Search

We report here a stingray spine (Dasyatidae) found embedded in the femur of a male skeleton from the archaeological site of Uedomari-5, Rebun Island, Hokkaido, Japan. A single well-preserved but incomplete human skeleton. Macroscopic observation and low power magnification, CT imaging, radiocarbon dating and stable isotope (carbon, nitrogen) analysis. The stingray spine is tentatively identified as Bathytoshia brevicaudata. CT imaging shows no healing, indicating that death occurred shortly afterwards. The skeleton has been directly radiocarbon dated to the Okhotsk period (cal AD 429–827), with δ 13C (−13.7‰) and δ 15N (19.3‰) values indicating a diet focused on marine foods. The absence of healing in what would have been a non-lethal injury strongly suggests that the spine tipped an arrowhead, rather than being the result of an accidental encounter with a living stingray. It is possible that the injury reflects a period of increased conflict coinciding with, or following on from, the expansion of the Okhotsk culture from Sakhalin into northern Hokkaido. Uedomari-5 provides the first example, to our knowledge, of a stingray spine directly embedded in human bone at an archaeological site. More widely, the finding contributes to our knowledge of conflict in northern hunter-gatherer communities. Given the early excavation date (1949–50), there is little contextual information available for the burials. ZooMS (Zooarchaeology by Mass Spectrometry) may be able to identify the stingray species. Archival research may provide more information concerning the excavations at Uedomari-5. [ABSTRACT FROM AUTHOR]

A new design for a tail-sitter vertical takeoff and landing unmanned aerial vehicle was proposed. A nonlinear mathematical model of the vehicle dynamics was constructed by combining simple estimation methods. The flight characteristics were revealed through a trim analysis and an optimized transitional flight path analysis by using the mathematical model. The trim analysis revealed the existence of a flight path constraint to avoid stall; the vehicle could not descend in low-speed flight without high-lift devices such as flaps and slats. These devices improved the descent performance. In particular, slats provided a substantial improvement; they enabled a descent rate of 2 m/s. In the optimized transitional flight path analysis, a level outbound transition without high-lift devices was achieved although a trimmed level flight at low speed, as was shown in the trim analysis, was not possible; this was because the outbound transition was an accelerative flight. On the contrary, without high-lift devices, the vehicle could not avoid climbing to avoid stall during inbound transitions. The slats provided a satisfactory improvement during the transition and enabled a level inbound transition. These results showed the necessity of leading-edge slats for the proposed tail-sitter vertical takeoff and landing unmanned aerial vehicle.

The development of a real-world Unmanned Aircraft System (UAS) Traffic Management (UTM) system to ensure the safe integration of Unmanned Aerial Vehicles (UAVs) in low altitude airspace, has recently generated novel research challenges. A key problem is the development of Pre-Flight Conflict Detection and Resolution (CDR) methods that provide collision-free flight paths to all UAVs before their takeoff. Such problem can be represented as a Multi-Agent Path Finding (MAPF) problem. Currently, most MAPF methods assume that the UTM system is a centralized entity in charge of CDR. However, recent discussions on UTM suggest that such centralized control might not be practical or desirable. Therefore, we explore Pre-Flight CDR methods where independent UAS Service Providers (UASSPs) with their own interests, communicate with each other to resolve conflicts among their UAV operations—without centralized UTM directives. We propose a novel MAPF model that supports the decentralized resolution of conflicts, whereby different ‘agents’, here UASSPs, manage their UAV operations. We present two approaches: (1) a prioritization approach and (2) a simple yet practical pairwise negotiation approach where UASSPs agents determine an agreement to solve conflicts between their UAV operations. We evaluate the performance of our proposed approaches with simulation scenarios based on a consultancy study of predicted UAV traffic for delivery services in Sendai, Japan, 2030. We demonstrate that our negotiation approach improves the “fairness” between UASSPs, i.e. the distribution of costs between UASSPs in terms of total delays and rejected operations due to replanning is more balanced when compared to the prioritization approach. [ABSTRACT FROM AUTHOR]

This paper shows some guidelines to improve the estimation accuracy of a navigation system, which is based on wide‐field‐integration (WFI) of optic flow. Optic flow is a vector field of relative velocities obtained by photoreceptors in image sensors, and WFI of optic flow enables motion estimation robust by integrating wide range of optic flow. Since the system has several attractive features (small size, light weight, and low computation), it is applicable to an autonomous control system of micro air vehicles. However, due to some restrictions of real systems, WFI of optic flow theory should be applied while considering sensor arrangement for better estimation. In this paper, first an adequate number and adequate optical‐axes of image sensors are investigated. Then, a new estimation system combining a gyro sensor with WFI of optic flow is discussed by numerical simulations. Finally, the essential effect for the number of cameras are verified in experiments. [ABSTRACT FROM AUTHOR]

