Tracing the spatial imprint of Oldowan technological behaviors: A view from DS (Bed I, Olduvai Gorge, Tanzania).

DS (David's site) is one of the new archaeological sites documented in the same paleolandscape in which FLK 22 was deposited at about 1.85 Ma in Olduvai Gorge. Fieldwork in DS has unearthed the largest vertically-discrete archaeological horizon in the African Pleistocene, where a multi-cluster anthropogenic accumulation of fossil bones and stone tools has been identified. In this work we present the results of the techno-economic study of the lithic assemblage recovered from DS. We also explore the spatial magnitude of the technological behaviors documented at this spot using powerful spatial statistical tools to unravel correlations between the spatial distributional patterns of lithic categories. At DS, lavas and quartzite were involved in different technological processes. Volcanic materials, probably transported to this spot from a close source, were introduced in large numbers, including unmodified materials, and used in percussion activities and in a wide variety of reduction strategies. A number of volcanic products were subject to outward fluxes to other parts of the paleolandscape. In contrast, quartzite rocks were introduced in smaller numbers and might have been subject to a significantly more intense exploitation. The intra-site spatial analysis has shown that specialized areas cannot be identified, unmodified materials are not randomly distributed, percussion and knapping categories do not spatially overlap, while bipolar specimens show some sort of spatial correlation with percussion activities.

Theoretical tissue compartment inert gas pressures during a deep dive with and without deep decompression stops: a case analysis.

BACKGROUND: Deep decompression stops are increasingly common in recreational technical diving. Concerns exist that they shift decompression stress back into slower tissues. A diver recorded an exceptional exposure dive, with deeps stops, on a commercially available dive computer. MATERIAL AND METHODS: Using the R package SCUBA tissue inert gas pressures in 17 Bühlmann (ZH-L16A) compartments were estimated from the dive computer recorded profile. The RGBM dive plan generated by the diver's software was similarly interrogated, as was a third profile with reduced deep stops generated using the VPM-B/E model. RESULTS: In this dive the combination of 5 gas switches appeared to ameliorate the effect of deep stops from 76 m depth. CONCLUSIONS: A higher-than-anticipated inert gas content in a decompression mixture, coupled with climbing 200 stairs post-decompression, appear possible risk factors for decompression sickness. Nonetheless, the physiological effect of deep decompression stops during exceptional exposure, even when diving with gas switches, remains urgently to be determined to improve safe decompression following exceptional exposures. Until algorithms utilising deep decompression stops are validated with human data, dive profiles incorporating deep decompression stops should be considered experimental.

An analysis of the causes of compressed-gas diving fatalities in Australia from 1972-2005.

In order to investigate causative factors, root cause analysis (RCA) was applied to 351 Australian compressed-gas diving fatalities from 1972-2005. Each case was described by four sequential events (trigger, disabling agent, disabling injury, cause of death) that were assessed for frequency, trends, and dive and diver characteristics. The average age increased by 16 years, with women three years younger than men annually. For the entire 34-year period, the principal disabling injuries were asphyxia (49%), cerebral arterial gas embolism (CAGE; 25%), and cardiac (19%). There was evidence of a long-term decline in the rate of asphyxia and a long-term increase in CAGE and cardiac disabling injuries. Asphyxia was associated with rough water, buoyancy trouble, equipment trouble, and gas supply trouble. CAGE was associated with gas supply trouble and ascent trouble, while cardiac cases were associated with exertion, cardiovascular disease, and greater age. Exertion was more common in younger cardiac deaths than in older deaths. Asphyxia became less common with increasing age. Equipment-related problems were most common during the late 1980s and less so in 2005. Buoyancy-related deaths usually involved loss of buoyancy on the surface but decreased when buoyancy control devices were used. Countermeasures to reduce fatalities based on these observations will require validation by active surveillance.