The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T

Objectives To measure mercury release from standardised hydroxyapatite/amalgam constructs during MRI scanning and investigate the impact of static field strength and radiofrequency (RF) power on mercury release. Methods Amalgam was placed into 140 hydroxyapatite disks and matured for 14-days in artificial saliva. The solution was replaced, and samples split into five groups of 28 immediately prior to MRI. One group had no exposure, and the remainder were exposed to either a 3T or 7T MRI scanner, each at high and low RF power. Mercury concentration was measured by inductively coupled plasma mass spectrometry. Groups were compared using one-way ANOVA, and two-way ANOVA for main effects/ interaction of field strength/ RF power. Results Mercury concentration was increased in the 7T groups (high/ low: 15.43/ 11.33 ng mL−1) and 3T high group (3.59) compared to control (2.44). MRI field strength significantly increased mercury release (p < .001) as did RF power (p = .030). At 3T, mercury release was 20.3 times lower than during maturation of dental amalgam, and for the average person an estimated 1.50 ng kg−1 of mercury might be released during one 3T investigation; this is substantially lower than the tolerable weekly intake of 4,000 ng kg−1. Conclusion Mercury release from amalgam shows a measurable increase following MRI, and the magnitude changes with magnetic field strength and RF power. The amount of mercury released is small compared to release during amalgam maturation. Amalgam mercury release during MRI is unlikely to be clinically meaningful and highly likely to remain below safe levels

At the world's edge: Reconstructing diet and geographic origins in medieval Iceland using isotope and trace element analyses

Objectives A multi‐isotope study was conducted on individuals buried at Skriðuklaustur monastery (AD 1493–1554) to investigate their geographic origins and dietary composition. Comparative material from individuals excavated from Skeljastaðir, an inland farm site was also analyzed. Materials and methods Bone collagen was extracted from 50 humans (Skriðuklaustur and Skeljastaðir) and 25 animals (Skriðuklaustur) and analyzed for δ13C, δ15N, and δ34S. Dental enamel samples from 31 individuals (Skriðuklaustur) were also analyzed for 87Sr/86Sr, δ18O, δ13C, and trace elements (Pb, Sr, Zn, Ba). Results The mean value determined from individuals from Skriðuklaustur (n = 36) was δ13C = −18.7 ± 0.8‰, δ15N = 12.8 ± 1.1‰, and δ34S = 9.0 ± 1.6‰, whereas at Skeljastaðir (n = 14), it was δ13C = −20.5 ± 0.8‰, δ15N = 7.8 ± 0.9‰, and δ34S = 9.4 ± 1.6‰. At Skriðuklaustur, human dental enamel samples (n = 31) provided a 87Sr/86Sr range of 0.7060–0.7088, δ18Ophosphate from 13.9 to 16.1‰ and δ13Ccarbonate from −16.6 to −12.9‰. Inferred drinking water (δ18Odw) values range from −12.3 to −8.9‰. Sr concentrations range from 25.8 to 156.7 ppm, Ba from 0.11 to 0.81 ppm, Zn from 43.8 to 145.8 ppm, and Pb from 0.13 to 9.40 ppm. Discussion A combination of results indicates that the people from Skriðuklaustur were born in Iceland, but some lived inland during childhood while others lived closer to the coast. Since Skriðuklaustur was a hospital, these individuals may have sought medical treatment at the monastery. The δ13C and δ15N values determined from bone collagen indicate that the people residing at Skriðuklaustur consumed a diet high in marine protein, while those residing at Skeljastaðir exhibit values more consistent with terrestrial resources.This research was financed by Fornminjasjóður (the Archaeology Fund), Háskólasjóður Eimskipafélags Íslands (the Eimskip University Fund), and the Stable Isotope Biogeochemistry Laboratory (SIBL).Peer Reviewe

Characterization of Lubricant Degeneration and Component Deterioration on Diesel Engine Fueling with Straight Plant Oil

