2,239 research outputs found
Differences between European birthweight standards: impact on classification of âsmall for gestational ageâ
We describe a quantitative and comparative review of a selection of European birthweight standards for gestational age for singletons, to enable appropriate choices to be made for clinical and research use. Differences between median values at term across standards in 10 regions and misclassification of âsmall for gestational ageâ (SGA), were studied. Sex and parity differences, exclusion criteria, and methods of construction were considered. There was wide variation between countries in exclusion criteria, methods of calculating standards, and median birthweight at term. The lightest standards (e.g. France's medians are 255g lower than Norway's medians) were associated with fewer exclusion criteria. Up to 20% of the population used in the construction of the Scottish standard would be classified as SGA using the Norwegian standard. Substantial misclassification of SGA is possible. Assumptions about variation used in the construction of some standards were not justified. It is not possible to conclude that there are real differences in birthweight standards between European countries. Country-based standards control for some population features but add misclassification due to the differing ways in which standards are derived. Standards should be chosen to reflect clinical or research need. If standards stratified by sex or parity are not available, adjustments should be made. In multinational studies, comparisons should be made between results using both a common standard and country-based standards
Holographic Screening Length in a Hot Plasma of Two Sphere
We study the screening length of a quark-antiquark pair moving in a hot
plasma living in two sphere manifold using AdS/CFT correspondence where
the background metric is four dimensional Schwarzschild-AdS black hole. The
geodesic solution of the string ends at the boundary is given by a stationary
motion in the equatorial plane as such the separation length of
quark-antiquark pair is parallel to the angular velocity . The
screening length and the bound energy are computed numerically using
Mathematica. We find that the plots are bounded from below by some functions
related to the momentum transfer of the drag force configuration. We
compare the result by computing the screening length in the quark-antiquark
reference frame where the gravity dual are "Boost-AdS" and Kerr-AdS black
holes. Finding relations of the parameters of both black holes, we argue that
the relation between mass parameters of the Schwarzschild-AdS black
hole and of the Kerr-AdS black hole in high temperature is given by
, where is the angular momentum
parameter.Comment: Major revision: title changed, adding authors, 13 pages, 8 figures,
etc. Accepted for publication in European Physical Journal
Extremely low longâterm erosion rates around the Gamburtsev Mountains in interior East Antarctica
The high elevation and rugged relief (>3 km) of the Gamburtsev Subglacial Mountains (GSM) have long been considered enigmatic. Orogenesis normally occurs near plate boundaries, not cratonic interiors, and largeâscale tectonic activity last occurred in East Antarctica during the PanâAfrican (480â600 Ma). We sampled detrital apatite from Eocene sands in Prydz Bay at the terminus of the Lambert Graben, which drained a large preâglacial basin including the northern Gamburtsev Mountains. Apatite fissionâtrack and (UâTh)/He cooling ages constrain bedrock erosion rates throughout the catchment. We doubleâdated apatites to resolve individual cooling histories. Erosion was very slow, averaging 0.01â0.02 km/Myr for >250 Myr, supporting the preservation of high elevation in interior East Antarctica since at least the cessation of Permian rifting. Longâterm topographic preservation lends credence to postulated highâelevation mountain ice caps in East Antarctica since at least the Cretaceous and to the idea that coldâbased glaciation can preserve tectonically inactive topography
Improving expert forecasts in reliability. Application and evidence for structured elicitation protocols
Quantitative expert judgementsare used in reliability assessmentsto informcritically important decisions. Structured elicitation protocols have been advocated to improveexpert judgements, yet their application in reliability ischallenged by a lack of examples or evidence that they improve judgements. This paper aims to overcome these barriers. We present a case study where two world-leading protocols, the IDEA protocol and the Classical Model were combined and applied by the Australian Department of Defence for a reliability assessment. We assess the practicality of the methods, and the extent to which they improve judgements. The average expert was extremely overconfident, with 90% credible intervals containing the true realisation 36% of the time. However,steps contained inthe protocols substantially improvedjudgements. In particular, an equal weighted aggregation of individual judgements, and the inclusion ofa discussion phase and revised estimate helped to improve calibration, statistical accuracy and the Classical Model score. Further improvements in precision and information were made via performance weighted aggregation. This paper provides useful insights into the application of structured elicitation protocols for reliability andthe extent to which judgements are improved. The findings raise concerns about existing practices for utilising experts in reliability assessments and suggest greater adoption of structured protocols is warranted. We encourage the reliability community to further develop examples and insights
Novel technique for the CO<sub>2</sub> laser fabrication of optical devices with sub-micrometer ablation depth precision
We present novel techniques for the processing of fibre end face and cladding surfaces using a 9.6 Âľm CO2 laser. We investigate the effects of pulse duration on process parameters
