Differences in Multitask Resource Reallocation After Change in Task Values

International audienceObjective The objective was to characterize multitask resource reallocation strategies when managing subtasks with various assigned values.Background When solving a resource conflict in multitasking, Salvucci and Taatgen predict a globally rational strategy will be followed that favors the most urgent subtask and optimizes global performance. However, Katidioti and Taatgen identified a locally rational strategy that optimizes only a subcomponent of the whole task, leading to detrimental consequences on global performance. Moreover, the question remains open whether expertise would have an impact on the choice of the strategy.Method We adopted a multitask environment used for pilot selection with a change in emphasis on two out of four subtasks while all subtasks had to be maintained over a minimum performance. A laboratory eye-tracking study contrasted 20 recently selected pilot students considered as experienced with this task and 15 university students considered as novices.Results When two subtasks were emphasized, novices focused their resources particularly on one high-value subtask and failed to prevent both low-value subtasks falling below minimum performance. On the contrary, experienced people delayed the processing of one low-value subtask but managed to optimize global performance.Conclusion In a multitasking environment where some subtasks are emphasized, novices follow a locally rational strategy whereas experienced participants follow a globally rational strategy.Application During complex training, trainees are only able to adjust their resource allocation strategy to subtask emphasis changes once they are familiar with the multitasking environment

Tracking of fatness during childhood, adolescence and young adulthood: a 7-year follow-up study in Madeira Island, Portugal

Aims: Investigating tracking of fatness from childhood to adolescence, early adolescence to young adulthood and late adolescence to young adulthood. Subjects and methods: Participants from the Madeira Growth Study were followed during an average period of 7.2 years. Height, body mass, skin-folds and circumferences were measured, nine health- and performance-related tests were administered and the Baecke questionnaire was used to assess physical activity. Skeletal maturity was estimated using the TW3 method. Results: The prevalence of overweight plus obesity ranged from 8.2–20.0% at baseline and from 20.4–40.0% at followup, in boys. Corresponding percentages for girls were 10.6– 12.0% and 13.2–18.0%. Inter-age correlations for fatness indicators ranged from 0.43–0.77. BMI, waist circumference and sum of skin-folds at 8, 12 and 16-years old were the main predictors of these variables at 15, 19 and 23-years old, respectively. Strength, muscular endurance and aerobic fitness were negatively related to body fatness. Physical activity and maturation were independently associated with adolescent (15 years) and young adult (19 years) fatness. Conclusions: Over 7.2 years, tracking was moderate-to-high for fatness. Variance was explained by fatness indicators and to a small extent by physical fitness, physical activity and maturation

Columbitization of fluorcalciopyrochlore by hydrothermalism at the Saint-Honoré alkaline complex, Québec (Canada) : new insights on halite in carbonatites

Niobium (Nb) in carbonatite is mainly hosted in fluorcalciopyrochlore and columbite-(Fe). Information related to Nb petrogenesis is useful for understanding the processes related to Nb mineralization and carbonatite evolution. The Saint-Honoré, Quebec, alkaline complex offers a rare opportunity for studying these processes as the complex is not affected by post-emplacement deformation, metamorphism nor weathering. Columbite-(Fe) is shown to be an alteration product of fluorcalciopyrochlore (columbitization). Columbitization is characterized by the leaching of Na and F from the A- and Y-sites of the pyrochlore crystal structure. As alteration increases, Fe and Mn are slowly introduced while Ca is simultaneously leached. Leached Ca and F then crystallize as inclusions of calcite and fluorite within the columbite-(Fe). A-site cations and vacancies in the crystal structure of fresh and altered pyrochlores demonstrate that pyrochlore alteration is hydrothermal in origin. Moreover, halite is a ubiquitous mineral in the Saint-Honoré alkaline complex. Petrographic evidence shows that halite forms in weakly altered pyrochlores, suggesting halite has a secondary origin. As alteration increases, halite is expelled by the hydrothermal fluid and is carried farther into the complex, filling factures throughout the carbonatite. The hydrothermal hypothesis is strengthened by significant enrichments in Cl and HREEs in columbite-(Fe). Chlorine is most likely introduced by a hydrothermal fluid that increases the solubility of REEs