Straight Plant Oils (SPOs) are promising alternatives to diesel fuel in some particular applications, e.g. electrification in remote areas and sustainable modernization of artisan fishing vessels. Moderate commercialization of SPOs is yet to be realized due to lack of critical information on engine durability, lubricant degeneration, and effective methods to offset the adverse effect of directly using SPOs on diesel engines. In this paper, the experimental study evaluates the long term impacts of crude Jatropha oil (JO) on a small diesel engine generator through 300 hour durability tests. The testing results demonstrate the evolution of gaseous emissions, the trace metal element variations in lubricant, and the carbon deposit formation on engine components. The associated fuel spray experiments in the controlled environment further reveal JO atomization patterns and provide important evidence to interpret why JO has greater influence on engine durability than diesel

Adakites without a slab: Remelting of hydrous basalt in the crust and shallow mantle of Borneo to produce the Miocene Sintang Suite and Bau Suite magmatism of West Sarawak

We present new geochronological and geochemical data for Neogene magmatism from West Sarawak. Zircon U-Pb geochronology divides Neogene magmatic rocks of West Sarawak into a Lower Miocene West Sarawak Sintang Suite with ages of c. 19 to 21 Ma, and a Middle Miocene Bau Suite with ages of c. 12 to 14 Ma. Magmatism occurred in multiple short-lived pulses from approximately 24 Ma and was coeval with magmatic activity in NW Kalimantan and East Kalimantan. The majority of, but not all, Bau Suite samples display adakitic chemistry, while the West Sarawak Sintang Suite is predominantly non-adakitic. There was no active subduction zone or subducted slab associated with this adakitic magmatism. Instead, the geochemical diversity is consistent with the Bau and West Sarawak Sintang suites representing mixtures of mafic, mantle-derived magma with felsic magma derived from remelting of hydrous, mafic rock that had been emplaced into the lithosphere of Borneo as arc basalt tens or hundreds of millions of years previously. This origin is most evident in the main Sintang Suite of central Borneo (Kalimantan) which has preserved less contaminated examples of the mafic endmember. This endmember resembles basaltic rocks from several locations across Borneo suggesting that intraplate, mantle-derived magmatism was responsible for remelting older, hydrated basaltic rocks in the crust

Lilypad aggregation: localised self-assembly and metal sequestration at a liquid-vapour interface

Spatially resolved soft materials, such as vesicles and microgels, have shown promise as selective adsorbents and microscale reaction vessels. However, spatiotemporal control of aggregation can be difficult to achieve. In this study, nickel(II) chloride and a dipyridyl oligo(urea) ligand were combined in a vapour-diffusion setup to produce a localised spheroidal aggregate at the liquid–vapour interface. This aggregate forms via the self-assembly and fusion of monodisperse colloids and grows until its weight is no longer counterbalanced by surface tension. A simple physical model reveals that this process, termed lilypad aggregation, is possible only for surface energies that favour neither bulk aggregation nor the growth of an interfacial film. These surface energies dictate the final size and shape of the aggregate and may be estimated through visual monitoring of its changing morphology. Lilypad aggregates sequester metal from the surrounding sol and can be collected manually from the surface of the liquid

Arc-related harzburgite-dunite-chromitite complexes in the mantle section of the Sabzevar ophiolite, Iran : a model for formation of podiform chromitites

