14,547 research outputs found
Brownian molecular motors driven by rotation-translation coupling
We investigated three models of Brownian motors which convert rotational
diffusion into directed translational motion by switching on and off a
potential. In the first model a spatially asymmetric potential generates
directed translational motion by rectifying rotational diffusion. It behaves
much like a conventional flashing ratchet. The second model utilizes both
rotational diffusion and drift to generate translational motion without spatial
asymmetry in the potential. This second model can be driven by a combination of
a Brownian motor mechanism (diffusion driven) or by powerstroke (drift driven)
depending on the chosen parameters. In the third model, elements of both the
Brownian motor and powerstroke mechanisms are combined by switching between
three distinct states. Relevance of the model to biological motor proteins is
discussed.Comment: 11 pages, 8 figure
Grammar of Location and Motion in Zande
In Zande expressions of position and motion are arranged on a gamut in correlation with increasing syntactic complexity. Topological relations, expressed by basic locative construction are at the left end, directed motion at the right end. Directed translational motion is marked by the preposition ku, which also marks angular location. Topological relations, in situ motion and undirected translational motion do not get a specific marking. This indicates the interrelatedness of stasis and motion on the one hand and undirected and directed motion on the other hand
Nonintegrable Schrodinger Discrete Breathers
In an extensive numerical investigation of nonintegrable translational motion
of discrete breathers in nonlinear Schrodinger lattices, we have used a
regularized Newton algorithm to continue these solutions from the limit of the
integrable Ablowitz-Ladik lattice. These solutions are shown to be a
superposition of a localized moving core and an excited extended state
(background) to which the localized moving pulse is spatially asymptotic. The
background is a linear combination of small amplitude nonlinear resonant plane
waves and it plays an essential role in the energy balance governing the
translational motion of the localized core. Perturbative collective variable
theory predictions are critically analyzed in the light of the numerical
results.Comment: 42 pages, 28 figures. to be published in CHAOS (December 2004
Current-driven vortex oscillations in metallic nanocontacts
We present experimental evidence of sub-GHz spin-transfer oscillations in
metallic nano-contacts that are due to the translational motion of a magnetic
vortex. The vortex is shown to execute large-amplitude orbital motion outside
the contact region. Good agreement with analytical theory and micromagnetics
simulations is found.Comment: 4 pages, 3 figure
Noise-Induced Transition from Translational to Rotational Motion of Swarms
We consider a model of active Brownian agents interacting via a harmonic
attractive potential in a two-dimensional system in the presence of noise. By
numerical simulations, we show that this model possesses a noise-induced
transition characterized by the breakdown of translational motion and the onset
of swarm rotation as the noise intensity is increased. Statistical properties
of swarm dynamics in the weak noise limit are further analytically
investigated.Comment: 7 pages, 7 figure
Rational design and dynamics of self-propelled colloidal bead chains: from rotators to flagella
The quest for designing new self-propelled colloids is fuelled by the demand
for simple experimental models to study the collective behaviour of their more
complex natural counterparts. Most synthetic self-propelled particles move by
converting the input energy into translational motion. In this work we address
the question if simple self-propelled spheres can assemble into more complex
structures that exhibit rotational motion, possibly coupled with translational
motion as in flagella. We exploit a combination of induced dipolar interactions
and a bonding step to create permanent linear bead chains, composed of
self-propelled Janus spheres, with a well-controlled internal structure. Next,
we study how flexibility between individual swimmers in a chain can affect its
swimming behaviour. Permanent rigid chains showed only active rotational or
spinning motion, whereas longer semi-flexible chains showed both translational
and rotational motion resembling flagella like-motion, in the presence of the
fuel. Moreover, we are able to reproduce our experimental results using
numerical calculations with a minimal model, which includes full hydrodynamic
interactions with the fluid. Our method is general and opens a new way to
design novel self-propelled colloids with complex swimming behaviours, using
different complex starting building blocks in combination with the flexibility
between them.Comment: 27 pages, 10 figure
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