Flight Mechanics and Control of Escape Manoeuvres in Hummingbirds. I. Flight Kinematics

Hummingbirds are nature’s masters of aerobatic manoeuvres. Previous research shows that hummingbirds and insects converged evolutionarily upon similar aerodynamic mechanisms and kinematics in hovering. Herein, we use three-dimensional kinematic data to begin to test for similar convergence of kinematics used for escape flight and to explore the effects of body size upon manoeuvring. We studied four hummingbird species in North America including two large species (magnificent hummingbird, Eugenes fulgens, 7.8 g, and blue-throated hummingbird, Lampornis clemenciae, 8.0 g) and two smaller species (broad-billed hummingbird, Cynanthus latirostris, 3.4 g, and black-chinned hummingbirds Archilochus alexandri, 3.1 g). Starting from a steady hover, hummingbirds consistently manoeuvred away from perceived threats using a drastic escape response that featured body pitch and roll rotations coupled with a large linear acceleration. Hummingbirds changed their flapping frequency and wing trajectory in all three degrees of freedom on a stroke-by-stroke basis, likely causing rapid and significant alteration of the magnitude and direction of aerodynamic forces. Thus it appears that the flight control of hummingbirds does not obey the ‘helicopter model’ that is valid for similar escape manoeuvres in fruit flies. Except for broad-billed hummingbirds, the hummingbirds had faster reaction times than those reported for visual feedback control in insects. The two larger hummingbird species performed pitch rotations and global-yaw turns with considerably larger magnitude than the smaller species, but roll rates and cumulative roll angles were similar among the four species

Flight Mechanics and Control of Escape Manoeuvres in Hummingbirds. II. Aerodynamic Force Production, Flight Control and Performance Limitations

The superior manoeuvrability of hummingbirds emerges from complex interactions of specialized neural and physiological processes with the unique flight dynamics of flapping wings. Escape manoeuvring is an ecologically relevant, natural behaviour of hummingbirds, from which we can gain understanding into the functional limits of vertebrate locomotor capacity. Here, we extend our kinematic analysis of escape manoeuvres from a companion paper to assess two potential limiting factors of the manoeuvring performance of hummingbirds: (1) muscle mechanical power output and (2) delays in the neural sensing and control system. We focused on the magnificent hummingbird (Eugenes fulgens, 7.8 g) and the black-chinned hummingbird (Archilochus alexandri, 3.1 g), which represent large and small species, respectively. We first estimated the aerodynamic forces, moments and the mechanical power of escape manoeuvres using measured wing kinematics. Comparing active-manoeuvring and passive-damping aerodynamic moments, we found that pitch dynamics were lightly damped and dominated by the effect of inertia, while roll dynamics were highly damped. To achieve observed closed-loop performance, pitch manoeuvres required faster sensorimotor transduction, as hummingbirds can only tolerate half the delay allowed in roll manoeuvres. Accordingly, our results suggested that pitch control may require a more sophisticated control strategy, such as those based on prediction. For the magnificent hummingbird, we estimated that escape manoeuvres required muscle mass-specific power 4.5 times that during hovering. Therefore, in addition to the limitation imposed by sensorimotor delays, muscle power could also limit the performance of escape manoeuvres

Catecholborane Reductions of Ditosylhydrozones to the Corresponding Methylene Derivatives

The smooth deoxygenation of diketones via the Catecholborane reduction of the corresponding ditosylhydrzaones is described. The reductions occur under mild conditions and are suitable for sensitive compounds

Current Distribution in the Three-Dimensional Random Resistor Network at the Percolation Threshold

We study the multifractal properties of the current distribution of the three-dimensional random resistor network at the percolation threshold. For lattices ranging in size from $8^3$ to $80^3$ we measure the second, fourth and sixth moments of the current distribution, finding {\it e.g.\/} that $t/\nu=2.282(5)$ where $t$ is the conductivity exponent and $\nu$ is the correlation length exponent.Comment: 10 pages, latex, 8 figures in separate uuencoded fil

