1,001 research outputs found

    Local density approximations from finite systems

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    The local density approximation (LDA) constructed through quantum Monte Carlo calculations of the homogeneous electron gas (HEG) is the most common approximation to the exchange-correlation functional in density functional theory. We introduce an alternative set of LDAs constructed from slablike systems of one, two, and three electrons that resemble the HEG within a finite region, and illustrate the concept in one dimension. Comparing with the exact densities and Kohn-Sham potentials for various test systems, we find that the LDAs give a good account of the self-interaction correction, but are less reliable when correlation is stronger or currents flow

    Status and outlook for lithium-ion battery cathode material synthesis and the application of mechanistic modeling

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    This work reviews different techniques available for the synthesis and modification of cathode active material (CAM) particles used in Li-ion batteries. The synthesis techniques are analyzed in terms of processes involved and product particle structure. The knowledge gap in the process-particle structure relationship is identified. Many of these processes are employed in other similar industries; hence, parallel insights and knowledge transfer can be applied to battery materials. Here, we discuss examples of applications of different mechanistic models outside the battery literature and identify similar potential applications for the synthesis of CAMs. We propose that the widespread implementation of such mechanistic models will increase the understanding of the process-particle structure relationship. Such understanding will provide better control over the CAM synthesis technique and open doors to the precise tailoring of product particle morphologies favorable for enhanced electrochemical performance

    Accurate total energies from the adiabatic-connection fluctuation-dissipation theorem

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    In the context of inhomogeneous one-dimensional finite systems, recent numerical advances [Phys. Rev. B 103, 125155 (2021)2469-995010.1103/PhysRevB.103.125155] allow us to compute the exact coupling-constant dependent exchange-correlation kernel fxcλ(x,x′,ω) within linear response time-dependent density-functional theory. This permits an improved understanding of ground-state total energies derived from the adiabatic-connection fluctuation-dissipation theorem (ACFDT). We consider both one-shot and self-consistent ACFDT calculations, and demonstrate that chemical accuracy is reliably preserved when the frequency dependence in the exact functional fxc[n](ω=0) is neglected. This performance is understood on the grounds that the exact fxc[n] varies slowly over the most relevant ω range (but not in general), and hence the spatial structure in fxc[n](ω=0) is able to largely remedy the principal issue in the present context: self-interaction (examined from the perspective of the exchange-correlation hole). Moreover, we find that the implicit orbitals contained within a self-consistent ACFDT calculation utilizing the adiabatic exact kernel fxc[n](ω=0) are remarkably similar to the exact Kohn-Sham orbitals, thus further establishing that the majority of the physics required to capture the ground-state total energy resides in the spatial dependence of fxc[n] at ω=0

    Recruitment to randomised trials : Strategies for Trial Enrolment and Participation Study. The STEPS study

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    Objectives: To identify factors associated with good and poor recruitment to multicentre trials. Data sources: Part A: database of trials started in or after 1994 and were due to end before 2003 held by the Medical Research Council and Health Technology Assessment Programmes. Part B: interviews with people playing a wide range of roles within four trials that their funders identified as ‘exemplars’. Part C: a large multicentre trial (the CRASH trial) of treatment for head injury. Review methods: The study used a number of different perspectives (‘multiple lenses’), and three components. Part A: an epidemiological review of a cohort of trials. Part B: case studies of trials that appeared to have particularly interesting lessons for recruitment. Part C: a single, in-depth case study to examine the feasibility of applying a businessorientated analytical framework as a reference model in future trials. Results: In the 114 trials found in Part A, less than one-third recruited their original target within the time originally specified, and around one-third had extensions. Factors observed more often in trials that recruited successfully were: having a dedicated trial manager, being a cancer or drug trial, and having interventions only available inside the trial. The most commonly reported strategies to improve recruitment were newsletters and mailshots, but it was not possible to assess whether they were causally linked to changes in recruitment. The analyses in Part B suggested that successful trials were those addressing clinically important questions at a timely point. The investigators were held in high esteem by the interviewees, and the trials were firmly grounded in existing clinical practices, so that the trial processes were not alien to clinical collaborators, and the results could be easily applicable to future practice. The interviewees considered that the needs of patients were well served by participation in the trials. Clinical collaborators particularly appreciated clear delineation of roles, which released them from much of the workload associated with trial participation. There was a strong feeling from interviewees that they were proud to be part of a successful team. This pride fed into further success. Good groundwork and excellent communications across many levels of complex trial structures were considered to be extremely important, including training components for learning about trial interventions and processes, and team building. All four trials had faced recruitment problems, and extra insights into the working of trials were afforded by strategies invoked to address them. The process of the case study in Part C was able to draw attention to a body of research and practice in a different discipline (academic business studies). It generated a reference model derived from a combination of business theory and work within CRASH. This enabled identification of weaker managerial components within CRASH, and initiatives to strengthen them. Although it is not clear, even within CRASH, whether the initiatives that follow from developing and applying the model will be effective in increasing recruitment or other aspects of the success of the trial, the reference model could provide a template, with potential for those managing other trials to use or adapt it, especially at foundation stages. The model derived from this project could also be used as a diagnostic tool if trials have difficulties and hence as a basis for deciding what type of remedial action to take. It may also be useful for auditing the progress of trials, such as during external review. Conclusions: While not producing sufficiently definitive results to make strong recommendations, the work here suggests that future trials should consider the different needs at different phases in the life of trials, and place greater emphasis on ‘conduct’ (the process of actually doing trials). This implies learning lessons from successful trialists and trial managers, with better training for issues relating to trial conduct. The complexity of large trials means that unanticipated difficulties are highly likely at some time in every trial. Part B suggested that successful trials were those flexible and robust enough to adapt to unexpected issues. Arguably, the trialists should also expect agility from funders within a proactive approach to monitoring ongoing trials. Further research into different recruitment patterns (including ‘failures’) may help to clarify whether the patterns seen in the ‘exemplar’ trials differ or are similar. The reference model from Part C needs to be further considered in other similar and different trials to assess its robustness. These and other strategies aimed at increasing recruitment and making trials more successful need to be formally evaluated for their effectiveness in a range of trials.Not peer reviewedPublisher PD

