A model for the scattering of high-frequency electromagnetic fields from dielectrics exhibiting thermally-activated electrical losses

An equivalent circuit model (ECM) approach is used to predict the scattering behavior of temperature-activated, electrically lossy dielectric layers. The total electrical response of the dielectric (relaxation + conductive) is given by the ECM and used in combination with transmission line theory to compute reflectance spectra for a Dallenbach layer configuration. The effects of thermally-activated relaxation processes on the scattering properties is discussed. Also, the effect of relaxation and conduction activation energy on the electrical properties of the dielectric is described

Apparatus for recording oscillation properties of a Penning ionization gauge at very high frequencies

Recording equipment for very high frequency oscillations in Penning ionization gaug

Glass formation, properties, and structure of soda-yttria-silicate glasses

The glass formation region of the soda yttria silicate system was determined. The glasses within this region were measured to have a density of 2.4 to 3.1 g/cu cm, a refractive index of 1.50 to 1.60, a coefficient of thermal expansion of 7 x 10(exp -6)/C, softening temperatures between 500 and 780 C, and Vickers hardness values of 3.7 to 5.8 GPa. Aqueous chemical durability measurements were made on select glass compositions while infrared transmission spectra were used to study the glass structure and its effect on glass properties. A compositional region was identified which exhibited high thermal expansion, high softening temperatures, and good chemical durability

Multidrug-resistant Escherichia coli and Tetracycline-resistant Enterococcus faecalis in wild raptors of Alabama and Georgia, USA

Wild birds inhabit in a wide variety of environments and can travel great distances. Thus, wild birds can possibly spread antimicrobial resistance along the way, and this may represent a potential public health concern. We characterized antimicrobial resistance in fecal Escherichia coli and Enterococcus faecalis in wild raptors in the southeastern US. Cloacal samples were collected from 118 wild raptors of 17 species from 18 counties in Alabama and 15 counties in Georgia. A total of 112 E. coli and 76 E. faecalis isolates were recovered, and we found significantly more antimicrobial-resistant E. coli (20/112, 18%) than E. faecalis (6/76, 8%; P = 0.05). Five antimicrobial-resistant genes: blaTEM-1, blaCTX-M-1, tet(M), cmlA, cat, and gyrA, were identified in antimicrobial-resistant E. coli isolates. Five of 13 (38%) ampicillin-resistant E. coli harbored both bla-TEM-1 and blaCTX-M-1 genes, indicating they are extended-spectrum beta-lactamase-carrying strains. Both of the tetracycline resistance genes, tet(M) and tet(L), were identified in E. faecalis isolates. Wild raptors seem to be a reservoir host of antimicrobial-resistant E. coli and E. faecalis and may represent a hazard to animal and human health by transmission of these isolates

Learning Race and Ethnicity: Hip-Hop 2.0

Part of the Volume on Learning Race and Ethnicity: Youth and Digital Media In the twenty-first century, a hip hop music label becomes an indispensable source for learning: a young person's resource for information otherwise suppressed by industry regulation, federally censored, or not considered "news worthy" across corporate broadcast modes of distribution. This chapter, "Hip Hop 2.0," examines how hip hop music label Web sites (Guerrillafunk.com and Slamjamz.com) provide an educational space where young people can interact, learn, and discuss "real world" problems via their commitments to popular culture. These internet music labels "sell" more than music. They broaden how cultural entrepreneurial production and innovative citizen initiatives can be re-interpreted by non-broadcast based media, while constituting a counter-public sphere for political activism and learning through networked digital media. Through these practices, we may witness the realization of the Internet's democratizing possibility at a time when these freedoms are not ensured, both off and online

Numerical and Physical Modeling of Turbulent Shear Flows

This dissertation is an evaluation of popular turbulence schemes; both three dimensional and depth-averaged, and also includes an experimental study on shallow near bed jets. The three dimensional and RNG turbulent closure schemes are evaluated for free and bounded shear flows. For free shear flows (circular and plane turbulent jets), the scheme with standard coefficient performs equally well and in some cases better than the renormalized group scheme in predicting growth rate, decay of centerline velocity and longitudinal velocity profiles. For turbulent kinetic energy across the jet, the inner region is better predicted by the RNG scheme. The second case used to evaluate the three dimensional schemes was a submerged hydraulic jump. This flow included a free surface and solid boundary creating larger shearing forces than in a free jet. The results showed the longitudinal velocity profiles and their maximum values, in vertical direction, were estimated better by the RNG scheme. The turbulent kinetic energy was overestimated in both magnitude and elevation of its maximum position in the flow. The elevation of the recirculation region was also over predicted by both schemes; however, its longitudinal extent was predicted well. A two-dimensional, depth-averaged flow model with the depth-averaged parabolic eddy viscosity, mixing length, and turbulent closure schemes was used to simulate flow patterns downstream of lock and dam structures. The mixing length scheme was modified and performed as well as the scheme in predicting the location and size of the recirculation zones, as well as the velocity profiles across the channel. Experimental measurements on shallow near bed jets are performed. For low submergence, the horizontal growth rates have two distinct regions, with the downstream region having a higher growth rate. The longitudinal velocity profiles in the horizontal plane are self-similar. The centerline decay was slower than that of a free jet