New radiocarbon dates from the Bapot-1 site in Saipan and Neolithic dispersal by stratified diffusion

The colonisation of the Mariana Islands in Western Micronesia is likely to represent an early ocean dispersal of more than 2000 km. Establishing the date of human arrival in the archipelago is important for modelling Neolithic expansion in Island Southeast Asia and the Pacific, particularly the role of long-distance dispersals. This paper presents new ¹⁴C results and a ΔR estimate from the Bapot-1 site on Saipan Island, which indicate human arrival at ca. 3400-3200 cal. BP. Archaeological chronologies of long-distance dispersal to Western Micronesia and the Lapita expansion (Bismarcks to Samoa) show that the Neolithic dispersal rate was increasing during the period ca. 3400-2900 cal. BP. The range-versus-time relationship is similar to stratified diffusion whereby a period of relatively slow expansion is succeeded by long-distance movement. An increase in new colonies created by long-distance migrants results in accelerating range expansion

Colonisation of the Mariana Islands : affinities and differences with ISEA and Pacific cultures in the 1st millennium BC

This thesis examines prehistoric human dispersals from Island Southeast Asia (ISEA) to the Pacific at {u0303}4000-3000 BP by focusing on the colonisation of the Mariana Islands. The Marianas are located in the Pacific Ocean more than 2000 km from ISEA and the distant archipelago contains well-preserved archaeological sites dating to the colonisation era that result from one of the very first migrations into Remote Oceania. Ceramics, particularly the distribution of red-slipped and surface marked pottery, have played a central role in archaeological models used to track the Neolithic migration of Austronesian speaking people from Taiwan to eastern ISEA. In addition to movements in ISEA, Austronesian colonisation also spread to Western Micronesia and the Bismarck Archipelago, which was the origin point of Lapita settlers who colonised islands as far east as Samoa. The most common explanation for this extensive and rapid dispersal (that included the first settlement of Remote Oceanic islands) is that it was stimulated by the introduction and spread of an agricultural economy that created demographic growth and human expansion. In the last two decades, multi-disciplinary data from archaeology, historical linguistics and genetics has frequently been used to expand our knowledge of Neolithic movement in the Indo-Pacific. However, the excavation and analysis of the oldest archaeological sites is essential to produce a fine-grained picture of human mobility and migration in the region. The archaeological site of Unai Bapot on Saipan in the Marianas was excavated by the author and colleagues to obtain a large sample of early material culture to better understand Austronesian expansion and human colonisation. Analysis of the archaeological remains concentrated on the ceramics and establishing the age of the site's oldest cultural deposits with radiocarbon. Given the important role that prehistoric ceramics have in human dispersal models it is surprising that there have been few detailed attempts to examine pottery relationships within the broader region. A new archaeometric method involving the thin-section study of pot sherds impregnated with a fluorescence agent was used to establish whether Bapot pottery vessels were made by coiling or the paddle and anvil technique. The study of ceramic manufacturing technique was extended to four Neolithic assemblages spanning a large part of the Austronesian range (Taiwan, Philippines, Palau, Bismarck Archipelago). In addition, vessel attributes from nine Neolithic ceramic assemblages in ISEA were recorded (form/decorative technique/decorative design/temper). By comparing ceramic production and stylistic data it is possible to better articulate the similarities and differences among the ceramic assemblages and to test hypotheses about the affinities of Neolithic colonists with a possible migration source. Results do not offer strong support for the orthodox model of Austronesian expansion and significant inter-assemblage variation in the pottery assemblages studied indicate a more complicated and less unified movement than is often thought. While there is currently no ISEA assemblage that can be identified as the source of the oldest Bapot pottery there are regional similarities in manufacture/temper/vessel form/decoration that point to eastern Indonesia-northern New Guinea as a key area where human movement into Remote Oceania first began

