The Energy Benefits of the Pantograph Wing Mechanism in Flapping Flight: Case Study of a Gull

Bird wings generally contain a 4-bar pantograph mechanism in the forearm that enables the wrist joint to be actuated from the elbow joint thus reducing the number of wing muscles and hence reducing the wing inertia and inertial drag. In this paper we develop a theoretical model of inertial power for flapping flight to estimate the advantage of the 4-bar pantograph mechanism by comparing the inertial power required for the case where wrist muscles are present in the forearm with the case where wrist muscles are not present in the forearm. It is difficult to predict how wrist muscles would look when there is no pantograph mechanism. Therefore a lower bound and upper bound case are defined. The lower bound case involves redistributing the elbow muscles with no increase in wing mass. The upper bound case involves replicating the biceps-triceps muscles near the wrist joint. At minimum power speed the model estimates that the 4-bar pantograph mechanism reduces the inertial power for the gull from between 6.1%-12.3% and reduces the overall power by 0.6%-1.2%. When account is taken of the tight margins involved in the design of a flying vehicle, the energy savings produced by the pantograph mechanism are significant. A ring-billed gull was chosen for the case study and an adult specimen was obtained to gather morphometric data. Lessons for the design of flapping micro air vehicles are discussed

A Technique for Evaluating Observer Efficiency in Raptor Migration Counts

A technique is described for sampling sections of the sky individually during a raptor migration count to obtain an unbiased estimate of the true number of raptors passing. This allows an estimate to be made of the efficiency of raptor detection by an observer counting at the same location and time. Practical and statistical issues are addressed that must be understood for efficient use of the technique

Morphometric Variation as an Indicator of Genetic Interactions between Black-capped and Carolina Chickadees at a Contact Zone in the Appalachian Mountains

We studied hybridization and introgression between Black-capped (Poecile atricapillus) and Carolina (P. carolinensis) chickadees along two transects in the Appalachians using four genetic markers and multivariate analysis of morphology. Genetic data revealed that at least 58% of the birds in the center of each transect were of mixed ancestry and that recombinant genotypes predominated among hybrids, demonstrating that hybridization is frequent and that many hybrids are fertile. Genetic clines generally were steep and coincident in position, but introgression was evident well beyond the range interface. Introgression was higher at the one autosomal locus surveyed than in mitochondrial DNA or in two sexlinked markers, suggesting that the hybrid zone is a conduit for gene flow between the two forms at some loci. On a broad scale, morphometric variation was concordant with genetic variation. Clines in morphological variation based on principal components (PC) scores were steep and coincident with genetic clines. Also, a strong correlation within a population between PC scores and an individual\u27s genetic makeup suggested that a large amount of morphological variation was genetically determined. However, morphological analysis indicated that hybrids were uncommon on one transect, whereas genetic data clearly showed that they were common on both. In addition, patterns of morphological variation were equivocal regarding introgression across the hybrid zone. Thus, genetic data provided a complementary and more detailed assessment of hybridization, largely due to the discrete nature of genetic variation. Genetic markers are useful in understanding hybridization and introgression, but diagnostic markers may underestimate average gene flow if selection against hybrids maintains steep clines at diagnostic loci. To gain a clearer picture of the genome-wide effects of hybridization. A much larger number of loci must be assayed, including non-diagnostic ones

Reproductive Isolation and Cryptic Introgression in a Sky Island Enclave of Appalachian Birds

