..202
VLT/SPHERE deep insight of NGC 3603's core: Segregation or confusion?
We present new near-infrared photometric measurements of the core of the
young massive cluster NGC 3603 obtained with extreme adaptive optics. The data
were obtained with the SPHERE instrument mounted on ESO Very Large Telescope,
and cover three fields in the core of this cluster. We applied a correction for
the effect of extinction to our data obtained in the J and K broadband filters
and estimated the mass of detected sources inside the field of view of
SPHERE/IRDIS, which is 13.5"x13.5". We derived the mass function (MF) slope for
each spectral band and field. The MF slope in the core is unusual compared to
previous results based on Hubble space telescope (HST) and very large telescope
(VLT) observations. The average slope in the core is estimated as
-1.06^{+0.26}_{-0.26} for the main sequence stars with 3.5 Msun < M < 120
Msun.Thanks to the SPHERE extreme adaptive optics, 814 low-mass stars were
detected to estimate the MF slope for the pre-main sequence stars with 0.6
Msun< M < 3.5 Msun , Gamma = -0.54^{+0.11}_{-0.11} in the K-band images in two
fields in the core of the cluster. For the first time, we derive the mass
function of the very core of the NGC 3603 young cluster for masses in the range
0.6 - 120 Msun. Previous studies were either limited by crowding, lack of
dynamic range, or a combination of both
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