Podiform chromitites are common within the mantle section of the Late Cretaceous Sabzevar ophiolite in NE Iran. We studied chromitite pods and related ultramafic rocks from three Sabzevar massifs: Baghjar-Kuh Siah, Gaft Chromitite Mine and Forumad peridotite-chromitite. These represent an upper mantle sequence just below the Sabzevar Moho. The Baghjar-Kuh Siah mantle sequence contains plagioclase lherzolites, enriched in bulk REEs, with low Cr# spinels and MORB-like clinopyroxenes. These lherzolites formed due to the impregnation of MORB-like melts. The Gaft and Forumad harzburgites are depleted in trace and rare earth elements and thus are residues after high degree of partial melting (more than exhaustion of Cpx). The Gaft Chromitite Mine includes two types of podiform chromitites, high Cr# and low Cr#. The melt precipitating high Cr# spinel was boninitic whereas the melt forming the low Cr# chromitites was tholeiitic. Most Forumad massif chromitites have high Cr# spinels, although those rich in silicate inclusions are aluminous. Trace and REE element patterns of Forumad harzburgite clinopyroxene are similar to those in supra-subduction zone (SSZ) peridotites while those of Baghjar-Kuh Siah lherzolites are similar to MOR peridotite clinopyroxenes. These mineral data are also consistent with bulk rock trace and rare earth elements composition of their host peridotites. Field observations indicate that early tholeiitic magmas were followed by late boninites, as revealed in chromitite compositions as well as mantle rocks and dikes. We suggest a time-integrated model for the evolution of the Sabzevar mantle sequence during an early stage of subduction initiation associated with formation of an incipient arc. In this scenario, MORB-like melts (forearc basalts) formed first, causing low Cr# chromitites and plagioclase-clinopyroxene impregnations. Subsequent arc-like or boninitic melts with increasing contribution of slab-derived fluids were responsible for the formation of replacive dunites and high Cr# chromitites.19 page(s

Coexistence of abyssal and ultra-depleted SSZ type mantle peridotites in a Neo-Tethyan Ophiolite in SW Turkey: Constraints from mineral composition, whole-rock geochemistry (major–trace–REE–PGE), and Re–Os isotope systematic.

We present new, whole-rock major and trace element chemistry, including rare earth elements (REE), platinum-group elements (PGE), and Re-Os isotope data from the upper mantle peridotites of a Cretaceous Neo-Tethyan ophiolite in the Mu\u1e7la area in SW Turkey. We also report extensive mineral chemistry data for these peridotites in order to better constrain their petrogenesis and tectonic environment of formation. The Mu\u1e7la peridotites consist mainly of cpx-harzburgite, depleted harzburgite, and dunite. Cpx-harzburgites are characterized by their higher average CaO (2.27wt.%), Al 2O 3 (2.07wt.%), REE (53ppb), and 187Os/ 188Os (i) ratios varying between 0.12497 and 0.12858. They contain Al-rich pyroxene with lower Cr content of coexisting spinel (Cr#=13-22). In contrast, the depleted harzburgites and dunites are characterized by their lower average CaO (0.58wt.%), Al 2O 3 (0.42wt.%), and REE (1.24ppb) values. Their clinopyroxenes are Al-poor and coexist with high-Cr spinel (Cr#=33-83). The 187Os/ 188Os (i) ratios are in the range of 0.12078-0.12588 and are more unradiogenic compared to those of the cpx-harzburgites.Mineral chemistry and whole rock trace and PGE data indicate that formation of the Mu\u1e7la peridotites cannot be explained by a single stage melting event; at least two-stages of melting and refertilization processes are needed to explain their geochemical characteristics. Trace element compositions of the cpx-harzburgites can be modeled by up to ~. 10-16% closed-system dynamic melting of a primitive mantle source, whereas those of the depleted harzburgites and dunites can be reproduced by ~. 10-16% open-system melting of an already depleted (~. 16%) mantle. These models indicate that the cpx-harzburgites are the products of first-stage melting and low-degrees of melt-rock interaction that occurred in a mid-ocean ridge (MOR) environment. However, the depleted harzburgites and dunites are the product of second-stage melting and related refertilization which took place in a supra subduction zone (SSZ) environment. The Re-Os isotope systematics of the Mu\u1e7la peridotites gives model age clusters of ~. 250. Ma, ~. 400. Ma and ~. 750. Ma that may record major tectonic events associated with the geodynamic evolution of the Neo-Tethyan, Rheic, and Proto-Tethyan oceans, respectively. Furthermore, > 1000. Ma model ages can be interpreted as a result of an ancient melting event before the Proto-Tethys evolution