2,575 research outputs found
Metal-insulator transition in YHx: scaling of the sub-THz conductivity
The established scaling laws of the conductivity with temperature and doping
are strong indications for the quantum nature of the metal-insulator transition
in YH. Here we report the first results on the frequency scaling of the
conductivity. Samples were brought from the insulating to the metallic phase by
carrier doping via illumination. In the metallic phase, the sub-terahertz
conductivity coincides with the dc data. These results do not agree with the
simplest picture of a quantum-phase transition.Comment: 4 pages, accepted to PR
Hubble Space Telescope weak lensing study of the z=0.83 cluster MS 1054-03
We have measured the weak gravitational lensing signal of MS 1054-03, a rich
and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a
two-colour mosaic of deep WFPC2 images. The small corrections for the size of
the PSF and the high number density of background galaxies obtained in these
observations result in an accurate and well calibrated measurement of the
lensing induced distortion. The strength of the lensing signal depends on the
redshift distribution of the background galaxies. We used photometric redshift
distributions from the Northern and Southern Hubble Deep Fields to relate the
lensing signal to the mass. The predicted variations of the signal as a
function of apparent source magnitude and colour agrees well with the observed
lensing signal. We determine a mass of (1.2+-0.2)x10^15 Msun within an aperture
of radius 1 Mpc. Under the assumption of an isothermal mass distribution, the
corresponding velocity dispersion is 1311^{+83}_{-89} km/s. For the
mass-to-light ratio we find 269+-37 Msun/Lsun. The errors in the mass and
mass-to-light ratio include the contribution from the random intrinsic
ellipticities of the source galaxies, but not the (systematic) error due to the
uncertainty in the redshift distribution. However, the estimates for the mass
and mass-to-light ratio of MS 1054-03 agree well with other estimators,
suggesting that the mass calibration works well. The reconstruction of the
projected mass surface density shows a complex mass distribution, consistent
with the light distribution. The results indicate that MS 1054-03 is a young
system. The timescale for relaxation is estimated to be at least 1 Gyr.
Averaging the tangential shear around the cluster galaxies, we find that the
velocity dispersion of an Lstar galaxy is 203+-33 km/s.Comment: 21 pages, Latex, with 27 figures (3 figures bitmapped), ApJ, in
press. Version (with non-bitmapped figures) available at
http://www.astro.rug.nl/~hoekstra/papers.htm
On the homotopy type of complexes of graphs with bounded domination number
Let be the complex of graphs on vertices and domination
number at least . We prove that has the homotopy type of a
finite wedge of 2-spheres. This is done by using discrete Morse theory
techniques. Acyclicity of the needed matching is proved by introducing a
relativized form of a much used method for constructing acyclic matchings on
suitable chunks of simplices. Our approach allows us to extend our results to
the realm of infinite graphs. We give evidence supporting the assertion that
the homotopy equivalence does not generalize
as expected for , if .Comment: 19 page
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Genetic and environmental covariation between autistic traits and behavioral problems
Objective: To examine the overlap between autistic traits and other behavioral problems in a general population sample, and explore the extent to which this overlap is due to genetic or environmental factors. Method: Youth Self Report (YSR) data were collected in a general population sample of 424 twin pairs at 18 years of age, and their non twin siblings. In 197 of these twin families, self-report ratings on the Autism-spectrum Quotient (AQ) were collected. Results: Stepwise backward regression analyses revealed that of all 8 YSR syndrome scales, the Withdrawn Behavior (WB) and Social Problems (SOC) scale were the most important predictors of AQ scores, and together with sex, explained 23% of the variance in AQ scores. Genetic structural equation modeling showed that the overlap between AQ and WB and SOC was mainly due to genetic effects. About half of the genetic variance in AQ scores was specific to the AQ, with the remaining half shared with genetic variance in WB and SOC. Conclusions: Endorsement of autistic traits in a general population sample is associated with social and withdrawn behavioral problems and these problems partly share a common genetic etiology with autistic traits. However, most of the variance in AQ scores remains unexplained by YSR scores, and half of the genetic variance in AQ is unshared with WB and SOC. These results indicate that autistic traits have specific characteristics that are substantially genetically independent from other common but related behavioral domains such as social problems and withdrawn behavior
Oscillatory Patterns In Angular Differential Ion-Atom Charge Exchange Cross Sections: The Role Of Electron Saddle Swaps
In this work, we have performed an experimental/theoretical study of state selective charge exchange cross sections in 1-10 keV/amu Ne8+ +Na(3s) collisions. Theoretical calculations provided by the classical trajectory Monte Carlo method (CTMC) are contrasted to data obtained at KVI by means of the magneto-optical trap recoil-ion momentum spectroscopy technique (MOTRIMS). We find that for electron capture to n 10, a two-step mechanism which involves an initial electronic excitation followed by electron capture at a later stage of the collision applies. Oscillatory structures in the n-state selective capture cross sections and recoil ion transverse momentum distributions are present in the experimental data as well as in the theoretical results, and are ascribed to the number of swaps the electron undergoes across the potential energy saddle during the collision process.Fil: Otranto, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Física; ArgentinaFil: Blank, I.. Kernfysisch Versneller Instituut. Atomic Physics; Países BajosFil: Olson, R. E.. Missouri University of Science and Technology; Estados UnidosFil: Hoekstra, R.. Kernfysisch Versneller Instituut. Atomic Physics; Países Bajo
Diversity in the stellar velocity dispersion profiles of a large sample of Brightest Cluster Galaxies