Numerical simulation of growth of Escherichia coli in unsaturated porous media

A model for the aerobic and anaerobic growth of Escherichia coli (HB101 K12 pGLO) depending on the concentration of oxygen and DOC as substrate has been developed based on laboratory batch experiments. Using inverse modelling to obtain optimal sets of parameters, it could be shown that a model based on a modified double Contois kinetic can predict cell densities, organic carbon utilisation, oxygen transfer and utilisation rates for a large number of experiments under aerobic and anaerobic conditions with a single unique set of parameters. The model was extended to describe growth of E. coli in unsaturated porous media, combining diffusion, phase exchange and microbiological growth. Experiments in a Hele-Shaw cell, filled with quartz sand, were conducted to study bacterial growth in the capillary fringe above a saturated porous medium. Cell density profiles in the Hele-Shaw cell were predicted with the growth model and the parameters from the batch experiments without any further calibration. They showed a very good qualitative and quantitative agreement with cell densities determined from samples taken from the Hele-Shaw cell by re-suspension and subsequent counting. Thus it could be shown, that it is possible to successfully transfer growth parameters from batch experiments to porous media for both aerobic and anaerobic conditions.Comment: Minor changes in conclusions, results unchange

Accuracy of robotic patient positioners used in ion beam therapy

BACKGROUND: In this study we investigate the accuracy of industrial six axes robots employed for patient positioning at the Heidelberg Ion Beam Therapy Center. METHODS: In total 1018 patient setups were monitored with a laser tracker and subsequently analyzed. The measurements were performed in the two rooms with a fixed horizontal beam line. Both, the 3d translational errors and the rotational errors around the three table axes were determined. RESULTS: For the first room the 3d error was smaller than 0.72 mm in 95 percent of all setups. The standard deviation of the rotational errors was at most 0.026° for all axes. For the second room Siemens implemented an improved approach strategy to the final couch positions. The 95 percent quantile of the 3d error could in this room be reduced to 0.53 mm; the standard deviation of the rotational errors was also at most 0.026°. CONCLUSIONS: Robots are very flexible tools for patient positioning in six degrees of freedom. This study proved that the robots are able to achieve clinically acceptable accuracy in real patient setups, too

Basal roughness of the East Antarctic Ice Sheet in relation to flow speed and basal thermal state

Basal motion of ice sheets depends in part on the roughness and material properties of the subglacial bed and the occurrence of water. To date, basal motion represents one of the largest uncertainties in ice-flow models. It is that component of the total flow velocity that can change most rapidly and can, therefore, facilitate rapid variations in dynamic behaviour. In this study, we investigate the subglacial properties of the East Antarctic Ice Sheet by statistically analysing the roughness of the bed topography, inferred from radio-echo sounding measurements. We analyse two sets of roughness parameters, one derived in the spatial and the other in the spectral domain, with two roughness parameters each. This enables us to compare the suitability of the four roughness parameters to classify the subglacial landscapes below the ice sheet. We further investigate the relationship of the roughness parameters with observed surface flow velocity and modelled basal temperatures of the ice sheet. We find that one of the roughness parameters, the Hurst exponent derived in the spatial domain, coincides with the thermal condition at the base of the ice sheet for slow flow velocities and varies with flow velocity

Age stratigraphy in the East Antarctic Ice Sheet inferred from radio-echo sounding horizons

The East Antarctic Ice Sheet contains a wealth of information that can be extracted from its internal architecture such as distribution of age, past flow features, and surface and basal properties. Airborne radar surveys can sample this stratigraphic archive across broad areas. Here, we identify and trace key horizons across several radar surveys to obtain the stratigraphic information. We transfer the age–depth scales from ice cores to intersecting radar data. We then propagate these age scales across the ice sheet using the high fidelity continuity of the radar horizons. In Dronning Maud Land, including Dome Fuji, we mapped isochrones with ages of 38 and 74 ka. In the central region of East Antarctica around Dome Concordia, Vostok and Dome Argus, we use isochrone ages of 38, 48, 90 and 161 ka. Taking together both regions, we provide isochrone depths traced along a combined profile length of more than 40 000 km and discuss uncertainties of the obtained stratigraphy, as well as factors important to consider for further expansion. This data set is the most extensive distribution of internal horizons in East Antarctica to date. The isochrone depths presented in this study are available on PANGAEA (https://doi.org/10.1594/PANGAEA.895528; Winter et al., 2018)

