Dynamic intermediate ocean circulation in the North Atlantic during Heinrich Stadial 1: a radiocarbon and neodymium isotope perspective

The last deglaciation was characterised by a series of millennial scale climate events that have been linked to deep ocean variability. While often implied in interpretations, few direct constraints exist on circulation changes at mid-depths. Here we provide new constraints on the variability of deglacial mid-depth circulation using combined radiocarbon and neodymium isotopes in 24 North Atlantic deep-sea corals. Their aragonite skeletons have been dated by uranium-series, providing absolute ages and the resolution to record centennial scale changes, while transects spanning the lifetime of a single coral allow sub-centennial tracer reconstruction. Our results reveal that rapid fluctuations of water mass sourcing and radiocarbon affected the mid-depth water column (1.7-2.5 km) on timescales of less than 100 years during the latter half of Heinrich Stadial 1. The neodymium isotopic variability (−14.5 to −11.0) ranges from the composition of the modern northern-sourced waters towards more radiogenic compositions that suggest the presence of a greater southern-sourced component at some times. However, in detail, simple two-component mixing between well-ventilated northern-sourced and radiocarbon-depleted southern-sourced water masses cannot explain all our data. Instead, corals from ~15.0 ka and ~15.8 ka may record variability between southern-sourced intermediate waters and radiocarbon-depleted northern-sourced waters, unless there was a major shift in the neodymium isotopic composition of the northern endmember. In order to explain the rapid shift towards the most depleted radiocarbon values at ~15.4 ka, we suggest a different mixing scenario involving either radiocarbon-depleted deep water from the Greenland-Iceland-Norwegian Seas or a southern-sourced deep water mass. Since these mid-depth changes preceded the Bolling-Allerod warming, and were apparently unaccompanied by changes in the deep Atlantic, they may indicate an important role for the intermediate ocean in the early deglacial climate evolution

Neodymium isotopes and concentrations in aragonitic scleractinian cold-water coral skeletons - Modern calibration and evaluation of palaeo-applications

TvdF and TS acknowledge financial support for a bursary by the Grantham Institute of Climate Change and the Environment and a Marie Curie Reintegration grant (IRG 230828), as well as funding from the Leverhulme Trust (RPG-398) and the NERC (NE/N001141/1). Additional financial support was provided to LFR by the USGS-WHOI Co-operative agreement, NSF-ANT grants 0636787 and 80295700, The European Research Council, the Leverhulme Trust and a Marie Curie Reintegration grant. LB was supported by a NOAA/UCAR Climate and Global Change Postdoctoral Fellowship and KJM acknowledges funding from a Marie Curie International Outgoing fellowship (IOF 236962).Cold-water corals (CWCs) are unique archives of mid-depth ocean chemistry and have been used successfully to reconstruct the neodymium (Nd) isotopic composition of seawater from a number of species. High and variable Nd concentrations in fossil corals however pose the question as to how Nd is incorporated into their skeletons. We here present new results on modern specimens of Desmophyllum dianthus, Balanophyllia malouinensis, and Flabellum curvatum, collected from the Drake Passage, and Madrepora oculata, collected from the North Atlantic. All modern individuals were either collected alive or uranium-series dated to be < 500 years old for comparison with local surface sediments and seawater profiles. Modern coral Nd isotopic compositions generally agree with ambient seawater values, which in turn are consistent with previously published seawater analyses, supporting small vertical and lateral Nd isotope gradients in modern Drake Passage waters. Two Balanophyllia malouinensis specimens collected live however deviate by up to 0.6 epsilon units from ambient seawater. We therefore recommend that this species should be treated with caution for the reconstruction of past seawater Nd isotopic compositions. Seventy fossil Drake Passage CWCs were furthermore analysed for their Nd concentrations, revealing a large range from 7.3 to 964.5 ng/g. Samples of the species D. dianthus and Caryophyllia spp. show minor covariation of Nd with 232Th content, utilised to monitor contaminant phases in cleaned coral aragonite. Strong covariations between Nd and Th concentrations are however observed in the species B. malouinensis and G. antarctica. In order to better constrain the source and nature of Nd in the cleaned aragonitic skeletons, a subset of sixteen corals was investigated for its rare earth element (REE) content, as well as major and trace element geochemistry. Our new data provide supporting evidence that the applied cleaning protocol efficiently removes contaminant lithogenic and ferromanganese oxyhydroxide phases. Mass balance calculations and seawater-like REE patterns rule out lithogenic and ferromanganese oxyhydroxide phases as a major contributor to elevated Nd concentrations in coral aragonite. Based on mass balance considerations, geochemical evidence, and previously published independent work by solid-state nuclear magnetic resonance (NMR) spectroscopy, we suggest authigenic phosphate phases as a significant carrier of skeletal Nd. Such a carrier phase could explain sporadic appearance of high Nd concentrations in corals and would be coupled with seawater-derived Nd isotopic compositions, lending further confidence to the application of Nd isotopes as a water mass proxy in CWCs.Publisher PDFPeer reviewe

