Browsing by Subject "Fluctuations"
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Item Computational modeling of fluctuations and phase behavior in polymeric systems(2015-08) Pandav, Gunja Rajesh; Ganesan, Venkat; Ellison, Christopher; Sanchez, Isaac; Truskett, Thomas; Henkelman, Graeme; Johnston, KeithThis research focuses on the computational modeling of fluctuations, interactions, phase behavior and structural characteristics of multicomponent polymeric systems. The role of fluctuations is studied in the context of block copolymer melts and polymer blends stabilized using copolymers exhibiting different sequence architectures. The relationship between interparticle interactions and structural characteristics of the aggregates formed in particle-polymer solutions is examined for charged nanoparticle-polymer and charged dendrimer-polyelectrolyte system. A hybrid Monte Carlo and self consistent field theory approach employed in single chain in mean field simulations (SCMF) is utilized in order to achieve the equilibrium morphologies/aggregates in such polymeric systems. We examine the effect of composition fluctuations on the phase behavior of polydisperse block copolymer melts quantified in terms of fluctuation-induced shift in the order-disorder transition temperature from the corresponding mean-field predictions. Fluctuation effects can also play an important role in stabilizing bicontinuous microemulsions phases. To study this effect, we examine polymer blend systems compatibilized by a copolymer having different sequence architectures such as monodisperse and polydisperse block copolymer, and gradient copolymer. We systematically assess the efficiency of such system in forming bicontinuous microemulsions phases. We also study the effect of sequence architecture on the phase behavior of gradient copolymer solutions. We extend above framework to account for electrostatic effects arising from charged polymers and dendrimers. Using such a framework, we characterize the clusters formed due to electrostatic binding between oppositely charged dendrimers and polyelectrolytes. Our results indicate that, the binding is maximum when the charge on dendrimers is balanced by the charge on the polyelectrolytes. We extend the above study to probe the phase behavior of charged nanoparticles suspended in polymer solutions. We examine the influence of polymer concentration, particle volume fraction, and particle charge on the structure and size of clusters. We also examine the influence of multibody effects on the resulting structure of nanoparticle clusters. The charged nanoparticle-polymer solution is seen to exhibit significant multibody effects and the effective two-body interparticle potentials are seen to be a function of nanoparticle density.Item The ups and downs of variability : are fluctuating relationship appraisals always detrimental for long-term relationship outcomes?(2013-12) Morgan, Taylor Anne; Neff, Lisa A.Variability in daily relationship satisfaction has been shown to undermine future relationship well-being. The current study suggests that the relationship climate may moderate this effect. Namely, and in light of prior work showing that ignoring relationship issues can be detrimental for long-term relationship well-being, it is argued that when the relationship is characterized by more negative relationship experiences, variability in daily satisfaction may actually represent an adaptive acknowledgement of those experiences. Seventy-eight newly-married couples completed a 10-day daily diary task which assessed the variability of daily marital satisfaction, the positive and negative marital events taking place each day, and the daily coping strategies used to manage negative marital events. Spouses then reported on their global marital happiness as well as the severity of their marital problems every six months over the first two and a half years of marriage. Results revealed that when the marriage was characterized by more negative than positive marital events (i.e., a more negative marital climate), greater variability in daily satisfaction predicted initially lower levels of global marital happiness and more severe marital problems. However, greater variability in a more negative marital climate also was associated with less steep declines in global marital happiness and fewer increases in marital problems over time compared to low variability. Together, these findings suggest that variability in daily relationship satisfaction may temporarily feel unpleasant but over time may allow couples to address important relationship issues.Item Variability of relationship evaluations & physical health outcomes : testing the moderating role of implicit theories of relationships(2015-08) Morgan, Taylor Anne; Loving, Timothy J.; Neff, Lisa A.; Gleason, Marci E.; Anderson, Edward R.; Campbell, LorneVariability (i.e., greater fluctuations) of relationship evaluations over time undermines current and future relationship and individual well-being. To date, greater variability of relationship evaluations has not been linked to individual physical health, yet overall relationship quality (e.g., initial or mean levels) is a strong predictor of several markers of physical health. The aims of the current study are three-fold--first, to explore new methods of capturing intra-individual variability; second, to replicate and extend previous findings on the damaging effects of variability by examining variability's association with relationship fate and physical health outcomes; and third, to investigate the potential moderating role of individuals' general relationship beliefs on these associations. I drew from a 9-month longitudinal study of 202 individuals who were in new dating relationships at the start of study participation (M[subscript length] = 3.28 months). The study included baseline self-reports of relationship satisfaction and Implicit Theories of Relationships (ITRs) as well as bi-weekly self-reports, for a total of up to 20 assessments per individual, of relationship status (together or not) and quality (semantic differential) and physical health (shortened SF-36). A series of analyses were conducted to obtain de-trended levels of intra-individual variability and a previously understudied measure of intra-individual change in relationship evaluations over time -- temporal dependency (i.e., the extent to which one day's relationship evaluation is correlated with the previous day's evaluation). These two variables were subsequently entered into a Cox proportional hazards model to explain the effect of each on the likelihood of relationship dissolution. Both variability and temporal dependency of relationship evaluations (but not their interaction) predicted increased likelihood of experiencing relationship dissolution. Contrary to predictions, however, greater variability and temporal dependency (and their interaction) were not associated with changes in self-reported physical health over time; all three terms, however, predicted higher levels of average self-reported physical health across assessments. Finally, the hypothesized moderating effects of individuals' implicit theories of relationships were not supported. These findings emphasize the predictive power of individuals' patterns of relationship evaluations over time for relationship fate yet suggest additional research is needed to understand the association between variable relationship evaluations and health outcomes.