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Each of the laboratory intercomparisons (from ICS onwards) has included wood samples, many of them dendrochronologically dated. In the early years, as a result of the majority of laboratories being radiometric, these samples were typically blocks of 20–40 rings, but more recently (SIRI), they have been single ring samples. The sample ages have spanned background through to modern. In some intercomparisons, we have examined different wood pretreatment effects, in others the focus has been on background samples. In this paper, we illustrate what we have learned from these extensive intercomparisons involving wood samples and how the results contribute to the global IntCal effort.
Expression of estrus (EST) near the time of fixed-time artificial insemination (FTAI) increases pregnancy success in beef females. This outcome has been associated with improved pregnancy establishment and maintenance, although research is still warranted to validate this theory. Hence, this experiment compared ovarian, uterine and conceptus factors associated with pregnancy establishment in Bos indicus beef cows according to estrous expression during a FTAI protocol. One hundred lactating multiparous Nelore cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device on day −11, a 12.5 mg injection of prostaglandin F2α on day −4, P4 device removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of equine chorionic gonadotropin on day −2, and FTAI on day 0. An estrous detection patch was attached to the tailhead of each cow on day −2, and estrous expression was defined as removal of >50% of the rub-off coating from the patch at FTAI. Overall, 39 cows expressed EST, 55 did not express EST (NOEST), and six cows lost their patch and were discarded from the experiment. Ovarian ultrasonography was performed at FTAI, and on days 7 and 15 of the experiment. Blood samples were also collected on days 7 and 15. Only cows without a corpus luteum (CL) on day 0, and with a CL on days 7 and 15 remained in the experiment (EST, n=36; NOEST, n=48). On day 15, cows were randomly selected within each group (EST, n=29; NOEST, n=30) for conceptus collection via transcervical flushing, followed by endometrial biopsy in the uterine horn ipsilateral to the CL. Within cows not assigned to conceptus collection, blood samples were collected for whole blood RNA extraction (day 20) and pregnancy status was verified by transrectal ultrasonography (day 30). Diameter of dominant follicle on day 0 and plasma P4 concentrations on day 7 were greater (P⩽0.02) in EST v. NOEST cows. Conceptus length and messenger RNA (mRNA) expression of prostaglandin E synthase and interferon-tau were greater (P⩽0.04) in EST v. NOEST cows. Moreover, EST cows diagnosed as pregnant on day 30 had greater (P<0.01) blood mRNA expression of myxovirus resistance 2 on day 20 compared with NOEST. In summary, estrous expression near the time of FTAI enhanced pregnancy establishment factors in B. indicus cows, including conceptus development and mRNA expression of interferon-tau.
OBJECTIVES/SPECIFIC AIMS: Glaucoma is a leading cause of irreversible blindness worldwide; in the United States alone, over 2.7 million individuals are affected. Various risk factors for glaucoma are known and include age, race/ethnicity, genetics, and ocular measures. Despite numerous studies, molecular and environmental factors that contribute to glaucoma remain elusive. Our objective was to conduct a genome-wide association for glaucoma among black and white HRS respondents, and to determine the feasibility for future analyses examining shared genetic markers between glaucoma and other comorbidities, behaviors, and environmental risk factors. METHODS/STUDY POPULATION: The University of Michigan Health and Retirement Study (HRS) is a longitudinal survey of a representative sample of Americans over the age of 50. Supported by the National Institute on Aging and the Social Security Administration, the HRS is designed to provide reliable data on the decisions, choices, and behaviors of people as they age and respond to changes in public policy, the economy, and health. The study obtains information every two years about income and wealth, health and use of health services, work and retirement, and family connections. Through its unique and in-depth interviews, the HRS provides an invaluable and growing body of multidisciplinary data that researchers can use to address important questions about the challenges and opportunities of aging. Because of its innovation and importance, the HRS has become the model and hub for a growing network of harmonized longitudinal aging studies around the world. Saliva was collected on half of the HRS sample each wave starting in 2006 and respondents were genotyped on the Illumina Human Omni2.5-Quad (Omni2.5) BeadChip at the NIH Center for Inherited Disease Research. We accessed survey results to evaluate prevalence of glaucoma in this dataset and performed a genome-wide