Dynamo in Weakly Collisional Nonmagnetized Plasmas Impeded by Landau Damping of Magnetic Fields

We perform fully kinetic simulations of flows known to produce dynamo in magnetohydrodynamics (MHD), considering scenarios with low Reynolds number and high magnetic Prandtl number, relevant for galaxy cluster scale fluctuation dynamos. We find that Landau damping on the electrons leads to a rapid decay of magnetic perturbations, impeding the dynamo. This collisionless damping process operates on spatial scales where electrons are nonmagnetized, reducing the range of scales where the magnetic field grows in high magnetic Prandtl number fluctuation dynamos. When electrons are not magnetized down to the resistive scale, the magnetic energy spectrum is expected to be limited by the scale corresponding to magnetic Landau damping or, if smaller, the electron gyroradius scale, instead of the resistive scale. In simulations we thus observe decaying magnetic fields where resistive MHD would predict a dynamo

Conformational changes of calmodulin upon Ca2+ binding studied with a microfluidic mixer

A microfluidic mixer is applied to study the kinetics of calmodulin conformational changes upon Ca2+ binding. The device facilitates rapid, uniform mixing by decoupling hydrodynamic focusing from diffusive mixing and accesses time scales of tens of microseconds. The mixer is used in conjunction with multiphoton microscopy to examine the fast Ca2+-induced transitions of acrylodan-labeled calmodulin. We find that the kinetic rates of the conformational changes in two homologous globular domains differ by more than an order of magnitude. The characteristic time constants are ≈490 μs for the transitions in the C-terminal domain and ≈20 ms for those in the N-terminal domain of the protein. We discuss possible mechanisms for the two distinct events and the biological role of the stable intermediate, half-saturated calmodulin

Additions, corrections and nomenclatural updates to "Mariposas de Venezuela" by Th\ue9ophile Raymond. IV. Pieridae and Hesperiidae (Lepidoptera)

The species of Pieridae portrayed in the watercolor paintings of "Mariposas de Venezuela" by Th\ue9ophile Raymond (1982, Ediciones Corpoven, Caracas) are identified herein. Two skippers, erroneously identified by Orellana et al (2002, Entomotropica 17(1): 107 - 109) are corrected herein. Comments to improve the knowledge on some species are included.Se identifican las especies de mariposas de la familia Pieridae que aparecen en las acuarelas del libro "Mariposas de Venezuela" de Th\ue9ophile Raymond (1982, Ediciones Corpoven, Caracas). Se corrigen, adem\ue1s, las identificaciones err\uf3neas de dos especies de Hesperiidae tratadas en Orellana et al. (2002, Entomotropica 17(1): 107 - 109). Comentarios para algunas de las especies citadas son incorporados al texto con la intenci\uf3n de facilitar y ayudar en su conocimiento