A Single-Year Cosmic Ray Event at 5410 BCE Registered in C-14 of Tree Rings

The annual C-14 data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and similar to 660 BCE. Here, we report another rapid increase of C-14 concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These C-14 data series show a significant increase of similar to 6 parts per thousand in 5411-5410 BCE. The signature of C-14 variation is very similar to the confirmed three SEP events and points to an extreme short-term flux of cosmic ray radiation into the atmosphere. The rapid C-14 increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand C-14 excursion during 5481-5471 BCE. The similarity of our C-14 data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.Peer reviewe

From the Editor

The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Erratum

The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

From the Editor

The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

The transformation of Sonoran Desert wetlands following the historic decrease of burning

The analysis of sediments from six wetlands (cienegas) in the Sonoran Desert of Arizona, U.S.A., and Sonora, Mexico, document a marked expansion of wetland taxa-particularly woody plants-about 200 years ago at the beginning of the historic period, following a decrease in charcoal percentages and increased percentages of the dung fungus Sporormiella. The presence of charred seeds and fruits of wetland plants in prehistoric sediment establishes burning of the cienega itself. The charcoal decline ca. 250 years ago precedes the first occurrence of the pollen exotic plants at several sites, the change of cienega sediment from silt to peat, and the increase of percentages of the decay fungus Tetraploa. We conclude that prior to the historic period, burning was frequent enough to exclude most woody plants (Celtis, Cephalanthus, Populus, Fraxinus, Salix) from the wetlands and suppress the abundance of bulrush (Scirpus). The cienegas were probably burned seasonally as a management tool to harvest animals and promote agriculture. Prehistoric agricultural utilization of the cienegas is demonstrated by the presence of corn (Zea) and pre-Columbian weeds. This study also records post-settlement (ca. 200 years ago) change of upland vegetation; i.e. an increase in the abundance of Juniperus, Quercus, Larrea, and Prosopis pollen. Historic fire suppression may have permitted the expansion of these non-wetland woody species. (C) 2002 Elsevier Science Ltd

Voltage-Gated Na+ Channel SCN5A Is a Key Regulator of a Gene Transcriptional Network That Controls Colon Cancer Invasion

Voltage-gated Na(+) channels (VGSCs) have been implicated in the metastatic potential of human breast, prostate and lung cancer cells. Specifically, the SCN5A gene encoding the VGSC isotype Na(v)1.5 has been defined as a key driver of human cancer cell invasion. In this study, we examined the expression and function of VGSCs in a panel of colon cancer cell lines by electrophysiological recordings. Na(+) channel activity and invasive potential were inhibited pharmacologically by tetrodotoxin or genetically by siRNAs specifically targeting SCN5A. Clinical relevance was established by immunohistochemistry of patient biopsies, where there was strong Na(v)1.5 protein staining in colon cancer specimens but little to no staining in matched-paired normal colon tissues. We explored the mechanism of VGSC-mediated invasive potential on the basis of reported links between VGSC activity and gene expression in excitable cells. Probabilistic modeling of loss-of-function screens and microarray data established an unequivocal role of VGSC SCN5A as a high level regulator of a colon cancer invasion network, involving genes that encompass Wnt signaling, cell migration, ectoderm development, response to biotic stimulus, steroid metabolic process and cell cycle control. siRNA-mediated knockdown of predicted downstream network components caused a loss of invasive behavior, demonstrating network connectivity and its function in driving colon cancer invasion

Iodine-129 in Seawater Offshore Fukushima: Distribution, Inorganic Speciation, Sources, and Budget

The Fukushima nuclear accident in March 2011 has released a large amount of radioactive pollutants to the environment. Of the pollutants, iodine-129 is a long-lived radionuclide and will remain in the environment for millions of years. This work first report levels and inorganic speciation of ¹²⁹I in seawater depth profiles collected offshore Fukushima in June 2011. Significantly elevated ¹²⁹I concentrations in surface water were observed with the highest ¹²⁹I/¹²⁷I atomic ratio of 2.2 × 10^–9 in the surface seawater 40 km offshore Fukushima. Iodide was found as the dominant species of ¹²⁹I, while stable ¹²⁷I was mainly in iodate form, reflecting the fact that the major source of ¹²⁹I is the direct liquid discharges from the Fukushima NPP. The amount of ¹²⁹I directly discharged from the Fukushima Dai-ichi nuclear power plant to the sea was estimated to be 2.35 GBq, and about 1.09 GBq of ¹²⁹I released to the atmosphere from the accident was deposited in the sea offshore Fukushima. A total release of 8.06 GBq (or 1.2 kg) of ¹²⁹I from the Fukushima accident was estimated. These Fukushima-derived ¹²⁹I data provide necessary information for the investigation of water circulation and geochemical cycle of iodine in the northwestern Pacific Ocean in the future

Iodine-129 in Seawater Offshore Fukushima: distribution, inorganic speciation, sources, and budget.

The Fukushima nuclear accident in March 2011 has released a large amount of radioactive pollutants to the environment. Of the pollutants, iodine-129 is a long-lived radionuclide and will remain in the environment for millions of years. This work first report levels and inorganic speciation of 129I in seawater depth profiles collected offshore Fukushima in June 2011. Significantly elevated 129I concentrations in surface water were observed with the highest 129I/127I atomic ratio of 2.2 &times; 10&minus;9 in the surface seawater 40 km offshore Fukushima. Iodide was found as the dominant species of 129I, while stable 127I was mainly in iodate form, reflecting the fact that the major source of 129I is the direct liquid discharges from the Fukushima NPP. The amount of 129I directly discharged from the Fukushima Dai-ichi nuclear power plant to the sea was estimated to be 2.35 GBq, and about 1.09 GBq of 129I released to the atmosphere from the accident was deposited in the sea offshore Fukushima. A total release of 8.06 GBq (or 1.2 kg) of 129I from the Fukushima accident was estimated. These Fukushimaderived 129I data provide necessary information for the investigation of water circulation and geochemical cycle of iodine in the northwestern Pacific Ocean in the future.</p