Development of a questionnaire to assess sedentary time in older persons -- a comparative study using accelerometry

Background: There is currently no validated questionnaire available to assess total sedentary time in older adults. Most studies only used TV viewing time as an indicator of sedentary time. The first aim of our study was to investigate the self-reported time spent by older persons on a set of sedentary activities, and to compare this with objective sedentary time measured by accelerometry. The second aim was to determine what set of self-reported sedentary activities should be used to validly rank people's total sedentary time. Finally we tested the reliability of our newly developed questionnaire using the best performing set of sedentary activities. Methods. The study sample included 83 men and women aged 65-92 y, a random sample of Longitudinal Aging Study Amsterdam participants, who completed a questionnaire including ten sedentary activities and wore an Actigraph GT3X accelerometer for 8 days. Spearman correlation coefficients were calculated to examine the association between self-reported time and objective sedentary time. The test-retest reliability was calculated using the intraclass correlation coefficient (ICC). Results: Mean total self-reported sedentary time was 10.4 (SD 3.5) h/d and was not significantly different from mean total objective sedentary time (10.2 (1.2) h/d, p = 0.63). Total self-reported sedentary time on an average day (sum of ten activities) correlated moderately (Spearman's r = 0.35, p < 0.01) with total objective sedentary time. The correlation improved when using the sum of six activities (r = 0.46, p < 0.01), and was much higher than when using TV watching only (r = 0.22, p = 0.05). The test-retest reliability of the sum of six sedentary activities was 0.71 (95% CI 0.57-0.81). Conclusions: A questionnaire including six sedentary activities was moderately associated with accelerometry-derived sedentary time and can be used to reliably rank sedentary time in older persons. © 2013 Visser and Koster; licensee BioMed Central Ltd

A low-cost open-source imaging platform reveals spatiotemporal insight into leaf elongation and movement

Plant organs move throughout the diurnal cycle, changing leaf and petiole positions to balance light capture, leaf temperature, and water loss under dynamic environmental conditions. Upward movement of the petiole, called hyponasty, is one of several traits of the shade avoidance syndrome (SAS). SAS traits are elicited upon perception of vegetation shade signals such as far-red light (FR) and improve light capture in dense vegetation. Monitoring plant movement at a high temporal resolution allows studying functionality and molecular regulation of hyponasty. However, high temporal resolution imaging solutions are often very expensive, making this unavailable to many researchers. Here, we present a modular and low-cost imaging setup, based on small Raspberry Pi computers that can track leaf movements and elongation growth with high temporal resolution. We also developed an open-source, semiautomated image analysis pipeline. Using this setup, we followed responses to FR enrichment, light intensity, and their interactions. Tracking both elongation and the angle of the petiole, lamina, and entire leaf in Arabidopsis (Arabidopsis thaliana) revealed insight into R:FR sensitivities of leaf growth and movement dynamics and the interactions of R:FR with background light intensity. The detailed imaging options of this system allowed us to identify spatially separate bending points for petiole and lamina positioning of the leaf

Proximity ligation assay reveals both pre- A nd postsynaptic localization of the APP-processing enzymes ADAM10 and BACE1 in rat and human adult brain

