24,327 research outputs found

    Structure, bonding and morphology of hydrothermally synthesised xonotlite

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    The authors have systematically investigated the role of synthesis conditions upon the structure and morphology of xonotlite. Starting with a mechanochemically prepared, semicrystalline phase with Ca/Si=1, the authors have prepared a series of xonotlite samples hydrothermally, at temperatures between 200 and 250 degrees C. Analysis in each case was by X-ray photoelectron spectroscopy, environmental scanning electron microscopy and X-ray diffraction. The authors’ use of a much lower water/solid ratio has indirectly confirmed the ‘through solution’ mechanism of xonotlite formation, where silicate dissolution is a key precursor of xonotlite formation. Concerning the role of temperature, too low a temperature (~200 degrees C) fails to yield xonotlite or leads to increased number of structural defects in the silicate chains of xonotlite and too high a temperature (>250 degrees C) leads to degradation of the xonotlite structure, through leaching of interchain calcium. Synthesis duration meanwhile leads to increased silicate polymerisation due to diminishing of the defects in the silicate chains and more perfect crystal morphologies

    Chromatin proteins and RNA are associated with DNA during all phases of mitosis.

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    Mitosis brings about major changes to chromosome and nuclear structure. We used recently developed proximity ligation assay-based techniques to investigate the association with DNA of chromatin-associated proteins and RNAs in Drosophila embryos during mitosis. All groups of tested proteins, histone-modifying and chromatin-remodeling proteins and methylated histones remained in close proximity to DNA during all phases of mitosis. We also found that RNA transcripts are associated with DNA during all stages of mitosis. Reduction of H3K27me3 levels or elimination of RNAs had no effect on the association of the components of PcG and TrxG complexes to DNA. Using a combination of proximity ligation assay-based techniques and super-resolution microscopy, we found that the number of protein-DNA and RNA-DNA foci undergoes significant reduction during mitosis, suggesting that mitosis may be accompanied by structural re-arrangement or compaction of specific chromatin domains

    Reducing the drag: creating v formations through slow scholarship and story

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    Every seed destroys its container, or else there would be no fruition (Scott-Maxwell, 1979). We are three women working across two Australian universities. Frustrated at the deadening, withering nature and containment of the neoliberal university, and inspired by the wisdom of slow scholarship and the cooperative reciprocity inherent in the V formations adopted by groups of flying birds to boost vital energy, our chapter encapsulates our efforts to ‘care for self and others’ and ‘count what others don’t’. It follows our attempts to resist the insidious, diminishing drag of metric-based audits and managerialism. Having joyfully discovered we have ‘outgrown’ narrow academic containers of measurement, comparison, and productivity, we are responding to our longing to connect and to ‘be’ differently in academia. Our resistance is characterised by efforts to listen and converse in meaningful ways, ways that speak our lives into the academy. For over a year we have been initiating conversations with a trusted group of colleagues and acquiring responsive, personal and aesthetic ways to address and reconcile our personal/professional lives. Inviting the reader into our deliberate storying and de-storying of our lived experience whilst practicing a politics of care, collaboration and authenticity, we are subverting what it means to be productive and accountable and what it means to be an academic. And in so doing we are seeding new and fruitful ways of working. We are unearthing our individual and collective voice, and creating and expanding safe spaces for scholarly, professional and personal disclosure and meaning-making

    Wind tunnel investigation of an oblique wing transport model at mach numbers between 0.6 and 1.4

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    Models of three practical oblique-wing transport configurations were tested in the NASA Ames 11 foot wind tunnel. The three configurations used a common forward fuselage, wing, and support system but employed different aft fuselage sections simulating alternate propulsion system installations. These included an integrated propulsion system, pylon-mounted nacelles, and clean (no propulsion system) configuration. The tests were conducted over a Mach number range from 0.6 to 1.4 and at sweep angles from 0 to 60 degrees. The nominal unit Reynolds number was 1.83 million per meter and the angle of attack range was -3 to +6 degrees. The models were mounted in the tunnel by means of a lower blade support system. The interference effects of this lower blade and the flow inclination were determined by using an image blade system and testing the configuration in both the upright and inverted positions

