Museum activities in dementia care: using visual analog scales to measure subjective wellbeing

Introduction: Previous research has shown that people with dementia and caregivers derive wellbeing-related benefits from viewing art in a group, and that facilitated museum object handling is effective in increasing subjective wellbeing for people with a range of health conditions. The present study quantitatively compared the impact of two museum-based activities and a social activity on the subjective wellbeing of people with dementia and their caregivers. Methods: A quasi-experimental crossover design was used. People with early to middle stage dementia and caregivers (N = 66) participated in museum object handling, a refreshment break and art-viewing in small groups. Visual analogue scales were used to rate subjective wellbeing pre and post each activity. Results: Mixed-design ANOVAs indicated wellbeing significantly increased during the session, irrespective of the order in which the activities were presented. Wellbeing significantly increased from object-handling and art-viewing for those with dementia and caregivers across pooled orders, but did not in the social activity of a refreshment break. An end-of-intervention questionnaire indicated that experiences of the session were positive. Conclusion: Results provide a rationale for considering museum activities as part of a broader psychosocial, relational approach to dementia care and support the use of easy to administer visual analogue scales as a quantitative outcome measure. Further partnership working is also supported between museums and healthcare professionals in the development of non-clinical, community-based programmes for this population

Klare communicatie: evaluatie interne en externe communicatie

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Inplane dispersion-relations of inas/alsb/gasb/alsb/inas interband resonant-tunneling diodes

We report on a flexible eight-band model, derived from a modified Kane base, generating a transfer-matrix formalism to calculate the transmission probability of carriers through, and the in-plane dispersion relations of, stratified media. We apply this model to study InAs/AlSb/GaSb/AlSb/InAs interband resonant-tunneling diodes. We show that the boundary-condition sets deduced from current continuity and the boundary-condition sets deduced from a Hermitian Hamiltonian defined across the interface are equal. A simplified triple-band model is found to be a good approximation to calculate the deep light-hole energy levels in a resonant interband tunneling diode. However, these simplified triple-band approximations are no longer valid when the carriers have an in-plane momentum.status: publishe

Accurate modelling of organic thin film transistors for analogue circuit simulation

Motivation: Electronics based on organic thin-film transistors (OTFTs) enables a variety of attractive applications like active matrix displays, flexible sensor systems and, at a longer timescale, printable item-level RFID tags. As analogue circuit applications of OTFTs are being extensively researched, accurate OTFT models suitable for the simulation of these circuits become increasingly more relevant and urgent. In this work we propose a physically-based, analytical model for OTFTs, which takes into account the influence of both tail and deep localized states. The model is symmetric, considers channel modulation, and provides good accuracy both in sub-threshold and above-threshold regime. It also preserves the continuity of the small-signal parameters, as it is required for analogue simulations. Model, results and discussion: Charge transport in organic semiconductors is usually explained by means of the variable range hopping (VRH) theory, i.e., thermally activated tunnelling of carriers between localized states. From a percolation model of hopping between localized states, Vissenberg and Matters [1] developed an analytic expression of field-effect mobility used to describe transport in OTFTs. Their model is based on the assumption of an exponential DOS. From the direct determination of the DOS by high lateral resolution Kelvin probe measurements [2], it was shown that the ‘’real’’ DOS is well fitted by a Gaussian function in tail states and an exponential function in deep states. Therefore the Vissenberg and Matters work is a very good approximation of the Gaussian DOS only in tail states [3] whereas it neglects deep states. Based on these experimental evidences, we consider the influence of both tail and deep states on the OTFT current. We show that the former are important at high gate voltages when the transistor works in strong accumulation regime and the latter are relevant at low VGS, both in saturation and in sub-threshold regime (see Fig. 1). Channel length modulation is also accounted for in the model, ensuring both current and output-resistance continuity at the pinch-off voltage: this is very important when the model is used in a CAD environment and for analogue design purposes. In Figs. 1, 2 the proposed model (red continuous line) is compared with experimental data: accuracy is good both below- and above- threshold. The model is fully symmetrical and can be easily extended to take into account contact resistance effects. The model parameters are extracted in a simple and direct way from the experimental measurements (without any optimization method) using the standard procedure described in [4]. From measurement in biasing conditions where the drain current is dominated by deep-states, one can determine the flat-band voltage VFB, the conductivity sd and the DOS characteristic temperature Td. It is worth noting that the flat-band condition is unambiguously determined from the deep-states current and, contrary to [5], no other threshold voltage needs to be introduced. Measurements where ID is dominated by tail-states current give st and Tt. Apart from geometric parameters, the model requires only five physical parameters related to the material properties