Equidistribution of zeros of holomorphic sections in the non compact setting

We consider N-tensor powers of a positive Hermitian line bundle L over a non-compact complex manifold X. In the compact case, B. Shiffman and S. Zelditch proved that the zeros of random sections become asymptotically uniformly distributed with respect to the natural measure coming from the curvature of L, as N tends to infinity. Under certain boundedness assumptions on the curvature of the canonical line bundle of X and on the Chern form of L we prove a non-compact version of this result. We give various applications, including the limiting distribution of zeros of cusp forms with respect to the principal congruence subgroups of SL2(Z) and to the hyperbolic measure, the higher dimensional case of arithmetic quotients and the case of orthogonal polynomials with weights at infinity. We also give estimates for the speed of convergence of the currents of integration on the zero-divisors.Comment: 25 pages; v.2 is a final update to agree with the published pape

Conflict resolution between husband and wife in the light of the hermeneutics of biblical proverbs

Conflicts are commonplace in human relationships. The Bible is replete with narratives and proverbial statements which border on conflict scenarios and conflict resolution strategies. Conflict cannot be severed from relationships between biological brothers and sisters, Christians, friends, colleagues and husbands and wives. In this qualitative study, the researchers examined the menace ‘conflict between husbands and wives’. There is no husband and wife relationship which is devoid of disputes and conflicts. In husband and wife relationship, conflict situations could arise from lack of sexual discipline, lack of sexual satisfaction, finance, lack of communication and other areas. The thrust of this article was to examine conflict resolution principles in the light of biblical proverbs. Biblical proverbs refer to concise and wise sayings in the Bible, which give pieces of advice about everyday life. This article utilised the descriptive research methodology to analyse the primary (Bible) and secondary (Internet materials, journal articles and books) data. The major finding of this work are numerous biblical proverbs which are veritable means for resolving conflicts between husbands and wives. CONTRIBUTION: The article brought to fore the major factors which lead to conflict between husbands and wives. The authors exegetically studied the chosen proverbs in order to ascertain its relevance to conflict situations. The major contribution of this article is that the messages of certain proverbs in the Book of Proverbs are very useful in resolving conflicts between husbands and wives.http://www.hts.org.zapm2020New Testament Studie

The impact of HIV knowledge and attitudes on HIV testing acceptance among patients in an emergency department in the Eastern Cape, South Africa

Background: Transmission of HIV in South Africa continues to be high due to a large proportion of individuals living with undiagnosed HIV. Uptake of HIV testing is influenced by a multitude of factors including the patient’s knowledge and beliefs about HIV. Methods: This study sought to quantify the impact of knowledge and attitudes on HIV testing acceptance in an emergency department by co-administering a validated HIV knowledge and attitudes survey to patients who were subsequently offered HIV testing. Results: During the study period 223 patients were interviewed and offered HIV testing. Individuals reporting more negative overall attitudes (p = 0.006), higher levels of stigma to HIV testing (p < 0.001), and individuals who believed their test was confidential (p < 0.001) were more likely to accept an HIV test. Conclusions: Interventions focused on improving patient perceptions around testing confidentiality will likely have the greatest impact on testing acceptance in the emergency department

The impact of HIV knowledge and attitudes on HIV testing acceptance among patients in an emergency department in the Eastern Cape, South Africa

Background: Transmission of HIV in South Africa continues to be high due to a large proportion of individuals living with undiagnosed HIV. Uptake of HIV testing is influenced by a multitude of factors including the patient’s knowledge and beliefs about HIV. Methods: This study sought to quantify the impact of knowledge and attitudes on HIV testing acceptance in an emergency department by co-administering a validated HIV knowledge and attitudes survey to patients who were subsequently offered HIV testing. Results: During the study period 223 patients were interviewed and offered HIV testing. Individuals reporting more negative overall attitudes (p = 0.006), higher levels of stigma to HIV testing (p < 0.001), and individuals who believed their test was confidential (p < 0.001) were more likely to accept an HIV test. Conclusions: Interventions focused on improving patient perceptions around testing confidentiality will likely have the greatest impact on testing acceptance in the emergency department

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results