The understanding of the effectiveness of prescribed burning and mowing as restoration tools of degraded grasslands is important for dryland rangeland management. We examined the effects of spring prescribed burning or seasonal mowing treatments on the degraded vegetation dominated by an unpalatable subshrub, Artemisia adamsii, in grazed Mongolian steppe. Spring burning was conducted in 2013, and three types of mowing treatments (spring, previous summer, and previous summer and autumn) were conducted with varying seasons and frequency, respectively. Soil samples were collected immediately after the spring treatments. Four months after the spring treatments, total plant biomass, the numbers of flowering shoots and florets per shoot of A. adamsii were compared among the treatments. Plant biomass was divided into A. adamsii and herbaceous plants (forbs and graminoids) with different Raunkiaer life forms (chamaephytes, hemicryptophytes and geophytes). Soil properties and total plant biomass were not different among the treatments. For A. adamsii, the biomass and number of flowering shoots were decreased by spring burning and growing-season mowing, owing to the disappearance of woody-shoots of A. adamsii. On the other hand, spring mowing had less negative impact on the biomass of A. adamsii due to an increase of the newly-formed shoots. The biomass of perennial herbaceous-plants was not affected by spring burning, regardless of the life form, whereas that of the geophytic sedge Carex duriuscula increased in the summer-and-autumn mowing. Thus, spring burning and growing-season mowing have the potential to control undesirable subshrubs due to loss of the woody shoots, while spring mowing may not be recommended as a useful management tool in the Mongolian steppe. Our results emphasize that the introduction of these management tools for degraded-grassland restoration in dryland rangelands needs more long-term evaluation considering the relation with external factors such as climate variation and grazing impact. [ABSTRACT FROM AUTHOR]

Background: Microfossils of the genus Punctatus include developmental stages such as blastula, gastrula, and hatchlings, and represent the most complete developmental sequence of animals available from the earliest Cambrian. Despite the extremely well-preserved specimens, the evolutionary position of Punctatus has relied only on their conical remains and they have been tentatively assigned to cnidarians. We present a new interpretation of the Punctatus body plan based on the developmental reconstruction aided by recent advances in developmental biology. Results: Punctatus developed from a rather large egg, gastrulated in a mode of invagination from a coeloblastura, and then formed a mouth directly from the blastopore. Spiny benthic hatchlings were distinguishable from swimming or crawling ciliate larvae found in cnidarians and sponges. A mouth appeared at the perihatching embryonic stage and was renewed periodically during growth, and old mouths transformed into the body wall, thus elongating the body. Growing animals retained a small blind gut in a large body cavity without partitioning by septa and did not form tentacles, pedal discs or holdfasts externally. A growth center at the oral pole was sufficient for body patterning throughout life, and the body patterning did not show any bias from radial symmetry. Conclusions: Contrary to proposed cnidarian affinity, the Punctatus body plan has basic differences from that of cnidarians, especially concerning a spacious body cavity separating ectoderm from endoderm. The lack of many basic cnidarian characters in the body patterning of Punctatus leads us to consider its own taxonomic group, potentially outside of Cnidaria. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes in detail the external morphology of LB1/1, the nearly complete and only known cranium of Homo floresiensis. Comparisons were made with a large sample of early groups of the genus Homo to assess primitive, derived, and unique craniofacial traits of LB1 and discuss its evolution. Principal cranial shape differences between H. floresiensis and Homo sapiens are also explored metrically. The LB1 specimen exhibits a marked reductive trend in its facial skeleton, which is comparable to the H. sapiens condition and is probably associated with reduced masticatory stresses. However, LB1 is craniometrically different from H. sapiens showing an extremely small overall cranial size, and the combination of a primitive low and anteriorly narrow vault shape, a relatively prognathic face, a rounded oval foramen that is greatly separated anteriorly from the carotid canal/jugular foramen, and a unique, tall orbital shape. Whereas the neurocranium of LB1 is as small as that of some Homo habilis specimens, it exhibits laterally expanded parietals, a weak suprameatal crest, a moderately flexed occipital, a marked facial reduction, and many other derived features that characterize post-habilis Homo. Other craniofacial characteristics of LB1 include, for example, a relatively narrow frontal squama with flattened right and left sides, a marked frontal keel, posteriorly divergent temporal lines, a posteriorly flexed anteromedial corner of the mandibular fossa, a bulbous lateral end of the supraorbital torus, and a forward protruding maxillary body with a distinct infraorbital sulcus. LB1 is most similar to early Javanese Homo erectus from Sangiran and Trinil in these and other aspects. We conclude that the craniofacial morphology of LB1 is consistent with the hypothesis that H. floresiensis evolved from early Javanese H. erectus with dramatic island dwarfism. However, further field discoveries of early hominin skeletal remains from Flores and detailed analyses of the finds are needed to understand the evolutionary history of this endemic hominin species. [Copyright &y& Elsevier]

Abstract: Skull IX (Tjg-1993.05) was unearthed from the upper stratigraphic zone (Bapang-AG levels) of the hominin-bearing sequence in Sangiran. This remarkably complete cranial specimen of Homo erectus from the early Pleistocene of Java preserves substantial portions of the vault and face. However, the distortion present in the original reconstruction has hampered detailed documentation of its morphological characteristics. We here report a new reconstruction of Skull IX that successfully recovers the original morphology and significantly differs from previous reconstructions. Detailed morphological description and the results of initial comparative analyses based on this new reconstruction are provided. The endocranial volume of Skull IX was measured as 870 cc using micro-CT data. The neurocranium of Skull IX is slightly smaller than the so far recorded smallest cranium from this zone, suggesting this individual was female. In most, but not all, aspects of the cranial vault form, details of the external surface structures, and facial morphology, Skull IX exhibits numerous similarities to the other Bapang-AG H. erectus specimens, indicating that it belonged to the Bapang-AG H. erectus population. Drawing on the expanded fossil sample of this chronoregional H. erectus group, we discuss their evolutionary status, degree of sexual dimorphism, and facial morphological variation in Afro-Asian earlier Homo specimens. [Copyright &y& Elsevier]