Forgotten news: shellfish isotopic insight into changing sea-level and associated impact on the first settlers of the Mariana Archipelago

The colonisation of the Pacific is an important chapter in human dispersal for which chronological control is primarily provided by radiocarbon (14C) dates. In this context, the ability to reliably date shellfish is important because alternative dating materials, such as charcoal and bone, are typically highly degraded. However, the interpretation of shell 14C results is not always black and white because 14C is not evenly distributed throughout the marine environment, with estuarine taxa more likely to incorporate terrestrial sources of carbon. Regions where water has percolated through limestone bedrock provide an additional problem since ancient carbon is introduced into the estuarine waters. This “hardwater” has been put forward to explain old 3500 cal. BP results from culturally significant shells recovered from the site of Unai Bapot (Bapot-1) on the island of Saipan (Petchey et al. 2017). While arguments for (Carson and Hung 2017) and against (Rieth and Athens 2017) early settlement dates remain polarised, little attention has been given to the idea of change in the marine 14C reservoir over time, or to possible species-specific offsets in shell 14C. In this paper, we further develop a tri-isotope approach using 14C, δ13C, δ18O to identify carbon source. To investigate which shellfish are more prone to erroneous ages we have selected shell taxa that cover a range of nearshore environments commonly found in Pacific archaeological sites; including Anadara antiquata, Gafrarium pectinatum (both estuarine) and Tridacna (marine/reef). To test the possibility of change over time we extend the dating of the site beyond the earliest occupation layers to deposits considered to post-date the end of the mid-Holocene drawdown in sea-level

Surface accumulation in Northern Central Greenland during the last 300 years

The internal stratigraphy of snow and ice as imaged by ground-penetrating radar may serve as a source of information on past accumulation. This study presents results from two ground-based radar surveys conducted in Greenland in 2007 and 2015, respectively. The first survey was conducted during the traverse from the ice-core station NGRIP (North Greenland Ice Core Project) to the ice-core station NEEM (North Greenland Eemian Ice Drilling). The second survey was carried out during the traverse from NEEM to the ice-core station EGRIP (East Greenland Ice Core Project) and then onwards to Summit Station. The total length of the radar profiles is 1427 km. From the radar data, we retrieve the large-scale spatial variation of the accumulation rates in the interior of the ice sheet. The accumulation rates range from 0.11 to 0.26 m a−1 ice equivalent with the lowest values found in the northeastern sector towards EGRIP. We find no evidence of temporal or spatial changes in accumulation rates when comparing the 150-year average accumulation rates with the 321-year average accumulation rates. Comparisons with regional climate models reveal that the models underestimate accumulation rates by up to 35% in northeastern Greenland. Our results serve as a robust baseline to detect present changes in either surface accumulation rates or patterns

Accumulation rates from 38 ka and 160 ka radio-echo sounding horizons in East Antarctica

The internal layering architecture of ice sheets, as detected with radio-echo sounding (RES), contains clues to past ice-flow dynamics and mass balance and supplies flow models with starting and boundary conditions. In comparison to the Greenland Ice Sheet, the coverage of the East Antarctic Ice Sheet with information on internal ice structure is still sparse. This hampers the constraining or initialization of ice-flow models with geometry and surface mass balance data inadequate resolution.We traced two RES horizons, 38 ka and 160 ka, over great parts and in the most remote areas of the East Antarctic Ice Sheet.We dated the horizons at the EPICA Dome C Ice Core and followed them along RES lines of the Alfred Wegener Institute to Vostok and Dome A. There, they could be connected to the RES grid, covering the Gamburtsev mountains, that was collected as part ofthe AGAP (Antarctica’s Gamburtsev Province) project, and continued to South Pole. From this widespread age-depth distribution we reconstruct mean accumulation rates and analyze spatial variations in surface mass balance, as well as differences between the two time periods