Electromagnetic scattering from an extended laminar plasma column

This paper is concerned with examining in the laboratory the backscattering from a simplified ionized target in the form of an extended laminar plasma column. Measured results, compared with calculations based on a homogeneous model approximation that incorporates the measured electrical parameters of the column, show that the column scatters electromagnetic energy that is polarized with the electric vector along the axis of the column in the same manner as a homogeneous column of critical density with the column radius equal to that of the critical electron density contained within the column.     

The Fatality Analysis Reporting System as a tool for investigating racial and ethnic determinants of motor vehicle crash fatalities

The Fatality Analysis Reporting System (FARS) is a Department of Transportation database in the public domain that contains detailed information about fatalities resulting from motor vehicle crashes on public roadways in the United States since 1975. However, data on race and Hispanic ethnicity were not collected by FARS until 1999. Since then, completeness of reported racial and ethnic information has varied from State to State. To assess utility of FARS for investigating race- and ethnicity-specific risk factors associated with motor vehicle crash mortality, we examined yearly national and State-specific reporting rates of race and Hispanic ethnicity for 168,863 motor vehicle crash fatalities from 1999 to 2002. In 1999, national reporting was 85% for race and 78% for Hispanic ethnicity. Over the 4-year study period, a significant linear increase in annual reporting for both race and Hispanic ethnicity was evident at the national level, as reporting by individual States improved over time. In 2002, national reporting rates reached 90% for race and 88% for Hispanic ethnicity. Our findings indicate that FARS has become a valuable resource for population-based studies of motor vehicle crash mortality disparities that exist among racial and ethnic subpopulations in the United States.     

Diffusivity of solutes measured in glass capillaries using Taylor's analysis of dispersion and a commercial CE instrument

We present a strategy for the rapid, efficient, and accurate measurement of the coefficient of diffusion (D) of solutes using a commercial capillary electrophoresis (CE) instrument. This approach utilizes the classic analysis of Taylor of the dispersion of solutes pumped hydrostatically through glass capillaries. To obtain accurate values of D, we modified Taylor's analysis of dispersion to account for the finite time required to reach steady-state flow in the capillary when using a CE instrument. Neglecting this effect results in measured diffusivities of phenylalanine, a model solute, that are in error by as much as 60% when compared with published values. We provide an analysis of this effect and a simple strategy for avoiding these errors. Using this approach, we analyze profiles of concentration fronts and measured values of D for phenylalanine to within 5% of published values. We also analyze profiles of pulses of solute. To determine values of D accurately, measurements of dispersion first need to be made as a function of injection volume to correct for the finite width of the injection plug, before they are corrected for unsteady-state flow. This approach also yields values of D for phenylalanine to within 5% of published values. In contrast to other techniques used for the determination of D, this approach requires no fluorescent labeling and is applicable to solutes of any molecular weight.     

Surface-enhanced Raman scattering from individual au nanoparticles and nanoparticle dimer substrates

Surface-enhanced Raman scattering (SERS) intensities for individual Au nanospheres, nanoshells, and nanosphere and nanoshell dimers coated with nonresonant molecules are measured, where the precise nanoscale geometry of each monomer and dimer is identified through in situ atomic force microscopy. The observed intensities correlate with the integrated quartic local electromagnetic field calculated for each specific nanostructure geometry. In this study, we find that suitably fabricated nanoshells can provide SERS enhancements comparable to nanosphere dimers.     

Surface active agents from isopropenyl esters: Acylation of isethionic acid and N-methyltaurine

Acylation of sodium isethionate with isopropenyl stearate at 200 C for 30 min gave a 95% yield of sodium 2-sulfoethyl stearate, acetone being the only byproduct. Acylation of N-methyltaurine at 200 C for 90 min gave a 95% yield of N-methyl-N-(2-sulfoethyl) stearamide sodium salt. Corresponding surface active derivatives were also prepared from pelargonic, lauric, myristic, palmitic, oleic, phenylstearic and hydrogenated tallow fatty acids from their respective isopropenyl esters. Detergency, foam height, wetting time, lime soap dispersing power, critical micelle concentration and other surfactant properties were evaluated. Optimum properties were found at the C₁₄−C₁₈ fatty acid chain length. Unsaturation or branching increased solubility. The 2-sulfoethyl esters were similar to the N-methyl-N-(2-sulfoethyl) amides in foam height, wetting ability and lime soap dispersing power, superior to the N-methyl-N-(2-sulfoethyl) amides in detergency, but inferior in calcium stability and less stable to acid and alkali. Both compounds are readily biodegraded. The fatty isopropenyl ester synthesis has an advantage in yield and purity of the product and could increase the utilization of the 2-sulfoethyl esters and N-methyl-N-(2-sulfoethyl) amides in many applications. Presented at the ISF-AOCS Meeting in Chicago, September 1970. Deceased. E. Mark. Nutr. Res. Div., ARS, USDA.     

Planar p-on-n HgCdTe FPAs by Arsenic Ion Implantation

This paper reviews recent developments in the characterization of planar p-on-n photodiodes fabricated from long- and mid-wavelength Hg_1−x Cd _x Te at␣the Electronics and Information Technology Laboratory (LETI). The Hg_1−x Cd _x Te epitaxial layers were grown by both liquid-phase and molecular-beam epitaxy. Planar p-on-n photodiodes were fabricated by arsenic implantation into an indium-doped Hg_1−x Cd _x Te base layer. Electro-optical characterization on these p-on-n photodiodes showed low leakage currents (shunt resistance > 10 GΩ) and mean R ₀ A values comparable to the state of the art, i.e., equal to 5000 Ω cm² at λ _c = 9.3 μm (λ _c: cutoff wavelength). Results of focal-plane arrays operating in both the long-wavelength infrared (IR) and middle-wavelength IR bands are reported, with noise equivalent delta temperature and responsivity values at λ _c = 9.3 μm in excess of 99.64%. These results demonstrate the viability and technological maturity of both material growth and device processing.