424 research outputs found

    Probing the Relation Between X-ray-Derived and Weak-Lensing-Derived Masses for Shear-Selected Galaxy Clusters: I. A781

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    We compare X-ray and weak-lensing masses for four galaxy clusters that comprise the top-ranked shear-selected cluster system in the Deep Lens Survey. The weak-lensing observations of this system, which is associated with A781, are from the Kitt Peak Mayall 4-m telescope, and the X-ray observations are from both Chandra and XMM-Newton. For a faithful comparison of masses, we adopt the same matter density profile for each method, which we choose to be an NFW profile. Since neither the X-ray nor weak-lensing data are deep enough to well constrain both the NFW scale radius and central density, we estimate the scale radius using a fitting function for the concentration derived from cosmological hydrodynamic simulations and an X-ray estimate of the mass assuming isothermality. We keep this scale radius in common for both X-ray and weak-lensing profiles, and fit for the central density, which scales linearly with mass. We find that for three of these clusters, there is agreement between X-ray and weak-lensing NFW central densities, and thus masses. For the other cluster, the X-ray central density is higher than that from weak-lensing by 2 sigma. X-ray images suggest that this cluster may be undergoing a merger with a smaller cluster. This work serves as an additional step towards understanding the possible biases in X-ray and weak-lensing cluster mass estimation methods. Such understanding is vital to efforts to constrain cosmology using X-ray or weak-lensing cluster surveys to trace the growth of structure over cosmic time.Comment: 14 pages, 7 figures, matches version in Ap

    Understanding Prediabetes Through Facebook: Pilot Study Protocol and Lessons Learned

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    Purpose/Background: Type 2 Diabetes is a serious contributor to mortality and morbidity. Rural populations (including those in Mountain West regions) exhibit greater health disparities than their urban counterparts for many conditions, including diabetes. It is therefore vital to address this important health issue, especially among rural populations. One way to address diabetes is with prevention, starting with enhanced detection of prediabetes. According to the CDC, more than 84 millions Americans (one in three adults) has prediabetes, but nine out of ten are not aware of their condition, which hampers prevention efforts. Infodemiology has been used successfully to track health information found on social media. Our project aims to find indicators of prediabetes through Facebook content, with a long-term goal of developing an effective social media screening tool for prediabetes. Materials & Methods: This study had an exploratory retrospective design (the study protocol has been published; Xu, Litchman, Geeet al., 2018 JMIR Research Protocols). Utilizing electronic medical records from a Mountain West region family medicine clinic, we recruited 17 patients diagnosed with prediabetes who were willing to share their Facebook posts. Participants completed a clinic session where they responded to a number of surveys (e.g., Facebook Intensity Scale, Prediabetes Online Community Engagement Scale, Computer-Mediated Social Support Scale) and provided us with their Facebook account information. We then accessed and coded all Facebook posts for the 6-month period surrounding their prediabetes diagnosis (3-months pre through 3-months post-diagnosis; see Figure 1). Coding included meta-data (e.g., time of post, post type), post text/visuals, social aspects of the post (e.g., comments, reactions, shares), and content of interest (e.g., health, physical symptoms, lifestyle factors, medical experiences, food etc.). Results: Descriptive information about participant demographics and their responses to surveys are provided (see Table 1). We are currently compiling the coded data and will use a mixed-method protocol for analyses. This includes both qualitative content analysis to identify themes as well as a quantitative approach to examine potential differences between the 3-months prediagnosis and the 3-months postdiagnosis for our participants. While we were able to code data for 17 patients, due to unanticipated barriers in recruitment and coding we did not meet our planned goal of 20 patients. To assist those planning on conducting this type of social media research, we will discuss some of these issues including the importance of having a large team of coders who can work simultaneously. Discussion/Conclusion: Data from this project should provide an initial taxonomy of prediabetes indicators indentifiable within a social media context. Future studies, with larger samples, can test the utility of the taxonomy on predicting prediabetes status from Facebook posts. We also hope that our lessons learned information will be helpful to other researchers working on social media health studies. The ultimate goal of our research is to develop an automated method to identify social media users who are likely to have prediabetes. This would be especially helpful for those who are unaware of their health condition, as identification can lead to efforts that can prevent the progression of prediabetes to diabetes

