From least action in electrodynamics to magnetomechanical energy -- a review

The equations of motion for electromechanical systems are traced back to the fundamental Lagrangian of particles and electromagnetic fields, via the Darwin Lagrangian. When dissipative forces can be neglected the systems are conservative and one can study them in a Hamiltonian formalism. The central concepts of generalized capacitance and inductance coefficients are introduced and explained. The problem of gauge independence of self-inductance is considered. Our main interest is in magnetomechanics, i.e. the study of systems where there is exchange between mechanical and magnetic energy. This throws light on the concept of magnetic energy, which according to the literature has confusing and peculiar properties. We apply the theory to a few simple examples: the extension of a circular current loop, the force between parallel wires, interacting circular current loops, and the rail gun. These show that the Hamiltonian, phase space, form of magnetic energy has the usual property that an equilibrium configuration corresponds to an energy minimum.Comment: 29 pages, 9 figures, 65 reference

The Mini-FLOTAC technique for the diagnosis of helminth and protozoan infections in humans and animals

This protocol is an extension to: Nat. Protoc. 5, 503–515 (2010). DOI: 10.1038/nprot.2009.235; The FLOTAC is a sensitive, accurate, and precise technique for the diagnosis of protozoan and helminth infections in humans and animals. However, it requires centrifugation, and hence might be out of reach in resource-constrained settings. As an extension of the original FLOTAC protocol, this protocol describes the Mini-FLOTAC technique, a logical evolution of FLOTAC conceived to perform multivalent, qualitative, and quantitative diagnosis of helminth and protozoan infections in human and animal feces, and urine. This has been found to be of most use in the processing of large numbers of samples with rapid laboratory workup, and for veterinary applications directly on-farm. In addition to the Mini-FLOTAC apparatus, we describe the use of the Fill-FLOTAC, a closed system used to facilitate the performance of the first four consecutive steps of the Mini-FLOTAC technique: fecal sample collection and weighing, homogenization, filtration, and filling of the Mini-FLOTAC chambers. Processing of an individual sample using this protocol requires ∼12 min