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1. Adiabatic light guide with S-shaped strips

   https://doi.org/10.1063/5.0218512  

   Wojtsekhowski, B; Brash, E J; Franklin, G B; Rosso, A; Sarty, A; Shahinyan, A; Zimmerman, E (October 2024, Review of Scientific Instruments)

   A light guide is an essential part of many scintillator counters and light collection systems. Our main interest is a light guide for a thin, wide scintillator that has high light transmission while converting the area of the light source to the shape of a photo-detector. We propose a variation of the light guide that avoids a 90° twist of the strips, reduces the length of the light pipe, and reduces the complexity of production. Detailed Monte Carlo simulation studies have been performed for a three-strip S-shaped light-guide system. 

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2. Light quality and spatial variability influences on seedling regeneration in Hawaiian lowland wet forests

   https://doi.org/10.1111/1365-2664.14775  

   Rosam, Jodie R; Warman, Laura; Ostertag, Rebecca; Perroy, Ryan; Cordell, Susan (November 2024, Journal of Applied Ecology)

   Abstract Tropical forest understories tend to be light‐limited. The red‐to‐far‐red ratio (R:FR) is a useful and reliable index of light quality and its spatial variability can influence competition between native and non‐native seedlings. While per cent light transmittance has been quantified in some Hawaiian lowland wet forests (HLWF), no information exists on how the spatial distribution of understorey light varies in relation to species invasion, or if patterns of seedling regeneration and light are linked.We measured the R:FR of light in the understorey to assess light quality in three HLWF forest types: native‐dominated, partially invaded andPsidium cattleyanum‐(strawberry guava) dominated to quantify light quality in the understorey (0–50 cm height). We also identified relationships between light quality and native and non‐native seedling presence, diversity and abundance. Together, these data can help to determine the restoration potential of HLWF.Linear mixed‐effect modelling showed that native‐dominated forests had significantly greater R:FR thanP. cattleyanum‐dominated forests, demonstrating a transformation in the light environment with increased invasion. Heterogeneity in R:FR varied more across sites than among forest types. In both native‐dominated and partially invaded forests, there were more native seedlings in the low‐quality R:FR (0.0–0.40) category and fewer in the medium‐ (0.41–0.70), and high‐quality (≥0.71) light categories than would be expected by chance, and there were no native seedlings in theP. cattleyanum‐dominated forests.Native‐dominated forests had greater species richness and abundance of native seedlings than the partially invaded forests, likely due to propagule availability. However, the spatial clustering of seedlings, the mismatch of native seedlings in light environments less suitable, and a considerable proportion of open high‐quality microsites, highlights that conditions are not optimal for native species in HLWF in the long term.Synthesis and applications.The native‐dominated and partially invaded forests still hold conservation value, despite variation among sites. Seedling additions could be targeted to different R:FR environments and at different spatial scales, but the lack of a strong relationship between R:FR and seedling number suggests that other factors besides light quality should be considered in seedling enrichment or other management activities. 

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3. Light availability and rhizobium variation interactively mediate the outcomes of legume–rhizobium symbiosis

   https://doi.org/10.1002/ajb2.1435  

   Heath, Katy_D; Podowski, Justin_C; Heniff, Stephanie; Klinger, Christie_R; Burke, Patricia_V; Weese, Dylan_J; Yang, Wendy_H; Lau, Jennifer_A (February 2020, American Journal of Botany)

   PremiseNutrients, light, water, and temperature are key factors limiting the growth of individual plants in nature. Mutualistic interactions between plants and microbes often mediate resource limitation for both partners. In the mutualism between legumes and rhizobia, plants provide rhizobia with carbon in exchange for fixed nitrogen. Because partner quality in mutualisms is genotype‐dependent, within‐species genetic variation is expected to alter the responses of mutualists to changes in the resource environment. Here we ask whether partner quality variation in rhizobia mediates the response of host plants to changing light availability, and conversely, whether light alters the expression of partner quality variation. MethodsWe inoculated clover hosts with 11 strains ofRhizobium leguminosarumthat differed in partner quality, grew plants under either ambient or low light conditions in the greenhouse, and measured plant growth, nodule traits, and foliar nutrient composition. ResultsLight availability and rhizobium inoculum interactively determined plant growth, and variation in rhizobium partner quality was more apparent in ambient light. ConclusionsOur results suggest that variation in the costs and benefits of rhizobium symbionts mediate host responses to light availability and that rhizobium strain variation might more important in higher‐light environments. Our work adds to a growing appreciation for the role of microbial intraspecific and interspecific diversity in mediating extended phenotypes in their hosts and suggests an important role for light availability in the ecology and evolution of legume–rhizobium symbiosis. 

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4. Passive atomic-scale optical sensors for mapping light flux in ultra-small cavities

   https://doi.org/10.1038/s41598-023-32010-y  

   Andričević, Pavao; Sellwood, Elaine L.; Eppes, Martha-Cary; Kook, Myungho; Jain, Mayank (December 2023, Scientific Reports)

   Abstract Understanding light propagation and attenuation in cavities is limited by lack of applicable light sensing technologies. Here we demonstrate the use of light-sensitive metastable states in wide bandgap aluminosilicates (feldspar) as passive optical sensors for high-resolution mapping of light flux. We develop non-destructive, infrared photoluminescence (IRPL) imaging of trapped electrons in cracks as thin as 50 µm width to determine the spatio-temporal evolution of light sensitive metastable states in response to light exposure. Modelling of these data yields estimates of relative light flux at different depths along the crack surfaces. Contrary to expectation, the measured light flux does not scale with the crack width, and it is independent of crack orientation suggesting the dominance of diffused light propagation within the cracks. This work paves way for understanding of how light attenuates in the minutest of cavities for applications in areas as diverse as geomorphology, biology/ecology and civil engineering. 

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5. Polymers and light: a love–hate relationship

   https://doi.org/10.1039/D5SC00997A  

   Weerasinghe, M_A_Sachini_N; Nwoko, Tochukwu; Konkolewicz, Dominik (March 2025, Chemical Science)

   The interaction of light with polymers can be positive, where light enhances polymerization or performance, but it can also be negative towards the targeted properties. Positive and negative interactions between polymers and light are highlighted. 

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