Anomalous supply of bioessential molybdenum in mid-Proterozoic surface environments

We are grateful to A. Sandison and W. Thayalon for skilled technical support, and Mike Porter and an anonymous reviewer, who helped to clarify the manuscript.Peer reviewedPostprin

Serpentinisation of Chondrules in the Murchison Cm Carbonaceous Chondrite by Centripetal Replacement and Cementation [abstract]

No abstract available

4.6 billion year old aragonite and its implications for understanding the geological record of Ca-carbonate

Owing to its diagenetic instability, aragonite is rare in the geological record and almost entirely absent from pre-carboniferous sedimentary rocks. The former presence of this mineral in older deposits has to be inferred from petrographic, chemical or isotopic proxies. Crystals of aragonite that formed around 4563 million years ago occur in carbonaceous chondrite meteorites, showing that under certain conditions, the orthorhombic polymorph of Ca-carbonate can survive essentially indefinitely. Together with other carbonate minerals, phyllosilicates and sulphides, this aragonite formed by low-temperature water-mediated alteration of anhydrous minerals and glass in the interior of the meteorite’s parent asteroid(s). The survival of aragonite for such a long time can be attributed to the loss of free water by its incorporation into phyllosilicates, and to the very low permeability of the fine-grained and organic-rich rock matrix that prevented the ingress of fresh solutions via intergranular flow. By analogy with these meteorites, terrestrial aragonite is likely to survive where it has been similarly isolated from liquid water, particularly in organic-rich mudrocks, and such deposits may provide important new evidence for deducing the original mineralogy of skeletal and non-skeletal carbonates in deep-time

Exploring Thermal Processing of the Mildly Aqueously Altered Cm2 Eet 96029 Using Sulphide Mineralogy and Carbon Structure [abstract]

No abstract available

Enhanced microbial activity in carbon-rich pillow lavas, Ordovician, Great Britain and Ireland

Date of acceptance: 09/07/2015 ACKNOWLEDGEMENTS A. Sandison and C. Taylor provided skilled technical support. Boyce is funded by Natural Environment Research Council (NERC) support of the Isotope Community Support Facility at the Scottish Universities Environmental Research Centre. NERC supported the project through facility grant IP-1235- 0511. The Raman spectroscopy facility at the University of Aberdeen is funded by the Biotechnology and Biological Sciences Research Council. We are grateful to M. Feely, G. Purvis, and an anonymous reviewer for helpful criticism.Peer reviewedPostprin

The Origin of Iddingsite Veins in Olivine from the Nakhlite Meteorites:New Insights from Analogy with CM Carbonaceous Chondrites and Terrestrial Basalts

The nakhlite meteorites are samples of a ~1300 million year old martian clinopyroxenite lava flow or sill [1, 2]. These rocks contain secondary minerals including hydrous silicates, carbonates, sulphates and Fe-(hydr)oxides that formed by watermediated alteration of the igneous body [3, 4]. A prerequisite for understanding the nature of the aqueous system from which these minerals formed, including water/rock ratio, the provenance of solutes and its longevity, is knowing whether the secondary minerals formed by replacement of primary igneous components (minerals and glasses), or by cementation of pores that were opened by fracturing. A replacive origin would suggest low water/rock ratios with solutions being close to saturation with respect to secondary minerals, and does not require a pre-existing network of pores for fluids to gain access to mineral grain interiors. An origin by cementation would suggest that solutes had been sourced by dissolution of other parts of the nakhlite parent rock or the martian crust and were introduced by fluid flow under relatively high water/rock ratio conditions; a means of fracturing the rock is also required.<p></p> Here we have sought to answer the question of whether olivine-hosted veins in the nakhlites formed by cementation or replacement by comparing the microstructures of veins in the nakhlite Lafayette with veins in olivine grains from type I chondrules in Murchison (CM2 carbonaceous chondrite). We also draw on previously published work on ‘iddingsite’ veins in olivine from terrestrial basalts.<p></p&gt

Education as a moderator of middle-age cardiovascular risk factor-old-age cognition relationships : testing cognitive reserve hypothesis in epidemiological study

