The combination of self-setting and biocompatibility makes calcium phosphate cements potentially useful materials for a variety of dental applications. The objective of this study was to investigate the setting and hardening mechanisms of a cement-type reaction leading to the formation of calcium-deficient hydroxyapatite at low temperature. Reactants used were a-tricalcium phosphate containing 17 wt% β-tricalcium phosphate, and 2 wt% of precipitated hydroxyapatite as solid phase and an aqueous solution 2.5 wt% of disodium hydrogen phosphate as liquid phase. The transformation of the mixture was stopped at selected times by a freeze-drying technique, so that the cement properties at various stages could be studied by means of x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. Also, the compressive strength of the cement was measured as a function of time. The results showed that: (1) the cement setting was the result of the a-tricalcium phosphate hydrolysis, giving as a product calcium-deficient hydroxyapatite, while β-tricalcium phosphate did not participate in the reaction; (2) the extent of conversion of a-TCP was nearly 80% after 24 hr; (3) both the extent of conversion and the compressive strength increased initially linearly with time, subsequently reaching a saturation level, with a strong correlation observed between them, indicating that the microstructural changes taking place as the setting reaction proceeded were responsible for the mechanical behavior of the cement; and (4) the microstructure of the set cement consisted of clusters of big plates with radial or parallel orientations in a matrix of small plate-like crystals.

Setting aside experimental costs, the choice of an experiment is usually formulated in terms of the maximization of a measure of information, often presented as an optimality design criterion. However, there does not seem to be a universal agreement on what objects can qualify as a valid measure of the information in an experiment. In this article we explicitly state a minimal set of requirements that must be satisfied by all such measures. Under that framework, the measure of the information in an experiment is equivalent to the measure of the variability of its likelihood ratio statistics or which is the same, it is equivalent to the measure of the variability of its posterior to prior ratio statistics and to the measure of the variability of the distribution of the posterior distributions yielded by it. The larger that variability, the more peaked the likelihood functions and posterior distributions that tend to be yielded by the experiment, and the more informative the experiment is. By going through various measures of variability, this paper uncovers the unifying link underlying well known information measures as well as information measures that are not yet recognized as such. The measure of the information in an experiment is then related to the measure of the information in a given observation from it. In this framework, the choice of experiment based on statistical merit only, is posed as a decision problem where the reward is a likelihood ratio or posterior distribution, the utility function is convex, the utility of the reward is the information observed, and the expected utility is the information in an experiment. Finally, the information in an experiment is linked to the information and to the uncertainty in a probability distribution, and we find that the measure of the information in an experiment is not always interpretable as the uncertainty in the prior minus the expected uncertainty in the posterior.

Objective: To assess whether alcohol intake is associated with the onset of migraine attacks up to 2 days after consumption in individuals with episodic migraine (EM). Background: Although alcohol has long been suspected to be a common migraine trigger, studies have been inconclusive in proving this association. Methods: This was an observational prospective cohort study among individuals with migraine who registered to use a digital health platform for headache. Eligible individuals were aged ≥18 years with EM who consumed alcohol and had tracked their headache symptoms and alcohol intake for ≥90 days. People who did not drink any alcohol were excluded. The association of alcohol intake (“Yes/No”) and of the number of alcoholic beverages in the 2 days preceding a migraine attack was assessed accounting for the presence of migraine on day‐2 and its interaction with alcohol intake on day‐2, and further adjusted for sex, age, and average weekly alcohol intake. Results: Data on 487 individuals reporting 5913 migraine attacks and a total of 40,165 diary days were included in the analysis. Presence of migraine on day‐2 and its interaction with alcohol intake on day‐2 were not significant and removed from the model. At the population level, alcohol intake on day‐2 was associated with a lower probability of migraine attack (OR [95% CI] = 0.75 [0.68, 0.82]; event rate 1006/4679, 21.5%), while the effect of alcohol intake on day‐1 was not significant (OR [95% CI] = 1.01 [0.91, 1.11]; event rate 1163/4679, 24.9%) after adjusting for sex, age, and average weekly alcohol intake. Similar results were obtained with the number of beverages as exposure. Conclusions: In this English‐speaking cohort of individuals with EM who identified themselves as mostly low‐dose alcohol consumers, there was no significant effect on the probability of a migraine attack in the 24 h following consumption, and a slightly lower likelihood of a migraine attack from 24 to 48 h following use.