A Lagrangian kinetic model for collisionless magnetic reconnection

A new fully kinetic system is proposed for modeling collisionless magnetic reconnection. The formulation relies on fundamental principles in Lagrangian dynamics, in which the inertia of the electron mean flow is neglected in the expression of the Lagrangian, rather then enforcing a zero electron mass in the equations of motion. This is done upon splitting the electron velocity into its mean and fluctuating parts, so that the latter naturally produce the corresponding pressure tensor. The model exhibits a new Coriolis force term, which emerges from a change of frame in the electron dynamics. Then, if the electron heat flux is neglected, the strong electron magnetization limit yields a hybrid model, in which the electron pressure tensor is frozen into the electron mean velocity.Comment: 15 pages, no figures. To Appear in Plasma Phys. Control. Fusio

Molecular characterization of Cryptosporidium and Giardia in farmers and their ruminant livestock from the Coastal Savannah zone of Ghana

Cryptosporidium and Giardia are major causes of diarrhoea in developing countries including Ghana, however, nothing is known about the species and subtypes of Cryptosporidium and Giardia in farmers and their ruminant livestock in this country. A total of 925 faecal samples from humans (n = 95), cattle (n = 328), sheep (n = 217) and goats (n = 285), were screened for Cryptosporidium and Giardia by quantitative PCR (qPCR) at the 18S rRNA and glutamate dehydrogenase (gdh) loci respectively. Cryptosporidium positives were typed by sequence analysis of 18S and 60 kDa glycoprotein (gp60) loci amplicons. Giardia positives were typed at the triose phosphate isomerase (tpi), beta-giardin (bg) and gdh loci. The prevalence of Cryptosporidium and Giardia by qPCR was 8.4% and 10.5% in humans, 26.5% and 8.5% in cattle, 34.1% and 12.9% in sheep, and 33.3% and 12.3% in goat faecal samples, respectively. G. duodenalis assemblages A and B were detected in humans and assemblage E was detected in livestock. Cryptosporidium parvum was the only species identified in humans; C. andersoni, C. bovis, C. ryanae and C. ubiquitum were identified in cattle; C. xiaoi, C. ubiquitum and C. bovis in sheep; and C. xiaoi, C. baileyi and C. parvum in goats. This is the first molecular study of Cryptosporidium and Giardia in livestock in Ghana. The identification of zoonotic species and the identification of C. parvum subtype IIcA5G3q in livestock, which has previously been identified in children in Ghana, suggests potential zoonotic transmission. Further studies on larger numbers of human and animal samples, and on younger livestock are required to better understand the epidemiology and transmission of Cryptosporidium and Giardia in Ghana

Shadow Pricing and Macroeconomic Analysis: Some Illustrations from Pakistan

Shadow prices are being used increasingly in the economic analysis of projects. The purpose of this paper, however, is to argue that shadow prices are equally relevant for certain types of analysis at the macro-economic level. In theory, macroeconomic issues can be properly analyzed, if at all, only in general equilibrium frame• work. Quantification then requires the solution of an appropriate model. But, estimable general equilibrium models can seldom include many variables, and the level of aggregation must remain high. They are general only in the very partial sense of simultaneous solution of a limited set of aggregated endogenous variables. On the other hand, some of the issues addressed by shadow pricing involve quite disaggregated variables, and, of course, project analysis itself often requires very detailed estimations

Finite depth effects on solitary waves in a floating ice sheet

A theoretical and numerical study of two-dimensional nonlinear flexural-gravity waves propagating at the surface of an ideal fluid of finite depth, covered by a thin ice sheet, is presented. The ice-sheet model is based on the special Cosserat theory of hyperelastic shells satisfying Kirchhoff׳s hypothesis, which yields a conservative and nonlinear expression for the bending force. From a Hamiltonian reformulation of the governing equations, two weakly nonlinear wave models are derived: a 5th-order Korteweg–de Vries equation in the long-wave regime and a cubic nonlinear Schrödinger equation in the modulational regime. Solitary wave solutions of these models and their stability are analysed. In particular, there is a critical depth below which the nonlinear Schrödinger equation is of focusing type and thus admits stable soliton solutions. These weakly nonlinear results are validated by comparison with direct numerical simulations of the full governing equations. It is observed numerically that small- to large-amplitude solitary waves of depression are stable. Overturning waves of depression are also found for low wave speeds and sufficiently large depth. However, solitary waves of elevation seem to be unstable in all cases

