Synopsis The mechanisms associated with the ability of owls to fly silently have been the subject of scientific interest for many decades and may be relevant to bio-inspired design to reduce noise of flapping and non-flapping flying devices. Here, we characterize the near wake dynamics and the associated flow structures produced during flight of the Australian boobook owl (Ninox boobook). Three individual owls were flown at 8 ms−1 in a climatic avian wind tunnel. The velocity field in the wake was sampled at 500 Hz using long-duration high-speed particle image velocimetry (PIV) while the wing kinematics were imaged simultaneously using high speed video. The time series of velocity maps that were acquired over several consecutive wingbeat cycles enabled us to characterize the wake patterns and to associate them with the phases of the wingbeat cycle. We found that the owl wake was dramatically different from other birds measured under the same flow conditions (i.e., western sandpiper, Calidris mauri and European starling, Sturnus vulgaris). The near wake of the owl did not exhibit any apparent shedding of organized vortices. Instead, a more chaotic wake pattern was observed, in which the characteristic scales of vorticity (associated with turbulence) are substantially smaller in comparison to other birds. Estimating the pressure field developed in the wake shows that owls reduce the pressure Hessian (i.e., the pressure distribution) to approximately zero. We hypothesize that owls manipulate the near wake to suppress the aeroacoustic signal by controlling the size of vortices generated in the wake, which are associated with noise reduction through suppression of the pressure field. Understanding how specialized feather structures, wing morphology, or flight kinematics of owls contribute to this effect remains a challenge for additional study.
OpinionZambia Since 1960 JONATHAN LAWLEY I was deeply influenced by my life as a child of the Raj. We left India when I was 10. Then came school in Southern Rhodesia and South Africa. I joined the Colonial Service because I believed in an historic British role to move southern Africa away from suicidal white racism and the routine humiliation of black people.As a cadet in Northern Rhodesia in 1960, the country came right up to expectations. Interracial relationships were totally different. I had my very first real conversations with black men. The Kalomo district had a population of 45,000 in seven chiefs' areas. There were three British administrators, the District Commissioner (DC), a District Officer (DO) and myself. It was an incredibly peaceful and law-abiding environment. The Northern Rhodesian Police (NRP) did not operate in the rural areas. Law and order was maintained by the Chief's Kapasus except in the case of murder. Most importantly, the relationship between civil servants and the people was one of mutual respect. We administrators spent about a third of our time in close contact with them on villageto-village tours. We travelled on bicycles or on foot, camping near a village in a tent under the trees with the Union Jack fluttering from a freshly cut pole. Communications with the villagers in the presence of chiefs and headmen were in the local language. Learning it quickly was my first priority.Crucial to our relationship with the local people were the disciplined district messengers. They were hand-picked local men who wore a smart red and blue uniform. They represented our viewpoint to the local people and theirs to us. They were held in high esteem by everyone. They formed a service unique to Northern Rhodesia and were a vital element in the excellent relations we had with the rural population. Several were old enough to be my father and I came to rely utterly on their local knowledge, wisdom and loyalty. Beyond extending contact and understanding, our work in the rural area included development in all its aspects. This included training the Native Authority and encouraging good practice, particularly in education as well as matters as diverse as health and hygiene and road building. Persuading conservative rural people to abandon unproductive and sometimes damaging agricultural practices was a constant challenge. There was progress, however, through training and incentives for 'improved farmers'.At district headquarters, or the boma as it was known, we had a staff of African clerks and executive assistants who played a vital role in keeping the wheels of the
Objective:The objective of this study was to evaluate the hemodynamic and laboratory data during the post-cardiopulmonary bypass (CPB) phase in vivo in cardiovascular surgery utilizing the VentriFlo True Pulse Pump, a novel pulsatile extracorporeal blood pump capable of generating a natural-like pulse through standard oxygenators, cannulas, and tubing sets. Methods: The surgical procedure in porcine animal model (n=2, weight 26 and 23 kg) consisted of full median sternotomy access, central aortic cannulation, transatrial venous cannula insertion under general anesthesia. The intended duration of 3 hours has been maintained. In one case, a roller pump (RP) has been instituted. Second case has received the VentriFlo pulsatile pump (VentriFlo Inc., Pelham, NH). Hemodynamics were recorded during the CPB support period and for 3 hours post-CPB, and blood sampling was performed every hour. Results: The aortic pulse pressure was consistently higher with the VentriFlo pump compared to the RP (47 mm Hg vs. 25 mm Hg) (Figure 1). Although the pump flow during CPB was comparable (Both approximately 1.3 L/min), cardiac output was higher in the VentriFlo pig during the post-CPB period (1-3 hours) compared to the RP pig (2.2 L/min vs. 1.1 L/min). Regarding blood tests, the RP group exhibited a higher white blood cell count (21,800/uL vs. 13,150/uL in the VentriFlo pig). Conclusion:The VentriFlo pulsatile pump demonstrated the capability to deliver and maintain normal pulsatile flow and optimal cardiac output during and after CPB. More studies will be necessary to elucidate longer duration postoperative outcomes in cardiovascular surgical setup.
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