Demon Dynamics: Deterministic Chaos, the Szilard Map, and the Intelligence of Thermodynamic Systems

We introduce a deterministic chaotic system---the Szilard Map---that encapsulates the measurement, control, and erasure protocol by which Maxwellian Demons extract work from a heat reservoir. Implementing the Demon's control function in a dynamical embodiment, our construction symmetrizes Demon and thermodynamic system, allowing one to explore their functionality and recover the fundamental trade-off between the thermodynamic costs of dissipation due to measurement and due to erasure. The map's degree of chaos---captured by the Kolmogorov-Sinai entropy---is the rate of energy extraction from the heat bath. Moreover, an engine's statistical complexity quantifies the minimum necessary system memory for it to function. In this way, dynamical instability in the control protocol plays an essential and constructive role in intelligent thermodynamic systems.Comment: 5 pages, 3 figures, supplementary materials; http://csc.ucdavis.edu/~cmg/compmech/pubs/dds.ht

Memoryless Thermodynamics? A Reply

We reply to arXiv:1508.00203 `Comment on "Identifying Functional Thermodynamics in Autonomous Maxwellian Ratchets" (arXiv:1507.01537v2)'.Comment: 4 pages; http://csc.ucdavis.edu/~cmg/compmech/pubs/MerhavReply.ht

Correlation-powered Information Engines and the Thermodynamics of Self-Correction

Information engines can use structured environments as a resource to generate work by randomizing ordered inputs and leveraging the increased Shannon entropy to transfer energy from a thermal reservoir to a work reservoir. We give a broadly applicable expression for the work production of an information engine, generally modeled as a memoryful channel that communicates inputs to outputs as it interacts with an evolving environment. The expression establishes that an information engine must have more than one memory state in order to leverage input environment correlations. To emphasize this functioning, we designed an information engine powered solely by temporal correlations and not by statistical biases, as employed by previous engines. Key to this is the engine's ability to synchronize---the engine automatically returns to a desired dynamical phase when thrown into an unwanted, dissipative phase by corruptions in the input---that is, by unanticipated environmental fluctuations. This self-correcting mechanism is robust up to a critical level of corruption, beyond which the system fails to act as an engine. We give explicit analytical expressions for both work and critical corruption level and summarize engine performance via a thermodynamic-function phase diagram over engine control parameters. The results reveal a new thermodynamic mechanism based on nonergodicity that underlies error correction as it operates to support resilient engineered and biological systems.Comment: 22 pages, 13 figures; http://csc.ucdavis.edu/~cmg/compmech/pubs/tos.ht

Above and Beyond the Landauer Bound: Thermodynamics of Modularity

Information processing typically occurs via the composition of modular units, such as universal logic gates. The benefit of modular information processing, in contrast to globally integrated information processing, is that complex global computations are more easily and flexibly implemented via a series of simpler, localized information processing operations which only control and change local degrees of freedom. We show that, despite these benefits, there are unavoidable thermodynamic costs to modularity---costs that arise directly from the operation of localized processing and that go beyond Landauer's dissipation bound for erasing information. Integrated computations can achieve Landauer's bound, however, when they globally coordinate the control of all of an information reservoir's degrees of freedom. Unfortunately, global correlations among the information-bearing degrees of freedom are easily lost by modular implementations. This is costly since such correlations are a thermodynamic fuel. We quantify the minimum irretrievable dissipation of modular computations in terms of the difference between the change in global nonequilibrium free energy, which captures these global correlations, and the local (marginal) change in nonequilibrium free energy, which bounds modular work production. This modularity dissipation is proportional to the amount of additional work required to perform the computational task modularly. It has immediate consequences for physically embedded transducers, known as information ratchets. We show how to circumvent modularity dissipation by designing internal ratchet states that capture the global correlations and patterns in the ratchet's information reservoir. Designed in this way, information ratchets match the optimum thermodynamic efficiency of globally integrated computations.Comment: 17 pages, 9 figures; http://csc.ucdavis.edu/~cmg/compmech/pubs/idolip.ht

