Efficiency of Lift Production in Flapping and Gliding Flight of Swifts

Many flying animals use both flapping and gliding flight as part of their routine behaviour. These two kinematic patterns impose conflicting requirements on wing design for aerodynamic efficiency and, in the absence of extreme morphing, wings cannot be optimised for both flight modes. In gliding flight, the wing experiences uniform incident flow and the optimal shape is a high aspect ratio wing with an elliptical planform. In flapping flight, on the other hand, the wing tip travels faster than the root, creating a spanwise velocity gradient. To compensate, the optimal wing shape should taper towards the tip (reducing the local chord) and/or twist from root to tip (reducing local angle of attack). We hypothesised that, if a bird is limited in its ability to morph its wings and adapt its wing shape to suit both flight modes, then a preference towards flapping flight optimization will be expected since this is the most energetically demanding flight mode. We tested this by studying a well-known flap-gliding species, the common swift, by measuring the wakes generated by two birds, one in gliding and one in flapping flight in a wind tunnel. We calculated span efficiency, the efficiency of lift production, and found that the flapping swift had consistently higher span efficiency than the gliding swift. This supports our hypothesis and suggests that even though swifts have been shown previously to increase their lift-to-drag ratio substantially when gliding, the wing morphology is tuned to be more aerodynamically efficient in generating lift during flapping. Since body drag can be assumed to be similar for both flapping and gliding, it follows that the higher total drag in flapping flight compared with gliding flight is primarily a consequence of an increase in wing profile drag due to the flapping motion, exceeding the reduction in induced drag

Welkom in Rotterdam! : een studie naar interculturele ontmoetingen tussen 'oude' en 'nieuwe' Rotterdammers

Maatschappelijke solidariteit tussen verschillende bevolkingsgroepen bestaat nog wel degelijk in de huidige multiculturele samenleving van Rotterdam. Dat concluderen onderzoekers in een studie van de Wetenschapswinkel van Wageningen UR (University & Research centre) naar de effecten van de interculturele ontmoetingen die het project 'Welkom in Rotterdam' organiseert. Zowel ‘oude’ als ‘nieuwe’ Rotterdammers staan open voor contact met elkaar, maar de drempel voor spontane contacten is voor veel mensen te hoog. Hun sociale netwerken zijn gescheiden waardoor de gelegenheid vaak ontbreekt

Discrepancies in dyadic coping: associations with distress and quality of life in couples facing early stage dementia

OBJECTIVES: Due to an aging population, the number of persons living with dementia (PWDs) is increasing worldwide. Romantic partners, as informal caregivers (IC) of PWDs, are often adopting additional tasks. The concept of dyadic coping (DC) addresses how couples cope with stress together. For dyadic coping to be successful, efforts of both partners should be equal. The current study examines how discrepancies in PWDs and ICs perspectives on DC relate to distress and quality of life in each partner within couples facing early stage dementia (ESD). METHODS: A total of 37 mixed-sex couples including one partner with ESD completed self-report questionnaires. Discrepancies in reciprocity (comparing provided or received levels of DC between partners), equity (each partner balancing own levels received and provided), and congruence (the agreement about levels of DC exchanged between partners) and their covariation with distress and quality of life (QoL) of each partner were measured. RESULTS: Both partners indicated a discrepancy in reciprocity: PWDs reported receiving more DC than ICs reported receiving, which was associated with higher QoL in PWDs and lower QoL in ICs. Inequities were found in ICs only, who reported receiving less DC, than providing. No relation between inequities and distress or QoL was found. ICs reported more incongruencies than PWDs did, which was associated with higher QoL and less depression in partners. DISCUSSION: A redivision of tasks and roles in the early stage of dementia is associated with different experiences and views between partners. Whereas ICs take over most household and care tasks within the couple, their effort was considered less helpful by PWDs than by ICs. A high care burden is associated with a compromised quality of ICs' social life and living conditions. The clinical implications of the results are discussed