2,958 research outputs found
Constraints on Dark Energy from Supernovae, Gamma Ray Bursts, Acoustic Oscillations, Nucleosynthesis and Large Scale Structure and the Hubble constant
The luminosity distance vs. redshift law is now measured using supernovae and
gamma ray bursts, and the angular size distance is measured at the surface of
last scattering by the CMB and at z = 0.35 by baryon acoustic oscillations. In
this paper this data is fit to models for the equation of state with w = -1, w
= const, and w(z) = w_0+w_a(1-a). The last model is poorly constrained by the
distance data, leading to unphysical solutions where the dark energy dominates
at early times unless the large scale structure and acoustic scale constraints
are modified to allow for early time dark energy effects. A flat LambdaCDM
model is consistent with all the data.Comment: 19 pages Latex with 8 Postscript figure files. A new reference and
constraint, w vs w' contour plots updated. Version accepted by the the Ap
Evolution of the Cluster X-ray Luminosity Function
We report measurements of the cluster X-ray luminosity function out to z=0.8
based on the final sample of 201 galaxy systems from the 160 Square Degree
ROSAT Cluster Survey. There is little evidence for any measurable change in
cluster abundance out to z~0.6 at luminosities less than a few times 10^44
ergs/s (0.5-2.0 keV). However, between 0.6 < z < 0.8 and at luminosities above
10^44 ergs/s, the observed volume densities are significantly lower than those
of the present-day population. We quantify this cluster deficit using
integrated number counts and a maximum-likelihood analysis of the observed
luminosity-redshift distribution fit with a model luminosity function. The
negative evolution signal is >3 sigma regardless of the adopted local
luminosity function or cosmological framework. Our results and those from
several other surveys independently confirm the presence of evolution. Whereas
the bulk of the cluster population does not evolve, the most luminous and
presumably most massive structures evolve appreciably between z=0.8 and the
present. Interpreted in the context of hierarchical structure formation, we are
probing sufficiently large mass aggregations at sufficiently early times in
cosmological history where the Universe has yet to assemble these clusters to
present-day volume densities.Comment: 15 pages, 10 figures, accepted for publication in Ap
Men, Muscles, and Body Image: Comparisons of Competitive Bodybuilders, Weight Trainers, and Athletically Active Controls
Objectives: To investigate body image and psychosocial adjustment among competitive bodybuilders, non-competitive weight trainers, and athletically active men. Methods: Participants were 40 men in each of the three groups who were assessed on body composition and multiple facets of body image evaluation, investment and anxiety, eating attitudes, and social self esteem. Results: Relative to the other two groups, competitive bodybuilders had greater body mass due to fat-free body mass. Although groups did not differ in their situational body image discomfort, competitive bodybuilders and weight trainers had a more positive global appearance evaluation and were more psychologically invested in their physical appearance. Compared with active controls, men in both weightlifting groups were more satisfied with their upper torso and muscle tone. Competitive bodybuilders reported more mid torso satisfaction than the other two groups. Competitive bodybuilders also wished to be significantly heavier than controls did and reported higher social self esteem but greater eating disturbance. Conclusions: The findings suggest that competitive bodybuilders as a group are not more muscle dysmorphic\u27\u27 than either non-competitive weight trainers or physically active men who do not train with weights
The Discovery of Argon in Comet C/1995 O1 (Hale-Bopp)
On 30.14 March 1997 we observed the EUV spectrum of the bright comet C/1995
O1 (Hale-Bopp) at the time of its perihelion, using our EUVS sounding rocket
telescope/spectrometer. The spectra reveal the presence H Ly beta, O+, and,
most notably, Argon. Modelling of the retrieved Ar production rates indicates
that comet Hale-Bopp is enriched in Ar relative to cosmogonic expectations.
