Validation of a videogrammetry technique for analysing American football helmet kinematics

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.     

Significance of context in university students' (meta)cognitions related to group work: A multi-layered,multi-dimensional and cultural approach

This article examines the significance of context in university students' development of (meta)cognitions related to a specific group assignment. For this purpose context was conceptualised at two levels: class (Business, Science) and small groups within class (culturally diverse, non-diverse). Diverging trends in (meta)cognitions emerged at class and small group levels, which reflected affordances and constraints of the learning contexts. The value of incorporating a cultural angle in research on group work was confirmed. Overall, the findings highlight the usefulness of a multi-layered learning contexts design for enhancing our understanding of the developing nature of students' multi-dimensional experiences of group work.     

‘And When did You Last See Your Father?’ Exploring the Views of Children with Learning Difficulties/Disabilities

The Gulliford Lecture 2003 was given by Professor Ann Lewis of the School of Education at the University of Birmingham. Professor Lewis's lecture, on which this article is based, focused on the process of listening to the views of children and, in particular, children with learning difficulties. Following the near-universal ratification of the United Nations (UN) Convention on the Rights of the Child, a plethora of recent initiatives, both in the UK and internationally, has encouraged professionals to access children's views about provision (educational, health-related, social and legal). A range of materials has been developed to support this process, often by, or in liaison with, children's charities. At the same time, research provides valuable insights into effective practice in exploring the views of children with learning difficulties. In this article, Ann Lewis reviews ten strategies for gathering the views of children and raises four challenges for the further development of policy and practice. She closes her argument with a call for greater rigour and critical evaluation in this crucial and demanding area.     

Changes that Occur in Families as Children with Intellectual Disability Grow Up

The effect on families and the changes that occur in relation to a child with disability or independently are considered through the life span. The recent advances in prenatal screening, special care baby units and genetic counselling may increase fear of disability and have not decreased the incidence. As the rest of the family grow older, the disabled child goes through school years, faces adult life, often with disappointments, and remains having special needs and specific vulnerability until old age.     

PLURALISTIC IGNORANCE AND THE CLIMATE OF OPINION IN A REAL-TIME DISASTER PREDICTION

This study employed a four-fold typology of opinion groups depictingthe relationships between minority–majority status andaccurate–inaccurate perception of the climate of opinionabout the 1990 prediction of a destructive earthquake for themid-United States New Madrid Seismic Zone. Data were collectedfrom 629 residents of the area where the earthquake was predictedto occur. Two frameworks were employed to define the climateof opinion to take into account two key variables that influencepublic response to earthquake predictions: the predication'sbelievability and its importance. Accurate perceptions of theclimate of opinion were differntiated from inaccurate perceptionsbased on more frequent media use and the confidence respondentsfelt about protecting themselves from potential earthquake damages.Inaccurate perceptions of the climate of opinion are differentiatednot by more extensive media use and discussions, but by thecrediability placed on the information from the news media anddiscussions, as well as the perceived influence of these informationsources.     

African American Othermothering in the Urban Elementary School

Othermothering and community othermothering can be defined as African American women's maternal assistance offered to the children of blood mothers within the African American community. Originally traced to slavery, othermothering was a survival mechanism that served as a vehicle for educational and cultural transmission. Currently, an othermothering tradition exists within the urban elementary-school context, and African American female educators play an integral role in fulfilling the pyschoeducational needs of the urban child. By employing a qualitative methodology, this article presents two biographical portraits that examine othermothering by a young elementary-school principal and community othermothering by a fifth-grade elementary-school teacher with 25 years of experience in the urban classroom.