Floating s- and p-type Gaussian Orbitals
The advantages of including a small number of p-type gaussian functions in a floating spherical gaussian orbital calculation are pointed out and illustrated by calculations on molecules which previously have proved to be troublesome. These include molecules such as F2 with multiple lone pairs and C2H2 with multiple bonds. A feature of the results is the excellent correlation between the orbital energies and those of a double zeta calculation reported by Snyder and Basch
Geographers out of place: institutions, (inter)disciplinarity and identity
Ten years ago, the decision was taken to close Brunel Universityâs Department of Geography and Earth Sciences and its undergraduate programmes. Since this time, most of the human geographers have remained at Brunel, but now work from beyond the boundaries of conventional academic Geography. In this paper we argue that this situation, which is not uncommon for geographers in the UK and elsewhere, has significant implications for both individuals and the discipline more broadly. Through our everyday experiences of interdisciplinary working, this paper reflects on what it means to be a geographer working outside of âGeographyâ. The paper examines the implications of this at three different yet related scales: the immediately personal scale in terms of identity and individual academic performance, the institutional scale and its organisation that can lead to the presence/ absence of academic subject areas, and then finally the disciplinary scale with its attendant spaces of knowledge generation, dissemination and protectionism. Our arguments are framed by neoliberal-led higher education changes and conceptualisations of institutions, (inter)disciplinarity and identity, and point to broader significances for the shape of the discipline
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Boron, carbon, and oxygen isotopic composition of brachiopod shells: Intra-shell variability, controls, and potential as a paleo-pH recorder
The boron isotopic composition of biogenic carbonates has been used to reconstruct seawater pH and atmospheric pCO2 on Pleistocene and Cenozoic timescales. Because of their excellent preservation and extensive fossil record throughout the Phanerozoic, brachiopods are a promising candidate for extending the boron isotope record as far back as the Cambrian. Here we present stable carbon, oxygen, and boron isotopic measurements of modern Terebratulid brachiopod calcite in comparison with environmental pH estimates calculated from oceanographic data. Geochemical transects along the length and depth of single shells confirm previously published trends in carbon and oxygen isotopic composition. In the outer surface (primary and outermost secondary layers), δ11B covaries with δ13C and δ18O, with more negative values in the outer and more positive values in the middle of the shell. However, δ11B deviates from δ13C and δ18O in the inner part of the secondary layer, where the δ13C and δ18O values are more positive and near equilibrium, whereas δ11B returns to more negative values. A comparison of different specimens of the species Terebratalia transversa (Sowerby, 1846) and Laqueus californianus (Kßster, 1844) microsampled from the middle part of the fibrous secondary layer demonstrates a clear correlation to ambient pH with a sensitivity similar to other empirical calibration curves for cultured planktic foraminifers, corals, and inorganic calcite. The relationship in other species is less clear and significantly offset, necessitating the use of a single species or a cross-calibration method with other species in paleo-pH reconstructions
ODDSOC2 Is a MADS Box Floral Repressor That Is Down-Regulated by Vernalization in Temperate Cereals
In temperate cereals, such as wheat (Triticum aestivum) and barley (Hordeum vulgare), the transition to reproductive development can be accelerated by prolonged exposure to cold (vernalization). We examined the role of the grass-specific MADS box gene ODDSOC2 (OS2) in the vernalization response in cereals. The barley OS2 gene (HvOS2) is expressed in leaves and shoot apices but is repressed by vernalization. Vernalization represses OS2 independently of VERNALIZATION1 (VRN1) in a VRN1 deletion mutant of einkorn wheat (Triticum monococcum), but VRN1 is required to maintain down-regulation of OS2 in vernalized plants. Furthermore, barleys that carry active alleles of the VRN1 gene (HvVRN1) have reduced expression of HvOS2, suggesting that HvVRN1 down-regulates HvOS2 during development. Overexpression of HvOS2 delayed flowering and reduced spike, stem, and leaf length in transgenic barley plants. Plants overexpressing HvOS2 showed reduced expression of barley homologs of the Arabidopsis (Arabidopsis thaliana) gene FLOWERING PROMOTING FACTOR1 (FPF1) and increased expression of RNase-S-like genes. FPF1 promotes floral development and enhances cell elongation, so down-regulation of FPF1-like genes might explain the phenotypes of HvOS2 overexpression lines. We present an extended model of the genetic pathways controlling vernalization-induced flowering in cereals, which describes the regulatory relationships between VRN1, OS2, and FPF1-like genes. Overall, these findings highlight differences and similarities between the vernalization responses of temperate cereals and the model plant Arabidopsis
Enhanced pump absorption in double-clad fibres using localised laser-machined mode scramblers
A novel method for improving pump absorption efficiency in circular double-clad fibres by laser machining localised pump scramblers at strategic positions along the fibre is reported. Preliminary results for a thulium-doped double-clad fibre indicate that the pump absorption coefficient attainable via this approach is comparable to an equivalent octagonal fibre
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