Physical Sciences and Mathematics | Open Access Articles

Seasonality Of Dissolved Rare Earth Elements In The Lower Mississippi River, Alan M. Shiller Nov 2002

Seasonality Of Dissolved Rare Earth Elements In The Lower Mississippi River, Alan M. Shiller

Faculty Publications

[1] Dissolved rare earth element (REE) concentrations were determined in a 27-month time series of the lower Mississippi River. Overall, the results agree with limited previous investigations; that is, the river shows enrichment of heavy REEs relative to light REEs and also has a significant Ce anomaly. However, the previous investigations relied on only single samples from the river. This seasonal investigation reveals significant temporal variations in the river's REE chemistry. In particular, large ( approximately fivefold) variations in light REE concentrations are observed. The light REEs follow a seasonality similar to particle-reactive trace elements. Also, the Ce anomaly shows …

Go to article

Density And Conformation With Relaxed Substrate, Bulk, And Interface In Electrophoretic Deposition Of Polymer Chains, F.W. Bentrem, J. Xie, Ras B. Pandey Sep 2002

Density And Conformation With Relaxed Substrate, Bulk, And Interface In Electrophoretic Deposition Of Polymer Chains, F.W. Bentrem, J. Xie, Ras B. Pandey

Faculty Publications

Characteristics of relaxed density profile and conformation of polymer chains are studied by a Monte Carlo simulation on a discrete lattice in three dimensions using different segmental (kink-jump (K), crank-shaft (C), reptation (R)) dynamics. Three distinct density regimes, substrate, bulk, and interface, are identified. With the KC segmental dynamics, we find that the substrate coverage grows with a power law, d_s∝t^γ with a field (E) dependent non-universal exponent γ=0.23+0.7E. The bulk volume fraction d_b and the substrate polymer density (d_s) increases with the field with power-laws (d_{b …}

Go to article

Density Profile And Flow Of Miscible Fluid With Dissimilar Constituent Masses, Ras B. Pandey, D. Stauffer, R. Seyfarth, Luis A. Cueva, J.F. Gettrust, Warren Wood Jul 2002

Density Profile And Flow Of Miscible Fluid With Dissimilar Constituent Masses, Ras B. Pandey, D. Stauffer, R. Seyfarth, Luis A. Cueva, J.F. Gettrust, Warren Wood

Faculty Publications

A computer simulation model is used to study the density profile and flow of a miscible gaseous fluid mixture consisting of differing constituent masses (m(A) = m(B)/3) through an open matrix. The density profile is found to decay with the height proportional to exp(-m(A(B))h), consistent with the barometric height law. The flux density shows a power-law increase proportional to (p(c) - p)(a) with mu similar or equal to 2.3 at the porosity 1 - p above the pore percolation threshold 1 - p(c). (C) 2002 Elsevier Science B.V. All rights reserved.

Go to article

Interface Relaxation In Electrophoretic Deposition Of Polymer Chains: Effects Of Segmental Dynamics, Molecular Weight, And Field, Frank W. Bentrem, Jun Xie, Ras B. Pandey Apr 2002

Interface Relaxation In Electrophoretic Deposition Of Polymer Chains: Effects Of Segmental Dynamics, Molecular Weight, And Field, Frank W. Bentrem, Jun Xie, Ras B. Pandey

Faculty Publications

Using different segmental dynamics and relaxation, characteristics of the interface growth is examined in an electrophoretic deposition of polymer chains on a three (2+1)-dimensional discrete lattice with a Monte Carlo simulation. Incorporation of faster modes such as crankshaft and reptation movements along with the relatively slow kink-jump dynamics seems crucial in relaxing the interface width. As the continuously released polymer chains are driven (via segmental movements) and deposited, the interface width W grows with the number of time steps t, W∝t^β, (β ~0.4-0.8), which is followed by its saturation to a steady-state value W_{s …}

Go to article

The Effect Of Reactor Geometry On Frontal Polymerization Spin Modes, John A. Pojman, Jonathan Masere, Enrico Petretto, Mauro Rustici, Do-Sung Huh, Min Suk Kim, Vladimir Volpert Mar 2002

The Effect Of Reactor Geometry On Frontal Polymerization Spin Modes, John A. Pojman, Jonathan Masere, Enrico Petretto, Mauro Rustici, Do-Sung Huh, Min Suk Kim, Vladimir Volpert

Faculty Publications

Using reactors of different sizes and geometries the dynamics of the frontal polymerization of 1,6-hexanediol diacrylate (HDDA) and pentaerythritol tetraacrylate (PETAC), with ammonium persulfate as the initiator were studied. For this system, the frontal polymerization exhibits complex behavior that depends on the ratio of the monomers. For a particular range of monomers concentration, the polymerization front becomes nonplanar, and spin modes appear. By varying the reactor diameter, we experimentally confirmed the expected shift of the system to a greater number of "hot spots" for larger diameters. For square test tubes a "zig-zag" mode was observed for the first time in …

Go to article

Physical Sciences and Mathematics Commons^™

Full-Text Articles in Physical Sciences and Mathematics

Seasonality Of Dissolved Rare Earth Elements In The Lower Mississippi River, Alan M. Shiller

Faculty Publications

Density And Conformation With Relaxed Substrate, Bulk, And Interface In Electrophoretic Deposition Of Polymer Chains, F.W. Bentrem, J. Xie, Ras B. Pandey

Faculty Publications

Density Profile And Flow Of Miscible Fluid With Dissimilar Constituent Masses, Ras B. Pandey, D. Stauffer, R. Seyfarth, Luis A. Cueva, J.F. Gettrust, Warren Wood

Faculty Publications

Interface Relaxation In Electrophoretic Deposition Of Polymer Chains: Effects Of Segmental Dynamics, Molecular Weight, And Field, Frank W. Bentrem, Jun Xie, Ras B. Pandey

Faculty Publications

The Effect Of Reactor Geometry On Frontal Polymerization Spin Modes, John A. Pojman, Jonathan Masere, Enrico Petretto, Mauro Rustici, Do-Sung Huh, Min Suk Kim, Vladimir Volpert

Faculty Publications