Correction to 'On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number'.

[This corrects the article DOI: 10.1098/rsfs.2016.

On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number.

The flight of many birds and bats, and their robotic counterparts, occurs over a range of chord-based Reynolds numbers from 1 × 10 to 1.5 × 10. It is precisely over this range where the aerodynamics of simple, rigid, fixed wings becomes extraordinarily sensitive to small changes in geometry and the environment, with two sets of consequences.

Not very NICE: deviance, stigma and nutritional guidelines related to healthy weight and obesity.

This paper critically examines the current National Institute for Health and Clinical Excellence and National Health Service guidelines on weight management and the avoidance of obesity (NG7). We demonstrate that the guidance is unlikely to produce the desired effect of enabling people to reduce or control their weight through the twin strategies of dieting (primarily using the calories-in, calories-out approach) and increasing their levels of exercise. The paper provides a critical examination of these guidelines and concludes that they are unlikely to encourage maintenance of 'healthy' weights or prevent obesity, are not based upon particularly strong evidence and are misguided in maintaining a persistent focus upon weight rather than other indicators of health.

Bird or bat: comparing airframe design and flight performance.

Birds and bats have evolved powered flight independently, which makes a comparison of evolutionary 'design' solutions potentially interesting. In this paper we highlight similarities and differences with respect to flight characteristics, including morphology, flight kinematics, aerodynamics, energetics and flight performance. Birds' size range is 0.

The near and far wake of Pallas' long tongued bat (Glossophaga soricina).

The wake structures of a bat in flight have a number of characteristics not associated with any of the bird species studied to this point. Unique features include discrete vortex rings generating negative lift at the end of the upstroke at medium and high speeds, each wing generating its own vortex loop, and a systematic variation in the circulation of the start and stop vortices along the wingspan, with increasing strength towards the wing tips. Here we analyse in further detail some previously published data from quantitative measurements of the wake behind a small bat species flying at speeds ranging from 1.

Beyond robins: aerodynamic analyses of animal flight.

Recent progress in studies of animal flight mechanics is reviewed. A range of birds, and now bats, has been studied in wind tunnel facilities, revealing an array of wake patterns caused by the beating wings and also by the drag on the body. Nevertheless, the quantitative analysis of these complex wake structures shows a degree of similarity among all the different wake patterns and a close agreement with standard quasi-steady aerodynamic models and predictions.

Leading-edge vortex improves lift in slow-flying bats.

Staying aloft when hovering and flying slowly is demanding. According to quasi-steady-state aerodynamic theory, slow-flying vertebrates should not be able to generate enough lift to remain aloft. Therefore, unsteady aerodynamic mechanisms to enhance lift production have been proposed.

Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel.

In this paper we describe the flight characteristics of a swift (Apus apus) in cruising flight at three different flight speeds (8.0, 8.4 and 9.

The implications of low-speed fixed-wing aerofoil measurements on the analysis and performance of flapping bird wings.

Bird flight occurs over a range of Reynolds numbers (Re; 10(4) < or = Re < or = 10(5), where Re is a measure of the relative importance of inertia and viscosity) that includes regimes where standard aerofoil performance is difficult to predict, compute or measure, with large performance jumps in response to small changes in geometry or environmental conditions. A comparison of measurements of fixed wing performance as a function of Re, combined with quantitative flow visualisation techniques, shows that, surprisingly, wakes of flapping bird wings at moderate flight speeds admit to certain simplifications where their basic properties can be understood through quasi-steady analysis. Indeed, a commonly cited measure of the relative flapping frequency, or wake unsteadiness, the Strouhal number, is seen to be approximately constant in accordance with a simple requirement for maintaining a moderate local angle of attack on the wing.

Bat flight generates complex aerodynamic tracks.

The flapping flight of animals generates an aerodynamic footprint as a time-varying vortex wake in which the rate of momentum change represents the aerodynamic force. We showed that the wakes of a small bat species differ from those of birds in some important respects. In our bats, each wing generated its own vortex loop.

Wake structure and wingbeat kinematics of a house-martin Delichon urbica.

The wingbeat kinematics and wake structure of a trained house martin in free, steady flight in a wind tunnel have been studied over a range of flight speeds, and compared and contrasted with similar measurements for a thrush nightingale and a pair of robins. The house martin has a higher aspect ratio (more slender) wing, and is a more obviously agile and aerobatic flyer, catching insects on the wing. The wingbeat is notable for the presence at higher flight speeds of a characteristic pause in the upstroke.

Vortex wakes generated by robins Erithacus rubecula during free flight in a wind tunnel.

The wakes of two individual robins were measured in digital particle image velocimetry (DPIV) experiments conducted in the Lund wind tunnel. Wake measurements were compared with each other, and with previous studies in the same facility. There was no significant individual variation in any of the measured quantities.

