Is comparability of C-14 dates an issue?: A status report on the fourth international radiocarbon intercomparison

For more than 15 years, the radiocarbon community has participated in a series of laboratory intercomparisons in response to the issue of comparability of measurements as perceived within the wider user communities (Scott et al. 1990; Rozanski et al. 1992; Guiliksen and Scott 1995; Scott et al. 1997).<br/> In this report, we provide an update on the current C-14 laboratory intercomparison and reflect on future issues linked to the laboratory intercomparison program, not least those resulting from a significant growth in the number of accelerator mass spectrometry (AMS) facilities providing routine dating of small samples (milligram size)

Local biochemical and morphological differences in human Achilles tendinopathy: a case control study

<p>Abstract</p> <p>Background</p> <p>The incidence of Achilles tendinopathy is high and underlying etiology as well as biochemical and morphological pathology associated with the disease is largely unknown. The aim of the present study was to describe biochemical and morphological differences in chronic Achilles tendinopathy. The expressions of growth factors, inflammatory mediators and tendon morphology were determined in both chronically diseased and healthy tendon parts.</p> <p>Methods</p> <p>Thirty Achilles tendinopathy patients were randomized to an expression-study (<it>n </it>= 16) or a structural-study (<it>n </it>= 14). Biopsies from two areas in the Achilles tendon were taken and structural parameters: fibril density, fibril size, volume fraction of cells and the nucleus/cytoplasm ratio of cells were determined. Further gene expressions of various genes were analyzed.</p> <p>Results</p> <p>Significantly smaller collagen fibrils and a higher volume fraction of cells were observed in the tendinopathic region of the tendon. Markers for collagen and its synthesis collagen 1, collagen 3, fibronectin, tenascin-c, transforming growth factor-β fibromodulin, and markers of collagen breakdown matrix metalloproteinase-2, matrix metalloproteinase-9 and metallopeptidase inhibitor-2 were significantly increased in the tendinopathic region. No altered expressions of markers for fibrillogenesis, inflammation or wound healing were observed.</p> <p>Conclusion</p> <p>The present study indicates that an increased expression of factors stimulating the turnover of connective tissue is present in the diseased part of tendinopathic tendons, associated with an increased number of cells in the injured area as well as an increased number of smaller and thinner fibrils in the diseased tendon region. As no fibrillogenesis, inflammation or wound healing could be detected, the present data supports the notion that tendinopathy is an ongoing degenerative process.</p> <p>Trial registration</p> <p>Current Controlled Trials <a href="http://www.controlled-trials.com/ISRCTN20896880">ISRCTN20896880</a></p

Annually resolved North Atlantic marine climate over the last millennium

This is the final version of the article. Available from Nature Publishing Group via the DOI in this record.Owing to the lack of absolutely dated oceanographic information before the modern instrumental period, there is currently significant debate as to the role played by North Atlantic Ocean dynamics in previous climate transitions (for example, Medieval Climate Anomaly-Little Ice Age, MCA-LIA). Here we present analyses of a millennial-length, annually resolved and absolutely dated marine δ(18)O archive. We interpret our record of oxygen isotope ratios from the shells of the long-lived marine bivalve Arctica islandica (δ(18)O-shell), from the North Icelandic shelf, in relation to seawater density variability and demonstrate that solar and volcanic forcing coupled with ocean circulation dynamics are key drivers of climate variability over the last millennium. During the pre-industrial period (AD 1000-1800) variability in the sub-polar North Atlantic leads changes in Northern Hemisphere surface air temperatures at multi-decadal timescales, indicating that North Atlantic Ocean dynamics played an active role in modulating the response of the atmosphere to solar and volcanic forcing.We thank the members of the RV Bjarni Sæmundsson (Cruise No. B05-2006). This work was supported by the NERC-funded ULTRA project (Grant Number NE/H023356/1), NERC-funded CLAM project; (Project No. NE/N001176/1) and EU Millennium Project (Project number 017008). This study is a contribution to the Climate Change Consortium for Wales (C3W). We thank Brian Long (Bangor University) and Dr Julia Becker (Cardiff University) for their technical support, and Dr Manfred Mudelsee for his assistance with the trend analysis. We thank Dr Jessica Tierney and an anonymous reviewer for providing the constructive comments in the reviewing process

Use of Cis-[18F]Fluoro-Proline for Assessment of Exercise-Related Collagen Synthesis in Musculoskeletal Connective Tissue

