179 research outputs found

    The XXL Survey X: K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies

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    We present the K-band luminosity-halo mass relation, LK,500M500,WLL_{K,500}-M_{500,WL}, for a subsample of 20 of the 100 brightest clusters in the XXL Survey observed with WIRCam at the Canada-France-Hawaii Telescope (CFHT). For the first time, we have measured this relation via weak-lensing analysis down to M500,WL=3.5×1013MM_{500,WL} =3.5 \times 10^{13}\,M_\odot. This allows us to investigate whether the slope of the LKML_K-M relation is different for groups and clusters, as seen in other works. The clusters in our sample span a wide range in mass, M500,WL=0.3512.10×1014MM_{500,WL} =0.35-12.10 \times 10^{14}\,M_\odot, at 0<z<0.60<z<0.6. The K-band luminosity scales as log10(LK,500/1012L)βlog10(M500,WL/1014M)\log_{10}(L_{K,500}/10^{12}L_\odot) \propto \beta log_{10}(M_{500,WL}/10^{14}M_\odot) with β=0.850.27+0.35\beta = 0.85^{+0.35}_{-0.27} and an intrinsic scatter of σlnLKM=0.370.17+0.19\sigma_{lnL_K|M} =0.37^{+0.19}_{-0.17}. Combining our sample with some clusters in the Local Cluster Substructure Survey (LoCuSS) present in the literature, we obtain a slope of 1.050.14+0.161.05^{+0.16}_{-0.14} and an intrinsic scatter of 0.140.07+0.090.14^{+0.09}_{-0.07}. The flattening in the LKML_K-M seen in previous works is not seen here and might be a result of a bias in the mass measurement due to assumptions on the dynamical state of the systems. We also study the richness-mass relation and find that group-sized halos have more galaxies per unit halo mass than massive clusters. However, the brightest cluster galaxy (BCG) in low-mass systems contributes a greater fraction to the total cluster light than BCGs do in massive clusters; the luminosity gap between the two brightest galaxies is more prominent for group-sized halos. This result is a natural outcome of the hierarchical growth of structures, where massive galaxies form and gain mass within low-mass groups and are ultimately accreted into more massive clusters to become either part of the BCG or one of the brighter galaxies. [Abridged]Comment: A&A, in pres

    An Investigation of Bilateral Symmetry During Manual Wheelchair Propulsion

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    Studies of manual wheelchair propulsion often assume bilateral symmetry to simplify data collection, processing and analysis. However, the validity of this assumption is unclear. Most investigations of wheelchair propulsion symmetry have been limited by a relatively small sample size and a focus on a single propulsion condition (e.g., level propulsion at self-selected speed). The purpose of this study was to evaluate bilateral symmetry during manual wheelchair propulsion in a large group of subjects across different propulsion conditions. Three-dimensional kinematics and handrim kinetics along with spatiotemporal variables were collected and processed from 80 subjects with paraplegia while propelling their wheelchairs on a stationary ergometer during three different conditions: level propulsion at their self-selected speed (free), level propulsion at their fastest comfortable speed (fast), and propulsion on an 8% grade at their level, self-selected speed (graded). All kinematic variables had significant side-to-side differences, primarily in the graded condition. Push angle was the only spatiotemporal variable with a significant side-to-side difference, and only during the graded condition. No kinetic variables had significant side-to-side differences. The magnitudes of the kinematic differences were low, with only one difference exceeding five degrees. With differences of such small magnitude, the bilateral symmetry assumption appears to be reasonable during manual wheelchair propulsion in subjects without significant upper-extremity pain or impairment. However, larger asymmetries may exist in individuals with secondary injuries and pain in their upper extremity and different etiologies of their neurological impairment

    Predicting temporary threshold shifts in a bottlenose dolphin (Tursiops truncatus) : the effects of noise level and duration

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    Author Posting. © Acoustical Society of America, 2009. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 125 (2009): 1816-1826, doi:10.1121/1.3068456.Noise levels in the ocean are increasing and are expected to affect marine mammals. To examine the auditory effects of noise on odontocetes, a bottlenose dolphin (Tursiops truncatus) was exposed to octave-band noise (4–8 kHz) of varying durations (<2–30 min) and sound pressures (130–178 dB re 1 µPa). Temporary threshold shift (TTS) occurrence was quantified in an effort to (i) determine the sound exposure levels (SELs) (dB re 1 µPa2 s) that induce TTS and (ii) develop a model to predict TTS onset. Hearing thresholds were measured using auditory evoked potentials. If SEL was kept constant, significant shifts were induced by longer duration exposures but not for shorter exposures. Higher SELs were required to induce shifts in shorter duration exposures. The results did not support an equal-energy model to predict TTS onset. Rather, a logarithmic algorithm, which increased in sound energy as exposure duration decreased, was a better predictor of TTS. Recovery to baseline hearing thresholds was also logarithmic (approximately −1.8 dB/doubling of time) but indicated variability including faster recovery rates after greater shifts and longer recoveries necessary after longer duration exposures. The data reflected the complexity of TTS in mammals that should be taken into account when predicting odontocete TTS.This work was funded by the Office of Naval Research Grant No. 00014-098-1-687 to P.E.N. and the support of Bob Gisiner and Mardi Hasting is noted. Additional support came from SeaSpace to T.A.M

