Rare Earth Element Partition Coefficients from Enstatite/Melt Synthesis Experiments

Enstatite (En(80)Fs(19)Wo(01)) was synthesized from a hypersthene normative basaltic melt doped at the same time with La, Ce, Nd, Sm, Eu, Dy, Er, Yb and Lu. The rare earth element concentrations were measured in both the basaltic glass and the enstatite. Rare earth element concentrations in the glass were determined by electron microprobe analysis with uncertainties less than two percent relative. Rare earth element concentrations in enstatite were determined by secondary ion mass spectrometry with uncertainties less than five percent relative. The resulting rare earth element partition signature for enstatite is similar to previous calculated and composite low-Ca pigeonite signatures, but is better defined and differs in several details. The partition coefficients are consistent with crystal structural constraints

Trace element zoning in pelitic garnet of the Black Hills, South Dakota

ABSTRACT Trace element (REE, Cr, Ti, Y, Y, and Zr) analysis of garnet from the garnet, staurolite, and lower sillimanite zones of an aluminous schist of the Black Hills, South Dakota, indicates that REE zoning varies as a function of grade. Garnet-zone garnet has high concentrations of REEs, Cr, Ti, Y, Y, and Zr in the cores and low concentrations in the rims. Profiles of heavy REEs contain inflections between the cores and rims, which are approximately symmetric about the cores. Staurolite-zone garnet contains cores enriched with Y and heavy REEs, which decrease toward the rim and increase again at the rim edges but to lower concentrations than in the cores. Cr, Y, Ti, Zr, and light REE zoning is less pronounced than heavy REE zoning and is less symmetric about the garnet cores. Almandine-rich garnet of the lower sillimanite zone displays no major element zonation. Trace element (Ti, Cr, Y, and Zr) concentrations are minimal, and the zoning is irregular and not symmetric about the garnet cores. Garnet from all three zones has core-to-rim Fe/(Fe + Mg) profiles that suggest garnet growth was uninterrupted with respect to major element components and that Mn zoning formed by a fractionation process. Analysis of trace element zoning in this garnet reveals that the major element zoning was relatively unaffected by volume-diffusion reequilibration. Trace element zonation of all samples of garnet is best explained by a fractionation mechanism in conjunction with limited intergranular diffusion and changing partition coefficients during garnet growth. Heavy REE partitioning is especially dependent on the major element composition of garnet. This research complements previous research by others on the use of trace elements as metamorphic petrogenetic indicators, which demonstrated the importance of bulk-rock composition and phase assemblage on trace element partitioning

Process for Making Single-Domain Magnetite Crystals

A process for making chemically pure, single-domain magnetite crystals substantially free of structural defects has been invented as a byproduct of research into the origin of globules in a meteorite found in Antarctica and believed to have originated on Mars. The globules in the meteorite comprise layers of mixed (Mg, Fe, and Ca) carbonates, magnetite, and iron sulfides. Since the discovery of the meteorite was announced in August 1996, scientists have debated whether the globules are of biological origin or were formed from inorganic materials by processes that could have taken place on Mars. While the research that led to the present invention has not provided a definitive conclusion concerning the origin of the globules, it has shown that globules of a different but related chemically layered structure can be grown from inorganic ingredients in a multistep precipitation process. As described in more detail below, the present invention comprises the multistep precipitation process plus a subsequent heat treatment. The multistep precipitation process was demonstrated in a laboratory experiment on the growth of submicron ankerite crystals, overgrown by submicron siderite and pyrite crystals, overgrown by submicron magnesite crystals, overgrown by submicron siderite and pyrite. In each step, chloride salts of appropriate cations (Ca, Fe, and Mg) were dissolved in deoxygenated, CO2- saturated water. NaHCO3 was added as a pH buffer while CO2 was passed continuously through the solution. A 15-mL aliquot of the resulting solution was transferred into each of several 20 mL, poly(tetrafluoroethylene)-lined hydrothermal pressure vessels. The vessels were closed in a CO2 atmosphere, then transferred into an oven at a temperature of 150 C. After a predetermined time, the hydrothermal vessels were removed from the oven and quenched in a freezer. Supernatant solutions were decanted, and carbonate precipitates were washed free of soluble salts by repeated decantations with deionized water

Search for high-mass diphoton resonances in proton-proton collisions at 13 TeV and combination with 8 TeV search

Peer reviewe

Shared genetic risk between eating disorder- and substance-use-related phenotypes:Evidence from genome-wide association studies

