567 research outputs found

    Spatioselective surface chemistry for the production of functional and chemically anisotropic nanocellulose colloids

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    Maximizing the benefits of nanomaterials from biomass requires unique considerations associated with their native chemical and physical structure. Both cellulose nanofibrils and nanocrystals are extracted from cellulose fibers via a top-down approach and have significantly advanced materials chemistry and set new benchmarks in the last decade. One major challenge has been to prepare defined and selectively modified nanocelluloses, which would, e.g., allow optimal particle interactions and thereby further improve the properties of processed materials. At the molecular and crystallite level, the surface of nanocelluloses offers an alternating chemical structure and functional groups of different reactivity, enabling straightforward avenues towards chemically anisotropic and molecularly patterned nanoparticles via spatioselective chemical modification. In this review, we will explain the influence and role of the multiscale hierarchy of cellulose fibers in chemical modifications, and critically discuss recent advances in selective surface chemistry of nanocelluloses. Finally, we will demonstrate the potential of those chemically anisotropic nanocelluloses in materials science and discuss challenges and opportunities in this field.Peer reviewe

    Possible fabrication techniques and welding specifications for the external cylinder of the CMS coil

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    The Compact Muon Solenoid (CMS) is one of the experiments, which are being designed in the framework of the Large Hadron Collider (LHC) project at CERN. The design field of the CMS magnet is 4 T, the magnetic length is 12.5 m and the free aperture is 6 m in diameter. This is achieved with a 4 layer and 5 module superconducting Al- stabilized coil energized at a nominal current of 20 kA at 4.5 K. In the CMS coil the structural function is ensured, unlike in other existing Al-stabilized thin solenoids, both by the Al-alloy reinforced conductor and the external cylinder. The calculated stress level in the cylinder at operating conditions is particularly severe. In this paper the different possible fabrication techniques are assessed and compared and a possible welding specification for this component is given. (9 refs)

    The purpose of United Nations Security Council practice: Contesting competence claims in the normative context created by the Responsibility to Protect.

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    Practice theory provides important insight into the workings of the Security Council. The contribution is currently limited however by the conjecture that practice theory operates on ‘a different analytical plane’ to norm / normative theory (Adler-Nissen and Pouliot 2014). Building on existing critiques (Duval and Chowdhury 2011; Schindler and Wille 2015) we argue that analyzing practices separately from normative positions risks misappropriating competence and reifying practice that is not fit for purpose. This risk is realized in Adler-Nissen and Pouliot’s (2014) practice based account Libya crisis. By returning the normative context created by the Responsibility to Protect (R2P) to the analytical foreground, and by drawing on a pragmatic conception of 'ethical competence' (Frost 2009), we find that pre-reflexive practices uncritically accepted as markers of competence – e.g. ‘penholding’ – can contribute to the Council’s failure to act collectively in the face of mass atrocity. Drawing on extensive interview material we offer an alternative account of the Libya intervention, finding that the practices of the permanent three (France, UK and US) did not cultivate the kind of collective consciousness that is required to implement R2P. This is further illustrated by an account of the Security Council’s failure in Syria, where the P3’s insistence on regime change instrumentalized the Council at the expense of R2P-appropriate practice. This changed when elected members became ‘penholders’. Practice theory can facilitate learning processes that help the Council meet its responsibilities, but only through an approach that combines its insights with those of norm / normative theory

    Intervention and revision: Expertise and interaction in text mediation

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    Many EAL (English as an Additional Language) scholars enlist text mediators’ support when faced with the challenges of writing for international publication. However, the contributions these individuals are able to make in improving scientific manuscripts remains unclear, especially when language professionals such as English teachers do this work. In this article, we explore this topic by examining how three mediators employed their very different expertise and brought different processes to bear on the same discussion section of a medical manuscript written by a novice scholar in China. We find that successfully mediated texts are often the result of an interplay between the mediator’s expertise and the relationship between the participants. Our findings contradict those of previous studies that question the role of English teachers in this process and have the potential to inform both text mediation practices and revision studies

    The CMS conductor

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    The Compact Muon Solenoid (CMS) is one of the experiments, which are being designed in the framework of the Large Hadron Collider (LHC) project at CERN, the design field of the CMS magnet is 4 T, the magnetic length is 13 m and the aperture is 6 m. This high magnetic field is achieved by means of a 4 layer, 5 modules superconducting coil. The coil is wound from an Al-stabilized Rutherford type conductor. The nominal current of the magnet is 20 kA at 4.5 K. In the CMS coil the structural function is ensured, unlike in other existing Al-stabilized thin solenoids, both by the Al-alloy reinforced conductor and the external former. In this paper the retained manufacturing process of the 50-km long reinforced conductor is described. In general the Rutherford type cable is surrounded by high purity aluminium in a continuous co-extrusion process to produce the Insert. Thereafter the reinforcement is joined by Electron Beam Welding to the pure Al of the insert, before being machined to the final dimensions. During the manufacture the bond quality between the Rutherford cable and the high purity aluminium as well as the quality of the EB welding are continuously controlled by a novel ultrasonic phased array system. The dimensions of the insert and the final conductor are measured by laser micrometer. (8 refs)

    Hidden expectations: Scaffolding subject specialists' genre knowledge of the assignments they set

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    Subject specialists’ knowledge of academic and disciplinary literacy is often tacit. We tackle the issue of how to elicit subject specialists’ tacit knowledge in order to develop their pedagogical practices and enable them to communicate this knowledge to students. Drawing on theories of genre and metacognition, a professional development activity was designed and delivered. Our aims were to (1) build participants’ genre knowledge and (2) scaffold metacognitive awareness of how genre knowledge can enhance their pedagogical practices. The findings reveal that participants built a genre-based understanding of academic literacy and that the tasks provided them with an accessible framework to articulate and reflect upon their knowledge of disciplinary literacy. Participants gained metacognitive awareness of misalignments between what they teach and what they expect from students, their assumptions about students’ prior learning and genre-based strategies to adapt their practice to students’ needs. Our approach provides a theoretically grounded professional development tool for the HE sector
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