Hot Mess

This thesis is a collection of short fiction written in fulfillment of the Master of Fine Arts in Creative Writing at the University of New Orleans

Microstructural refinement of cement paste internally cured by polyacrylamide composite hydrogel particles containing silica fume and nanosilica

Supplementary cementitious materials were incorporated into hydrogel-based internal curing agents to improve the hydration, microstructure, and ultimately strength of internally cured high-performance cement paste. Polyacrylamide composite hydrogel particles containing amorphous silica – either silica fume or nanosilica – and two different polymer network crosslink densities were synthesized and incorporated into cement paste. The presence of silica and low crosslink density increased the absorption capacity of the particles in pore solution. Micrographs of internally cured paste indicated a significant improvement in hydrogel-related void-filling ability and an increase in void size for low crosslink density particles containing silica. Compressive strength and electrical resistivity increased at later ages for paste samples containing particles with higher silica dosage. The relationship between extent of hydration, void size, and void-filling activity was found to strongly influence the paste\u27s long-term strength and is thus an important structure-property relationship to consider when selecting hydrogels for internal curing purposes

Lignopolymers As Viscosity-Reducing Additives in Magnesium Oxide Suspensions

Lignopolymers are a new class of polymer additives with the capability to be used as dispersants in cementitious pastes. Made with kraft lignin cores and grafted polymer side- chains, the custom-synthesized lignopolymers were examined in terms of the molecular architecture for viscosity reducing potential in inert model suspensions. Lignin-poly(acrylic acid) (LPAA) and lignin-polyacrylamide (LPAm) have been found to vary the rheology of magnesium oxide (MgO) suspensions based on differences in chain architecture and particle- polymer interactions. A commercial comb-polymer polycarboxylate ester was compared to LPAA and LPAm at 2.7 mg/mL, a typical dosage for cement admixtures, as well as 0.25 mg/mL. It was found that LPAm was a more effective viscosity reducer than both LPAA and the commercial additive at low concentrations, which was attributed to greater adsorption on the MgO particle surface and increased steric dispersion from PAm side-chain extension. The influence of chain adsorption and grafted side-chain molecular weight on rheology was also tested

Diverse diazotrophs are present on sinking particles in the North Pacific Subtropical Gyre.

Sinking particles transport carbon and nutrients from the surface ocean into the deep sea and are considered hot spots for bacterial diversity and activity. In the oligotrophic oceans, nitrogen (N2)-fixing organisms (diazotrophs) are an important source of new N but the extent to which these organisms are present and exported on sinking particles is not well known. Sinking particles were collected every 6 h over a 2-day period using net traps deployed at 150 m in the North Pacific Subtropical Gyre. The bacterial community and composition of diazotrophs associated with individual and bulk sinking particles was assessed using 16S rRNA and nifH gene amplicon sequencing. The bacterial community composition in bulk particles remained remarkably consistent throughout time and space while large variations of individually picked particles were observed. This difference suggests that unique biogeochemical conditions within individual particles may offer distinct ecological niches for specialized bacterial taxa. Compared to surrounding seawater, particle samples were enriched in different size classes of globally significant N2-fixing cyanobacteria including Trichodesmium, symbionts of diatoms, and the unicellular cyanobacteria Crocosphaera and UCYN-A. The particles also contained nifH gene sequences of diverse non-cyanobacterial diazotrophs suggesting that particles could be loci for N2 fixation by heterotrophic bacteria. The results demonstrate that diverse diazotrophs were present on particles and that new N may thereby be directly exported from surface waters on sinking particles

Characterization of Suspension Polymerized Polyacrylamide and Poly(sodium acrylate-acrylamide) Copolymer and their Size Influence on the Properties of Concrete

Shrinkage leading to cracking and mechanical instability is a major problem for concrete due to the loss of water during the curing process. However, through the addition of Superabsorbent Polymer (SAP) hydrogels, shrinkage can be prevented, increasing the strength of concrete. Characterization of suspension polymerized polyacrylamide (PAM) poly(sodium acrylate-polyacrylamide) (PANa-PAM) copolymer microsphere sizes, morphology and swelling behavior was conducted before adding them to concrete. Size was determined using microscopy paired with ImageJ analysis. Coulter Counter size characterization was also used to determine the particle size distribution. Swelling behavior was determined using the tea bag method as well as size analysis before and after hydration. After characterization, concrete containing various sizes of SAP microspheres will be tested for shrinkage and mechanical strength. These tests will allow us to discover the optimal size of SAP microspheres in concrete to increase its mechanical properties as well as control shrinkage. We will also investigate if the shape of particles has an impact on the final properties of the concrete. The results of this study will contribute to the growing knowledge of applying SAPs in concrete and will give a better understanding on how the size and shape of SAP hydrogels influence the properties of concrete. Using this knowledge, concrete can be made to perform better resulting in more mechanically sound structures

Hierarchical processing in adolescents : a comparison of nonverbal and verbal tasks

Speec

The perceived role of biological father contact in the self-estem development of young African American women : an exploratory study

This qualitative study was designed to explore how young self-identified women of African American and African descent describe the connection between their father-daughter relationships and their self-esteem development. This exploratory study presents findings and narratives from the perspectives of 14 self-identified women of African American and African descent between the ages of 22- 30 who had face-to face contact with their biological fathers for at least five years throughout their lives. It was expected that the African American women in this study would speak to their experiences of paternal love or rejection in ways, which were tied positively or negatively to their self-esteem. The majority of participants (n= 9) saw a connection between their self-esteem and their relationship with their biological fathers. All nine women who reported seeing a connection between their father-daughter relationship and their self-esteem also reported having high self-esteem and close father-daughter relationships. Four key phenomenological themes describing how biological fathers positively shape an African American daughter\u27s self-esteem were identified: 1) support and positive reinforcement of daughter\u27s physical attractiveness and intellectual strengths, 2) general non-judgmental support, 3) conveying positive messages about racial/ethnic pride and standards of beauty, and 4) modeling appropriate boundaries for daughters in intimate relationships

Climate change impacts go beyond the surface: Groundwater recharge rates and aquifer resources across the Contiguous United States

Groundwater is a primary source of potable water for millions and a major source for crop irrigation in the United States. Thus, it is vital to understand current and future rates of recharge to predict and manage groundwater availability. In this study, current groundwater recharge rates across the Contiguous US at 800m resolution are estimated by following methods presented by Reitz et al. (2017), and the reproducibility of the methods are assessed. A water budget approach is implemented where quick flow runoff and evapotranspiration rates are subtracted from precipitation rates. Precipitation was found to be the most reproducible water budget component, whereas evapotranspiration and quick flow runoff were found to be more sensitive aspects of the model. Final recharge estimates, dependent on the three water budget components, reflect inaccuracies produced in estimating precipitation, quick flow runoff, and evapotranspiration. Patterns in recharge rates are examined alongside the geospatial distribution of precipitation in the context of large-scale atmospheric circulation systems. In addition, changes to precipitation patterns that are expected to occur over the 21st century such as increasing precipitation in the Midwest and decreasing precipitation in the Southwest, are presented as a way of estimating changes to future groundwater recharge rates. Agriculture in the US relies heavily on groundwater resources, thus increased precipitation in the Midwest and decreased precipitation in the Southwest are expected the drastically alter US food production