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

A period of calm in Scottish seas: a comprehensive study of ΔR values for the northern British Isles coast and the consequent implications for archaeology and oceanography

The Marine Radiocarbon Reservoir Effect (MRE) is a 14C age offset between contemporaneous marine- and terrestrially-derived carbon. In Northern Hemisphere surface waters it is of the order of 400 years but temporal and spatial deviations, known as ΔR, occur. This study provides a comprehensive dataset of 21 ΔR and MRE values for the east coast of Scotland and 21 recalculated values for the west coast of Scotland and Ireland, for the period c. 3500 BC to 1450 AD. They are presented as mean, site-specific ΔR and MRE values, together with their associated uncertainties, calculated as standard errors for predicted values. The ΔR values range from -320 ± 35 to +150 ± 28 14C years and show no spatial or temporal trends. The MRE values range from 59 ± 40 to 531 ± 26, show an almost identical distribution pattern to the ΔR values and again show no spatial or temporal trends. Results show that ΔR values calculated for a single site using statistically indistinguishable groups of terrestrial and marine radiocarbon age measurements can produce variability of up to 225 14C years. ΔR is an important factor in the accurate calibration of samples containing marine-derived carbon for archaeological interpretation but is often also used as an indicator of changes in 14C specific activity of the oceans, and therefore a proxy for changes in ocean circulation and/or climate. Using the methods outlined in this paper, it is apparent that ΔR values for the northern part of the British Isles have been relatively stable, within our ability to quantify non-random variation in the data. The fact that significant climatic shifts have been recorded during this time, yet these are not visible in the ΔR data, presents a cautionary tale regarding the use of ΔR to infer large-scale oceanographic or climatic changes. Upon the exclusion of 5 outliers from the 42 values, the remaining ΔR values are statistically indistinguishable from one another and range from -142 ± 61 to +40 ± 47 14C years. 34 of these values are from Scottish archaeological sites and can be combined to produce a mean value for Scotland of -47 ± 52 14C years for the period 3500 BC to 1450 AD, to be used only in the absence of site- and period-specific data

Holocene variations in the Scottish marine radiocarbon reservoir effect

We assessed the evidence for variations in the marine radiocarbon reservoir effect (MRE) at coastal, archaeological Iron Age sites in north and west Scotland by comparing AMS measurements of paired marine and terrestrial materials (4 pairs per context). DeltaR values were calculated from measurements on material from 3 sites using 6 sets of samples, all of which were deposited around 2000 BP. The weighted mean of the DeltaR determinations was -79 +/- 17 C-14 yr, which indicates a consistent, reduced offset between atmospheric and surface ocean C-14 specific activity for these sites during this period, relative to the present day (DeltaR = similar to0 C-14 yr). We discuss the significance of this revised AR correction by using the example of wheelhouse chronologies at Hornish Point and their development in relation to brochs. In addition, we assess the importance of using the concepts of MRE correction and AR variations when constructing chronologies using C-14 measurements made on materials that contain marine- derived carbon

Survival Rates of Teeth with Primary Endodontic Treatment after Core/Post and Crown Placement

Introduction The objective of this study was to determine the effect of delayed placement of the core/post and crown on the outcomes of nonsurgical root canal therapy (NSRCT). Methods According to the Delta Dental of Wisconsin claims database, 160,040 NSRCTs were completed with a core/post and a crown placed before the end of the continuous coverage period or occurrence of an untoward event. Untoward events were defined as a retreatment, apicoectomy, or extraction as defined by the Code on Dental Procedures and Nomenclature. Statistical analysis was performed by using a multivariable Cox proportional hazards model. Results The survival rate from the time of crown placement to an untoward event was 99.1% at 1 year, 96.0% at 3 years, 92.3% at 5 years, and 83.8% at 10 years. Failure rates were greater when a core/post was placed more than 60 days after the NSRCT (adjusted hazard ratio, 1.08) and when the crown was placed more than 60 days after the core/post placement (adjusted hazard ratio, 1.14). Overall, the survival rates of NSRCT were greater when performed by an endodontist versus other providers. Conclusions On the basis of the information available from insurance claims data, this study shows that the long-term survival rates of initial endodontic therapy are adversely affected by the delayed placement of the final restoration and full coverage crown

Life after SIRI- where next?

