53 research outputs found
A deformable microswimmer in a swirl: capturing and scattering dynamics
Inspired by the classical Kepler and Rutherford problem, we investigate an
analogous set-up in the context of active microswimmers: the behavior of a
deformable microswimmer in a swirl flow. First we identify new steady bound
states in the swirl flow and analyze their stability. Second we study the
dynamics of a self-propelled swimmer heading towards the vortex center, and we
observe the subsequent capturing and scattering dynamics. We distinguish
between two major types of swimmers, those that tend to elongate
perpendicularly to the propulsion direction and those that pursue a parallel
elongation. While the first ones can get caught by the swirl, the second ones
were always observed to be scattered, which proposes a promising escape
strategy. This offers a route to design artificial microswimmers that show the
desired behavior in complicated flow fields. It should be straightforward to
verify our results in a corresponding quasi-two-dimensional experiment using
self-propelled droplets on water surfaces.Comment: 13 pages, 8 figure
Individual and collective dynamics of self-propelled soft particles
Deformable self-propelled particles provide us with one of the most important
nonlinear dissipative systems, which are related, for example, to the motion of
microorganisms. It is emphasized that this is a subject of localized objects in
non-equilibrium open systems. We introduce a coupled set of ordinary
differential equations to study various dynamics of individual soft particles
due to the nonlinear couplings between migration, spinning and deformation. By
introducing interactions among the particles, the collective dynamics and its
collapse are also investigated by changing the particle density and the
interaction strength. We stress that assemblies of self-propelled particles
also exhibit a variety of non-equilibrium localized patterns
Non-Spinning Black Holes in Alternative Theories of Gravity
We study two large classes of alternative theories, modifying the action
through algebraic, quadratic curvature invariants coupled to scalar fields. We
find one class that admits solutions that solve the vacuum Einstein equations
and another that does not. In the latter, we find a deformation to the
Schwarzschild metric that solves the modified field equations in the small
coupling approximation. We calculate the event horizon shift, the innermost
stable circular orbit shift, and corrections to gravitational waves, mapping
them to the parametrized post-Einsteinian framework.Comment: 7 pages, submitted to PR
Dynamics of a deformable self-propelled particle under external forcing
We investigate dynamics of a self-propelled deformable particle under
external field in two dimensions based on the model equations for the center of
mass and a tensor variable characterizing deformations. We consider two kinds
of external force. One is a gravitational-like force which enters additively in
the time-evolution equation for the center of mass. The other is an
electric-like force supposing that a dipole moment is induced in the particle.
This force is added to the equation for the deformation tensor. It is shown
that a rich variety of dynamics appears by changing the strength of the forces
and the migration velocity of self-propelled particle
Viral Vector Malaria Vaccines Induce High-Level T Cell and Antibody Responses in West African Children and Infants.
Heterologous prime-boosting with viral vectors encoding the pre-erythrocytic antigen thrombospondin-related adhesion protein fused to a multiple epitope string (ME-TRAP) induces CD8+ T cell-mediated immunity to malaria sporozoite challenge in European malaria-naive and Kenyan semi-immune adults. This approach has yet to be evaluated in children and infants. We assessed this vaccine strategy among 138 Gambian and Burkinabe children in four cohorts: 2- to 6-year olds in The Gambia, 5- to 17-month-olds in Burkina Faso, and 5- to 12-month-olds and 10-week-olds in The Gambia. We assessed induction of cellular immunity, taking into account the distinctive hematological status of young infants, and characterized the antibody response to vaccination. T cell responses peaked 7 days after boosting with modified vaccinia virus Ankara (MVA), with highest responses in infants aged 10 weeks at priming. Incorporating lymphocyte count into the calculation of T cell responses facilitated a more physiologically relevant comparison of cellular immunity across different age groups. Both CD8+ and CD4+ T cells secreted cytokines. Induced antibodies were up to 20-fold higher in all groups compared with Gambian and United Kingdom (UK) adults, with comparable or higher avidity. This immunization regimen elicited strong immune responses, particularly in young infants, supporting future evaluation of efficacy in this key target age group for a malaria vaccine
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