Microfluidic study of the chemotactic response of Escherichia coli to amino acids,signaling molecules and secondary metabolites

Quorum sensing and chemotaxis both affect bacterial behavior on the population level. Chemotaxis shapes the spatial distribution of cells, while quorum sensing realizes a cell-density dependent gene regulation. An interesting question is if these mechanisms interact on some level: Does quorum sensing, a density dependent process, affect cell density itself via chemotaxis? Since quorum sensing often spans across species, such a feedback mechanism may also exist between multiple species. We constructed a microfluidic platform to study these questions. A flow-free, stable linear chemical gradient is formed in our device within a few minutes that makes it suitable for sensitive testing of chemoeffectors: we showed that the amino acid lysine is a weak chemoattractant for Escherichia coli, while arginine is neutral. We studied the effect of quorum sensing signal molecules of Pseudomonas aeruginosa on E. coli chemotaxis. Our results show that N-(3-oxododecanoyl)-homoserine lactone (oxo-C12-HSL) and N-(butryl)-homoserine lactone (C4-HSL) are attractants. Furthermore, we tested the chemoeffector potential of pyocyanin and pyoverdine, secondary metabolites under a quorum sensing control. Pyocyanin is proved to be a weak attractant while pyoverdine are repellent. We demonstrated the usability of the device in co-culturing experiments, where we showed that various factors released by P. aeruginosa affect the dynamic spatial rearrangement of a neighboring E. coli population, while surface adhesion of the cells is also modulated.     

Judging students' achievement goal orientations: Are teacher ratings accurate?

Using the theoretical framework of achievement goal theory, this study investigated the accuracy of teachers' judgments of their students' motivation. Self-report data were gathered on the mastery, performance-approach, and performance-avoidance goals of 1140 German secondary school students (mean age = 14.24) in five academic subjects (English, Mathematics, German, second foreign language, and Biology). Their teachers in each of the five subjects (N = 176) were asked to judge students' achievement goals. Multilevel regression analyses revealed that teacher ratings of students' motivation statistically significantly predicted student ratings in all five subjects for mastery and performance-approach motivation, but not for performance-avoidance motivation. Assessment of differences in teachers' judgment accuracy across classrooms revealed some variability in teachers' ability to judge their students' mastery and performance-approach goals. Exploratory analyses showed that teaching experience, teacher gender, student age, and student gender did not systematically explain variation in judgment accuracy. Future research should examine other characteristics potentially influencing teachers' judgment accuracy and investigate the effect of teachers' judgment accuracy on students' motivation.     

A key to the future: the attitudes and values of adolescent Europeans

Based on original empirical data collected from adolescents in Europe (N = 9003) this paper focuses the lifeworlds of young people. It analyses negative and positive patterns of attitude and combines them with further concepts: personal life perspectives, various key values and political attitudes. Technically, the attitude towards Europe acts as the dependent variable whereas the remaining concepts are used as independent variables. The empirical results show Turkish and Polish adolescents are more critical towards Europe than adolescents living in ‘old’ Europe. Furthermore, the data show that those who hold negative expectations about their personal futures are likely also to be Eurosceptical.     

Syntactic complexity as a predictor of adolescent writing quality: Which measures? Which genre?

This study examined the relationship of different measures of syntactic complexity with rated quality for two genres of text produced by middle school students. It was hypothesized that different measures would be associated with distinct aspects of syntactic complexity; words per clause with greater use of structures more typical of expository texts, and clauses per T-unit with structures more typical of conversational or narrative registers. A sample of 41 seventh and eighth grade students from suburban middle schools composed a narrative and persuasive essays. Texts were rated for quality and coded for syntactic features including words per clause and clauses per T-unit. Syntactic complexity as measured in words per clause was positively correlated with quality for essays but not for narratives. Clauses per T-unit was positively correlated with quality for narratives, but negatively correlated with quality for essays. The relationships between syntactic complexity and text quality were thus found to be dependent both on the genre of the text, and the measure of syntactic complexity used.     

Can international elite sport success trickle down to mass sport participation? Evidence from Danish team handball

Many scholars do not find evidence of a trickle-down effect from elite sport success to mass sport participation. Contrary to what is assumed by the trickle-down effect “theorem”, successful elite sportspeople do not seem to inspire amateurs to take up sport themselves. However, recent studies present evidence that elite sport can have an influence. In this article, we apply regression models on time series data from one of the most successful Danish sports, team handball. Our findings are mixed, but lean towards supporting scholars who argue that trickle-down effects are not necessarily an inherent part of international sporting success. Further studies should examine more sports to identify where trickle-down effects occur and why.