Polarization-independent filters for luminescent solar concentrators

The efficiency of luminescent solar concentrators could be enhanced by use of wavelength-selective filters, reducing the amount of luminescent light lost. To accomplish this, polarization-independent filters with reflectivity >97% were made by combining layers of cholesteric liquid crystals, either a right- with a left-handed layer, or two right-handed layers with a half-lambda waveplate. Normal cholesteric filters have a reflection bandwidth which is narrower than the spectral and angular range of the luminescent emission. The reflection band is broadened from 80 to 200 nm by employing a pitch gradient in the cholesteric layer. The measured transmission bands compare well with calculations

Does physical activity change predict functional recovery in low back pain? Protocol for a prospective cohort study

Background: Activity advice and prescription are commonly used in the management of low back pain (LBP). Although there is evidence for advising patients with LBP to remain active, facilitating both recovery and return to work, to date no research has assessed whether objective measurements of free living physical activity (PA) can predict outcome, recovery and course of LBP. Methods: An observational longitudinal study will investigate PA levels in a cohort of community-dwelling working age adults with acute and sub-acute LBP. Each participant's PA level, functional status, mood, fear avoidance behaviours, and levels of pain, psychological distress and occupational activity will be measured on three occasions during for 1 week periods at baseline, 3 months, and 1 year. Physical activity levels will be measured by self report, RT3 triaxial accelerometer, and activity recall questionnaires. The primary outcome measure of functional recovery will be the Roland Morris Disability Questionnaire (RMDQ). Free living PA levels and changes in functional status will be quantified in order to look at predictive relationships between levels and changes in free living PA and functional recovery in a LBP population. Discussion: This research will investigate levels and changes in activity levels of an acute LBP cohort and the predictive relationship to LBP recovery. The results will assess whether occupational, psychological and behavioural factors affect the relationship between free living PA and LBP recovery. Results from this research will help to determine the strength of evidence supporting international guidelines that recommend restoration of normal activity in managing LBP. Trial registration. [Clinical Trial Registration Number, ACTRN12609000282280]. © 2009 Hendrick et al; licensee BioMed Central Ltd

Anisotropic light emissions in luminescent solar concentrators-isotropic systems

In this paper we develop a model to describe the emission profile from randomly oriented dichroic dye molecules in a luminescent solar concentrator (LSC) waveguide as a function of incoming light direction. The resulting emission is non-isotropic, in contradiction to what is used in almost all previous simulations on the performance of LSCs, and helps explain the large surface losses measured in these devices. To achieve more precise LSC performance simulations we suggest that the dichroic nature of the dyes must be included in the future modeling efforts. © 2013 Optical Society of America.M.D. would like to acknowledge the support of STW Vidi grant 7940 and C.S.S. thanks the Spanish MINECO project MAT2011-27978-C02-02, CSIC project i-LINK0394, Gobierno de Aragón, and FEDER (EU).Peer Reviewe

A promising fluorescent dye for solar energy conversion based on a perylene perinone

We describe the synthesis of a dye based on a perylene perinone and evaluate its potential as the functional material for use in the luminescent solar concentrator (LSC). The dye extends the absorption wavelength of LSCs using the perylene-based dye Lumogen Red 305 by more than ~50nm, translating into the collection of potentially 25% more photons at a reasonable fluorescent quantum yield and photostability. When the new perinone is used in a two-waveguide LSC in conjunction with Red 305, the integrated edge emission of the total LSC system may be increased more than 24% when compared to the Red 305 dye alone

Thermoresponsive scattering coating for smart white LEDs

White light emitting diode (LED) systems, capable of lowering the color temperature of emitted light on dimming, have been reported in the literature. These systems all use multiple color LEDs and complex control circuitry. Here we present a novel responsive lighting system based on a single white light emitting LED and a thermoresponsive scattering coating. The coated LED automatically emits light of lower correlated color temperature (CCT) when the power is reduced. We also present results on the use of multiple phosphors in the white light LED allowing for the emission of warm white light in the range between 2900 K and 4150 K, and with a chromaticity complying with the ANSI standards (C78.377). This responsive warm white light LED-system with close-to-ideal emission characteristics is highly interesting for the lighting industry

Does a patient’s physical activity predict recovery from an episode of acute low back pain?: a prospective cohort study

Background Advice to remain active and normalisation of activity are commonly prescribed in the management of low back pain (LBP). However, no research has assessed whether objective measurements of physical activity predict outcome and recovery in acute low back pain. Method The aims of this study were to assess the predictive relationship between activity and disability at 3 months in a sub-acute LBP population. This prospective cohort study recruited 101 consenting patients with sub-acute LBP (< 6 weeks) who completed the Roland Morris Disability Questionnaire (RMDQ), the Visual Analogue Scale, and resumption of full ‘normal’ activity question (Y/N), at baseline and 3 months. Physical activity was measured for 7 days at both baseline and at 3 months with an RT3 accelerometer and a recall questionnaire. Results Observed and self-reported measures of physical activity at baseline and change in activity from baseline to 3 months were not independent predictors of RMDQ (p > 0.05) or RMDQ change (p > 0.05) over 3 months. A self-report of a return to full ‘normal’ activities was significantly associated with greater RMDQ change score at 3 months (p < 0.001). Paired t-tests found no significant change in activity levels measured with the RT3 (p = 0.57) or the recall questionnaire (p = 0.38) from baseline to 3 months. Conclusions These results question the predictive role of physical activity in LBP recovery, and the assumption that activity levels change as LBP symptoms resolve. The importance of a patient’s perception of activity limitation in recovery from acute LBP was also highlighted. Trial registration Clinical Trial Registration Number, ACTRN1260900028228

The relationship between physical activity and low back pain outcomes: a systematic review of observational studies

Although clinical guidelines advocate exercise and activity in the management of non-specific low back pain (NSLBP), the link between levels of physical activity and outcomes is unclear. This systematic review investigated the relationships between free living activity levels after onset of low back pain (LBP) and measures of pain, and disability in patients with NSLBP. Cohort and cross-sectional studies were located using OVID, CINAHL, Medline, AMED, Embase, Biomed, PubMed-National Library of Medicine, Proquest and Cochrane Databases, and hand searches of reference lists. Studies were included if a statistical relationship was investigated between measures of free living physical activity (PA) in subjects with LBP and LBP outcome measures. Twelve studies (seven cohort and five cross-sectional) were included. One prospective study reported a statistically significant relationship between increased leisure time activity and improved LBP outcomes, and one cross-sectional study found that lower levels of sporting activity were associated with higher levels of pain and disability. All other studies (n = 10) found no relationship between measures of activity levels and either pain or disability. Heterogeneity of study designs, particularly in terms of activity measurement, made comparisons between studies difficult. These data suggest that the activity levels of patients with NSLBP are neither associated with, nor predictive of, disability or pain levels. Validated activity measurement in prospective research is required to better evaluate the relationships between PA and LBP