7,781 research outputs found

    The Stratigraphic Record of Pre-breakup Geodynamics: Evidence from the Barrow Delta, offshore Northwest Australia

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    The structural and stratigraphic evolution of rift basins and passive margins has been widely studied, with many analyses demonstrating that delta systems can provide important records of post-rift geodynamic processes. However, the apparent lack of ancient syn-breakup delta systems and the paucity of seismic imaging across continent-ocean boundaries means the transition from continental rifting to oceanic spreading remains poorly understood. The Early Cretaceous Barrow Group of the North Carnarvon Basin, offshore NW Australia was a major deltaic system that formed during the latter stages of continental rifting, and represents a rich sedimentary archive, documenting uplift, subsidence and erosion of the margin. We use a regional database of 2D and 3D seismic and well data to constrain the internal architecture of the Barrow Group. Our results highlight three major depocentres: the Exmouth and Barrow sub-basins, and southern Exmouth Plateau. Over-compaction of pre-Cretaceous sedimentary rocks in the South Carnarvon Basin, and pervasive reworking of Permian and Triassic palynomorphs in the offshore Barrow Group, suggests that the onshore South Carnarvon Basin originally contained a thicker sedimentary succession, which was uplifted and eroded prior to breakup. Backstripping of sedimentary successions encountered in wells in the Exmouth Plateau depocentre indicate anomalously rapid tectonic subsidence (≤0.24 mm yr-1) accommodated Barrow Group deposition, despite evidence for minimal, contemporaneous upper crustal extension. Our results suggest that classic models of uniform extension cannot account for the observations of uplift and subsidence in the North Carnarvon Basin, and may indicate a period of depth-dependent extension or dynamic topography preceding breakup

    Z2SAL: a translation-based model checker for Z

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    Despite being widely known and accepted in industry, the Z formal specification language has not so far been well supported by automated verification tools, mostly because of the challenges in handling the abstraction of the language. In this paper we discuss a novel approach to building a model-checker for Z, which involves implementing a translation from Z into SAL, the input language for the Symbolic Analysis Laboratory, a toolset which includes a number of model-checkers and a simulator. The Z2SAL translation deals with a number of important issues, including: mapping unbounded, abstract specifications into bounded, finite models amenable to a BDD-based symbolic checker; converting a non-constructive and piecemeal style of functional specification into a deterministic, automaton-based style of specification; and supporting the rich set-based vocabulary of the Z mathematical toolkit. This paper discusses progress made towards implementing as complete and faithful a translation as possible, while highlighting certain assumptions, respecting certain limitations and making use of available optimisations. The translation is illustrated throughout with examples; and a complete working example is presented, together with performance data

    Glass production at an Early Islamic workshop in Tel Aviv

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    A refuse deposit at HaGolan Street, Khirbet al-Ḥadra, northeastern Tel Aviv, is rich in debris deriving from an Islamic period glass workshop, dating to the 7th–8th centuries. Twenty-four samples of glass vessels, chunks and moils were analysed by electron microprobe. Glass used in the workshop derives from three primary sources: Egypt II, somewhere in inland Egypt, Beth Eli'ezer, near Hadera, Israel and a third group which appears to represent a previously unknown Levantine primary production centre. Glass corresponding to at least twelve production events has been identified. While vessels made of Beth Eli'ezer and Egypt II glass have previously been reported from the same context, this is the first time that they have been related to the products of a single workshop. It appears that glass from both primary production centres was available in the later 8th century, and that the glass workers at HaGolan St were obliged to balance the high working and fuel costs of the stiff low-soda Levantine glass against the better working properties but higher raw material costs of the high-soda glass from Egypt

    Investigating white matter fibre density and morphology using fixel-based analysis

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    Voxel-based analysis of diffusion MRI data is increasingly popular. However, most white matter voxels contain contributions from multiple fibre populations (often referred to as crossing fibres), and therefore voxel-averaged quantitative measures (e.g. fractional anisotropy) are not fibre-specific and have poor interpretability. Using higher-order diffusion models, parameters related to fibre density can be extracted for individual fibre populations within each voxel (‘fixels’), and recent advances in statistics enable the multi-subject analysis of such data. However, investigating within-voxel microscopic fibre density alone does not account for macroscopic differences in the white matter morphology (e.g. the calibre of a fibre bundle). In this work, we introduce a novel method to investigate the latter, which we call fixel-based morphometry (FBM). To obtain a more complete measure related to the total number of white matter axons, information from both within-voxel microscopic fibre density and macroscopic morphology must be combined. We therefore present the FBM method as an integral piece within a comprehensive fixel-based analysis framework to investigate measures of fibre density, fibre-bundle morphology (cross-section), and a combined measure of fibre density and cross-section. We performed simulations to demonstrate the proposed measures using various transformations of a numerical fibre bundle phantom. Finally, we provide an example of such an analysis by comparing a clinical patient group to a healthy control group, which demonstrates that all three measures provide distinct and complementary information. By capturing information from both sources, the combined fibre density and cross-section measure is likely to be more sensitive to certain pathologies and more directly interpretable