Quantifying the role of the seed population in radiation belt dynamics

The dynamics of the radiation belts depend on a delicate balance of source and loss processes. One such source process that has been shown to be effective is local acceleration, where 10s-100s keV seed electrons are accelerated via wave-particle interactions up to energies \u3e1 MeV. Historically, much of the focus of radiation belt research has been on the dynamics of these \u3e1 MeV electrons, and the role and importance of the seed electrons has been largely overlooked. In this thesis, we use phase space density calculated using data from the Van Allen Probes, to directly investigate seed population for a variety of events. We begin by presenting a case study of the 17 March 2013 event, providing some of the first clear observations of the seed population during a local acceleration event. Next, we present results from the first ever statistical study of the radiation belt seed population from the first 26 months of data from the Van Allen Probes. Finally, we examine all the pieces of the acceleration process together to determine what conditions produce effective radiation belt acceleration. Our results clearly demonstrate that the seed population plays a critical role in governing the dynamics of the higher energy radiation belt electrons

Microbial Nitrate Dependent Fe²⁺ Oxidation: A Potential Early Mars Metabolism

This thesis experimentally investigates the proposition that aqueous environments with anoxic, reducing, circumneutral conditions, inorganic electron donors and oxidants such as nitrate may have allowed chemolithotrophic microbial metabolisms, such as nitrate-dependent Fe2+ oxidation (NDFO), to thrive on early Mars. The NDFO microorganisms, Acidovorax sp. strain BoFeN1, Paracoccus sp. strain KS1 and Pseudogulbenkiania sp. strain 2002, are demonstrated to grow lithoautotrophically with a Mars-relevant olivine Fe2+ source and in martian simulant media developed from in situ and meteorite geochemical data. Additionally, mixotrophic NDFO with Fe2+ and an organic co-substrate as electron donors, was shown to increase the extent of microbial growth, which gains importance in light of the confirmation of complex organics at the martian surface. Biomineralised microbial features were discovered after culture with olivine and the oxidation of Fe2+ was measured in heterotrophic cultures. Microfossils and Fe3+ compounds in reducing contexts provide targets for biosignature detection missions. In addition, this work presents findings on the biochemical mechanisms of NDFO, quantifying the relative contributions of the Nar respiratory nitrate reductase enzyme, putative ferroxidases and nitrite accumulation to Fe2+ oxidation during nitrate reduction. Gene knockout experiments revealed that Fe2+ oxidation in the heterotrophic Salmonella enterica Serovar Typhimurium strain SL1344 is largely driven by the production of reactive nitrite ions during Nar activity. Draft genome analysis of Acidovorax sp. strain BoFeN1 and Paracoccus sp. strain KS1 revealed potential mechanisms of electron acquisition during Fe2+ oxidation, underlining that multiple mechanisms of NDFO exist. The combined findings of this thesis support the plausibility of NDFO in the deep martian past and propose mechanisms by which evidence may be preserved in the geological record of that planet

The Histological Structure and Physiological Response of the Sensory Units in the Knee-Joint of the Cat

