Luminescent solar concentrators (LSCs) use down-converting phosphors embedded in a transparent waveguide to absorb sunlight, trap luminescent photons by total internal reflection, and deliver high irradiance, narrowband output light for driving photovoltaic, photochemical, and other solar energy converters. Quantum-dot-based (QD) LSCs are typically affected by several optical loss mechanisms including the loss of a fraction of guided light during transport to the concentrator edges through scattering from QD aggregates. Although the recent introduction of large effective Stokes shift QD luminophores for LSC applications has helped address several shortcomings associated with previous generations of organic and inorganic dyes, including improved solar spectrum matching, photostability, and photoluminescence quantum yield, achieving low light scattering at technologically relevant QD loadings in commercially deployed polymers such as poly(methyl methacrylate) (PMMA) remains challenging. Herein, we study the concept of applying QDs bearing polymer ligands matching the composition of the LSC matrix to reduce aggregation and the resulting parasitic waveguide losses caused by scattering. We report the synthesis and characterization of a thiol-terminated PMMA-based ligand and its successful ligand exchange reaction with copper indium disulfide/zinc sulfide (CIS/ZnS) QDs. QDs bearing PMMA ligands are then applied as down-converting phosphors embedded in a PMMA waveguide. The resulting QD-based LSCs were found to have lower optical scattering with higher loading as a result of reduced aggregation in the devices.
Background/Aims: Falls are an increasing problem in the elderly population. Several pieces of primary and secondary research have been carried out into the effectiveness of Tai Chi as a falls prevention intervention. Benefits such as improvements in balance, dual task working, and proprioception have been reported. Nevertheless, the research remains inconclusive. There is uncertainty regarding an optimum Tai Chi style, dosage, and patient characteristics for whom Tai Chi is most suitable. This review aims to explore and discuss the current best evidence to assess the efficacy of Tai Chi as a falls prevention strategy for adults aged 65 and over. Methods: A systematic literature search was carried out using CINAHL, MEDLINE and AMED, along with predetermined inclusion and exclusion criteria, eventually yielding four papers for the review. Narrative synthesis was then carried out to identify themes to answer the research aim. Some evidence showed that although Tai Chi is effective for reducing falls in the population aged 65 and over, the body of evidence did not conclude this effect to be significant. Conclusions: There is some evidence for positive intervention effects in the pre-frail subgroup of the population; however, more research is needed to confirm this. A multidimensional falls prevention programme may prove more beneficial for falls prevention in the elderly at present—although Tai Chi could indeed be an element of this.
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