238 research outputs found

    The Role of Learning in Consumer Value Co-Creation Activities

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    This paper draws on Self-Directed Learning (SDL) theor

    Magnetic record of deglaciation using FORC-PCA, sortable-silt grain size, and magnetic excursion at 26 ka, from the Rockall Trough (NE Atlantic)

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    Core MD04-2822 from the Rockall Trough has apparent sedimentation rates of ~1 m/kyr during the last deglaciation (Termination I). Component magnetization directions indicate a magnetic excursion at 16.3 m depth in the core, corresponding to an age of 26.5 ka, implying an excursion duration of ~350 years. Across Termination I, the mean grain size of sortable silt implies reduced bottom-current velocity in the Younger Dryas and Heinrich Stadial (HS)-21A, and increased velocities during the BĂžlling-AllerĂžd warm period. Standard bulk magnetic parameters imply ïŹning of magnetic grain size from the mid-Younger Dryas (~12 ka) until ~8 ka. First-order reversal curves (FORCs) were analyzed using ridge extraction to differentiate single domain (SD) from background (detrital) components. Principal component analysis (FORC-PCA) was then used to discriminate three end members corresponding to SD, pseudo-single domain (PSD), and multidomain (MD) magnetite. The ïŹning of bulk magnetic grain size from 12 to 8 ka is due to reduction in concentration of detrital (PSD 1 MD) magnetite, superimposed on a relatively uniform concentration of SD magnetite pro- duced by magnetotactic bacteria. The decrease in PSD1MD magnetite concentration from 12 to 8 ka is synchronized with increase in benthic d13C, and with major (~70 m) regional sea-level rise, and may therefore be related to detrital sources on the shelf that had reduced inïŹ‚uence as sea level rose, and to bottom-water reorganization as Northern Source Water (NSW) replaced Southern Source Water (SSW)

    Examining the Role of Churches in Adolescent Girls\u27 Physical Activity

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    Background: In adults, associations between church attendance and positive health behaviors exist; however, similar evidence among children and youth is lacking. The purposes of this investigation were to examine the associations between physical activity (PA) and church attendance, PA and use of church as a PA facility, and PA and proximity to churches among those who use church as a PA facility (while addressing racial and geographic differences). Methods: High school girls (N=915, age=17.7 ± 0.6 years, 56% African American) completed the 3-Day Physical Activity Recall and surveys including demographics and use of PA facilities. Geographic Information Systems data were used to spatially examine the number of churches within a 0.75-mile street network buffer around girls\u27 homes. Associations were examined using mixed model analyses controlling for demographic factors. Results: For the overall sample, total METs (56 versus 52) and proportion of girls meeting PA guidelines (62% vs. 52%) were significantly higher in church attendees versus nonattendees. Among participants who used facilities, having more churches close to home was associated with more PA. Conclusions: Church attendance and use are correlates of physical activity that should be further explored and addressed in future intervention research with adolescent girls

    Observing secondary school teachers’ effective teaching behavior in the Netherlands, England, and the United States using the ICALT observation instrument

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    Introduction: The purpose of this study was to examine measurement invariance in observer scoring of effective teaching behavior in three secondary education contexts–the Netherlands, England, and the United States. It also aimed to describe what effective teaching behavior looks like in secondary education across the three education contexts. Methods: A uniform observation measure called International Comparative Analysis of Learning and Teaching (ICALT) was used to observe teachers. Results: Results revealed that the hypothesized factor structure of effective teaching behavior was confirmed for the Dutch and English data, but not for the US data. Teachers in the Netherlands showed higher levels of more basic teaching behaviors, but lower levels of more complex teaching behaviors, compared to teachers in England. Discussion: Implications of the findings are discussed.</p

    An evaluation of edge effects in nutritional accessibility and availability measures: a simulation study