    A Quality Major: Some Doctoral Programs Are Beginning to Offer a Specialization in Quality

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    Describes the doctorate in technology management from Indiana State University, a member of a consortium offering the degree that prepares graduates to be technological leaders for public and private sectors

    Beyond deficit-based models of learners' cognition: Interpreting engineering students' difficulties with sense-making in terms of fine-grained epistemological and conceptual dynamics

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    Researchers have argued against deficit-based explanations of students' troubles with mathematical sense-making, pointing instead to factors such as epistemology: students' beliefs about knowledge and learning can hinder them from activating and integrating productive knowledge they have. In this case study of an engineering major solving problems (about content from his introductory physics course) during a clinical interview, we show that "Jim" has all the mathematical and conceptual knowledge he would need to solve a hydrostatic pressure problem that we posed to him. But he reaches and sticks with an incorrect answer that violates common sense. We argue that his lack of mathematical sense-making-specifically, translating and reconciling between mathematical and everyday/common-sense reasoning-stems in part from his epistemological views, i.e., his views about the nature of knowledge and learning. He regards mathematical equations as much more trustworthy than everyday reasoning, and he does not view mathematical equations as expressing meaning that tractably connects to common sense. For these reasons, he does not view reconciling between common sense and mathematical formalism as either necessary or plausible to accomplish. We, however, avoid a potential "deficit trap"-substituting an epistemological deficit for a concepts/skills deficit-by incorporating multiple, context-dependent epistemological stances into Jim's cognitive dynamics. We argue that Jim's epistemological stance contains productive seeds that instructors could build upon to support Jim's mathematical sense-making: He does see common-sense as connected to formalism (though not always tractably so) and in some circumstances this connection is both salient and valued.Comment: Submitted to the Journal of Engineering Educatio

    Spontaneous Subarachnoid Hemorrhage: A Systematic Review and Meta-analysis Describing the Diagnostic Accuracy of History, Physical Examination, Imaging, and Lumbar Puncture With an Exploration of Test Thresholds.

