280 research outputs found

    Discussions and Reviews : Waging experimental war: a review

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66539/2/10.1177_002200276200600108.pd

    High-definition velocity-space tomography of fast-ion dynamics

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    Velocity-space tomography of the fast-ion distribution function in a fusion plasma is usually a photon-starved tomography method due to limited optical access and signal-to-noise ratio of fast-ion Dα (FIDA) spectroscopy as well as the strive for high-resolution images. In high-definition tomography, prior information makes up for this lack of data. We restrict the target velocity space through the measured absence of FIDA light, impose phase-space densities to be non-negative, and encode the known geometry of neutral beam injection (NBI) sources. We further use a numerical simulation as prior information to reconstruct where in velocity space the measurements and the simulation disagree. This alternative approach is demonstrated for four-view as well as for two-view FIDA measurements. The high-definition tomography tools allow us to study fast ions in sawtoothing plasmas and the formation of NBI peaks at full, half and one-third energy by time-resolved tomographic movies

    4D and 5D phase-space tomography using slowing-down physics regularization

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    We compute reconstructions of 4D and 5D fast-ion phase-space distribution functions in fusion plasmas from synthetic projections of these functions. The fast-ion phase-space distribution functions originating from neutral beam injection (NBI) at TCV and Wendelstein 7-X (W7-X) at full, half, and one-third injection energies can be istinguished and particle densities of each component inferred based on 20 synthetic spectra of projected velocities at TCV and 680 at W7-X. Further, we demonstrate that an expansion into a basis of slowing-down distribution functions is equivalent to regularization using slowing-down physics as prior information. Using this technique in a Tikhonov formulation, we infer the particle density fractions for each NBI energy for each NBI beam from synthetic measurements, resulting in six unknowns at TCV and 24 unknowns at W7-X. Additionally, we show that installing 40 LOS in each of 17 ports at W7-X, providing full beam coverage and almost full angle coverage, produces the highest quality reconstructions

    特別賦金論

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    Velocity-space tomography has been used to infer 2D fast-ion velocity distribution functions. Here we compare the performance of five different tomographic inversion methods: truncated singular value decomposition, maximum entropy, minimum Fisher information and zerothand first-order Tikhonov regularization. The inversion methods are applied to fast-ion Dα measurements taken just before and just after a sawtooth crash in the ASDEX Upgrade tokamak as well as to synthetic measurements from different test distributions. We find that the methods regularizing by penalizing steep gradients or maximizing entropy perform best. We assess the uncertainty of the calculated inversions taking into account photon noise, uncertainties in the forward model as well as uncertainties introduced by the regularization which allows us to distinguish regions of high and low confidence in the tomographies. In high confidence regions, all methods agree that ions with pitch values close to zero, as well as ions with large pitch values, are ejected from the plasma center by the sawtooth crash, and that this ejection depletes the ion population with large pitch values more strongly

    Influence of microenvironment on engraftment of transplanted β-cells

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    Pancreatic islet transplantation into the liver provides a possibility to treat selected patients with brittle type 1 diabetes mellitus. However, massive early β-cell death increases the number of islets needed to restore glucose homeostasis. Moreover, late dysfunction and death contribute to the poor long-term results of islet transplantation on insulin independence. Studies in recent years have identified early and late challenges for transplanted pancreatic islets, including an instant blood-mediated inflammatory reaction when exposing human islets to the blood microenvironment in the portal vein and the low oxygenated milieu of islets transplanted into the liver. Poor revascularization of remaining intact islets combined with severe changes in the gene expression of islets transplanted into the liver contributes to late dysfunction. Strategies to overcome these hurdles have been developed, and some of these interventions are now even tested in clinical trials providing a hope to improve results in clinical islet transplantation. In parallel, experimental and clinical studies have, based on the identified problems with the liver site, evaluated the possibility of change of implantation organ in order to improve the results. Site-specific differences clearly exist in the engraftment of transplanted islets, and a more thorough characterization of alternative locations is needed. New strategies with modifications of islet microenvironment with cells and growth factors adhered to the islet surface or in a surrounding matrix could be designed to intervene with site-specific hurdles and provide possibilities to improve future results of islet transplantation

