Adjusting Sails: A Narrative Inquiry into the Transfer Experience of Three Secondary Teachers in the Maldives

'Adjusting Sails' is a narrative inquiry which presents the stories of three secondary teachers who underwent transfer from one school to the other in the Maldives. This metaphoric journey also describes my journey as a narrative researcher, how I sailed into unknown waters with my participants, what I discovered, and the interpretations I drew from their experiences. Semi-structured interviews of teachers and transfer managers and the analysis of official correspondence of the transfer contributed to the richness of the data. The stories of the teachers were analyzed for common themes, partially corroborated by contrasting the data gathered from interviews with two transfer managers, and written in collaboration with the participant storytellers. Trustworthiness of findings was further enforced through member-checking and adhering to reflexive procedures. The findings of this study suggest that the three teachers found the transfer quite stressful and as having impacted negatively on their emotions and professional lives. Communication issues before and after the transfer, personal perceptions associated with the transfer as well as leadership practices in their new environments appeared to have given rise to de-motivation, stress and frustrations. Apart from contributing to existing literature on teacher transfer, this study highlighted factors that made the transfer a negative experience for teachers and provided evidence which may usefully inform school managements and future transfer policies on the impact a transfer can have on the emotional and professional well-being of teachers

The Role of Triplet Exciton Diffusion in Light-Upconverting Polymer Glasses

Light upconversion (UC) via triplet–triplet annihilation (TTA) by using noncoherent photoexcitation at subsolar irradiance power densities is extremely attractive, particularly for enhanced solar energy harvesting. Unfortunately, practical TTA-UC application is hampered by low UC efficiency of upconverting polymer glasses, which is commonly attributed to poor exciton diffusion of the triplet excitons across emitter molecules. The present study addresses this issue by systematically evaluating triplet exciton diffusion coefficients and diffusion lengths (<i>L</i>_D) in a UC model system based on platinum-octaethylporphyrin-sensitized poly­(methyl methacrylate)/diphenylanthracene (emitter) films as a function of emitter concentration (15–40 wt %). For this evaluation time-resolved photoluminescence bulk-quenching technique followed by Stern–Volmer-type quenching analysis of experimental data was employed. The key finding is that although increasing emitter concentration in the disordered PMMA/DPA/PtOEP films improves triplet exciton diffusion, and thus <i>L</i>_D, this does not result in enhanced UC quantum yield. Conversely, improved <i>L</i>_D accompanied by the accelerated decay of UC intensity on millisecond time scale degrades TTA-UC performance at high emitter loadings (>25 wt %) and suggests that diffusion-enhanced nonradiative decay of triplet excitons is the major limiting factor

Biosensors Based on Porous Cellulose Nanocrystal–Poly(vinyl Alcohol) Scaffolds

Cellulose nanocrystals (CNCs), which offer a high aspect ratio, large specific surface area, and large number of reactive surface groups, are well suited for the facile immobilization of high density biological probes. We here report functional high surface area scaffolds based on cellulose nanocrystals (CNCs) and poly­(vinyl alcohol) (PVA) and demonstrate that this platform is useful for fluorescence-based sensing schemes. Porous CNC/PVA nanocomposite films with a thickness of 25–70 nm were deposited on glass substrates by dip-coating with an aqueous mixture of the CNCs and PVA, and the porous nanostructure was fixated by heat treatment. In a subsequent step, a portion of the scaffold’s hydroxyl surface groups was reacted with 2-(acryloxy)­ethyl (3-isocyanato-4-methylphenyl)­carbamate to permit the immobilization of thiolated fluorescein-substituted lysine, which was used as a first sensing motif, via nucleophile-based thiol–ene Michael addition. The resulting sensor films exhibit a nearly instantaneous and pronounced change of their fluorescence emission intensity in response to changes in pH. The approach was further extended to the detection of protease activity by immobilizing a Förster-type resonance energy transfer chromophore pair via a labile peptide sequence to the scaffold. This sensing scheme is based on the degradation of the protein linker in the presence of appropriate enzymes, which separate the chromophores and causes a turn-on of the originally quenched fluorescence. Using a standard benchtop spectrometer to monitor the increase in fluorescence intensity, trypsin was detected at a concentration of 250 μg/mL, i.e., in a concentration that is typical for abnormal proteolytic activity in wound fluids

La naissance des jeux olympiques et le sport dans l'antiquité

The ultrasound-induced cleavage of macromolecules has become a routine experiment in the emerging field of polymer mechanochemistry. To date, it has not been conclusively proven whether the molecular weight of a polymer or its contour length is the determining factor for chain scission upon ultrasonication. Here we report comparative experiments that confirm unequivocally that the contour length is the decisive parameter. We utilized postpolymerization modifications of specifically designed precursor polymers to create polymers with identical chain length but different molecular mass. To demonstrate the universality of the findings, two different polymer backbones were utilizedpoly­(styrene) and poly­(norbornene imide alkyne)whose molecular weights were altered by bromination and removal of pendant triisopropylsilyl protecting groups, respectively. Solutions of the respective polymer pairs were subjected to pulsed ultrasound at 20 kHz and 10.4 W/cm² in order to investigate the chain scission trends. The effects of cleavage and sonochemical treatments were monitored by size exclusion chromatography. In both series, experimental data and calculations show that the molecular weight reduction upon sonication is the same for polymers with the same contour length