Background higher educational attainment and less midlife cardiovascular risk factors are related to better old-age cognition. Whether education moderates the association between cardiovascular risk factors and late-life cognition is not known. We studied if higher education provides resilience against the deteriorative effects of higher middle-age body mass index (BMI) and a combination of midlife cardiovascular risk factors on old-age cognition. Methods the study population is the older Finnish Twin Cohort (n = 4,051, mean age [standard deviation, SD] = 45.5 years [6.5]). Cardiovascular risk factors and education were studied at baseline with questionnaires in 1975, 1981 and/or 1990 (participation rates of 89, 84 and 77%, respectively). Cognition was evaluated with telephone interviews (participation rate 67%, mean age [SD] =73.4 [2.9] years, mean follow-up [SD] = 27.8 [6.0] years) in 1999-2017. We studied the main and interactive effects of education and BMI/dementia risk score on late-life cognition with linear regression analysis. The study design was formulated before the pre-defined analyses. Results years of education moderated the association between BMI with old-age cognition (among less educated persons, BMI-cognition association was stronger [B = -0.24 points per BMI unit, 95% CI -0.31, -0.18] than among more educated persons [B = -0.06 points per BMI unit, 95% CI -0.16, 0.03], P-interaction < 0.01). There was a similar moderating effect of education on dementia risk score consisting of cardiovascular risk factors (P < 0.001). Conclusions our results support the cognitive reserve hypothesis. Those with higher education may tolerate the deteriorative effects of midlife cardiovascular risk factors on old-age cognition better than those with lower education.Peer reviewe

Middle-age dementia risk scores and old-age cognition : a quasi-experimental population-based twin study with over 20-year follow-up

Background Middle-age risk scores predict cognitive impairment, but it is not known if these associations are evident when controlling for shared genetic and environmental factors. Using two risk scores, self-report educational-occupational score and Cardiovascular Risk Factors, Aging and Dementia (CAIDE), we investigated if twins with higher middle-age dementia risk have poorer old-age cognition compared with their co-twins with lower risk. Methods We used a population-based older Finnish Twin Cohort study with middle-age questionnaire data (n=15 169, mean age=52.0 years, SD=11.8) and old-age cognition measured via telephone interview (mean age=74.1, SD=4.1, n=4302). Between-family and within-family linear regression analyses were performed. Results In between-family analyses (N=2359), higher educational-occupational score was related to better cognition (B=0.76, 95% CI 0.69 to 0.83) and higher CAIDE score was associated with poorer cognition (B=-0.73, 95% CI -0.82 to -0.65). Within twin-pair differences in educational-occupational score were significantly related to within twin-pair differences in cognition in dizygotic (DZ) pairs (B=0.78, 95% CI 0.25 to 1.31; N=338) but not in monozygotic (MZ) pairs (B=0.12, 95% CI -0.44 to 0.68; N=221). Within twin-pair differences in CAIDE score were not related to within twin-pair differences in cognition: DZ B=-0.38 (95% CI -0.90 to 0.14, N=343) and MZ B=-0.05 (95% CI -0.59 to 0.49; N=226). Conclusion Middle-age dementia risk scores predicted old-age cognition, but within twin-pair analyses gave little support for associations independent of shared environmental and genetic factors. Understanding genetic underpinnings of risk score-cognition associations is important for early detection of dementia and designing intervention trials.Peer reviewe

Objectively measured physical activity profile and cognition in Finnish elderly twins

Introduction We studied whether objectively measured physical activity (PA) and sedentary behavior (SB) are associated with cognition in Finnish elderly twins. Methods This cross-sectional study comprised twins born in Finland from 1940 to 1944 in the Older Finnish Twin Cohort (mean age, 72.9 years; 726 persons). From 2014 to 2016, cognition was assessed with a validated telephonic interview, whereas PA was measured with a waist-worn accelerometer. Results In between-family models, SB and light physical activity had significant linear associations with cognition after adjusting for age, sex, wearing time, education level, body mass index, and living condition (SB: β-estimate, −0.21 [95% confidence intervals, −0.42 to −0.003]; light physical activity: β-estimate, 0.30 [95% confidence intervals, 0.02–0.58]). In within-family models, there were no significant linear associations between objectively measured PA and cognition. Discussion Objectively measured light physical activity and SB are associated with cognition in Finnish twins in their seventies, but the associations were attributable to genetic and environmental selection.Peer reviewe