association study (GWAS) adjusting for age, sex, and significant Principal Components and stratifying by self-reported race (White / Black). RESULTS/ANTICIPATED RESULTS: Of 8179 respondents passing quality filters, 6409 (78.40%) were white and 985 (12.05%) were black. Self-reported glaucoma prevalence was 7.85% and 16.34% in white and black respondents, respectively. White respondents had a mean age of 76.97 (SD 7.53) and were 57.25% female. Black respondents had a similar mean age of 74.96 (SD 7.27) and were 62.54% female. More than 87% of both groups were assessed in 2012. Preliminary GWAS analyses did not replicate known glaucoma loci and no variants attained genome-wide significance. A suggestive variant (p<1e-05) in the black population was within 10kb of a known locus, rs1196998. Future analyses will evaluate genetic association with combinations of glaucoma and comorbidities. DISCUSSION/SIGNIFICANCE OF IMPACT: Glaucoma risk is higher in minority groups than in whites, and the majority of reported genetic studies of glaucoma have been performed in individuals of European descent. It is imperative to better understand the role of genetics, environment, and health behavior in glaucoma risk. Further, understanding common mechanisms underlying diseases that co-occur with glaucoma could illuminate novel disease mechanisms that can be targeted for early intervention and/or treatment.
Many Spanish chroniclers detail violent cultural practices of the indigenous populations they encountered in the Isthmo-Colombian Area; however, lack of physical evidence of interpersonal violence from archaeological contexts has made uncertain the veracity of these claims. At the precolumbian site of Playa Venado in Panama, these accounts of violent mortuary rituals may have influenced the interpretation of the burials encountered in excavations, leading to claims of mutilations and sacrifice, with little or no supporting evidence. This paper considers the physical evidence for interpersonal violence and sacrificial death at Playa Venado based on the burial positioning, demographic composition, and trauma present on the human remains recovered from the site. Analysis of field notes, excavation photos, and the 77 individuals available for study from the site yielded no evidence of perimortem trauma nor abnormal body positioning unexplained by taphonomy. The demography at the site tracked with normal patterns of natural age-at-death at the non-elite site of Cerro Juan Díaz rather than the abnormal patterns seen at the large ceremonial sites of Sitio Conte and El Caño. Therefore, we propose an alternative interpretation of the site as a non-elite cemetery containing evidence of re-use and secondary burial practices associated with ancestor veneration rituals.
To evaluate the effects of a polyunsaturated fatty acids (PUFA) supplement on reproductive parameters of suckled beef cows, two experiments were conducted. In Experiment (Exp.) 1, 60 primiparous cows were randomly assigned to one of two treatments: CTRL – 1.36 kg/day of corn gluten feed (CGF) and MEGR – 1.36 kg/day of CGF and 0.23 kg/day of calcium salts of soybean oil. Supplementation occurred from 30 days before fixed-time artificial insemination (TAI) until 7 days post-TAI. The expression of interferon-stimulated genes (ISG) was measured on days 18 and 21. Pregnancy rates were diagnosed on days 30 and 100. Treatment altered plasma fatty acid profile (P<0.05), however, did not change cow BW (P=0.52) or body condition score (BCS) (P=0.52). Treatment did not alter (P=0.12) pregnancy rates to TAI or final pregnancy rates (P=0.56). Treatments did not impact messenger RNA (mRNA) expression of the ISG OAS1 or MX2 on days 18 (P=0.67; P=0.96, respectively) or 21 (P=0.72; P=0.17, respectively). Length of gestation was greater (P=0.02) for MEGR, however, treatments did not alter calf birth weight (P=0.20). In Exp. two, 66 multiparous cows were assigned to one of two treatments: MEG – 0.65 kg/day of CGF+0.23 kg/day of calcium salts of palm oil and MEGR – 0.65 kg/day of CGF+0.23 kg/day of Ca salts of soybean oil. Cows were supplemented from 30 days prepartum to 30 days postpartum. On day 35 after TAI, pregnancy status, embryo crown-to-rump length (CRL), and plasma concentrations of pregnancy-specific protein-B (PSPB) were evaluated. Treatment altered plasma fatty acid profile (P<0.05). In addition, cows from the MEG treatment had greater BW (P<0.01) and BCS (P<0.01) than those in the MEGR treatment, as well as heavier calves at weaning (P=0.03). Treatment did not affect resumption of estrous cycle (P=0.29). There were no differences in pregnancy rates to TAI (P=0.87) or final pregnancy rates (P=0.29). No differences between treatments were detected on CRL (P=0.24) and plasma concentrations of PSPB (P=0.46). Birth weight (P=0.12) and calving distribution (P=0.52) were not altered. We concluded that PUFA supplementation altered plasma fatty acid profile, however, did not impact the remaining reproductive parameters evaluated.
