The influence of wing–wake interactions on the production of aerodynamic forces in flapping flight

We used two-dimensional digital particle image velocimetry (DPIV) to visualize flow patterns around the flapping wing of a dynamically scaled robot for a series of reciprocating strokes starting from rest. The base of the wing was equipped with strain gauges so that the pattern of fluid motion could be directly compared with the time history of force production. The results show that the development and shedding of vortices throughout each stroke are highly stereotyped and influence force generation in subsequent strokes. When a wing starts from rest, it generates a transient force as the leading edge vortex (LEV) grows. This early peak, previously attributed to added-mass acceleration, is not amenable to quasi-steady models but corresponds well to calculations based on the time derivative of the first moment of vorticity within a sectional slice of fluid. Forces decay to a stable level as the LEV reaches a constant size and remains attached throughout most of the stroke. The LEV grows as the wing supinates prior to stroke reversal, accompanied by an increase in total force. At stroke reversal, both the LEV and a rotational starting vortex (RSV) are shed into the wake, forming a counter-rotating pair that directs a jet of fluid towards the underside of the wing at the start of the next stroke. We isolated the aerodynamic influence of the wake by subtracting forces and flow fields generated in the first stroke, when the wake is just developing, from those produced during the fourth stroke, when the pattern of both the forces and wake dynamics has reached a limit cycle. This technique identified two effects of the wake on force production by the wing: an early augmentation followed by a small attenuation. The later decrease in force is consistent with the influence of a decreased aerodynamic angle of attack on translational forces caused by downwash within the wake and is well explained by a quasi-steady model. The early effect of the wake is not well approximated by a quasi-steady model, even when the magnitude and orientation of the instantaneous velocity field are taken into account. Thus, the wake capture force represents a truly unsteady phenomenon dependent on temporal changes in the distribution and magnitude of vorticity during stroke reversal

Testing Mediated Effects of a Sex Education Program on Youth Sexual Activity

Empirical investigations have identified hundreds of factors that predict whether youth engage in sexual activity (YSA). To promote optimal health and the avoidance of unhealthy or problematic outcomes that can result from YSA, sex education programs have been extensively developed and evaluated. Many evaluations have identified the effect of the program on immediate outcomes such as attitudes and intentions, others have examined subsequent behavioral and health outcomes, and some have done both. The purpose of this study was to extend the evaluation literature by testing a mediated effects model. A sex education program was found to have significant immediate effects on several attitudinal factors that have been shown to predict YSA, and was shown to significantly reduce the incidence of sexual activity approximately one year after the program (OR = 0.534, p = .004). A mediating effects test showed that youth’s stated intentions to engage in sexual activity was a significant mediated effect (B = -0.182, Lower CI = -0.291, Upper CI = -0.073), suggesting that the program effects on sexual activity occurred through the immediate effect on intentions, which in turn was likely affected by program content, which changed other attitudinal factors such as values, efficacy, and knowledge. Using immediate changes on these mediating factors to predict the likelihood of YSA showed that accurate prediction was possible, with an overall prediction accuracy rate of 74%. It was easier to predict who was not going to engage in YSA (94% accuracy) than who would (35% accuracy). Further predictive analyses showed that a score of 4.12 (on a scale of 1 to 5) on agreement with the items comprising the mediating factors’ scales was a threshold point, with the likelihood of engaging in YSA rising sharply as a function of this score until that point, and score increases above that point resulting in minimal changes in the probability of YSA. The results of this study demonstrate that it is possible to reduce YSA, that intent to engage in YSA was a primary mediator, and that accurate prediction of eventual behavioral results is possible, based on analysis of immediate results

Queller’s separation condition explained and defended

The theories of inclusive fitness and multilevel selection provide alternative perspectives on social evolution. The question of whether these perspectives are of equal generality remains a divisive issue. In an analysis based on the Price equation, Queller argued (by means of a principle he called the separation condition) that the two approaches are subject to the same limitations, arising from their fundamentally quantitative-genetical character. Recently, van Veelen et al. have challenged Queller’s results, using this as the basis for a broader critique of the Price equation, the separation condition, and the very notion of inclusive fitness. Here we show that the van Veelen et al. model, when analyzed in the way Queller intended, confirms rather than refutes his original conclusions. We thereby confirm (i) that Queller’s separation condition remains a legitimate theoretical principle and (ii) that the standard inclusive fitness and multilevel approaches are indeed subject to the same limitations

Can fundamental movement skill mastery be increased via a six week physical activity intervention to have positive effects on physical activity and physical self-perception?

