Browsing by Subject "solubility"

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    Evaluation of water sorption and solubility behavior of nine different polymeric luting materials
    (2009) Alsheikh, Rasha N.; Platt, Jeffrey A.; Lund, Melvin R., 1922-; Cochran, Michael A. (Michael Alan), 1944-; Moore, B. Keith; Matis, Bruce A.
    The cementation procedure is the key to long-term success of fixed restorations. The prognosis of prosthetic restoration is largely impacted by the maintenance of the luting cement and the adhesive bond. When exposed to water or saliva, most restorative materials undergo hydrolytic degradation. The purpose of this study is to evaluate the water solubility and water sorption characteristics of newly introduced acidic polymeric luting agents over a 180-day water-storage period. Nine different luting agents were tested. Fifty-two disc specimens of each material were fabricated using a mold with an internal dimension of 15[plus-minus]0.1 mm in diameter and 1.0 [plus-minus]0.1 mm deep. A constant weight, W0 [subscript zero], was reached after desiccating the specimens. Then, 13 specimens were assigned randomly to one of the four testing periods in the water for seven, 30, 90 and 180 days. After each period, the specimens were removed from the water and weighed to get W1 [subscript one]. A second period of desiccating the samples provided a constant weight W2 [subscript two]. The water sorption and solubility were determined by the following equations: WSP [subscript SP](%) = (W1 [subscript one] W2 [subscript two] ) X 100/ W0 [subscript zero] ,WSL [subscript SL](%) = (W0 [subscript zero] W2 [subscript two) X 100/ W0 [subscript zero]. The resin-modified glass-ionomers showed the highest water sorption/solubility results. The resin luting agents had the lowest sorption/solubility results. The self-adhesives showed a wide range of solubility/sorption; in general, they showed lower results compared with the resin-modified glass-ionomers. All the materials reached some sort of equilibrium after 90-days. Based on the results of our study, we conclude that self-adhesive luting materials were not all alike. Rely X Unicem was the most comparable to the resin luting materials. The resin luting materials had the lowest solubility and sorption. Resin-modified glass-ionomers showed the highest sorption/solubility results.
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    A meta-analysis of pesticide loss in runoff under conventional tillage and no-till management
    (Springer, 2018-02) Elias, Daniel; Wang, Lixin; Jacinthe, Pierre-Andre; Earth Sciences, School of Science
    Global agricultural intensification has led to increased pesticide use (37-fold from 1960 to 2005) and soil erosion (14% since 2000). Conservation tillage, including no-till (NT), has been proposed as an alternative to conventional plow till (PT) to mitigate soil erosion, but past studies have reported mixed results on the effect of conservation tillage on pesticide loss. To explore the underlying factors of these differences, a meta-analysis was conducted using published data on pesticide concentration and load in agricultural runoff from NT and PT fields. Peer-reviewed articles (1985–2016) were compiled to build a database for analysis. Contrary to expectations, results showed greater concentration of atrazine, cyanazine, dicamba, and simazine in runoff from NT than PT fields. Further, we observed greater load of dicamba and metribuzin, but reduced load of alachlor from NT fields. Overall, the concentration and the load of pesticides were greater in runoff from NT fields, especially pesticides with high solubility and low affinity for solids. Thus, NT farming affects soil properties that control pesticide retention and interactions with soils, and ultimately their mobility in the environment. Future research is needed for a more complete understanding of pesticide-soil interactions in NT systems. This research could inform the selection of pesticides by farmers and improve the predictive power of pesticide transport models.