The stress relaxation process in spread dipalmitoyl phosphatidyl glycerol (DPPG) monolayers was investigated by using the pendant drop technique as a microfilm balance in combination with the axisymmetric drop shape analysis. The stress relaxation caused by a transient drop volume change was analysed by a new model, which takes into account material inhomogeneity by means of a distribution of relaxation times. The surface pressure decay in the DPPG monolayers at 35 and 40 ºC is governed by 2 main relaxation times. One is of the order of 20 s, the other one is in the range of 200-600 s. The π/A isotherms, the surface dilational modulus, and the higher relaxation times are influenced by temperature and by the presence of electrolyte in the subphase; 0.15 mol dm -3 NaCl yields a smaller area demand per molecule in the monolayer. Harmonic oscillation experiments were carried out and the dilational elasticities and viscosities were determined for different frequencies in the range between the two main relaxation times. Both the elasticities and the viscosities, depend on frequency. The surface rheological behaviour is structurally viscous, i.e. high viscosities at small frequencies, which decrease at faster deformations. The results are related to the surface dilational rheological behaviour of dipalmitoyl phosphatidyl choline (DPPC) monolayers.

Research has suggested that different strategies used when solving fraction problems are highly correlated with students' problem-solving accuracy. This study (a) utilized latent profile modeling to classify students into three different strategic developmental levels in solving fraction comparison problems and (b) accordingly provided differentiated strategic training for students starting from two different strategic developmental levels. In Study 1 we assessed 49 middle school students' performance on fraction comparison problems and categorized students into three clusters of strategic developmental clusters: a cross-multiplication cluster with the highest accuracy, a representation strategy cluster with medium accuracy, and a whole-number strategy cluster with the lowest accuracy. Based on the strategic developmental levels identified in Study 1, in Study 2 we selected three students from the whole-number strategy cluster and another three students from the representation strategy cluster and implemented a differentiated strategic training intervention within a multiple-baseline design. Results showed that both groups of students transitioned from less advanced to more advanced strategies and improved their problem-solving accuracy during the posttest, the maintenance test, and the generalization test.

No abstract

The Latinx population is the largest group of racially and ethnically diverse students in the United States. Although disproportionality in school discipline has been documented for Latinx students, findings related to such disparities have been inconsistent. We examined disciplinary exclusion practices involving students with and without disabilities who are Latinx across the United States using risk ratios (RR) and weighted mixed-effect models. We leveraged data from the Civil Rights Data Collection (CRDC) data set for the 2015 to 2016 academic school year, which included data from more than 94,000 schools. The CRDC is collected by the U.S. Department of Education’s Office of Civil Rights every 2 years. All U.S. public schools are required to submit data to the CRDC. Results suggest that Latinx students with and without disabilities were statistically significantly more likely to receive exclusionary discipline than White students, but less likely than Black students. Implications for research and practice are provided.