Acting White: A Critical Review

The hypothesis of acting White has been heatedly debated and influential over the last 20 years or so in explaining the Black–White test score gap. Recently, economists have joined the debate and started providing new theoretical and empirical analyses of the phenomenon. This paper critically reviews the arguments that have been advanced to support and refute the hypothesis. This review particularly covers the analyses in economics because the economic analyses are relatively new and usually neglected in other disciplines. Also, nationally representative data are emphasized, whenever possible, to improve the generalizability of the arguments. This review concludes that although the analyses in both non-economics and economics are thought-provoking and compelling in some respect, a substantial body of empirical evidence is inconsistent with the assumptions of and results from the analyses.     

Applying computerized-scoring models of written biological explanations across courses and colleges: prospects and limitations

Our study explored the prospects and limitations of using machine-learning software to score introductory biology students’ written explanations of evolutionary change. We investigated three research questions: 1) Do scoring models built using student responses at one university function effectively at another university? 2) How many human-scored student responses are needed to build scoring models suitable for cross-institutional application? 3) What factors limit computer-scoring efficacy, and how can these factors be mitigated? To answer these questions, two biology experts scored a corpus of 2556 short-answer explanations (from biology majors and nonmajors) at two universities for the presence or absence of five key concepts of evolution. Human- and computer-generated scores were compared using kappa agreement statistics. We found that machine-learning software was capable in most cases of accurately evaluating the degree of scientific sophistication in undergraduate majors’ and nonmajors’ written explanations of evolutionary change. In cases in which the software did not perform at the benchmark of “near-perfect” agreement (kappa > 0.80), we located the causes of poor performance and identified a series of strategies for their mitigation. Machine-learning software holds promise as an assessment tool for use in undergraduate biology education, but like most assessment tools, it is also characterized by limitations.     

Harnessing technology to improve formative assessment of student conceptions in STEM: forging a national network

Concept inventories, consisting of multiple-choice questions designed around common student misconceptions, are designed to reveal student thinking. However, students often have complex, heterogeneous ideas about scientific concepts. Constructed-response assessments, in which students must create their own answer, may better reveal students' thinking, but are time- and resource-intensive to evaluate. This report describes the initial meeting of a National Science Foundation-funded cross-institutional collaboration of interdisciplinary science, technology, engineering, and mathematics (STEM) education researchers interested in exploring the use of automated text analysis to evaluate constructed-response assessments. Participants at the meeting shared existing work on lexical analysis and concept inventories, participated in technology demonstrations and workshops, and discussed research goals. We are seeking interested collaborators to join our research community.     

Engineering the race car wing: application of the vortex panel numerical method

This study examined aerodynamic properties and boundary layer stability in five cambered airfoils operating at the low Reynolds numbers encountered in motor racing. Numerical modelling was carried out in the flow regime characterised by Reynolds numbers 0.82–1.29 × 10⁶. The design Reynolds number of 3 × 10⁶ was used as a reference. Aerodynamics variables were computed using AeroFoil 2.2 software, which uses the vortex panel method and integral boundary layer equations. Validation of AeroFoil 2.2 software showed very good agreement between calculated aerodynamic coefficients and wind tunnel experimental data. Drag polars, lift/drag ratio, pitching moment coefficient, chordwise distributions (surface velocity ratio, pressure coefficient and boundary layer thickness), stagnation point, and boundary layer transition and separation were obtained at angles of attack from −4° to 12°. The NASA NLF(1)-0414F airfoil offers versatility for motor racing with a wide low-drag bucket, low minimum profile drag, high lift/drag ratio, laminar flow up to 0.7 chord, rapid concave pressure recovery, high resultant pressure coefficient and stall resistance at low Reynolds numbers. The findings have implications for the design of race car wings.     

The effects of testing procedure on critical fall height determination for third-generation synthetic turf

Test procedures and their accuracy in determining critical fall height (CFH) on sporting grounds are paramount to player safety. The procedure currently adopted for synthetic turf in Australian football [1] consists of four consecutive drops at various drop heights at three test locations on the sample. The quantity and packing of the infill in third-generation turf and the pooling effect of the rubber particles with consecutive drops suggests that the current standard protocol may need re-assessment. Therefore, the purpose of this pilot study was to investigate whether current methods of testing for CFH are appropriate for third-generation synthetic turf or whether an alternative or adapted method needs to be developed. CFH was measured, using a HISUN Uniaxe-II Impact Tester, on 12 combinations of synthetic turf samples (four different products with three shock pad options). Three conditions were investigated on each sample; the existing protocol; an alternative 12 single-drop protocol and four single drops from the CFH determined from the existing protocol. A significant difference was found for both absolute and percentage difference between the existing and 12 single-drop protocol, with p = 0.001 and t = 4.33 and p < 0.001 and t = 6.03, respectively. There was also a significant difference between the CFH reached with and without a shock pad for both the existing protocol and the 12 single-drop protocol. The results of this pilot study demonstrate that differences do occur with alterations to the existing protocol and highlight the need for a more detailed characterisation of testing methods on third-generation synthetic turf and the response of surfaces to them.     

Three-dimensional kinematic analysis of the golf swing using instantaneous screw axis theory,Part 2: golf swing kinematic sequence

A number of recent studies have measured the extent and timing of segment rotation during the golf swing. A promising technique, instantaneous screw axis (ISA) theory, could provide a better expression of segment rotation. In Part 1 of this two-part study, the objectives are to identify the ISA of the pelvis, shoulders and left arm during the downswing, compute segment angular velocity relative to that segment’s ISA and verify that ISA theory is a valid tool to analyse segment rotation during the golf swing. Results indicate that for all subjects, at least 71% of marker velocity is a result of rotation about their respective ISA, when averaging results over the duration of the downswing, confirming that motion is primarily rotational. Furthermore, ISA position and orientation of each segment approaches, on average, the expected gross axis of rotation, confirming that motion about the ISA is representative of joint motion.     

Neuromuscular control and running economy is preserved in elite international triathletes after cycling

Running is the most important discipline for Olympic triathlon success. However, cycling impairs running muscle recruitment and performance in some highly trained triathletes; though it is not known if this occurs in elite international triathletes. The purpose of this study was to investigate the effect of cycling in two different protocols on running economy and neuromuscular control in elite international triathletes. Muscle recruitment and sagittal plane joint angles of the left lower extremity and running economy were compared between control (no preceding cycle) and transition (preceded by cycling) runs for two different cycle protocols (20-minute low-intensity and 50-minute high-intensity cycles) in seven elite international triathletes. Muscle recruitment and joint angles were not different between control and transition runs for either cycle protocols. Running economy was also not different between control and transition runs for the low-intensity (62.4 +/- 4.5 vs. 62.1 +/- 4.0 ml/min/kg, p > 0.05) and high-intensity (63.4 +/- 3.5 vs. 63.3 +/- 4.3 ml/min/kg, p > 0.05) cycle protocols. The results of this study demonstrate that both low- and high-intensity cycles do not adversely influence neuromuscular control and running economy in elite international triathletes.