7 research outputs found
Structural transition in the collective behavior of cognitive agents
Living organisms process information to interact and adapt to their surroundings with the goal of finding food, mating, or averting hazards. The structure of their environment has profound repercussions through both selecting their internal architecture and also inducing adaptive responses to environmental cues and stimuli. Adaptive collective behavior underpinned by specialized optimization strategies is ubiquitous in the natural world. We develop a minimal model of agents that explore their environment by means of sampling trajectories. The spatial information stored in the sampling trajectories is our minimal definition of a cognitive map. We find that, as cognitive agents build and update their internal, cognitive representation of the causal structure of their environment, complex patterns emerge in the system, where the onset of pattern formation relates to the spatial overlap of cognitive maps. Exchange of information among the agents leads to an order-disorder transition. As a result of the spontaneous breaking of translational symmetry, a Goldstone mode emerges, which points at a collective mechanism of information transfer among cognitive organisms. These findings may be generally applicable to the design of decentralized, artificial-intelligence swarm systems
Myelin Structures Formed by Thermotropic Smectic Liquid Crystals
We report on transient
structures, formed by thermotropic smectic-A
liquid crystals, resembling the myelin figures of lyotropic lamellar
liquid crystals. The thermotropic myelin structures form during the
solubilization of a smectic-A droplet in an aqueous phase containing
a cationic surfactant at concentrations above the critical micelle
concentration. Similar to the lyotropic myelin figures, the thermotropic
myelins appear in an optical microscope as flexible tubelike structures
growing at the smectic/aqueous interface. Polarizing microscopy and
confocal fluorescence microscopy show that the smectic layers are
parallel to the tube surface and form a cylindrically bent arrangement
around a central line defect in the tube. We study the growth behavior
of this new type of myelins and discuss similarities to and differences
from the classical lyotropic myelin figures
Solubilization of Thermotropic Liquid Crystal Compounds in Aqueous Surfactant Solutions
We study the micellar solubilization of three thermotropic
liquid
crystal compounds by immersing single drops in aqueous solutions of
the ionic surfactant tetradecyltrimethylammonium bromide. For both
nematic and isotropic drops, we observe a linear decrease of the drop
size with time as well as convective flows and self-propelled motions.
The solubilization is accompanied by the appearance of small aqueous
droplets within the nematic or isotropic drop. At low temperatures,
nematic drops expell small nematic droplets into the aqueous environment.
Smectic drops show the spontaneous formation of filament-like structures
which resemble the myelin figures observed in lyotropic lamellar systems.
In all cases, the liquid crystal drops become completely solubilized,
provided the weight fraction of the liquid crystal in the system is
not larger than a few percent. The solubilization of the liquid crystal
drops is compared with earlier studies of the solubilization of alkanes
in ionic surfactant solutions
Solubilization of Thermotropic Liquid Crystal Compounds in Aqueous Surfactant Solutions
We study the micellar solubilization of three thermotropic
liquid
crystal compounds by immersing single drops in aqueous solutions of
the ionic surfactant tetradecyltrimethylammonium bromide. For both
nematic and isotropic drops, we observe a linear decrease of the drop
size with time as well as convective flows and self-propelled motions.
The solubilization is accompanied by the appearance of small aqueous
droplets within the nematic or isotropic drop. At low temperatures,
nematic drops expell small nematic droplets into the aqueous environment.
Smectic drops show the spontaneous formation of filament-like structures
which resemble the myelin figures observed in lyotropic lamellar systems.
In all cases, the liquid crystal drops become completely solubilized,
provided the weight fraction of the liquid crystal in the system is
not larger than a few percent. The solubilization of the liquid crystal
drops is compared with earlier studies of the solubilization of alkanes
in ionic surfactant solutions
Electrowetting Actuated Microfluidic Transport in Surface Grooves with Triangular Cross Section
Liquids show different static wetting
morphologies in open triangular
grooves depending upon the wedge angle (ψ) of the groove and
the liquid contact angle (θ) with the substrate. Switching between
different morphologies can be achieved either by varying the contact
angle of the liquid or by changing the wedge angle of the groove.
In the present work we manipulate the apparent contact angle of a
liquid by electrowetting to switch between liquid morphologies, from
droplet to filament, to achieve microfluidic transport of the liquid
into open triangular grooves. The static length of liquid filaments
in grooves is analyzed as a function of applied voltage for different
applied ac frequencies. The dynamic advancement of the filament lengths
in grooves is analyzed as a function of time for different applied
voltages for two different liquids: first with contact angle greater
than the wedge angle and second with contact angle smaller than the
wedge angle. Later an exact electrical model is derived to explain
the liquid transport in triangular grooves actuated by electrowetting
which includes the precise geometry of the liquid morphology
Direct Visualization of Spatiotemporal Structure of Self-Assembled Colloidal Particles in Electrohydrodynamic Flow of a Nematic Liquid Crystal
Characterization of spatiotemporal
dynamics is of vital importance
to soft matter systems far from equilibrium. Using a confocal laser
scanning microscopy, we directly reveal three-dimensional motion of
surface-modified particles in the electrohydrodynamic convection of
a nematic liquid crystal. Particularly, visualizing a caterpillar-like
motion of a self-assembled colloidal chain demonstrates the mechanism
of the persistent transport enabled by the elastic, electric, and
hydrodynamic contributions. We also precisely show how the particles’
trajectory is spatially modified by simply changing the surface boundary
condition
Direct Visualization of Spatiotemporal Structure of Self-Assembled Colloidal Particles in Electrohydrodynamic Flow of a Nematic Liquid Crystal
Characterization of spatiotemporal
dynamics is of vital importance
to soft matter systems far from equilibrium. Using a confocal laser
scanning microscopy, we directly reveal three-dimensional motion of
surface-modified particles in the electrohydrodynamic convection of
a nematic liquid crystal. Particularly, visualizing a caterpillar-like
motion of a self-assembled colloidal chain demonstrates the mechanism
of the persistent transport enabled by the elastic, electric, and
hydrodynamic contributions. We also precisely show how the particles’
trajectory is spatially modified by simply changing the surface boundary
condition