Background: Synaptic degeneration and accumulation of amyloid \u3b2-peptides (A\u3b2) are hallmarks of the Alzheimer diseased brain. A\u3b2 is synaptotoxic and produced by sequential cleavage of the amyloid precursor protein (APP) by the \u3b2-secretase BACE1 and by \u3b3-secretase. If APP is instead cleaved by the \u3b1-secretase ADAM10, A\u3b2 will not be generated. Although BACE1 is considered to be a presynaptic protein and ADAM10 has been reported to mainly localize to the postsynaptic density, we have previously shown that both ADAM10 and BACE1 are highly enriched in synaptic vesicles of rat brain and mouse primary hippocampal neurons. Results: Here, using brightfield proximity ligation assay, we expanded our previous result in primary neurons and investigated the in situ synaptic localization of ADAM10 and BACE1 in rat and human adult brain using both pre- A nd postsynaptic markers. We found that ADAM10 and BACE1 were in close proximity with both the presynaptic marker synaptophysin and the postsynaptic marker PSD-95. The substrate APP was also detected both pre- A nd postsynaptically. Subcellular fractionation confirmed that ADAM10 and BACE1 are enriched to a similar degree in synaptic vesicles and as well as in the postsynaptic density. Conclusions: We show that the \u3b1-secretase ADAM10 and the \u3b2-secretase BACE1 are located in both the pre- A nd postsynaptic compartments in intact brain sections. These findings increase our understanding of the regulation of APP processing, thereby facilitating development of more specific treatment strategies

Blood Derived Amyloid Biomarkers for Alzheimer's Disease Prevention.

BACKGROUND: Reliable, widely accessible and affordable biomarkers for predicting Alzheimer's disease (AD) brain pathology status are a necessity to aid development of prevention strategies in cognitively healthy at-risk older adults, at the right timepoint. Measurements of the key neuropathological hallmark beta-amyloid (Aβ) by PET neuroimaging or cerebrospinal fluid measures reflect its accumulation in the brain, yet recent methodological advancements now enable blood-based measures reflecting cerebral amyloid burden. OBJECTIVES: The current study validated the capacity of plasma Aβ42/Aβ40 measured using six different assays to predict amyloid positivity in a subgroup of cognitively unimpaired (CU) participants in the ADNI study and assessed its ability to discriminate CU from AD cases. We also explored economic viability of using two different plasma amyloid assays for pre-screening in AD prevention trials and as routine clinical diagnostic tool, versus amyloid PET alone. DESIGN: A cross-sectional analysis of plasma and brain amyloid data, including comparative cost analysis of the plasma biomarkers in relation to brain amyloid PET. SETTING: Alzheimer's Disease Neuroimaging Initiative (ADNI). PARTICIPANTS: ADNI participants consisting of 115 CU, mild cognitive impairment and AD cases who had plasma Aβ42/Aβ40 measured with six platforms. MEASUREMENTS: Plasma Aβ42/Aβ40 was measured via six different platforms: three immunoassays (Roche, Quanterix and ADx Neurosciences) and three mass spectrometry (MS) based assays (WashU, Shimadzu and Gothenburg). Aβ-PET imaging was conducted within three months of plasma sampling using [18F]florbetapir. RESULTS: There was a weak to moderate correlation of plasma Aβ42/Aβ40 ratio between platforms. The MS-based WashU test had the highest capacity to discriminate between CU and AD (area under the curve, AUC = 0.734, 95% CI: 0.613-0.854; P = 0.008). Within the CU group, the WashU plasma amyloid test had the best discriminative capacity to distinguish Aβ+ from Aβ- (AUC = 0.753, 95% CI: 0.601-0.905; P = 0.003) closely followed by the immunoassay from Roche (AUC = 0.737, 95% CI: 0.597-0.877; P = 0.006). The exploratory economic analyses showed that the use of Roche or WashU plasma amyloid assay as a pre-screening tool prior to Aβ-PET scans for clinical trial recruitment significantly reduced total screening cost (saving up to $5882 per recruited patient) expected in an AD prevention trial. CONCLUSIONS: With few available treatment strategies, dementia prevention is a global priority. CU individuals at risk for AD are the target population for dementia prevention but have been poorly studied. Our findings confirming diagnostic value of ultrasensitive immunoassays and high-performance immunoprecipitation coupled with MS for measurement of plasma Aβ42/Aβ40 to detect PET amyloid positivity in CU participants allude to potential clinical utility of this biomarker. Plasma Aβ42/Aβ40 could be optimal for pre-selecting at-risk candidates for more invasive and expensive investigations across AD prevention clinical trials and clinical care for a rapidly ageing population