Radiocarbon (14C) dating is routinely used, yet occasionally, issues still arise surrounding laboratory offsets, and unexpected and unexplained variability. Quality assurance and quality control have long been recognized as important in addressing the two issues of comparability (or bias, accuracy) and uncertainty or variability (or precision) of measurements both within and between laboratories (Long and Kalin 1990). The 14C community and the wider user communities have supported interlaboratory comparisons as one of several strands to ensure the quality of measurements (Scott et al. 2018). The nature of the intercomparisons has evolved as the laboratory characteristics have changed s. The next intercomparison is currently being planned to take place in 2019–2020. The focus of our work in designing intercomparisons is to (1) assist laboratories by contributing to their QA/QC processes, (2) supplement and enhance our suite of reference materials that are available to laboratories, (3) provide consensus 14C values with associated (small) uncertainties for performance checking, and (4) provide estimates of laboratory offsets and error multipliers which can inform subsequent modeling and laboratory improvements

Dynamic plantar loading index detects altered foot function in individuals with rheumatoid arthritis but not changes due to orthotic use

Background Altered foot function is common in individuals with rheumatoid arthritis. Plantar pressure distributions during gait are regularly assessed in this patient group; however, the association between frequently reported magnitude-based pressure variables and clinical outcomes has not been clearly established. Recently, a novel approach to the analysis of plantar pressure distributions throughout stance phase, the dynamic plantar loading index, has been proposed. This study aimed to assess the utility of this index for measuring foot function in individuals with rheumatoid arthritis.Methods Barefoot plantar pressures during gait were measured in 63 patients with rheumatoid arthritis and 51 matched controls. Additionally, 15 individuals with rheumatoid arthritis had in-shoe plantar pressures measured whilst walking in standardized footwear for two conditions: shoes-only; and shoes with prescribed custom foot orthoses. The dynamic plantar loading index was determined for all participants and conditions. Patient and control groups were compared for significant differences as were the shod and orthosis conditions.Findings The patient group was found to have a mean index of 0.19, significantly lower than the control group's index of 0.32 (p > 0.001, 95% CI [0.054, 0.197]). No significant differences were found between the shoe-only and shoe plus orthosis conditions. The loading index was found to correlate with clinical measures of structural deformity.Interpretation The dynamic plantar loading index may be a useful tool for researchers and clinicians looking to objectively assess dynamic foot function in patients with rheumatoid arthritis; however, it may be unresponsive to changes caused by orthotic interventions in this patient group.</p

A Leucine-enriched Diet Enhances Overload-induced Growth and Markers of Protein Synthesis in Aged Rat Skeletal Muscle

Introduction: The hypertrophic response to overload in fast-twitch skeletal muscle is impaired in aged humans and rats, and impaired protein synthesis pathway activation is hypothesized to be a contributing factor. Muscle growth occurs when protein synthesis exceeds protein degradation. Dietary supplementation of the essential amino acid leucine has been shown to enhance protein synthesis in both young and aged skeletal muscle. Leucine acts in part by activating mammalian target of rapamycin (mTOR; a key upstream regulator of protein synthesis pathways) as well as by attenuating the activation of 5\u27-AMP-activated protein kinase (AMPK; a negative regulator of mTOR and protein synthesis). During the aging process, AMPK Thr172 phosphorylation (and thus its activation) is increased, purportedly inhibiting gains in muscle mass and strength. Although dietary leucine supplementation has been shown to enhance strength gains in response to resistance training in young humans, the potential for leucine supplementation to enhance overload-induced muscle hypertrophy in aged humans or animal models has not been examined. Thus, the aim of this study was to determine whether dietary leucine supplementation can enhance markers of protein synthesis and rescue hypertrophy in overloaded fast-twitch skeletal muscles of aged rats to levels comparable