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Showing papers by "John Bechhoefer published in 2021"


Journal ArticleDOI
TL;DR: In this article, the authors used optical replication mapping (ORM) to map early-initiation events in human cells and found that the distribution of human replication initiation is consistent with inefficient, stochastic activation of heterogeneously distributed potential initiation complexes enriched in accessible chromatin.

46 citations


Journal ArticleDOI
TL;DR: This work designed an engine that stores energy by raising a bead against gravity, driven purely by information about the bead position, and finds that the rate of work storage and velocity of directed motion are limited only by the physical parameters of the engine.
Abstract: Information-driven engines that rectify thermal fluctuations are a modern realization of the Maxwell-demon thought experiment. We introduce a simple design based on a heavy colloidal particle, held by an optical trap and immersed in water. Using a carefully designed feedback loop, our experimental realization of an "information ratchet" takes advantage of favorable "up" fluctuations to lift a weight against gravity, storing potential energy without doing external work. By optimizing the ratchet design for performance via a simple theory, we find that the rate of work storage and velocity of directed motion are limited only by the physical parameters of the engine: the size of the particle, stiffness of the ratchet spring, friction produced by the motion, and temperature of the surrounding medium. Notably, because performance saturates with increasing frequency of observations, the measurement process is not a limiting factor. The extracted power and velocity are at least an order of magnitude higher than in previously reported engines.

33 citations


Journal ArticleDOI
01 Aug 2021
TL;DR: In this paper, Bechhoefer et al. discuss recent experiments that show how this "Mpemba effect" can be reliably reproduced and quantitatively understood and demonstrate that hot water quenched in a cold container can sometimes begin to freeze sooner than warm water under similar initial conditions.
Abstract: Anecdotal but elusive reports suggest that hot water quenched in a cold container can sometimes begin to freeze sooner than warm water under similar initial conditions. John Bechhoefer and colleagues discuss recent experiments that show how this ‘Mpemba effect’ can be reliably reproduced and quantitatively understood.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show that the Mpemba effect arises from a non-monotonic temperature dependence of the maximum amount of work that can be extracted from the local-equilibrium state at the end of Stage 1.
Abstract: The Mpemba effect refers to systems whose thermal relaxation time is a non-monotonic function of the initial temperature. Thus, a system that is initially hot cools to a bath temperature more quickly than the same system, initially warm. In the special case where the system dynamics can be described by a double-well potential with metastable and stable states, dynamics occurs in two stages: a fast relaxation to local equilibrium followed by a slow equilibration of populations in each coarse-grained state. We have recently observed the Mpemba effect experimentally in such a setting, for a colloidal particle immersed in water. Here, we show that this metastable Mpemba effect arises from a non-monotonic temperature dependence of the maximum amount of work that can be extracted from the local-equilibrium state at the end of Stage 1.

15 citations


Book
28 Feb 2021
TL;DR: Control theory, an interdisciplinary concept dealing with the behaviour of dynamical systems, is an important but often overlooked aspect of physics as discussed by the authors, which is the first broad and complete treatment of the topic tailored for physicists, one which goes from the basics right through to the most recent advances.
Abstract: Control theory, an interdisciplinary concept dealing with the behaviour of dynamical systems, is an important but often overlooked aspect of physics. This is the first broad and complete treatment of the topic tailored for physicists, one which goes from the basics right through to the most recent advances. Simple examples develop a deep understanding and intuition for the systematic principles of control theory, beyond the recipes given in standard engineering-focused texts. Up-to-date coverage of control of networks and complex systems, and a thorough discussion of the fundamental limits of control, including the limitations placed by causality, information theory, and thermodynamics are included. In addition it explores important recent advances in stochastic thermodynamics on the thermodynamic costs of information processing and control. For all students of physics interested in control theory, this classroom-tested, comprehensive approach to the topic with online solutions and further materials delivers both fundamental principles and current developments.

13 citations


Posted ContentDOI
TL;DR: In this paper, the limits of information-to-energy conversion when an information engine's benefit is limited to output energy that can be stored were explored. And they showed that restricting the engine's output in this way can limit its ability to convert information to energy.
Abstract: Understanding the connections between information and thermodynamics has been among the most visible applications of stochastic thermodynamics. While recent theoretical advances have established that the second law of thermodynamics sets limits on information-to-energy conversion, it is currently unclear to what extent real systems can achieve the predicted theoretical limits. Using a simple model of an information engine that has recently been experimentally implemented, we explore the limits of information-to-energy conversion when an information engine's benefit is limited to output energy that can be stored. We find that restricting the engine's output in this way can limit its ability to convert information to energy. Nevertheless, a feedback control that inputs work can allow the engine to store energy at the highest achievable rate. These results sharpen our theoretical understanding of the limits of real systems that convert information to energy.

5 citations


Journal ArticleDOI
01 Feb 2021-EPL
TL;DR: It is shown that although a single unit bit is easier to erase in the slow-driving limit, the majority-logic bit in general outperforms the single unitbit in the fast-erasure limit.
Abstract: We study finite-time bit erasure in the context of majority-logic decoding. In particular, we calculate the minimum amount of work needed to erase a majority-logic bit when one has full control over the system dynamics. We show that although a single unit bit is easier to erase in the slow-driving limit, the majority-logic bit in general outperforms the single unit bit in the fast-erasure limit. Our results also suggest optimal design principles for majority-logic bits under limited control.

2 citations


Posted Content
TL;DR: In this article, anomalous heating in a colloidal system, where an initially cold system heats up faster than an identical warm system coupled to the same thermal bath, was observed.
Abstract: We report anomalous heating in a colloidal system, the first observation of the inverse Mpemba effect, where an initially cold system heats up faster than an identical warm system coupled to the same thermal bath. For an overdamped, Brownian colloidal particle moving in a tilted double-well potential, we find a non-monotonic dependence of the heating times on the initial temperature of the system, as predicted by an eigenfunction expansion of the associated Fokker-Planck equation. By carefully tuning parameters, we also observe a "strong" version of anomalous heating, where a cold system heats up exponentially faster than systems prepared under slightly different conditions

2 citations


Proceedings ArticleDOI
TL;DR: In this paper, an information engine that can transport a bead in a desired direction by using favorable fluctuations from the thermal bath is presented. But, in its original formulation, the information engine generates a fluctuating velocity and cannot control the position of the bead.
Abstract: We have built an information engine that can transport a bead in a desired direction by using favorable fluctuations from the thermal bath. However, in its original formulation, the information engine generates a fluctuating velocity and cannot control the position of the bead. Here, we introduce a feedback algorithm that can control the bead's position, to follow a desired trajectory. The bead can track the path if the maximum desired velocity is below the engine's maximum average velocity. Measuring the range of frequency that the feedback algorithm can track, we find a bandwidth that is slightly lower than the corner frequency of the bead in the trap.

1 citations