The Influence of Chemical Structure of Model Epoxy Networks on Chemical Resistance

Structural differences in cross-linked epoxy networks from the use of different isomers (ortho-, meta- and para-) of disubstituted aromatic diglycidyl ethers can have a dramatic effect on the polymer properties. By changing the disubstitution from meta- to para- it has been shown that there is a direct correlation between the diffusion of gasses and the symmetry of related polymers. The aim of this work is to investigate the influence of the chemical structure of aromatic diglycidyl ethers on the ability of the resulting amine-cured epoxy polymer networks to adsorb organic solvents. Pure diglycidyl ethers based on hydroquinone and catechol, have been synthesised in high purity and good yields using a process previously developed at Durham University which utilise elemental fluorine to produce hypofluorous acid. The diglycidyl ether of resorcinol is commercially available and readily purified via vacuum distillation. Using the pure epoxides model networks have been produced by reacting the diglycidyl ethers with the diamine 4,4’-methylenebis(cyclohexylamine) to produce highly cross-linked films. Analytical techniques including DSC, DMTA, TGA, FTIR, solid state NMR, thermodynamic testing, PALs and density measurements have been used to investigate the influence of polymer structure on the network properties. With these materials we are determining the effect of the different epoxide isomers on the chemical resistance of the polymers. The results obtained for the polymers shows consistency with those suggested by the literature which is that the meta- polymer has the best chemical resistance with the other isomers having similar results

Aspects of late iron age and Romano-British settlement in the lower Hull valley

The lower Hull valley is an extensive tract of estuarine alluvium between Kingston upon Hull and Beverley, North Humberside. The thesis examines the evidence for later Iron Age and Romano-British settlement in a landscape block of c. 330 km(^2), incorporating the valley proper and the higher glacial deposits at its margins. The discussion utilises a comprehensive and critical gazetteer of some two hundred and twenty sites and findspots, and seven detailed site-studies present the results of the author’s fieldwork or analysis of previously unpublished material assemblages. The sites are located on both alluvial and glacial deposits, and are presented in the context of their environmental settings. Activity on the valley margins before the end of the Arras burial tradition is evidenced by aerial photography and by the beginning of the first millennium A.D. there were settlements on the clay/alluvium interface at sites such as Salthouse High School, Hull, and Chapel Farm, Weel. Acculturation from south of the Humber is suggested by the use of wheelthrown cordoned pottery at Risby, a site which may have developed into a villa and which remained in occupation until the late fourth century. Settlement on the alluvium deposit itself, hitherto held to have been a tidal inlet of the Humber until the early Middle Ages, can now be demonstrated at riparian sites such as Greylees Avenue, Hull, throughout the Roman period. A substantial body of Roman finds from the alluvium has been revealed by recent fieldwork and database research, and is analysed in the light of the valley’s geomorphology and the lower Mean Sea Level which then obtained and for which a value is postulated

Interpreting Metaphor: Perspectives from Pragmatics & Psychotherapy

The primary objective of this thesis is to provide an account of metaphor comprehension that applies to the full spectrum of metaphorical utterances. I take the relevance-theoretic account of communication, and its entailed theory of metaphor, to provide a good account of how many metaphorical expressions are comprehended, in particular lexical/phrasal cases. However, I maintain the need for a different processing route to account for instances of metaphor interpretation in which the literal meaning of the metaphorical utterance is more keenly felt and experienced by the interpreter. As I demonstrate, this applies to cases of extended and/or creative metaphorical utterances. The additional processing route described, referred to as the ‘metaphorical/imaginary world’ route, is argued to be complementary to the relevance-theoretic ad hoc concept account and is, therefore, framed against the backdrop of RT’s general theory of communication. In order to incorporate the perspective-shifting and imagistic effects that I show to be derived during ‘metaphorical world’ comprehension, I suggest enriching the relevance-theoretic notion of ‘encyclopaedic entry’ to encompass affective and imagistic content. This work takes its cue from recent research in the field of embodied simulation. In my attempt to offer support for the existence of the metaphorical world mode of understanding, I present two empirical investigations designed to test its claims. In addition, I provide extensive analysis of metaphorical expressions that occur in the context of psychotherapeutic discourse. I argue that this unique communicative context lends itself to the metaphorical world processing route in so much as it creates a reflective space that invites both client and therapist to deeply consider and sustain the literal meanings of their metaphorical expressions. While my main goal is to inform pragmatic theories of metaphor comprehension, this endeavour also serves therapeutic ends, by informing the theoretical underpinnings concerning the use of metaphor in psychotherapy

