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Search Results: 1 - 10 of 385391 matches for " C. L. Jones "
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Simulation of the SONGS Reactor Antineutrino Flux Using DRAGON
C. L. Jones
Physics , 2011,
Abstract: For reactor antineutrino experiments, a thorough understanding of the fuel composition and isotopic evolution is of paramount importance for the extraction of $\theta_{13}$. To accomplish these goals, we employ the deterministic lattice code DRAGON, and analyze the instantaneous antineutrino rate from the San Onofre Nuclear Generating Station (SONGS) Unit 2 reactor in California. DRAGON's ability to predict the rate for two consecutive fuel cycles is examined.
Barriers and facilitators to an outreach rehabilitation program delivered in nursing homes after hip fracture surgical repair  [PDF]
Donna M. Wilson, Sandra L. Robertson, C. Allyson Jones, D. W. C. Johnston, Lauren A. Beaupre
Advances in Aging Research (AAR) , 2013, DOI: 10.4236/aar.2013.21006
Abstract:

Objective: To identify and understand facilitators and barriers to implementing an Outreach rehabilitation program designed to improve post-operative recovery following hip fracture in long-term care residents. Residents of nursing home facilities are at considerable risk of hip fracture and minimal recovery following a hip fracture. Methods: Data were gathered over June-August, 2012 through semi-structured interviews or focus groups. Fifteen persons (n = 15) who were members of the Outreach rehabilitation team (n = 8) or relevant nursing home staff (n = 7) were interviewed. Data analysis was guided by principles of grounded theory method. Findings: Three major themes that contributed to or hindered the Outreach rehabilitation program emerged, namely, 1) the division, the separate operation and delivery of rehabilitation services; 2) building bridges, or negotiating ways to communicate and work together, and 3) strength in the structure, the acceptance of the program and the perceived benefits of the program. One main challenge to program implementation con- cerned coordinating additional rehabilitation with the rehabilitation provided within the nursing homes. Facility staff was largely unaware of the program and were unprepared to work with Outreach team members. As the program progressed, the facility staff and Outreach team were able to collaborate to overcome resident health issues impeding recovery such as cognitive impairment, language barriers and post-surgical pain control needs. Facilitators included the consistency of Outreach team members and accessible facility staff, which contributed to effective communication and trust between the Outreach team and facility staff. Facilitators also included support for the program by the Outreach team and facility staff, as well

Contact Toxicity and Residual Efficacy of Indoxacarb against the European Earwig (Dermaptera: Forficulidae)
Susan C. Jones,Joshua L. Bryant
Insects , 2012, DOI: 10.3390/insects3030593
Abstract: Indoxacarb (Arilon 20WG) was evaluated against a nuisance pest, the European earwig ( Forficula auricularia), and was found to be an effective contact toxicant with residual activity on substrates commonly encountered in urban environments. Within 16 h of being directly sprayed with indoxacarb, ≥90% of earwigs from two populations were either ataxic, moribund, or dead, and 100% displayed these symptoms of severe intoxication at 1 d. Brief exposure (5 min or 1 h) to dried residues on either a porous (pine wood) or non-porous (ceramic tile) substrate also was sufficient to cause severe intoxication of earwigs within 1 d. In all bioassays, indoxacarb-treated earwigs showed no signs of recovery during the 21-d observation period. In outdoor urban habitats, intoxicated earwigs would be more vulnerable to desiccation, predation, or pathogens leading to higher mortality than in a laboratory setting.
Prolonged N-acetylcysteine therapy in late acetaminophen poisoning associated with acute liver failure – a need to be more cautious?
