Carboxylic Acid Functionalized Butyl Rubber: From Synthesis to Applications

Butyl Rubber (RB) is a copolymer of isobutylene (IB) with small percentages of isoprene (IP). Typically these IP units serve as sites for the covalent cross-linking of the rubber, but they can also serve as sites to further functionalize RB. These modifications can expand the potential applications of RB. This thesis describes the synthesis of carboxylic acid functionalized RB and some properties and applications of these materials

Positron-rubidium scattering

A 5-state close-coupling calculation (5s-5p-4d-6s-6p) was carried out for positron-Rb scattering in the energy range 3.7 to 28.0 eV. In contrast to the results of similar close-coupling calculations for positron-Na and positron-K scattering the (effective) total integrated cross section has an energy dependence which is contrary to recent experimental measurements

Numerical Green's functions in optical potential calculations for positron scattering from argon and neon

An optical potential method was applied to the calculation of positron scattering from the noble gases in order to determine the effect of open excitation channels on the shape of differential scattering cross sections

Improving the design of saturated riparian buffers for removing nitrate from subsurface drainage

In the U.S. Midwest, agricultural subsurface drainage, or tile, is commonly used to improve crop production; however, because nitrate is easily leached, tile drainage typically has high nitrate loads. Nitrate exported via tile drainage impairs water quality and can be reduced by implementing conservation practices, such as saturated riparian buffers (SRBs). SRBs function by redistributing the nitrate-rich tile drainage through the soil of a vegetated buffer zone via a perforated distribution pipe, facilitating denitrification and plant uptake. Because this practice is relatively new, there has been limited research into how SRBs function and how to effectively design them. In the first study, an equation for the optimal SRB width was derived by applying a mass balance to maximize the nitrate removal effectiveness. The optimal width is smaller than the current width at each of the six study sites, and two sites have optimal widths that are smaller than the minimum width specified in the current NRCS design standards. In the second study, a three-dimensional, finite-difference groundwater flow model was developed to better understand how groundwater flows in SRBs. Because flow is one-dimensional in most of the SRB, assuming one-dimensional groundwater flow in an SRB is reasonable. The median error associated with computing the travel time using a one-dimensional approximation is 11.6%. The flow path of the tile drainage toward the stream depends on where it exits the distribution pipe; the flow that exits through the top perforations at the end of the distribution pipe has the greatest potential for nitrate removal. Better understanding how groundwater flows in an SRB is an important step toward improving design to more effectively improve water quality

Positron excitation of neon

The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions

Emerging patterns of species richness, diversity, population density, and distribution in the skates (Rajidae) of Alaska

Six years of bottom-trawl survey data, including over 6000 trawls covering over 200 km2 of bottom area throughout Alaska’s subarctic marine waters, were analyzed for patterns in species richness, diversity, density, and distribution of skates. The Bering Sea continental shelf and slope, Aleutian Islands, and Gulf of Alaska regions were stratified by geographic subregion and depth. Species richness and relative density of skates increased with depth to the shelf break in all regions. The Bering Sea shelf was dominated by the Alaska skate (Bathyraja parmifera), but species richness and diversity were low. On the Bering Sea slope, richness and diversity were higher in the shallow stratum, and relative density appeared higher in subregions dominated by canyons. In the Aleutian Islands and Gulf of Alaska, species richness and relative density were generally highest in the deepest depth strata. The data and distribution maps presented here are based on species-level data collected throughout the marine waters of Alaska, and this article represents the most comprehensive summary of the skate fauna of the region published to date