402 research outputs found

    Epitaxial growth and thermodynamic stability of SrIrO3/SrTiO3 heterostructures

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    Obtaining high-quality thin films of 5d transition metal oxides is essential to explore the exotic semimetallic and topological phases predicted to arise from the combination of strong electron correlations and spin-orbit coupling. Here, we show that the transport properties of SrIrO3 thin films, grown by pulsed laser deposition, can be optimized by considering the effect of laser-induced modification of the SrIrO3 target surface. We further demonstrate that bare SrIrO3 thin films are subject to degradation in air and are highly sensitive to lithographic processing. A crystalline SrTiO3 cap layer deposited in-situ is effective in preserving the film quality, allowing us to measure metallic transport behavior in films with thicknesses down to 4 unit cells. In addition, the SrTiO3 encapsulation enables the fabrication of devices such as Hall bars without altering the film properties, allowing precise (magneto)transport measurements on micro- and nanoscale devices.Comment: 5 pages, 3 figure

    The role of positron-emission tomography in the diagnosis of giant cell arteritis

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    Abstract Background: Giant cell arteritis (GCA) is an inflammatory disease of the larger vessels, typically affecting the temporal arteries, but involvement of the carotid and thoracic arteries is not uncommon. Serious complications such as blindness can occur if the disease is left untreated. Currently, the gold standard test for GCA is a temporal biopsy, but this invasive technique is not without risks and frequently inaccurate. We investigate the use of 18-fluoro-desoxyglucose (18F-FDG) positron emission tomography (PET) as a new diagnostic means in GCA. Methods: We performed a literature search in the MEDLINE database for original research articles written in the English language that discussed the use of PET in diagnosing GCA. After applying selection criteria, 9 articles were included for literature review and 4 of these were incorporated in a meta-analysis. Results: 18-FDG uptake in the extracranial arteries is correlated to the presence GCA within patients suspected for vasculitis. In our meta-analysis we found the following results: sensitivity 85% (95% CI; 74-92%, I2=0.0%), specificity 91% (95% CI; 82-96%, I2=31.2%), positive likelihood ratio 7.18 (95% CI; 3.43-15.06, I2 =10.1%) and negative likelihood ratio 0.19 (95% CI; 0.11-0.33, I2= 0.0%). Discussion: 18F-FDG-PET cannot replace temporal artery biopsy at the present time, because of its limited ability to visualise the cranial arteries. However, PET may be provide valuable information when extracranial involvement is suspected, specifically in biopsy-negative patients who are strongly suspected of having GCA

    Upgrade of the HadGEM3-A based attribution system to high resolution and a new validation framework for probabilistic event attribution

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    We present a substantial upgrade of the Met Office system for the probabilistic attribution of extreme weather and climate events with higher horizontal and vertical resolution (60 km mid-latitudes and 85 vertical levels), the latest Hadley Centre atmospheric and land model (ENDGame dynamics with GA6.0 science and JULES at GL6.0) as well as an updated forcings set. A new set of experiments designed for the evaluation and implementation of an operational attribution service are described which consist of pairs of multi-decadal stochastic physics ensembles continued on a season by season basis by large ensembles that are able to sample extreme at- mospheric states possible in the recent past. Diagnostics from these experiments form the HadGEM3-A contribution to the international Climate of the 20th Century Plus (C20Cþ) project and were analysed under the European Climate and Weather Events: Interpretation and Attribution (EUCLEIA) event attribution project as well as contributing to the Climate Science for Service Partnership (CSSP)-China programme. After discussing the framing issues surrounding questions that can be asked with our system we construct a novel approach to the evaluation of atmosphere-only ensembles intended for event attribution, in the process highlighting and clarifying the distinction between hindcast skill and model performance. A framework based around assessing model representation of predictable components and ensuring exchangeability of model and real world statistics leads to a form of detection and attribution to boundary condition forcing as a means of quantifying one degree of freedom of potential model error and allowing for the bias correction of event probabilities and resulting probability ratios. This method is then applied systematically across the globe to assess contributions from anthropogenic influence and specific boundary conditions to the changing probability of observed and record seasonal mean temperatures of four recent 3-month seasons from March 2016–February 2017

    Reversing Blood Flows Act through klf2a to Ensure Normal Valvulogenesis in the Developing Heart

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    Heart valve anomalies are some of the most common congenital heart defects, yet neither the genetic nor the epigenetic forces guiding heart valve development are well understood. When functioning normally, mature heart valves prevent intracardiac retrograde blood flow; before valves develop, there is considerable regurgitation, resulting in reversing (or oscillatory) flows between the atrium and ventricle. As reversing flows are particularly strong stimuli to endothelial cells in culture, an attractive hypothesis is that heart valves form as a developmental response to retrograde blood flows through the maturing heart. Here, we exploit the relationship between oscillatory flow and heart rate to manipulate the amount of retrograde flow in the atrioventricular (AV) canal before and during valvulogenesis, and find that this leads to arrested valve growth. Using this manipulation, we determined that klf2a is normally expressed in the valve precursors in response to reversing flows, and is dramatically reduced by treatments that decrease such flows. Experimentally knocking down the expression of this shear-responsive gene with morpholine antisense oligonucleotides (MOs) results in dysfunctional valves. Thus, klf2a expression appears to be necessary for normal valve formation. This, together with its dependence on intracardiac hemodynamic forces, makes klf2a expression an early and reliable indicator of proper valve development. Together, these results demonstrate a critical role for reversing flows during valvulogenesis and show how relatively subtle perturbations of normal hemodynamic patterns can lead to both major alterations in gene expression and severe valve dysgenesis