Objectives: To evaluate prospective and retrospective memory abilities in Operation Enduring Freedom (OEF), Operation Iraqi Freedom (OIF), and Operation New Dawn (OND) Veterans with and without a self-reported history of blast-related mild traumatic brain injury (mTBI). Methods: Sixty-one OEF/OIF/OND Veterans, including Veterans with a self-reported history of blast-related mTBI (mTBI group; n=42) and Veterans without a self-reported history of TBI (control group; n=19) completed the Memory for Intentions Test, a measure of prospective memory (PM), and two measures of retrospective memory (RM), the California Verbal Learning Test-II and the Brief Visuospatial Memory Test-Revised. Results: Veterans in the mTBI group exhibited significantly lower PM performance than the control group, but the groups did not differ in their performance on RM measures. Further analysis revealed that Veterans in the mTBI group with current PTSD (mTBI/PTSD+) demonstrated significantly lower performance on the PM measure than Veterans in the control group. PM performance by Veterans in the mTBI group without current PTSD (mTBI/PTSD-) was intermediate between the mTBI/PTSD+ and control groups, and results for the mTBI/PTSD- group were not significantly different from either of the other two groups. Conclusions: Results suggest that PM performance may be a sensitive marker of cognitive dysfunction among OEF/OIF/OND Veterans with a history of self-reported blast-related mTBI and comorbid PTSD. Reduced PM may account, in part, for complaints of cognitive difficulties in this Veteran cohort, even years post-injury. (JINS, 2018, 24, 324–334)
This experiment evaluated the impacts of supplementing a yeast-derived product (Celmanax; Church & Dwight Co., Inc., Princeton, NJ, USA) on productive and health responses of beef steers, and was divided into a preconditioning (days 4 to 30) and feedlot receiving phase (days 31 to 69). In all, 84 Angus × Hereford steers were weaned on day 0 (BW=245±2 kg; age=186±2 days), and maintained in a single group from days 0 to 3. On day 4, steers were allocated according to weaning BW and age to a 21-pen drylot (4 steers/pen). Pens were randomly assigned to (n=7 pens/treatment): (1) no Celmanax supplementation during the study, (2) Celmanax supplementation (14 g/steer daily; as-fed) from days 14 to 69 or (3) Celmanax supplementation (14 g/steer daily; as-fed) from days 31 to 69. Steers had free-choice access to grass-alfalfa hay, and were also offered a corn-based concentrate beginning on day 14. Celmanax was mixed daily with the concentrate. On day 30, steers were road-transported for 1500 km (24 h). On day 31, steers returned to their original pens for the 38-day feedlot receiving. Shrunk BW was recorded on days 4, 31 and 70. Feed intake was evaluated daily (days 14 to 69). Steers were observed daily (days 4 to 69) for bovine respiratory disease (BRD) signs. Blood samples were collected on days 14, 30, 31, 33, 35, 40, 45, 54 and 69, and analyzed for plasma cortisol, haptoglobin, IGF-I, and serum fatty acids. Preconditioning results were analyzed by comparing pens that received (CELM) or not (CONPC) Celmanax during the preconditioning phase. Feedlot receiving results were analyzed by comparing pens that received Celmanax from days 14 to 69 (CELPREC), days 31 to 69 (CELRECV) or no Celmanax supplementation (CON). During preconditioning, BRD incidence was less (P=0.03) in CELM v. CONPC. During feedlot receiving, average daily gain (ADG) (P=0.07) and feed efficiency (P=0.08) tended to be greater in CELPREC and CELRECV v. CON, whereas dry matter intake was similar (P⩾0.29) among treatments. No other treatment effects were detected (P⩾0.20). Collectively, Celmanax supplementation reduced BRD incidence during the 30-day preconditioning. Moreover, supplementing Celmanax tended to improve ADG and feed efficiency during the 38-day feedlot receiving, independently of whether supplementation began during preconditioning or after feedlot entry. These results suggest that Celmanax supplementation benefits preconditioning health and feedlot receiving performance in beef cattle.
