North Atlantic marine ¹⁴C reservoir effects: implications for late-Holocene chronological studies

We investigated surface ocean–atmosphere 14C offsets for the later Holocene at eight locations in the eastern North Atlantic. This resulted in 11 new ΔR assessments for the west coast of Ireland, the Outer Hebrides, the north coast of the Scottish mainland, the Orkney Isles and the Shetland Isles over the period 1300–500 BP. Assessments were made using a robust Multiple Paired Sample (MPS) approach, which is designed to maximize the accuracy of ΔR determinations. Assessments are placed in context with other available data to enable reconstruction of a realistic picture of surface ocean 14C activity over the Holocene period within the North Atlantic region

Marine radiocarbon reservoir effect of coastal waters off Cape Verde archipelago

Quantification of the marine radiocarbon reservoir effect (Delta R) is essential in order to calibrate conventional C-14 dates from marine shell samples with reliability. Delta R also provides information concerning the intensity of coastal upwelling in marine regions influenced by this phenomenon. C-14 ages of closely associated marine samples (mollusk shells) and terrestrial samples (goat bones) from Sao Vicente Island, Cape Verde Archipelago, permitted the first calculation of the marine C-14 reservoir effect in this region. A Delta R weighted mean value of 70 +/- 70 C-14 yr was obtained. This value is in accordance with the previously published oceanographic conditions of the region indicating the existence of a seasonal active upwelling regime

FARM COMPUTER ADOPTION IN THE GREAT PLAINS

Computers change rapidly, yet the last survey on computer use in agriculture was in 1991. We surveyed Great Plains producers in 1995 and used logit analysis to characterize adopters and non-adopters. About 37% of these producers use computers which is consistent with the general population. We confirmed previous surveys emphasizing the importance of education, age/experience, and other farm characteristics on adoption. However, we also found that education and experience may no longer be a significant influence. Future research and education could focus on when and where computers are most needed, and therefore when adoption is most appropriate.adoption, agriculture, computers, farmers, Great Plains, logit, Farm Management,

The North Atlantic marine reservoir effect in the early Holocene: implications for defining and understanding MRE values

The marine reservoir effect (MRE) is a <sup>14</sup>C age offset between the oceanic and atmospheric carbon reservoirs. The MRE is neither spatially nor temporally constant and values may deviate significantly from the global model average provided by the Marine04 curve. Such a deviation is calculated as a ©R value and modern (pre-bomb) values show considerable spatial variations. There is also considerable evidence for temporal variability linked to paleoenvironmental changes identified in paleoclimatic proxy records. Seven new ©R values are presented for the North Atlantic, relating to the period c. 8430 3890 cal. BP (c. 6480 1940 BC). These were obtained from <sup>14</sup>C analysis of multiple samples of terrestrial and marine material derived from seven individual archaeological deposits from Mainland Scotland, the Outer Hebrides and the Orkney Isles. The ©R values vary between 143 ± 20 14C yr and ‑100 ± 15 <sup>14</sup>C yr with the positive values all occurring in the earlier period (8430 5060 cal. BP), and the negative values all coming from later deposits (4820 3890 cal. BP). The nature of MRE values and the potential for spatial and temporal variation in values is the subject of current research interest and these data are placed in the context of (i) other estimates for UK coastal waters and (ii) important questions concerning current approaches to quantifying the MRE

Spatial variation in the MRE throughout the Scottish Post-Roman to late Medieval period: North Sea values (500-1350 BP)

The marine radiocarbon reservoir effect (MRE) occurs as a spatially and temporally dependent variable owing to localized changes in oceanic water composition. This study investigates ΔR values (deviations from the global average MRE whose ΔR = 0) during the period 500–1350 BP for the east coast of Scotland, where a complex estuarine system exists that drains into the semi-enclosed North Sea basin. Due to the availability of suitable archaeological samples, the data set has a distinct Medieval focus that spans the area from Aberdeen in the north to East Lothian in the south. Many of the ΔR values are not significantly different from 0 (the global average), but there are occasional excursions to negative values (max –172 ± 20) indicating the presence of younger water. These values show greater variability compared to other published data for this general region, suggesting that considerable care must be taken when dating marine derived samples from archaeological sites on the east coast of Scotland

Influence of mollusk species on marine DELTA R determinations

Radiocarbon ages were measured on replicate samples of burnt grain and 5 mollusk species collected from a single sealed layer at an archaeological site (Hornish Point) on the west coast of South Uist, Scotland. The aim was to examine the impact of using different mollusk species on ΔR determinations that are calculated using the paired terrestrial/marine sample approach. The mollusk species examined inhabit a range of environments and utilize a variety of food sources within the intertidal zone. Several authors have suggested that these factors may be responsible for observed variations in the 14C activity of mollusk shells that were contemporaneous in a single location. This study found no significant variation in the <sup>14</sup>C ages of the mollusk species, and consequently, no significant variation in calculated values of ΔR. The implication is that in an area where there are no carboniferous rocks or significant local inputs of freshwater to the surface ocean, any of a range of marine mollusk species can be used in combination with short-lived terrestrial material from the same secure archaeological context to accurately determine a ΔR value for a particular geographic location and period in time