First published: 16 February 202

Laboratory simulation of impacts on aluminum foils of the Stardust spacecraft: Calibration of dust particle size from comet Wild-2

Metallic aluminum alloy foils exposed oil the forward, comet-facing surface of the aerogel tray oil the Stardust spacecraft are likely to have been impacted by the same cometary particle Population as the dedicated impact sensors and the aerogel collector. The ability of soft aluminum alloy to record hypervelocity impacts as bowl-shaped craters offers all opportunistic substrate for recognition of impacts by particles of a potentially wide size range. In contrast to impact surveys conducted oil samples from low Earth orbit, the simple encounter geometry for Stardust and Wild-2, with a known and constant spacecraft-particle relative velocity and effective surface-perpendicular impact trajectories, permits closely comparable simulation in laboratory experiments. For a detailed calibration program, we have selected a suite of spherical glass projectiles of uniform density and hardness characteristics, with well-documented particle size range from 10 mu m to nearly 100 mu m. Light gas gun buckshot firings of these particles at approximately 6 kill s(-1) onto samples of the same foil as employed on Stardust have yielded large numbers of craters. Scanning electron microscopy of both projectiles and impact features has allowed construction of a calibration plot, showing a linear relationship between impacting particle size and impact crater diameter. The close match between our experimental conditions and the Stardust mission encounter parameters should provide another opportunity to measure particle size distributions and Mixes close to the nucleus of Wild-2, independent of the active impact detector instruments aboard the Stardust spacecraft

Identification by Raman spectroscopy of processing effects in forsterite-fayalite samples during hypervelocity impacts on foils and capture in aerogel

The capture of cometary dust grains in aerogel at the well defined impact velocity of 6.1 km/s resulted in the production of a range of impact cavity morphologies. These tracks range from the classical carrot shaped tracks (type A) seen in laboratory experiments with efractory-solid projectiles, to bulbous tracks with “turnip”-like properties and a stylus (type B), to bulbous stubby tracks (type C) [1,2]. These morphologies must reflect the underlying variati on in the structure and strength of cometary dust grains. The cap ture of cometary dust grains also presents the possibility that the chemical content of projec- tiles, in the form of volatiles that are released during capture, also contributed to bulbous track features and analyses of the terminal particles and track residues suggest that the volatile content of the projectiles, released preferentially during capture, would have contributed to the range of morphologies seen in the Stardust cometary dust tracks. An additional contributor to track bulb production could come from par ticle fragmentation during cap-ture and here we present a quantita tive analysis of the factors that contribute to the production of bulbous impact cavities in aerogel

Longitudinal trajectories of BMI z-score: an international comparison of 11,513 Australian, American and German/Austrian/Luxembourgian youth with type 1 diabetes

BACKGROUND:BMI fluctuations during puberty are common. Data on individual change in BMI from childhood to young adulthood are limited in youth with type 1 diabetes. OBJECTIVES:To compare longitudinal trajectories of body mass index z score (BMIz) from childhood to adolescence across three registries spanning five countries. METHODS:Data sources: T1DX (USA), DPV (Germany/Austria/Luxembourg) and ADDN (Australia). The analysis included 11,513 youth with type 1 diabetes, duration >1 year, at least one BMI measure at baseline (age 8-10 years) and >5 aggregated BMI measures by year of age during follow-up until age 17 years. BMIz was calculated based on WHO charts. Latent class growth modelling was used to identify subgroups following a similar trajectory of BMIz over time. RESULTS:Five distinct trajectories of BMIz were present in the T1DX and ADDN cohorts, while six trajectories were identified in the DPV cohort. Boys followed more often a low/near-normal pattern while elevated BMIz curves were more likely in girls (ADDN; DPV). For T1DX cohort, no sex differences were observed. Comparing the reference group (BMIz ~0) with the other groups during puberty, higher BMIz was significantly associated with older age at T1D onset, racial/ethnic minority and elevated HbA1c (all p<0.05). CONCLUSION:This multinational study presents unique BMIz trajectories in youth with T1D across three continents. The prevalence of overweight and the longitudinal persistence of overweight support the need for close monitoring of weight and nutrition in this population. The international and individual differences likely result from diverse genetic, environmental and therapeutic factors.Helen Phelan, Nicole C. Foster, Anke Schwandt, Jennifer J. Couper, Steven Willi, Peter Kroschwald ... et al