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
Collagen associated with bone samples is frequently used for radiocarbon (14C) dating of bones recovered from archaeological sites. However, submersion and exposure to moisture favors the degradation of collagen, which leads to difficulty in reliably dating bones from tropical, humid, or previously submerged archaeological sites. In this paper, we characterized the preservation state of a series of bones, through parameters such as %C, %N, C/N ratio, and collagen recovery. We performed 14C analyses of three collagen fractions obtained through the pretreatment steps (total, ultrafiltered, and insoluble collagen) in order to link the preservation state and the reproducibility of 14C values obtained from the three fractions. Collagen ultrafiltration resulted in a decrease of C/N ratio, although collagen yield was reduced. When two or three collagen fractions were obtained, ages were reproducible and consistent with expected values, according to archaeological or hydrogeological criteria. The pretreatment steps were monitored by infrared spectroscopy in order to analyze the collagen fractions at the molecular level. The presence of collagen in the total and insoluble fractions was confirmed. Since many of the Mexican samples had poor ultrafiltered collagen yield (<3%) or nonexistent yield, our results show that if additional contextual information is carefully considered, the remnant collagen in the total and insoluble fraction can be dated, especially from sites where no other datable fraction exists.
We explore the properties of sound and human sound recognition as a means to enhance and accelerate visual-only data analysis methods. The aim of this work is to enable and improve the analysis of large data sets, data requiring rapid analysis, multi-dimensional data, and signal detection in data with low signal-to-noise ratio. We present a prototype tool, StarSound, to sonify data such as astronomical transient light curves, spectra, and power spectra. Stereophonic sound is used to ‘visualise’ and localise the data under examination, and 3-D sound is discussed in conjunction with virtual reality technology, as a means to enhance analysis efficiency and efficacy, including rapid data assessment and training machine learning software. In addition, we explore the use of higher-order harmonics as a means to examine simultaneously multi-dimensional data sets. Such an approach can allow the data to be interpreted in a holistic manner and facilitates the discovery of previously unseen connections and relationships. Furthermore, we exploit the capability of the human brain for selective or focused hearing that enables the identification of desired signals in noisy data, or amidst similar or more significant signals. Finally, we provide research examples that benefit directly from data sonification. The work presented here aims to help tackle the challenges of the upcoming era of Big Data and help optimise, speed up and expand aspects of data analysis requiring human interaction.
Archaeological fieldwork preceding housing development revealed a Mesolithic site in a primary context. A central hearth was evident from a cluster of calcined flint and bone, the latter producing a modelled date for the start of occupation at 8220–7840 cal bc and ending at 7960–7530 cal bc (95% probability). The principal activity was the knapping of bladelets, the blanks for microlith production. Impact-damaged microliths indicated the re-tooling of hunting weaponry, while microwear analysis of other tools demonstrated hide working and butchery activity at the site. The lithics can be classified as a Honey Hill assemblage type on the basis of distinctive leaf-shaped microlithic points with inverse basal retouch.
Such assemblages have a known concentration in central England and are thought to be temporally intermediate between the conventional British Early and Late Mesolithic periods. The lithic assemblage is compared to other Honey Hill type and related Horsham type assemblages from south-eastern England. Both assemblage types are termed Middle Mesolithic and may be seen as part of wider developments in the late Preboreal and Boreal periods of north-west Europe. Rapid climatic warming at this time saw the northward expansion of deciduous woodland into north-west Europe. Emerging new ecosystems presented changes in resource patterns and the Middle Mesolithic lithic typo-technological developments reflect novel foraging strategies as adaptations to the new opportunities of Boreal forest conditions. While Honey Hill-type assemblages are seen as part of such wider processes their distinctive typological signature attests to autochthonous, regional developments of human groups infilling the landscape. Such cultural insularity may reflect changing social boundaries with reduction in mobility range and physical isolation caused by rising sea level and the creation of the British archipelago.