Accurate modelling of organic thin film transistors for analogue circuit simulation

Motivation: Electronics based on organic thin-film transistors (OTFTs) enables a variety of attractive applications like active matrix displays, flexible sensor systems and, at a longer timescale, printable item-level RFID tags. As analogue circuit applications of OTFTs are being extensively researched, accurate OTFT models suitable for the simulation of these circuits become increasingly more relevant and urgent. In this work we propose a physically-based, analytical model for OTFTs, which takes into account the influence of both tail and deep localized states. The model is symmetric, considers channel modulation, and provides good accuracy both in sub-threshold and above-threshold regime. It also preserves the continuity of the small-signal parameters, as it is required for analogue simulations. Model, results and discussion: Charge transport in organic semiconductors is usually explained by means of the variable range hopping (VRH) theory, i.e., thermally activated tunnelling of carriers between localized states. From a percolation model of hopping between localized states, Vissenberg and Matters [1] developed an analytic expression of field-effect mobility used to describe transport in OTFTs. Their model is based on the assumption of an exponential DOS. From the direct determination of the DOS by high lateral resolution Kelvin probe measurements [2], it was shown that the ‘’real’’ DOS is well fitted by a Gaussian function in tail states and an exponential function in deep states. Therefore the Vissenberg and Matters work is a very good approximation of the Gaussian DOS only in tail states [3] whereas it neglects deep states. Based on these experimental evidences, we consider the influence of both tail and deep states on the OTFT current. We show that the former are important at high gate voltages when the transistor works in strong accumulation regime and the latter are relevant at low VGS, both in saturation and in sub-threshold regime (see Fig. 1). Channel length modulation is also accounted for in the model, ensuring both current and output-resistance continuity at the pinch-off voltage: this is very important when the model is used in a CAD environment and for analogue design purposes. In Figs. 1, 2 the proposed model (red continuous line) is compared with experimental data: accuracy is good both below- and above- threshold. The model is fully symmetrical and can be easily extended to take into account contact resistance effects. The model parameters are extracted in a simple and direct way from the experimental measurements (without any optimization method) using the standard procedure described in [4]. From measurement in biasing conditions where the drain current is dominated by deep-states, one can determine the flat-band voltage VFB, the conductivity sd and the DOS characteristic temperature Td. It is worth noting that the flat-band condition is unambiguously determined from the deep-states current and, contrary to [5], no other threshold voltage needs to be introduced. Measurements where ID is dominated by tail-states current give st and Tt. Apart from geometric parameters, the model requires only five physical parameters related to the material properties

Pnp resonant tunneling light-emitting transistor

A pnp bipolar resonant tunneling transistor is realized using a base consisting of an n-type modulation doped quantum-well layer next to a double-barrier tunneling structure. Electrons are injected from the quantum-well base layer into the tunneling structure, leading to quantum-well light emission when they recombine with holes from the emitter. This optical output, which is modulated by the base voltage, persists in the negative differential resistance region of the current-voltage characteristics where the hole current is in oscillation. This opens possibilities for using this transistor as a high frequency electro-optical heterodyne convertor.status: publishe

Leisure innovation and the transition to retirement

Innovation theory posits that adopting new leisure activities contributes to well-being in later life. We explored the relevance of innovation theory among Canadian baby boomers transitioning to retirement. Using grounded theory and online qualitative methods, we recruited baby boomers who had recently retired or were planning to retire in the next five years. Twenty-five participants engaged in three two-week blogging sessions, followed by face-to-face focus groups/interview over about one year. Data, including blog posts from each session and focus group/interview transcripts, were analyzed using initial, focused, and theoretical coding. Two main themes, embracing retirement and pursuing new and former leisure, highlighted nuances of leisure and the transition to retirement as participants adjusted to increased free time along with shifting priorities and available resources. The findings supported innovation theory and suggested areas of refinement

An 8b organic microprocessor on plastic foil

We introduce a microprocessor made by organic thin-film transistors processed directly onto flexible plastic foil. This is a direct realization of a microprocessor by thin-film technology, i.e., without transfer, on plastic. It paves the way to equip mundane supports and objects with low-cost computing power. We also demonstrate the correct execution of a digital signal-processing task, namely increasing the accuracy of a repetitive digital input by time-averaging. © 2011 IEEE