Enhanced coupling of broadband light into amorphous silicon via periodic nanoplasmonic arrays.

Achieving enhanced coupling of solar radiation over the full range of the silicon absorption spectrum up to the bandgap is essential for increased efficiency of solar cells, especially thin film versions. While many designs for enhancing trapping of radiation have been explored, detailed measurements of light scattering inside silicon cells is still lacking. Here, we demonstrate experimentally and computationally that plasmonic-assisted localized and traveling modes can efficiently couple red and infrared radiation into ultrathin amorphous silicon (a-Si) layers. Utilizing patterned periodic arrays of aluminum nanostructures on thin a-Si, we perform specular and diffuse reflectivity and transmission measurements over a broad spectrum. Based on these results, we are able to separate parasitic absorption in aluminum plasmonic arrays from enhanced light absorption in the 200 nm thick amorphous silicon layer, as compared to a blank silicon layer. We discover a very efficient near-infrared a-Si absorption mechanism that occurs at the transition from the radiative to evanescent diffractive coupling, analogous to earlier surface-enhanced infrared studies. These results represent a direct demonstration of enhanced radiation coupling into silicon due to large angle scattering and show a path forward to improved ultrathin solar cell efficiency.

Factors related to the length of in-hospital stay of geriatric patients.

The aim of this study was to evaluate factors predicting length of stay in hospital of geriatric patients. Study participants were 402 patients (183 males and 219 females) consecutively admitted to four geriatric wards located in Chieti, Perugia, Pescara and Prato, Italy. Information on potential predictors of length of stay was collected; in particular, we assessed the presence and severity of specific chronic medical conditions, level of physical function, cognitive status, and depressive symptoms. Moreover, information on family and social support was obtained. In general, participants were old, often cognitively impaired and physically disabled. Average length of stay ranged from 9.4 +/- 3.3 days (Perugia) to 14.1 +/- 7.2 days (Chieti), and was statistically different across centers (p < 0.001). None of the specific medical diagnoses was associated with different length of stay. However, higher comorbidity score (p < 0.001), living alone (p < 0.01), lower MMSE score (p = 0.03), and poor functional status (p = 0.05) were all associated with longer length of stay. When these variables were included in a multivariate model predicting length of stay, differences between centers were no longer statistically significant. Findings of this study show that specific medical diagnoses are not adequate instruments to estimate length of stay in geriatric units. Other assessment systems based on extension of the social network, comorbidity, and the cognitive as well as the functional level need to be developed.

Constant hierarchic patterns of physical functioning across seven populations in five countries.

This research was aimed at identifying critical steps in the decline in physical function that often parallels aging. Six basic and nine instrumental activities of daily living (ADLs) were classified into four domains of disability characterized by specific underlying physical impairment. The hierarchical order of this classification was verified in two random samples representative of the older home-dwelling population. The concordance level of disability and results of performance-based measures of physical function were also tested. Finally, the cross-cultural reliability of the model was verified in seven population-based samples of older persons living in five European countries. In older persons the disabling process follows a general pattern of progression based on a typical sequence of impairments.