Hydrodynamic synchronization of flagellar oscillators

We survey the theory synchronization in collections of noisy oscillators. This framework is applied to flagellar synchronization by hydrodynamic interactions. The time-reversibility of hydrodynamics at low Reynolds numbers prompts swimming strokes that break symmetry to facilitate hydrodynamic synchronization. We discuss different physical mechanisms for flagellar synchronization, which break this symmetry in different ways.Comment: 15 pages, 3 figures; accepted for publication in EPJ Special Topics Issue,Lecture Notes of the Summer School "Microswimmers -- From Single Particle Motion to Collective Behaviour'', organised by the DFG Priority Programme SPP 1726 (Forschungszentrum J\"ulich, J\"ulich, 2015

Synopsis of Mid-latitude Radio Wave Absorption in Europe

Radio wave absorption data covering almost two years from Europe to Central Asia are presented. They are normalized by relating them to a reference absorption. Every day these normalized data are fitted to a mathematical function of geographical location in order to obtain a daily synopsis of radio wave absorption. A film of these absorption charts was made which is intended to reveal movements of absorption or absorption anomaly. In addition, radiance (temperature) data from the lower D-region are also plotted onto these charts

Case study of modeled and measured D-region plasma densities

Two of the many sounding rockets launched as part of the MAC/Epsilon campaign are particularly suited to test the validity or quality of D region models. The measurements covered atomic oxygen, neutral temperatures and fluxes of charged particles. With these parameters as inputs, one is thus in the position to assess their relevance for the measured parameters, i.e., ion composition, transition heights of clusters and negative ions and total plasma density. The two IOMAS payloads are believed to be the only night flights with associated measurements of atomic oxygen extending below the ledge at about 80 km

A three-sphere swimmer for flagellar synchronization

In a recent letter (Friedrich et al., Phys. Rev. Lett. 109:138102, 2012), a minimal model swimmer was proposed that propels itself at low Reynolds numbers by a revolving motion of a pair of spheres. The motion of the two spheres can synchronize by virtue of a hydrodynamic coupling that depends on the motion of the swimmer, but is rather independent of direct hydrodynamic interactions. This novel synchronization mechanism could account for the synchronization of a pair of flagella, e.g. in the green algae Chlamydomonas. Here, we discuss in detail how swimming and synchronization depend on the geometry of the model swimmer and compute the swimmer design for optimal synchronization. Our analysis highlights the role of broken symmetries for swimming and synchronization.Comment: 25 pages, 4 color figures, provisionally accepted for publication in the New Journal of Physic