Background: The need to control moisture and contamination is crucial in adhesive dentistry, especially when rubber dam isolation is not feasible. Hemostatic contamination can negatively affect adhesion to tooth substrate. To achieve better outcomes, hemostatic agents should be rinsed off properly using a method that will remove the contamination and will not affect the μ-SBS. Objective: To evaluate and compare the effect of three different aluminum chloride and ferric sulfate contamination removal methods on the μ-SBS of lithium disilicate glass-ceramic bonded to enamel and to compare the type of fracture between samples. Material and Methods: Lithium disilicate blocks (IPS e.max CAD) were cut into samples of 2 mm in diameter and 3mm in height. Thirty-five human molar teeth were collected and separated into seven groups (n=17) Groups: G1(control): No contamination. G2: Contamination with aluminum chloride and removal by 30 seconds water-rinse. G3: Contamination with aluminum chloride, removal by re-etching (37.5% phosphoric acid), water-rinse. G4: Contamination with aluminum chloride, removal with 18% EDTA G5: Contamination with ferric sulfate, removal with water-rinse. G6: Contamination with ferric sulfate, removal by re-etching (37.5% phosphoric acid), water-rinse and dried. G7: Contamination with ferric sulfate, removal with 18% EDTA. The enamel surface was etched, then contaminated with aluminum chloride and ferric sulfate, cleaned using 3 different methods, previously described. Ceramic samples were etched with HF acid, silanated then bonded to enamel surface using Optibond FL, Variolink veneer cement and the Elipar S10 curing light, to avoid oxygen inhibition restoration margins were cover with a glycerin to complete polymerization of 10 -30 seconds each side. Specimens were stored in deionized water for 7 days, then subjected to μ-SBS testing, fractured specimens were examined with a stereomicroscope to determine the type of fracture, and five sample of each group were selected for SEM. To compare differences for the outcome a general linear mode ANOVA was created, and data recorded. Results: There were statistically significant differences among the studied groups for the μ-SBS (p< 0.05). The G6 (Ferric sulfate- Re-etching) was the closest mean μ-SBS (10.75 MPa) to the G1(control group).μ-SBS (16.24 MPa), the lowest μ-SBS (6.13 MPa) for the G4 (Aluminum chloride-EDTA). The groups using ferric sulfate as a cleaning method presented higher μ-SBS MPa than the groups using aluminum chloride as a cleaning method. The type of fracture on groups with higher μ-SBS (MPa), G6 - 10.75 MPa (ferric sulfate-reetching), G5 - 9.21 μ-SBS(MPa) (Ferric sulfate-water) presented more cohesive fractures, while groups with lower μ-SBS(MPa), G4 – 6.13 MPa (Aluminum chloride- EDTA), G3 – 6.27 (aluminum chloride- re- etching) presented more mixed fractures. Conclusions: The present study sought to investigate the effect of three different contamination removal methods on bond strength of ceramic to enamel contaminated with aluminum chloride and ferric sulfate. Ferric sulfate hemostatic agent showed higher μ-SBS in all contamination removal methods when compare to aluminum chloride hemostatic agent. But all the contamination removal methods in both groups failed to increase the bond strength on enamel to the level of the control group. Further research is required before we can make definitive conclusions

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Organic methods development has long dictated the molecular scaffolds available to the pharmaceutical and fine chemical synthesis industries. Photoredox catalysis has emerged as a powerful platform to enable novel reactivity with visible light irradiation through triplet sensitization and single-electron transfer. New methods involving radical intermediates are now readily accessible from countless starting materials through the application of these catalysts. Much of my work has utilized established photoredox platforms to enable both nickel catalyzed remote cross-coupling of primary amines via 1,5 hydrogen-atom transfer (HAT) and formal [3+2] synthesis of γ-lactams through triplet sensitization. My further work focuses on the application of ligand-to-metal charge transfer catalysis with cupric chloride and ferric chloride salts towards the alkylation of alkanes through the catalytic generation of chlorine radical to enable HAT. These studies expand photoredox catalysis to inner sphere mechanisms with abundant base-metal salts to enable redox chemistry at reduced electrochemical potentials.

