155 research outputs found
Analysis of Alfven eigenmodes destabilization by energetic particles in TJ-II using a Landau-closure model
Alfven Eigenmodes (AE) can be destabilized by energetic particles in neutral beam injection (NBI) heated plasmas through inverse Landau damping and couplings with gap modes in the shear Alfven continua. We describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system using the reduced MHD equations, density and parallel velocity moments for the energetic particles as well as the geodesic acoustic wave dynamics. A closure relation adds the Landau damping and resonant destabilization effects in the model. We apply the model to study the Alfven modes stability in TJ-II, performing a parametric analysis in a range of realistic values of energetic particle beta (beta(f)), ratios of thermal/Alfven velocities (V-th/V-A0), energetic particle density profiles and toroidal modes (n) including toroidal and helical couplings. The study predicts a large helical coupling between different toroidal modes and the destabilization of helical Alfven eigenmodes (HAE) with frequencies similar to the AE activity measured in TJ-II, between 50-400 kHz. The analysis has also revealed the destabilization of GAE (global Alfven eigenmodes), TAE (toroidal Alfven eigenmodes) and EPM (energetic particle modes). For the modes considered here, optimized TJ-II operations require a t profile in the range of [0.845, 0.979] to stabilize AEs in the inner and middle plasma. AEs in the plasma periphery cannot be fully stabilized, although for a configuration with t = [0.945, 1.079], only n = 7, 11, 15 AE are unstable with a growth rate 4 times smaller compared to the standard t = [1.54, 1.68] case and a frequency of 100 kHz. We reproduce the frequency sweeping evolution of the AE frequency observed in TJ-II as the t profile is varied. The AE frequency sweeping is caused by consecutive changes of the instability dominant modes between different helical families.This material based on work is supported both by the U.S. Department of Energy, Office of Science, under Contract DE-AC05-00OR22725 with UT-Battelle, LLC. This research was sponsored in part by the Ministerio of Economia y Competitividad of Spain under project no. ENE2015-68265-P. We also want to acknowledge Alexander Melnikov and the TJ-II group at CIEMAT for providing us the initial VMEC equilibria and useful discussions regarding the experimental phenomena
Defining and measuring âeczema controlâ: An international qualitative study to explore the views of those living with and treating atopic eczema
Background
Atopic eczema (also known as eczema) is a chronic, inflammatory skin condition that often afflicts patientsâ health and wellbeing. The Harmonising Outcome Measures for Eczema (HOME) initiative recommends that âlong-term control of eczemaâ is measured in all clinical trials 3 months or longer in duration. However, little has been published on what eczema control means to those living with or treating atopic eczema.
Objectives
To i) develop understanding of what eczema control means to patients, carers and clinicians and ii) explore the feasibility and acceptability of different ways of measuring eczema control in the long-term.
Methods
Online focus groups explored patients/carers experiences in the UK, USA, the Netherlands, France, Sweden and Japan, and an international online survey gathered views of clinicians. The Framework Method was used to analyse the focus groups and thematic analysis was used to analyse survey data. All findings were integrated into a theoretical framework to create overarching themes that cut across these diverse groups.
Results
Eight focus groups with patients (16 years+) and eight groups with carers of children took place (N=97). Sixty-two people took part in the survey. Eczema control was described as a multifaceted construct involving changes in disease activity, the treatment and management of the condition, and psychological, social and physical functioning. Patient /carer measurement allows personal accounts and frequent measurement, whilst clinician measurement was deemed less subjective. The burden on patients/carers and issues for analysing and interpreting data should be considered.
Conclusions
This study formed the basis of judging the content validity and feasibility of measurement instruments/methods to assess control of eczema in clinical trials. This online approach to an international qualitative study is an example of how core outcome set developers with limited resources can engage with multiple stakeholder groups on an international basis to inform consensus meeting discussions
The development of Scotlandâs Curriculum for Excellence: Amnesia and DĂ©jĂ Vu
Scotlandâs new Curriculum for Excellence (CfE) has been widely acknowledged as the most significant educational development in a generation, with the potential to transform learning and teaching in Scottish schools. In common with recent developments elsewhere, CfE seeks to re-engage teachers with processes of curriculum development, to place learning at the heart of the curriculum and to change engrained practices of schooling. This article draws upon well-established curriculum theory (notably the work of both Lawrence Stenhouse and A.V. Kelly) to analyse the new curriculum. We argue that by neglecting to take account of such theory, the curricular offering proposed by CfE is subject to a number of significant structural contradictions which may affect the impact that it ultimately exerts on learning and teaching; in effect, by ignoring the lessons of the past, CfE runs the risk of undermining the potential for real change
Ferromagnetic Convection in a Heterogeneous Darcy Porous Medium Using a Local Thermal Non-equilibrium (LTNE) Model
Building resilience from the ground up
This paper provides an overview and commentary on a special issue of the journal Disasters that reflects on experiences in resilience-building. Experiences are drawn from two recent DfID-funded programmes in some of the worldâs most climate-vulnerable countries and contexts. These programmes have focused on scaling up action to build resilience, principally through the expansion and replication of good practices by influencing government policies, plans and investments. The papers provide insights that are each grounded in different contexts and understandings of local realities and the factors that support and undermine
peopleâs resilience
Prospects for e+e- physics at Frascati between the phi and the psi
We present a detailed study, done in the framework of the INFN 2006 Roadmap,
of the prospects for e+e- physics at the Frascati National Laboratories. The
physics case for an e+e- collider running at high luminosity at the phi
resonance energy and also reaching a maximum center of mass energy of 2.5 GeV
is discussed, together with the specific aspects of a very high luminosity
tau-charm factory. Subjects connected to Kaon decay physics are not discussed
here, being part of another INFN Roadmap working group. The significance of the
project and the impact on INFN are also discussed. All the documentation
related to the activities of the working group can be found in
http://www.roma1.infn.it/people/bini/roadmap.html.Comment: INFN Roadmap Report: 86 pages, 25 figures, 9 table
NMR study of reorientational motion of BH4 groups in bimetallic borohydrides A[Al(BH4)4] (A = Na, K, Rb, and Cs) (poster)
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