arXiv subjects

S. Siva Nasarayya Chari

Publications and source records attributed to S. Siva Nasarayya Chari.

4 recordsLinked to original sources

arXiv2026

Phase separating microdomains in highly coarse-grained lipids

A highly coarse-grained model for the lipid monolayer is formulated by considering a two-dimensional system of spherical particles with distinct types of S, U, and C, corresponding to the saturated, unsaturated, and cholesterol molecules. Their interactions are defined as modified Lennard-Jones type with distinct interaction strengths. The phase behavior of the system is studied for various cholesterol compositions, $x$ ranging from 0.1 to 0.6. From the simulation results, we observe that the S- and C-type particles segregate together to form ordered microdomains, with U-type particles at their outer leaflet; consistent with observations in literature. An order parameter $Φ$ is defined to quantify the extent of phase separation among the constituents. The time averaged value of $Φ$ is found increasing with the $x$ value. Radial distribution function calculations indicate the structural ordering within the phase separated domains.

cond-mat.soft↗

arXiv2025

Sterol-induced raft-like domains in a model lipid monolayer

A two-dimensional system consisting a mixture of highly coarse-grained saturated (S-type), unsaturated (U-type) lipid molecules, and cholesterol (C-type) molecules is considered to form a model lipid monolayer. All the S-, U- and C-type particles are spherical in shape, with distinct interaction strengths. The phase behavior of the system is studied for various compositions ($x$) of the C-type particles, ranging from $x = 0.1$ to $0.9$. The results show that a structurally ordered complex is formed with the S- and C-types in the fluid-like environment of U-type particles, for $x \in \lbrace 0.5 - 0.6\rbrace$. The time-averaged hexatic order parameter $\left\langle Ψ_{6} \right\rangle$ indicates that the dynamical segregation of S- and C-types exhibits a positional order, that is found to be maximum for $x$ in the range of 0.5 - 0.6. The mean change in the free energy ($ΔG(x)$) obtained from the mean change in enthalpy ($ΔH$) and entropy ($ΔS$) calculations suggests that $ΔG$ is minimum for $x \sim 0.6$. A phenomenological expression for the Gibbs free energy is formulated by explicitly accounting for the individual free energies of S-,U- and C-type particles and the mutual interactions between them. Minimizing this phenomenological $G$ with respect to the C-type composition results in the optimal value, $x^* = 0.564 \pm 0.001$ for stable coexistence of phases; consistent with the simulation results and also the previous experimental observations \cite{raghavendra_effect_2023}. All these observations signify the optimal C-type composition, $x \sim 0.5 - 0.6$.

cond-mat.soft↗

arXiv2025

Nonequilibrium Work Fluctuations in Force-induced Melting of a Short B-DNA

A system of a solvated canonical B-DNA of 12 base pairs with the specified sequence is initially equilibrated in a state of zero external force $f$ acting on it. After equilibration, a switching experiment is performed over the system by pulling one end of the DNA while restraining its other end. The finite time pulling process is performed at a constant rate of the applied force until a maximum value of 400 pN. The associated nonequilibrium work done $(W)$ during this process is determined by numerically integrating the force-extension curve as a function of the applied force. An ensemble of the work values, $P(W)$, is obtained by repeating the pulling experiment a large number of times. We determine the free energy difference $(ΔF)$ between the equilibrium and force-induced melted states of the DNA by employing the Jarzynski equality. The value of $ΔF$ is found to be in close agreement with the conventional equilibrium methods.

cond-mat.soft↗

arXiv2016

A new truncation scheme for BBGKY hierarchy: conservation of energy and time reversibility

We propose a new truncation scheme for Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. We approximate the three particle distribution function $f_{3}(1,2,3,t)$ in terms of $f_{2}(1,2,t)$, $f_{1}(3,t)$ and two point correlation functions $\left\lbrace g_{2}(1,3,t), g_{2}(2,3,t)\right\rbrace $. Further $f_{2}$ is expressed in terms of $f_{1}(1,t)$ and $g_{2}(1,2,t)$ to close the hierarchy, resulting a set of coupled kinetic equations for $f_{1}$ and $g_{2}$. In this paper we show that, for velocity independent correlations, the kinetic equation for $f_{1}$ reduces to the model proposed by Martys[Martys N S 1999 \textit{IJMPC} \textbf{10} 1367-1382]. In the steady state limit, the kinetic equation for $g_{2}$ reduces to Born-Green-Yvon (BGY) hierarchy for homogeneous density. We also prove that the present scheme respects the energy conservation and under specific circumstances, time symmetry \textit{i.e.,} $\displaystyle \frac{dH(t)}{dt} = 0$ where $H(t)$ refers to the Boltzmann's H-function.

cond-mat.stat-mech↗