Should archaeologists care about 14C inter-comparisons? Why? A summary report on SIRI

Radiocarbon (14C) dating is used widely in many projects as a basis for the creation and testing of chronological constructs. 14C measurements are by their nature complex and the degree of sample pretreatment varies considerably depending on the material. Within the United Kingdom and Europe, there are a number of well-established laboratories and increasingly, archaeologists are not just commissioning new dates, but also using statistical modelling of assemblages of dates, perhaps measured in different laboratories, to provide formal date estimates for their sites. The issue of comparability of measurements (and thus bias, accuracy and precision of measurement) from the diverse laboratories is one which has been the focus of some attention both within the 14C community and the wider user communities for some time. As a result of this but also as part of laboratory benchmarking and quality assurance, the 14C community has undertaken a wide-scale, far-reaching, and evolving program of intercomparisons, to the benefit of laboratories and users alike. This paper summarizes the most recent exercise, the Sixth International Radiocarbon Intercomparison (SIRI)

The fifth international radiocarbon intercomparison (VIRI): An assessment of laboratory performance in stage 3

Proficiency testing is a widely used, international procedure common within the analytical chemistry community. A proficiency trial (which VIRI is) often follows a standard protocol, including analysis that is typically based on zscores, with one key quantity, σp. From a laboratory intercomparison (sometimes called a proficiency trial), we hope to gain an assessment of accuracy (in this case, from dendro-dated samples), laboratory precision (from any duplicate samples), and generally, an overall measure of performance, including measurement variability and hence realistic estimates of uncertainty. In addition, given our stated aim of creating an archive of reference materials, we also gain a determination of consensus values for new reference materials. VIRI samples have been chosen to deliver these objectives and the sample ages included in the different stages, by design, spanned modern to background. With regard to pretreatment, some samples required intensive pretreatment (e.g. bone), while others required none (e.g. cellulose and humic acid). Sample size was not optimized, and indeed some samples were provided solely for accelerator mass spectrometry (AMS) measurement. In this sense, VIRI presented a more challenging exercise than previous intercomparisons, since by its design in stages, one can explore improvements (or deteriorations) over time in laboratory performance. At each stage, more than 50 laboratories have participated, with an increasing demographic shift towards more AMS and fewer radiometric laboratories

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

Why do we need 14C inter-comparisons?: The Glasgow 14C inter-comparison series, a reflection over 30 years

Radiocarbon measurement is a well-established, routinely used, yet complex series of inter-linked procedures. The degree of sample pre-treatment varies considerably depending on the material, the methods of processing pre-treated material vary across laboratories and the detection of 14C at low levels remains challenging. As in any complex measurement process, the questions of quality assurance and quality control become paramount, both internally, i.e. within a laboratory and externally, across laboratories. The issue of comparability of measurements (and thus bias, accuracy and precision of measurement) from the diverse laboratories is one that has been the focus of considerable attention for some time, both within the 14C community and the wider user communities. In the early years of the technique when there was only a small number of laboratories in existence, inter-comparisons would function on an ad hoc basis, usually involving small numbers of laboratories (e.g.Otlet et al, 1980). However, as more laboratories were set-up and the detection methods were further developed (e.g. new AMS facilities), the need for more systematic work was recognised. The international efforts to create a global calibration curve also requires the use of data generated by different laboratories at different times, so that evidence of laboratory offsets is needed to inform curve formation. As a result of these factors, but also as part of general good laboratory practice, including laboratory benchmarking and quality assurance, the 14C community has undertaken a wide-scale, far-reaching and evolving programme of global inter-comparisons, to the benefit of laboratories and users alike. This paper looks at some of that history and considers what has been achieved in the past 30 years

Is there a fifth international radiocarbon intercomparison (VIRI)?

The issue of comparability of measurements (and thus bias, accuracy, and precision of measurement) from diverse laboratories is one which has been the focus of some attention both within the radiocarbon community and the wider user communities. As a result, the C-14 community has undertaken a widescale, far-reaching, and evolving program of inter- comparisons, to the benefit of laboratories and users alike. The benefit to the users is, however, indirect, since the C-14 intercomparisons have not been used to generate "league tables" of performance, but rather to allow individual laboratories to check procedures and modify them as required. The historical progression of C-14 laboratory intercomparisons from the Third (TIRI, completed in 1995, Gulliksen and Scott 1995) and Fourth (FIRI, completed in 2000, Scott 2003; Boaretto et al. 2000; Bryant et al. 2002) suggests that a Fifth (VIRI) should also be expected. We describe the plans for VIRI

Markov Chains Derived From Lagrangian Mechanical Systems

The theory of Markov chains with countable state spaces is a greatly developed and successful area of probability theory and statistics. There is much interest in continuing to develop the theory of Markov chains beyond countable state spaces. One needs good and well motivated model systems in this effort. In this thesis, we propose to produce such systems by introducing randomness into familiar deterministic systems so that we can draw upon the existing: deterministic) results to aid the analysis of our Markov chains. We will focus most heavily on models drawn from Lagrangian mechanical systems with collisions: billiards)

Teachers\u27 Perceptions and Experiences Consulting with School Counselors: A Qualitative Study

School counselor–teacher consultation is an efficient strategy for school counselors to indirectly serve students on their caseload. Teachers\u27 perceptions are crucial in examining this consultation process. This qualitative study examined elementary school teachers\u27 perceptions and experiences of school counselor–teacher consultation. The researchers identified three themes: (a) school counselors prioritizing relationships, (b) school counselors taking initiative, and (c) school counselors\u27 specialization. The researchers discuss implications for school counseling practice, including strategies for facilitating consultation with teachers

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

The quest for loyalty: creating value through partnership

In his bestselling book, The Loyalty Effect, Fred Reichheld made the definitive case for the economic value of loyalty in business. Now he deepens and enriches that picture with a collection of 14 articles and interviews on the same subject from the Harvard Business Review. Here, some of the world\u27s preeminent business leaders and thinkers present their original views on various key aspects of customer, employee, and investor loyalty and on the assumptions and strategies that underlie loyalty-based success. This collection of articles and interviews from the "Harvard Business Review", should help business leaders understand, integrate and manage the various dimensions of loyalty in their companies. The book also features contributions from authors such as Hamel, Prahalad, Porter, Handy and Drucker. It demonstrates a need for understanding loyalty from customers, investors, employees and strategists