A Mini Look at Some Maxi Ideas

Time and again I have listened to busy teachers complaining that they don\u27t have time to read the many current articles on IQ, open classrooms, class organization, learning theory, motivation, and use of traditional material which appear in professional literature. Therefore, I would like to consolidate many of these sources into one article which will give the reader some indication of the trends which seem to be taking place concerning these things

Interactions of diploid embryonal carcinoma cells and normal cell mass cells with 2.5 day mouse embryos following aggregation

Spontaneous teratocarcinomas are ovarian or testicular tumors which have their origins in germ cells. The tumors contain a disorganized array of benign differentiated cells as well as an undifferentiated population of malignant stem cells, the embryonal carcinoma or EC cells. These pluripotent stem cells in tissue culture share many properties with the transient pluripotent cells of the early embryo, and might therefore serve as models for the investigation of developmental events ill vitro. The property of EC cells of prime interest in this study is an in vivo phenomenon. Certain EC cell lines are known to be regulated ill vivo and to differentiate normally in association with normal embryonic cells, resulting in chimeric mice. These mice have two genetically distinct cell populations, one of which is derived from the originally malignant EC cells. This has usually been accomplished by injection of the EC cells into the Day 3 blastocyst. In this study, the interactions between earlier stage embryos and EC cells have been tested by aggregating clumps of EC cells with Day 2 embryos. The few previous aggregation studies produced a high degree of abnormality in chimeric embryos, but the EC cells employed had known chromosomal abnormalities. In this study, two diploid EC cell lines (P19 and Pi0) were aggregated with 2.5 day mouse embryos, and were found to behave quite differently in the embryonic environment. P19 containing aggregates generally resorbed early, and the few embryos recovered at midgestation were normal and non-chimeric. Pi0 containing aggregates survived in high numbers to midgestation, and the Pi0 cells were very successful in colonizing the embryo. All these embryos were chimeric, and the contribution by the EC cells to each chimera was very high. However, these heavily chimeric embryos were all abnormal. Blastocyst injection had previously produced some abnormal embryos with high Pl0 contributions in addition to the live born mice, which had lower EC contributions. This study now adds more support to the hypothesis that high EC contributions may be incompatible with normal development. The possibility that the abnormalities were due to the mixing of temporally asynchronous embryonic cell types in the aggregates was tested by aggregating normal pluripotent cells taken from 3.5 day embryos with 2.5 day embryos. Early embryo loss was very high, and histological studies showed that the majority of these embryos died by 6.5 days development. Some embryos escaped this early death such that some healthy chimeras were recovered, in contrast to recovery of abnormal chimeric embryos following Pl0-morula aggregations, and non-chimeric embryos following P19-morula aggregations. This somewhat surprising adverse effect on development following aggregation of normal cell types suggests that there are developmental difficulties associated with the mixing of asynchronous cell types in aggregates. However, the greater magnitude of the adverse effects when the aggregates contained tumor derived cells suggests that EC cells should not be considered the complete equivalent of the pluripotent cells of the early embryo

A Novel Form of Product Placement? The Use of Fashion Brand Names in British Chick Lit

Several studies have noted the frequent use of fashion brand names in contemporary fiction, but to date there has been little academic research into this phenomenon and the effect that it has on the reader. This study therefore set out to address this research gap. Focusing specifically on chick lit (a type of contemporary popular fiction, typically featuring and aimed at young women), the present study aimed to explore the use of fashion brand names in women’s fiction, concentrating on the relationships between fashion brands, authors, fictitious characters and readers, with a view to establishing whether there might be potential commercial benefits of fashion brand product placement in chick lit novels. A mixed methods approach was used to explore the topic from multiple perspectives. A summative content analysis was undertaken to investigate the frequency, variety and types of fashion brand names used in a corpus of 19 chick lit novels drawn from the Bridget Jones, Shopaholic and I Heart series. A qualitative analysis of the novels in the corpus focused on the ways in which the characters interacted with fashion brands in the text. An online survey of 166 chick lit authors was used to explore why writers use fashion brand names in their work, and a survey of 96 female students was used to investigate readers’ response to fashion brand names in novels. The study findings indicated that chick lit authors use fashion brand names to support characterisation due to the ability of fashion brands to express the values, self-concepts and stereotypes of their typical brand users. The outcomes of the consumer survey suggested that readers use textual cues, including those related to fashion consumption, to help them to develop their impressions of characters in novels, however the study was unable to demonstrate a clear relationship between readers’ perceptions of character personality and brand personality. In terms of product placement, the findings confirmed that readers demonstrated high levels of recall and recognition of fashion brand names used in chick lit narratives, but no evidence was found to indicate that the appearance of brand names in the text had an impact on consumers’ brand attitudes. Readers were found to be broadly positive about the use of brand names in novels, indicating that they preferred to see real brands, rather than fictional brands, in books. Readers appeared to have no significant objection to commercial product placement in fiction books, provided that such placements were accompanied by a disclosure. The results of the study therefore provide support for the proposal that chick lit novels are a potential product placement medium for fashion brands seeking to generate brand awareness. The frequent mentions and positive treatment of fashion brand names in chick lit mean that it would be relatively easy to incorporate paid-for placements of fashion brands in chick lit novels without compromising the narrative