Induction and subversion of human protective immunity: contrasting influenza and respiratory syncytial virus

Respiratory syncytial virus (RSV) and influenza are among the most important causes of severe respiratory disease worldwide. Despite the clinical need, barriers to developing reliably effective vaccines against these viruses have remained firmly in place for decades. Overcoming these hurdles requires better understanding of human immunity and the strategies by which these pathogens evade it. Although superficially similar, the virology and host response to RSV and influenza are strikingly distinct. Influenza induces robust strain-specific immunity following natural infection, although protection by current vaccines is short-lived. In contrast, even strain-specific protection is incomplete after RSV and there are currently no licensed RSV vaccines. Although animal models have been critical for developing a fundamental understanding of antiviral immunity, extrapolating to human disease has been problematic. It is only with recent translational advances (such as controlled human infection models and high-dimensional technologies) that the mechanisms responsible for differences in protection against RSV compared to influenza have begun to be elucidated in the human context. Influenza infection elicits high-affinity IgA in the respiratory tract and virus-specific IgG, which correlates with protection. Long-lived influenza-specific T cells have also been shown to ameliorate disease. This robust immunity promotes rapid emergence of antigenic variants leading to immune escape. RSV differs markedly, as reinfection with similar strains occurs despite natural infection inducing high levels of antibody against conserved antigens. The immunomodulatory mechanisms of RSV are thus highly effective in inhibiting long-term protection, with disturbance of type I interferon signaling, antigen presentation and chemokine-induced inflammation possibly all contributing. These lead to widespread effects on adaptive immunity with impaired B cell memory and reduced T cell generation and functionality. Here, we discuss the differences in clinical outcome and immune response following influenza and RSV. Specifically, we focus on differences in their recognition by innate immunity; the strategies used by each virus to evade these early immune responses; and effects across the innate-adaptive interface that may prevent long-lived memory generation. Thus, by comparing these globally important pathogens, we highlight mechanisms by which optimal antiviral immunity may be better induced and discuss the potential for these insights to inform novel vaccines

Reservoirs and radiocarbon: ¹⁴C dating problems in Myvatnssveit, Northern Iceland

This paper examines 2 potential sources of the radiocarbon offset between human and terrestrial mammal (horse) bones recovered from Norse (~AD 870–1000) pagan graves in Mývatnssveit, north Iceland. These are the marine and freshwater 14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine 14C reservoir effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusk shell) at 2 archaeological sites in Mývatnssveit and 1 site on the north Icelandic coast. These produced 3 new ΔR values for the north coast of Iceland, indicating a ΔR of 106 ± 10 14C yr at AD 868–985, and of 144 ± 28 14C yr at AD 1280–1400. These values are statistically comparable and give an overall weighted mean ΔR of 111 ± 10 14C yr. The freshwater reservoir effect was similarly quantified using freshwater fish bones from a site in Mývatnssveit. These show an offset of between 1285 and 1830 14C yr, where the fish are depleted in 14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2 into the groundwater and subsequently into Lake Mývatn. We conclude the following: i) some of the Norse inhabitants of Mývatnssveit incorporated non-terrestrial resources into their diet that may be identified from the stable isotope composition of their bone collagen; ii) the MRE off the north Icelandic coast during the Norse period fits a spatial gradient of wider North Atlantic MRE values with increasing values to the northwest; and iii) it is important to consider the effect that geothermal activity could have on the 14C activity of samples influenced by groundwater at Icelandic archaeological sites

Assessment of oxygen plasma ashing as a pre-treatment for radiocarbon dating

This study investigates the potential of low-temperature oxygen plasma ashing as a technique for decontaminating charcoal and wood samples prior to radiocarbon dating. Plasma ashing is demonstrated to be rapid, controllable and surface-specific, and clear differences are identified in the rate of ashing in different organic materials. However, the ability of plasma ashing to selectively remove these different components is limited in heterogeneous sample matrices. This is because oxidation is confined to the immediate sample surface. Comparison of radiocarbon dates obtained from identical aliquots of contaminated ancient charcoal pre-treated by acid-base-acid (ABA), acid-base-oxidation-stepped combustion (ABOx-SC) and plasma ashing suggests that the technique performs as well as the ABA pre-treatment but does not remove as much contamination as the ABOx-SC technique. Plasma-ashing may be particularly useful in cases where sample size is limiting