5,926 research outputs found

    An XMM and Chandra view of massive clusters of galaxies to z=1

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    The X-ray properties of a sample of high redshift (z>0.6), massive clusters observed with XMM-Newton and Chandra are described, including two exceptional systems. One, at z=0.89, has an X-ray temperature of T=11.5 (+1.1, -0.9) keV (the highest temperature of any cluster known at z>0.6), an estimated mass of (1.4+/-0.2)x10^15 solar masses and appears relaxed. The other, at z=0.83, has at least three sub-clumps, probably in the process of merging, and may also show signs of faint filamentary structure at large radii,observed in X-rays. In general there is a mix of X-ray morphologies, from those clusters which appear relaxed and containing little substructure to some highly non-virialized and probably merging systems. The X-ray gas metallicities and gas mass fractions of the relaxed systems are similar to those of low redshift clusters of the same temperature, suggesting that the gas was in place, and containing its metals, by z=0.8. The evolution of the mass-temperature relation may be consistent with no evolution or with the ``late formation'' assumption. The effect of point source contamination in the ROSAT survey from which these clusters were selected is estimated, and the implications for the ROSAT X-ray luminosity function discussed.Comment: 9 pages, in Carnegie Observatories Astrophysics Series, Vol. 3: Clusters of Galaxies: Probes of Cosmological Structure and Galaxy Evolution, ed. J. S. Mulchaey, A. Dressler, and A. Oemler. See http://www.ociw.edu/ociw/symposia/series/symposium3/proceedings.html for a full-resolution versio

    Measuring Accuracy of Automated Parsing and Categorization Tools and Processes in Digital Investigations

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    This work presents a method for the measurement of the accuracy of evidential artifact extraction and categorization tasks in digital forensic investigations. Instead of focusing on the measurement of accuracy and errors in the functions of digital forensic tools, this work proposes the application of information retrieval measurement techniques that allow the incorporation of errors introduced by tools and analysis processes. This method uses a `gold standard' that is the collection of evidential objects determined by a digital investigator from suspect data with an unknown ground truth. This work proposes that the accuracy of tools and investigation processes can be evaluated compared to the derived gold standard using common precision and recall values. Two example case studies are presented showing the measurement of the accuracy of automated analysis tools as compared to an in-depth analysis by an expert. It is shown that such measurement can allow investigators to determine changes in accuracy of their processes over time, and determine if such a change is caused by their tools or knowledge.Comment: 17 pages, 2 appendices, 1 figure, 5th International Conference on Digital Forensics and Cyber Crime; Digital Forensics and Cyber Crime, pp. 147-169, 201

    Acidification effects on biofouling communities: winners and losers

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    How ocean acidification affects marine life is a major concern for science and society. However, its impacts on encrusting biofouling communities, that are both the initial colonizers of hard substrata and of great economic importance, are almost unknown. We showed that community composition changed significantly, from 92% spirorbids, 3% ascidians and 4% sponges initially to 47% spirorbids, 23% ascidians and 29% sponges after 100days in acidified conditions (pH 7.7). In low pH, numbers of the spirorbid Neodexiospira pseudocorrugata were reduced x5 compared to controls. The two ascidians present behaved differently with Aplidium sp. decreasing x10 in pH 7.7, whereas Molgula sp. numbers were x4 higher in low pH than controls. Calcareous sponge (Leucosolenia sp.) numbers increased x2.5 in pH 7.7 over controls. The diatom and filamentous algal community was also more poorly developed in the low pH treatments compared to controls. Colonization of new surfaces likewise showed large decreases in spirorbid numbers, but numbers of sponges and Molgula sp. increased. Spirorbid losses appeared due to both recruitment failure and loss of existing tubes. Spirorbid tubes are comprised of a loose prismatic fabric of calcite crystals. Loss of tube materials appeared due to changes in the binding matrix and not crystal dissolution, as SEM analyses showed crystal surfaces were not pitted or dissolved in low pH conditions. Biofouling communities face dramatic future changes with reductions in groups with hard exposed exoskeletons and domination by soft-bodied ascidians and sponges.EU [227799, 00415/2010]; Natural Environment Research Council [bas0100036, bas0100025

    First GIS analysis of modern stone tools used by wild chimpanzees (Pan troglodytes verus) in Bossou, Guinea, West Africa

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    Stone tool use by wild chimpanzees of West Africa offers a unique opportunity to explore the evolutionary roots of technology during human evolution. However, detailed analyses of chimpanzee stone artifacts are still lacking, thus precluding a comparison with the earliest archaeological record. This paper presents the first systematic study of stone tools used by wild chimpanzees to crack open nuts in Bossou (Guinea-Conakry), and applies pioneering analytical techniques to such artifacts. Automatic morphometric GIS classification enabled to create maps of use wear over the stone tools (anvils, hammers, and hammers/anvils), which were blind tested with GIS spatial analysis of damage patterns identified visually. Our analysis shows that chimpanzee stone tool use wear can be systematized and specific damage patterns discerned, allowing to discriminate between active and passive pounders in lithic assemblages. In summary, our results demonstrate the heuristic potential of combined suites of GIS techniques for the analysis of battered artifacts, and have enabled creating a referential framework of analysis in which wild chimpanzee battered tools can for the first time be directly compared to the early archaeological record.Leverhulme Trust [IN-052]; MEXT [20002001, 24000001]; JSPS-U04-PWS; FCT-Portugal [SFRH/BD/36169/2007]; Wenner-Gren Foundation for Anthropological Researc

