Solution of an industrially relevant coupled magneto–mechanical problem set on an axisymmetric domain

Eddy currents are generated when low frequency magnetic fields interact with conducting components and this, in turn, generates Lorentz forces, which can cause these metallic components to deform and vibrate. An important application of this magneto–mechanical coupling is in coil design for magnetic resonance imaging scanners, where such vibrations can have unwanted effects such as ghosting of images, reduction of the life span of devices and discomfort for the patient. This work is aimed at developing an accurate computational tool for better understanding these deformations by considering a benchmark problem proposed by Siemens plc (Kruip, personal communication, 2013) on an idealised axisymmetric geometry. We present a new fixed point algorithm and develop new weak variational statements, which use a stress tensor approach for force calculation and permit discretisation using H1 conforming hp-version finite elements. Numerical results are included, which show the importance of high order finite elements for predicting the eddy currents and the associated coupling in the resonance region

A Survey in Mathematics for Industry - An efficient method for the numerical simulation of magneto-mechanical sensors and actuators

The dynamic behaviour of magneto-mechanical sensors and actuators can be completely described by Maxwell's and Navier-Lamé's partial differential equations (PDEs) with appropriate coupling terms reflecting the interactions of these fields and with the corresponding initial, boundary and interface conditions. Neglecting the displacement currents, which can be done for the classes of problems considered in this paper, and introducing the vector potential for the magnetic field, we arrive at a system of degenerate parabolic PDEs for the vector potential coupled with the hyperbolic PDEs for the displacements.Usually the computational domain, the finite element discretization, the time integration, and the solver are different for the magnetic and mechanical parts. For instance, the vector potential is approximated by edge elements whereas the finite element discretization of the displacements is based on nodal elements on different meshes. The most time consuming modules in the solution procedure are the solvers for both, the magnetical and the mechanical finite element equations arising at each step of the time integration procedure. We use geometrical multigrid solvers which are different for both parts. These multigrid solvers enable us to solve quite efficiently not only academic test problems, but also transient 3D technical magneto-mechanical systems of high complexity such as solenoid valves and electro-magnetic-acoustic transducers. The results of the computer simulation are in very good agreement with the experimental data

New chromosome counts and other karyological data for members of the Stemonaceae

Chromosome numbers and other karyological data for ten Stemona species and for Stichoneuron caudatum are presented, including first reports for Stemona burkillii, S. involuta, S. mairei and S. phyllantha.All investigated taxa of Stemona exhibit n = x = 7 (2n = 14) chromosomes. For Stichoneuron caudatum an earlier count revealing 2n = 18 is confirmed. The observed chromosome lengths range between 0.9 and 6.9 μm (largest chromosome in Stichoneuron caudatum).Additionally, the genome sizes of seven Stemona species and of Stichoneuron caudatum are reported. The obtained results are compared with literature data and discussed

Phytochemistry Meets Geochemistry—Blumenol C Sulfate: A New Megastigmane Sulfate from Palicourea luxurians (Rubiaceae: Palicoureeae)

There is a previously neglected influence of geochemical conditions on plant phytochemistry. In particular, high concentrations of dissolved salts can affect their biosynthesis of natural products. Detoxification is most likely an important aspect for the plant, but additional natural products can also give it an expanded range of bioactivities. During the phytochemical analysis a Palicourea luxurians plant collected in a sulfate-rich environment (near the Río Sucio, Costa Rica) showed an interesting natural product in this regard. The structure of this compound was determined using spectroscopic and computational methods (NMR, MS, UV, IR, CD, optical rotation, quantum chemical calculations) and resulted in a megastigmane sulfate ester possessing a β-ionone core structure, namely blumenol C sulfate (1, C13H22O5S). The levels of sulfur and sulfate ions in the leaves of the plant were determined using elemental analysis and compared to the corresponding levels in comparable plant leaves from a less sulfate-rich environments. The analyses show the leaves from which we isolated blumenol C sulfate (1) to contain 35% more sulfur and 80% more sulfate than the other samples. Antimicrobial and antioxidant activities of compound 1 were tested against Escherichia coli, E. coli ampR and Bacillus subtilis as well as measured using complementary in vitro FRAP and ATBS assays, respectively. These bioactivities are comparable to those determined for structurally related megastigmanes. The sulfur and sulfate content of the plant leaves from the sulfate-rich environment was significantly higher than that of the other plants. Against this background of salt stress, we discuss a possible biosynthesis of blumenol C sulfate (1). Furthermore, there appears to be no benefit for the plant in terms of extended bioactivities. Hence, the formation of blumenol C sulfate (1) probably primarily serves the plant detoxification process