    Rectal cancer management during the COVID-19 pandemic (ReCaP): multicentre prospective observational study.

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    Concerns over unacceptable high mortality in patients with rectal cancer undergoing surgery or systemic therapy who contract COVID-19 have led to widespread adoption of alternative treatment strategies.The ReCaP study aimed to study these variations and associated outcomes

    Evolution of normal fault displacement and length as continental lithosphere stretches

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    Continental rifting is accommodated by the development of normal fault networks. Fault growth patterns control their related seismic hazards, and the tectonostratigraphic evolution and resource and CO2 storage potential of rifts. Our understanding of fault evolution is largely derived by observing the final geometry and displacement (D)-length (L) characteristics of active and inactive fault arrays, and by subsequently inferring their kinematics. We can rarely determine how these geometric properties change through time, and how the growth of individual fault arrays relate to the temporal evolution of their host networks. Here we use 3D seismic reflection and borehole data from the Exmouth Plateau, NW Shelf, Australia to determine the growth of rift-related, crustal-scale fault arrays and networks over geological timescales (>106 Ma). The excellent-quality seismic data allows us to reconstruct the entire Jurassic-to-Early Cretaceous fault network over a relatively large area (ca. 1,200 km2). We find that fault trace lengths were established early, within the first ca. 7.2 Myr of rifting, and that along-strike migration of throw maxima towards the centre of individual fault arrays occurred after ca. 28.5 Myr of rifting. Faults located in stress shadows become inactive and appear under-displaced relative to adjacent larger faults, onto which strain localises as rifting proceeds. This implies that the scatter frequently observed in D-L plots can simply reflect fault growth and network maturity. We show that by studying complete rift-related normal networks, rather than just individual fault arrays, we can better understand how faults grow and more generally how continental lithosphere deforms as it stretches

    Single Gene Deletions of Orexin, Leptin, Neuropeptide Y, and Ghrelin Do Not Appreciably Alter Food Anticipatory Activity in Mice

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    Timing activity to match resource availability is a widely conserved ability in nature. Scheduled feeding of a limited amount of food induces increased activity prior to feeding time in animals as diverse as fish and rodents. Typically, food anticipatory activity (FAA) involves temporally restricting unlimited food access (RF) to several hours in the middle of the light cycle, which is a time of day when rodents are not normally active. We compared this model to calorie restriction (CR), giving the mice 60% of their normal daily calorie intake at the same time each day. Measurement of body temperature and home cage behaviors suggests that the RF and CR models are very similar but CR has the advantage of a clearly defined food intake and more stable mean body temperature. Using the CR model, we then attempted to verify the published result that orexin deletion diminishes food anticipatory activity (FAA) but observed little to no diminution in the response to CR and, surprisingly, that orexin KO mice are refractory to body weight loss on a CR diet. Next we tested the orexigenic neuropeptide Y (NPY) and ghrelin and the anorexigenic hormone, leptin, using mouse mutants. NPY deletion did not alter the behavior or physiological response to CR. Leptin deletion impaired FAA in terms of some activity measures, such as walking and rearing, but did not substantially diminish hanging behavior preceding feeding time, suggesting that leptin knockout mice do anticipate daily meal time but do not manifest the full spectrum of activities that typify FAA. Ghrelin knockout mice do not have impaired FAA on a CR diet. Collectively, these results suggest that the individual hormones and neuropepetides tested do not regulate FAA by acting individually but this does not rule out the possibility of their concerted action in mediating FAA

    The effects of childbirth on the pelvic-floor

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    Basically, vaginal delivery is associated with the risk of pelvic floor damage. The pelvic floor sequelae of childbirth includes anal incontinence, urinary incontinence and pelvic organ prolapse. Pathophysiology, incidence and risk factors for the development of the respective problems are reviewed. Where possible, recommendations for reducing the risk of pelvic floor damage are given
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