Browsing by Subject "Methods"

Now showing 1 - 4 of 4
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    Open Access
    A model for presenting accelerometer paradata in large studies: ISCOLE
    (2015-04-20) Tudor-Locke, Catrine; Mire, Emily F; Dentro, Kara N; Barreira, Tiago V; Schuna, John M; Zhao, Pei; Tremblay, Mark S; Standage, Martyn; Sarmiento, Olga L; Onywera, Vincent; Olds, Tim; Matsudo, Victor; Maia, José; Maher, Carol; Lambert, Estelle V; Kurpad, Anura; Kuriyan, Rebecca; Hu, Gang; Fogelholm, Mikael; Chaput, Jean-Philippe; Church, Timothy S; Katzmarzyk, Peter T
    Abstract Background We present a model for reporting accelerometer paradata (process-related data produced from survey administration) collected in the International Study of Childhood Obesity Lifestyle and the Environment (ISCOLE), a multi-national investigation of >7000 children (averaging 10.5 years of age) sampled from 12 different developed and developing countries and five continents. Methods ISCOLE employed a 24-hr waist worn 7-day protocol using the ActiGraph GT3X+. Checklists, flow charts, and systematic data queries documented accelerometer paradata from enrollment to data collection and treatment. Paradata included counts of consented and eligible participants, accelerometers distributed for initial and additional monitoring (site specific decisions in the face of initial monitoring failure), inadequate data (e.g., lost/malfunction, insufficient wear time), and averages for waking wear time, valid days of data, participants with valid data (≥4 valid days of data, including 1 weekend day), and minutes with implausibly high values (≥20,000 activity counts/min). Results Of 7806 consented participants, 7372 were deemed eligible to participate, 7314 accelerometers were distributed for initial monitoring and another 106 for additional monitoring. 414 accelerometer data files were inadequate (primarily due to insufficient wear time). Only 29 accelerometers were lost during the implementation of ISCOLE worldwide. The final locked data file consisted of 6553 participant files (90.0% relative to number of participants who completed monitoring) with valid waking wear time, averaging 6.5 valid days and 888.4 minutes/day (14.8 hours). We documented 4762 minutes with implausibly high activity count values from 695 unique participants (9.4% of eligible participants and <0.01% of all minutes). Conclusions Detailed accelerometer paradata is useful for standardizing communication, facilitating study management, improving the representative qualities of surveys, tracking study endpoint attainment, comparing studies, and ultimately anticipating and controlling costs. Trial registration ClinicalTrials.gov: NCT01722500
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    Open Access
    Bayesian inference for radio observations
    (Oxford University Press, 25) Lochner, Michelle; Natarajan, Iniyan; Zwart, Jonathan T L; Smirnov, Oleg; Bassett, Bruce A; Oozeer, Nadeem; Kunz, Martin
    New telescopes like the Square Kilometre Array (SKA) will push into a new sensitivity regime and expose systematics, such as direction-dependent effects, that could previously be ignored. Current methods for handling such systematics rely on alternating best estimates of instrumental calibration and models of the underlying sky, which can lead to inadequate uncertainty estimates and biased results because any correlations between parameters are ignored. These deconvolution algorithms produce a single image that is assumed to be a true representation of the sky, when in fact it is just one realization of an infinite ensemble of images compatible with the noise in the data. In contrast, here we report a Bayesian formalism that simultaneously infers both systematics and science. Our technique, Bayesian Inference for Radio Observations (BIRO), determines all parameters directly from the raw data, bypassing image-making entirely, by sampling from the joint posterior probability distribution. This enables it to derive both correlations and accurate uncertainties, making use of the flexible software MEQTREES to model the sky and telescope simultaneously. We demonstrate BIRO with two simulated sets of Westerbork Synthesis Radio Telescope data sets. In the first, we perform joint estimates of 103 scientific (flux densities of sources) and instrumental (pointing errors, beamwidth and noise) parameters. In the second example, we perform source separation with BIRO. Using the Bayesian evidence, we can accurately select between a single point source, two point sources and an extended Gaussian source, allowing for ‘super-resolution’ on scales much smaller than the synthesized beam.
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    Open Access
    Is the golden hour optimally used in South Africa for children presenting with polytrauma?
    (2013) Zuidgeest, J; Jonkheijm, A; Van Dijk, M; Van As, A
    BACKGROUND: The major paediatric public health problem worldwide is injury or trauma. In 2004, 950 000 children died as a result of injury. OBJECTIVE: The aim of this study was to evaluate the logistics of medical care after paediatric polytrauma within the first hours after arrival into a trauma unit - the so-called Golden Hour. METHODS: Children presenting with polytrauma to the Trauma Unit at the Red Cross War Memorial Children's Hospital between May 2011 and August 2011 were considered for inclusion in the study. RESULTS: Fifty-five children were included in the final analysis. The median duration of stay in the Trauma Unit was 205 minutes (interquartile range 135 - 274). CONCLUSION: Several factors were identified that unnecessarily prolonged the time that patients stayed in the trauma unit following arrival in hospital for polytrauma management.
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    Open Access
    The immunological response to syphilis differs by HIV status; a prospective observational cohort study
    (2017) Kenyon, Chris; Osbak, Kara Krista; Crucitti, Tania; Kestens, Luc
    BACKGROUND: It is not known if there is a difference in the immune response to syphilis between HIV-infected and uninfected individuals. METHODS: We prospectively recruited all patients with a new diagnosis of syphilis and tested their plasma for IFNα, IFNγ, IL-1β, IL-12p40, IL-12p70, IP-10, MCP-1, MIP-1α, MIP-1β, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10 and IL-17A at baseline pre-treatment and 6 months following therapy. RESULTS: A total of 79 HIV-infected [44 primary/secondary syphilis (PSS) and 35 latent syphilis (LS)] and 12 HIV-uninfected (10 PSS and 2 LS) cases of syphilis and 30 HIV-infected controls were included in the study. At the baseline visit, compared to the control group, concentrations of IL-10 were significantly elevated in the HIV-infected and uninfected groups. The level of IL-10 was significantly higher in the HIV-infected compared to the HIV-uninfected PSS group (25.3 pg/mL (IQR, 4.56-41.76) vs 2.73 pg/mL (IQR, 1.55-9.02), P = 0.0192). In the HIV-infected PSS group (but not the HIV-infected LS or HIV-uninfected PSS groups) the IP-10, MIP-1b, IL-6 and IL-8 were raised compared to the controls. IL-10 levels decreased but did not return to control baseline values by 6 months in HIV infected PSS and LS and HIV uninfected PSS. CONCLUSION: PSS and LS in HIV-infected individuals is characterized by an increase in inflammatory and anti-inflammatory cytokines such as IL-10. The increase of IL-10 is greater in HIV-infected than uninfected individuals. Further work is required to ascertain if this is part of an immunological profile that correlates with adverse outcomes such as serofast syphilis and neurosyphilis, in HIV-infected individuals.