This in turn indicates that Hale-Bopp's deep interior has never been exposed to
the 35-40 K temperatures necessary to deplete the comet's primordial argon
supply.Comment: 9 pages, 2 figures. ApJ, 545, in press (2000
The TREC2001 video track: information retrieval on digital video information
The development of techniques to support content-based access to archives of digital video information has recently started to receive much attention from the research community. During 2001, the annual TREC activity, which has been benchmarking the performance of information retrieval techniques on a range of media for 10 years, included a ”track“ or activity which allowed investigation into approaches to support searching through a video library. This paper is not intended to provide a comprehensive picture of the different approaches taken by the TREC2001 video track participants but instead we give an overview of the TREC video search task and a thumbnail sketch of the approaches taken by different groups. The reason for writing this paper is to highlight the message from the TREC video track that there are now a variety of approaches available for searching and browsing through digital video archives, that these approaches do work, are scalable to larger archives and can yield useful retrieval performance for users. This has important implications in making digital libraries of video information attainable
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Loss of the Birt–Hogg–Dubé tumor suppressor results in apoptotic resistance due to aberrant TGFβ-mediated transcription
Birt–Hogg–Dubé (BHD) syndrome is an inherited cancer susceptibility disease characterized by skin and kidney tumors, as well as cystic lung disease, which results from loss-of-function mutations in the BHD gene. BHD is also inactivated in a significant fraction of patients with sporadic renal cancers and idiopathic cystic lung disease, and little is known about its mode of action. To investigate the molecular and cellular basis of BHD tumor suppressor activity, we generated mutant Bhd mice and embryonic stem cell lines. BHD-deficient cells exhibited defects in cell-intrinsic apoptosis that correlated with reduced expression of the BH3-only protein Bim, which was similarly observed in all human and murine BHD-related tumors examined. We further demonstrate that Bim deficiency in Bhd−/− cells is not a consequence of elevated mTOR or ERK activity, but results instead from reduced Bim transcription associated with a general loss of TGFβ-mediated transcription and chromatin modifications. In aggregate, this work identifies a specific tumor suppressive mechanism for BHD in regulating TGFβ-dependent transcription and apoptosis, which has implications for the development of targeted therapies
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Assessment of the potential for ferrocyanide propagating reaction accidents
This report contains safety criteria for the storage of ferrocyanide bearing waste sludges in Hanford underground waste storage tanks. In addition, the tank wastes are categorized with this criteria into SAFE, CONDITIONALLY SAFE, and UNSAFE categories based on available historical records and sample information. Fourteen (14) tanks are classified as CONDITIONALLY SAFE, while four (4) C-Farm tanks are categorized as SAFE. This report therefore provides a technical basis to resolve the ferrocyanide safety issue for these four tanks and supports their removal from the Watch List. The 14 CONDITIONALLY SAFE tanks will be re-evaluated in a future revision to this report as representative sample data becomes available. It is anticipated that the 14 tanks will be re-categorized as SAFE at that time
Spatial Correlation Function of X-ray Selected AGN
We present a detailed description of the first direct measurement of the
spatial correlation function of X-ray selected AGN. This result is based on an
X-ray flux-limited sample of 219 AGN discovered in the contiguous 80.7 deg^2
region of the ROSAT North Ecliptic Pole (NEP) Survey. Clustering is detected at
the 4 sigma level at comoving scales in the interval r = 5-60 h^-1 Mpc. Fitting
the data with a power law of slope gamma=1.8, we find a correlation length of
r_0 = 7.4 (+1.8, -1.9) h^-1 Mpc (Omega_M=0.3, Omega_Lambda=0.7). The median
redshift of the AGN contributing to the signal is z_xi=0.22. This clustering
amplitude implies that X-ray selected AGN are spatially distributed in a manner
similar to that of optically selected AGN. Furthermore, the ROSAT NEP
determination establishes the local behavior of AGN clustering, a regime which
is poorly sampled in general. Combined with high-redshift measures from optical
studies, the ROSAT NEP results argue that the AGN correlation strength
essentially does not evolve with redshift, at least out to z~2.2. In the local
Universe, X-ray selected AGN appear to be unbiased relative to galaxies and the
inferred X-ray bias parameter is near unity, b_X~1. Hence X-ray selected AGN
closely trace the underlying mass distribution. The ROSAT NEP AGN catalog,
presented here, features complete optical identifications and spectroscopic
redshifts. The median redshift, X-ray flux, and X-ray luminosity are z=0.41,
f_X=1.1*10^-13 cgs, and L_X=9.2*10^43 h_70^-2 cgs (0.5-2.0 keV), respectively.
Unobscured, type 1 AGN are the dominant constituents (90%) of this soft X-ray
selected sample of AGN.Comment: 17 pages, 8 figures, accepted for publication in ApJ, a version with
high-resolution figures is available at
http://www.eso.org/~cmullis/papers/Mullis_et_al_2004b.ps.gz, a
machine-readable version of the ROSAT NEP AGN catalog is available at
http://www.eso.org/~cmullis/research/nep-catalog.htm
The Lick Planet Search: Detectability and Mass Thresholds
We analyse 11 years of precise radial velocities for 76 solar type stars from
the Lick survey. Eight stars in this sample have previously reported
planetary-mass companions, all with mass (m sin i) less than 8 Jupiter masses
(MJ). For the stars without a detected companion, we place upper limits on
possible companion mass. For most stars, we can exclude companions with m sin i
> 0.7 MJ (a/AU)^1/2 for orbital radii a < 5 AU.
We use our results to interpret the observed masses and orbital radii of
planetary-mass companions. For example, we show that the finite duration of the
observations makes detection of Jupiter mass companions more and more difficult
for orbital radii beyond 3 AU. Thus it is possible that the majority of solar
type stars harbor Jupiter-mass companions much like our own, and if so these
companions should be detectable in a few years.
To search for periodicities, we adopt a "floating-mean" periodogram, which
improves on the traditional Lomb-Scargle periodogram by accounting for
statistical fluctuations in the mean of a sampled sinusoid. We discuss in
detail the normalization of the periodogram, an issue which has been of some
debate in the literature.Comment: To appear in the Astrophysical Journal (50 pages, LaTeX, including 11
figures
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