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ABSTRACT

Professional American football games are recorded in digital video with multiple cameras, often at high resolution and high frame rates. The purpose of this study was to evaluate the accuracy of a videogrammetry technique to calculate translational and rotational helmet velocity before, during and after a helmet impact. In total, 10 football impacts were staged in a National Football League (NFL) stadium by propelling helmeted 50th percentile male crash test dummies into each other or the ground at speeds and orientations representative of concussive impacts for NFL players. The tests were recorded by experienced sports film crews to obtain video coverage and quality typically available for NFL games. A videogrammetry procedure was used to track the position and rotation of the helmet throughout the relevant time interval of the head impact. Compared with rigidly mounted retroreflective marker three dimensional (3-D) motion tracking that was concurrently collected in the experiments, videogrammetry accurately calculated changes in translational and rotational velocity of the helmet using high frame rate (two cameras at 240 Hz) video (7% and 15% error, respectively). Low frame rate (2 cameras at 60 Hz) video was adequate for calculating pre-impact translational velocity but not for calculating the translational or rotational velocity change of the helmet during impact.  相似文献   
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In typical development, gestures precede and predict language development. This study examines the developmental sequence of expressive communication and relations between specific gestural and language milestones in toddlers with autism spectrum disorder (ASD), who demonstrate marked difficulty with gesture production and language. Communication skills across five stages (gestures, word approximations, first words, gesture-word combinations, and two-word combinations) were assessed monthly by blind raters for toddlers with ASD participating in an randomized control trial of parent-mediated treatment (N = 42, 12–30 months). Findings revealed that toddlers acquired skills following a reliable (vs. idiosyncratic) sequence and the majority of toddlers combined gestures with words before combining words in speech, but in contrast to the pattern observed in typical development, a significant subset acquired pointing after first words.  相似文献   
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Mathematics educators have long emphasised the importance of attitudes, beliefs, and feelings towards mathematics, as crucial in motivating (or not) its learning and use, and as influenced in turn by its social images. This paper is about images of mathematics. Our search for advertisements containing such images in UK daily newspapers, during 2006–2008, found that 4.7 % of editions included a “mathematical” advert, compared with 1.7 % in pilot work for 1994–2003. The incidence varied across type of newspaper, being correlated with class and gender profiles of the readership. Three quarters of advertisements were classified as containing only very simple mathematics. ‘Semiotic discursive’ analysis of selected advertisements suggests that they draw on mathematics not to inform, but to connote qualities like precision, certainty, and authority. We discuss the discourse on mathematics in advertising as ‘quasi-pedagogic’ discourse, and argue that its oversimplified forms, being empty of mathematical content, become powerful means for regulating and ‘pedagogising’ today's global consumers.  相似文献   
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The clinical use of ultrasound has dramatically increased, necessitating early ultrasound education and the development of new tools in ultrasound training and assessment. The goal of this study was to devise a novel low-resource examination that tested the anatomical knowledge and technical skill of early undergraduate medical students in a gross anatomy course. The team-based ultrasound objective structured practice examination (OSPE) was created as a method for assessing practical ultrasound competencies, anatomical knowledge, and non-technical skills such as teamwork and professionalism. The examination utilized a rotation of students through four team roles as they scanned different areas of the body. This station-based examination required four models and four instructors, and tested ultrasound skills in the heart, abdominal vessels, abdominal organs, and neck regions. A Likert scale survey assessed student attitudes toward the examination. Survey data from participants (n = 46) were examined along with OSPE examination grades (n = 52). Mean and standard deviations were calculated for examination items and survey responses. Student grades were high in both technical (96.5%). and professional (96.5%) competencies with structure identification scoring the lowest (93.8%). There were no statistical differences between performances in each of the body regions being scanned. The survey showed that students deemed the examination to be fair and effective. In addition, students agreed that the examination motivated them to practice ultrasound. The team-based OSPE was found to be an efficient and student-favored method for evaluating integrated ultrasound competencies, anatomical knowledge, team-work, and professional attributes.  相似文献   
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This study relies on data from 388 junior and senior criminal justice majors to examine predictors of intentions to pursue graduate education in criminology, criminal justice, or a closely related field. Logistic regression results demonstrate that women, students who receive greater encouragement to attend graduate school, students with a lower aversion to reading, writing, and statistics, and students who perceive greater diversity intolerance are more likely to report graduate school intentions. Although students’ race was not found to be significant in the overall model, split-sample models revealed that the significance of predictors varied by race and ethnicity. In discussing the findings, special attention is given to the need for primarily White institutions (PWIs) to partner with historically Black college and universities (HBCUs). We conclude by calling for departments to redouble their efforts to diversify their faculty and student bodies.  相似文献   
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正多年前,俄勒冈靠金矿吸引了全世界的眼球;如今,俄勒冈继续以它的美丽和真实闪耀在世人面前。本期,旅居中国的Jeff Gerdes将带领我们感受他眼中的俄勒冈:无论是这里秀丽的自然风光,还是深厚的文化底蕴,相信都能让你领略到这个位于美国西海岸小州的独特之美。  相似文献   
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