867 research outputs found
Complex structures in galaxy cluster fields: implications for gravitational lensing mass models
The distribution of mass on galaxy cluster scales is an important test of
structure formation scenarios, providing constraints on the nature of dark
matter itself. Several techniques have been used to probe the mass
distributions of clusters, sometimes yielding results which are discrepant, or
at odds with clusters formed in simulations - for example giving NFW
concentration parameters much higher than expected in the standard CDM model.
In addition, the velocity fields of some well studied galaxy clusters reveal
the presence of several structures close to the line-of-sight, often not
dynamically bound to the cluster itself. We investigate what impact such
neighbouring but unbound massive structures would have on the determination of
cluster profiles using weak gravitational lensing. Depending on its
concentration and mass ratio to the primary halo, one secondary halo close to
the line-of-sight can cause the estimated NFW concentration parameter to be
significantly higher than that of the primary halo, and also cause the
estimated mass to be biased high. Although it is difficult to envisage how this
mechanism alone could yield concentrations as high as reported for some
clusters, multiple haloes close to the line-of-sight, such as in the case of
Abell 1689, can substantially increase the concentration parameter estimate.
Together with the fact that clusters are triaxial, and that including baryonic
physics also leads to an increase in the concentration of a dark matter halo,
the tension between observations and the standard CDM model is eased. If the
alignment with the secondary structure is imprecise, then the estimated
concentration parameter can also be even lower than that of the primary halo,
reinforcing the importance of identifying structures in cluster fields.Comment: To appear in MNRAS letters, 5 pages, 3 figure
INSURANCE Georgia Motor Vehicle Accident Reparations Act: Repeal Provisions Requiring Personal Injury Protection Insurance Coverage and Related Provisions
The Act repeals and adds a number of Code sections dealing with Georgia\u27s automobile insurance legislation. The central measure of the Act repeals and revises provisions of the Georgia Motor Vehicle Accident Reparations Act that require personal injury protection insurance coverage. Other key features include a mandatory fifteen percent rollback of certain motor vehicle insurance rates and an additional ten percent discount for motorists with good driving records; tighter regulation of insurance rates by requiring prior approval by the Insurance Commissioner of any rating plan; adding powers to regulate fraud including provisions making it easier to report fraud, increasing the powers of the Insurance Commissioner to arrest persons for insurance fraud, and making fraud a felony offense; and providing guidelines to govern the cancellation or nonrenewal of automobile or motorcycle insurance policies
An MCMC Fitting Method for Triaxial Dark Matter Haloes
Measuring the 3D distribution of mass on galaxy cluster scales is a crucial
test of the LCDM model, providing constraints on the behaviour of dark matter.
Recent work investigating mass distributions of individual galaxy clusters
(e.g. Abell 1689) using weak and strong gravitational lensing has revealed
potential inconsistencies between the predictions of structure formation models
relating halo mass to concentration and those relationships as measured in
massive clusters. However, such analyses employ simple spherical halo models
while a growing body of work indicates that triaxial 3D halo structure is both
common and important in parameter estimates. The very strong assumptions about
the symmetry of the lensing halo implied with circular or perturbative
elliptical NFW models are not physically motivated and lead to incorrect
parameter estimates with significantly underestimated error bars. We here
introduce a Markov Chain Monte Carlo (MCMC) method to fit fully triaxial models
to weak lensing data that gives parameter and error estimates that fully
incorporate the true uncertainty present in nature. Applying the MCMC triaxial
fitting method to a population of NFW triaxial lenses drawn from the shape
distribution of structure formation simulations, we find that including
triaxiality cannot explain a population of massive, highly concentrated
clusters within the framework of LCDM, but easily explains rare cases of
apparently massive, highly concentrated, very efficient lensing clusters. Our
MCMC triaxial NFW fitting method is easily expandable to include constraints
from additional data types, and its application returns model parameters and
errors that more accurately capture the true (and limited) extent of our
knowledge of the structure of galaxy cluster lenses. (abridged)Comment: 18 pages, 15 figures. Updated to match published versio
A New Look at Massive Clusters: weak lensing constraints on the triaxial dark matter halos of Abell 1689, Abell 1835, & Abell 2204
Measuring the 3D distribution of mass on galaxy cluster scales is a crucial
test of the LCDM model, providing constraints on the nature of dark matter.
