A particle model of rolling grain ripples under waves

A simple model is presented for the formation of rolling grain ripples on a flat sand bed by the oscillatory flow generated by a surface wave. An equation of motion is derived for the individual ripples, seen as "particles", on the otherwise flat bed. The model account for the initial apperance of the ripples, the subsequent coarsening of the ripples and the final equilibrium state. The model is related to physical parameters of the problem, and an analytical approximation for the equilibrium spacing of the ripples is developed. It is found that the spacing between the ripples scale with the square-root of the non-dimensional shear stress (the Shields parameter) on a flat bed. The results of the model are compared with measurements, and reasonable agreement between the model and the measurements is demonstrated.Comment: 9 pages incl. figures. Revised versio

Validity and worth in the science curriculum: learning school science outside the laboratory

It is widely acknowledged that there are problems with school science in many developed countries of the world. Such problems manifest themselves in a progressive decline in pupil enthusiasm for school science across the secondary age range and the fact that fewer students are choosing to study the physical sciences at higher levels and as careers. Responses to these developments have included proposals to reform the curriculum, pedagogy and the nature of pupil discussion in science lessons. We support such changes but argue from a consideration of the aims of science education that secondary school science is too rooted in the science laboratory; substantially greater use needs to be made of out-of-school sites for the teaching of science. Such usage should result in a school science education that is more valid and more motivating and is better at fulfilling defensible aims of school science education. Our contention is that laboratory-based school science teaching needs to be complemented by out-of-school science learning that draws on the actual world (e.g. through fieldtrips), the presented world (e.g. in science centres, botanic gardens, zoos and science museums) and the virtual worlds that are increasingly available through information and communications technologies (ICT)

Wall conditions in ORMAK

From surface effects in controlled thermonuclear fusion devices and reactors meeting; Argonne, Illnois, USA (10 Jan 1974). ORMAK is a diffuse toroidal pinch with typical plasma currents of 100 kA, electron temperatures of 800 eV, and ion temperatures of 300 eV. The walls of the plasma region are made of stainless steel coated with an intermediate layer of platinum 0.05 mu thick and an outer 1 to 2 mu layer of gold. Tests with an Ion Microprobe Mass Analyzer have shown that the platinum acts to decrease diffusion of impurities from the stalnless steel to the surface. Gold was chosen to inhibit the surface chemical adsorption of gases. Studies with a movable limiter indicate that electron energy is lost at the plasma edge mainly via line radiation and cooling on ions, while ions are lost from the plasma by charge exchange. Thus the walls are bombarded by energetic neutrals, line radiation and, in addition, bremsstrahlung x-rays. The flux of energetic neutrals is measured by a charge exchange analyzer. Wall bombardment by such neutrals should cause sputtering, and gold has been observed spectroscopically near the limiter, increasing with time during a shot, However, analysis of impurities coated on a window by the discharge indicated very little gold sputtering and re-deposition. To measure the sputterirg rate, a wall sample was coated with 105 A of radioactive gold and bombarded with neutrals from ORMAK during a day's run. No measurable sputtering was found within the counting statistics of the measurement, but surface carbon contamination of the sample prevented any final conclusions. (auth

Social representations and the politics of participation

Recent work has called for the integration of different perspectives into the field of political psychology (Haste, 2012). This chapter suggests that one possible direction that such efforts can take is studying the role that social representations theory (SRT) can play in understanding political participation and social change. Social representations are systems of common-sense knowledge and social practice; they provide the lens through which to view and create social and political realities, mediate people's relations with these sociopolitical worlds and defend cultural and political identities. Social representations are therefore key for conceptualising participation as the activity that locates individuals and social groups in their sociopolitical world. Political participation is generally seen as conditional to membership of sociopolitical groups and therefore is often linked to citizenship. To be a citizen of a society or a member of any social group one has to participate as such. Often political participation is defined as the ability to communicate one's views to the political elite or to the political establishment (Uhlaner, 2001), or simply explicit involvement in politics and electoral processes (Milbrath, 1965). However, following scholars on ideology (Eagleton, 1991; Thompson, 1990) and social knowledge (Jovchelovitch, 2007), we extend our understanding of political participation to all social relations and also develop a more agentic model where individuals and groups construct, develop and resist their own views, ideas and beliefs. We thus adopt a broader approach to participation in comparison to other political-psychological approaches, such as personality approaches (e.g. Mondak and Halperin, 2008) and cognitive approaches or, more recently, neuropsychological approaches (Hatemi and McDermott, 2012). We move away from a focus on the individual's political behaviour and its antecedents and outline an approach that focuses on the interaction between psychological and political phenomena (Deutsch and Kinnvall, 2002) through examining the politics of social knowledge