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    BACKGROUND: Spontaneous subarachnoid hemorrhage (SAH) is a rare, but serious etiology of headache. The diagnosis of SAH is especially challenging in alert, neurologically intact patients, as missed or delayed diagnosis can be catastrophic. OBJECTIVES: The objective was to perform a diagnostic accuracy systematic review and meta-analysis of history, physical examination, cerebrospinal fluid (CSF) tests, computed tomography (CT), and clinical decision rules for spontaneous SAH. A secondary objective was to delineate probability of disease thresholds for imaging and lumbar puncture (LP). METHODS: PubMed, Embase, Scopus, and research meeting abstracts were searched up to June 2015 for studies of emergency department patients with acute headache clinically concerning for spontaneous SAH. QUADAS-2 was used to assess study quality and, when appropriate, meta-analysis was conducted using random effects models. Outcomes were sensitivity, specificity, and positive (LR+) and negative (LR-) likelihood ratios. To identify test and treatment thresholds, we employed the Pauker-Kassirer method with Bernstein test indication curves using the summary estimates of diagnostic accuracy. RESULTS: A total of 5,022 publications were identified, of which 122 underwent full-text review; 22 studies were included (average SAH prevalence = 7.5%). Diagnostic studies differed in assessment of history and physical examination findings, CT technology, analytical techniques used to identify xanthochromia, and criterion standards for SAH. Study quality by QUADAS-2 was variable; however, most had a relatively low risk of biases. A history of neck pain (LR+ = 4.1; 95% confidence interval [CI] = 2.2 to 7.6) and neck stiffness on physical examination (LR+ = 6.6; 95% CI = 4.0 to 11.0) were the individual findings most strongly associated with SAH. Combinations of findings may rule out SAH, yet promising clinical decision rules await external validation. Noncontrast cranial CT within 6 hours of headache onset accurately ruled in (LR+ = 230; 95% CI = 6 to 8,700) and ruled out SAH (LR- = 0.01; 95% CI = 0 to 0.04); CT beyond 6 hours had a LR- of 0.07 (95% CI = 0.01 to 0.61). CSF analyses had lower diagnostic accuracy, whether using red blood cell (RBC) count or xanthochromia. At a threshold RBC count of 1,000 Ă— 10(6) /L, the LR+ was 5.7 (95% CI = 1.4 to 23) and LR- was 0.21 (95% CI = 0.03 to 1.7). Using the pooled estimates of diagnostic accuracy and testing risks and benefits, we estimate that LP only benefits CT-negative patients when the pre-LP probability of SAH is on the order of 5%, which corresponds to a pre-CT probability greater than 20%. CONCLUSIONS: Less than one in 10 headache patients concerning for SAH are ultimately diagnosed with SAH in recent studies. While certain symptoms and signs increase or decrease the likelihood of SAH, no single characteristic is sufficient to rule in or rule out SAH. Within 6 hours of symptom onset, noncontrast cranial CT is highly accurate, while a negative CT beyond 6 hours substantially reduces the likelihood of SAH. LP appears to benefit relatively few patients within a narrow pretest probability range. With improvements in CT technology and an expanding body of evidence, test thresholds for LP may become more precise, obviating the need for a post-CT LP in more acute headache patients. Existing SAH clinical decision rules await external validation, but offer the potential to identify subsets most likely to benefit from post-CT LP, angiography, or no further testing

    Coaching Games: Comparisons and Contrasts

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    A key feature of any coach’s role is to decide on the most appropriate approach to develop player learning and performance at any given time. When coaching games, these decisions are even more challenging due to the interactive nature of games themselves and, in team games, this interactivity is heightened. Therefore, proponents of various approaches to coaching games could do well to demonstrate how different approaches may compliment rather than oppose each other, to avoid a one-size-fits-all process of coaching. In this insights paper, we summarise some of the fundamental approaches used for coaching games, whilst clarifying and contrasting their theoretical and practical differences. In doing so, we propose that there is a space in the coach’s toolbox for a games approach that hones the metacognitive skills of players. We also suggest reasons why coaches might use metacognitive game design as a tool to develop players’ deep understanding of game play to support player learning and performance

    Shear-Selected Clusters From the Deep Lens Survey III: Masses from Weak Lensing

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    We present weak lensing mass estimates of seven shear-selected galaxy cluster candidates from the Deep Lens Survey. The clusters were previously identified as mass peaks in convergence maps of 8.6 sq. deg of R band imaging, and followed up with X-ray and spectroscopic confirmation, spanning a redshift range 0.19 - 0.68. Most clusters contained multiple X-ray peaks, yielding 17 total mass concentrations. In this paper, we constrain the masses of these X-ray sources with weak lensing, using photometric redshifts from the full set of BVRz' imaging to properly weight background galaxies according to their lensing distance ratios. We fit both NFW and singular isothermal sphere profiles, and find that the results are insensitive to the assumed profile. We also show that the results do not depend significantly on the assumed prior on the position of the mass peak, but that this may become an issue in future larger samples. The inferred velocity dispersions for the extended X-ray sources range from 250-800 km/s, with the exception of one source for which no lensing signal was found. This work further establishes shear selection as a viable technique for finding clusters, but also highlights some unresolved issues such as determination of the mass profile center without biasing the mass estimate, and fully accounting for line-of-sight projections. A follow-up paper will examine the mass-X-ray scaling relations of these clusters.Comment: Accepted for publication in ApJ, 27 pages, 4 figures. Some discussion and clarification added. Cluster centre offset added to Table
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