Late Precambrian U-Pb titanite age for peak regional metamorphism and deformation (Knoydartian orogeny) in the western Moine, Scotland

There has been controversy over the number and timing of orogenies in the Precambrian Moine block in the Scottish Caledonides since the earliest radiometric dating in the 1960s. This work challenges a recent hypothesis, that this sector of the Laurentian margin was subjected to continuous crustal extension between greater than 900 and 470 Ma. U-Pb dating (thermal ionization mass spectrometry) of titanite from a calcsilicate pod in the Moine (Morar Group) of the western Highlands gives an age of 737 ñ 5 Ma. The titanite grew from Fe-Ti-bearing detrital minerals during the main progressive, syn-D2, amphibolite-facies (sillimanite zone) regional metamorphism, thus demonstrating that a Neoproterozoic contractional tectonothermal event (Knoydartian orogeny) affected the Moine block following the rift-related emplacement of the West Highland granite gneiss at 873 Ma. We conclude that the Sgurr Beag Thrust, a major tectonic break separating the Morar and Glenfinnan groups of the Moine, is mainly of Neoproterozoic, not Caledonian, age. The early tectonothermal event was succeeded by the Grampian Phase (Caledonian orogeny) at 460-470 Ma

Equivalence of two approaches for the inhomogeneous density in the canonical ensemble

In this article we show that the inhomogeneous density obtained from a density-functional theory of classical fluids in the canonical ensemble (CE), recently presented by White et al [Phys. Rev. Lett. 84 (2000) 1220], is equivalent to first order to the result of the series expansion of the CE inhomogeneous density introduced by Gonzalez et al [Phys. Rev. Lett. 79 (1997) 2466].Comment: 6 pages, RevTe

Occurrence of the alien nudibranch Melibe viridis (Kelaart, 1858) (Opisthobranchia, Tethydidae), in the Maltese Islands

The alien dendronotacean nudibranch Melibe viridis (Kelaart, 1858), a tropical Indo-Pacific species that seems to have been introduced by shipping into the Mediterranean via the Suez Canal, and which has established populations in Greece, Turkey, Cyprus, Montenegro, Croatia, NW Sicily, southern peninsular Italy and Djerba Island in the Gulf of Gabes, is recorded for the first time from Malta. A thriving population was observed on a soft sediment bottom at a depth of 18-20 m off the western coast of the island of Comino (Maltese Islands). It is suggested that this species was introduced into Malta due to a natural range expansion of surrounding populations

Relationship continuity and emotional well-being in spouses of people with dementia

YesObjectives: Qualitative research has suggested that spousal experiences of discontinuity in their relationship with a person who has dementia (i.e. the relationship is experienced as radically changed) may contribute to heightened feelings of burden, entrapment, isolation, guilt and intolerance of behaviours that challenge. By contrast, continuity in the relationship may contribute to a greater sense of achievement and gratification from providing care. The present study served as a quantitative test of these suggestions. Method: A convenience sample of 71 spouses of people with dementia completed three questionnaires - the Zarit Burden Interview (ZBI), the Positive Aspects of Caregiving measure (PAC) and the Birmingham Relationship Continuity Measure (BRCM). Results: In accordance with the hypotheses, the experience of greater relationship continuity (higher BRCM scores) was correlated with fewer negative emotional reactions to caregiving (lower ZBI scores; rho = −.795) and more positive emotional reactions (higher PAC scores; rho = .764). Conclusions: The study provided some quantitative support for suggestions arising from qualitative research about how perceptions of continuity/discontinuity in the relationship may impact on the caregiving spouse's emotional well-being. Helping couples to maintain a sense of continuity and couplehood may assist their emotional adjustment to dementia

Glacial geomorphology of the Neutral Hills Uplands, southeast Alberta, Canada: The process-form imprints of dynamic ice streams and surging ice lobes

