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We have studied the room-temperature non-radiative energy transfer processes in hybrid structures composed of (Ga, In)N/GaN single quantum wells and semiconducting polymer blend films placed in nanometre-scale proximity. The blends consist of three polyfluorene materials with concentrations adjusted so that they emit white light. Power-dependent photoluminescence (PL) measurements are used to investigate the process of energy transfer from the quantum wells to the different components of the polymer blend. We show that energy distribution among the hybrid structures involves competition between nanoscale range non-radiative energy transfer processes from the inorganic well to the polymer components and within the blend itself. © 2009 IOP Publishing Ltd. 20 27 Cited By :16

We report on novel InGaN/GaN quantum well/polyfluorene heterostructures where efficient Förster energy transfer from the well to the organic layer occurs. We show that Mott-Wannier excitons dominate the quantum well luminescence in the quantum wells in the 77 to at least 225 K range and are responsible for the efficient energy channeling to the polyfluorene films. © 2007 American Institute of Physics. 893 355 356 Sponsors: Austrian Research Centers (ARCS) Infineon Austrian Fed. Minist. Educ., Sci. Cult. (BMBMWK) FFG Austrian Nano Initiative Cited By :1

We present the highlights of a research programme on hybrid inorganic-organic light emitters. These devices combine recent developments in III-V nitride technology (including UV emitting micro-arrays and specifically tailored quantum wells) with conjugated polymers to access the entire visible spectrum. Two types of devices are studied, those based on down conversion of the quantum well emission by radiative transfer and those based on non-radiative resonant energy transfer. The spectral and operating characteristics of the devices are described in detail. Selectable colour micro-arrays and bar emitters are demonstrated. The nature of the non-radiative energy transfer process has also been studied and we find transfer efficiencies of up to 43% at 15 K, with a 1/R2 dependence on the distance between quantum well and polymer layer, suggesting a plane-plane interaction. The relative importance of the non-radiative resonant energy transfer process increases with temperature to be up to 20 times more efficient, at 300 K, than the radiative transfer process. © 2008 IOP Publishing Ltd. 41 9 Cited By :39

People have limited capacity to process and integrate multiple sources of information, so how do they integrate multiple contextual risk factors for Coronavirus disease (COVID-19) infection? In June 2020, we elicited risk perceptions from a nationally representative sample of the public (N = 800) using three psychologically-distinct tasks. Responses were compared to a sample of medical experts who completed the same tasks. Relative to experts, the public perceived lower risk associated with environmental factors (such as whether a gathering takes place indoors or outdoors) and were less inclined to treat risk factors as multiplicative. Our results are consistent with a heuristic simply to “avoid people” and with a coarse (e.g., “safe or unsafe”) classification of social settings. A further task, completed only by the general public sample, generated novel evidence that when infection risk competes with risk in another domain (e.g., a different medical risk), people perceive a lower likelihood of contracting the virus. These results inform the policy response to the pandemic and have implications for understanding differences between expert and lay perception of risk

Contact-tracing mobile phone apps can play a role in controlling the spread of COVID-19, but their success hinges on widespread public acceptance, uptake and use, which are difficult for public administrators to foresee. We report on a rapid behavioral pre-test of COVID Tracker, Ireland’s contact-tracing app, prior to its launch. A large sample of participants were randomized to receive different versions of a trial app. They responded to an online survey while downloading and using the app on their phones in real time. Experimental manipulations focused on: (i) the level of privacy assurance provided in the app, (ii) the goal-framing of the purpose of the app and (iii) the structuring of the exposure notification. Almost one in five participants mentioned privacy concerns in relation to their likelihood of downloading the app, but concerns were lower and engagement stronger in a condition that included additional assurances regarding the privacy of users’ data in the app. This finding informed the final version of the app. Overall, our results demonstrate the value and feasibility of pre-testing digital interfaces to improve public administration.

Objective: Self-isolation is a vital element of efforts to contain COVID-19. We set out to test whether decision aids can support self-isolation. Design: We conducted a pre-registered online experiment with a nationally representative sample (n = 500). Three stages tested: (i) whether decision trees help people to decide whether they need to self-isolate; (ii) whether an online planning tool increases people’s confidence in their ability to self-isolate; and (iii) whether infographics help people to absorb advice on managing a household in which someone must self-isolate. Main Outcome Measures: (i) Accuracy of matching symptom patterns to a response scale for the need to self-isolate; (ii) self-reported confidence in coping with self-isolation; (iii) objective tests of recall and comprehension. Results: Decision trees improved decisions about when self-isolation was necessary, although participants systematically underestimated the need to self-isolate with less common COVID-19 symptoms (e.g. sore throat, fatigue). The online planning tool increased confidence about coping with self-isolation only among the adults aged under 40. Infographics improved recall and comprehension of how to manage self-isolation. Conclusion: Decision aids can be used to support self-isolation during COVID-19. The study also demonstrates how even an emergency public health response can benefit from rapid experimental pre-testing of interventions.

