Deterministic Josephson Vortex Ratchet with a load

We investigate experimentally a deterministic underdamped Josephson vortex ratchet -- a fluxon-particle moving along a Josephson junction in an asymmetric periodic potential. By applying a sinusoidal driving current one can compel the vortex to move in a certain direction, producing average dc voltage across the junction. Being in such a rectification regime we also load the ratchet, i.e., apply an additional dc bias current I_dc (counterforce) which tilts the potential so that the fluxon climbs uphill due to the ratchet effect. The value of the bias current at which the fluxon stops climbing up defines the strength of the ratchet effect and is determined experimentally. This allows us to estimate the loading capability of the ratchet, the output power and efficiency. For the quasi-static regime we present a simple model which delivers simple analytic expressions for the above mentioned figures of merit.Comment: submitted to PR

Dim light, sleep tight, and wake up bright:Sleep optimization in athletes by means of light regulation

Despite an elevated recovery need, research indicates that athletes often exhibit relatively poor sleep. Timing and consolidation of sleep is driven by the circadian system, which requires periodic light–dark exposure for stable entrainment to the 24-hour day, but is often disturbed due to underexposure to light in the morning (e.g. low-level indoor lighting) and overexposure to light in the evening (e.g. environmental and screen-light). This study examined whether combining fixed sleep schedules with light regulation leads to more consolidated sleep. Morning light exposure was increased using light-emitting goggles, whereas evening light exposure was reduced using amber-lens glasses. Using a within-subject crossover design, twenty-six athletes (14 female, 12 male) were randomly assigned to start the intervention with the light-regulation-week or the no light-regulation-week. Sleep was monitored by means of sleep diaries and actigraphy. Due to low protocol adherence regarding the fixed sleep-wake schedules, two datasets were constructed; one including athletes who kept a strict sleep-wake schedule (N = 8), and one that also included athletes with a more lenient sleep-wake schedule (N = 25). In case of a lenient sleep-wake schedule, light regulation improved self-reported sleep onset latency (Δ SOL = 8 min). This effect was stronger (Δ SOL = 17 min) and complemented by enhanced subjective sleep quality in case of a strict sleep-wake schedule. None of the actigraphy-based estimates differed significantly between conditions. To conclude, light regulation may be considered a potentially effective strategy to improve subjective sleep, but less obtrusive methods should be explored to increase protocol compliance.</p

Most important barriers and facilitators of HTA usage in decision-making in Europe

This is an Accepted Manuscript of an article published by Taylor & Francis in Expert Review of Pharmacoeconomics & Outcomes Research on 05 Jan 2018, available online: https://www.tandfonline.com/doi/full/10.1080/14737167.2018.1421459.Erasmu

Sleep in elite athletes

Contains fulltext : 195566.pdf (publisher's version ) (Open Access)Radboud University, 01 oktober 2018Promotores : Kompier, M.A.J., Geurts, S.A.E. Co-promotores : Nieuwenhuys, A., Coenen, A.M.L.231 p

Exposure to bright light biases effort-based decisions

Item does not contain fulltextSecreted in the evening and the night, melatonin suppresses activity of the mesolimbic dopamine pathway, a brain pathway involved in reward processing. However, exposure to bright light diminishes - or even prevents - melatonin secretion. Thus, we hypothesized that reward processing, in the evening, is more pronounced in bright light (vs. dim light). Healthy human participants carried out three tasks that tapped into various aspects of reward processing (effort expenditure for rewards task [EEfRT]; two-armed bandit task [2ABT]; balloon analogue risk task [BART). Brightness was manipulated within-subjects (bright vs. dim light), in separate evening sessions. During the EEfRT, participants used reward-value information more strongly when they were exposed to bright light (vs. dim light). This finding supported our hypothesis. However, exposure to bright light did not significantly affect task behavior on the 2ABT and the BART. While future research is necessary (e.g., to zoom in on working mechanisms), these findings have potential implications for the design of physical work environments.11 p

Restricting short-wavelength light in the evening to improve sleep in recreational athletes: A pilot study

Contains fulltext : 203911.pdf (publisher's version ) (Open Access)Sleep is crucial for recovery and skill acquisition in athletes. Paradoxically, athletes often encounter difficulties initiating and maintaining sleep, while having sufficient sleep opportunity. Blue (short-wavelength) light as emitted by electronic screens is considered a potential sleep thief, as it suppresses habitual melatonin secretion. The current study sought to investigate whether blocking short-wavelength light in the evening can improve sleep onset latency and potentially other sleep parameters among recreational athletes. The study had a within-subject crossover design. Fifteen recreational athletes, aged between 18 and 32 years (12 females, 3 males), were randomly assigned to start the intervention period with either the light restriction condition (LR; amber-lens glasses), or the no-light restriction condition (nLR; transparent glasses). Sleep hygiene practices, actigraphy and diary-based sleep estimates were monitored during four consecutive nights within each condition. Sleep hygiene practices did not significantly differ between conditions. Results indicate that blocking short-wavelength light in the evening, as compared to habitual light exposure, significantly shortened subjective sleep onset latency (delta = 7 min), improved sleep quality (delta = 0.6; scale 1-10), and increased alertness the following morning. Actigraphy-based sleep estimates showed no significant differences between conditions. Blocking short-wavelength light in the evening by means of amber-lens glasses is a cost-efficient and promising means to improve subjective sleep estimates among recreational athletes in their habitual home environment. The relatively small effects of the current study may be strengthened by additionally increasing morning- and daytime light exposure and, potentially, by reducing the alerting effects of media use before bedtime.8 p

Ambulatory automated auditory partial sleep deprivation affects subjective sleepiness without affecting sleep macro structure

Item does not contain fulltex