The Neutral Hills Uplands of southern Alberta, Canada is an area of complex and varied glacial landforms dominated by glacitectonic compressional structures but also containing expansive areas of hummocky terrain and kame and kettle topography. It lies between the strongly streamlined trunks of the former Central Alberta (CAIS) and Maskwa palaeo-ice streams of the SW Laurentide Ice Sheet (LIS) and hence comprises an inter-ice stream regional moraine zone, constructed at around 15.5 cal ka BP. This study aimed to compile a regional map of the glacial geomorphology of central southeast Alberta in order to decipher the landform-sediment signatures of overprinted ice stream margins in terrestrial continental environments, and to refine the palaeoglaciological reconstructions for the southwest LIS. Detailed mapping from LiDAR and aerial imagery identifies distinctive glacial landsystems diagnostic of the partial overprinting of cross-cutting ice stream trunks and fast flow lobes. Widespread evidence of surge-diagnostic features indicates that the ice streams experienced repeated flow instabilities, consistent with the broader scenario of a highly dynamic and unstable SW LIS, characterised by markedly transitory and cross-cutting palaeo-ice streams. The inter-ice stream moraine zone is characterised by spectacular glacitectonic compression of bedrock, cupola hill construction and mega raft displacement but also displays evidence of multi-phase stagnant ice melt-out, where partially overprinted surge lobes advanced into large areas of buried glacier ice. Contemporaneous ice melting led to the widespread development of glacier karst and the production of eskers at a range of scales, the largest of which record deranged drainage patterns indicative of ice-walled channel sedimentation controlled by the regional bedrock slope towards the northeast. These process-form regimes have created a significant local relief that is a product of not only glacitectonic compression of bedrock but also the creation and melting of a melange of ice and bedrock/sediment blocks of variable ice volume, which are representative of former buried snout ice with a glacier karst system that was repeatedly proglacially thrust due to surging. Widespread evidence for subglacial channel cutting is likely strongly linked to the transitory, surging and cross-cutting nature of the palaeo-ice streams in the region, whereby ice streams switched on and surged in response to the build-up, migration and marginal outbursts of subglacial water reservoirs. In addition to the reduced basal friction caused by the low permeability of the Cretaceous bedrock, pressurized groundwater and potentially also shallow biogenic gas deposits were likely important to the process-form regimes of surging lobes of soft-bedded ice streams in a region where ice flow was against an adverse bed slope; a scenario that gave rise to a variety of enigmatic landforms such as doughnuts, doughnut chains, apparent blow-out features and possible till eskers, as well as glacitectonic mega-rafts

Determination of step--edge barriers to interlayer transport from surface morphology during the initial stages of homoepitaxial growth

We use analytic formulae obtained from a simple model of crystal growth by molecular--beam epitaxy to determine step--edge barriers to interlayer transport. The method is based on information about the surface morphology at the onset of nucleation on top of first--layer islands in the submonolayer coverage regime of homoepitaxial growth. The formulae are tested using kinetic Monte Carlo simulations of a solid--on--solid model and applied to estimate step--edge barriers from scanning--tunneling microscopy data on initial stages of Fe(001), Pt(111), and Ag(111) homoepitaxy.Comment: 4 pages, a Postscript file, uuencoded and compressed. Physical Review B, Rapid Communications, in press

A multi-isotope investigation of diet and subsistence amongst island and mainland populations from early medieval western Britain

