Rationale: Micrometeorites are extraterrestrial particles smaller than ~2 mm in diameter, most of which melted during atmospheric entry and crystallised or quenched to form 'cosmic spherules'. Their parentage among meteorite groups can be inferred from triple-oxygen isotope compositions, for example, by secondary ion mass spectrometry (SIMS). This method uses sample efficiently, preserving spherules for other investigations.
View Article and Find Full Text PDFThe isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct from other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI chondrites formed in a different region of the accretion disk, possibly around the orbits of Uranus and Neptune. We show that, like for Fe, Ryugu and CI chondrites also have indistinguishable Ni isotope anomalies, which differ from those of other carbonaceous chondrites. We propose that this unique Fe and Ni isotopic composition reflects different accretion efficiencies of small FeNi metal grains among the carbonaceous chondrite parent bodies.
View Article and Find Full Text PDFThis guideline has been prepared by the ACPSEM to provide a standardised quality assurance program to be used within General X-ray imaging environments. The guideline includes the responsibilities of various multidisciplinary team members within medical imaging facilities. It must be noted that the listed tests and testing frequencies are not intended to replace or become regulatory requirements.
View Article and Find Full Text PDFCharacterization of the elemental distribution of samples with rough surfaces has been strongly desired for the analysis of various natural and artificial materials. Particularly for pristine and rare analytes with micrometer sizes embedded on specimen surfaces, non-invasive and matrix effect-free analysis is required without surface polishing treatment. To satisfy these requirements, we proposed a new method employing the sequential combination of two imaging modalities, i.
View Article and Find Full Text PDFObjectives: To introduce a versatile fabrication process to fabricate zirconia/PMMA composites for chairside CAD/CAM dental restorations. These zirconia composites have nacre-like lamellar microstructures, competent and tooth-matched mechanical properties, as well as crack resistance behaviours.
Methods: Bi-directional freeze casting was used to fabricate ceramic green bodies with highly aligned lamellar structure.
Rare earth elements (REEs) have been found to have numerous uses to trace geological and cosmochemical processes through analyses of elemental patterns, radioactive decay, nucleosynthetic anomalies, and cosmogenic effects. Stable isotopic fractionation is one aspect of REE geochemistry that has been seldom studied, with most publications focusing on the development of analytical methodologies for individual REEs, and most applications concerning terrestrial igneous rocks. In this study, we present a method to systematically analyze stable isotopic fractionations of 8 REEs, including Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb, using sample-standard bracketing (SSB) and double-spike (DS) approaches.
View Article and Find Full Text PDFStudies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform.
View Article and Find Full Text PDFPreliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration.
View Article and Find Full Text PDFThe extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: O-rich (associated with refractory inclusions) and O-poor (associated with chondrules). Both the O-rich and O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward.
View Article and Find Full Text PDFInitial analyses showed that asteroid Ryugu's composition is close to CI (Ivuna-like) carbonaceous chondrites -the chemically most primitive meteorites, characterized by near-solar abundances for most elements. However, some isotopic signatures (e.g.
View Article and Find Full Text PDFThe visible and Mössbauer spectra of [Fe(II)(Por)L] and [Fe(II)(Por)L(CO)] complexes (where Por = protoporphyrin IX (PPIX) or tetra(p-sulfophenyl)porphyrin (TPPS) and L = an aliphatic or aromatic nitrogenous base) are reported and discussed. The results are compared to those of previously reported [Fe(II)(Por)L(CO)] complexes (where Por = PPIX, TPPS, PMXPP, TPP, OMTBP and OEP; L = a nitrogenous aromatic ligand) and HbCO (where Hb = haemoglobin) and MyCO (where My = myoglobin). A new approach, to extracting information from the Mössbauer parameters has been developed by plotting those of the [Fe(II)(Por)L] complexes against those of [Fe(II)(Por)L(CO)] complexes for the same ligands, has yielded a series of trend lines that show a significant dependence on both the nature of the porphyrin and also of the nitrogenous ligand.
View Article and Find Full Text PDFLittle is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids.
View Article and Find Full Text PDFIntroduction: Exposure to gender-based violence (GBV) has devastating psychological outcomes for victims/survivors. Particularly in conditions where GBV intersects with multiple forms of oppression, the negative impacts of violence are more challenging to overcome and potential pathways for recovery become less accessible. However, evidence regarding the availability and effectiveness of mental health interventions for GBV survivors from marginalised and disadvantaged communities has yet to be systematically integrated and synthesised.
View Article and Find Full Text PDFThe indiscriminate biodistribution of therapeutics can be a key barrier to their safety and efficacy. Localization of compounds into non-diseased tissues often leads to both toxic and dose-limiting effects. To overcome this barrier, nanomedicine implements targeting agents to localize or selectively uptake drugs at disease sites.
View Article and Find Full Text PDFCarbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples.
View Article and Find Full Text PDFIn this work, we investigate the synthesis of (LaSr)MnO (LSM) in various molten salts to gain insight on the influence of molten salt ions for synthesizing materials critical for energy applications. LSM nanoparticles with a size range of ∼10-200 nm and with target stoichiometries were formed from oxide precursors feeding into KNO. Furthermore, feeding precursors into the melt compared to mixing and heating from room temperature results in complete formation of LSM that was otherwise unattainable using conventional molten salt synthesis methods.
View Article and Find Full Text PDFStudies are reported on the formation of low-spin six-coordinate [Fe(PPIX)L] complexes from iron(II) protoporphyrin where L is one of a series of nitrogenous ligands (aliphatic, aromatic or heterocyclic). The bonding constants have been determined by titration of the metal complex with these ligands and are compared in relation to previous studies. The adduct formation was monitored utilising optical spectroscopy.
View Article and Find Full Text PDFThe Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sample location.
View Article and Find Full Text PDFObjective To assess factors affecting willingness to pay for orthodontic treatment.Methods An online discrete choice experiment and willingness to pay study was conducted on a convenience sample of 250 participants aged 16 and above over a four-month period. Participants completed a series of stated-preference tasks, in which they viewed choice sets with two orthodontic treatment options involving different combinations of attributes: family income; cost to patient; cause of problem; prevention of future problems; age; severity of the problem; and self-esteem/confidence.
View Article and Find Full Text PDFObjectives To determine the priorities of patients and dental professionals concerning NHS dental treatments, the factors influencing prioritisation and the willingness to contribute towards the cost of NHS dental treatments.Methods Focus groups and interviews involving patients and practitioners informed the development of a piloted questionnaire concerning the priorities for NHS dental treatments. Patients attending three purposively selected dental settings in London and Kent, as well as dental professionals working within a large London dental hospital were recruited to participate in this initial qualitative phase.
View Article and Find Full Text PDFEquilibrium condensation of solar gas is often invoked to explain the abundance of refractory elements in planets and meteorites. This is partly motivated, by the observation that the depletions in both the least and most refractory rare earth elements (REEs) in meteoritic group II calcium-aluminum-rich inclusions (CAIs) can be reproduced by thermodynamic models of solar nebula condensation. We measured the isotopic compositions of Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb in eight CAIs to test this scenario.
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