Structure of the Wake of a Magnetic Obstacle

We use a combination of numerical simulations and experiments to elucidate the structure of the flow of an electrically conducting fluid past a localized magnetic field, called magnetic obstacle. We demonstrate that the stationary flow pattern is considerably more complex than in the wake behind an ordinary body. The steady flow is shown to undergo two bifurcations (rather than one) and to involve up to six (rather than just two) vortices. We find that the first bifurcation leads to the formation of a pair of vortices within the region of magnetic field that we call inner magnetic vortices, whereas a second bifurcation gives rise to a pair of attached vortices that are linked to the inner vortices by connecting vortices.Comment: 4 pages, 5 figures, corrected two typos, accepted for PR

Flow and magnetic structures in a kinematic ABC-dynamo

Dynamo theory describes the magnetic field induced by the rotating, convecting and electrically conducting fluid in a celestial body. The classical ABC-flow model represents fast dynamo action, required to sustain such a magnetic field. In this letter, Lagrangian coherent structures (LCSs) in the ABC-flow are detected through Finite-time Lyapunov exponents (FTLE). The flow skeleton is identified by extracting intersections between repelling and attracting LCSs. For the case A = B = C = 1, the skeleton structures are made up from lines connecting two different types of stagnation points in the ABC-flow. The corresponding kinematic ABC-dynamo problem is solved using a spectral method, and the distribution of cigar-like magnetic structures visualized. Inherent links are found to exist between LCSs in the ABC-flow and induced magnetic structures, which provides insight into the mechanism behind the ABC-dynamo

Comparative efficacy and safety of bifonazole 1% cream and the corresponding base preparation in the treatment of seborrhoeic dermatitis

Zienicke H, Korting HC, Braun-Falco O, et al. Comparative efficacy and safety of bifonazole 1% cream and the corresponding base preparation in the treatment of seborrhoeic dermatitis . Mycoses. 1993;36(9-10):325-331.Seborrhoeic dermatitis is a common entity that conventionally is difficult to treat. Recently, topical ketoconazole has been proven successful. To determine if other azoles, and in particular the more modern ones, are also helpful in this condition, a double-blind multicentre randomized controlled trial was performed in patients suffering from seborrhoeic dermatitis involving individuals 16 years and older without human immunodeficiency virus (HIV) infection. One hundred patients were enrolled and treated according to a random plan with either bifonazole 1% cream or the corresponding vehicle once daily for 4 weeks. All patients were evaluated at the beginning of the study, as well as after 2 and 4 weeks, i.e. the treatment period proper, and after 6 weeks of follow-up. Clinical evaluation was based on scores of 0-3 for the following parameters: erythema, papules, infiltration, scaling, itch. In addition, mycological evaluation was performed using adequate contact plates for quantitative determination of Malassezia furfur. In the end, 92 patients were at least partially evaluable. In general, the verum preparation tended to be more efficacious, e.g. the score for erythema amounted to 0.75 after 4 weeks as compared with 0.88 in the control group, the baseline values being 2.18 and 2.04 respectively. With itch, the corresponding figures were 0.17 and 0.33 as compared with 1.42 and 1.38 before treatment. While in statistical terms there was significant difference in these parameters, such a difference was demonstrated by clinical judgement at follow-up. In the verum group (n=37) 10 and 24 patients respectively were cured or improved; the corresponding figures for the control group (n=43) were 9 and 23 (P=0.1). Differences in M. furfur colonization in favour of the verum preparation were not significant. Accordingly, there was no major difference in terms of the overall clinical and mycological cure rate in both groups, originally defined as a major test parameter. Bifonazole 1% cream might be helpful clinically in seborrhoeic dermatitis of non-HIV-infected patients. For definite proof of this hypothesis another confirmatory trial is needed, which should be based solely on global clinical judgement

Confinement and bursty transport in a flux-driven convection model with sheared flows

Transport and confinement within the resistive-g paradigm are investigated by means of two-dimensional numerical simulations. The system is driven by a constant incoming heat flux at the inner radial boundary. Different confinement and transport states are identified, involving self-sustained sheared poloidal flows. At the onset of turbulent convection the probability distribution functions of pressure and radial velocity fluctuations measured in the centre of the plasma layer have a nearly Gaussian form. Further increasing the heat flux drive these distributions become increasingly non-Gaussian, developing exponential tails. This large-scale intermittency is ascribed to the presence of bursting in the domain averaged convective transport and the fluctuation energy integrals. The quasi-periodic bursts are separated by shear-dominated quiescent periods in which the mean flow energy decreases and the confined heat increases on diffusive timescales. The time-averaged thermal energy confined within the plasma layer shows a power law dependence and significant increase with the injected power over the range of turbulent convection investigated