Objectives: This is the first investigation of dietary practices amongst multiple early medieval populations (AD 500–1000) from Wales and the Isle of Man using carbon, nitrogen, and sulphur isotope analysis. The analysis will illuminate similarities or differences between the diets and subsistence strategies of populations occupying different geographical regions, specifically those living in marginal coastal regions in comparison to inland populations well-connected to ecclesiastical centres and high-status settlements. Materials and Methods: One hundred and two human skeletons were sampled for carbon and nitrogen isotope analysis, and 69 human skeletons were sampled for sulphur isotope analysis from nine cemetery sites from western Britain (Isle of Man = 3, southwest Wales = 4, southeast Wales = 2). Thirteen faunal skeletons from St Patrick's Chapel (southwest Wales) were sampled for carbon, nitrogen, and sulphur isotope analysis. Results: Human δ13C values range from −19.4‰ to −21.2‰ (δ13C mean=−20.4 ±0.4‰, 1σ, n = 86), and δ15N values range from 9.1‰ to 13.8‰ (δ15N mean = 10.8 ± 0.9‰, 1σ, n = 86). δ34S values range from 1.2‰ to 18.4‰ (δ34S mean = 11.6 ± 4.5‰, 1σ, n = 66). Significant differences were noted between the mean δ13C, δ15N and δ34S values according to geographic region: Isle of Man (δ13C = −20.7 ± 0.4‰, δ15N = 11.4 ±0.6‰, n = 13/86; δ34S mean = 17.1 ±0.6, n = 4/66), southwest Wales (δ13C = −20.5 ± 0.4‰, δ15N = 11.0 ±1‰, n = 32/86; δ34S = 16.1 ± 2.1, n = 21/66), and southeast Wales (δ13C =−20.3 ±0.4‰, δ15N = 10.4 ±0.7‰, n = 41/86; δ34S= 8.8 ±3‰, n = 41/66). Faunal δ13C values range from −23.1‰ to −21.2‰ (δ13C mean= −22.1 ±0.5‰, 1σ, n = 13), and δ15N values range from 6.3‰ to 9.8‰ (δ15N mean = 7.3 ± 1.1‰, 1σ, n = 13). δ34S values range from 4.7‰ to 18.4‰ (δ34S mean= 16.3 ± 3.6‰, 1σ, n = 13). Conclusions: The data reveal a reliance on terrestrial protein, however differences are observed between the resource consumption of populations from southwest Wales and the Isle of Man in comparison to the populations from southeast Wales. Populations from the west coast have a marine sulphur signature that reflects their coastal proximity and may also include a reliance on seaweed as a fertiliser/food source. Populations in the southeast were connected to ecclesiastical centres and high-status settlements and had access to inland-grown produce. The data add support to the suggestion that δ34S can be used as a mobility indicator

Finite-Element Discretization of Static Hamilton-Jacobi Equations Based on a Local Variational Principle

We propose a linear finite-element discretization of Dirichlet problems for static Hamilton-Jacobi equations on unstructured triangulations. The discretization is based on simplified localized Dirichlet problems that are solved by a local variational principle. It generalizes several approaches known in the literature and allows for a simple and transparent convergence theory. In this paper the resulting system of nonlinear equations is solved by an adaptive Gauss-Seidel iteration that is easily implemented and quite effective as a couple of numerical experiments show.Comment: 19 page

Remote sensing of glacier change (1965 - 2021) and identification of surge-type glaciers on Severnaya Zemlya, Russian High Arctic

Glaciers in the Russian High Arctic have undergone accelerated mass loss due to atmospheric and oceanic warming in the Barents-Kara Seas region. Most studies have concentrated on the western Barents-Kara sector, despite evidence of accelerating mass loss as far east as Severnaya Zemlya. However, long-term trends in glacier change on Severnaya Zemlya are largely unknown and this record may be complicated by surge-type glaciers. Here, we present a long-term assessment of glacier change (1965-2021) on Severnaya Zemlya and a new inventory of surge-type glaciers using declassified spy-satellite photography (KH-7/9 Hexagon) and optical satellite imagery (ASTER, Sentinel-2A, Landsat 4/5 TM & 8 OLI). Glacier area reduced from 17,053 km2 in 1965 to 16,275 in 2021 (-5%; mean: -18%, max: -100%), with areal shrinkage most pronounced at land-terminating glaciers on southern Severnaya Zemlya, where there is a recent (post-2010s) increase in summer atmospheric temperatures. We find that surging may be more widespread than previously thought, with three glaciers classified confirmed as surge-type, eight as likely to have surged and nine as possible, comprising 11% of Severnaya Zemlya’s 190 glaciers (37% by area). Under continued warming, we anticipate accelerated retreat and increased likelihood of surging as basal thermal regimes shift