Physics of Target Plasmas in Minimum-B Geometries

Provides efficient targets for accumulation of a hot-ion plasma by energetic neutral injection

Dynamical models for sand ripples beneath surface waves

We introduce order parameter models for describing the dynamics of sand ripple patterns under oscillatory flow. A crucial ingredient of these models is the mass transport between adjacent ripples, which we obtain from detailed numerical simulations for a range of ripple sizes. Using this mass transport function, our models predict the existence of a stable band of wavenumbers limited by secondary instabilities. Small ripples coarsen in our models and this process leads to a sharply selected final wavenumber, in agreement with experimental observations.Comment: 9 pages. Shortened version of previous submissio

The masculine logic of DDR and SSR in the Rwanda Defence Force

Since the 1994 genocide and civil war, the Rwandan government has implemented an externally funded Demobilisation, Demilitarisation and Reintegration (DDR)/Security Sector Reform (SSR) program culminating in the consolidation of armed groups into a new, professionalised Rwanda Defence Force (RDF). Feminists argue that DDR-SSR initiatives that exclude combatant women and girls or ignore gendered security needs fail to transform the political conditions that led to conflict. Less attention has been paid to how gendered relations of power play out through gender sensitive DDR and SSR initiatives that seek to integrate women and transform hyper-masculine militarised masculinities. This article investigates how Rwanda’s DDR-SSR program is governed by an oppressive masculine logic. Drawing on critical studies on men and masculinities and feminist work on peacebuilding, myths and the politics of belonging, it is argued that Rwanda’s locally-owned DDR-SSR program places the military and militarisation at the centre of the nation-building program. Through various ‘boundary construction’ practices, the Rwandan government attempts to stabilise the post-1994 gender order and entrench the hegemony of a new militarised masculinity in Rwandan society. The case study draws on field research conducted in 2014 and 2015 and a discourse analysis of RDF historical accounts, policy documents and training materials

Identification of B Cell Epitopes of Alcohol Dehydrogenase Allergen of Curvularia lunata

BACKGROUND/OBJECTIVE: Epitope identification assists in developing molecules for clinical applications and is useful in defining molecular features of allergens for understanding structure/function relationship. The present study was aimed to identify the B cell epitopes of alcohol dehydrogenase (ADH) allergen from Curvularia lunata using in-silico methods and immunoassay. METHOD: B cell epitopes of ADH were predicted by sequence and structure based methods and protein-protein interaction tools while T cell epitopes by inhibitory concentration and binding score methods. The epitopes were superimposed on a three dimensional model of ADH generated by homology modeling and analyzed for antigenic characteristics. Peptides corresponding to predicted epitopes were synthesized and immunoreactivity assessed by ELISA using individual and pooled patients' sera. RESULT: The homology model showed GroES like catalytic domain joined to Rossmann superfamily domain by an alpha helix. Stereochemical quality was confirmed by Procheck which showed 90% residues in most favorable region of Ramachandran plot while Errat gave a quality score of 92.733%. Six B cell (P1-P6) and four T cell (P7-P10) epitopes were predicted by a combination of methods. Peptide P2 (epitope P2) showed E(X)(2)GGP(X)(3)KKI conserved pattern among allergens of pathogenesis related family. It was predicted as high affinity binder based on electronegativity and low hydrophobicity. The computational methods employed were validated using Bet v 1 and Der p 2 allergens where 67% and 60% of the epitope residues were predicted correctly. Among B cell epitopes, Peptide P2 showed maximum IgE binding with individual and pooled patients' sera (mean OD 0.604±0.059 and 0.506±0.0035, respectively) followed by P1, P4 and P3 epitopes. All T cell epitopes showed lower IgE binding. CONCLUSION: Four B cell epitopes of C. lunata ADH were identified. Peptide P2 can serve as a potential candidate for diagnosis of allergic diseases