    Use of medications by people with chronic fatigue syndrome and healthy persons: a population-based study of fatiguing illness in Georgia

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    <p>Abstract</p> <p>Background</p> <p>Chronic fatigue syndrome (CFS) is a debilitating condition of unknown etiology and no definitive pharmacotherapy. Patients are usually prescribed symptomatic treatment or self-medicate. We evaluated prescription and non-prescription drug use among persons with CFS in Georgia and compared it to that in non-fatigued <it>Well </it>controls and also to chronically <it>Unwell </it>individuals not fully meeting criteria for CFS.</p> <p>Methods</p> <p>A population-based, case-control study. To identify persons with possible CFS-like illness and controls, we conducted a random-digit dialing telephone screening of 19,807 Georgia residents, followed by a detailed telephone interview of 5,630 to identify subjects with CFS-like illness, other chronically <it>Unwell</it>, and <it>Well </it>subjects. All those with CFS-like illness (n = 469), a random sample of chronically <it>Unwell </it>subjects (n = 505), and <it>Well </it>individuals (n = 641) who were age-, sex-, race-, and geographically matched to those with CFS-like illness were invited for a clinical evaluation and 783 participated (48% overall response rate). Clinical evaluation identified 113 persons with CFS, 264 <it>Unwell </it>subjects with insufficient symptoms for CFS (named ISF), and 124 <it>Well </it>controls; the remaining 280 subjects had exclusionary medical or psychiatric conditions, and 2 subjects could not be classified. Subjects were asked to bring all medications taken in the past 2 weeks to the clinic where a research nurse viewed and recorded the name and the dose of each medication.</p> <p>Results</p> <p>More than 90% of persons with CFS used at least one drug or supplement within the preceding two weeks. Among users, people with CFS used an average of 5.8 drugs or supplements, compared to 4.1 by ISF and 3.7 by <it>Well </it>controls. Persons with CFS were significantly more likely to use antidepressants, sedatives, muscle relaxants, and anti-acids than either <it>Well </it>controls or the ISF group. In addition, persons with CFS were significantly more likely to use pain-relievers, anti-histamines and cold/sinus medications than were <it>Well </it>controls.</p> <p>Conclusion</p> <p>Medical care providers of patients with chronic fatigue syndrome should be aware of polypharmacy as a problem in such patients, and the related potential iatrogenic effects and drug interactions.</p

    Patterns and Predictors of Relapse Following Radical Chemoradiation Therapy Delivered Using Intensity Modulated Radiation Therapy With a Simultaneous Integrated Boost in Anal Squamous Cell Carcinoma

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    Purpose: To describe the patterns and predictors of treatment failure in patients receiving definitive chemoradiotherapy (CRT) for anal squamous cell carcinoma (ASCC), delivered using intensity modulated radiotherapy (IMRT). Materials and methods: A retrospective cohort analysis of consecutive patients treated with curative intent for ASCC using CRT delivered with a standardised IMRT technique in five UK cancer centres. Patients were included from the start of UK IMRT guidance in February 2013 to 31st October 2017. Collected data included baseline demographics, treatment details, tumour control, sites of relapse and overall survival. Statistical analysis to calculate outcomes and predictive factors for outcome measures were performed using SPSS and R. Results: The medical records of 385 consecutive patients were analysed. Median follow-up was 24.0 months. 86.7% of patients achieved a complete response (CR) within 6 months of completing chemoradiotherapy. 3yr disease free survival (DFS) and overall survival (OS) were 75.6% and 85.6% respectively. Of all relapses, 83.4% occurred at the site of primary disease. There were two isolated relapses in regional nodes not involved at outset. Predictive factors for cancer recurrence included male sex, high N-stage and failure to complete radiotherapy as planned. Conclusions: The treatment results compare favourably to published outcomes from similar cohorts using 3D conformal CRT. The observed patterns of failure support the current UK IMRT voluming guidelines and dose levels, highlighting our prophylactic nodal dose is sufficient to prevent isolated regional relapse in uninvolved nodes. Further investigation into strategies to optimise CR should remain a priority in ASCC, as the site of primary disease remains the overwhelming site of relapse

    A single sub-km Kuiper Belt object from a stellar Occultation in archival data

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    The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects (KBOs). Small, sub-km sized, KBOs elude direct detection, but the signature of their occultations of background stars should be detectable. Observations at both optical and X-ray wavelengths claim to have detected such occultations, but their implied KBO abundances are inconsistent with each other and far exceed theoretical expectations. Here, we report an analysis of archival data that reveals an occultation by a body with a 500 m radius at a distance of 45 AU. The probability of this event to occur due to random statistical fluctuations within our data set is about 2%. Our survey yields a surface density of KBOs with radii larger than 250 m of 2.1^{+4.8}_{-1.7} x 10^7 deg^{-2}, ruling out inferred surface densities from previous claimed detections by more than 5 sigma. The fact that we detected only one event, firmly shows a deficit of sub-km sized KBOs compared to a population extrapolated from objects with r>50 km. This implies that sub-km sized KBOs are undergoing collisional erosion, just like debris disks observed around other stars.Comment: To appear in Nature on December 17, 2009. Under press embargo until 1800 hours London time on 16 December. 19 pages; 7 figure
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