The stability of capillary waves on fluid sheets

The linear stability of finite amplitude capillary waves on inviscid sheets of fluid is investigated. A method similar to that recently used by Tiron & Choi (2012) to determine the stability of Crapper waves on fluid of infinite depth is developed by extending the conformal mapping technique of Dyachenko et al. (1996a) to a form capable of capturing general periodic waves on both the upper and the lower surface of the sheet, including the symmetric and antisymmetric waves studied by Kinnersley (1976). The primary, surprising result is that both symmetric and antisymmetric Kinnersley waves are unstable to small superharmonic disturbances. The waves are also unstable to subharmonic perturbations. Growth rates are computed for a range of steady waves in the Kinnersley family, and also waves found along the bifurcation branches identified by Blyth & Vanden-Broeck (2004). The instability results are corroborated by time integration of the fully nonlinear unsteady equations. Evidence is presented for superharmonic instability of nonlinear waves via a collision of eigenvalues on the imaginary axis which appear to have the same Krein signature

The Long and Winding Road: Archiving and Re-Using Qualitative Data from 12 Research Projects Spanning 16 Years

We describe a pilot project designed to assess the feasibility of re-use across 12 diverse qualitative datasets related to Human Immunodeficiency Virus (HIV) in the UK, from research projects undertaken between 1997 and 2013 – an approach which is chronically underused. First, we consider the sweeping biomedical changes and imperatives relating to HIV in this time frame, offering a rationale for data re-use at this point in the epidemic. We then reflexively situate the processes and procedures we devised for this study with reference to relevant methodological literature. Hammersley’s and Leonelli’s contributions have been particularly instructive through this process, and following their lead, we conclude with further considerations for those undertaking qualitative data re-use, reflecting on the extent to which qualitative data re-use as a practice requires attention to both the given and the constructed aspects of data when assembled as evidence

Economic evaluation of short treatment for multidrugresistant tuberculosis, Ethiopia and South Africa : the STREAM trial

OBJECTIVE STREAM was a phase-III non-inferiority randomised controlled trial (RCT) to evaluate a shortened regimen for multi-drug resistant tuberculosis (MDR-TB), and included the first-ever within-trial economic evaluation of such regimens, reported here. METHODS We compared the costs of ‘Long’ (20-22 months) and ‘Short’ (9-11 months) regimens in Ethiopia and South Africa. Cost data were collected from trial participants, and health system costs estimated using ‘bottom-up’ and ‘top-down’ costing approaches. A cost-effectiveness analysis was conducted with the trial primary outcome as the measure of effectiveness, including a probabilistic sensitivity analysis (PSA) to illustrate decision uncertainty. FINDINGS The Short-regimen reduced healthcare costs per case by 21% in South Africa (US$8,341 Long vs US$6,619 Short) and 25% in Ethiopia (US$6,097 Long vs US$4,552 Short). The largest component of this saving was medication in South Africa (67%) and social support in Ethiopia (35%). In Ethiopia, participants on the Short-regimen reported reductions in dietary supplementation expenditure (US$225 per case (95$13 (95%CI 11-14), South Africa US$64 (95$19,000 (Ethiopia) or <US$14,500 (South Africa). CONCLUSION The Short-regimen provided substantial health system cost savings and reduced financial burden on participants. Shorter regimens are likely to be cost-effective in most settings, and an effective strategy to support the WHO goal of eliminating catastrophic costs in T

The gaming involvement and informal learning framework

Aim. This article presents a model of how gaming involvement and informal learning come together in practice. Method. Based on a series of interviews, case studies, and a wider survey, the Gaming Involvement and Informal Learning (GIIL) framework indicates how involvement with a variety of gaming practices can lead to a range of different learning experiences. Results. The framework is able to account for both how and what people learn from gaming while also highlighting the influence of player identity. Further, the iterative relationship between identity, involvement, and learning is emphasized: The more strongly someone identifies themselves as a gamer, the greater their micro- and macro-level involvement and the more likely they are to learn from their gaming experiences. Conclusion. The implications of the findings are discussed with regard to informal and formal learning