Volume 7 Issue 4 March 2009


Undergraduate Essay: Open Source Science



Megan Schield and Douglas Armstrong


Olivet Nazarene University, One University Avenue, Bourbonnais, Illinois 60914-2345 USA

Molecular Distribution Behavior of Cyanine Dyes in Aqueous Solution



David Baumann, Bryan Clark, Jared Garlick, and Hussein Samha


Department of Physical Science, Southern Utah University, Cedar City, Utah 84720 USA


The molecular distribution of the cyanine dye (5-chloro-2-[3-[5-chloro-3-(4-sulfobutyl)-2(3H)-benzothiazolylidine]-1-propenyl]-3-(4-sulfobutyl)-benzothiazolium hydroxide triethylamine salt, NK-3796) in aqueous solution was investigated using absorption and emission spectroscopy. Dimers of the dye are formed in concentrated solutions, while monomers dominate more diluted solutions. J aggregates are formed in solutions containing electrolytes such as sodium chloride, calcium chloride, and di-hydrogen ammonium phosphate. The dye readily forms J aggregates upon mixing with electrolyte. The J aggregates formation was followed spectroscopically by the appearance of a red-shifted narrow band centered at 653 nm in the absorption spectra. A similar shift is also observed in the emission spectra. The absorbance bandwidth is dependent on the charge of the cation of the electrolyte. This suggests different ground-state conformations for the J aggregates in solution.

Material Point Method Investigations of Trauma to Fluids and Elastic Solids Due to Finite Barriers


Authors and Affiliations:

J.L. Dean
Department of Aeronautical Engineering, Iowa State University, Ames, Iowa 50014 USA
M.W. Roth
Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614-0150 USA

Paul A. Gray
Department of Computer Science, University of Northern Iowa, Cedar Falls, Iowa 50614-0507 USA


A Material Point Method (MPM) algorithm is developed and utilized to investigate how the dynamics of (Langrangian) Navier-Stokes fluids as well as that of elastic solids is affected by trauma due to finite barriers. For the fluid simulations, material point particles are placed in a two dimensional pipe with various initial and boundary conditions and stationary perturbations to fluid flow. Results show that eddy currents are present not only in the wake of the perturbing object but are also responsible for disruption of laminar flow upstream from the barrier. An unfortunately relevant application for sudden finite trauma to an elastic solid involves simulations of an aircraft striking a large building under varying system conditions. The work presented here is introductory in nature; the potential ramifications and importance of continued study is discussed and emphasized.

Anisotropic Properties of Sculptured Thin Films



Drew Pulsifer, Andrew Jones and Tariq H. Gilani


Department of Physics, Millersville University, P. O. Box 1002, Millersville, Pennsylvania 17551 USA


The electrical anisotropy of Cr-Sculptured thin films has been studies as a function of growth angle of Cr columns on a glass substrate. A peak in resistivity anisotropy is found at growth angle of 72 ± 5^o.