Bone is frequently dated in archaeological studies and, especially for very old bones (more than 40,000 years old), it is critical to have an accurate and precise measure of the material-specific background value and its associated uncertainty. The SUERC Radiocarbon Laboratory has obtained a mammoth bone as a background bone standard and an appropriate number are now routinely prepared and measured in each AMS batch, resulting in the accumulation of a large number of background bone results over a two-year period. Additionally, information on which of the two accelerator mass spectrometry (AMS) instruments was used to make the radiocarbon (14C) measurements, and which sample pretreatment method (modified Longin or modified ultrafiltration) was used to extract and purify the collagen, is recorded for each sample. These data have been used to estimate the laboratory bone background (to be subtracted from each unknown bone sample prepared in the laboratory) and its associated analytical uncertainty. The statistical analysis of the bone results has made use of a linear mixed effects model to examine the variation, and to apportion the overall variation between and within batches on both AMS instruments, and the different pretreatment methods used at SUERC.
Dispersed facies basal ice – massive (i.e. structureless) ice with dispersed debris aggregates – is present at the margins of many glaciers and, as a product of internal glacial processes, has the potential to provide important information about the mechanisms of glacier flow and the nature of the subglacial environment. The origin of dispersed facies is poorly understood, with several hypotheses having been advanced for its formation, and there is disagreement as to whether it is largely a sedimentary or a tectonic feature. We test these established hypotheses at the temperate glacier Svínafellsjökull, Iceland, and find that none fully account for dispersed facies characteristics at this location. Instead, dispersed facies physical, sedimentological and stable-isotope (δ18O, δD) characteristics favour a predominantly tectonic origin that we suggest comprises the regelation and strain-induced metamorphism of debris-rich basal ice that has been entrained into an englacial position by tectonic processes operating at the base of an icefall. Further thickening of the resultant dispersed facies may also occur tectonically as a result of ice flow against the reverse bed slope of a terminal overdeepening. Lack of efficient subglacial drainage in the region of the overdeepening may limit basal melting and thus favour basal ice preservation, including the preservation of dispersed facies. Despite the relatively low sediment content of dispersed facies ( ∼1.6% by volume), its thickness (up to 25 m) and ubiquity at Svínafellsjökull results in a significant contribution to annual sediment discharge (1635–3270 m3 a−1) that is ∼6.5 times that contributed by debris-rich stratified facies basal ice.
We identified human paleodietary changes from inhabitants of the Guanzhong basin since 8000 BP, based on published carbon and nitrogen isotopic measurements on bones, fauna and plant remains. We also directly measured 14C ages, δ13C and δ15N values from bones unearthed at the Zhouyuan site, west of Guanzhong, in order to reconstruct paleodietary changes of the ancient inhabitants. We found that during the Laoguantai period, animal foods were the main source of nourishment with supplementary plant-derived foods. After this period, plant-derived foods became the main food source, with supplementary animal sources. The development of dry farming led to increased consumption of foxtail millet and broomcorn millet. This trend persisted and marked a fundamental shift from hunting, gathering, and fishing to farming and animal domestication. The dietary trends of the ancient inhabitants also show pronounced regional differences through time. The use of domestic animals was proportionally higher in the eastern part of the Guanzhong region, while wild animals were more common in the west.
