The Use of Wheel Brakes on Airplanes

The results of tests to determine the effect of wheel brakes on the landing run of an airplane under conditions of load and at various wind velocities are presented

The NACA full-scale wind tunnel

This report gives a complete description of the full-scale wind tunnel of the National Advisory Committee for Aeronautics

The Aerodynamic Effect of a Retractable Landing Gear

Tests were conducted in the N.A.C.A. full scale wind tunnel at the request of the Army Air Corps to determine the effect of retractable landing gear openings in the bottom surface of a wing upon the characteristics of a Lockheed Altair airplane. The tests were extended to include the determination of the lift and drag characteristics throughout the angle-of-attack range with the landing gear both retracted and extended. Covering the wheel openings in the wing with sheet metal when the wheels were extended reduced the drag only 2 percent at a lift coefficient of 1.0, which was assumed for the take-off condition. Therefore, the wheel openings in the bottom side of the wing have a negligible effect upon the take-off of the airplane. Retracting the landing gear reduced the minimum drag of the complete airplane 50 percent

Assessing the quality of footwear marks recovered from simulated graves

Footwear marks are one of the most frequently encountered evidence types recovered from a crime scene and can provide valuable scene intelligence regarding potential suspects. It has been acknowledged that impressions of footwear and tools can be recovered from graves, but previous studies have only focused on tool mark recovery. This has led to a lack of published information regarding footwear mark recovery from graves. It is therefore important to demonstrate whether the recovery of footwear marks is feasible and, if so, under what conditions this can be achieved. To address recovery, this study, placed 60 three dimensional (3D) impressions of footwear marks within 60 simulated graves. This was done to assess time (1, 2, 4 months) and at known depths (20, 30, 40 cm). The footwear marks within the graves were covered with clothing or left uncovered. The shoe’s design patterns were grouped and counted in a photographic comparison between the 3D footwear impressions, placed within the test-pits, and any recovered impressions. A grading system was adapted by the authors to score the quality of footwear impressions observed during recovery. The results demonstrate that the preservation and recovery of footwear impressions from graves is feasible. The simulated graves covered with clothing showed better preservation of footwear impressions, but there was no clear evidence that time or depth had an effect. The authors note that careful consideration and vigilant excavation skills are needed when excavating graves which may bear potential footwear marks, as their recovery will lead to an increased amount of intelligence that can link suspects to homicide scenes

Investigating the global dispersal of chickens in prehistory using ancient mitochondrial dna signatures

Data from morphology, linguistics, history, and archaeology have all been used to trace the dispersal of chickens from Asian domestication centers to their current global distribution. Each provides a unique perspective which can aid in the reconstruction of prehistory. This study expands on previous investigations by adding a temporal component from ancient DNA and, in some cases, direct dating of bones of individual chickens from a variety of sites in Europe, the Pacific, and the Americas. The results from the ancient DNA analyses of forty-eight archaeologically derived chicken bones provide support for archaeological hypotheses about the prehistoric human transport of chickens. Haplogroup E mtDNA signatures have been amplified from directly dated samples originating in Europe at 1000 B.P. and in the Pacific at 3000 B.P. indicating multiple prehistoric dispersals from a single Asian centre. These two dispersal pathways converged in the Americas where chickens were introduced both by Polynesians and later by Europeans. The results of this study also highlight the inappropriate application of the small stretch of D-loop, traditionally amplified for use in phylogenetic studies, to understanding discrete episodes of chicken translocation in the past. The results of this study lead to the proposal of four hypotheses which will require further scrutiny and rigorous future testingExcavations in Fais by MI were made possible by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science. DB gratefully acknowledges support from the Marsden Fund, and the Allan Wilson Centre for Molecular Ecology and Evolution. During the course of this research AS was supported by a Postgraduate Scholarship from the University of Auckland and a Fellowship from the Allan Wilson Centre for Molecular Ecology and Evolutio

Ancient DNA of guinea pigs (Cavia spp.) indicates a probable new center of domestication and pathways of global distribution

Guinea pigs (Cavia spp.) have a long association with humans. From as early as 10,000 years ago they were a wild food source. Later, domesticated Cavia porcellus were dispersed well beyond their native range through pre-Columbian exchange networks and, more recently, widely across the globe. Here we present 46 complete mitogenomes of archaeological guinea pigs from sites in Peru, Bolivia, Colombia, the Caribbean, Belgium and the United States to elucidate their evolutionary history, origins and paths of dispersal. Our results indicate an independent centre of domestication of Cavia in the eastern Colombian Highlands. We identify a Peruvian origin for the initial introduction of domesticated guinea pigs (Cavia porcellus) beyond South America into the Caribbean. We also demonstrate that Peru was the probable source of the earliest known guinea pigs transported, as part of the exotic pet trade, to both Europe and the southeastern United States. Finally, we identify a modern reintroduction of guinea pigs to Puerto Rico, where local inhabitants use them for food. This research demonstrates that the natural and cultural history of guinea pigs is more complex than previously known and has implications for other studies regarding regional to global-scale studies of mammal domestication, translocation, and distribution.Fil: Lord, E.. Stockholms Universitet; Suecia. University of Otago; Nueva ZelandaFil: Collins, C.. University of Otago; Nueva ZelandaFil: deFrance, S.. University of Florida; Estados UnidosFil: LeFebvre, M. J.. University of Florida; Estados UnidosFil: Pigière, F.. Universidad de Dublin; IrlandaFil: Eeckhout, P.. Université Libre de Bruxelles; BélgicaFil: Erauw, C.. Université Libre de Bruxelles; BélgicaFil: Fitzpatrick, S. M.. State University of Oregon; Estados UnidosFil: Healy, P. F.. Trent University; CanadáFil: Martínez Polanco, M. F.. Muséum National d'Histoire Naturelle; Francia. Universitat Rovira I Virgili; España. Institut Català de Paleoecologia Humana i Evolució Social; EspañaFil: Garcia, J. L.. Stetson University; Estados UnidosFil: Ramos Roca, E.. Universidad de los Andes. Facultad de Ciencias Sociales. Departamento de Antropología; ColombiaFil: Delgado Burbano, Miguel Eduardo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Área Antropológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. School of Life Sciences and Human Phenome Institute Fudan University; ChinaFil: Sánchez Urriago, A.. Instituto Colombiano de Antropología e Historia; ColombiaFil: Peña Léon, G. A.. Universidad Nacional de Colombia; ColombiaFil: Toyne, J. M.. University of Florida; Estados UnidosFil: Dahlstedt, A.. Arizona State University; Estados UnidosFil: Moore, K. M.. State University of Pennsylvania; Estados UnidosFil: Laguer Diaz, C.. University of Florida; Estados UnidosFil: Zori, C.. Baylor University; Estados UnidosFil: Matisoo-Smith, E.. University of Otago; Nueva Zeland

NACA Technical Notes

"Tests were conducted in the N.A.C.A. full scale wind tunnel at the request of the Army Air Corps to determine the effect of retractable landing gear openings in the bottom surface of a wing upon the characteristics of a Lockheed Altair airplane. The tests were extended to include the determination of the lift and drag characteristics throughout the angle-of-attack range with the landing gear both retracted and extended. Covering the wheel openings in the wing with sheet metal when the wheels were extended reduced the drag only 2 percent at a lift coefficient of 1.0, which was assumed for the take-off condition" (p. 1)

NACA Technical Reports

This report gives a complete description of the full-scale wind tunnel of the National Advisory Committee for Aeronautics

NACA Technical Notes

The results of tests to determine the effect of wheel brakes on the landing run of an airplane under conditions of load and at various wind velocities are presented