Automated Deception Detection of Males and Females From Non-Verbal Facial Micro-Gestures

Gender bias within Artificial intelligence driven systems is currently a hot topic and is one of a number of areas where the data used to train, validate and test machine learning algorithms is under more scrutiny than ever before. In this paper we investigate if there is a difference between the nonverbal cues to deception generated by males and females through the use of an automated deception detection system. The system uses hierarchical neural networks to extract 36 channels of non-verbal head and facial behaviors whilst male and female participants are engaged in either a deceptive or truthful roleplaying task. An Image Vector dataset, comprising of 86584 vectors, is collated which uses a fixed sliding window slot of 1 second to record deceptive or truthful slots. Experiments were conducted on three variants of the dataset, all males, all females and mixed in order to examine if the differences in cues generated by males and females lead to differences in the accuracies of machine learning algorithms which classify their behavior. Results showed differences in nonverbal cues between males and females, with both genders at a disadvantage when treated by classifiers trained on both genders rather than classifiers specifically trained for each gender. However, there was no striking disadvantageous effect beyond the influence of their relative frequency of occurrence in the dataset

Formation of Spaced Cleavage and Concurrent Mass Removal of Si02, Meguma Goup Metagreywackes, Goldenville, Nova Scotia

Increasing inequancy and decreasing fluctuation of long axes of quartz grains from lithons to cleavage zones in Heguna Group metagreywackes indicate an increase in strain. This strain increase is best ascribed to pervasive pressure solution in which quartz grains are trimmed to yield nearly rectangular sections in cleavage zones, as compared to their irregular outlines in lithons. Shortening calculated from a one-dimensional strain model reaches 60-7OZ in cleavage zones. Comparable values of shortening are calculated from modal analyses, and from chemical analyses of cleavages and lithons. The Implication of such shortening is that about ten percent of all the quartz in the original rock has been removed from the immediate system. This demands volumes of water about one order of magnitude greater than any likely content of connate water. The transport system was a dynamic one, involving most of the rock volume. R&#xC9;SUM&#xC9; L'accroieseaent de l'in&#xE9;galit&#xE9; et la baisse des fluctuations des longs axes des grains de quartz, des lithons jusqu'aux zones de clivage, dans les m&#xE9;tagrauwackes du groupe M&#xE9;guma, indique une haueae de tension. Cette hausse de tension est attribute &#xE0; la solution de pression p&#xE9;n&#xE9;trante dans laquelle les grains de quartz sont tall&#xE9;s et donnent des sections presque rectangulaires dans les zones de clivage, compar&#xE9; &#xE0; leur profile irr&#xE9;gulier dans les lithons. Le raccourcissement, calculi &#xE0; partlr d'un mod&#xE8;le de pression unidimensionnel, atteint des valeurs entre 60 et 702 dans les zones de clivage. Des valeurs comparables du raccourcissement sont calcul&#xE9;es &#xE0; partlr d'analyses modales, et d'analyses chimiques des clivages et des lithons. L'implicatlon de ce raccourclssement est qu'environ dix pourcent de tout le quartz de la roche originaire, a &#xE9;t&#xE9; sup&#xE9;rime du syst&#xE8;me imm&#xE9;diate Cela exige des volumes d'eau d'un ordre de grandeur plus important que n'importe quel syst&#xE8;me inn&#xE9; d'eau vraissembable. Ce syst&#xE8;me de transport &#xE9;tait un syst&#xE8;me dynamique qui comprenait la majorit&#xE9; du volume des roches. [Traduit par le journal

Platinum-group elements, S, Se and Cu in highly depleted abyssal peridotites from the Mid-Atlantic Ocean Ridge (ODP Hole 1274A): Influence of hydrothermal and magmatic processes