Protein turnover in collagen rich tissue is influenced by exercise, but can only with difficulty be studied in vivo due to use of invasive procedure. The present study was done to investigate the possibility of applying the PET-tracer, cis-[18F]fluoro-proline (cis-Fpro), for non-invasive assessment of collagen synthesis in rat musculoskeletal tissues at rest and following short-term (3 days) treadmill running. Musculoskeletal collagen synthesis was studied in rats at rest and 24 h post-exercise. At each session, rats were PET scanned at two time points following injection of cis-FPro: (60 and 240 min p.i). SUV were calculated for Achilles tendon, calf muscle and tibial bone. The PET-derived results were compared to mRNA expression of collagen type I and III. Tibial bone had the highest SUV that increased significantly (p<0.001) from the early (60 min) to the late (240 min) PET scan, while SUV in tendon and muscle decreased (p<0.001). Exercise had no influence on SUV, which was contradicted by an increased gene expression of collagen type I and III in muscle and tendon. The clearly, visible uptake of cis-Fpro in the collagen-rich musculoskeletal tissues is promising for multi-tissue studies in vivo. The tissue-specific differences with the highest basal uptake in bone are in accordance with earlier studies relying on tissue incorporation of isotopic-labelled proline. A possible explanation of the failure to demonstrate enhanced collagen synthesis following exercise, despite augmented collagen type I and III transcription, is that SUV calculations are not sensitive enough to detect minor changes in collagen synthesis. Further studies including kinetic compartment modeling must be performed to establish whether cis-Fpro can be used for non-invasive in-vivo assessment of exercise-induced changes in musculoskeletal collagen synthesis

Is there a reliable taphonomic clock in the temperate North Atlantic? An example from a North Sea population of the mollusc Arctica islandica

This is the final version. Available on open access from Elsevier via the DOI in this recordTwo hundred and seventy-seven shells of the long-lived bivalve mollusc Arctica islandica, collected from the Fladen Ground, northern North Sea, were radiocarbon dated and their taphonomic condition assessed, in order to determine whether taphonomic condition might provide a reliable indication of time since the death of the animal. With nine stations from across the Fladen Ground sampled, some strong geographic biases in 14C ages were apparent, with living and modern (post-bomb pulse) material found in the northern part of the Fladen Ground while older material (first half of the last millennium and early Holocene/Lateglacial) was concentrated in the central and western sites. Samples from the south and east Fladen Ground were sparse and were dominated by material from the second half of the last millennium. This south-north distribution is interpreted as the result of environmental change over millennial time-scales in the North Sea causing a gradual northward shift of living A. islandica populations and is not thought to be related to post mortem transport of shells to the south and east. Taphonomic condition, assessed using discriminant analysis and principal component analysis of five characteristics (amount of remaining periostracum, presence and condition of the ligament, extent of erosion at the shell margin, amount of bioerosion, and nacre condition), appeared to be a generally unreliable indicator of time since the death of the animal. Based on these five taphonomic characteristics, discriminant analysis placed 81.1% of post-bomb shells, 39.6% of shells from the period 0–500 yr BP, 68.0% of shells from the period 500–1000 yr BP and 20.0% of shells from the Early Holocene/Late glacial group into the correct radiocarbon age grouping, providing no support for the idea that this method can be used to triage shells for chronology construction as an alternative to radiometric dating.Natural Environment Research Council (NERC

Future needs and requirements for AMS C-14 standards and reference materials

C-14 measurement uses a number of standards and reference materials with different properties. Historically the absolute calibration of C-14 measurement was tied to 1890 wood, through the 'primary' standard of NBS-OxI (produced by the National Bureau of Standards, now NIST - National Institute of Standards and technology) subsequently replaced by NBS-OxII. These are both internationally calibrated and certified materials, whose C-14 activities are known absolutely. A second tier of materials, often called secondary standards or reference materials, and including internationally recognised materials such as ANU-sucrose (now also IAEA-C6), Chinese - sucrose and the IAEA C1-C6 series, augmented by additional oxalic acid samples are also used routinely. The activity of these materials has been estimated from large numbers of measurements made by many laboratories. Recently, further natural materials from the Third and Fourth International Radiocarbon Inter- comparisons (TIRI and FIRI) have been added to this list. The activities of these standards and reference materials span both the applied C-14 age range and the chemical composition range of typical samples, but this is not achieved uniformly and there is a continuing need for reference materials for laboratory quality control and measurement-traceability purposes. In this paper, we review the development of C-14 Standards and reference materials and consider the future requirements for such materials within the C-14 AMS community