T Nimmi C Athuraliya, Alison L Jones
Critical Care , 2009, DOI: 10.1186/cc7800
Abstract: The paper entitled 'Prolonged treatment with N-acetylcysteine delays liver recovery from acetaminophen hepatotoxicity' by Yang and colleagues [1], published in the previous issue of Critical Care, demonstrates that prolonged administration of N-acetylcysteine (NAC) at 100 mg/kg in acetaminophen (APAP)-induced liver failure in mice potentially limits hepatocellular regeneration. Activation of a transcription factor, nuclear factor-kappa-B (NF-κB), strongly linked to impairment of liver regeneration, is a putative mechanism for this. Furthermore, the paper postulates that high doses of NAC may interfere with normal metabolic processes of the liver, leading to impairment of its regenerative capacity [1].NAC has been used since the 1970s, and it effectively manages APAP poisoning by glutathione repletion if administered within 8 to 10 hours of ingestion of the overdose [2]. In later years, clinical use of NAC was extended to patients who present more than 10 hours after ingestion and to those with APAP-induced acute liver failure (ALF), and patients in such categories are routinely on NAC infusions for many days, even weeks [3,4]. The putative protective mechanisms of NAC in late-APAP poisoning and APAP-induced liver failure remain poorly characterised but include free-radical scavenging, hemodynamic, and cytokine effects [1,5,6]. Concern has been expressed relating to its extended use in late presenters with APAP poisoning and APAP-induced liver failure because of the possibility of changed kinetics of NAC in liver injury, reduced efficacy, and adverse hemodynamic changes (vasodilatation and increased cardiac index) [7]. This new study raises the issue of whether impairment of regeneration is also a clinical concern for extended NAC use.A key issue in liver recovery after any acute injury is tissue repair and regeneration. Such liver regeneration involves replication of mature parenchyma and non-parenchyma liver cells, which requires multiple cytokine and growth factor
The ILIUM forward modelling algorithm for multivariate parameter estimation and its application to derive stellar parameters from Gaia spectrophotometry
C. A. L. Bailer-Jones
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.16125.x
Abstract: I introduce an algorithm for estimating parameters from multidimensional data based on forward modelling. In contrast to many machine learning approaches it avoids fitting an inverse model and the problems associated with this. The algorithm makes explicit use of the sensitivities of the data to the parameters, with the goal of better treating parameters which only have a weak impact on the data. The forward modelling approach provides uncertainty (full covariance) estimates in the predicted parameters as well as a goodness-of-fit for observations. I demonstrate the algorithm, ILIUM, with the estimation of stellar astrophysical parameters (APs) from simulations of the low resolution spectrophotometry to be obtained by Gaia. The AP accuracy is competitive with that obtained by a support vector machine. For example, for zero extinction stars covering a wide range of metallicity, surface gravity and temperature, ILIUM can estimate Teff to an accuracy of 0.3% at G=15 and to 4% for (lower signal-to-noise ratio) spectra at G=20. [Fe/H] and logg can be estimated to accuracies of 0.1-0.4dex for stars with G<=18.5. If extinction varies a priori over a wide range (Av=0-10mag), then Teff and Av can be estimated quite accurately (3-4% and 0.1-0.2mag respectively at G=15), but there is a strong and ubiquitous degeneracy in these parameters which limits our ability to estimate either accurately at faint magnitudes. Using the forward model we can map these degeneracies (in advance), and thus provide a complete probability distribution over solutions. (Abridged)
The evidence for and against astronomical impacts on climate change and mass extinctions: A review
C. A. L. Bailer-Jones
Physics , 2009, DOI: 10.1017/S147355040999005X
Abstract: Numerous studies over the past 30 years have suggested there is a causal connection between the motion of the Sun through the Galaxy and terrestrial mass extinctions or climate change. Proposed mechanisms include comet impacts (via perturbation of the Oort cloud), cosmic rays and supernovae, the effects of which are modulated by the passage of the Sun through the Galactic midplane or spiral arms. Supposed periodicities in the fossil record, impact cratering dates or climate proxies over the Phanerozoic (past 545 Myr) are frequently cited as evidence in support of these hypotheses. This remains a controversial subject, with many refutations and replies having been published. Here I review both the mechanisms and the evidence for and against the relevance of astronomical phenomena to climate change and evolution. This necessarily includes a critical assessment of time series analysis techniques and hypothesis testing. Some of the studies have suffered from flaws in methodology, in particular drawing incorrect conclusions based on ruling out a null hypothesis. I conclude that there is little evidence for intrinsic periodicities in biodiversity, impact cratering or climate on timescales of tens to hundreds of Myr. Furthermore, Galactic midplane and spiral arm crossings seem to have little or no impact on biological or climate variation above background level. (truncated)
The K Band Luminosity Function of High Redshift Clusters
S. C. Ellis,L. R. Jones
Physics , 2003,
Abstract: K band observations of the galaxy populations of three high redshift (z=0.8-1.0), X-ray selected, massive clusters are presented. The observations reach a depth of K = 21.5, corresponding to K*+3.5 mag. The evolution of the galaxy properties are discussed in terms of their K band luminosity functions and the K band Hubble diagram of brightest cluster galaxies. The bulk of the galaxies, as characterised by the parameter K* from the Schechter (1976) function, are found to be consistent with passive evolution with a redshift of formation of z_f = 1.5-2. This is in agreement with observations of other high redshift clusters, but in disagreement with field galaxies at similar redshifts. The shape of the luminosity function at high redshift, after correcting for passive evolution, is not significantly different from that of the Coma cluster, again consistent with passive evolution.
