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Full-Text Articles in Physics
Nonequilibrium Heterogeneous Catalysis In The Long Mean-Free-Path Regime, D. P. Sheehan
Nonequilibrium Heterogeneous Catalysis In The Long Mean-Free-Path Regime, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
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 …
Infrared Cloaking, Stealth, And The Second Law Of Thermodynamics, D. P. Sheehan
Infrared Cloaking, Stealth, And The Second Law Of Thermodynamics, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
Infrared signature management (IRSM) has been a primary aeronautical concern for over 50 years. Most strategies and technologies are limited by the second law of thermodynamics. In this article, IRSM is considered in light of theoretical developments over the last 15 years that have put the absolute status of the second law into doubt and that might open the door to a new class of broadband IR stealth and cloaking techniques. Following a brief overview of IRSM and its current thermodynamic limitations, theoretical and experimental challenges to the second law are reviewed. One proposal is treated in detail: a high …
Casimir Chemistry, D. P. Sheehan
Casimir Chemistry, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
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), D. P. Sheehan
Energy, Entropy And The Environment (How To Increase The First By Decreasing The Second To Save The Third), D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
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 …
Intrinsically Biased Electrocapacitive Catalysis, D. P. Sheehan, T. Seideman
Intrinsically Biased Electrocapacitive Catalysis, D. P. Sheehan, T. Seideman
Physics and Biophysics: Faculty Scholarship
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 …
The Second Law Mystique, Alexey V. Nikulov, D. P. Sheehan
The Second Law Mystique, Alexey V. Nikulov, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
No abstract provided.
Simple, Compact Source For Low-Temperature Air Plasmas, D. P. Sheehan, J. Lawson, M. Sosa, R. A. Long
Simple, Compact Source For Low-Temperature Air Plasmas, D. P. Sheehan, J. Lawson, M. Sosa, R. A. Long
Physics and Biophysics: Faculty Scholarship
A simple, compact source of low-temperature, spatially and temporally uniform air plasma using a Telsa induction coil driver is described. The low-power ionization discharge plasma is localized (2 cm X 0.5 cm X 0.1 cm) and essentially free of arc channels. A Teflon coated rolling cylindrical electrode and dielectric coated ground plate are essential to the source’s operation and allow flat test samples to be readily exposed to the plasma. The plasma is a copious source of ozone and nitrogen oxides. Its effects on various microbes are discussed.
On The Persistence Of Small Regions Of Vorticity In The Protoplanetary Nebula, S. S. Davis, D. P. Sheehan, J. N. Cuzzi
On The Persistence Of Small Regions Of Vorticity In The Protoplanetary Nebula, S. S. Davis, D. P. Sheehan, J. N. Cuzzi
Physics and Biophysics: Faculty Scholarship
The fate of small regions of vorticity in a barotropic model of the protoplanetary nebula is investigated over thousands of years using a finite difference model. It is found that the coherence time for a small island of vorticity depends on its size, strength, orientation, and radial location in the nebula. Anticyclonic vorticity retains its coherence for longer times than cyclonic vorticity due to favorable interactions with the Keplerian shear flow. Rossby waves are generated as a result of mean vorticity gradients across the disk. The two-dimensional nebula evolves from discrete vortices into an axisymmetric flow consisting of small-amplitude vortex …
Reply To ‘‘Comment On ‘Dynamically Maintained Steady-State Pressure Gradients’ ’’, D. P. Sheehan
Reply To ‘‘Comment On ‘Dynamically Maintained Steady-State Pressure Gradients’ ’’, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
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, D. P. Sheehan
Dynamically Maintained Steady-State Pressure Gradients, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