    Towards a contemporary social care ‘prevention narrative’ of principled complexity: An integrative literature review

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    Prevention has become increasingly central in social care policy and commissioning strategies within the United Kingdom (UK). Commonly there is reliance on understandings borrowed from the sphere of public health, leaning on a prevention discourse characterised by the 'upstream and downstream' metaphor. Whilst framing both structural factors and responses to individual circumstances, the public health approach nonetheless suggests linearity in a cause and effect relationship. Social care and illness follow many trajectories and this conceptualisation of prevention may limit its effectiveness and scope in social care. Undertaken as part of a commissioned evaluation of the Social Services and Wellbeing Act (2014) Wales, a systematic integrative review was conducted to establish the key current debates within prevention work, and how prevention is conceptually framed, implemented and evaluated within the social care context. The databases Scopus, ASSIA, CINAHL and Social Care Online were initially searched in September 2019 resulting in 52 documents being incorporated for analysis. A further re-run of searches was run in March 2021, identifying a further 14 documents, thereby creating a total of 66. Predominantly, these were journal articles or research reports (n = 53), with the remainder guidance or strategy documents, briefings or process evaluations (n = 13). These were categorised by their primary theme and focus, as well as document format and research method before undergoing thematic analysis. This highlighted the continued prominence of three-tiered, linear public health narratives in the framing of prevention for social care, with prevention work often categorised and enacted with inconsistency. Common drivers for prevention activity continue to be cost reduction and reduced dependence on the care system in the future. Through exploring prevention for older people and caregivers, we argue for an approach to prevention aligning with the complexities of the social world surrounding it. Building on developments in complexity theory in social science and healthcare, we offer an alternative view of social care prevention guided by principles rooted in the everyday realities of communities, service users and caregivers

    Mate-selection and the Dark Triad: Facilitating a Short-term Mating Strategy and Creating a Volatile Environment

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    The current study (N = 242) seeks to establish the relationship between traits known collectively as the Dark Triad - narcissism, psychopathy, Machiavellianism - and mating standards and preferences. Using a budget-allocation task, we correlated scores on the Dark Triad traits with mate preferences for a long-term and short-term mate. Men scoring high on the Dark Triad may be more indiscriminate than most when selecting for short-term mates in order to widen their prospects. Furthermore, those high on the Dark Triad - psychopathy in particular - tend to select for mates based on self-interest, assortative mating, or a predilection for volatile environments. We assessed these correlations when controlling for the Big Five and the sex of the participant. We also tested for moderation by the sex of the participant and mating context. Ramifications and future directions are considered

    Fine-Scale Mapping of the 4q24 Locus Identifies Two Independent Loci Associated with Breast Cancer Risk

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    Background: A recent association study identified a common variant (rs9790517) at 4q24 to be associated with breast cancer risk. Independent association signals and potential functional variants in this locus have not been explored. Methods: We conducted a fine-mapping analysis in 55,540 breast cancer cases and 51,168 controls from the Breast Cancer Association Consortium. Results: Conditional analyses identified two independent association signals among women of European ancestry, represented by rs9790517 [conditional P = 2.51 × 10−4; OR, 1.04; 95% confidence interval (CI), 1.02–1.07] and rs77928427 (P = 1.86 × 10−4; OR, 1.04; 95% CI, 1.02–1.07). Functional annotation using data from the Encyclopedia of DNA Elements (ENCODE) project revealed two putative functional variants, rs62331150 and rs73838678 in linkage disequilibrium (LD) with rs9790517 (r2 ≥ 0.90) residing in the active promoter or enhancer, respectively, of the nearest gene, TET2. Both variants are located in DNase I hypersensitivity and transcription factor–binding sites. Using data from both The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC), we showed that rs62331150 was associated with level of expression of TET2 in breast normal and tumor tissue. Conclusion: Our study identified two independent association signals at 4q24 in relation to breast cancer risk and suggested that observed association in this locus may be mediated through the regulation of TET2. Impact: Fine-mapping study with large sample size warranted for identification of independent loci for breast cancer risk
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