Browsing by Author "Tsekouras, Konstantinos"

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    Coupled simple exclusion process models
    (2009) Tsekouras, Konstantinos; Kolomeisky, Anatoly B.
    This study investigates problems in the overall context of intracellular particle transport using coupled simple exclusion processes to construct mathematical models of systems under consideration. Nonequilibrium statistical mechanics and cluster mean-field theory are used to analytically solve the model steady state and derive phase diagrams and quantities characteristic of transport such as average density and entrance/bulk/exit currents. All results are supported by extensive Monte-Carlo simulations. Four systems are investigated, namely: A system where kinesin motor proteins jump between microtubule tracks due to a single-point inhomogeneity; a system where transport of kinesins on a microtubule is interrupted by a diffusive compartment; a system where kinesin transport on a microtubule is coupled to the aqueous medium surrounding it; and finally a system where dyneins are transported on two protofilaments linked to each other at every site.
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    Dynamic evolution of spin-1 and spin-2 dipolar BECs
    (2007) Tsekouras, Konstantinos; Pu, Han
    This study investigates the dynamical evolution of spin-1 and spin-2 Bose-Einstein Condensates (BECs) when the dipolar interaction is taken into consideration. Using the Single-Mode Approximation (SMA) equations of motion are derived for each condensate component which are then numerically solved. The results convincingly show that the dipolar interaction has a significant effect despite being much weaker than the collision or spin-exchange interaction and that if included magnetic effects are easy to treat. Further, an analytical Mean-Field Theory formulation is used to derive and simplify equations of motion for a spin-1 BEC in 2D (pancake) configuration. Moving to a reference frame that rotates at the Larmor frequency greatly simplifies the equations and removes first-order Zeeman terms, rendering the effects of the dipolar interaction much clearer to observe in the condensate evolution.