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 …
Four Paradoxes Involving The Second Law Of Thermodynamics, D. P. Sheehan
Four Paradoxes Involving The Second Law Of Thermodynamics, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
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 thermodynamic
Ion Acceleration And Anomalous Transport In The Near Wake Of A Plasma Limiter, D. P. Sheehan, J. Bowles, R. Mcwilliams
Ion Acceleration And Anomalous Transport In The Near Wake Of A Plasma Limiter, D. P. Sheehan, J. Bowles, R. Mcwilliams
Physics and Biophysics: Faculty Scholarship
Ion acceleration and anomalous transport were studied experimentally in the near wake region of an electrically floating disk limiter immersed in two different types of collisionless, supersonically flowing, magnetized plasmas: the first initially quiescent, the second initially turbulent. Ion densities and velocity distributions were obtained using a nonperturbing laser induced fluorescence diagnostic. Large-amplitude, low-frequency turbulence was observed at the obstacle edge and in the wake. Rapid ion and electron configuration space transport and ion velocity space transport were observed. Configuration space and velocity space transport were similar for both quiescent and turbulent plasma-obstacle systems, suggesting that plasma-obstacle effects outweigh the …
Response To ‘‘Comment On ‘A Paradox Involving The Second Law Of Thermodynamics’ ’’ [Phys. Plasmas 2, 1893 (1995)], D. P. Sheehan
Response To ‘‘Comment On ‘A Paradox Involving The Second Law Of Thermodynamics’ ’’ [Phys. Plasmas 2, 1893 (1995)], D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
No abstract provided.
Interaction Of An Expanding Plasma Cloud With A Simple Antenna: Application To Anomalous Voltage Signals Observed By Voyager 1, Voyager 2, Ice, And Vega Spacecraft, D. P. Sheehan, C. A. Casey, L. T. Volz
Interaction Of An Expanding Plasma Cloud With A Simple Antenna: Application To Anomalous Voltage Signals Observed By Voyager 1, Voyager 2, Ice, And Vega Spacecraft, D. P. Sheehan, C. A. Casey, L. T. Volz
Physics and Biophysics: Faculty Scholarship
High‐velocity impacts of interplanetary dust grains with spacecraft can give rise to transient plasma clouds from the spacecraft bodies. It is believed these plasma clouds can affect spacecraft instruments. Laboratory results are presented demonstrating the interaction of small expanding plasma clouds with a simple antenna. Results corroborate the hypothesized origin of anomalous impulsive voltage signals recorded by Voyager 1 and 2 spacecraft during flybys of Saturn, Uranus, and Neptune, the International Cometary Explorer (ICE) during its flyby of comet Giacobini‐Zinner, and Vega during its flyby of comet Halley. Results suggest that preflight calibration of antenna‐plasma interactions may extend the range …
Adjustable Levels Of Strong Turbulence In A Positive/Negative Ion Plasma, D. P. Sheehan, R. Mcwilliams, N. Rynn
Adjustable Levels Of Strong Turbulence In A Positive/Negative Ion Plasma, D. P. Sheehan, R. Mcwilliams, N. Rynn
Physics and Biophysics: Faculty Scholarship
Positive/negative ion plasmas, composed of Ba+, SF6−, and residual electrons, were observed to display characteristics of strong turbulence.Experiments on the UCI Q machine linked the presence of negative ions (and the depletion of electrons) with large density fluctuations (δn/n≂1), large‐amplitude, low‐frequency electrostatic noise (f≤20 kHz), and rapid transport of ions across magnetic field lines (D⊥≂104 cm2/sec). Ion velocity distributions were heated parallel to and cooled perpendicular to the confining magnetic field. The partial pressure of gaseous SF6 was shown to serve as a regulator of plasma turbulence. Turbulence levels could be smoothly varied from quiescent states (δn/n≂0.01) to strongly turbulent …
Laboratory Simulations Of Suprauroral Mechanisms Leading To Perpendicular Ion Heating And Conic Formation, D. P. Sheehan, R. Koslover, R. Mcwilliams
Laboratory Simulations Of Suprauroral Mechanisms Leading To Perpendicular Ion Heating And Conic Formation, D. P. Sheehan, R. Koslover, R. Mcwilliams