to their younger counterparts. It was hypothesized that dietary leucine supplementation during 7 days of fast-twitch plantaris muscle overload would enhance plantaris muscle hypertrophy in aged rats to levels observed in young adult rats not receiving leucine. It was also hypothesized that dietary leucine supplementation during the overload period would suppress AMPK phosphorylation and enhance markers of protein synthesis [70 kDa ribosomal protein S6 kinase (p70S6k), ribosomal protein S6 (rpS6), and eukaryotic elongation factor 2 (eEF2)] in the overloaded fast-twitch plantaris muscles of the aged rats to levels observed in young adult rats not receiving leucine. Methods: Young adult (8 mo.) and old (33 mo.) male Fisher 344 x Brown Norway F1 Hybrid (FBN) rats underwent a 1-week unilateral overload of the fast-twitch plantaris muscles via tenotomy of the synergistic gastrocnemius muscle. Within each age group, animals were matched for body weight and separated into either a dietary leucine supplementation group (normal rat chow supplemented by an additional 5% leucine content in place of 5% of the carbohydrate content; n = 7/age group) or placebo group (normal rat chow; n = 6/age group). The leucine groups started the leucine-enriched diet 2 days prior to, and throughout, the overload intervention. All animals had ad libitum access to water and chow during the entire experiment; no differences in daily calorie consumption were observed between the placebo vs. leucine groups within each age group. At the end of the overload period, sham-operated and overloaded plantaris muscles were harvested and analyzed via western blotting for the phosphorylations of AMPK, p70S6k, rpS6, and eEF2. A 2x2x2 ANOVA with repeated measures was used for analyses of the effects of age, dietary intervention, and overload (the repeated measure) on muscle hypertrophy. A 2x2 ANOVA was used to measure the percent changes in hypertrophy and western blot analyses. Post-hoc comparisons were accomplished via a Fisher\u27s Least Significant Difference test, with statistical significance being set at p ≤ 0.05. Results: Dietary leucine enrichment significantly (p ≤ 0.05) enhanced overload-induced fast-twitch plantaris muscle hypertrophy in old, but not in young adult, animals. A similar effect was also observed in the slow-twitch soleus muscles, but western blotting analyses are only presented for the fast-twitch plantaris muscles. Sham and overloaded plantaris muscle AMPK phosphorylation (Thr172) was significantly higher in aged animals receiving normal chow compared to young adult animals; however, leucine supplementation in old animals reduced this AMPK phosphorylation to levels similar to young adult animals. Phospho-p70S6k (Thr389) and phospho-rpS6 (Ser235/Ser236) were significantly lower in old vs. young overloaded muscles under placebo conditions, but leucine partially restored both p70S6k and rpS6 phosphorylations in old overloaded muscles to that of young adult overloaded muscles. Overload significantly increased total eEF2 content and decreased inhibitory eEF2 phosphorylation (Thr56; normalized to total eEF2) in young adult muscles regardless of leucine supplementation. Total eEF2 content was unaffected by overload in old placebo muscles, but leucine supplementation in old animals non-significantly (p = 0.09) restored the overload-induced increase in total eEF2 content. Muscle eEF2 phosphorylation was unaffected by overload or leucine supplementation in old animals. Discussion: These novel findings indicate that a leucine-enriched diet may potentially enhance overload-induced growth of aged fast-twitch muscle, in part by enhancing pathways known to stimulate protein synthesis. This is in accord with previous findings of leucine’s stimulating effect on protein synthesis in both young adult and aged skeletal muscle under resting conditions. The fact that leucine supplementation enhanced overload-induced hypertrophy only in the old (and not the young) animals may reflect the high growth stimulus of the chronic overload model. That is, the balance of protein synthesis/degradation rates under such a large chronic growth stimulus may not be the limiting factor in young animals, in which muscle growth is not impaired (i.e., synthesis/degradation rates may reach futile levels, and another factor such as sarcomere assembly may be limiting). However, the impaired balance of protein synthesis/degradation rates may be the limiting factor to growth in aged muscle, and leucine may correct this imbalance to restore muscle growth to levels observed in young animals