Previous research has suggested a positive relationship between fundamental movement skills (FMS) mastery and physical activity (PA) level. Research conducted on interventions to improve FMS mastery is equivocal and further research is needed.An intervention group of 82 children (35 boys and 47 girls) and a control group of 83 children (42 boys and 41 girls) were recruited from Years 4 and 5 (mean age ± SD = 8.3 ± 0.4 years) of two schools in Central England. The intervention included a combination of circuits and dancing to music. Pre and post intervention tests were conducted. Tests included: subjective assessment of eight FMS; objective measurement of two FMS; four day pedometer step count recording; height and mass for Body Mass Index (BMI); and the completion of Harter et al.'s (1982) self-perception questionnaire.Following a two (pre to post) by two (intervention and control group) mixed-model ANOVA it was highlighted that the intervention group improved mastery in all eight FMS, and increased both daily steps and physical self-perception.It can be concluded that focussing one Physical Education (PE) lesson per week on the development of FMS has had a positive benefit on FMS, PA level and physical self-perception for the children in this study

International Capital Taxation.

Globalization carries profound implications for tax systems, yet most tax systems, including that of the UK, still retain many features more suited to closed economies. The purpose of this chapter is to assess how tax policy should reflect the changing international economic environment. Institutional barriers to the movement of goods, services, capital, and (to a lesser extent) labour have fallen dramatically since the Meade Report (Meade, 1978) was published. So have the costs of moving both real activity and taxable profits between tax jurisdictions. These changes mean that capital and taxable profits in particular are more mobile between jurisdictions than they used to be. Our focus is on the taxation of capital and our main conclusions may be summarized as follows

THE DETERMINATION OF THE OPTICAL CONSTANTS OF SOME SILICATE GLASSES AT MILLIMETRE AND SUBMILLIMETRE WAVELENGTHS

PhDThis work has two interlocking themes. It is primarily concerned with the development of precise, broad band, Fourier transform spectrometric techniques for the determination of the optical constants of solids at millimetre and submillimetre wavelengths. One such technique cannot easily accomodate the wide range of optical constants found in solids, leading to specimens which range from the virtually transparent to the virtually opaque, and it was therefore necessary to develop transmission and reflection techniques. The intercomparison of these techniques, their particular experimental difficulties and susceptibilities to random and systematic error, was performed by using each method to determin'the optical constants of soda lime silica glass over as wide a spectral range as possible. Previous to this work there had been no systematic study of this important material at these wavelengths and,thus, this investigation gave the second theme of this work, the quantitative determination of the optical constants of soda lime silica glass at millimetre and submillimetre wavelengths. The results of this study are presented in four chapters. First, in chapter 5, power transmission Fourier transform spectrometry has been used to investigate the spectral variation of the optical constants of the glass between 3 and 50cm, using an analysis of channel spectra to give the refractive index. This chapter also contains the results of measurements made with a grating instrument between 1000 and k000cm. Secondly, in chapter 6, the results of the first direct determinations of the optical constants by dispersive transmission Fourier transform spectrometry are presented and shown to indicate the presence of a hitherto unknown loss process below 20er that is tentatively associated with a similar process previously observed in fused silica. Thirdly, in chapter 7, dispersive reflection Fourier transform spectrometry has been used to determin the optical constants up to 360em, well into the midinfrared region of opacity of this glass. The results of chapters 6 and 7 provide the first quantitative description of the optical constants of this glass betweem 3 and 360em Finally, in chapter 8, the dispersive reflection measurements are extended to simple binary and ternary silicate glasses, and these results used to identify the contributions to the mid-infrared absorption of the metal ions associated with the various metal oxide additives of the glass. From this it was possible to account for all of the absorption in soda lime silica glass as a superposition of contributions from the near-infrared bands of the SiO1 network of the glass and the four main metal ions

Can fundamental movement skill mastery be increased via a six week physical activity intervention to have positive effects on physical activity and physical self-perception?

Previous research has suggested a positive relationship between fundamental movement skills (FMS) mastery and physical activity (PA) level. Research conducted on interventions to improve FMS mastery is equivocal and further research is needed.An intervention group of 82 children (35 boys and 47 girls) and a control group of 83 children (42 boys and 41 girls) were recruited from Years 4 and 5 (mean age ± SD = 8.3 ± 0.4 years) of two schools in Central England. The intervention included a combination of circuits and dancing to music. Pre and post intervention tests were conducted. Tests included: subjective assessment of eight FMS; objective measurement of two FMS; four day pedometer step count recording; height and mass for Body Mass Index (BMI); and the completion of Harter et al.'s (1982) self-perception questionnaire.Following a two (pre to post) by two (intervention and control group) mixed-model ANOVA it was highlighted that the intervention group improved mastery in all eight FMS, and increased both daily steps and physical self-perception.It can be concluded that focussing one Physical Education (PE) lesson per week on the development of FMS has had a positive benefit on FMS, PA level and physical self-perception for the children in this study