Physics and Biophysics: Faculty Scholarship
Laboratory experiments are presented simulating aspects of perpendicular ion heating and conic formation that are observed or hypothesized to occur in the terrestrial ionosphere and magnetosphere. Previous laboratory observations of ion conics in the presence of the current‐driven electrostatic ion cyclotron wave are reviewed. Field‐aligned ion beams, accompanied by beam‐generated electrostatic ion cyclotron modes, resulted in perpendicular energization of beam ions and also the heating of background plasma ions. Antenna‐launched broadband and narrow‐band lower hybrid waves produced considerable perpendicular ion heating and non‐Maxwellian “tail” formation. Laboratory results are discussed in light of in situ measurements by the S3‐3 satellite and …
Device For Dispersal Of Micrometer- And Submicrometer-Sized Particles In Vaccum, D. P. Sheehan, M. Carillo, W. Heidbrink
Device For Dispersal Of Micrometer- And Submicrometer-Sized Particles In Vaccum, D. P. Sheehan, M. Carillo, W. Heidbrink
Physics and Biophysics: Faculty Scholarship
A simple, versatile device for dispersing micrometer‐ and submicrometer-sized particles in vacuum is described. The source allows control of particle size (0.5 μm≤l≤200 μm) and particle flux density up to roughly 107 cm−2 s−1. Several types of microparticles were successfully dispersed.
Simple Overdense Rf Plasma Source, R. Mcwilliams, D. Edrich, R. C. Platt, D. P. Sheehan
Simple Overdense Rf Plasma Source, R. Mcwilliams, D. Edrich, R. C. Platt, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
A simple, gas‐fed, radio‐frequency‐driven plasma source is described. By use of lower hybrid waves, noble gas plasmas were produced with electron densities up to 10^12 cm -3 over a range of magnetic fields from 400 G to 1.5 kG and rf frequencies from 2–220 MHz.
Fast-Wave Current Drive Above The Slow-Wave Density Limit, D. P. Sheehan, R. Mcwilliams, N. S. Wolf, D. Edrich
Fast-Wave Current Drive Above The Slow-Wave Density Limit, D. P. Sheehan, R. Mcwilliams, N. S. Wolf, D. Edrich
Physics and Biophysics: Faculty Scholarship
Fast-wave and slow-wave current drive near the mean gyrofrequency were compared in the Irvine Torus. The slow-wave current drive density limit observation was extended by an order of magnitude in wave frequency compared to previous tokamak results. At low densities, the fast-wave antenna was observed to launch slow waves which drove currents that suffered from the current drive density limit identical to waves launched from the slow-wave antenna. At higher densities, current was driven by the fast-wave antenna while none was driven by the slow-wave antenna.
Experimental Measurements Of Phase Space, Roger Mcwilliams, D. P. Sheehan
Experimental Measurements Of Phase Space, Roger Mcwilliams, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
Direct measurements of integrated phase-space densities, e.g., f(x,vy,t), have been made in an experiment. Using spectroscopically active ions, measurements in a plasma show the ion response, fi(x,v,t), to linear and nonlinear waves and phase-space particle bunching. Time-resolved measurements show coherent and incoherent phase-space density changes in the presence of waves, indicating that transitions to turbulence and chaos may be studied. The time, space, and velocity-space resolution may allow experimental tests of predictions from the Boltzmann equation.
The Production Of Highly Unidirectional Lower-Hybrid Waves, R. Mcwilliams, M. Okubo, R. C. Platt, D. P. Sheehan
The Production Of Highly Unidirectional Lower-Hybrid Waves, R. Mcwilliams, M. Okubo, R. C. Platt, D. P. Sheehan
Physics and Biophysics: Faculty Scholarship
The development of a highly unidirectional lower-hybrid wave source would improve the electron current drive efficiency in tokamaks. Lower-hybrid waves launched from a phased wave array are shown to be reflected from a grid placed in a cold, low-density plasma. The antenna-grid combination results in highly unidirectional lower-hybrid waves.