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    <p>Abstract</p> <p>Background</p> <p>This paper addresses the statistical use of accessibility and availability indices and the effect of study boundaries on these measures. The measures are evaluated via an extensive simulation based on cluster models for local outlet density. We define outlet to mean either food retail store (convenience store, supermarket, gas station) or restaurant (limited service or full service restaurants). We designed a simulation whereby a cluster outlet model is assumed in a large study window and an internal subset of that window is constructed. We performed simulations on various criteria including one scenario representing an urban area with 2000 outlets as well as a non-urban area simulated with only 300 outlets. A comparison is made between estimates obtained with the full study area and estimates using only the subset area. This allows the study of the effect of edge censoring on accessibility measures.</p> <p>Results</p> <p>The results suggest that considerable bias is found at the edges of study regions in particular for accessibility measures. Edge effects are smaller for availability measures (when not smoothed) and also for short range accessibility</p> <p>Conclusions</p> <p>It is recommended that any study utilizing these measures should correct for edge effects. The use of edge correction via guard areas is recommended and the avoidance of large range distance-based accessibility measures is also proposed.</p

    Do Physical Activity Facilities near Schools Affect Physical Activity in High School Girls?

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    Objective - To investigate associations between the number of physical activity facilities within walking distance of school and physical activity behavior in 12th grade girls during after-school hours. Methods - Girls (N=1394) from 22 schools completed a self-report to determine physical activity after 3:00 pm. The number of physical activity facilities within a 0.75-mile buffer of the school was counted with a Geographic Information System. Associations between the number of facilities and girls\u27 physical activity were examined using linear mixed-model analysis of variance. Results - Overall, girls who attended schools with ≄ 5 facilities within the buffer reported more physical activity per day than girls in schools with \u3c 5 facilities. In addition, girls who attended rural schools with ≄ 5 facilities reported ~12% more physical activity per day than girls who attended rural schools with \u3c 5 facilities. No difference existed for girls in urban/suburban schools with ≄ 5 vs. \u3c 5 facilities. Conclusion - When school siting decisions are made, the number of physical activity facilities surrounding the school should be considered to encourage physical activity in 12th grade girls

    Multispectral imaging for presymptomatic analysis of light leaf spot in oilseed rape

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    Background: The use of spectral imaging within the plant phenotyping and breeding community has been increasing due its utility as a non-invasive diagnostic tool. However, there is a lack of imaging systems targeted specifically at plant science duties, resulting in low precision for canopy-scale measurements. This study trials a prototype multispectral system designed specifically for plant studies and looks at its use as an early detection system for visually asymptomatic disease phases, in this case Pyrenopeziza brassicae in Brassica napus. The analysis takes advantage of machine learning in the form of feature selection and novelty detection to facilitate the classification. An initial study into recording the morphology of the samples is also included to allow for further improvement to the system performance. Results: The proposed method was able to detect light leaf spot infection with 92% accuracy when imaging entire oilseed rape plants from above, 12 days after inoculation and 13 days before the appearance of visible symptoms. False colour mapping of spectral vegetation indices was used to quantify disease severity and its distribution within the plant canopy. In addition, the structure of the plant was recorded using photometric stereo, with the output influencing regions used for diagnosis. The shape of the plants was also recorded using photometric stereo, which allowed for reconstruction of the leaf angle and surface texture, although further work is needed to improve the fidelity due to uneven lighting distributions, to allow for reflectance compensation. Conclusions: The ability of active multispectral imaging has been demonstrated along with the improvement in time taken to detect light leaf spot at a high accuracy. The importance of capturing structural information is outlined, with its effect on reflectance and thus classification illustrated. The system could be used in plant breeding to enhance the selection of resistant cultivars, with its early and quantitative capability

    Evaluating geographic imputation approaches for zip code level data: an application to a study of pediatric diabetes

