Dating of mortar and bricks from the Castle of Kastelholm

In connection with the excavation and restauration works at Kastelholm radiocarbon dating of mortar from the walls of the castle has been attempted. Except for a date clearly affected by old carbonate and a few samples of modern age, the calibrated samples date back to the 14th century. Four bricks from different parts of the tower of the castle dated by the thermoluminescence method gave ages between 1490 and 1600 AD. The TL measurements are made on feldspar inclusions extracted from the bricks. The dating results are in agreement with those from the archaeological investigations

First direct dating of Late Pleistocene ice-wedges by AMS

We present the first direct dating by C-14-accelerator mass spectrometry of three Late Pleistocene syngenetic ice-wedges from the Seyaha cross-section. They are representative of permafrost with multistage ice-wedges from the North of Western Siberia. The most important result is the clear vertical age stratification of the ice, i.e. the old ice is located beneath the young. This shows that a timescale can be assigned to these ice-wedges penetrating down into the permafrost. The age of the ice shows a depth of not more than 3-5 m for frost cracking; water penetrated into the ice-wedges at that depth. The lower part of the ice-wedges from the Seyaha cross-section has been dated between 21 000 and 14 000 BP. (C) 2000 Elsevier Science B.V. All rights reserved

Spatio‐temporal patterns of tree growth as related to carbon isotope fractionation in European forests under changing climate

Aim To decipher Europe-wide spatiotemporal patterns of forest growth dynamics and their associations with carbon isotope fractionation processes inferred from tree rings as modulated by climate warming. Location Europe and North Africa (30‒70°N, 10°W‒35°E). Time period 1901‒2003. Major taxa studied Temperate and Euro-Siberian trees. Methods We characterize changes in the relationship between tree growth and carbon isotope fractionation over the 20th century using a European network consisting of 20 site chronologies. Using indexed tree-ring widths (TRWi), we assess shifts in the temporal coherence of radial growth across sites (synchrony) for five forest ecosystems (Atlantic, Boreal, cold continental, Mediterranean and temperate). We also examine whether TRWi shows variable coupling with leaf-level gas exchange, inferred from indexed carbon isotope discrimination of tree-ring cellulose (Δ13Ci). Results We find spatial autocorrelation for TRWi and Δ13Ci extending over up to 1,000 km among forest stands. However, growth synchrony is not uniform across Europe, but increases along a latitudinal gradient concurrent with decreasing temperature and evapotranspiration. Latitudinal relationships between TRWi and Δ13Ci (changing from negative to positive southwards) point to drought impairing carbon uptake via stomatal regulation for water saving occurring at forests below 60°N in continental Europe. A rise in forest growth synchrony over the 20th century together with increasingly positive relationships between TRWi and Δ13Ci indicate intensifying drought impacts on tree performance. These effects are noticeable in drought-prone biomes (Mediterranean, temperate and cold continental). Main conclusions At the turn of this century, convergence in growth synchrony across European forest ecosystems is coupled with coordinated warming-induced drought effects on leaf physiology and tree growth spreading northwards. Such a tendency towards exacerbated moisture-sensitive growth and physiology could override positive effects of enhanced leaf intercellular CO2 concentrations, possibly resulting in Europe-wide declines of forest carbon gain in the coming decades

Effect of methylene blue on the genomic response to reperfusion injury induced by cardiac arrest and cardiopulmonary resuscitation in porcine brain

<p>Abstract</p> <p>Background</p> <p>Cerebral ischemia/reperfusion injury is a common secondary effect of cardiac arrest which is largely responsible for postresuscitative mortality. Therefore development of therapies which restore and protect the brain function after cardiac arrest is essential. Methylene blue (MB) has been experimentally proven neuroprotective in a porcine model of global ischemia-reperfusion in experimental cardiac arrest. However, no comprehensive analyses have been conducted at gene expression level.</p> <p>Methods</p> <p>Pigs underwent either untreated cardiac arrest (CA) or CA with subsequent cardiopulmonary resuscitation (CPR) accompanied with an infusion of saline or an infusion of saline with MB. Genome-wide transcriptional profiling using the Affymetrix porcine microarray was performed to 1) gain understanding of delayed neuronal death initiation in porcine brain during ischemia and after 30, 60 and 180 min following reperfusion, and 2) identify the mechanisms behind the neuroprotective effect of MB after ischemic injury (at 30, 60 and 180 min).</p> <p>Results</p> <p>Our results show that restoration of spontaneous circulation (ROSC) induces major transcriptional changes related to stress response, inflammation, apoptosis and even cytoprotection. In contrast, the untreated ischemic and anoxic insult affected only few genes mainly involved in intra-/extracellular ionic balance. Furthermore, our data show that the neuroprotective role of MB is diverse and fulfilled by regulation of the expression of soluble guanylate cyclase and biological processes accountable for inhibition of apoptosis, modulation of stress response, neurogenesis and neuroprotection.</p> <p>Conclusions</p> <p>Our results support that MB could be a valuable intervention and should be investigated as a therapeutic agent against neural damage associated with I/R injury induced by cardiac arrest.</p

An Improvement in Preparation of Mortar for Radiocarbon Dating

From the 17th International Radiocarbon Conference held in Jerusalem, Israel, June 18-23, 2000.An error source in radiocarbon dating of ancient mortar is dead carbon of limestone mixed in the matrix. To eliminate the influence of limestone the difference in feasibility to react with acid between mortar and limestone is used. Since the rate of reaction depends on grain size use of a well-defined grain size can give a better separation between mortar and limestone. We present results for the grain size dependence of reaction rates for several mortar and limestone samples and discuss the application for dating.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