73 research outputs found

    Bright Stuff on Ceres = Sulfates and Carbonates on CI Chondrites

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    Recent reports of the DAWN spacecraft's observations of the surface of Ceres indicate that there are bright areas, which can be explained by large amounts of the Mg sulfate hexahydrate (MgSO46(H2O)), although the identification appears tenuous. There are preliminary indications that water is being evolved from these bright areas, and some have inferred that these might be sites of contemporary hydro-volcanism. A heat source for such modern activity is not obvious, given the small size of Ceres, lack of any tidal forces from nearby giant planets, probable age and presumed bulk composition. We contend that observations of chondritic materials in the lab shed light on the nature of the bright spots on Cere

    Fluid Inclusions in Astromaterials: Direct Samples of Early Solar System Aqueous Fluids

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    We have become increasingly aware of the fundamental importance of water, and aqueous alteration, on primitive solar-system bodies. All classes of astromaterials studied show some degree of interaction with aqueous fluids. We have direct observations of cryovolcanism of several small solar system bodies (e.g. Saturnian and Jovian moons), and indirect evidence for this process on the moons Europa, Titan, Ganymede, and Miranda, and the Kuiper Belt object Charon, and so are certain of the continuing and widespread importance of aqueous processes across the solar system. Nevertheless, we are still lacking fundamental information such as the location and timing of the aqueous alteration and the detailed nature of the aqueous fluid itself

    Measurements of Shock Effects Recorded by Hayabusa Samples

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    We requested and have been approved for 5 Hayabusa samples in order definitively establish the degree of shock experienced by the regolith of asteroid Itokawa, and to devise a bridge between shock determinations by standard light optical petrography, crystal structures as determined by synchrotron X-ray diffraction (SXRD), and degree of crystallinity as determined by electron back-scattered diffraction (EBSD) [1,2]. As of the writing of this abstract we are awaiting the approved samples. We propose measurements of astromaterial crystal structures and regolith processes. The proposed research work will improve our understanding of how small, primitive solar system bodies formed and evolved, and improve understanding of the processes that determine the history and future of habitability of environments on other solar system bodies. The results of the proposed research will directly enrich the ongoing asteroid and comet exploration missions by NASA, JAXA and ESA, and broaden our understanding of the origin and evolution of small bodies in the early solar system, and elucidate the nature of asteroid and comet regolith

    One-pot synthesis of amino acid precursors with insoluble organic matter in planetesimals with aqueous activity

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    We report that the water-soluble amino acid precursors are synthesized from formaldehyde, glycolaldehyde, and ammonia with the presence of liquid water, simultaneously with macromolecular organic solids similar to the chondritic IOM. Amino acid products from hydrothermal experiments after acid hydrolysis include α-, ÎČ-, and Îł-amino acids up to five carbons, for which relative abundances are similar to those extracted from carbonaceous chondrites. One-pot aqueous processing from simple ubiquitous molecules can thus produce a wide variety of meteoritic organic matter from amino acid precursors to macromolecular IOM in chondrite parent bodies.Yoko Kebukawa, Queenie H. S. Chan, Shogo Tachibana, Kensei Kobayashi and Michael E. Zolensk

    A D- and N-15-Rich Micrometer-Sized Aggregate of Organic Matter in a Xenolithic Clast from the Zag Ordinary Chondrite

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    The nature and origin of extraterrestrial organic matter are still under debate despite the significant progress in the analyses and experimental approaches in this field over the last five decades. Xenolithic clasts are often found in a wide variety of meteorite groups, some of which contain exotic organic matter (OM). The Zag meteorite is a thermally-metamorphosed H ordinary chondrite. It contains a primitive xenolithic clast that has been proposed to have originated from Ceres, which was accreted to the Zag host asteroid after metamorphism. The cm-sized clast contains abundant large carbon-rich (mostly organic) grains or aggregates up to 20 microns. Such large OM grains are unique among astromaterials with respect to the size. Here we report organic and isotope analyses of a large (approx.10 microns) aggregate of solid OM in the Zag clast. The X-ray micro-spectroscopic technique revealed that the OM has sp2 bonded carbon with no other functional groups nor graphitic feature (1s-sigma exciton), and thus it is distinguished from most of the OM in carbonaceous meteorites. The apparent absence of functional groups in the OM suggests that it is composed of hydrocarbon networks with less heteroatoms, and therefore the OM aggregate is similar to hydrogenated amorphous carbon (HAC). The OM aggregate has high D/H and 15N/14N ratios, suggesting that it originated in a very cold environment such as the interstellar medium or outer region of the solar nebula, while the OM is embedded in carbonate-bearing matrix resulting from aqueous activities. Thus the high D/H ratio must have survived the extensive late-stage aqueous processing. It is not in the case for OM in carbonaceous chondrites of which the D/H ratio was reduced by the alteration via the D-H exchange of water. It indicates that both the OM precursors and the water had high D/H ratios, similar to the water in Enceladus. Our results support the idea that the clast originated from Ceres, or at least, a hydrovolcanically active body similar to Ceres, and further imply that Ceres originally formed in the outer Solar System and migrated to the main belt asteroid region as suggested by the "Grand tack" scenario

    Characterising frailty, metrics of continuous glucose monitoring, and mortality hazards in older adults with type 2 diabetes on insulin therapy (HARE) : a prospective, observational cohort study

