Broadband enhancement of light harvesting in luminescent solar concentrator

Luminescent solar concentrator (LSC) can absorb large-area incident sunlight, then emit luminescence with high quantum efficiency, which finally be collected by a small photovoltaic (PV) system. The light-harvesting area of the PV system is much smaller than that of the LSC system, potentially improving the efficiency and reducing the cost of solar cells. Here, based on Fermi-golden rule, we present a theoretical description of the luminescent process in nanoscale LSCs where the conventional ray-optics model is no longer applicable. As an example calculated with this new model, we demonstrate that a slot waveguide consisting of a nanometer-sized low-index slot region sandwiched by two high-index regions provides a broadband enhancement of light harvesting by the luminescent centers in the slot region. This is because the slot waveguide can (1) greatly enhance the spontaneous emission due to the Purcell effect, (2) dramatically increase the effective absorption cross-section of luminescent centers, and (3) strongly improve the quantum efficiency of luminescent centers. It is found that about 80% solar photons can be ultimately converted to waveguide-coupled luminescent photons even for a low luminescent quantum efficiency of 0.5. This LSC is potential to construct a tandem structure which can absorb nearly full-spectrum solar photons, and also may be of special interest for building integrated nano-PV applications

Home hazard removal to reduce falls among community-dwelling older adults: A randomized clinical trial

Importance: Falls are the leading preventable cause of morbidity, mortality, and premature institutionalization for community-dwelling older adults. Objective: To test the effectiveness of a behavioral intervention on fall risk among older adults receiving services from an Area Agency on Aging. Design, Setting, and Participants: This randomized clinical trial examined a home hazard removal intervention in the community using a race- and sex-stratified randomization design. Older adults receiving services from the Area Agency on Aging in urban St Louis, Missouri, were assigned to a home hazard removal intervention delivered over 2 weeks with a 6-month booster or usual care control. Eligible participants were adults aged 65 years or older who did not have dementia, were at high risk for falling, and resided in the community. Enrollment occurred from January 2015 to September 2016; 12-month follow-up occurred from February 2016 to October 2017. Data were analyzed from February 2019 to July 2021. Interventions: The intervention was a home hazard removal program delivered by an occupational therapist in the home that included a comprehensive clinical assessment and a tailored hazard removal plan. Usual care control consisted of annual assessments and community referral. Main Outcomes and Measures: The primary outcome was the hazard of a fall over 12 months. Prespecified secondary outcomes included the rate of falls over 12 months, daily activity performance, falls self-efficacy, and self-reported quality of life. Results: A total of 310 participants (mean [SD] age, 75 [7.4] years; 229 [74%] women; 161 Black participants [52%]) were randomized, with 155 participants assigned to the intervention and 155 participants assigned to usual care. Retention was 127 participants (82%) in the intervention group and 126 participants (81%) in the control group. There was no difference for our primary outcome of fall hazard (hazard ratio, 0.90; 95% CI, 0.66-1.27). There was a 38% reduction in the rate of falling in the intervention group compared with the control group (relative risk, 0.62; 95% CI, 0.40-0.95; P = .03). At 12 months, the rate of falls per person-year was 1.5 (95% CI, 1.32-1.75) in the intervention group and 2.3 (95% CI, 2.08-2.60) in the control group. There was no difference in daily activity performance (adjusted difference, -0.20; 95% CI, -0.95 to 0.55; P = .60), falls self-efficacy (adjusted difference, -0.12; 95% CI, -1.25 to 1.01; P = .84), or quality of life (adjusted difference, 0.84; 95% CI, -0.95 to 2.64; P = .35). Conclusions and Relevance: This randomized clinical trial found that a brief home hazard removal program did not reduce the hazard of falls among community-dwelling older adults at high risk for falling. The intervention was effective in achieving a reduced rate of falls, a prespecified secondary outcome. This effectiveness study has the potential for delivery through the national aging services network. Trial Registration: ClinicalTrials.gov Identifier: NCT02392013

