Optimal Orbital Coverage of Theater Operations and Targets

The use of satellites as a tactical asset to support theater operations is a desired capability for future space operations. Unlike traditional satellite systems designed to provide coverage over the entire globe or large regions, tactical satellites would provide coverage over a small region which can be modeled as a single ground point defined by a latitude and longitude. In order to provide sufficient utility as a theater asset, a satellite should be placed in an orbit that provides a maximum amount of coverage of the target ground point. This study examined the optimization of orbit parameters to maximize the number of passes made over a target. An optimization algorithm was developed to maximize the number of passes made while also minimizing the distance from the satellite to the target. Single satellite coverage properties as well as two and three satellite constellations were analyzed

Neural computations underlying action-based decision making in the human brain

Action-based decision making involves choices between different physical actions to obtain rewards. To make such decisions the brain needs to assign a value to each action and then compare them to make a choice. Using fMRI in human subjects, we found evidence for action-value signals in supplementary motor cortex. Separate brain regions, most prominently ventromedial prefrontal cortex, were involved in encoding the expected value of the action that was ultimately taken. These findings differentiate two main forms of value signals in the human brain: those relating to the value of each available action, likely reflecting signals that are a precursor of choice, and those corresponding to the expected value of the action that is subsequently chosen, and therefore reflecting the consequence of the decision process. Furthermore, we also found signals in the dorsomedial frontal cortex that resemble the output of a decision comparator, which implicates this region in the computation of the decision itself

Outcomes of exclusive enteral nutrition in paediatric Crohn\u27s disease

Background/objectives: Exclusive enteral nutrition (EEN) is a safe and effective treatment modality for inducing remission in paediatric Crohn\u27s disease (CD). The primary aim of this study was to compare the outcomes of EEN to corticosteroid (CS) therapy in newly diagnosed, treatment-naïve patients with CD. A secondary aim was to describe the outcomes of EEN in a national cohort of paediatric CD patients over a 10-year period. Subjects/methods: A retrospective chart review was conducted at the Irish national referral centre for paediatric CD. A case-matched analysis was conducted on two cohorts matched for age, gender, disease location, disease behaviour and disease activity, who received CS or EEN as their initial treatment. Subsequently, cohort analysis was conducted on all patients who undertook a course of EEN therapy between 2004 and 2013. Results: The case-matched analysis found higher remission rates after treatment with EEN (24/28, 86%) compared with those with CS (15/28, 54%; P=0.02). Dietetic contacts were found to be pivotal to the success of treatment and the attainment of remission. In total, 59 patients completed EEN at some time-point in their disease course and were included in the cohort analysis. Sixty-nine per cent of this cohort entered clinical remission (41/59). EEN was found to be most effective when used as an initial treatment (P=0.004) and less effective in patients aged under 10 years (P=0.04). Conclusions: EEN should be strongly considered as a favourable primary treatment over CS, especially in those diagnosed over the age of 10 years

Economic choices can be made using only stimulus values

Decision-making often involves choices between different stimuli, each of which is associated with a different physical action. A growing consensus suggests that the brain makes such decisions by assigning a value to each available option and then comparing them to make a choice. An open question in decision neuroscience is whether the brain computes these choices by comparing the values of stimuli directly in goods space or instead by first assigning values to the associated actions and then making a choice over actions. We used a functional MRI paradigm in which human subjects made choices between different stimuli with and without knowledge of the actions required to obtain the different stimuli. We found neural correlates of the value of the chosen stimulus (a postdecision signal) in ventromedial prefrontal cortex before the actual stimulus–action pairing was revealed. These findings provide support for the hypothesis that the brain is capable of making choices in the space of goods without first transferring values into action space

Meta-analysis & Review of Learner Performance & Preference: Virtual vs. Optical Microscopy

Background & Purpose: For nearly two decades, a wealth of literature has been published describing the various capabilities, uses, and adaptations of virtual microscopy (VM). Many studies have investigated the effects and benefits of VM on student learning compared to optical microscopy (OM). As such, this study statistically aggregated the findings of multiple comparative studies through a meta-analysis to summarize and substantiate the pedagogical efficacy of teaching with VM. Methods Using predefined eligibility criteria, teams of paired researchers screened the titles and abstracts of VM studies retrieved from seven different databases. After two rounds of screening, numerical and thematic data were extracted from the eligible studies for analysis. A summary effect size and estimate of heterogeneity were calculated to determine the effects of VM on learner performance and the amount of variance between studies, respectively. Trends in student perceptions were also analyzed and reported. Results: Of the 725 records screened, 72 studies underwent full-text review. In total, 12 studies were viable for meta-analysis and additional studies were reviewed to extract themes relating to learners’ perceptions of VM. The meta-analysis detected a small yet significant positive effect on learner performance (SMD=0.28, [CI=0.09, 0.47], p=0.003), indicating that learners experience marked knowledge gains when exposed to VM over OM. Variation among studies was evident as high heterogeneity was reported. An analysis of trends in learner perceptions noted that respondents favored VM over OM by a large margin. Conclusions: Despite many individual studies reporting non-significant findings when comparing VM to OM, the enhanced power afforded by meta-analysis revealed that the pedagogical approach of VM is modestly superior to OM and is preferred by learners

Decoding the neural substrates of reward-related decision making with functional MRI

Although previous studies have implicated a diverse set of brain regions in reward-related decision making, it is not yet known which of these regions contain information that directly reflects a decision. Here, we measured brain activity using functional MRI in a group of subjects while they performed a simple reward-based decision-making task: probabilistic reversal-learning. We recorded brain activity from nine distinct regions of interest previously implicated in decision making and separated out local spatially distributed signals in each region from global differences in signal. Using a multivariate analysis approach, we determined the extent to which global and local signals could be used to decode subjects' subsequent behavioral choice, based on their brain activity on the preceding trial. We found that subjects' decisions could be decoded to a high level of accuracy on the basis of both local and global signals even before they were required to make a choice, and even before they knew which physical action would be required. Furthermore, the combined signals from three specific brain areas (anterior cingulate cortex, medial prefrontal cortex, and ventral striatum) were found to provide all of the information sufficient to decode subjects' decisions out of all of the regions we studied. These findings implicate a specific network of regions in encoding information relevant to subsequent behavioral choice

The COVID-19 pandemic and children’s engagement with learning in rural Sierra Leone

The COVID-19 pandemic caused worldwide educational disruption. This paper addresses a gap in the literature relating to the impact of the pandemic on learning experiences of children in rural communities in the Global South, particularly in earlier years of schooling. Children in these communities are at considerable disadvantage in comparison to their urban peers due to poor school infrastructure and challenges in recruitment and retention of teachers. Drawing on a mixed-methods study of primary school children, their teachers and families in rural Sierra Leone, both during and immediately after school closures, the paper highlights how primary schools and their communities responded to the pandemic and how this influenced children’s engagement with their learning. While national planning focused on pandemic control measures and provision of some remote learning support, findings highlight challenges for poor rural communities in accessing basic learning supports and the consequent disruption to children’s education

Transcript of The Dory Derby Accident

This story is an excerpt from a longer interview that was collected as part of the Launching through the Surf: The Dory Fleet of Pacific City project. In this story, Don Grotjohn recounts an accident that occurred during a Dory Derby competition