Diving-flight aerodynamics of a peregrine falcon (Falco peregrinus)

This study investigates the aerodynamics of the falcon Falco peregrinus while diving. During a dive peregrines can reach velocities of more than 320 km h⁻¹. Unfortunately, in freely roaming falcons, these high velocities prohibit a precise determination of flight parameters such as velocity and acceleration as well as body shape and wing contour. Therefore, individual F. peregrinus were trained to dive in front of a vertical dam with a height of 60 m. The presence of a well-defined background allowed us to reconstruct the flight path and the body shape of the falcon during certain flight phases. Flight trajectories were obtained with a stereo high-speed camera system. In addition, body images of the falcon were taken from two perspectives with a high-resolution digital camera. The dam allowed us to match the high-resolution images obtained from the digital camera with the corresponding images taken with the high-speed cameras. Using these data we built a life-size model of F. peregrinus and used it to measure the drag and lift forces in a wind-tunnel. We compared these forces acting on the model with the data obtained from the 3-D flight path trajectory of the diving F. peregrinus. Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow. High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred

Vortices enable the complex aerobatics of peregrine falcons

The peregrine falcon (Falco peregrinus) is known for its extremely high speeds during hunting dives or stoop. Here we demonstrate that the superior manoeuvrability of peregrine falcons during stoop is attributed to vortex-dominated flow promoted by their morphology, in the M-shape configuration adopted towards the end of dive. Both experiments and simulations on life-size models, derived from field observations, revealed the presence of vortices emanating from the frontal and dorsal region due to a strong spanwise flow promoted by the forward sweep of the radiale. These vortices enhance mixing for flow reattachment towards the tail. The stronger wing and tail vortices provide extra aerodynamic forces through vortex-induced lift for pitch and roll control. A vortex pair with a sense of rotation opposite to that from conventional planar wings interacts with the main wings vortex to reduce induced drag, which would otherwise decelerate the bird significantly during pull-out. These findings could help in improving aircraft performance and wing suits for human flights

Activated plasma coagulation β-Factor XII-induced vasoconstriction in rats

By inducing BK (bradykinin)-stimulated adrenomedullary catecholamine release, bolus injection of the β-fragment of activated plasma coagulation Factor XII (β-FXIIa) transiently elevates BP (blood pressure) and HR (heart rate) of anaesthetized, vagotomized, ganglion-blocked, captopril-treated bioassay rats. We hypothesized that intravenous infusion of β-FXIIa into intact untreated rats would elicit a qualitatively similar vasoconstrictor response. BN (Brown Norway) rats received for 60 min either: (i) saline (control; n=10); (ii) β-FXIIa (85 ng/min per kg of body weight; n=9); or (iii) β-FXIIa after 2ADX (bilateral adrenalectomy; n=9). LV (left ventricular) volume and aortic BP were recorded before (30 min baseline), during (60 min) and after (30 min recovery) the infusion. TPR (total peripheral resistance) was derived from MAP (mean arterial pressure), SV (stroke volume) and HR. Saline had no haemodynamic effects. β-FXIIa infusion increased its plasma concentration 3-fold in both groups. In adrenally intact rats, β-FXIIa infusion increased MAP by 6% (5±2 mmHg) and TPR by 45% (0.50±0.12 mmHg/ml per min), despite falls in SV (−38±8 μl) and HR [−18±5 b.p.m. (beats/min)] (all P<0.05). In 2ADX rats, β-FXIIa had no HR effect, but decreased SV (−89±9 μl) and MAP (−4±1 mmHg), and increased TPR by 66% (0.59±0.15 mmHg/ml per min) (all P<0.05). After infusion, adrenally intact rats exhibited persistent vasoconstriction (MAP, 10±1 mmHg; TPR, 0.55±0.07 mmHg/ml per min; both P<0.05), whereas in 2ADX rats, MAP remained 5±1 mmHg below baseline (P<0.05) and TPR returned to baseline. End-study arterial adrenaline (epinephrine) concentrations in the three groups were 1.9±0.6, 9.8±4.1 and 0.6±0.2 nmol/l respectively. Thus, in neurally intact lightly anaesthetized untreated rats, β-FXIIa infusion induces both adrenal catecholamine-mediated and adrenally independent increases in peripheral resistance

Investigating the links between the subcomponents of executive function and academic achievement: A cross-cultural analysis of Chinese and American preschoolers

Little is known about how components of executive function (EF) jointly and uniquely predict different aspects of academic achievement and how this may vary across cultural contexts. In the current study, 119 Chinese and 139 American preschoolers were tested on a battery of EF tasks (i.e., inhibition, working memory, and attentional control) as well as academic achievement tasks (i.e., reading and mathematics). Results demonstrate that although working memory performance in both cultures was comparable, Chinese children outperformed American children on inhibition and attentional control tasks. In addition, the relation between components of EF and achievement was similar in the two countries. Working memory uniquely predicted academic achievement, with some intriguing patterns in regard to tasks requiring complex processing. Inhibition uniquely predicted counting but did not uniquely predict calculation. Attentional control predicted most aspects of achievement uniformly and was the most robust predictor for reading in both countries. In sum, the data provide insight into both cultural variability and consistency in the development of EF during early childhood. (C) 2010 Elsevier Inc. All rights reserved

Investigating the links between the subcomponents of executive function and academic achievement: A cross-cultural analysis of Chinese and American preschoolers

Little is known about how components of executive function (EF) jointly and uniquely predict different aspects of academic achievement and how this may vary across cultural contexts. In the current study, 119 Chinese and 139 American preschoolers were tested on a battery of EF tasks (i.e., inhibition, working memory, and attentional control) as well as academic achievement tasks (i.e., reading and mathematics). Results demonstrate that although working memory performance in both cultures was comparable, Chinese children outperformed American children on inhibition and attentional control tasks. In addition, the relation between components of EF and achievement was similar in the two countries. Working memory uniquely predicted academic achievement, with some intriguing patterns in regard to tasks requiring complex processing. Inhibition uniquely predicted counting but did not uniquely predict calculation. Attentional control predicted most aspects of achievement uniformly and was the most robust predictor for reading in both countries. In sum, the data provide insight into both cultural variability and consistency in the development of EF during early childhood. (C) 2010 Elsevier Inc. All rights reserved