Search

Radiocarbon reservoir effects (RREs) are observed when the14C concentration of aquatic reservoirs is lower than the contemporary atmosphere. Within these reservoirs, aquatic species will also have a14C depleted signal, and humans feeding on these species will show a dietary RRE. Human dietary RREs are often viewed as a problem for the establishment of reliable chronologies. However, they also represent an opportunity to introduce radiocarbon as a dietary proxy when investigating possible past human consumption of aquatic food groups. Here, a synthesis of previously published and new radiocarbon dates on edible aquatic species from central and northern Germany is presented. The samples were collected from modern and archaeological contexts. The goal was to provide an approximate RRE baseline within Germany. The results show that within the German context, local RREs in edible aquatic species are usually large and variable. The variability in local RREs implies that precise quantitative human dietary estimates will most likely not be possible. However, the large values of local RREs allow the use of14C measured in human bone collagen as an extra dietary proxy that can aid in detecting the consumption of aquatic food groups when traditional isotopic proxies (δ13C and δ15N) do not provide unambiguous estimates. [ABSTRACT FROM AUTHOR]

Long-term environmental changes in some areas of Central Europe are still poorly documented due to the lack of archives suitable for well-established paleoecological approaches. However, paleorecords of such areas would provide important insights into the Holocene vegetation history of Central Europe. To contribute to fill this gap, we conducted soil charcoal analyses to investigate fire and forest history for the eastern Harz Mountains (Germany). Soil from 15 sequences at three investigation sites was analyzed, and charcoal assemblages were extracted. The taxonomic analysis shows Holocene woodland composition changes, from post-glacial pioneer woodland, dominated by pine, to broad-leaf closed forests, dominated by oak, and succeeded by beech. The temporal distribution of accelerator mass spectrometry (AMS)-14C datings of single charcoal pieces indicates that fire events occurred regionally synchronous, mainly in the late-Pleistocene/early-Holocene and late-Holocene periods. The radiocarbon dating is supported by the description of the sampled soil sequences, which permits the identification of late-Pleistocene/early-Holocene in situ formed soil horizons, as well as evidences late-Holocene erosion-sedimentation processes. Climate seems to have triggered late-Pleistocene/early-Holocene fire events. In contrast, the increase of fires, at both local and regional scales, during the late Holocene in low flammable broad-leaf forests is interpreted as related to human activities. Finally, it is highlighted that the species spectrum of the extracted charcoal assemblages and the radiocarbon ages obtained fits regional and over-regional data, also concerning the soil charcoal concentrations that appear to be included in regional and global ranges of soil charcoal pools. [ABSTRACT FROM AUTHOR]

The woodland history of the forest of Stodthagen (northern Germany) was investigated by using complementary palaeobotanical indicators. Six soil profiles from the study plot were sampled, the wood charcoal pieces extracted from the soil samples were quantified, taxonomically identified, and some were radiocarbon dated. Peat sequences from a small adjacent mire were also sampled and the pollen, microcharcoal, and macrocharcoal were analysed. The pollen record shows a continuous forestation during the Holocene, with small indication of a disturbance phase during the late Holocene. This continuity of the woodland presence is confirmed by the weak quantity of macrocharcoal, indicating that fire did not have a serious impact during the Holocene in terms of canopy opening, despite the identification of three local fire events. However, large amounts of wood charcoal pieces were found in the soil samples allowing the identification of at least one more fire event, dated in the Iron Age, unrecorded in the charcoal signal from the peat sequences. The taxonomical charcoal assemblage is in agreement with the pollen data. This innovative multiproxy approach allows the assessment of the ancient and continual presence of a woodland at the study site, which highlights the biological and patrimonial interest of the area and justifies the ongoing conservation management of the woodland. [ABSTRACT FROM PUBLISHER]

The modern antiquities market uses radiocarbon (14C) dating to screen for forged objects. Although this fact shows the potential and power of the method, the circumstances where it is applied can be questionable and call for our attention. Here we present an outline of a call to radiocarbon laboratories for due diligence and best practice approaches to the analysis of antique objects requested by non-research clients. [ABSTRACT FROM AUTHOR]

The article focuses on the Gundestrup cauldron exhibited at the Danish National Museum in Copenhagen, Denmark. It is said that among the objects exhibited at the museum, the Gundestrup cauldron has kept its outstanding position since it was found more than a century ago. This has to do with the fact that people are facing ancient imagery not met elsewhere.

