Forcing boundary-layer transition on an inverted airfoil in ground effect and at varying incidence

Presented at 34th AIAA Applied Aerodynamics ConferenceThe influence of the laminar boundary-layer state on a wing operating in ground effect at Re = 6 × 10 has been investigated using experiments with a model that provides two-dimensional flow and computations with a panel-method code. The effect of a boundary-layer trip placed at varying distances from the leading edge was observed at various incidences in terms of on-surface characteristics, including pressure measurements, flow visualisation and hot-film anemometry, and off-surface characteristics with LDA surveys below and behind the wing. The act of forcing transition led to downforce being reduced and drag increased, moreover, it altered almost all aspects of the wing’s aerodynamic characteristics, with the effect becoming greater as the trip was placed closer to the leading edge. These aspects include the replacement of a laminar separation bubble with trailing-edge separation, a thicker boundary layer, and a thicker wake with greater velocity deficit. The importance of considering laminar phenomena for wings operating in ground effect has been show

Fiddler crabs (Afruca tangeri) detect second-order motion in both intensity and polarization

Motion vision is vital for a wide range of animal behaviors. Fiddler crabs, for example, rely heavily on motion to detect the movement of avian predators. They are known to detect first-order motion using both intensity (defined by spatiotemporal correlations in luminance) and polarization information (defined separately as spatiotemporal correlations in the degree and/or angle of polarization). However, little is known about their ability to detect second-order motion, another important form of motion information; defined separately by spatiotemporal correlations in higher-order image properties. In this work we used behavioral experiments to test how fiddler crabs (Afruca tangeri) responded to both second-order intensity and polarization stimuli. Fiddler crabs responded to a number of different intensity based second-order stimuli. Furthermore, the crabs also responded to second-order polarization stimuli, a behaviorally relevant stimulus applicable to an unpolarized flying bird when viewed against a polarized sky. The detection of second-order motion in polarization is, to the best of our knowledge, the first demonstration of this ability in any animal. This discovery therefore opens a new dimension in our understanding of how animals use polarization vision for target detection and the broader importance of second-order motion detection for animal behavior

Clostridium novyi-NT in cancer therapy

AbstractThe attenuated anaerobic bacterium Clostridium novyi-NT (C. novyi-NT) is known for its ability to precisely germinate in and eradicate treatment-resistant hypoxic tumors in various experimental animal models and spontaneously occurring canine sarcomas. In this article, we review the therapeutic and toxicologic aspects of C. novyi-NT therapy, key challenges and limitations, and promising strategies to optimize its performance via recombinant DNA technology and immunotherapeutic approaches, to establish C. novyi-NT as an essential tool in cancer therapy

Forcing boundary-layer transition on an inverted airfoil in ground effect

The influence of the laminar boundary-layer state on a wing operating in ground effect has been investigated using experiments with a model that provides two-dimensional flow. The effect of a boundary-layer trip placed at varying distances from the leading edge was observed at various incidences in terms of on-surface characteristics, including pressure measurements, flow visualization, and hot-film anemometry, and off-surface characteristics with velocity surveys below and behind the wing. The act of forcing transition led to downforce being reduced and drag increased, moreover, it altered almost all aspects of the wing’s aerodynamic characteristics, with the effect becoming greater as the trip was placed closer to the leading edge. These aspects include the replacement of a laminar separation bubble with trailing-edge separation, a thicker boundary layer, and a thicker wake with greater velocity deficit. The importance of considering laminar phenomena for wings operating in ground effect has been shown

The effects of surface structure mutations in <i>Arabidopsis thaliana</i> on the polarization of reflections from virus-infected leaves

<div><p>The way in which light is polarized when reflected from leaves can be affected by infection with plant viruses. This has the potential to influence viral transmission by insect vectors due to altered visual attractiveness of infected plants. The optical and topological properties of cuticular waxes and trichomes are important determinants of how light is polarized upon reflection. Changes in expression of genes involved in the formation of surface structures have also been reported following viral infection. This paper investigates the role of altered surface structures in virus-induced changes to polarization reflection from leaves. The percentage polarization of reflections from <i>Arabidopsis thaliana cer5</i>, <i>cer6</i> and <i>cer8</i> wax synthesis mutants, and the <i>gl1</i> leaf hair mutant, was compared to those from wild-type (WT) leaves. The <i>cer5</i> mutant leaves were less polarizing than WT on the adaxial and abaxial surfaces; <i>gl1</i> leaves were more polarizing than WT on the adaxial surfaces. The <i>cer6</i> and <i>cer8</i> mutations did not significantly affect polarization reflection. The impacts of <i>Turnip vein clearing virus</i> (TVCV) infection on the polarization of reflected light were significantly affected by <i>cer5</i> mutation, with the reflections from <i>cer5</i> mutants being higher than those from WT leaves, suggesting that changes in <i>CER5</i> expression following infection could influence the polarization of the reflections. There was, however, no significant effect of the <i>gl1</i> mutation on polarization following TVCV infection. The <i>cer5</i> and <i>gl1</i> mutations did not affect the changes in polarization following <i>Cucumber mosaic virus</i> (CMV) infection. The accumulation of TVCV and CMV did not differ significantly between mutant and WT leaves, suggesting that altered expression of surface structure genes does not significantly affect viral titres, raising the possibility that if such regulatory changes have any adaptive value it may possibly be through impacts on viral transmission.</p></div

Environmental Policy Update 2012: Development Strategies and Environmental Policy in East Africa

The seven chapters that comprise this report explore ways to integrate sustainability goals and objectives into Ethiopia's current development strategies

Predicting the diversity of early epidemic spread on networks

The course of an epidemic exhibits average growth dynamics determined by features of the pathogen and the population, yet also features significant variability reflecting the stochastic nature of disease spread. The interplay of biological, social, structural and random factors makes disease forecasting extraordinarily complex. In this work, we reframe a stochastic branching process analysis in terms of probability generating functions and compare it to continuous time epidemic simulations on networks. In doing so, we predict the diversity of emerging epidemic courses on both homogeneous and heterogeneous networks. We show how the challenge of inferring the early course of an epidemic falls on the randomness of disease spread more so than on the heterogeneity of contact patterns. We provide an analysis which helps quantify, in real time, the probability that an epidemic goes supercritical or conversely, dies stochastically. These probabilities are often assumed to be one and zero, respectively, if the basic reproduction number, or R0, is greater than 1, ignoring the heterogeneity and randomness inherent to disease spread. This framework can give more insight into early epidemic spread by weighting standard deterministic models with likelihood to inform pandemic preparedness with probabilistic forecasts