Highly depleted harzburgites and dunites were recovered from ODP Hole 1274A, near the intersection between the Mid-Atlantic Ocean Ridge and the 15°20′N Fracture Zone. In addition to high degrees of partial melting, these peridotites underwent multiple episodes of melt-rock reaction and intense serpentinization and seawater alteration close to the seafloor. Low concentrations of Se, Cu and platinum-group elements (PGE) in harzburgites drilled at around 35-85 m below seafloor are consistent with the consumption of mantle sulfides after high degrees (>15-20 %) of partial melting and redistribution of chalcophile and siderophile elements into PGE-rich residual microphases. Higher concentrations of Cu, Se, Ru, Rh and Pd in harzburgites from the uppermost and lowest cores testify to late reaction with a sulfide melt. Dunites were formed by percolation of silica- and sulfur-undersaturated melts into low-Se harzburgites. Platinum-group and chalcophile elements were not mobilized during dunite formation and mostly preserve the signature of precursor harzburgites, except for higher Ru and lower Pt contents caused by precipitation and removal of platinum-group minerals. During serpentinization at low temperature (<250 °C) and reducing conditions, mantle sulfides experienced desulfurization to S-poor sulfides (mainly heazlewoodite) and awaruite. Contrary to Se and Cu, sulfur does not record the magmatic evolution of peridotites but was mostly added in hydrothermal sulfides and sulfate from seawater. Platinum-group elements were unaffected by post-magmatic low-temperature processes, except Pt and Pd that may have been slightly remobilized during oxidative seawater alteration

Do‐it‐yourself continuous glucose monitoring in people aged 16 to 69 years with type 1 diabetes: A qualitative study

Aims: In many countries, real-time continuous glucose monitoring (rt- CGM) is not funded, and cost presents a barrier to access. A do-it-yourself conversion of intermittently scanned CGM (DIY- CGM) is a cheaper alternative. This qualitative study aimed to explore user experiences with DIY- CGM in people aged 16 to 69 years with type 1 diabetes (T1D). Methods: Convenience sampling was used to recruit participants for semi-structured virtual interviews exploring experiences of DIY- CGM use. Participants were recruited after completing the intervention arm of a crossover randomised controlled trial that evaluated DIY- CGM versus intermittently scanned CGM (isCGM). Participants were previously naive to DIY- CGM and rt- CGM but not isCGM. The DIY- CGM intervention consisted of a Bluetooth bridge connected to isCGM, adding rt- CGM functionality over 8 weeks. Interviews were transcribed, then thematic analysis was performed. Results: Interviews were with 12 people aged 16 to 65 years, with T1D: mean age ± SD 43 ±14 years; baseline mean HbA1c ± SD 60 mmol/mol ± 9.9 (7.6 ± 0.9%) and time in range 59.8% ± 14.8%. Participants perceived that using DIY- CGM improved both glycaemic control and aspects of quality of life. Alarm and trend functionality allowed participants to perceive reduced glycaemic variability overnight and following meals. The addition of a smartwatch increased discrete access to glucose information. There was a high degree of trust in DIY- CGM. Challenges while using DIY- CGM included signal loss during vigorous exercise, alarm fatigue and short battery life. Conclusions: This study suggests that for users, DIY- CGM appears to be an acceptable alternative method of rt- CGM

A qualitative study of professional and client perspectives on information flows and decision aid use

<p>Abstract</p> <p>Background</p> <p>This paper explores the meanings given by a diverse range of stakeholders to a decision aid aimed at helping carers of people in early to moderate stages of dementia (PWD) to select community based respite services. Decision aids aim to empower clients to share decision making with health professionals. However, the match between health professionals' perspectives on decision support needs and their clients' perspective is an important and often unstudied aspect of decision aid use.</p> <p>Methods</p> <p>A secondary analysis was undertaken of qualitative data collected as part of a larger study. The data included twelve interviews with carers of people with dementia, three interviews with expert advisors, and three focus groups with health professionals. A theoretical analysis was conducted, drawing on theories of 'positioning' and professional identity.</p> <p>Results</p> <p>Health professionals are seen to hold varying attitudes and beliefs about carers' decision support needs, and these appeared to be grounded in the professional identity of each group. These attitudes and beliefs shaped their attitudes towards decision aids, the information they believed should be offered to dementia carers, and the timing of its offering. Some groups understood carers as needing to be protected from realistic information and consequently saw a need to filter information to carer clients.</p> <p>Conclusion</p> <p>Health professionals' beliefs may cause them to restrict information flows, which can limit carers' ability to make decisions, and limit health services' ability to improve partnering and shared decision making. In an era where information is freely available to those with the resources to access it, we question whether health professionals should filter information.</p