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Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
Nonlinear Parallel And Perpendicular Diffusion Of Charged Cosmic Rays In Weak Turbulence, Andreas Schalchi, John William Bieber, William H. Matthaeus, Gang Qin
Nonlinear Parallel And Perpendicular Diffusion Of Charged Cosmic Rays In Weak Turbulence, Andreas Schalchi, John William Bieber, William H. Matthaeus, Gang Qin
Aerospace, Physics, and Space Science Faculty Publications
The problem of particle transport perpendicular to a magnetic background field is well known in cosmic-ray astrophysics. Whereas it is widely accepted that quasi-linear theory (QLT) of particle transport does not provide the correct results for perpendicular diffusion, it was assumed for a long time that QLT is the correct theory for parallel diffusion. In the current paper we demonstrate that QLT is in general also incorrect for parallel particle transport if we consider composite turbulence geometry. Motivated through the recent success of the so-called nonlinear guiding center theory of perpendicular diffusion, we present a new theory for parallel and …
The Li Overabundance Of J37: Diffusion Or Accretion?, J F. Ashwell, R D. Jeffries, C P. Deliyannis, A Steinhauer, Jeremy R. King
The Li Overabundance Of J37: Diffusion Or Accretion?, J F. Ashwell, R D. Jeffries, C P. Deliyannis, A Steinhauer, Jeremy R. King
Publications
In September 2002 the discovery of a super Li-rich F-dwarf (J37) in NGC 6633, an iron poor analogue of the better studied Hyades and Praecepe open clusters, was announced. This unique star was thought to be the smoking gun for the action of diffusion, models of which predict a narrow ”Li-peak” at approximately the correct temperature. However, with more detailed studies into J37s abundance pattern this star provides firm evidence for the accretion of planetesimals or other material from the circumstellar environment of new born stars. Thanks to the specific predictions made about the behaviour of Be abundances, (the most …
Investigation Of The Diffusion Processes In Self-Processing Acrylamide-Based Photopolymer System, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Suzanne Martin, Vincent Toal
Investigation Of The Diffusion Processes In Self-Processing Acrylamide-Based Photopolymer System, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Suzanne Martin, Vincent Toal
Articles
Results from the investigation of the diffusion processes in a dry acrylamide-based photopolymer system are presented. The investigation is carried out in the context of experimental work on optimization of the high spatial frequency response of the photopolymer. Tracing the transmission holographic grating dynamics at short times of exposure is utilized to measure diffusion coefficients. The results reveal that two different diffusion processes contribute with opposite sign to the refractive index modulation responsible for the diffraction grating build up. Monomer diffusion from dark to bright fringe areas increases the refractive index modulation. It is characterized with diffusion constant D0=1.6E-7 cm2/s. …
Tomex: Mesospheric And Lower Thermospheric Diffusivities And Instability Layers, R. L. Bishop, M. F. Larsen, J. H. Hecht, Alan Z. Liu, C. S. Gardner
Tomex: Mesospheric And Lower Thermospheric Diffusivities And Instability Layers, R. L. Bishop, M. F. Larsen, J. H. Hecht, Alan Z. Liu, C. S. Gardner
Physical Sciences - Daytona Beach
The Turbulent Oxygen Mixing Experiment (TOMEX), which was carried out at White Sands Missile Range in New Mexico on 26 October 2000, included a rocketborne trimethyl aluminum (TMA) chemical tracer experiment. The subsequent TMA trails provided detailed information about the horizontal neutral wind, turbulence, and diffusivity properties of the atmosphere between approximately 85 and 140 km altitude. Measurements with the University of Illinois Na wind/temperature lidar located at the Starfire Optical Range, NM, provided a detailed time history of the stability properties between 85 and 105-km altitude, including high-resolution wind and temperature measurements prior to and during the chemical tracer …
Diffusional Interactions At Dual Disk Microelectrodes: Comparison Of Experiment With Three-Dimensional Random Walk Simulations, John E. Baur, Perry N. Motsegood
Diffusional Interactions At Dual Disk Microelectrodes: Comparison Of Experiment With Three-Dimensional Random Walk Simulations, John E. Baur, Perry N. Motsegood
Faculty Publications – Chemistry
Three dimensional random walk simulations were used to model the diffusional interactions between coplanar dual disk microelectrodes. Working curves for the dependence of shielding factor, collection efficiency, and amplification factor on the size of the gap between the electrodes were developed. The simulations showed that when the gap size was ≥22 radii, the electrodes could be considered as independent and diffusionally isolated. Empirical equations for determining the gap size from simple shielding and generator-collector experiments were established. The simulation was used to model the collector electrode response for square waves of various frequencies applied to the generator electrode. Simulation results …
Dynamics Of Complex Polymer Solutions: Putting Diffusion To Work And Exploring Rigid Rod Diffusion, Garrett John Doucet
Dynamics Of Complex Polymer Solutions: Putting Diffusion To Work And Exploring Rigid Rod Diffusion, Garrett John Doucet
LSU Doctoral Dissertations
This dissertation is concerned with random coil and rodlike polymer diffusion in complex solutions. The development of fluorescence photobleaching recovery, FPR, as a technique to determine polymer molecular weight distributions by measuring the diffusion distribution and converting it to a molecular weight distribution using a calibration curve is first covered. Fluorescently tagged probes were individually dissolved in polymer solutions at negligible amounts and measured with FPR to construct the calibration curve of self-diffusion vs. molecular weight. Once calibration curves were constructed, bimodal distributions were separated using the matrices corresponding to the calibration curves. The diffusion of the probes and separation …
Diffusion Effect On The Anodic Reactions Of Tungsten, Mustafa Anik, Tuba Cansizoğlu, Si̇nem Çevi̇k
Diffusion Effect On The Anodic Reactions Of Tungsten, Mustafa Anik, Tuba Cansizoğlu, Si̇nem Çevi̇k
Turkish Journal of Chemistry
Potentiodynamic and potentiostatic polarizations, and a rotating disk electrode technique were used to study the influence of diffusion on the anodic reactions of tungsten (W) in a broad pH range (\sim 0.3--13.5) in H_3PO_4 buffered solutions. The anodic current was controlled totally by the kinetics of H^+ -assisted dissolution below pH 1 (Region A). At around pH 2.5 (Region B), in addition to the kinetics of H_2O-assisted dissolution, specimen rotation had an effect on the current. This observation was attributed mainly to the physical damage to an oxide phase by hydrodynamic effects and partly to the diffusion of surface H_2WO_4(aq) …