Browsing by Author "Argun, A."
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Item Open Access Better stability with measurement errors(Springer New York LLC, 2016-06) Argun, A.; Volpe, G.Often it is desirable to stabilize a system around an optimal state. This can be effectively accomplished using feedback control, where the system deviation from the desired state is measured in order to determine the magnitude of the restoring force to be applied. Contrary to conventional wisdom, i.e. that a more precise measurement is expected to improve the system stability, here we demonstrate that a certain degree of measurement error can improve the system stability. We exemplify the implications of this finding with numerical examples drawn from various fields, such as the operation of a temperature controller, the confinement of a microscopic particle, the localization of a target by a microswimmer, and the control of a population.Item Open Access Brownian gyrator: an experimental realization(OSA, 2017) Soni, Jalpa; Argun, A.; Dabelow, L.; Bo, S.; Eichhorn, R.; Pesce, G.; Volpe, GiovanniWe present an experimental realization of a minimal heat engine in the form of a single Brownian particle, performing gyrating motion by systematic torque generation due to dissipation from two different heat baths in a simple optical tweezer set-up.Item Open Access Non-Boltzmann stationary distributions and non-equilibrium relations in active baths(Optical Society of America, 2017) Argun, A.; Moradi, A. R.; Pinçe, E.; Bağcı, Gökhan Barış; Imparato, A.; Volpe, GiovanniThe presence of active noise generated by motile bacteria results in the violation of Boltzmann distribution. Therefore, non-equilibrium relations become invalid active baths. Yet these relations can be recovered by introducing effective potentials.Item Open Access Non-Boltzmann stationary distributions and nonequilibrium relations in active baths(American Physical Society, 2016-12) Argun, A.; Moradi A.-R.; Pinçe, E.; Bagci, G. B.; Imparato, A.; Volpe, G.Most natural and engineered processes, such as biomolecular reactions, protein folding, and population dynamics, occur far from equilibrium and therefore cannot be treated within the framework of classical equilibrium thermodynamics. Here we experimentally study how some fundamental thermodynamic quantities and relations are affected by the presence of the nonequilibrium fluctuations associated with an active bath. We show in particular that, as the confinement of the particle increases, the stationary probability distribution of a Brownian particle confined within a harmonic potential becomes non-Boltzmann, featuring a transition from a Gaussian distribution to a heavy-tailed distribution. Because of this, nonequilibrium relations (e.g., the Jarzynski equality and Crooks fluctuation theorem) cannot be applied. We show that these relations can be restored by using the effective potential associated with the stationary probability distribution. We corroborate our experimental findings with theoretical arguments.Item Open Access XPS and water contact angle measurements on aged and corona-treated PP(John Wiley & Sons, Inc., 1999) Süzer, S.; Argun, A.; Vatansever, O.; Aral, O.Effects of corona treatment and aging on commercially produced corona discharged polypropylene (PP) films were followed via surface sensitive roughness analysis by atomic force microscopy (AFM), water contact angle (WCA), and X-ray photoelectron spectroscopic (XPS) measurements. Roughness analysis by AFM gave similar results for both untreated and corona-treated samples. The measured water contact angle decreased after corona treatment but increased with aging. XPS findings revealed that corona treatment caused an increase in the O-containing species on the surface of the films, but the measured O/C atomic ratio decreased with aging. The angle dependence of the observed XPS O/C atomic ratio further revealed that surface modifications by the corona treatment were buried into the polymer away from the surface as a function of aging. This is attributed to a surface rearrangement of the macromolecules in agreement with the findings of Garbassi et al. on oxygen-plasma-treated polypropylene.