The Leibniz-Labor was founded to provide radiometric dating services using AMS and measured over 15 000 samples and 26 800 targets up to September 2002. Research and development have primarily been directed at improving the efficiency and reliability of AMS measurements, optimising existing sample preparation procedures for AMS and developing new ones. The standard chemical pre-treatment of organic radiocarbon samples produces often two fractions: one from which contaminants have been removed, and one in which they have been enriched. Dating both fractions reveals the degree of sample contamination. This provides a useful indication of the reliability of the sample age obtained and of the environmental conditions where the sample was taken.Upgrades to reduce maintenance include replacing four cryo- by turbo pumps, installing a deionizer loop, which keeps conductivity between 100 and 150 μS/cm to control corrosion, in the closed cooling water circuit, and developing a new sample wheel, which holds target holders with a groove and spring clip.Long term stability is demonstrated by the results obtained for IAEA reference materials, measured routinely and regularly over the years. Tests made as part of the FIRI project demonstrate that reliable measurements down to <0.1 mg C can be made. [Copyright &y& Elsevier]

Abstract: Radiocarbon dating is the most widely used dating technique in the world. Recent advances in Accelerator Mass Spectrometry (AMS) and sample preparation techniques have reduced the sample-size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes. Today, it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates. The production of 14C in the atmosphere varies through time due to changes in the Earth''s geomagnetic field intensity and in its concentration, which is regulated by the carbon cycle. As a result of these two variables, a radiocarbon age is not equivalent to a calendar age. Four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12,000 calendar years before present. This paper presents high precision paired 230Th/234U/238U and 14C age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12,000 to 50,000 years before present. We developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years, taking full account of combined errors in input ages and calibration uncertainties. Our radiocarbon calibration program is publicly accessible at: http://www.radiocarbon.LDEO.columbia.edu/ along with full documentation of the samples, data, and our statistical calibration model. [Copyright &y& Elsevier]

Motor neuron degeneration and spinal cord demyelination are hallmark pathological events in Amyotrophic Lateral Sclerosis (ALS). Endogenous retrovirus-K (ERVK) expression has an established association with ALS neuropathology, with murine modeling pointing to a role for the ERVK envelope ( env ) gene in disease processes. Here, we describe a novel viral protein cryptically encoded within the ERVK env transcript, which resembles two distinct cysteine-rich neurotoxic proteins: conotoxin proteins found in marine snails and the Human Immunodeficiency Virus (HIV) Tat protein. Consistent with Nuclear factor-kappa B (NF-κB)-induced retrotransposon expression, the ERVK conotoxin-like protein (CTXLP) is induced by inflammatory signaling. CTXLP is found in the nucleus, impacting innate immune gene expression and NF-κB p65 activity. Using human autopsy specimens from patients with ALS, we further showcase CTXLP expression in degenerating motor cortex and spinal cord tissues, concomitant with inflammation linked pathways, including enhancement of necroptosis marker mixed lineage kinase domain-like (MLKL) protein and oligodendrocyte maturation/myelination inhibitor Nogo-A. These findings identify CTXLP as a novel ERVK protein product, which may act as an effector in ALS neuropathology.

Background: The optimal site for local anesthetic injection during ultrasound-guided sciatic popliteal block remains controversial., Methods: Patients were randomized to receive 25 mL ropivacaine 0.75% around the sciatic nerve cephalad to the peroneal-tibial division in group A (n = 51) or caudad to the division in group B (n = 51). The sensory and motor blocks were evaluated every 5 minutes up to 30 minutes., Results: Rates of complete sensory block and surgical anesthesia were superior in group B (P < 0.0001)., Conclusion: The caudad technique provided better surgical anesthesia.