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The objectives of this study were to (1) determine an intermittent aeration strategy that could be used to conserve nitrogen (N) via nitrification in dairy manure, (2) determine the effect of recycled flush water on the bio-availability of N during nitrification, and (3) determine effective and economical dosages of chemicals to remove phosphorus (P) from liquid dairy manure. Intermittent aeration strategies, defined in terms of time the aerator is on and off (ON h:OFF h), could be used to conserve N in dairy manure. Testing of four treatments (continuous aeration [100%], 1h:0.33h [75%], 1h:0.67h [60%], and 1h:1h [50%]) showed that only treatments using air provided for 100% and 75% of the time could support nitrification. The 100% and 75% aeration treatments conserved an average of 38% and 25% of influent total ammonia nitrogen (TAN) as nitrite-N+nitrate-N, respectively. Less than 2% of influent TAN was conserved using 60% and 50% treatments. The effect of manure handling technique on N bioavailability and nitrification was tested using flushed and scraped dairy manure. Nitrification was inhibited in scraped manure. Four aluminum- and iron-based salts and five cationic polyacrylamide polymers were evaluated for P removal using jar tests. Ferric chloride (FeCl3·6H2O), aluminum sulfate (Al2[SO4]3·13H2O, alum), and Superfloc 4512 were selected for further study. Polymer addition enhanced floc size and improved P removal. Treatment of manure (0.89% total solids) from Tank 2 at Virginia Tech's dairy using either FeCl3 or alum in combination with polymer resulted in more than 90% P removal. Chemical treatment and transport of P-rich sludge from a 2,270 cubic meter storage tank would result in an estimated 40% cost savings over transport of the entire manure volume offsite for land application elsewhere. The manure treatment strategies tested provide some solutions to dairy farmers regarding adjustment of N:P ratios so that manure can be applied to meet nutrient needs of crops while adhering to regulations set forth by nutrient management plans. / Master of Science

Effective coagulation is critical to the production of safe, potable drinking water, but variations in the chemical composition of source water can present challenges in achieving targeted contaminant removal and predicting coagulation outcomes. A critical literature review describes factors affecting the hydrolysis reactions of metal salt coagulants and the resulting precipitates. Properties of two key contaminants, turbidity and natural organic matter (NOM), are explored in the context of removal during coagulation, and the influence of co-occurring ions is described. While it is apparent that NOM character determines the minimum achievable organic carbon residual, the effects of water quality—including pH, NOM character and concentration, and concentrations of synergistic and competitive ions—on overall coagulation efficacy and NOM removal may be underestimated. An experimental research plan was devised to investigate the influence of water quality in coagulation and provide data to support the development of a predictive coagulation model. NOM is capable of interfering with ferric iron hydrolysis and influencing the size, morphology, and identity of precipitates. Conversely, calcium is known to increase the size and aggregation of Fe3+ precipitates and increase surface potential, leading to more effective coagulation and widening the pH range of treatment. Experiments and modeling were conducted to investigate the significance of the Fe/NOM ratio and the presence of calcium in coagulation. At the high Fe/NOM ratio, sufficient or excess ferric hydroxide was available for NOM removal, and coagulation proceeded according to expectations based upon the literature. At the low Fe/NOM ratio, however, NOM inhibited Fe3+ hydrolysis, reduced zeta potential, and suppressed the formation of filterable Fe flocs, leading to interference with effective NOM removal. In these dose-limited systems, equilibrating NOM with 1 mM Ca2+ prior to dosing with ferric chloride coagulant increased the extent of Fe3+ hydrolysis, increased zeta potential, decreased the fraction of colloidal Fe, and improved NOM removal. In dose-limited systems without calcium, complexation of Fe species by NOM appears to be the mechanism by which coagulation is disrupted. In systems with calcium, data and modeling indicate that calcium complexation by NOM neutralizes some of the negative organic charge and minimizes Fe complexation, making Fe hydrolysis species available for growth and effective coagulation. Experiments were conducted to investigate the influence of aqueous silica and pH on the removal of natural organic matter (NOM) by coagulation with ferric chloride. Samples with preformed ferric hydroxide were also compared to samples coagulated in situ to assess the role of coprecipitation. The moderate (10 mg/L) and high (50 mg/L) SiO2 concentrations both demonstrated interference with NOM removal at pH 6.5-7.5. In turn, NOM at 2 mg/L as DOC interfered with silica sorption at the moderate silica level and in samples with preformed ferric hydroxide at the high silica level. The combination of NOM and high silica led to decreases in DOC sorption and unexpected increases in silica sorption in the coprecipitated samples. The fraction of colloidal Fe passing a 0.45-μm filter also increased in the coprecipitated samples with both NOM and high silica. It is hypothesized that the combination of NOM and high silica synergistically interfered with Fe precipitation and particle growth processes, with NOM having the greater effect at lower pH and shorter reaction times, and silica exerting greater influence at higher pH and longer reaction time. Direct competition for surface sites and electrostatic repulsion were also influential. An overall goal for this research was the development of a quantitative coagulation model. Previous attempts to model coagulation have been limited by the inherent complexities of simultaneously predicting ligand sorption, metal complexation, floc surface charge, and particle removal. A diffuse layer (DLM) surface complexation model was formulated to simultaneously predict sorption of NOM and other key species, including silica, calcium, and carbonate alkalinity. Predictions of surface potential were used to estimate zeta potential and resulting regimes of effective aggregation and turbidity removal. The model provided good predictive ability for data from bench-scale experiments with synthetic water and jar tests of nine U.S. source waters. Under most conditions, the model provides excellent capability for predicting NOM sorption, calcium sorption, and particle destabilization and adequate capability for predicting silica sorption. Model simulations of hypothetical scenarios and experimental results help to explain practical observations from the literature. The DLM can be optimized to site-specific conditions and expanded to include sorption of additional species, such as arsenic. / Ph. D.