    LoCuSS: Testing hydrostatic equilibrium in galaxy clusters

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    We test the assumption of hydrostatic equilibrium in an X-ray luminosity selected sample of 50 galaxy clusters at 0.15<z<0.30.15<z<0.3 from the Local Cluster Substructure Survey (LoCuSS). Our weak-lensing measurements of M500M_{500} control systematic biases to sub-4 per cent, and our hydrostatic measurements of the same achieve excellent agreement between XMM-Newton and Chandra. The mean ratio of X-ray to lensing mass for these 50 clusters is βX=0.95±0.05\beta_{\rm X}=0.95\pm0.05, and for the 44 clusters also detected by Planck, the mean ratio of Planck mass estimate to LoCuSS lensing mass is βP=0.95±0.04\beta_{\rm P}=0.95\pm0.04. Based on a careful like-for-like analysis, we find that LoCuSS, the Canadian Cluster Comparison Project (CCCP), and Weighing the Giants (WtG) agree on βP0.90.95\beta_{\rm P}\simeq0.9-0.95 at 0.15<z<0.30.15<z<0.3. This small level of hydrostatic bias disagrees at 5σ\sim5\sigma with the level required to reconcile Planck cosmology results from the cosmic microwave background and galaxy cluster counts

    Fixation of the Cemented Stem: Clinical Relevance of the Porosity and Thickness of the Cement Mantle

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    The aim of this review paper is to define the fixation of the cemented stem. Polymethyl methacrylate, otherwise known as “bone cement”, has been used in the fixation of hip implants since the early 1960s. Sir John Charnley, the pioneer of modern hip replacement, incorporated the use of cement in the development of low frictional torque hip arthroplasty. In this paper, the concepts of femoral stem design and fixation, clinical results, and advances in understanding of the optimal use of cement are reviewed. The purpose of this paper is to help understanding and discussions on the thickness and the porosity of the cement mantle in total hip arthroplasty. Cement does not act as an adhesive, as sometimes thought, but relies on an interlocking fit to provide mechanical stability at the cement–bone interface, while at the prosthesis– cement interface it achieves stability by optimizing the fit of the implant in the cement mantle, such as in a tapered femoral stem

    Complications and pitfalls of lumbar interlaminar and transforaminal epidural injections

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    Lumbar interlaminar and transforaminal epidural injections are used in the treatment of lumbar radicular pain and other lumbar spinal pain syndromes. Complications from these procedures arise from needle placement and the administration of medication. Potential risks include infection, hematoma, intravascular injection of medication, direct nerve trauma, subdural injection of medication, air embolism, disc entry, urinary retention, radiation exposure, and hypersensitivity reactions. The objective of this article is to review the complications of lumbar interlaminar and transforaminal epidural injections and discuss the potential pitfalls related to these procedures. We performed a comprehensive literature review through a Medline search for relevant case reports, clinical trials, and review articles. Complications from lumbar epidural injections are extremely rare. Most if not all complications can be avoided by careful technique with accurate needle placement, sterile precautions, and a thorough understanding of the relevant anatomy and contrast patterns on fluoroscopic imaging

    Adverse Drug Reactions in Children—A Systematic Review

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    Adverse drug reactions in children are an important public health problem. We have undertaken a systematic review of observational studies in children in three settings: causing admission to hospital, occurring during hospital stay and occurring in the community. We were particularly interested in understanding how ADRs might be better detected, assessed and avoided

    “The world around me”: The environment and single women

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    The “environment” has often been taken as a backdrop for feminist research and theory, as a setting within which issues of feminist concern are played out. This environment, however, is not a neutral setting; rather, research over the past 15 years has evidenced the assumptions about “a woman's place” as a man's wife literally built into women's worlds. Space speaks, and the stories it tells center around particular and identifiable assumptions about gender and where a woman “should” be, when, and with whom. Unmarried women are in a unique position in this environment: they are subjected not only to the economic disadvantages and social subjugation of being a woman, but also to the social and economic drawbacks of being single in a couple-oriented society and in an environment they see as not built for them. Although research exists on the sexism in the physical environment, on women's economic and social position, and on singlehood, a need exists to bridge these areas to explore how single women experience their singlehood, their womanhood, and the environment in their everyday lives and decision making. I conducted in-depth interviews with 25 single women, 23 white and 2 African-American women, about their experiences of living single. This article, based on the results of those interviews and a series of focus group discussions, examines how single women negotiate and respond to their necessary environmental decisions about housing, transportation, and leisure activities in an environment not likely to be conducive to their ways of life.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45605/1/11199_2005_Article_BF01544591.pd
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