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    SummaryBackground: To our knowledge, no previous study has examined the inter-relationship between frailty, dysglycaemia, and mortality in frail older adults with type 2 diabetes who are on insulin therapy. We used continuous glucose monitors (CGMs) to profile this patient population and determine the prognostic value of CGM metrics. We hypothesised that incremental frailty was associated with increased hypoglycaemia or time below range (TBR).Methods: HARE was a multicentre, prospective, observational cohort study with mortality hazard analysis carried out in four hospitals in Hong Kong. Eligible participants were community-living adults aged 70 years and older; had had type 2 diabetes for 5 years or more; were on insulin therapy; were frail; and were not hospitalised at the time of frailty assessment and CGM recording. Glucose control was characterised according to the Advanced Technologies and Treatments for Diabetes 2019 international consensus clinical targets. Frailty index was computed, and comprehensive frailty assessments and targeted serum metabolic profiling were performed. The Jonckheere-Terpstra test for trend was used to analyse frailty index tertiles and variables. Inter-relationships between CGM metrics and frailty, glycated haemoglobin A1c (HbA1c), and serum albumin were characterised using adjusted regression models. Survival analysis and Cox proportional hazard modelling were performed.Findings: Between July 25, 2018, and Sept 27, 2019, 225 participants were recruited, 222 of whom had CGMs fitted and 215 of whom had analysable CGM data (190 were frail, 25 were not frail). Incremental frailty was associated with older age, greater HbA1c, worse renal function, and history of stroke. Eight of 11 CGM metrics were significantly associated with frailty. Decreased time in range (TIR; glucose concentration 3·9–10·0 mmol/L) and increased time above range (TAR) metrics were strongly correlated with increased frailty and hyperglycaemia, whereas TBR metrics were marginally or not different between frailty levels. Glucose-lowering agents did not significantly affect regression estimates. In patients with HbA1c of 7·5% or more, reduced serum albumin was associated with level 2 TAR (glucose concentration >13·9 mmol/L) and dysglycaemia. During a median follow-up of 28·0 months (IQR 25·3–30·4), increased level 2 TAR was predictive of mortality explainable by frailty in the absence of detectable interaction. Each 1% increment of level 2 TAR was associated with 1·9% increase in mortality hazard.Interpretation: In older adults with type 2 diabetes who are on insulin therapy, incremental frailty was associated with increased dysglycaemia and hyperglycaemia rather than hypoglycaemia. Mortality hazard was increased with severe hyperglycaemia. Future clinical studies and trials targeting actionable CGM metrics highlighted in this study could translate into improved care and outcomes.Funding: Health and Medical Research Fund, Food and Health Bureau, The Government of the Hong Kong Special Administrative Region of China.Summary Background: To our knowledge, no previous study has examined the inter-relationship between frailty, dysglycaemia, and mortality in frail older adults with type 2 diabetes who are on insulin therapy. We used continuous glucose monitors (CGMs) to profile this patient population and determine the prognostic value of CGM metrics. We hypothesised that incremental frailty was associated with increased hypoglycaemia or time below range (TBR). Methods: HARE was a multicentre, prospective, observational cohort study with mortality hazard analysis carried out in four hospitals in Hong Kong. Eligible participants were community-living adults aged 70 years and older; had had type 2 diabetes for 5 years or more; were on insulin therapy; were frail; and were not hospitalised at the time of frailty assessment and CGM recording. Glucose control was characterised according to the Advanced Technologies and Treatments for Diabetes 2019 international consensus clinical targets. Frailty index was computed, and comprehensive frailty assessments and targeted serum metabolic profiling were performed. The Jonckheere-Terpstra test for trend was used to analyse frailty index tertiles and variables. Inter-relationships between CGM metrics and frailty, glycated haemoglobin A1c (HbA1c), and serum albumin were characterised using adjusted regression models. Survival analysis and Cox proportional hazard modelling were performed. Findings: Between July 25, 2018, and Sept 27, 2019, 225 participants were recruited, 222 of whom had CGMs fitted and 215 of whom had analysable CGM data (190 were frail, 25 were not frail). Incremental frailty was associated with older age, greater HbA1c, worse renal function, and history of stroke. Eight of 11 CGM metrics were significantly associated with frailty. Decreased time in range (TIR; glucose concentration 3·9–10·0 mmol/L) and increased time above range (TAR) metrics were strongly correlated with increased frailty and hyperglycaemia, whereas TBR metrics were marginally or not different between frailty levels. Glucose-lowering agents did not significantly affect regression estimates. In patients with HbA1c of 7·5% or more, reduced serum albumin was associated with level 2 TAR (glucose concentration >13·9 mmol/L) and dysglycaemia. During a median follow-up of 28·0 months (IQR 25·3–30·4), increased level 2 TAR was predictive of mortality explainable by frailty in the absence of detectable interaction. Each 1% increment of level 2 TAR was associated with 1·9% increase in mortality hazard. Interpretation: In older adults with type 2 diabetes who are on insulin therapy, incremental frailty was associated with increased dysglycaemia and hyperglycaemia rather than hypoglycaemia. Mortality hazard was increased with severe hyperglycaemia. Future clinical studies and trials targeting actionable CGM metrics highlighted in this study could translate into improved care and outcomes. Funding: Health and Medical Research Fund, Food and Health Bureau, The Government of the Hong Kong Special Administrative Region of China
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