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    <p>Abstract</p> <p>Background</p> <p>There is increasing interest in the study of place effects on health, facilitated in part by geographic information systems. Incomplete or missing address information reduces geocoding success. Several geographic imputation methods have been suggested to overcome this limitation. Accuracy evaluation of these methods can be focused at the level of individuals and at higher group-levels (e.g., spatial distribution).</p> <p>Methods</p> <p>We evaluated the accuracy of eight geo-imputation methods for address allocation from ZIP codes to census tracts at the individual and group level. The spatial apportioning approaches underlying the imputation methods included four fixed (deterministic) and four random (stochastic) allocation methods using land area, total population, population under age 20, and race/ethnicity as weighting factors. Data included more than 2,000 geocoded cases of diabetes mellitus among youth aged 0-19 in four U.S. regions. The imputed distribution of cases across tracts was compared to the true distribution using a chi-squared statistic.</p> <p>Results</p> <p>At the individual level, population-weighted (total or under age 20) fixed allocation showed the greatest level of accuracy, with correct census tract assignments averaging 30.01% across all regions, followed by the race/ethnicity-weighted random method (23.83%). The true distribution of cases across census tracts was that 58.2% of tracts exhibited no cases, 26.2% had one case, 9.5% had two cases, and less than 3% had three or more. This distribution was best captured by random allocation methods, with no significant differences (p-value > 0.90). However, significant differences in distributions based on fixed allocation methods were found (p-value < 0.0003).</p> <p>Conclusion</p> <p>Fixed imputation methods seemed to yield greatest accuracy at the individual level, suggesting use for studies on area-level environmental exposures. Fixed methods result in artificial clusters in single census tracts. For studies focusing on spatial distribution of disease, random methods seemed superior, as they most closely replicated the true spatial distribution. When selecting an imputation approach, researchers should consider carefully the study aims.</p

    An empirical approach to improving tidal predictions using recent real-time tide gauge data

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    Harmonic tidal prediction methods are often problematic in estuaries owing to the distortion of tidal fluctuations in shallow water, causing disparity between predicted and observed sea levels. The UK National Tidal and Sea Level Facility attempted to reduce prediction errors for the short-term forecasting of High Water (HW) extremes using three alternative techniques to the Harmonic Method in the Bristol Channel, where prediction errors are relatively large. A simple procedure for correcting Harmonic Method HW predictions using recent observations (referred to as the Empirical Correction Method) proved most effective and was also successfully applied to sea-level records from 42 of the 44 UK Tide Gauge Network locations. It is to be incorporated into the operational systems of the UK Coastal Monitoring and Forecasting Partnership to improve UK short-term sea level predictions

    Implications of 36Cl exposure ages from Skye, northwest Scotland for the timing of ice stream deglaciation and deglacial ice dynamics

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    The French national AMS facility ASTER (CEREGE, Aix en Provence) is supported by the INSU/CNRS, the ANR through the "Projets thĂ©matiques d’excellence" program for the "Equipements d’excellence" ASTER-CEREGE action, IRD and CEA. The authors would like to thank Shasta Marrero for helpful and informative discussion on the CRONUScalc online calculator. DS was supported by a SAGES studentship and fieldwork by funds from the QRA and BSG.Geochronological constraints on the deglaciation of former marine based ice streams provide information on the rates and modes by which marine based ice sheets have responded to external forcing factors such as climate change. This paper presents new 36Cl cosmic ray exposure dating from boulders located on two moraines (Glen Brittle and Loch Scavaig) in southern Skye, northwest Scotland. Ages from the Glen Brittle moraines constrain deglaciation of a major marine terminating ice stream, the Barra-Donegal Ice Stream that drained the former British-Irish Ice Sheet, depending on choice of production method and scaling model this occurred 19.9 ± 1.5–17.6 ± 1.3 ka ago. We compare this timing of deglaciation to existing geochronological data and changes in a variety of potential forcing factors constrained through proxy records and numerical models to determine what deglaciation age is most consistent with existing evidence. Another small section of moraine, the Scavaig moraine, is traced offshore through multibeam swath-bathymetry and interpreted as delimiting a later stillstand/readvance stage following ice stream deglaciation. Additional cosmic ray exposure dating from the onshore portion of this moraine indicate that it was deposited 16.3 ± 1.3–15.2 ± 0.9 ka ago. When calculated using the most up-to-date scaling scheme this time of deposition is, within uncertainty, the same as the timing of a widely identified readvance, the Wester Ross Readvance, observed elsewhere in northwest Scotland. This extends the area over which this readvance has potentially occurred, reinforcing the view that it was climatically forced.PostprintPeer reviewe
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