Kinetic and kinematic analysis of stamping impacts during simulated rucking in rugby union

Laceration injuries account for up to 23% of injuries in rugby union. They are frequently caused by studded footwear as a result of a player stamping onto another player during the ruck. Little is known about the kinetics and kinematics of rugby stamping impacts; current test methods assessing laceration injury risk of stud designs therefore lack informed test parameters. In this study, twelve participants stamped on an anthropomorphic test device in a one-on-one simulated ruck setting. Velocity and inclination angle of the foot prior to impact was determined from high-speed video footage. Total stamping force and individual stud force were measured using pressure sensors. Mean foot inbound velocity was 4.3 m ? s^?1 (range 2.1–6.3 m ? s^?1). Mean peak total force was 1246 N and mean peak stud force was 214 N. The total mean effective mass during stamping was 6.6 kg (range: 1.6–13.5 kg) and stud effective mass was 1.2 kg (range: 0.5–2.9 kg). These results provide representative test parameters for mechanical test devices designed to assess laceration injury risk of studded footwear for rugby union.     

Alternating current-dielectrophoresis driven on-chip collection and chaining of green microalgae in freshwaters

The capability of the AC dielectrophoresis (DEP) for on-chip capture and chaining of microalgae suspended in freshwaters was evaluated. The effects of freshwater composition as well as the electric field voltage, frequency, and duration, on the dielectrophoretic response of microalga Chlamydomonas reinhardtii were characterized systematically. Highest efficiency of cell alignment in one-dimensional arrays, determined by the percentage of cells in chain and the chain length, was obtained at AC-field of 20 V mm⁻¹ and 1 kHz applied for 600 s. The DEP response and cell alignment of C. reinhardtii in water sampled from lake, pond, and river, as well as model media were affected by the chemical composition of the media. In the model media, the efficiency of DEP chaining was negatively correlated to the conductivity of the cell suspensions, being higher in suspensions with low conductivity. The cells suspended in freshwaters, however, showed anomalously high chaining at long exposure times. High concentrations of nitrate and dissolved organic matter decrease cell chaining efficiency, while phosphate and citrate concentrations increase it and favor formation of longer chains. Importantly, the application of AC-field had no effect on algal autofluorescence, cell membrane damage, or oxidative stress damages in C. reinhardtii.     

Making it happen: Possibilities and pitfalls of Cunningham's educational semiotic

In fundamental agreement with Cunningham's overall thesis, we attempt in this paper to articulate what an educational semiotic might look like on a practical level. For educational psychologists, it should mean an increased awareness of the limited, localized world views offered by current models of cognition and an increased attentiveness to alternate models. For teachers, an educational semiotic offers integration of cognition and affect and instructional strategies that depend upon and facilitate many ways of knowing. For an educational semiotic to be realized, however, there must be much greater attention paid to the roles of motivation and metacognition in semiotic pedagogy.     

Dominance relationships in femaleHerotilapia multispinosa (Pisces: Cichlidae)

Agonistic interactions between all possible pairings of 10 adult female rainbow cichlids (Herotilapia multispinosa) were observed in three round-robin tournaments. Specific behaviors and color patterns were found to characterize winning and losing fish. The outcomes of agonistic encounters were used to construct a hypothetical dominance hierarchy. This hierarchy was consistent over the three tournaments in that (1) the order of animals in the hierarchy remained relatively unchanged and (2) the relationship between the members of a particular dyad tended to remain stable. The latter was especially true for fish of widely different dominance rank.     

Improving energy expenditure estimates from wearable devices: A machine learning approach

ABSTRACT

A means of quantifying continuous, free-living energy expenditure (EE) would advance the study of bioenergetics. The aim of this study was to apply a non-linear, machine learning algorithm (random forest) to predict minute level EE for a range of activities using acceleration, physiological signals (e.g., heart rate, body temperature, galvanic skin response), and participant characteristics (e.g., sex, age, height, weight, body composition) collected from wearable devices (Fitbit charge 2, Polar H7, SenseWear Armband Mini and Actigraph GT3-x) as potential inputs. By utilising a leave-one-out cross-validation approach in 59 subjects, we investigated the predictive accuracy in sedentary, ambulatory, household, and cycling activities compared to indirect calorimetry (Vyntus CPX). Over all activities, correlations of at least r = 0.85 were achieved by the models. Root mean squared error ranged from 1 to 1.37 METs and all overall models were statistically equivalent to the criterion measure. Significantly lower error was observed for Actigraph and Sensewear models, when compared to the manufacturer provided estimates of the Sensewear Armband (p < 0.05). A high degree of accuracy in EE estimation was achieved by applying non-linear models to wearable devices which may offer a means to capture the energy cost of free-living activities.     

Measures of cognitive structure: Do they assess learning at the level of comprehension?

One purpose of this study was to determine whether cognitive structure, assessed by psychometric measures of concept interrelatedness, can be developed when the students initially do not know what concept relationships exist and what they mean. The second purpose was to apply those measures to a learning situation that has produced a nonspecific transfer effect, i.e., the facilitative effect of concrete examples on learning abstract passages, to attempt to explain this effect more completely. Five groups of 20 students each read two prose passages and took recall and structure assessment tests on the second passage. Results (1) indicated that the nonspecific facilitative transfer effect was replicated and (2) offered some support for the contention that the cognitive structure which proximity measures assess can be trained to correspond to content structure, but that related recall remains low. With resolution of some of the methodological issues surrounding these measures, however, clearer explanation of transfer effects and assessment of higher order learning may be facilitated.     

Primary grade student reports for teacher evaluation

The improvement of teacher evaluation is an important theme in current public school reform efforts. One change, suggested by a number of researchers, is to gather more lines of evidence or perspectives of teacher performance for decision making. Student views, commonly used in higher education, are advocated as one data source about teacher quality. Although it is clear that students of all ages can provide some perspective on teacher performance, substantial questions remain about using the views of young pupils.The purpose of this study was to empirically examine a sample of student reports of teacher performance from kindergarten through second grade. The analysis used procedures developed for student rating forms in higher education. The objective was to advance understanding and practice about effective teacher evaluation, specifically in the use of pupil report data.     

Collaborative knowledge building: A case study

What learning conditions are necessary to effectively support the knowledge-building enterprise in a learning community? To answer this question, the case-study method was employed to investigate collaborative knowledge building in a graduate level course designed to incorporate specific constructivist learning principles. These principles included (a) having a collective and authentic community goal to facilitate collaboration and engagement in the community, (b) using cooperative groups to provide for social negotiation and to promote multiple perspectives, (c) personally selecting of course readings and group decision-making to encourage ownership in learning, and (d) employing an integrated set of technology tools to archive the work of the community and facilitate communication. Results indicated that the instructional strategies designed into the course promoted collaborative knowledge building and the acquisition of key concepts through self-directed learning strategies. Results also pointed out the types of technological support required to implement an effective community of learners. A proposed set of guidelines is discussed to assist instructional designers in the design and development of collaborative, knowledge-building environments.