    Mechanisms for Non-Trivial Magnetization Plateaux of an S=1 Frustrated Spin Ladder

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    We investigate the non-trivial magnetization plateau at 1/4 of the saturation magnetization of S=1 spin ladder, especially with reference to recent experimental results on a new organic tetraradical 3,3',5,5'-tetrakis(N-tert-butylaminoxyl)biphenyl, abbreviated as BIP-TENO. We propose three mechanisms for the formation of the plateau; the Neel mechanism, the dimer mechanism and the spin-Peierls mechanism. We also discuss the effect of four-spin exchange interactions.Comment: 3 pages, 5 figures, Orbital2001 (International Conference on Strongly Correlated Electrons with Orbital Degrees of Freedom) (September 11-14, 2001. Sendai

    Brain structure in pediatric Tourette syndrome

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    Previous studies of brain structure in Tourette syndrome (TS) have produced mixed results, and most had modest sample sizes. In the present multicenter study, we used structural magnetic resonance imaging (MRI) to compare 103 children and adolescents with TS to a well-matched group of 103 children without tics. We applied voxel-based morphometry methods to test gray matter (GM) and white matter (WM) volume differences between diagnostic groups, accounting for MRI scanner and sequence, age, sex and total GM+WM volume. The TS group demonstrated lower WM volume bilaterally in orbital and medial prefrontal cortex, and greater GM volume in posterior thalamus, hypothalamus and midbrain. These results demonstrate evidence for abnormal brain structure in children and youth with TS, consistent with and extending previous findings, and they point to new target regions and avenues of study in TS. For example, as orbital cortex is reciprocally connected with hypothalamus, structural abnormalities in these regions may relate to abnormal decision making, reinforcement learning or somatic processing in TS

    Detection of 6 K gas in Ophiuchus D

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    Cold cores in interstellar molecular clouds represent the very first phase in star formation. The physical conditions of these objects are studied in order to understand how molecular clouds evolve and how stellar masses are determined. The purpose of this study is to probe conditions in the dense, starless clump Ophichus D (Oph D). The ground-state (1(10)-1(11)) rotational transition of ortho-H2D+ was observed with APEX towards the density peak of Oph D. The width of the H2D+ line indicates that the kinetic temperature in the core is about 6 K. So far, this is the most direct evidence of such cold gas in molecular clouds. The observed H2D+ spectrum can be reproduced with a hydrostatic model with the temperature increasing from about 6 K in the centre to almost 10 K at the surface. The model is unstable against any increase in the external pressure, and the core is likely to form a low-mass star. The results suggest that an equilibrium configuration is a feasible intermediate stage of star formation even if the larger scale structure of the cloud is thought to be determined by turbulent fragmentation. In comparison with the isothermal case, the inward decrease in the temperature makes smaller, i.e. less massive, cores susceptible to externally triggered collapse.Comment: 7 pages, 5 figures, accepted for Astronomy and Astrophysic

    Engineering advice in policy-making: a new domain of inquiry in evidence and policy

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    Background. Academic research on technical advice to policy commonly focuses on social and related policy areas such as health, education and crime (Oliver et al. 2014) and disciplinary advice from science disciplines (Jasanoff 1994; Millstone and van Zwanenberg 2001). Little or no prior research in the social sciences have explored engineering expertise in policy domains where such advice is critical (e.g. energy policy). Aims and objectives. We aim to establish ‘engineering advice’ as a new domain of inquiry by showing how civil servants view it as distinctive (from ‘science advice’), important and similar to policy making – implying it can clash or complement it. Methods. 18 qualitative interviews with a purposive sample of officials across a UK ministry were conducted by the authors (all but one of whom were civil servants) in 2012. The qualitative data were thematically coded to address the study aims. Findings. A majority of officials spontaneously identified engineering expertise as both distinctive and important for their work. There was clear evidence that it both complemented and clashed with policymaking. Discussion. We identified a range of interactions that imply a need to consider styles of management internal deployment of experts within policy organisations as well as the implications for policy making and engineering expertise given the way practices overlap. Conclusions. Further research on the ontological, epistemological nature of engineering as it relates to policy making is needed if governments and therefore society are to fully benefit from engineering advice
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