    Reaching consensus on reporting patient and public involvement (PPI) in research: methods and lessons learned from the development of reporting guidelines

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    INTRODUCTION: Patient and public involvement (PPI) is inconsistently reported in health and social care research. Improving the quality of how PPI is reported is critical in developing a higher quality evidence base to gain a better insight into the methods and impact of PPI. This paper describes the methods used to develop and gain consensus on guidelines for reporting PPI in research studies (updated version of the Guidance for Reporting Patient and Public Involvement (GRIPP2)). METHODS: There were three key stages in the development of GRIPP2: identification of key items for the guideline from systematic review evidence of the impact of PPI on health research and health services, a three-phase online Delphi survey with a diverse sample of experts in PPI to gain consensus on included items and a face-to-face consensus meeting to finalise and reach definitive agreement on GRIPP2. Challenges and lessons learnt during the development of the reporting guidelines are reported. DISCUSSION: The process of reaching consensus is vital within the development of guidelines and policy directions, although debate around how best to reach consensus is still needed. This paper discusses the critical stages of consensus development as applied to the development of consensus for GRIPP2 and discusses the benefits and challenges of consensus development

    Broadening public participation in systematic reviews : a case example involving young people in two configurative reviews

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    Background: Arguments supporting the involvement of users in research have even more weight when involving the public in systematic reviews of research. We aimed to explore the potential for public involvement in systematic reviews of observational and qualitative studies. Methods: Two consultative workshops were carried out with a group of young people (YP) aged 12–17 years to examine two ongoing reviews about obesity: one about children's views and one on the link between obesity and educational attainment. YP were invited to comment on the credibility of themes, to propose elements of interventions, to suggest links between educational attainment and obesity and to comment on their plausibility. Results: Researchers had more confidence in review findings, after checking that themes identified as important by YP were emphasised appropriately. Researchers were able to use factors linking obesity and attainment identified as important by YP to identify limitations in the scope of extant research. Conclusion: Consultative workshops helped researchers draw on the perspectives of YP when interpreting and reflecting upon two systematic reviews. Involving users in judging synthesis credibility and identifying concepts was easier than involving them in interpreting findings. Involvement activities for reviews should be designed with review stage, purpose and group in mind

    Conceptual learning : the priority for higher education

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    The common sense notion of learning as the all-pervasive acquisition of new behaviour and knowledge, made vivid by experience, is an incomplete characterisation, because it assumes that the learning of behaviour and the learning of knowledge are indistinguishable, and that acquisition constitutes learning without reference to transfer. A psychological level of analysis is used to argue that conceptual learning should have priority in higher education

    Suited for Success? : Suits, Status, and Hybrid Masculinity

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    This document is the Accepted Manuscript version. The final, definitive version of this paper has been published in Men and Masculinities, March 2017, doi: https://doi.org/10.1177/1097184X17696193, published by SAGE Publishing, All rights reserved.This article analyzes the sartorial biographies of four Canadian men to explore how the suit is understood and embodied in everyday life. Each of these men varied in their subject positions—body shape, ethnicity, age, and gender identity—which allowed us to look at the influence of men’s intersectional identities on their relationship with their suits. The men in our research all understood the suit according to its most common representation in popular culture: a symbol of hegemonic masculinity. While they wore the suit to embody hegemonic masculine configurations of practice—power, status, and rationality—most of these men were simultaneously marginalized by the gender hierarchy. We explain this disjuncture by using the concept of hybrid masculinity and illustrate that changes in the style of hegemonic masculinity leave its substance intact. Our findings expand thinking about hybrid masculinity by revealing the ways subordinated masculinities appropriate and reinforce hegemonic masculinity.Peer reviewe

    Protected proteins as supplements for bulls fed tropical forage diets

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    Under the extensive conditions encountered in the dry tropics of Australia mating in the beef herd ususally commences immediately after the onset of the wet season. Bulls are often mated only four to six weeks after suffering a period of liveweight loss. This experiment looked at the liveweight change and reproductive responses when bulls were subject to two different planes of nutrition
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