Gene expression and matrix turnover in overused and damaged tendons

Chronic, painful conditions affecting tendons, frequently known as tendinopathy, are very common types of sporting injury. The tendon extracellular matrix is substantially altered in tendinopathy, and these changes are thought to precede and underlie the clinical condition. The tendon cell response to repeated minor injuries or “overuse” is thought to be a major factor in the development of tendinopathy. Changes in matrix turnover may also be effected by the cellular response to physical load, altering the balance of matrix turnover and changing the structure and composition of the tendon. Matrix turnover is relatively high in tendons exposed to high mechanical demands, such as the supraspinatus and Achilles, and this is thought to represent either a repair or tissue maintenance function. Metalloproteinases are a large family of enzymes capable of degrading all of the tendon matrix components, and these are thought to play a major role in the degradation of matrix during development, adaptation and repair. It is proposed that some metalloproteinase enzymes are required for the health of the tendon, and others may be damaging, leading to degeneration of the tissue. Further research is required to investigate how these enzyme activities are regulated in tendon and altered in tendinopathy. A profile of all the metalloproteinases expressed and active in healthy and degenerate tendon is required and may lead to the development of new drug therapies for these common and debilitating sports injuries

The Marine Radiocarbon Bomb Pulse across the Temperate North Atlantic: A Compilation of Δ14C Time Histories from Arctica islandica Growth Increments

Marine radiocarbon bomb-pulse time histories of annually resolved archives from temperate regions have been underexploited. We present here series of Δ14C excess from known-age annual increments of the long-lived bivalve mollusk Arctica islandica from 4 sites across the coastal North Atlantic (German Bight, North Sea; Troms⊘, north Norway; Siglufjordur, north Icelandic shelf; Grimsey, north Icelandic shelf) combined with published series from Georges Bank and Sable Bank (NW Atlantic) and the Oyster Ground (North Sea). The atmospheric bomb pulse is shown to be a step-function whose response in the marine environment is immediate but of smaller amplitude and which has a longer decay time as a result of the much larger marine carbon reservoir. Attenuation is determined by the regional hydrographic setting of the sites, vertical mixing, processes controlling the isotopic exchange of 14C at the air-sea boundary, 14C content of the freshwater flux, primary productivity, and the residence time of organic matter in the sediment mixed layer. The inventories form a sequence from high magnitude-early peak (German Bight) to low magnitude-late peak (Grimsey). All series show a rapid response to the increase in atmospheric Δ14C excess but a slow response to the subsequent decline resulting from the succession of rapid isotopic air-sea exchange followed by the more gradual isotopic equilibration in the mixed layer due to the variable marine carbon reservoir and incorporation of organic carbon from the sediment mixed layer. The data constitute calibration scries for the use of the bomb pulse as a high-resolution dating tool in the marine environment and as a tracer of coastal ocean water masses

ASHRAE's Proposed Guideline 14P for Measurement of Energy and Demand Savings: How to Determine What Was Really Saved by the Retrofit

ASHRAE has recently completed the development of Guideline 14 to fill a need for a standard set of energy (and demand) savings calculation procedures. Guideline 14 is intended to be a guideline that provides a minimum acceptable level of performance in the measurement of energy and demand savings from energy management projects applied to residential, commercial or industrial buildings. Such measurements can serve as the basis for commercial transactions between Energy Service Companies (ESCOs) and their customers, or other energy conservation providers that rely on energy savings as the basis for repayment of the costs of the retrofit. When applied properly, ASHRAE Guideline 14 is expected to provide adequate assurance for the payment of services by allowing for well specified measurement methods that provide reasonably accurate savings calculations. ASHRAE Guideline 14 may also be used by governments to calculate pollution reductions from energy efficiency activities. Since Guideline 14 is intended to be applied to an individual building, or a few buildings served by a utility meter, large scale utility energy conservation programs, such as those involving statistical sampling, are not addressed by the current version of Guideline 14. Furthermore, metering standards and procedures for calculating savings from modifications to major industrial process loads are also not covered. This paper presents an overview of the measurement methods contained in ASHRAE Guideline 14 , including a discussion about how they were developed, and their intended relationship with other national protocols for measuring savings from energy conservation programs, such as the USDOE's International Performance Measurement and Verification Protocols (IPMVP)