Raising the standards by standardization?

Journal of Mathematics Teacher Education -     

An evaluation of biomechanical measures of bowling action legality in cricket

Cricket bowling is traditionally thought to be a rigid-arm motion, allowing no elbow straightening during the delivery phase. Conversely, research has shown that a perfectly rigid arm through delivery is practically unattainable, which has led to rule changes over the past years. The current rule requires a bowler not to increase the elbow angle by more than 15 degrees, thus requiring a measurement to confirm legality in "suspect" bowlers. The aims of this study were to evaluate whether the current rule is maintained over a range of bowlers and bowling styles, and to ascertain whether other kinematics measures may better differentiate between legal and suspect bowling actions. Eighty-three bowlers of varying pace were analysed using reflective markers and a high-speed (240 Hz) eight-camera motion analysis system in a laboratory. The change in elbow segment angle (minimum angle between the arm and forearm), the change in elbow extension angle with respect to the flexion-extension axis of a joint coordinate system, and the elbow extension angular velocity at ball release were measured. We found that bowlers generally bowled within a change in elbow extension angle of 15.5 degrees. However, this limit was unable to differentiate groups of bowlers from those who were suspected of throwing in the past. Improved differentiation was attained using the elbow extension angular velocity at ball release. The elbow extension angular velocity at ball release may be conceptually more valid than the elbow extension angle in determining which bowlers use the velocity-contributing mechanisms of a throw. Also, a high value of elbow extension angular velocity at ball release may be related to the visual impression of throwing. Therefore, it is recommended that researchers and cricket legislators examine the feasibility of specifying a limit to the elbow extension angular velocity at ball release to determine bowling legality.     

On demand nanoliter-scale microfluidic droplet generation,injection, and mixing using a passive microfluidic device

We here present and characterize a programmable nanoliter scale droplet-on-demand device that can be used separately or readily integrated into low cost single layer rapid prototyping microfluidic systems for a wide range of user applications. The passive microfluidic device allows external (off-the-shelf) electronically controlled pinch valves to program the delivery of nanoliter scale aqueous droplets from up to 9 different inputs to a central outlet channel. The inputs can be either continuous aqueous fluid streams or microliter scale aqueous plugs embedded in a carrier fluid, in which case the number of effective input solutions that can be employed in an experiment is no longer strongly constrained (100 s–1000 s). Both nanoliter droplet sequencing output and nanoliter-scale droplet mixing are reported with this device. Optimization of the geometry and pressure relationships in the device was achieved in several hardware iterations with the support of open source microfluidic simulation software and equivalent circuit models. The requisite modular control of pressure relationships within the device is accomplished using hydrodynamic barriers and matched resistance channels with three different channel heights, custom parallel reversible microfluidic I/O connections, low dead-volume pinch valves, and a simply adjustable array of external screw valves. Programmable sequences of droplet mixes or chains of droplets can be achieved with the device at low Hz frequencies, limited by device elasticity, and could be further enhanced by valve integration. The chip has already found use in the characterization of droplet bunching during export and the synthesis of a DNA library.     

Global Mistrust in News: The Impact of Social Media on Trust

ABSTRACT

Digital platforms such as search engines and social media have become major gateways to news. Algorithms are used to deliver news that is consistent with consumers’ preferences and individuals share news through their online social networks. This networked environment has resulted in growing uncertainty about online information which has had an impact on news industries globally. While it is well established that perceptions of trust in news found on social media or via search engines are lower than traditional news media, there has been less discussion about the impact of social media use on perceptions of trust in the news media more broadly. This study fills that gap by examining the influence of social media as news sources and pathways to news on perceptions of the level of news trust at a country level. A secondary data analysis of a 26-country survey in 2016 and 2019 was conducted. The analysis revealed an increase in social media use for accessing news resulted in a decline in trust in news media generally across the globe. Higher levels of general mistrust in news were related to an increased use of sharing of news. This paper argues the use of social media for news is closely linked to the increase in news mistrust, which is likely to continue to rise as the number of people using social media to access news continues to grow.     

Formative Assessment – Ein erfolgversprechendes Konzept zur Reform von Unterricht und Leistungsmessung?