Reproductive isolation is central to the speciation process, and cases where the strength of reproductive isolation varies geographically can inform our understanding of speciation mechanisms. Although generally treated as separate species, Black-capped chickadees (Poecile atricapillus) and Carolina chickadees (P. carolinensis) hybridize and undergo genetic introgression in many areas where they come into contact across the eastern United States and in the northern Appalachian Mountains. The Great Smoky Mountains harbor the last large breeding population of atricapillus in the southern Appalachians, isolated from the species’ main range by nearly 200 km. This population is believed to be reproductively isolated from local carolinensis due to an unusual, behaviorally mediated elevational range gap, which forms during the breeding season and may function as an incipient reproductive isolating mechanism. We examined the effectiveness of this putative isolating mechanism by looking for genetic introgression from carolinensis in Great Smoky Mountain atricapillus. We characterized this population and parental controls genetically using hundreds of amplified fragment length polymorphism (AFLP) loci as well as mitochondrial DNA (mtDNA) sequence data from cytochrome-b. Great Smoky Mountain atricapillus have experienced nuclear genetic introgression from carolinensis, but at much lower levels than other populations near the hybrid zone to the north. No mitochondrial introgression was detected, in contrast to northern contact areas. Thus, the seasonal elevational range gap appears to have been effective in reducing gene flow between these closely related taxa

Semantically Informed Multiview Surface Refinement

We present a method to jointly refine the geometry and semantic segmentation of 3D surface meshes. Our method alternates between updating the shape and the semantic labels. In the geometry refinement step, the mesh is deformed with variational energy minimization, such that it simultaneously maximizes photo-consistency and the compatibility of the semantic segmentations across a set of calibrated images. Label-specific shape priors account for interactions between the geometry and the semantic labels in 3D. In the semantic segmentation step, the labels on the mesh are updated with MRF inference, such that they are compatible with the semantic segmentations in the input images. Also, this step includes prior assumptions about the surface shape of different semantic classes. The priors induce a tight coupling, where semantic information influences the shape update and vice versa. Specifically, we introduce priors that favor (i) adaptive smoothing, depending on the class label; (ii) straightness of class boundaries; and (iii) semantic labels that are consistent with the surface orientation. The novel mesh-based reconstruction is evaluated in a series of experiments with real and synthetic data. We compare both to state-of-the-art, voxel-based semantic 3D reconstruction, and to purely geometric mesh refinement, and demonstrate that the proposed scheme yields improved 3D geometry as well as an improved semantic segmentation

An Assessment of Song Admixture as an Indicator of Hybridization in Black-capped Chickadees (Poecile atricapillus) and Carolina Chickadees (Poecile carolinensis)

Vocal admixture often occurs where differentiated populations or species of birds meet. This may entail song sympatry, bilingually singing birds, and songs with intermediate or atypical characteristics. Different levels of vocal admixture at the range interface between Black-capped Chickadees (Poecile atricapillus) and Carolina Chickadees (P. carolinensis) have been interpreted as indicating that hybridization is frequent at some locations but not others. However, song ontogeny in these birds has a strong nongenetic component, so that inferences regarding hybridization based on vocal admixture require confirmation. We used diagnostic genetic markers and quantitative analyses of song to characterize population samples along two transects of the chickadee contact zone in the Appalachian Mountains. More than 50% of individuals at the range interface were of hybrid ancestry, yet only 20% were observed to be bilingual or to sing atypical songs. Principal component analysis revealed minimal song intermediacy. This result contrasts with an earlier analysis of the hybrid zone in Missouri that found considerable song intermediacy. Re-analysis of the Missouri data confirmed this difference. Correlation between an individual\u27s genetic composition and its song type was weak in Appalachian hybrid populations, and genetic introgression in both forms extended far beyond the limits of vocal admixture. Therefore, song is not a reliable indicator of levels of hybridization or genetic introgression at this contact zone. Varying ecological factors may play a role in producing variable levels of song admixture in different regions of the range interface

Dislocation generation and propagation during flash lamp annealing

Dislocation generation and propagation during flash lamp annealing for 20 ms was investigated using wafers with sawed, ground, and etched surfaces. Due to the thermal stress resulting from the temperature profiles generated by the flash pre-existing dislocations propagate into the wafer from both surfaces during flash lamp annealing. A dislocation free zone was observed around 700 μm depth below the surface of a 900 μm thick sawed wafer. The dislocation propagation can be well described by a three-dimensional mechanical model. It was further demonstrated that in wafers being initially free of dislocations no dislocations are generated during flash lamp annealing