The SUERC Radiocarbon Laboratory employs a one-step “background subtraction” method when calculating 14C ages. An interglacial wood (VIRI Sample K) is employed as the non-bone organic background standard, while a mammoth bone (LQH12) from Latton Quarry is used as the bone background standard. Results over several years demonstrate that the bone background is consistently around a factor of two higher and more variable than the wood background. As a result, the uncertainty on routine bone measurements is higher than for other sample types. This study investigates the factors that may contribute to the difference in F14C values and the higher variability. Preparations of collagen using modified Longin or ultrafiltration methods show no significant difference, nor does eliminating the collagen dissolution step. Two bone samples of known infinite age with respect to radiocarbon are compared and again no significant difference is observed. Finally, the quantity and age of the organic matter in the water used during the pretreatment is investigated and it is shown that there is insufficient organic matter in the reverse osmosis water to influence background values significantly. The attention is now on determining if incomplete demineralization could lead to contaminants being retained by the phosphate in the hydroxyapatite.
The existing spectral searches for quasars have increased the number of quasars known very substantially but have not contributed proportionately to an understanding of the collective properties because of the selection effects. To fully exploit the spectral searches we have developed the technique of automated quasar detection (AQD) using objective-prism plates from the UK Schmidt Telescope, the COSMOS measuring machine at the Royal Observatory Edinburgh, and the STARLINK nodes at Durham and Edinburgh.
Permineralized plant remains occur individually and in small mats within anoxic and dysoxic marine black shales deposited seaward of the Wedington delta (Fayetteville Formation, Middle Chester) in northwestern Arkansas. Plant debris and associated cephalopods occur within 20 km of offshore bars that developed at the mouths of delta distributary channels. The bars were produced by longshore paleocurrents flowing eastward among the southwestern margin of the Ozark Dome. The flora includes several genera of arborescent lycopods, zygopteridalean ferns, filicalean ferns, calamites, medullosan seed ferns and seed fern remains with features that are characteristic of the Lyginopteridaceae. Among the lyginopteridalean stems are specimens that have been described as Megaloxylon wheelerae, an arborescent form, as well as several undescribed species.
Two stems with prominent leaf scars represent one species of a new genus. The stems measure 35 cm and 34 cm long, and are approximately 2.5 cm in diameter. Leaf arrangement is helical, approaching a 3/8 phyllotaxis, with internodal lengths of about 3 cm. Stems are eustelic with a polygonal primary body 3-4 mm in diameter. Each leaf trace diverges from the cauline bundle as a single strand. The strand trifurcates in the cortex to produce a distinctive configuration of two c-shaped lateral bundles separated by a tangentially elongated central strand.
Pith cells are large with prominent walls. Some show internal contents suggestive of secretory substances. The primary body is surrounded by a distinctive zone of wood 3-4 cm wide. Large rays 2-5 cells wide and more than 8 mm high separate wedges of tracheids that typically are 2-4 cells wide. Secondary tracheids display multiseriate oval bordered pits on the radial walls. Vascular cambium and secondary phloem are present, but incompletely preserved. The cortex is differentiated into an inner parenchymatous zone with horizontally elongated “sclerotic” nests, and an outer zone of alternating bands of vertically elongated sclerenchyma and parenchyma.
This material significantly increases our knowledge of Namurian floras inhabiting non peat-forming environments, and emphasizes the systematic diversity among hydrasperman gymnosperms at the base of the Upper Carboniferous.
Terrestrial gastropods are problematical for radiocarbon (14C) measurement because they tend to incorporate carbon from ancient sources as a result of their dietary behavior. The 14C ecology of the pulmonate land snail, Helix melanostoma in Cyrenaica, northeastern Libya, was investigated as part of a wider study on the potential of using terrestrial mollusk shell for 14C dating of archaeological deposits. H. melanostoma was selected out of the species available in the region as it has the most predictable 14C ecology and also had a ubiquitous presence within the local archaeology. The ecological observations indicate that H. melanostoma has a very homogenous 14C ecology with consistent variations in F14C across sample sites controlled by availability of dietary vegetation. The majority of dated specimens from non-urbanized sample locations have only a small old-carbon effect, weighted mean of 476±48 14C yr, with between ~1% and 9% of dietary F14C from non-organic carbonate sources. Observed instabilities in the 14C ecology can all be attributed to the results of intense human activity not present before the Roman Period. Therefore, H. melanostoma and species with similar ecological behavior are suitable for 14C dating of archaeological and geological deposits with the use of a suitable offset.
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).