Solving order constraints in logarithmic space.

We combine methods of order theory, finite model theory, and universal algebra to study, within the constraint satisfaction framework, the complexity of some well-known combinatorial problems connected with a finite poset. We identify some conditions on a poset which guarantee solvability of the problems in (deterministic, symmetric, or non-deterministic) logarithmic space. On the example of order constraints we study how a certain algebraic invariance property is related to solvability of a constraint satisfaction problem in non-deterministic logarithmic space

Variation in the dispersions of powder liquid ratios in hand-mix glass ionomers

BACKGROUND: The Powder/Liquid Ratio (PLR) influence, and the literature regarding the handling and physical properties of Glass Ionomer restorative materials (GIC) were investigated. OBJECTIVE: The objective of the study was to compare the PLR variability and magnitude in hand-mix GICs, as dispensed for clinical use. From the recorded individual powder and liquid weights, additional comparisons could be made by pairing the various “extreme” outer observations in relation to the manufacturer’s PLR. STUDY DESIGN: The materials assessed were Ketac Universal Hand-mix (KUH), Riva Self Cure Hand-mix (RSCH) and Fuji IX GP Hand-mix (FIXH). Twenty scoops of powder were paired with twenty drops of liquid, as would be the case in the clinical scenario. Statistical analysis was completed with the Kruskal Wallis H test, Intraclass Correlation (ICC) and straight line regressions with One-way ANOVA and the post-hoc Tukey HSD Test (p<0.05 was considered significant). RESULTS: The powder and liquid observations indicate a lack of consistency in both the powder and liquid dispersions. The volume remained “one drop” but the weights were much lower than the manufacturer’s recommended drop weight for some observations, due to air in the liquid drop. The Kruskal-Wallis H test indicated significant differences (p=0.0001) between the three materials for the paired PLRs. The One-way ANOVA and post-hoc Tukey HSD Test were used to compare the recommended PLR to the results and the significant differences (p<0.01). CONCLUSION: The recommended manufacturers’ powder and liquid weights were KUH 0.150/0.05g; RSC 0.165/0.035; FIXH 0.18/0.05, respectively. KUH, FIXH and RSCH liquid had powder and liquid dispersions above the manufacturer’s recommendations. FIXH had the most paired PLR observations within the ±10% range followed by KUH. Extreme powder and liquid combinations could occur in the clinical scenario and these combinations were considered

The Context of Emotional Responses to Athletic Injury: A Qualitative Analysis

This study used grounded theory to describe the emotional responses of athletes following injury and their situational and temporal contexts. Sixteen seriously injured athletes were interviewed. The NUD*IST (Nonnumerical Unstructured Data Indexing Searching and Theorizing) computer program was used to search, store, explore, and organize the qualitative material. The main emotional responses, appraisals, events, and behaviors that emerged from the analysis were represented diagrammatically. Frustration and depression were the prevalent emotional responses throughout rehabilitation, although the situational corollaries differed as recovery progressed. In the early phase of rehabilitation, frustration and depression resulted from disruption to normal function, in the middle phase they were provoked by a negative appraisal of rehabilitation progress, and. at the end of rehabilitation the main instigator was impatience to return to sport. Whether to risk returning prematurely to sport emerged as a key theme, as did the confounding effects of exercise withdrawal. symptoms in extremely committed athletes. The results were considered in terms of both cognitive appraisal and risk models