21 research outputs found
An Overview of Emergent Order in Far-from-equilibrium Driven Systems: From Kuramoto Oscillators to Rayleigh-B\'enard Convection
Soft-matter systems when driven out-of-equilibrium often give rise to
structures that usually lie in-between the macroscopic scale of the material
and microscopic scale of its constituents. In this paper we review three such
systems, the two-dimensional square-lattice Ising model, the Kuramoto model and
the Rayleigh-B\'enard convection system which when driven out-of-equilibrium
give rise to emergent spatio-temporal order through self-organization. A common
feature of these systems is that the entities that self-organize are coupled to
one another in some way, either through local interactions or through a
continuous media. Therefore, the general nature of non-equilibrium fluctuations
of the intrinsic variables in these systems are found to follow similar trends
as order emerges. Through this paper, we attempt to find connections between
these systems, and systems in general which give rise to emergent order when
driven out-of-equilibrium.Comment: Submitted to Entrop
Dielectric Hysteresis, Relaxation Dynamics, and Non-volatile Memory Effect in Carbon Nanotube Dispersed Liquid Crystal
The self-organizing properties of nematic liquid crystals (LC) can be used to
template carbon nanotubes (CNTs) on a macroscopic dimension. The nematic
director field, coupled to the dispersed CNT long-axis, enables controlled
director reorientation using well-established methods of LC alignment
techniques, such as patterned-electrode-surface, electric fields, and magnetic
fields. Electric field induced director rotation of a nematic LC+CNT system is
of potential interests due to its possible applications as a nano
electromechanical system. The relaxation mechanism for a LC+CNT composite, on
the removal of the applied field, reveals the intrinsic dynamics of this
anisotropic system. Dielectric hysteresis and temperature dependence of the
dielectric constant coherently shows the ferroelectric-type behavior of the
LC+CNT system in the nematic phase. The strong surface anchoring of LC
molecules on CNT walls results in forming local isolated pseudo-nematic domains
in the isotropic phase. These domains, being anisotropic, respond to external
fields, but, do not relax back to the original state on switching of the field
off, showing non-volatile memory effect.Comment: 7 pages, 8 figure
Exponential Self-Organization and Moore\u27s Law: Measures and Mechanisms
The question of how complex systems become more organized and efficient with time is open. Examples are the formation of elementary particles from pure energy, the formation of atoms from particles, the formation of stars and galaxies, and the formation of molecules from atoms, of organisms, and of the society. In this sequence, order appears inside complex systems and randomness (entropy) is expelled to their surroundings. Key features of self-organizing systems are that they are open and they are far away from equilibrium, with increasing energy flows through them. This work searches for global measures of such self-organizing systems, which are predictable and do not depend on the substrate of the system studied. Our results will help to understand the existence of complex systems and mechanisms of self-organization. In part we also provide insights, in this work, about the underlying physical essence of Moore’s law and the multiple logistic growth observed in technological progress
Calorimetric study of the nematic to smectic-A phase transition in octylcyanobiphenyl-hexane binary mixtures
The continuous nematic to smectic-A (N-SmA) phase transition has been studied
by high-resolution ac-calorimetry in binary mixtures of the liquid crystal
octylcyanobiphenyl(8CB) and a non-mesogenic, low-molecular weight, solvent
n-hexane(hex) as a function of temperature and solvent concentration. Heating
and cooling scans about the N-SmA transition temperature were repeatedly
performed on pure and six 8CB+hex samples having hexane molar concentration
ranging from x_{hex}= 0.02 to 0.12. All 8CB+hex samples in this range of
x_{hex} remain macroscopically miscible and exhibit an N-SmA heat capacity peak
that shifts non-monotonically to lower temperature and evolves in shape, with a
reproducible hysteresis, as x_{hex} increases. The imaginary part of heat
capacity remains zero up to x^{TCP}_{hex}\simeq 0.07$ above which the distinct
peak is observed, corresponding to a jump in both the real and imaginary
enthalpy. A simple power-law analysis reveals an effective exponent that
increases smoothly from 0.30 to 0.50 with an amplitude ratio
A^{-}/A^{+}\rightarrow 1 as x_{hex}\rightarrow x^{TCP}_{hex}. This observed
crossover towards the N-SmA tricritical point driven by solvent concentration
is consistent with previous results and can be understood as weakening of the
liquid crystal intermolecular potential promoting increased nematic
fluctuations
Studies of Nanocomposites of Carbon Nanotubes and a Negative Dielectric Anisotropy Liquid Crystal
The complex specific heat is reported over a wide temperature range for a negative dielectric anisotropy alkoxyphenylbenzoate liquid crystal (9OO4) and carbon nanotube (CNT) composites as a function of carbon nanotube concentration. It has been observed that the combination of nanotubes (CNT) and liquid crystal (LC) provides a very useful way to align CNTs and also dramatically increases the order in the liquid crystal performance, which is useful in liquid display technology (LCD). The calorimetric scans were performed between 25 and 95°C temperatures, first allowed cooling and then heating for CNT concentration ranging from ϕw = 0 to 0.2 wt%. All 9OO4/CNT composite mesophases have transition temperatures about 1 K higher and a crystallization temperature 4 K higher as compared to the pure 9OO4 liquid crystal. A strongly first-order specific heat feature is observed, which is 0.5 K higher than in the pure 9OO4. The transition enthalpy for the composite mesophases is observed 10% lower than the pure liquid crystal. We interpret that these results arising from the LC-CNT surface interaction lead to pinning orientational order uniformly along the CNT, without pinning the position of the 9OO4 molecule. These effects of incorporating CNTs with LC are likely due to elastic coupling between CNT and LC. These effects of incorporating CNTs into LCs are likely due to an "anisotropic orientational" coupling between CNT and LC, the change in the elastic properties of composites and thermal anisotropic properties of the CNTs