Objective Accurate measurement of compliance with COVID-19 guidance is important for public health policy and communications. Responses to surveys, however, are susceptible to psychological biases, including framing effects and social desirability. Our aim was to measure the effects of these biases on estimates of compliance with public health guidance (eg, hand-washing, social distancing). Design We conducted two online experiments (n=1800) and varied whether questions were framed positively or negatively (eg, ‘I always wash my hands…’ vs ‘I don’t always wash my hands…’). We also varied the degree to which anonymity was assured, via a ‘list’ experiment. Results Reported compliance, despite being generally high, was reduced by negatively framing questions and increasing anonymity using a list experiment technique. Effect sizes were large: compliance estimates diminished by up to 17% points and 10% points, respectively. Conclusion Estimates of compliance with COVID-19 guidance vary substantially with how the question is asked. Standard tracking surveys tend to pose questions in ways that lead to higher estimates than alternative approaches. Experimental tests of these surveys offer public health officials greater insight into the range of likely compliance estimates to better inform policy and communications.

Rationale Maintaining social distance during the COVID-19 pandemic can save lives. We therefore set out to test communication strategies to promote social distancing. Objective We aimed to test two novel public health messages against a control message. The first was designed to exploit the “identifiable victim” effect by highlighting the risk of transmission to identifiable vulnerable persons. The second sought to counteract intuitive underestimation of exponential transmission. Method In total, 500 Irish adults undertook a pre-registered, online experiment. They were randomly assigned to a control group or one of two treatment groups. The control group viewed a current poster that encouraged a 2-m separation between people. The two treatment groups saw posters of similar design, but with narrative messages describing how an individual had infected a specific vulnerable person or multiple other people. Later questions measured intentions to undertake three specific types of social interaction over the coming days and the stated acceptability of three other types of social interaction. Pilot work had identified these six behaviors as “marginal” – people were unsure whether they were advisable. Results Participants in the treatment conditions were more cautious about undertaking the behaviors and less accepting of them. This positive effect occurred despite participants rating the treatment posters as likely to be less effective and memorable than the control poster. Conclusions Messages that invoke thoughts of infecting vulnerable people or large numbers of people can motivate social distancing and, hence, help to limit the spread of COVID-19. Stated public evaluations (obtained via focus groups or surveys) may underestimate the actual effectiveness of such emotional messages.

Background. PON1, an arylesterase, associated with high density lipoprotein (HDL), protects low density lipoprotein (LDL) against oxidative modification. Common polymorphisms PON1 55 (L/M) and 192 (Q/R) in the PON1 gene associate with atherosclerosis and heart disease. Because long-lived people seem protected from premature vascular death, we conducted a pooled statistical analysis to assess any association between these polymorphisms and longevity in a large combined group of Italian centenarians and octo/nonagenarians from Northern Ireland (NI). Materials and methods. Separated DNA was available from 1479 subjects from Italy and Northern Ireland (NI). In Italy 308 centenarians (males 67, females 241, mean age 100.8, SD2.1 years) and 579 young controls (males 347, females 232, mean age 40.7, SD 12.7 years) were included in the study. In NI, 296 octo/nonagenarians (males 92, females 204, mean age 89.8, SD 5.7 years) and 296 young sex-matched subjects (mean age 13.0, SD 1.4 years) had available DNA. PON1 55 (L/M) and 192 (Q/R) polymorphisms were studied using a PCR-RFLP approach. Results. There was a significant difference in PON1 192 genotypes in Italian centenarians compared to younger controls (X2=6.8, df=2, p=0.03) and a similar but non significant trend between octo/nonagenarian and young subjects in NI (X2=4.0, df=2, p=0.14). Using logistic regression analysis on the combined Italian and Irish datasets, there was a small survival advantage for centenarian and octo/nonagenarian subjects who were heterozygous for PON1 192 R allele, (OR 1.3, CI 1-1.6; p=0.04) with a stepwise increase for RR homozygous subjects (OR 1.7, CI 1.1-2.6; p=0.02), compared to QQ subjects. Comparing R and Q alleles there was a survival advantage for octo/nonagenarian/centenarian subjects who carried the R allele (OR 1.3, CI 1.1-1.5; p=0.007), but there was no sex-specific effect (p=0.77). LL, LM and MM genotypes of PON 55 polymorphisms showed similar frequencies in Italy (39.9, 47.0, 13.1%) and Ireland (39.5, 48.6, 11.9%) with no age or sex-related differences. The PON1 192R/Q and PON55L/M loci were in strong linkage disequilibrium with a Lewontin's D′ coefficient −0.928 (elderly) and −0.965 (young). There was a significant difference in haplotype frequency of these linked loci in older compared to younger subjects (Likelihood Ratio X2=9.60, df=3, p=0.02). Conclusion. These data suggest a modest association between the 192R allele and longevity in two very elderly populations in two European countries. Being homozygous for 192 RR further enhances survival advantage but this effect was not found to be sex specific. This finding is of interest because the 192R allele has previously been associated with increased risk of coronary heart disease. On the other hand, the 192R allele shows higher enzymatic activity, using paraoxon as substrate, and we postulate that its role in the metabolism of potentially toxic chemicals or other metabolic pathways may be important in survival to very old age.