A Leucine-enriched Diet Enhances Overload-induced Growth and Suppresses Markers of Protein Degradation in Aged Rat Skeletal Muscle

Introduction: The hypertrophic response to overload in fast-twitch skeletal muscle is impaired in aged humans and rats, and upregulation of protein degradation pathways are hypothesized to be a contributing factor. Muscle growth occurs when protein synthesis is greater than protein degradation. Dietary supplementation of the essential amino acid leucine has been shown to reduce protein degradation in both young and aged skeletal muscle. Specifically, leucine acts in part by attenuating 5\u27-AMP-activated protein kinase (AMPK) activation as well as the translocation of the forkhead box transcription factor 3A (FoxO3, known to promote transcription of mRNAs encoding degradation pathway proteins) to the nucleus. Akt (a promoter of muscle growth) prevents translocation of FoxO3 into the nucleus by phosphorylating FoxO3 phosphorylation at Ser318/321. However, AMPK, inhibits Akt\u27s phosphorylation of FoxO3, allowing it to enter the nucleus and increase transcription of protein degradation pathway genes encoding ubiquitin ligase proteins such as muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx, or Atrogin-1). During the aging process, AMPK Thr172 phosphorylation (and thus its activation) is increased, purportedly inhibiting gains in muscle mass and strength. Although dietary leucine supplementation has been shown to enhance strength gians in response to resistance training in young humans, the potential for leucine supplementation to enhance overload-induced muscle hypertrophy in aged humans or animal models has not been examined. Thus, the aim of this study was to determine whether dietary leucine supplementation can attenuate markers of protein degradation and rescue hypertrophy during overload in the fast-twitch skeletal muscles of aged rats to levels comparable to their younger counterparts. It was hypothesized that dietary leucine supplementation during 7 days of fast-twitch plantaris muscle overload would enhance plantaris muscle hypertrophy in aged rats to levels observed in young adult rats not receiving leucine. It was also hypothesized that dietary leucine supplementation during the overload period would alter markers of protein degradation (enhance FoxO3 phosphorylation and reduce the levels of AMPK phosphorylation, Atrogin-1 protein content, and MuRF1 protein content) in the overloaded fast-twitch plantaris muscles of the aged rats to levels observed in young adult rats not receiving leucine. Methods: Young adult (8 mo.) and old (33 mo.) male Fisher 344 x Brown Norway F1 Hybrid (FBN) rats underwent a 1-week unilateral overload of the fast-twitch plantaris muscles via tenotomy of the synergistic gastrocnemius muscle. Within each age group, animals were matched for body weight and separated into either a dietary leucine supplementation group (normal rat chow supplemented by an additional 5% leucine content in place of 5% of the carbohydrate content; n = 7/age group) or placebo group (normal rat chow; n = 6/age group). The leucine groups started the leucine-enriched diet 2 days prior to, and throughout, the overload intervention. All animals had ad libitum access to water and chow during the entire experiment; no differences in daily calorie consumption were observed between the placebo vs. leucine groups within each age group. At the end of the overload period, sham-operated and overloaded plantaris muscles were harvested and analyzed via western blotting for the phosphorylations of AMPK and FoxO3 as well as total levels of Atrogin-1 and MuRF1. A 2x2x2 ANOVA with repeated measures was used for analyses of the effects of age, dietary intervention, and overload (the repeated measure) on muscle hypertrophy. A 2x2 ANOVA was used to measure the percent changes in hypertrophy and western blot analyses. Post-hoc comparisons were accomplished via a Fisher\u27s Least Significant Difference test, with statistical significance being set at p ≤ 0.05. Results: Dietary leucine enrichment significantly (p ≤ 0.05) enhanced overload-induced fast-twitch plantaris muscle hypertrophy in old, but not in young adult, animals. A similar effect was also observed in the slow-twitch soleus muscles, but western blotting analyses are only presented for the fast-twitch plantaris muscles. Sham and overloaded plantaris muscle AMPK phosphorylation was significantly higher in aged animals receiving normal chow compared to young adult animals; however, leucine supplementation in old animals reduced this AMPK phosphorylation to levels similar to young adult animals. Compared to placebo, leucine also non-significantly (p = 0.07) enhanced FoxO3 phosphorylation in the overloaded muscles of both young adult and old animals (thus theoretically reducing FoxO3 translocation to the nucleus). Accordingly, leucine also non-significantly (p = 0.07) reversed the overload-induced increase (from a 22.8% increase to a 17.0% decrease) in Atrogin-1 content in aged muscles and non-significantly (p = 0.14) enhanced the overload-induced decrease in MuRF1 content in the muscles of both age groups. Discussion: These novel findings indicate that a leucine-enriched diet may potentially enhance overload-induced growth of aged fast-twitch muscle, in part by suppressing pathways known to stimulate protein degradation. This is in accord with previous findings of leucine’s suppressive effect on protein degradation in both young adult and aged skeletal muscle under resting conditions. The fact that leucine supplementation enhanced overload-induced hypertrophy only in the old (and not the young) animals may reflect the high growth stimulus of the chronic overload model. That is, the balance of protein synthesis/degradation rates under such a large chronic growth stimulus may not be the limiting factor in young animals, in which muscle growth is not impaired (i.e., synthesis/degradation rates may reach futile levels, and another factor such as sarcomere assembly may be limiting). However, the impaired balance of protein synthesis/degradation rates may be the limiting factor to growth in aged muscle, and leucine may correct this imbalance to restore muscle growth to levels observed in young animals

Evaluating the climate effects of mid-1800s deforestation in New England, USA, using a Weather, Research, and Forecasting (WRF) Model Multi-Physics Ensemble

The New England region of the northeastern United States has a land use history characterized by forest clearing for agriculture and other uses during European colonization and subsequent reforestation following widespread farm abandonment. Despite these broad changes, the potential influence on local and regional climate has received relatively little attention. This study investigated wintertime (December through March) climate impacts of reforestation in New England using a high-resolution (4 km) multiphysics ensemble of the Weather Research and Forecasting Model. In general, the conversion from mid-1800s cropland/grassland to forest led to warming, but results were sensitive to physics parameterizations. The 2-m maximum temperature (T2max) was most sensitive to choice of land surface model, 2-m minimum temperature (T2min) was sensitive to radiation scheme, and all ensemble members simulated precipitation poorly. Reforestation experiments suggest that conversion of mid-1800s cropland/grassland to present-day forest warmed T2max +0.5 to +3 K, with weaker warming during a warm, dry winter compared to a cold, snowy winter. Warmer T2max over forests was primarily the result of increased absorbed shortwave radiation and increased sensible heat flux compared to cropland/grassland. At night, T2min warmed +0.2 to +1.5 K where deciduous broadleaf forest replaced cropland/grassland, a result of decreased ground heat flux. By contrast, T2min of evergreen needleleaf forest cooled –0.5 to –2.1 K, primarily owing to increased ground heat flux and decreased sensible heat flux