874 research outputs found
Temperature dependence of thermal conductivities of coupled rotator lattice and the momentum diffusion in standard map
In contrary to other 1D momentum-conserving lattices such as the
Fermi-Pasta-Ulam (FPU-) lattice, the 1D coupled rotator lattice
is a notable exception which conserves total momentum while exhibits normal
heat conduction behavior. The temperature behavior of the thermal
conductivities of 1D coupled rotator lattice had been studied in previous works
trying to reveal the underlying physical mechanism for normal heat conduction.
However, two different temperature behaviors of thermal conductivities have
been claimed for the same coupled rotator lattice. These different temperature
behaviors also intrigue the debate whether there is a phase transition of
thermal conductivities as the function of temperature. In this work, we will
revisit the temperature dependent thermal conductivities for the 1D coupled
rotator lattice. We find that the temperature dependence follows a power law
behavior which is different with the previously found temperature behaviors.
Our results also support the claim that there is no phase transition for 1D
coupled rotator lattice. We also give some discussion about the similarity of
diffusion behaviors between the 1D coupled rotator lattice and the single
kicked rotator also called the Chirikov standard map.Comment: 6 pages, 5 figure
Noisy saltatory spike propagation: The breakdown of signal transmission due to channel noise
Noisy saltatory spike propagation along myelinated axons is studied within a
stochastic Hodgkin-Huxley model. The intrinsic noise (whose strength is inverse
proportional to the nodal membrane size) arising from fluctuations of the
number of open ion channels influences the dynamics of the membrane potential
in a node of Ranvier where the sodium ion channels are predominantly localized.
The nodes of Ranvier are linearly coupled. As the measure for the signal
propagation reliability we focus on the ratio between the number of initiated
spikes and the transmitted spikes. This work supplements our earlier study [A.
Ochab-Marcinek, G. Schmid, I. Goychuk and P. H\"anggi, Phys. Rev E 79, 011904
(2009)] towards stronger channel noise intensity and supra-threshold coupling.
For strong supra-threshold coupling the transmission reliability decreases with
increasing channel noise level until the causal relationship is completely lost
and a breakdown of the spike propagation due to the intrinsic noise is
observed.Comment: To appear in EPJS
Thermal conductance of the coupled-rotator chain: Influence of temperature and size
Thermal conductance of a homogeneous 1D nonlinear lattice system with
neareast neighbor interactions has recently been computationally studied in
detail by Li et al [Eur. Phys. J. B {\bf 88}, 182 (2015)], where its power-law
dependence on temperature for high temperatures is shown. Here, we address
its entire temperature dependence, in addition to its dependence on the size
of the system. We obtain a neat data collapse for arbitrary temperatures
and system sizes, and numerically show that the thermal conductance curve is
quite satisfactorily described by a fat-tailed -Gaussian dependence on
with . Consequently, its asymptotic
behavior is given by with .Comment: 5 pages including 2 figure
Active Brownian motion in a narrow channel
We review recent advances in rectification control of artificial
microswimmers, also known as Janus particles, diffusing along narrow,
periodically corrugated channels. The swimmer self-propulsion mechanism is
modeled so as to incorporate a nonzero torque (propulsion chirality). We first
summarize the effects of chirality on the autonomous current of microswimmers
freely diffusing in channels of different geometries. In particular, left-right
and upside-down asymmetric channels are shown to exhibit different transport
properties. We then report new results on the dependence of the diffusivity of
chiral microswimmers on the channel geometry and their own self-propulsion
mechanism. The self-propulsion torque turns out to play a key role as a
transport control parameter.Comment: to be published in Eur. Phys. J Special Topic
Hydrodynamic and entropic effects on colloidal diffusion in corrugated channels
In the absence of advection, confined diffusion characterizes transport in
many natural and artificial devices, such as ionic channels, zeolites, and
nanopores. While extensive theoretical and numerical studies on this subject
have produced many important predictions, experimental verifications of the
predictions are rare. Here, we experimentally measure colloidal diffusion times
in microchannels with periodically varying width and contrast results with
predictions from the Fick-Jacobs theory and Brownian dynamics simulation. While
the theory and simulation correctly predict the entropic effect of the varying
channel width, they fail to account for hydrodynamic effects, which include
both an overall decrease and a spatial variation of diffusivity in channels.
Neglecting such hydrodynamic effects, the theory and simulation underestimate
the mean and standard deviation of first passage times by 40\% in channels with
a neck width twice the particle diameter. We further show that the validity of
the Fick-Jakobs theory can be restored by reformulating it in terms of the
experimentally measured diffusivity. Our work thus demonstrates that
hydrodynamic effects play a key role in diffusive transport through narrow
channels and should be included in theoretical and numerical models.Comment: 7 pages, 4 figure
A quorum sensing active matter in a confined geometry
Inspired by the problem of biofilm growth, we numerically investigate
clustering in a two-dimensional suspension of active (Janus) particles of
finite size confined in a circular cavity. Their dynamics is regulated by a
non-reciprocal mechanism that causes them to switch from active to passive
above a certain threshold of the perceived near-neighbor density (quorum
sensing).A variety of cluster phases -- glassy, solid (hexatic) and liquid --
is observed depending on the particle dynamics at the boundary, the quorum
sensing range, and the level of nois
Tetra-n-butylÂammonium tricyanido[N-(2-pyridylÂcarbonÂyl)pyridine-2-carboxÂimidato]ferrate(III) dihydrate
In the title compound, (C16H36N)[Fe(C12H8N3O2)(CN)3]·2H2O, the tetra-n-butylÂammonium ion has a tetraÂhedral configuration around the N atom, while the FeIII atom of the tricyanido[N-(2-pyridylÂcarbonÂyl)pyridine-2-carboximidato]iron(III) anion adopts a distorted octaÂhedral geometry. O—H⋯O and O—H⋯N hydrogen bonds link the components in the crystal structure
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