The force-time profile of elite front crawl swimmers

In this study, we used recently developed technology to determine the force-time profile of elite swimmers, which enabled coaches to make informed decisions on technique modifications. Eight elite male swimmers with a FINA (Federation Internationale de Natation) rank of 900+ completed five passive (streamline tow) and five net force (arms and leg swimming) trials. Three 50-Hz cameras were used to video each trial and were synchronized to the kinetic data output from a force-platform, upon which a motorized towing device was mounted. Passive and net force trials were completed at the participant's maximal front crawl swimming velocity. For the constant tow velocity, the net force profile was presented as a force-time graph, and the limitation of a constant velocity assumption was acknowledged. This allowed minimum and maximum net forces and arm symmetry to be identified. At a mean velocity of 1.92+0.06 m s?1, the mean passive drag for the swimmers was 80.3+4.0 N, and the mean net force was 262.4+33.4 N. The mean location in the stroke cycle for minimum and maximum net force production was at 45% (insweep phase) and 75% (upsweep phase) of the stroke, respectively. This force-time profile also identified any stroke asymmetry.     

The possibility of deliberate norm-adherence in AI

Ethics and Information Technology - Moral agency status is often given to those individuals or entities which act intentionally within a society or environment. In the past, moral agency has...     

Bandpass sorting of heterogeneous cells using a single surface acoustic wave transducer pair

Separation and sorting of biological entities (viruses, bacteria, and cells) is a critical step in any microfluidic lab-on-a-chip device. Acoustofluidics platforms have demonstrated their ability to use physical characteristics of cells to perform label-free separation. Bandpass-type sorting methods of medium-sized entities from a mixture have been presented using acoustic techniques; however, they require multiple transducers, lack support for various target populations, can be sensitive to flow variations, or have not been verified for continuous flow sorting of biological cells. To our knowledge, this paper presents the first acoustic bandpass method that overcomes all these limitations and presents an inherently reconfigurable technique with a single transducer pair for stable continuous flow sorting of blood cells. The sorting method is first demonstrated for polystyrene particles of sizes 6, 10, and 14.5 μm in diameter with measured purity and efficiency coefficients above 75 ± 6% and 85 ± 9%, respectively. The sorting strategy was further validated in the separation of red blood cells from white blood cells and 1 μm polystyrene particles with 78 ± 8% efficiency and 74 ± 6% purity, respectively, at a flow rate of at least 1 μl/min, enabling to process finger prick blood samples within minutes.     

Tweet Up? Examining Twitter's Impact on Social Capital and Digital Citizenship in Higher Education

Twitter is a highly accessible communication venue that is embraced by great numbers of traditionally aged and ethnically diverse college students. Danielle Morgan Acosta challenges us to turn our research and teaching attention to the potential of Twitter to support student learning.     

An Investigation of How a Physics Professional Development Course Influenced the Teaching Practices of Five Elementary School Teachers

This paper reports the results of an investigation of how a professional development content course based on the Physics and Everyday Thinking (PET) curriculum affected the teaching practices of five case study elementary school teachers. The findings of this study highlight different ways that teachers use what they learn in content courses to teach science to elementary children. While some teachers transferred pedagogical practices along with the content, others transformed the content to be useful in already existing pedagogical frameworks, and still others show little or no evidence of transfer. The range of transfer is explained by considering how each teacher interacted with the learning context (the PET curriculum) and their initial ideas about teaching science.     

In vitro antioxidant activity and potential inhibitory action against α-glucosidase of polysaccharides from fruit peel oftea (Camellia sinensis L.)简

The conditions for extracting polysaccharides from tea (Camellia sinensis L.) fruit peel (TFPPs) were studied. Three parameters (temperature, time, and liquid/solid ratio) affecting the extraction of TFPP were optimized using response surface methodology (RSM). Under the optimized conditions, the yield of TFPP was predicted to be 4.98%. The physicochemical properties, in vitro antioxidant activities, and inhibitory effects on α-glucosidase of fractionated TFPPs (TFPP-0, TFPP-20, TFPP-40, and TFPP-60) were investigated. We found that the TFPPs were all acid protein-bound heteropolysaccharides, although with different chemical compositions. They had not only remarkable scavenging activity on 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and reducing activity, but also excellent inhibitory potential against α-glucosidase in vitro. Our results suggest that tea fruit peel could be treated as a potential bioresource for the development of polysaccharide antioxidants.