Recent work investigating mass distributions of individual galaxy clusters
(e.g. Abell 1689) using weak and strong gravitational lensing has revealed
potential inconsistencies between the predictions of structure formation models
relating halo mass to concentration and those relationships as measured in
massive clusters. However, such analyses employ simple spherical halo models
while a growing body of work indicates that triaxial 3D halo structure is both
common and important in parameter estimates. We recently introduced a Markov
Chain Monte Carlo (MCMC) method to fit fully triaxial models to weak lensing
data that gives parameter and error estimates that fully incorporate the true
shape uncertainty present in nature. In this paper we apply that method to weak
lensing data obtained with the ESO/MPG Wide-Field Imager for galaxy clusters
A1689, A1835, and A2204, under a range of Bayesian priors derived from theory
and from independent X-ray and strong lensing observations. For Abell 1689,
using a simple strong lensing prior we find marginalized mean parameter values
M_200 = (0.83 +- 0.16)x10^15 M_solar/h and C=12.2 +- 6.7, which are marginally
consistent with the mass-concentration relation predicted in LCDM. The large
error contours that accompany our triaxial parameter estimates more accurately
represent the true extent of our limited knowledge of the structure of galaxy
cluster lenses, and make clear the importance of combining many constraints
from other theoretical, lensing (strong, flexion), or other observational
(X-ray, SZ, dynamical) data to confidently measure cluster mass profiles.
(Abridged)Comment: 21 pages, 10 figures, accepted for publication in MNRA
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Loss of the PTCH1 tumor suppressor defines a new subset of plexiform fibromyxoma.
BackgroundPlexiform fibromyxoma (PF) is a rare gastric tumor often confused with gastrointestinal stromal tumor. These so-called "benign" tumors often present with upper GI bleeding and gastric outlet obstruction. It was recently demonstrated that approximately one-third of PF have activation of the GLI1 oncogene, a transcription factor in the hedgehog (Hh) pathway, via a MALAT1-GLI1 fusion protein or GLI1 up-regulation. Despite this discovery, the biology of most PFs remains unknown.MethodsNext generation sequencing (NGS) was performed on formalin-fixed paraffin-embedded (FFPE) samples of PF specimens collected from three institutions (UCSD, NCI and OHSU). Fresh frozen tissue from one tumor was utilized for in vitro assays, including quantitative RT-PCR and cell viability assays following drug treatment.ResultsEight patients with PF were identified and 5 patients' tumors were analyzed by NGS. An index case had a mono-allelic PTCH1 deletion of exons 15-24 and a second case, identified in a validation cohort, also had a PTCH1 gene loss associated with a suspected long-range chromosome 9 deletion. Building on the role of Hh signaling in PF, PTCH1, a tumor suppressor protein, functions upstream of GLI1. Loss of PTCH1 induces GLI1 activation and downstream gene transcription. Utilizing fresh tissue from the index PF case, RT-qPCR analysis demonstrated expression of Hh pathway components, SMO and GLI1, as well as GLI1 transcriptional targets, CCND1 and HHIP. In turn, short-term in vitro treatment with a Hh pathway inhibitor, sonidegib, resulted in dose-dependent cell killing.ConclusionsFor the first time, we report a novel association between PTCH1 inactivation and the development of plexiform fibromyxoma. Hh pathway inhibition with SMO antagonists may represent a target to study for treating a subset of plexiform fibromyxomas
Quadruplewild-type (WT) GIST: defining the subset of GIST that lacks abnormalities of KIT, PDGFRA, SDH, or RAS signaling pathways
A subset of GISTs lack mutations in the KIT/PDGFRA or RAS pathways and yet retain an intact succinate dehydrogensase (SDH) complex. We propose that these KIT/PDGFRA/SDH/RAS-P WT GIST tumors be designated as quadruple wild-type (WT) GIST. Further molecular and clinicophatological characterization of quadruple WT GIST will help to determine their prognosis as well as assist in the optimization of medical management, including clinical test of novel therapies
Exercise intensity and the protection from postprandial vascular dysfunction in adolescents