    Coupling charge and topological reconstructions at polar oxide interfaces

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    In oxide heterostructures, different materials are integrated into a single artificial crystal, resulting in a breaking of inversion-symmetry across the heterointerfaces. A notable example is the interface between polar and non-polar materials, where valence discontinuities lead to otherwise inaccessible charge and spin states. This approach paved the way to the discovery of numerous unconventional properties absent in the bulk constituents. However, control of the geometric structure of the electronic wavefunctions in correlated oxides remains an open challenge. Here, we create heterostructures consisting of ultrathin SrRuO3_3, an itinerant ferromagnet hosting momentum-space sources of Berry curvature, and LaAlO3_3, a polar wide-bandgap insulator. Transmission electron microscopy reveals an atomically sharp LaO/RuO2_2/SrO interface configuration, leading to excess charge being pinned near the LaAlO3_3/SrRuO3_3 interface. We demonstrate through magneto-optical characterization, theoretical calculations and transport measurements that the real-space charge reconstruction modifies the momentum-space Berry curvature in SrRuO3_3, driving a reorganization of the topological charges in the band structure. Our results illustrate how the topological and magnetic features of oxides can be manipulated by engineering charge discontinuities at oxide interfaces.Comment: 5 pages main text (4 figures), 29 pages of supplementary informatio

    Rich Situated Attitudes

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    We outline a novel theory of natural language meaning, Rich Situated Semantics [RSS], on which the content of sentential utterances is semantically rich and informationally situated. In virtue of its situatedness, an utterance’s rich situated content varies with the informational situation of the cognitive agent interpreting the utterance. In virtue of its richness, this content contains information beyond the utterance’s lexically encoded information. The agent-dependence of rich situated content solves a number of problems in semantics and the philosophy of language (cf. [14, 20, 25]). In particular, since RSS varies the granularity of utterance contents with the interpreting agent’s informational situation, it solves the problem of finding suitably fine- or coarse-grained objects for the content of propositional attitudes. In virtue of this variation, a layman will reason with more propositions than an expert

    Protein intake and bone mineral density: Cross-sectional relationship and longitudinal effects in older adults

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    Background: There are several mechanisms via which increased protein intake might maintain or improve bone mineral density (BMD), but current evidence for an association or effect is inconclusive. The objectives of this study were to investigate the association between dietary protein intake (total, plant and animal) with BMD (spine and total body) and the effects of protein supplementation on BMD. Methods: Individual data from four trials that included either (pre-)frail, undernourished or healthy older adults (aged ≥65 years) were combined. Dietary intake was assessed with food records (2, 3 or 7 days) and BMD with dual-energy X-ray absorptiometry (DXA). Associations and effects were assessed by adjusted linear mixed models. Results: A total of 1570 participants [57% women, median (inter-quartile range): age 71 (68–75) years] for which at least total protein intake and total body BMD were known were included in cross-sectional analyses. In fully adjusted models, total protein intake was associated with higher total body and spine BMD [beta (95% confidence interval): 0.0011 (0.0006–0.0015) and 0.0015 (0.0007–0.0023) g/cm2, respectively]. Animal protein intake was associated with higher total body and spine BMD as well [0.0011 (0.0007–0.0016) and 0.0017 (0.0010–0.0024) g/cm2, respectively]. Plant protein intake was associated with a lower total body and spine BMD [−0.0010 (−0.0020 to −0.0001) and −0.0019 (−0.0034 to −0.0004) g/cm2, respectively]. Associations were similar between sexes. Participants with a high ratio of animal to plant protein intake had higher BMD. In participants with an adequate calcium intake and sufficient serum 25(OH)D concentrations, the association between total protein intake with total body and spine BMD became stronger. Likewise, the association between animal protein intake with total body BMD was stronger. In the longitudinal analyses, 340 participants [58% women, median (inter-quartile range): age 75 (70–81) years] were included. Interventions of 12 or 24 weeks with protein supplementation or protein supplementation combined with resistance exercise did not lead to significant improvements in BMD. Conclusions: An association between total and animal protein intake with higher BMD was found. In contrast, plant protein intake was associated with lower BMD. Research is warranted to further investigate the added value of dietary protein alongside calcium and vitamin D for BMD improvement, especially in osteopenic or osteoporotic individuals. Moreover, more research on the impact of a plant-based diet on bone health is needed
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