Polyelectrolyte multilayer surface functionalization of poly(dimethylsiloxane) (PDMS) for reduction of yeast cell adhesion in microfluidic devices

Polyelectrolyte multilayers (PEMs) based on the combinations poly(diallyldimethylammonium chloride)∕poly(acrylic acid) (PDADMAC∕PAA) and poly(allylamine hydrochloride)∕PAA (PAH∕PAA) were adsorbed on poly(dimethylsiloxane) (PDMS) and tested for nonspecific surface attachment of hydrophobic yeast cells using a parallel plate flow chamber. A custom-made graft copolymer containing poly(ethylene glycol) (PEG) side chains (PAA-g-PEG) was additionally adsorbed on the PEMs as a terminal layer. A suitable PEM modification effectively decreased the adhesion strength of Saccharomyces cerevisiae DSM 2155 to the channel walls. However, a further decrease in initial cell attachment and adhesion strength was observed after adsorption of PAA-g-PEG copolymer onto PEMs from aqueous solution. The results demonstrate that a facile layer-by-layer surface functionalization from aqueous solutions can be successfully applied to reduce cell adhesion strength of S. cerevisiae by at least two orders of magnitude compared to bare PDMS. Therefore, this method is potentially suitable to promote planktonic growth inside capped PDMS-based microfluidic devices if the PEM deposition is completed by a dynamic flow-through process.     

Does local dynamic stability of kayak paddling technique affect the sports performance? A pilot study

During competition, kayak athletes must optimally adapt to environmental factors (e.g. wind, waves) to achieve peak performance. However, the ability to adapt to such perturbations has never been assessed in kayak paddling. Therefore, the aim of the current study was to evaluate the local dynamic stability in sports technique of youth sprint kayak athletes. In a cross-sectional study, 14 healthy male athletes were recruited from an elite youth sprint kayak squad. During an incremental kayak ergometer test, mean power, heart rates and local dynamic technique stability of hands, arms, trunk and paddle were registered and the association with the athletes 2000?m free-water times were estimated using mixed models. The 2000?m free-water performance significantly predicted the paddles (p?=?.037) local dynamic stability whereas no association was found for the trunk or the upper extremity kinematics. In conclusion, kayak athletes with high-performance capability over 2000?m paddling depict high local dynamic technique stability. This emphasizes the importance of a stable technique for advanced kayak skills, especially regarding paddling movements.     

The publishing imperative: the pervasive influence of publication metrics

This article summarizes the effects of the increasing global trend towards measuring research quality and effectiveness through, in particular, publication‐based metrics, and its effects on scholarly communication. Such metrics are increasingly influencing the behaviour patterns of administrators, publishers, librarians, and researchers. Impact and citation measures, which often rely solely on Thomson Scientific data, are examined in the context of university league tables and research assessment exercises. The need to establish alternate metrics, particularly for the social sciences and humanities, is emphasized, as is an holistic approach to scholarly communication agenda.     

Relationships between mathematical knowledge for teaching and teaching practice: the case of proof

Teachers of mathematics orchestrate opportunities for interactions between learners and subject matter. Therefore, mathematics teachers need rich, multidimensional content knowledge for teaching mathematics, which incorporates knowledge of the subject matter, students, and teaching. Studying this mathematical knowledge for teaching (MKT) necessitates more than a unidirectional assessment. In this study, the mathematical knowledge for teaching reasoning and proving of two secondary mathematics teachers was investigated through classroom observations and clinical assessments. Results indicate that using MKT as a frame for examining classroom practice, in addition to assessing the MKT a teacher possesses in a clinical setting, provides an in-depth and innovative method for investigating MKT. The comparison of the two cases also identifies student positioning as a key mediating factor between MKT and opportunities to learn. Implications for using MKT as a lens for examining practice in teacher education are discussed.