We analyse spatially-resolved deep optical spectroscopy of Brightest Cluster
Galaxies (BCGs) located in 32 massive clusters with redshifts of 0.05 0.30, to investigate their velocity dispersion profiles. We compare these
measurements to those of other massive early-type galaxies, as well as central
group galaxies, where relevant. This unique, large sample extends to the most
extreme of massive galaxies, spanning M between -25.7 to -27.8 mag, and
host cluster halo mass M up to 1.7 10 M. To
compare the kinematic properties between brightest group and cluster members,
we analyse similar spatially-resolved long-slit spectroscopy for 23 nearby
Brightest Group Galaxies (BGGs) from the Complete Local-Volume Groups Sample
(CLoGS). We find a surprisingly large variety in velocity dispersion slopes for
BCGs, with a significantly larger fraction of positive slopes, unique compared
to other (non-central) early-type galaxies as well as the majority of the
brightest members of the groups. We find that the velocity dispersion slopes of
the BCGs and BGGs correlate with the luminosity of the galaxies, and we
quantify this correlation. It is not clear whether the full diversity in
velocity dispersion slopes that we see is reproduced in simulations.Comment: 25 pages, 17 figures, accepted for publication in MNRA
Heritability of testosterone levels in 12-year-old twins and its relation to pubertal development
The aim of this study was to estimate the heritability of variation in testosterone levels in 12-year-old children, and to explore the overlap in genetic and environmental influences on circulating testosterone levels and androgen dependent pubertal development. Midday salivary testosterone samples were collected on two consecutive days in a sample of 183 unselected twin pairs. Androgen induced pubertal development was assessed using self report Tanner scales of pubic hair development (boys and girls) and genital development (boys). A significant contribution of genetic effects to the variance in testosterone levels was found.
Heritability was approximately 50% in both boys and girls. The remaining proportion of the variance in testosterone levels could be explained by non-shared environmental influences. The relatively high correlation between testosterone levels of opposite sex dizygotic twins suggests that sex differences in genes influencing variation in testosterone levels have not yet developed in pre- and early puberty. Variance in pubertal development was explained by a large genetic component, moderate shared environmental influences, and a small non-shared environmental effect. Testosterone levels correlated moderately (r = .31) with pubertal development; the covariance between testosterone levels and pubertal development was entirely accounted for by genetic influences
Residual work capacity and (in)ability to work fulltime among a year cohort of cancer survivors who claim a disability benefit
PURPOSE: Residual work capacity (RWC) and inability to work fulltime (IWF) are important outcomes in disability benefit assessments for workers diagnosed with cancer. The aim of this study is to gain insight into the prevalence of both outcomes, the associations of disease-related and socio-demographic factors and if these differ across cancer diagnosis groups.METHODS: A year cohort of anonymized register data of cancer survivors who claim a disability benefit after 2 years of sick leave (n = 3690, age 53.3 ± 8.8, 60.4% female) was used. Having no RWC was defined as having no possibilities to perform any work at all, whereas IWF was defined as being able to work less than 8 h per day.RESULTS: The prevalence of being assessed with no RWC was 42.6%. Of the applicants with RWC (57.4%), 69.8% were assessed with IWF. Cancers of the respiratory organs showed the highest odds for having no RWC, whereas lymphoid and haematopoietic cancers showed the highest odds for IWF. Within specific cancer diagnosis groups, different associations were identified for both outcomes.CONCLUSION: The prevalence of no RWC and IWF in applicants of work disability benefits diagnosed with cancer is high compared to the prevalence in other diagnoses. The odds for no RWC, IWF, and associated factors differ per cancer diagnosis group.IMPLICATIONS FOR CANCER SURVIVORS: Being diagnosed with cancer has an enormous impact on work (dis)ability. Our results show that 2 years after being diagnosed with cancer, the majority of the disability benefit applicants are assessed with RWC; however, only 15% of all applicants with cancer had a normal ability to work fulltime, and therefore, it is of great importance to accompany them in their return to work.</p
Cosmic Shear Analysis with CFHTLS Deep data
We present the first cosmic shear measurements obtained from the T0001
release of the Canada-France-Hawaii Telescope Legacy Survey. The data set
covers three uncorrelated patches (D1, D3 and D4) of one square degree each
observed in u*, g', r', i' and z' bands, out to i'=25.5. The depth and the
multicolored observations done in deep fields enable several data quality
controls. The lensing signal is detected in both r' and i' bands and shows
similar amplitude and slope in both filters. B-modes are found to be
statistically zero at all scales. Using multi-color information, we derived a
photometric redshift for each galaxy and separate the sample into medium and
high-z galaxies. A stronger shear signal is detected from the high-z subsample
than from the low-z subsample, as expected from weak lensing tomography. While
further work is needed to model the effects of errors in the photometric
redshifts, this results suggests that it will be possible to obtain constraints
on the growth of dark matter fluctuations with lensing wide field surveys. The
various quality tests and analysis discussed in this work demonstrate that
MegaPrime/Megacam instrument produces excellent quality data. The combined Deep
and Wide surveys give sigma_8= 0.89 pm 0.06 assuming the Peacock & Dodds
non-linear scheme and sigma_8=0.86 pm 0.05 for the halo fitting model and
Omega_m=0.3. We assumed a Cold Dark Matter model with flat geometry.
Systematics, Hubble constant and redshift uncertainties have been marginalized
over. Using only data from the Deep survey, the 1 sigma upper bound for w_0,
the constant equation of state parameter is w_0 < -0.8.Comment: 14 pages, 16 figures, accepted A&
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