Interfacial heat transfer coefficients and solidification of an aluminum alloy in a rotary continuous caster

The present study describes the development of an experimental set-up representing the metal/mold system of a rotary continuous caster as part of a methodology, which connected to a numerical heat transfer model permits to determine transient metal/mold heat transfer coefficients, h, during solidification. By using this approach the variation of h along the different mold walls and the metal surface has been investigated by a method based on numerically calculated/experimental fit of thermal profiles (IHCP). The results have shown that the used methodology permits the characterization of h and may be used in the simulation of solidification in industrial processes.     

Hydration of Nafion® studied by AFM and X-ray scattering

Nafion® is a commercially available perfluorosulphonate cation exchange membrane commonly used as a perm-selective separator in chlor-alkali electrolysers and as the electrolyte in solid polymer fuel cells. This usage arises because of its high mechanical, thermal and chemical stability coupled with its high conductivity and ionic selectivity, which depend strongly on the water content. The membrane was therefore studied in different states of hydration with two complementary techniques: atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) combined with a maximum entropy (MaxEnt) reconstruction. Tapping mode phase imaging was successfully used to identify the hydrophobic and hydrophilic regions of Nafion. The images support the MaxEnt interpretation of a cluster model of ionic aggregation, with spacings between individual clusters ranging from 3 to 5 nm, aggregating to form cluster agglomerates with sizes from 5 to 30 nm. Both techniques indicate that the number density of ionic clusters changes as a function of water content, and this explains why the bulk volumetric swelling in water is observed to be significantly less than the swelling inferred from scattering measurements.     

Meeting the Challenge of Chemical Language Barriers in University Level Chemistry Education

The specific yet varied challenges chemical language presents to students learning the subject are widely recognised. However, to effectively engage a student population becoming increasingly diverse in terms of culture, language and prior knowledge chemistry educators must develop pedagogical strategies that address issues of language comprehension. In this paper we discuss the body of literature that provides evidence of the multiple challenges that the language of chemistry presents students. These include: words in a scientific context, words with dual meaning, similar words and symbolic language. The chemistry learning triplet is used to illustrate how students must use chemical language to move between the macroscopic, sub‐microscopic and symbolic levels. Combining evidence from our research and the wider literature we describe a novel model of linguistic demand in multiple dimensions that represents the challenge of chemical language. This model can be used to assess the linguistic demand of teaching resources and to focus the appropriate use of language and literacy informed pedagogical strategies.     

Expression and immune response to foreign epitopes in bacteria. Perspectives for live vaccine development

We previously developed a general procedure which allows the genetic coupling of a chosen foreign linear epitope in different regions of a carrier protein. By using as carriers, two bacterial envelope proteins, the LamB and MalE proteins of E. coli K12, we were able to express the same epitope in different sites of the two proteins and in different compartments of the bacteria. This allowed us to analyze the influence of the localization in E. coli cells of a foreign B-cell epitope on the induction of specific antibody responses, and the role of the molecular environment on the immunological properties of foreign B- or T-cell epitopes, using either purified hybrid proteins or live recombinant bacteria. Several LamB and MalE hybrid proteins were expressed in the aroA attenuated strain of S. typhimurium, SL3261. Immunizations of mice with live recombinant bacteria by the intravenous route showed that it was possible to induce humoral responses against inserted foreign sequences. In order to improve the in vivo stability of the plasmids carrying the different contructions, and to increase the amounts of recombinant LamB and MalE hybrid proteins expressed in vivo, the LamB and malE genes were placed under the control of the anaerobically inducible pnirBpromoter control. The genetic factors susceptible of influencing the immune response to recombinant Salmonella in mice were also studied.