Determination of stellar parameters with GAIA
C. A. L. Bailer-Jones
Physics , 2002, DOI: 10.1023/A:1015527705755
Abstract: The GAIA Galactic survey satellite will obtain photometry in 15 filters of over 10^9 stars in our Galaxy across a very wide range of stellar types. No other planned survey will provide so much photometric information on so many stars. I examine the problem of how to determine fundamental physical parameters (Teff, log g, [Fe/H] etc.) from these data. Given the size, multidimensionality and diversity of this dataset, this is a challenging task beyond any encountered so far in large-scale stellar parametrization. I describe the problems faced (initial object identification, interstellar extinction, multiplicity, missing data etc.) and present a framework in which they can can be addressed. A probabilistic approach is advocated on the grounds that it can take advantage of additional information (e.g. priors and data uncertainties) in a consistent and useful manner, as well as give meaningful results in the presence of poor or degenerate data. Furthermore, I suggest an approach to parametrization which can use the other information GAIA will acquire, in particular the parallax, which has not previously been available for large-scale multidimensional parametrization. Several of the problems identified and ideas suggested will be relevant to other large surveys, such as SDSS, DIVA, FAME, VISTA and LSST, as well as stellar parametrization in a virtual observatory.
Close encounters of the stellar kind
C. A. L. Bailer-Jones
Physics , 2014, DOI: 10.1051/0004-6361/201425221
Abstract: Stars which pass close to the Sun can perturb the Oort cloud, injecting comets into the inner solar system where they may collide with the Earth. Using van Leeuwen's re-reduction of the Hipparcos data complemented by the original Hipparcos and Tycho-2 catalogues, along with recent radial velocity surveys, I integrate the orbits of over 50 000 stars through the Galaxy to look for close encounters. The search uses a Monte Carlo simulation over the covariance of the data in order to properly characterize the uncertainties in the times, distances, and speeds of the encounters. I show that modelling stellar encounters by assuming instead a linear relative motion produces, for many encounters, inaccurate and biased results. I find 42, 14, and 4 stars which have encounter distances below 2, 1, and 0.5 pc respectively, although some of these stars have questionable data. Of the 14 stars coming within 1 pc, 5 were found by at least one of three previous studies (which found a total of 7 coming within 1 pc). The closest encounter appears to be Hip 85605, a K or M star, which has a 90% probability of coming between 0.04 and 0.20 pc between 240 and 470 kyr from now (90% Bayesian confidence interval). However, its astrometry may be incorrect, in which case the closest encounter found is the K7 dwarf GL 710, which has a 90% probability of coming within 0.10-0.44 pc in about 1.3 Myr. A larger perturbation may have been caused by gamma Microscopii, a G6 giant with a mass of about 2.5 Msol, which came within 0.35-1.34 pc (90% confidence interval) around 3.8 Myr ago.
Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry
C. A. L. Bailer-Jones
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17699.x
Abstract: Astrometric surveys provide the opportunity to measure the absolute magnitudes of large numbers of stars, but only if the individual line-of-sight extinctions are known. Unfortunately, extinction is highly degenerate with stellar effective temperature when estimated from broad band optical/infrared photometry. To address this problem, I introduce a Bayesian method for estimating the intrinsic parameters of a star and its line-of-sight extinction. It uses both photometry and parallaxes in a self-consistent manner in order to provide a non-parametric posterior probability distribution over the parameters. The method makes explicit use of domain knowledge by employing the Hertzsprung--Russell Diagram (HRD) to constrain solutions and to ensure that they respect stellar physics. I first demonstrate this method by using it to estimate effective temperature and extinction from BVJHK data for a set of artificially reddened Hipparcos stars, for which accurate effective temperatures have been estimated from high resolution spectroscopy. Using just the four colours, we see the expected strong degeneracy (positive correlation) between the temperature and extinction. Introducing the parallax, apparent magnitude and the HRD reduces this degeneracy and improves both the precision (reduces the error bars) and the accuracy of the parameter estimates, the latter by about 35%. The resulting accuracy is about 200K in temperature and 0.2mag in extinction. I then apply the method to estimate these parameters and absolute magnitudes for some 47000 F,G,K Hipparcos stars which have been cross-matched with 2MASS. The method can easily be extended to incorporate the estimation of other parameters, in particular metallicity and surface gravity, making it particularly suitable for the analysis of the 10^9 stars from Gaia.
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