Ostwald ripening, chiral crystallization, and the common-ancestor effect

We introduce an agent-based model for advection-mediated chiral autocatalysis in which we take into account dissolution-crystallization processes through Ostwald ripening. We demonstrate that the latter phenomenon is the key to explaining previously puzzling experimental results whereby complete chiral symmetry breaking is attained from an initially unbiased mixture of seed crystals. We show that this homochirality is achieved by what has been termed the common-ancestor effect: Ostwald ripening removes competing lineages, leaving only one common ancestor for the entire system.     

A microscopic mechanism for ultrasonic attenuation in KDP

The pseudo-spin model of KDP is extended to include modulation of the dipole-dipole separation by longitudinal acoustic phonons. This coupling is shown to give rise to attenuation of transverse sound in the paraelectric region, in agreement with experiment. The calculation has been performed using the approximation. The contribution of this coupling to the ferroelectric mode has also been calculated.     

Bailout embeddings and neutrally buoyant particles in three-dimensional flows

We use the bailout embeddings of three-dimensional volume-preserving maps to study qualitatively the dynamics of small spherical neutrally buoyant impurities suspended in a time-periodic incompressible fluid flow. The accumulation of impurities in tubular vortical structures, the detachment of particles from fluid trajectories near hyperbolic invariant lines, and the formation of nontrivial three-dimensional structures in the distribution of particles are predicted.     

Control of particles in microelectrode devices

The impact of the convective fluid motion induced by the electric fields on the dielectrophoretic manipulation of particles is investigated theoretically and experimentally. By means of a simplified model a channel with a periodic array of microelectrodes we show that electroconvective flows induce the formation of traps for particles, providing a dynamical mechanism to control microparticles in such devices. We demonstrate experimentally the theoretically predicted dynamical phenomena.     

Emergence of synchronized beating during the regrowth of eukaryotic flagella

A fundamental issue in the biology of eukaryotic flagella is the origin of synchronized beating observed in tissues and organisms containing multiple flagella. Recent studies of the biflagellate unicellular alga Chlamydomonas reinhardtii provided the first evidence that the interflagellar coupling responsible for synchronization is of hydrodynamic origin. To investigate this mechanism in detail, we study here synchronization in Chlamydomonas as its flagella slowly regrow after mechanically induced self-scission. The duration of synchronized intervals is found to be strongly dependent on flagellar length. Analysis within a stochastic model of coupled phase oscillators is used to extract the length dependence of the interflagellar coupling and the intrinsic beat frequencies of the two flagella. Physical and biological considerations that may explain these results are proposed.     

Equal Quasi-Partition of p-Groups

Let S be a subgroup of a group G. A set ${\Pi= \{H_1, \ldots , H_n\}}$ of subgroups ${H_i (i = 1, \ldots ,n)}$ with ${G=\cup_{H_i\in\Pi}H_i}$ is said to be an equal quasi-partition of G if ${H_i\cap H_j\cong S}$ and ${|H_i|=|H_j|}$ for all ${H_i, H_j\in\Pi}$ with ${i\ne j}$ . In this paper we investigate finite p-groups such that a subset of their maximal subgroups form an equal quasi-partition.