Interplay between motility and cell-substratum adhesion in amoeboid cells

The effective migration of amoeboid cells requires a fine regulation of cell-substratum adhesion. These entwined processes have been shown to be regulated by a host of biophysical and biochemical cues. Here, we reveal the pivotal role played by calcium-based mechanosensation in the active regulation of adhesion resulting in a high migratory adaptability. Using mechanotactically driven Dictyostelium discoideum amoebae, we uncover the existence of optimal mechanosensitive conditions—corresponding to specific levels of extracellular calcium—for persistent directional migration over physicochemically different substrates. When these optimal mechanosensitive conditions are met, noticeable enhancement in cell migration directionality and speed is achieved, yet with significant differences among the different substrates. In the same narrow range of calcium concentrations that yields optimal cellular mechanosensory activity, we uncovered an absolute minimum in cell-substratum adhesion activity, for all considered substrates, with differences in adhesion strength among them amplified. The blocking of the mechanosensitive ion channels with gadolinium—i.e., the inhibition of the primary mechanosensory apparatus—hampers the active reduction in substrate adhesion, thereby leading to the same undifferentiated and drastically reduced directed migratory response. The adaptive behavioral responses of Dictyostelium cells sensitive to substrates with varying physicochemical properties suggest the possibility of novel surface analyses based on the mechanobiological ability of mechanosensitive and guidable cells to probe substrates at the nanometer-to-micrometer level.     

An empirical investigation of Web session workloads: Can self-similarity be explained by deterministic chaos?

Several studies of Web server workloads have hypothesized that these workloads are self-similar. The explanation commonly advanced for this phenomenon is that the distribution of Web server requests may be heavy-tailed. However, there is another possible explanation: self-similarity can also arise from deterministic, chaotic processes. To our knowledge, this possibility has not previously been investigated, and so existing studies on Web workloads lack an adequate comparison against this alternative. We conduct an empirical study of workloads from two different Web sites: one public university, and one private company, using the largest datasets that have been described in the literature. Our study employs methods from nonlinear time series analysis to search for chaotic behavior in the web logs of these two sites. While we do find that the deterministic components (i.e. the well-known “weekend effect”) are significant components in these time series, we do not find evidence of chaotic behavior. Predictive modeling experiments contrasting heavy-tailed with deterministic models showed that both approaches were equally effective in modeling our datasets.     

Modified breastfeeding attrition prediction tool: prenatal and postpartum tests

In earlier studies, the Breastfeeding Attrition Prediction Tool (BAPT) demonstrated predictive validity in the postpartum period. The purpose of this study was to compare the effectiveness of a modified version of the BAPT when given in the last trimester (BAPT1) and following delivery (BAPT2) in predicting breastfeeding attrition among 117 women who planned to breastfeed for at least 8 weeks. Subjects completed the BAPT during a prenatal breastfeeding class and again at delivery, and they received a phone call at 8 weeks to determine breastfeeding status. In this study, neither of the two administrations of the BAPT was predictive of breastfeeding status at 8 weeks. Findings here may differ because subjects in the current study were all committed enough to attend breastfeeding class and, thus, varied less on commitment than women in earlier studies. Significant associations were found with level of education and having a close relative who breastfed. To assist the perinatal educator in identifying women most at risk for early cessation of breastfeeding, the use of three questions regarding level of education, family support, and breastfeeding preparation is suggested.     

Colonial legacies and neo‐colonial practices in Papua New Guinean higher education

This paper explores the Westernization of academic quality within the Papua New Guinea higher education system and the hybridity of the university sector where different actors force knowledge to be created for the needs of a small, formal economy, rather than for the development needs of the country. The country has yet to find a system that best responds to its educational needs; several models have been put into practice but without significant results. The approach that the PNG higher education institutes have taken, continuing the colonial tradition, builds on and is reinforced by the new international trends in higher education that follow the market needs, giving a false guarantee that HE is contributing to the economic growth of the country. Colonial legacies and neo‐colonial practices provide the conceptual framework.     

Rethinking Intensive Quantities via Guided Mediated Abduction

Some intensive quantities, such as slope, velocity, or likelihood, are perceptually privileged in the sense that they are experienced as holistic, irreducible sensations. However, the formal expression of these quantities uses a/b analytic metrics; for example, the slope of a line is the quotient of its rise and run. Thus, whereas students' sensation of an intensive quantity could serve as a powerful resource for grounding its formal expression, accepting the mathematical form requires students to align the sensation with a new way of reasoning about the phenomenon. I offer a case analysis of a middle school student who successfully came to understand the intensive quantity of likelihood. The analysis highlights a form of reasoning called abduction and suggests that sociocognitive processes can guide and mediate students' abductive reasoning. Interpreting the child's and tutor's multimodal action through the lens of abductive inference, I demonstrate the emergence of a proportional concept as guided mediated objectification of tacit perception. This “gestalt first” process is contrasted with traditional “elements first” approaches to building proportional concepts, and I speculate on epistemic and cognitive implications of this contrast for the design and instruction of these important concepts. In particular, my approach highlights an important source of epistemic difficulty for students as they learn intensive quantities: the difficulty in shifting from intuitive perceptual conviction to mediated disciplinary analysis. My proposed conceptualization of learning can serve as an effective synthesis of traditional and reform-based mathematics instruction.     

Broadcasting

Jack Lyle's The People Look at Public Television: 1974 (Washington: Corporation for Public Broadcasting, 1975—$1.00, paper)

Ken Coleman's So You Want to be a Sportscaster (New York: Hawthron Books, 1973—$5.95)

Joseph Fletcher Littell (ed.) Coping with Television (Evanston, Ill.: McDougal, Littell, 1973— cost not given, paper)

Joseph Julian's This Was Radio: A Personal Memoir (New York: Viking, 1975—$8.85)

Dick Cavett and Christopher Porterfield's Cavett (New York: Harcourt, Brace Jevanovich, 1974—$8.95)     

Intended and unintended consequences of student use of an online questioning environment

While supplementation of face‐to‐face (F2F) teaching with online engagement is increasingly common, the educators' challenge of teaching F2F personalities and facilitating online personalities has not been widely explored. In this paper, we report on a project in which 1st‐year students attended F2F sessions and engaged with an anonymous online questioning environment. The differences between students' F2F and online behaviour led to intended and unintended consequences. The purpose of this paper is to explore these intended and unintended consequences of technology use. The project was undertaken over a 3‐year period, starting in 2004. In 2004, a pilot project was conducted based on a class of 35 students studying a 1st‐year programming course in information systems. The investigation was again conducted in 2005 for the same course, this time with 63 students. In 2006, the project was extended to a class of 610 1st‐year commerce students studying an introductory information systems course. In all cases, students met F2F and when online, engaged with an anonymous Web/SMS collaborative tool. The intended consequence was that a blending of F2F with online interaction extended student engagement beyond the limitation of a classroom and provided a forum for further collaboration and consultation. The intended outcome was achieved. An unintended consequence was that the tool provided the lecturer with diagnostic information that was used to impact on pedagogical designs. This was often a result of students taking on an online personality that would very often be extremely frank and honest about the manner in which the course was conducted, and how learning was taking place. The findings show that students used the tool in ways that exceeded the envisaged intention, and student use of the tool positively impacted on the curriculum, pedagogy and general running of the course. The paper concludes that integration of online engagement with F2F teaching adds value to the teaching and learning experience.