Browsing by Subject "Measurement"

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    Open Access
    H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7
    (2017) Namumba, B; Carignan, C; Passmoor, S; de Blok, W J G
    We present high sensitivity H I observations of NGC 6822, obtained with the Karoo Array Telescope (KAT-7). We study the kinematics, the mass distribution and the star formation thresholds. The KAT-7 short baselines and low system temperature make it sensitive to large-scale, low surface brightness emission. The observations detected ∼ 23 per cent more flux than previous Australian Telescope Compact Array observations. We fit a tilted ring model to the H I velocity field to derive the rotation curve (RC). The KAT-7 observations allow the measurement of the rotation curve of NGC 6822 out to 5.8 kpc, ∼1 kpc further than existing measurements. NGC 6822 is seen to be dark matter dominated at all radii. The observationally motivated pseudo-isothermal dark matter (DM) halo model reproduces well the observed RC while the Navarro Frank-White DM model gives a poor fit to the data. We find the best-fitting mass-to-light ratio (M/L) of 0.12 ± 0.01 which is consistent with the literature. The modified Newtonian dynamics gives a poor fit to our data. We derive the star formation threshold in NGC 6822 using the H I and H α data. The critical gas densities were calculated for gravitational instabilities using the Toomre-Q criterion and the cloud-growth criterion. We found that in regions of star formation, the cloud-growth criterion explains star formation better than the Toomre-Q criterion. This shows that the local shear rate could be a key player in cloud formation for irregular galaxies such as NGC 6822.
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    Open Access
    Improving wear time compliance with a 24-hour waist-worn accelerometer protocol in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE)
    (2015-02-11) Tudor-Locke, Catrine; Barreira, Tiago V; Schuna, John M; Mire, Emily F; Chaput, Jean-Philippe; Fogelholm, Mikael; Hu, Gang; Kuriyan, Rebecca; Kurpad, Anura; Lambert, Estelle V; Maher, Carol; Maia, José; Matsudo, Victor; Olds, Tim; Onywera, Vincent; Sarmiento, Olga L; Standage, Martyn; Tremblay, Mark S; Zhao, Pei; Church, Timothy S; Katzmarzyk, Peter T
    Abstract Background We compared 24-hour waist-worn accelerometer wear time characteristics of 9–11 year old children in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) to similarly aged U.S. children providing waking-hours waist-worn accelerometer data in the 2003–2006 National Health and Nutrition Examination Survey (NHANES). Methods Valid cases were defined as having ≥4 days with ≥10 hours of waking wear time in a 24-hour period, including one weekend day. Previously published algorithms for extracting total sleep episode time from 24-hour accelerometer data and for identifying wear time (in both the 24-hour and waking-hours protocols) were applied. The number of valid days obtained and a ratio (percent) of valid cases to the number of participants originally wearing an accelerometer were computed for both ISCOLE and NHANES. Given the two surveys’ discrepant sampling designs, wear time (minutes/day, hours/day) from U.S. ISCOLE was compared to NHANES using a meta-analytic approach. Wear time for the 11 additional countries participating in ISCOLE were graphically compared with NHANES. Results 491 U.S. ISCOLE children (9.92±0.03 years of age [M±SE]) and 586 NHANES children (10.43 ± 0.04 years of age) were deemed valid cases. The ratio of valid cases to the number of participants originally wearing an accelerometer was 76.7% in U.S. ISCOLE and 62.6% in NHANES. Wear time averaged 1357.0 ± 4.2 minutes per 24-hour day in ISCOLE. Waking wear time was 884.4 ± 2.2 minutes/day for U.S. ISCOLE children and 822.6 ± 4.3 minutes/day in NHANES children (difference = 61.8 minutes/day, p < 0.001). Wear time characteristics were consistently higher in all ISCOLE study sites compared to the NHANES protocol. Conclusions A 24-hour waist-worn accelerometry protocol implemented in U.S. children produced 22.6 out of 24 hours of possible wear time, and 61.8 more minutes/day of waking wear time than a similarly implemented and processed waking wear time waist-worn accelerometry protocol. Consistent results were obtained internationally. The 24-hour protocol may produce an important increase in wear time compliance that also provides an opportunity to study the total sleep episode time separate and distinct from physical activity and sedentary time detected during waking-hours. Trial registration ClinicalTrials.gov NCT01722500 .
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    Open Access
    Informing the measurement of wellbeing among young people living with HIV in sub-Saharan Africa for policy evaluations: a mixed-methods systematic review
    (2020-05-05) Govindasamy, Darshini; Seeley, Janet; Olaru, Ioana D; Wiyeh, Alison; Mathews, Catherine; Ferrari, Giulia
    Young people living with HIV (YPLHIV) in sub-Saharan Africa (SSA) are at high risk of having a poor quality of life. Addressing wellbeing explicitly within HIV/AIDS policies could assist mitigation efforts. However, guidance on wellbeing measures to evaluate policies for YPLHIV is scarce. The aims of this mixed-methods review were to identify: i) key dimensions of wellbeing and ii) wellbeing measures that align to these dimensions among YPLHIV (15–24 years) in SSA. We searched six social science and medical databases, including grey literature. We included studies that examined correlates and lived experiences of wellbeing, among YPLHIV in SSA, from January 2000 to May 2019. Two reviewers independently screened abstracts and full texts and assessed methodological quality of included articles. We analysed quantitative and qualitative data using descriptive and meta-ethnographic approaches, respectively. Thereafter, we integrated findings using a framework approach. We identified 6527 citations. Of these, 10 quantitative and 30 qualitative studies were included. Being male, higher educational status, less stigma and more social support were likely correlates of wellbeing. Themes that shaped experiences suggestive of wellbeing were: 1) acceptance and belonging— stigma, social support; 2) coping; 3) standard of living. Our final synthesis found that the following dimensions potentially characterise wellbeing: self-acceptance, belonging, autonomy; positive relations, environmental mastery, purpose in life. Wellbeing for YPLHIV is multi-dimensional and relational. Relevant measures include the Personal Wellbeing Index, Ryff’s Psychological Wellbeing Scale and Mental Health Continuum Short Form. However, psychometric evaluations of these scales among YPLHIV in SSA are needed.
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