1. Using a 'single-fibre' technique, afferent discharges from single sensory units in the capsule of the knee-joint of the decerebrate cat have been recorded from the posterior articular nerve to this joint. 2. The responses are of two types - 'rapidly-adapting' and 'slowly-adapting'. 3. The rapidly-adapting responses consist of impulses during movement of the joint but not while the joint is stationary. Such responses were found on only a few occasions and are similar to those from the C organs of Matthews (1933), and also to those attributed by Gray & Matthews (1951) to Pacinian corpuscles. 4. The slowly-adapting responses were more frequently encountered. They are characterized by maintained steady discharges while the joint is stationary, with 'exaggerated' changes in frequency during movement. The degree of exaggeration depends on the rate of movement, and the exaggerated response is followed by adaptation to a new, steady impulse-frequency. 5. The steady, adapted impulse-frequency in any one position is independent of the rate, but not always of the direction, of the movement used to reach that position. If the movement is one which produces a decrease in the frequency of the impulses, the final steady value may he less than that in the same position following a movement in the direction producing an increase in impulse-frequency. The degree of this 'directional' effect varies from unit to unit. 6. The sensory units giving rise to both types of response can he made to discharge by direct pressure on the part of the capsule in which they lie. By locating them in this way, the slowly-adapting units have been found to he most numerous in the centre of the hack of the joint-capsule, whereas the rapidly-adapting units tend to lie towards the sides of the joint. 7. Using the Gairns (1930) gold chloride technique, two types of sensory unit have been demonstrated histologically in the posterior part of the knee-joint capsule, a 'spray' type and a 'lamellated' type. 8. By obtaining a single-fibre discharge from the articular nerve and, while still recording the discharge, excising the particular area of capsule containing the sensory unit responsible for the discharge, it has been possible to correlate the structure of the sensory units with their physiological response. 9. The sensory units of spray type consist of a number of sprays supplied by a single axon, and are situated in the fibrous layer of the joint-capsule; they are undoubtedly the 'typical Ruffini endings' described by Gardner (1944). They are definitely responsible for the slowly-adapting discharges in the posterior articular nerve. It is suggested that these spray sensory units are capable of providing accurate information about the relative position of the bones forming the joint. 10. The lamellated sensory units, which also lie in the fibrous capsule, are much scarcer than the spray type. They consist of several receptors supplied by a single axon. These receptors are double the length of the spray receptors, but are very much smaller, and relatively more elongated, than Pacinian corpuscles. The lamellated type of sensory unit is almost certainly responsible for the rapidly-adapting discharges in the posterior articular nerve. 11. It is doubtful if other types of organised nerve-ending exist in the capsule, but some free nerve-endings are present. On one occasion tendon-organs were found in a cruciate ligament. 12. It is suggested that the larger fibres in the articular nerve innervate tendon-organs in the ligaments of the joint, and that the response of these is similar to the response of the spray sensory units in the capsule. The possibility is discussed that the capsular spray units, the sensory units of spray type (tendon-organs) in ligaments and tendons, and the flower-spray units in muscle-spindles form a series of sensory units, graded in size, which are all basically similar in structure and in function

Bridging the Gap with Deaf Paraprofessionals

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The Boundedness Locus and baby Mandelbrot sets for some generalized McMullen maps

In this paper we study rational functions of the form $R_{n,a,c}(z) = z^n + \dfrac{a}{z^n} + c,$ with $n$ fixed and at least $3$, and hold either $a$ or $c$ fixed while the other varies. We locate some homeomorphic copies of the Mandelbrot set in the $c$-parameter plane for certain ranges of $a$, as well as in the $a$-plane for some $c$-ranges. We use techniques first introduced by Douady and Hubbard, that were applied for the subfamily $R_{n,a,0}$ by Robert Devaney. These techniques involve polynomial-like maps of degree two.Comment: 36 pages, 22 figures; in this version made minor editorial changes and improved some figure

Enhanced Two-Photon Absorption in a Hollow-Core Photonic Bandgap Fiber

We show that two-photon absorption (TPA) in Rubidium atoms can be greatly enhanced by the use of a hollow-core photonic bandgap fiber. We investigate off-resonant, degenerate Doppler-free TPA on the 5S1/2 - 5D5/2 transition and observe 1% absorption of a pump beam with a total power of only 1 mW in the fiber. These results are verified by measuring the amount of emitted blue fluorescence and are consistent with the theoretical predictions which indicate that transit time effects play an important role in determining the two-photon absorption cross-section in a confined geometry.Comment: 5 pages, 6 figure