Traditional procedures for measuring school performance, which focus on selection and grading, are being increasingly criticized for their negative effects on pupil motivation, teaching and learning processes. The German academic discussion in the field of education science is subsequently focusing on alternative forms of performance measurement and grading, e.g. using portfolios or learning diaries. International literature shows, in contrast, a broader, more empirically oriented discussion on different forms of performance measurement with the goal of optimizing teaching and learning processes (formative assessment). This theoretical paper will investigate whether a more extensive reception of the literature on formative assessment could give new impulses to the German discussion on reforming performance measurement.     

Prediction of the P-leaching potential of arable soils in areas with high livestock densities

Due to long-term positive P-balances many surface soils in areas with high livestock density in Germany are oversupplied with available P, creating a potential for vertical P losses by leaching. In extensive studies to characterize the endangering of ground water to P pollution by chemical soil parameters it is shown that the available P content and the P concentration of the soil solution in the deeper soil layers, as indicators of the P-leaching potential, cannot be satisfactorily predicted from the available P content of the topsoils. The P equilibrium concentration in the soil solution directly above ground water table or the pipe drainage system highly depends on the relative saturation of the P-sorption capacity in this layer. A saturation index of 〈20% normally corresponds with P equilibrium concentrations of〈0.2 mg P/L. Phytoremediation may reduce the P leaching potential of P-enriched soils only over a very long period.     

Neurophysiological correlates of interference control and response inhibition processes in children and adolescents engaging in open- and closed-skill sports

Background:Accumulating evidence suggests that sports participation promotes the development of inhibitory control,but the influences of the sports category and inhibition type still remain unclear.The categorization of sports based on the open-skill(externally paced)and closed-skill(self-paced)continuum allows for the integration of the environment as a factor contributing to sports-related benefits for inhibitory control.Methods:Cross-sectional data from different studies were combined(n=184)to examine the association between open-and closed-skill sports and cognitive control processes related to interference control and response inhibition.Participants(aged 9-14 years)filled in 7-day physical activity recall protocols and completed a Stroop Color-Word or a Go/NoGo task.The N200,N450,and P300 components of event-related potentials elicited by these tasks were recorded using electroencephalography.Results:Partial correlations supported the belief that time spent in open-skill sports was related to higher performance on inhibition trials.Additionally,path analyses revealed an association between this sports type and a greater negativity in the N200 and N450 amplitudes in both the full sample and group-level analyses.In contrast,no relation was found between sports type and P300 amplitude.Conclusion:The findings suggest that only the engagement in open-skill sports is associated with more effective conflict monitoring and higher performance on tasks demanding inhibitory control.     

Differences in impact characteristics,joint kinetics and measurement reliability between forehand and backhand forward badminton lunges

ABSTRACT

This study identified the effect of badminton lunging directions on impact characteristics, joint kinetics and measurement reliability. A total of 14 badminton players performed 20 lunges in both forehand and backhand sides. Ground reaction force (GRF) and three-dimensional joint moment variables were determined for further analyses. Paired t-tests and Wilcoxon signed-rank tests were performed to determine any differences between the two lunge directions and intra-class correlation (ICC) and sequential averaging analysis (SAA) were used to estimate the minimum number of trials. Compared to the forehand side, participants experienced significantly larger total GRF impulse (+ 3.8%, p = 0.021) and transverse moment (hip + 63.5%, p < 0.001; knee + 80.7%, p = 0.011), but smaller hip (?7.7%), knee (?18.7%) and ankle frontal moments (?58.0%, p < 0.05) in backhand lunges. The minimum number of trials was similar for both lunge directions, as the averaged absolute differences was less than one in both ICC and SAA. Furthermore, smaller minimal number of trials was determined by the ICC (7.9–8.0), compared with the SAA approach (9.5–10.3). Lunge direction would influence GRF and joint loading, but not on the measurement reliability. These results give important insights to establish performance or equipment evaluation protocols during badminton lunges.     

Pythagoras and Diophantus

The Theorem of Pythagoras is employed as a starting point for discussing the irrationality of the square root of 2 and its implications in Mathematics and culture. It motivates to consider the equation of the circle over the field of rational numbers and other fields which leads in a natural way t to the use of modular arithmetic for Diophantine equations.     

2. Heymann, Hans Werner (Hrsg.): Allgemeinbildung und Fachunterricht

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