This is the author accepted manuscript. The final version is available from American Physiological Society via the DOI in this recordBACKGROUND: Acute exercise transiently improves endothelial function, and protects the vasculature from the deleterious effects of a high fat meal (HFM). We sought to identify whether this response is dependent on exercise intensity in adolescents. METHODS: Twenty adolescents (10 male, 14.3 ± 0.3 y) completed three 1-day trials: 1) rest (CON); 2) 8x1 min cycling at 90% peak power with 75s recovery (high-intensity interval exercise; HIIE); 3) cycling at 90% of the gas exchange threshold (moderate-intensity exercise; MIE) one hour before consuming a HFM (1.50 gâkg(-1) fat). Macrovascular and microvascular endothelial function were assessed before and immediately after exercise, and three hours after the HFM by flow mediated dilation (FMD) and laser Doppler imaging (peak reactive hyperaemia; PRH). RESULTS: FMD and PRH increased one hour after HIIE (P<0.001, ES=1.20 and P=0.048, ES=0.56) but were unchanged after MIE. FMD and PRH were attenuated three hours after the HFM in CON (P<0.001, ES=1.78 and P=0.02, ES=0.59). FMD remained greater three hours after the HFM in HIIE compared to MIE (P<0.001, ES=1.47) and CON (P<0.001, ES=2.54), and in MIE compared to CON (P<0.001, ES=1.40). Compared to CON, PRH was greater three hours after the HFM in HIIE (P=0.02, ES=0.71) and MIE (P=0.02, ES=0.84), with no differences between HIIE and MIE (P=0.72, ES=0.16). Plasma [triacylglycerol] and [total antioxidant status] were not different between trials. CONCLUSIONS: Exercise intensity plays an important role in protecting the vasculature from the deleterious effects of a HFM. Performing HIIE may provide superior vascular benefits than MIE in adolescent groups
A Simple Theory of Condensation
A simple assumption of an emergence in gas of small atomic clusters
consisting of particles each, leads to a phase separation (first order
transition). It reveals itself by an emergence of ``forbidden'' density range
starting at a certain temperature. Defining this latter value as the critical
temperature predicts existence of an interval with anomalous heat capacity
behaviour . The value suggested in literature
yields the heat capacity exponent .Comment: 9 pages, 1 figur
Cosmology with the cluster mass function: mass estimators and shape systematics in large weak lensing surveys
Accurate measurement of the cluster mass function is a crucial element in
efforts to constrain structure formation models, the normalisation of the
matter power spectrum and the cosmological matter density, and the nature and
evolution of dark energy. Large weak lensing surveys of ~20,000 galaxy clusters
and groups will be key tools in the observational pursuit of that goal. These
weak lensing studies often proceed by stacking the lensing signals of many
clusters and groups binned by mass-correlated observables such as richness and
luminosity; typically such analyses ignore the triaxial structure of dark
matter halos on the assumption that the averaging of many shear signals within
each mass bin makes its effects (as large as factors of two in mass model
parameter estimates from individual clusters) negligible. We test this
assumption and find that triaxiality can bias 3D virial mass estimates compared
to those for a spherical population by a few percent if suboptimal mass
estimators are used. This bias affects not only direct lensing constraints on
the mass function but can also affect the scatter and normalization of the
mass-observable relations derived from lensing that are so crucial to
constraining the cluster mass function with large samples. However, we
demonstrate that a careful choice of mass estimator can remove the bias very
effectively if the lensing signals from a sufficient number of triaxial halos
are averaged together, and further quantify that sufficient number for adequate
shape averaging. We thus show that by choosing observable bins to contain an
adequate number of halos and by utilizing a carefully chosen 3D mass estimator
stacked weak-lensing analyses can give unbiased constraints on the triaxial
mass function.Comment: 10 pages, 7 figures, accepted for publication in MNRA
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