The Dynamics of a Collapsing Polyelectrolyte Gel

We analyse the dynamics of different routes to collapse of a constrained polyelectrolyte gel in contact with an ionic bath. The evolution of the gel is described by a model that incorporates non-linear elasticity, Stefan-Maxwell diffusion and interfacial gradient free energy to account for phase separation of the gel. A bifurcation analysis of the homogeneous equilibrium states reveals three solution branches at low ion concentrations in the bath, giving way to only one above a critical ion concentration. We present numerical solutions that capture both the spatial heterogeneity and the multiple timescales involved in the process of collapse. These solutions are complemented by two analytical studies. Firstly, a phase-plane analysis that reveals the existence of a depletion front for the transition from the highly swollen to the new collapsed equilibrium state. This depletion front is initiated after the fast ionic diffusion has set the initial condition for this time regime. Secondly, we perform a linear stability analysis about the homogeneous states that show that for a range of ion concentrations in the bath, spinodal decomposition of the swollen state gives rise to localized solvent-rich(poor) and, due to the electroneutrality condition, ion-poor(rich) phases that coarsen on the route to collapse. This dynamics of a collapsing polyelectrolyte gel has not been described before

Asymptotic study of the electric double layer at the interface of a polyelectrolyte gel and solvent bath

An asymptotic framework is developed to study electric double layers that form at the inter-face between a solvent bath and a polyelectrolyte gel that can undergo phase separation. The kinetic model for the gel accounts for the finite strain of polyelectrolyte chains, free energy ofinternal interfaces, and Stefan?Maxwell diffusion. By assuming that the thickness of the doublelayer is small compared to the typical size of the gel, matched asymptotic expansions are used toderive electroneutral models with consistent jump conditions across the gel-bath interface in two-dimensional plane-strain as well as fully three-dimensional settings. The asymptotic frameworkis then applied to cylindrical gels that undergo volume phase transitions. The analysis indicatesthat Maxwell stresses are responsible for generating large compressive hoop stresses in the double layer of the gel when it is in the collapsed state, potentially leading to localised mechanicalinstabilities that cannot occur when the gel is in the swollen state. When the energy cost of in-ternal interfaces is sufficiently weak, a sharp transition between electrically neutral and chargedregions of the gel can occur. This transition truncates the double layer and causes it to have finitethickness. Moreover, phase separation within the double layer can occur. Both of these featuresare suppressed if the energy cost of internal interfaces is sufficiently high. Thus, interfacial freeenergy plays a critical role in controlling the structure of the double layer in the gel

Spinodal decomposition and collapse of a polyelectrolyte gel

The collapse of a polyelectrolyte gel in a (monovalent) salt solution is analysed using a new model that includes interfacial gradient energy to account for phase separation in the gel, finite elasticity and multicomponent transport. We carry out a linear stability analysis to determine the stable and unstable spatially homogeneous equilibrium states and how they phase separate into localized regions that eventually coarsen to a new stable state. We then investigate the problem of a collapsing gel as a response to increasing the salt concentration in the bath. A phase space analysis reveals that the collapse is obtained by a front moving through the gel that eventually ends in a new stable equilibrium. For some parameter ranges, these two routes to gel shrinking occur together

Breakdown of electroneutrality in polyelectrolyte gels

Mathematical models of polyelectrolyte gels are often simplified by assuming the gel is electrically neutral. The rationale behind this assumption is that the thickness of the electric double layer (EDL) at the free surface of the gel is small compared to the size of the gel. Hence, the thin-EDL limit is taken, in which the thickness of the EDL is set to zero. Despite the widespread use of the thin-EDL limit, the solutions in the EDL are rarely computed and shown to match to the solutions for the electrically neutral bulk. The aims of this paper are to study the structure of the EDL and establish the validity of the thin-EDL limit. The model for the gel accounts for phase separation, which gives rise to diffuse interfaces with a thickness described by the Kuhn length. We show that the solutions in the EDL can only be asymptotically matched to the solutions for an electrically neutral bulk, in general, when the Debye length is much smaller than the Kuhn length. If the Debye length is similar to or larger than the Kuhn length, then phase separation can be initiated in the EDL. This phase separation spreads into the bulk of the gel and gives rise to electrically charged layers with different degrees of swelling. Thus, the thin-EDL limit and the assumption of electroneutrality only generally apply when the Debye length is much smaller than the Kuhn length