The relationship between wingbeat kinematics and vortex wake of a thrush nightingale.

The wingbeat kinematics of a thrush nightingale Luscinia luscinia were measured for steady flight in a wind tunnel over a range of flight speeds (5-10 m s(-1)), and the results are interpreted and discussed in the context of a detailed, previously published, wake analysis of the same bird. Neither the wingbeat frequency nor wingbeat amplitude change significantly over the investigated speed range and consequently dimensionless measures that compare timescales of flapping vs. timescales due to the mean flow vary in direct proportion to the mean flow itself, with no constant or slowly varying intervals.

Comparing fluid mechanics models with experimental data.

The art of modelling the physical world lies in the appropriate simplification and abstraction of the complete problem. In fluid mechanics, the Navier-Stokes equations provide a model that is valid under most circumstances germane to animal locomotion, but the complexity of solutions provides strong incentive for the development of further, more simplified practical models. When the flow organizes itself so that all shearing motions are collected into localized patches, then various mathematical vortex models have been very successful in predicting and furthering the physical understanding of many flows, particularly in aerodynamics.

A family of vortex wakes generated by a thrush nightingale in free flight in a wind tunnel over its entire natural range of flight speeds.

In view of the complexity of the wing-beat kinematics and geometry, an important class of theoretical models for analysis and prediction of bird flight performance entirely, or almost entirely, ignores the action of the wing itself and considers only the resulting motions in the air behind the bird. These motions can also be complicated, but some success has previously been recorded in detecting and measuring relatively simple wake structures that can sometimes account for required quantities used to estimate aerodynamic power consumption. To date, all bird wakes, measured or presumed, seem to fall into one of two classes: the closed-loop, discrete vortex model at low flight speeds, and the constant-circulation, continuous vortex model at moderate to high speeds.

Uncertainty calculations for theoretical flight power curves.

The comparison of theoretical and experimental estimates of the mechanical power requirement for flight is currently impossible owing to the absence of complete experimental data based on mechanical power, as opposed to measurements of metabolic rates. Nevertheless, comparisons of measured and predicted characteristic speeds, and inferred power curves are frequently made, despite the total absence of uncertainty estimates of the theoretically predicted quantities. Here the method for correct calculation of uncertainty estimates in mechanical power models is outlined in detail, and analytical and numerical results are derived for realistic examples.

A non-radioactive assay system for screening for inhibitors of RNA-dependent reverse transcriptase activity; an analysis using aurintricarboxylic acid and plant flavonoids.

Ongoing and extensive screening for potentially selective and potent inhibitors of RNA-dependent DNA polymerases (reverse transcriptases) is important for the discovery of therapeutic agents active against retroviruses. Traditional systems for assaying the activity of reverse transcriptase enzymes have relied upon the use of radioactive nucleotides for monitoring complementary DNA (cDNA) synthesis. Moreover, such assays have also typically been programmed by the addition of synthetic template-primers.

Allosteric mechanism for translational repression in the Escherichia coli alpha operon.

The ribosomal protein S4 is a translational repressor that binds to a complex mRNA pseudoknot structure containing the ribosome binding site for the first gene of the alpha operon. Either 30S subunits or S4 protein bound to the mRNA causes Moloney murine leukemia virus reverse transcriptase to pause near the 3' terminus of the pseudoknot. There is no competition between subunits and S4 for mRNA binding.

Ribosome initiation complex formation with the pseudoknotted alpha operon messenger RNA.

The Escherichia coli alpha mRNA has a complex pseudoknot secondary structure that forms the recognition site for a translational repressor, ribosomal protein S4, and also encompasses the regulated ribosome binding site. To find out whether the pseudoknot is a stable structure under the conditions of ribosome initiation complex formation, thermal denaturation of the RNA was monitored by calorimetry and ultraviolet light hyperchromicity. The secondary structure formed by the coding region melts in a single transition and has a stability of -7.

Inhibition of reverse transcriptases by flavonoids.

Selected naturally occurring flavonoids were shown to inhibit three reverse transcriptases (RT): avian myeloblastosis (AMV) RT, Rous-associated virus-2 (RAV-2) RT and Maloney murine leukemia virus (MMLV) RT when poly (rA)oligo(dT)12-18 or rabbit globin mRNA were used as template. Amentoflavone, scutellarein and quercetin were the most active compounds and their effect was concentration-dependent. The enzymes exhibited differential sensitivity to the inhibitory effects of the flavonoids.

Identification of the altered ribosomal component responsible for resistance to micrococcin in mutants of Bacillus megaterium.

A mutant strain of Bacillus megaterium, arising spontaneously and resistant to micrococcin , possesses ribosomes which contain an altered form of protein BM-L11 (the homologue of Escherichia coli protein L11). Reconstitution analysis has revealed that the alteration to protein BM-L11 is the sole cause of resistance in this strain.