Bin ratio-based histogram distances and their application to image classification

Large variations in image background may cause partial matching and normalization problems for histogram-based representations, i.e., the histograms of the same category may have bins which are significantly different, and normalization may produce large changes in the differences between corresponding bins. In this paper, we deal with this problem by using the ratios between bin values of histograms, rather than bin values' differences which are used in the traditional histogram distances. We propose a bin ratio-based histogram distance (BRD), which is an intra-cross-bin distance, in contrast with previous bin-to-bin distances and cross-bin distances. The BRD is robust to partial matching and histogram normalization, and captures correlations between bins with only a linear computational complexity. We combine the BRD with the ℓ1 histogram distance and the χ2 histogram distance to generate the ℓ1 BRD and the χ2 BRD, respectively. These combinations exploit and benefit from the robustness of the BRD under partial matching and the robustness of the ℓ1 and χ2 distances to small noise. We propose a method for assessing the robustness of histogram distances to partial matching. The BRDs and logistic regression-based histogram fusion are applied to image classification. The experimental results on synthetic data sets show the robustness of the BRDs to partial matching, and the experiments on seven benchmark data sets demonstrate promising results of the BRDs for image classification

(E)-1-(4-Methyl­phen­yl)-3-[(1-phenyl­ethyl­idene)amino]­thio­urea

In the title compound, C16H17N3S, the amino­thio­urea unit is nearly planar (r.m.s. deviation = 0.0425 Å), and is twisted with respect to the tolyl and phenyl rings by 57.84 (7) and 15.88 (14)°, respectively; the tolyl and phenyl rings are twisted by 65.64 (11)° to each other. Inter­molecular N—H⋯S and weak C—H⋯S hydrogen bonds are present in the crystal structure

The landscape–atmosphere continuum determines ecological change in alpine lakes of SE Tibet

© 2017 Springer Science+Business Media, LLC Remote alpine regions were considered to be largely unimpacted by anthropogenic disturbance, but it is now clear these areas are changing rapidly. It is often difficult to identify the causal processes underpinning ecological change because the main drivers (direct and indirect climate forcing, land use change and atmospheric deposition) are acting simultaneously. In addition, alpine landscapes are morphometrically complex with strong local environmental gradients creating natural heterogeneity which acts as a variable filter to climate and anthropogenic forcing, emphasizing the need for analyzing responses at multiple sites. The eastern margin of Tibet is a hotspot of global biodiversity and is affected by both atmospheric N and dust deposition, whereas regional climate warming is comparatively recent. Here we use 210 Pb and 137 Cs dated sediment records from nine alpine lakes, and statistical measures of diatom ecological change (turnover and PCA axis 1 scores) to determine regional scale patterns in community response to global environmental change forcing over approximately the last 150 years. The study lakes showed contrasting ecological responses with increased nutrient input as the primary driver of change, mediated by lake morphology and catchment characteristics. Turnover rates of diatom composition, although low, are significantly associated with lake volume, lake area, altitude and DOC

A Novel Inward Gradient Self-Lubrication Layer with Soft Alloys and Its Lubricating Mechanism

A novel ceramic composite inward gradient distribution layer has been developed. The layer is a lubricating layer in which soft-metal lubricants are compounded into the ceramic matrix by high frequency induction infiltrating method. The design of the layer and its lubricating mechanism are investigated in the paper. The results show that the property of the layer greatly depends on the wetting angle of the soft-metal lubricants on the matrix and the proportion of Ag, Cu, Sn, and Pb as well as the infiltrating parameters. Based on a lot of experiments, a novel inward gradient layer with Pb28Sn19Ag6Cu has been developed. The layer has an excellent lubricating property (friction coefficient about 0.2~0.3 at 600°C). The research reveals the lubricating mechanism, observing the phenomenon that the soft-metal in the matrix diffuses out of the frictional surface, and measures the lubricating film thickness as about 20 μm on the worn surface