Quality dating: a well-defined protocol implemented at ETH for high-precision 14c-dates tested on late glacial wood

Advances in accelerator mass spectrometry have resulted in an unprecedented amount of new high-precision radiocarbon (14C) -dates, some of which will redefine the international 14C calibration curves (IntCal and SHCal). Often these datasets are unaccompanied by detailed quality insurances in place at the laboratory, questioning whether the 14C structure is real, a result of a laboratory variation or measurement-scatter. A handful of intercomparison studies attempt to elucidate laboratory offsets but may fail to identify measurement-scatter and are often financially constrained. Here we introduce a protocol, called Quality Dating, implemented at ETH-Zürich to ensure reproducible and accurate high-precision 14C-dates. The protocol highlights the importance of the continuous measurements and evaluation of blanks, standards, references and replicates. This protocol is tested on an absolutely dated German Late Glacial tree-ring chronology, part of which is intercompared with the Curt Engelhorn-Center for Archaeometry, Mannheim, Germany (CEZA). The combined dataset contains 170 highly resolved, highly precise 14C-dates that supplement three decadal dates spanning 280 cal. years in IntCal, and provides detailed 14C structure for this interval

Radiocarbon Protocols and First Intercomparison Results From The Chronos¹⁴ Carbon-Cycle Facility, University Of New South Wales, Sydney, Australia

The Chronos 14Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeological sciences. Here we report an overview of the Chronos facility, the pretreatment methods currently employed (bones, carbonates, peat, pollen, charcoal, and wood) and results of radiocarbon and stable isotope measurements undertaken on a wide range of sample types. Measurements on international standards, known-age and blank samples demonstrate the facility is capable of measuring 14C samples from the Anthropocene back to nearly 50,000 years ago. Future work will focus on improving our understanding of the Earth system and managing resources in a future warmer world

Defending the genome from the enemy within:mechanisms of retrotransposon suppression in the mouse germline

The viability of any species requires that the genome is kept stable as it is transmitted from generation to generation by the germ cells. One of the challenges to transgenerational genome stability is the potential mutagenic activity of transposable genetic elements, particularly retrotransposons. There are many different types of retrotransposon in mammalian genomes, and these target different points in germline development to amplify and integrate into new genomic locations. Germ cells, and their pluripotent developmental precursors, have evolved a variety of genome defence mechanisms that suppress retrotransposon activity and maintain genome stability across the generations. Here, we review recent advances in understanding how retrotransposon activity is suppressed in the mammalian germline, how genes involved in germline genome defence mechanisms are regulated, and the consequences of mutating these genome defence genes for the developing germline

Precise date for the Laacher See eruption synchronizes the Younger Dryas

The Laacher See eruption (LSE) in Germany ranks among Europe’s largest volcanic events of the Upper Pleistocene. Although tephra deposits of the LSE represent an important isochron for the synchronization of proxy archives at the Late Glacial to Early Holocene transition, uncertainty in the age of the eruption has prevailed. Here we present dendrochronological and radiocarbon measurements of subfossil trees that were buried by pyroclastic deposits that frmly date the LSE to 13,006 ± 9 calibrated years before present (bp; taken as ad 1950), which is more than a century earlier than previously accepted. The revised age of the LSE necessarily shifts the chronology of European varved lakes relative to the Greenland ice core record, thereby dating the onset of the Younger Dryas to 12,807 ± 12 calibrated years bp, which is around 130 years earlier than thought. Our results synchronize the onset of the Younger Dryas across the North Atlantic–European sector, preclude a direct link between the LSE and Greenland Stadial-1 cooling, and suggest a large-scale common mechanism of a weakened Atlantic Meridional Overturning Circulation under warming condition

Supplementary Material for: Contrasting Rates of LINE-1 Amplification among New World Primates of the Atelidae Family

<p>LINE-1 (L1) retrotransposons constitute the dominant category of transposons in mammalian genomes. L1 elements are active in the vast majority of mammals, and only a few cases of L1 extinction have been documented. The only possible case of extinction in primates was suggested for South American spider monkeys. However, these previous studies were based on a single species. We revisited this question with a larger phylogenetic sample, covering all 4 genera of Atelidae and 3 species of spider monkeys. We used an enrichment method to clone recently inserted L1 elements and performed an evolutionary analysis of the sequences. We were able to identify young L1 elements in all taxa, suggesting that L1 is probably still active in all Atelidae examined. However, we also detected considerable variations in the proportion of recent elements indicating that the rate of L1 amplification varies among Atelidae by a 3-fold factor. The extent of L1 amplification in Atelidae remains overall lower than in other New World monkeys. Multiple factors can affect the amplification of L1, such as the demography of the host and the control of transposition. These factors are discussed in the context of host life history.</p

Additive Effects of Steel Factor and Antisense Tgf-Beta-1 Oligodeoxynucleotide On Cd34(+) Hematopoietic Progenitor Cells

We previously demonstrated that TGF-beta 1 antisense oligodeoxynucleotides can release early CD34(+) bone marrow progenitors from quiescence, and increase the numbers of mixed and large erythroid colonies. As Steel Factor (SF) has a similar effect on colony formation by CD34(+) cells, we tested whether this factor acts by blocking the inhibitory effects of TGF-beta. That this is not generally the case was demonstrated by the finding that the combination of TGF-beta 1 antisense with SF in cultures of CD34(+) bone marrow cells yielded enhanced colony formation that was more than additive when compared to cultures containing the single agents. This combination also yielded enhanced colony formation by CD34(+) umbilical cord blood cells, but in this case, the effect was slightly less than additive. Thus in cord blood, some, but not all, of the progenitors that are maintained in quiescence by TGF-beta can be triggered into cycle by SF. However, the absolute number of CFU-GEMMs found in the antisense TGF-beta plus SF cultures of cord blood was I-fold higher than that found in comparable bone marrow cultures. These data correlate well with our previous observations that umbilical cord blood contains 4-fold more CD34(+) CD38(-) cells, the population found to respond to TGF-beta 1 antisense oligodeoxynucleotides