4,453 research outputs found

    Four Paradoxes Involving the Second Law of Thermodynamics

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    Recently four independent paradoxes have been proposed which appear to challenge the second law of thermodynamics [1-8]. These paradoxes are briefly reviewed. It is shown that each paradox results from a synergism of two broken symmetries - one geometric, one thermodynami

    Nonequilibrium heterogeneous catalysis in the long mean-free-path regime

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    It is shown that a standard principle of traditional catalysis-that a catalyst does not alter the final thermodynamic equilibrium of a reaction-can fail in low-pressure, heterogeneous gas-surface reactions. Kinetic theory for this epicatalysis is presented, and two well-documented experimental examples are detailed: surface ionized plasmas and hydrogen dissociation on refractory metals. This phenomenon should be observable over a wide range of temperatures and pressures, and for a broad spectrum of heterogeneous reactions. By transcending some constraints of equilibrium thermodynamics, epicatalysis might provide additional control parameters and synthetic routes for reactions, and enable product streams boosted in thermochemical energy or desirable species

    Casimir chemistry

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    It is shown that, at the nanoscale, the Casimir effect can be used to mechanically tune critical aspects of chemical reaction e.g., energies, equilibrium constants, activation energies, transition states, reaction rates by varying the spacing and composition of reaction vessel boundaries. This suggests new modalities for catalysts, nanoscale chemical manufacturing, chemical-mechanical engines, and biochemical processes in organisms

    Energy, Entropy and the Environment (How to Increase the First by Decreasing the Second to Save the Third)

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    Energy is the lifeblood of civilization, but inexpensive, high energy density sources are rapidly being depleted and their exploitation is severely degrading the environment. This paper explores a radical solution to this energy-environmental dilemma. In the last 10–15 years, the universality of the second law of thermodynamics has fallen into serious theoretical doubt [1–3].Should it prove experimentally violable, this would open the door to a nearly limitless reservoir of ubiquitous, clean, recyclable energy. If economical, it could precipitate paradigm shifts in energy production, utilization and politics. In this paper, recent challenges to the second law are reviewed, with focus given to one for which laboratory experiments are planned. Possible consequences of its violation for technology, society and the environment are explored

    Reply to ‘‘Comment on ‘Dynamically maintained steady-state pressure gradients’ ’’

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    A reply is made to Duncan’s Comment [T. L. Duncan, Phys. Rev. E 61, 4661 (2000)] on my earlier paper [D. P. Sheehan, Phys. Rev. E 57, 6660 (1998)] in which he raises an apparent second-law paradox arising from dynamically maintained, steady-state pressure gradients. Resolutions to this paradox are considered in light of current theoretical and experimental understanding

    Dynamically maintained steady-state pressure gradients

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    In a sealed blackbody cavity with gas, pressure gradients commonly take three forms: (a) statistical fluctuations, (b) transients associated with the system relaxing toward equilibrium, and (c)equilibrium pressure gradients associated with potential gradients (such as with gravity). In this paper, it is shown that in the low-density (collisionless) regime, a fourth type of pressure gradient may arise, this due to steady-state differential thermal desorption of surface species from chemically active surfaces. This gas phase is inherently nonequilibrium in character. Numerical simulations using realistic physical parameters support the possibility of this gas phase and indicate that these novel pressure gradients might be observable in the laboratory; candidate chemical systems are suggested. [S1063-651X(98)07406-6

    A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster

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    We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm continuum maps of compact radio sources in the Orion Nebular Cluster. We mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and 109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and 190 HST-identified proplyds (with significant overlap between those characterizations). We detected radio emission from 175 compact radio sources in the ONC, including 26 sources that were detected for the first time at these wavelengths. For each detected source we fit a simple free-free and dust emission model to characterize the radio emission. We extrapolate the free-free emission spectrum model for each source to ALMA bands to illustrate how these measurements could be used to correctly measure protoplanetary disk dust masses from sub-millimeter flux measurements. Finally, we compare the fluxes measured in this survey with previously measured fluxes for our targets, as well as four separate epochs of 1.3 cm data, to search for and quantify variability of our sources.Comment: 13 pages, 6 figures, 4 tables, ApJ, in pres

    Intrinsically biased electrocapacitive catalysis

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    We propose the application of the contact potential from metal-metal junctions or the built-in potential of semiconductor p-np-n junctions to induce or catalyze chemical reactions. Free of external sources, this intrinsic potential across microscale and nanoscale vacuum gaps establishes electric fields in excess of 10^7V/m. The electrostatic potential energy of these fields can be converted into useful chemical energy. As an example, we focus on the production of superthermal gas ions to drive reactions. Analysis indicates that this intrinsically biased electrocapacitive catalysis can achieve locally directed ion energies up to a few electron volts and local gas temperatureboosts in excess of 10^4K. Practical considerations for implementation and experimental tests are considered
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