Fully biodegradable and biocompatible emulsion template polymer scaffolds by thiol-acrylate polymerisation of polycaprolactone macropolymers

The emulsion templating process offers a route to highly porous polymers with well-defined morphologies. This study describes the preparation of such porous polymers (polyHIPEs) via the photopolymerization of a multi-functional thiol and polycaprolactone macromonomer. The resulting materials have nominal porosities of 90% and 95%, and are seen to have an interconnected pore morphology, with an average pore diameter of approximately 60 μm. Initial biocompatibility assessments with fibroblast cells (L929) have shown that the polymers are capable of supporting cell growth over 7 days and degradation products are non-toxic to cells up to a concentration of 0.1 mg ml−1

Degradable emulsion-templated scaffolds for tissue engineering from thiol– ene photopolymerisation

Emulsion templating has been used to prepare highly porous polyHIPE materials by thiol–ene photoinitiated network formation. Commercially available multifunctional thiols and acrylates were formulated into water-in-oil high internal phase emulsions (HIPEs) using an appropriate surfactant, and the HIPEs were photo-cured. The temperature of the HIPE aqueous phase was found to influence the morphology of the resulting materials. In agreement with previous work, a higher aqueous phase temperature (80 °C) gave rise to a larger mean void and interconnect diameter. The influence of temperature on morphology was found to be reduced at higher porosity, but still significant. The Young's modulus of the porous materials was shown to be related to the functionality of the acrylate comonomer used. A mixture of penta- and hexa-acrylate gave rise to a 100-fold increase in modulus, compared to an analogous tri-functional acrylate. The materials could be functionalised conveniently by addition of mono-acrylates or thiols to the organic phase of the precursor HIPE. Degradation was observed to occur at a rate depending on the degradation conditions. Under cell culture conditions at 37 °C, 19% mass loss occurred over 15 weeks. The scaffolds were found to be capable of supporting the growth of keratinocytic cells (HaCaTs) over 11 days in culture. Some penetrative in-growth of the cells into the scaffold was observed

Rotavirus NSP4 is secreted from infected cells as an oligomeric lipoprotein and binds to glycosaminoglycans on the surface of non-infected cells

<p>Abstract</p> <p>Background</p> <p>Nonstructural glycoprotein 4 (NSP4) encoded by rotavirus is the only viral protein currently believed to function as an enterotoxin. NSP4 is synthesized as an intracellular transmembrane glycoprotein and as such is essential for virus assembly. Infection of polarized Caco-2 cells with rotavirus also results in the secretion of glycosylated NSP4 apparently in a soluble form despite retention of its transmembrane domain. We have examined the structure, solubility and cell-binding properties of this secreted form of NSP4 to further understand the biochemical basis for its enterotoxic function. We show here that NSP4 is secreted as discrete detergent-sensitive oligomers in a complex with phospholipids and demonstrate that this secreted form of NSP4 can bind to glycosaminoglycans present on the surface of a range of different cell types.</p> <p>Methods</p> <p>NSP4 was purified from the medium of infected cells after ultracentrifugation and ultrafiltration by successive lectin-affinity and ion exchange chromatography. Oligomerisation of NSP4 was examined by density gradient centrifugation and chemical crosslinking and the lipid content was assessed by analytical thin layer chromatography and flame ionization detection. Binding of NSP4 to various cell lines was measured using a flow cytometric-based assay.</p> <p>Results</p> <p>Secreted NSP4 formed oligomers that contained phospholipid but dissociated to a dimeric species in the presence of non-ionic detergent. The purified glycoprotein binds to the surface of various non-infected cells of distinct lineage. Binding of NSP4 to HT-29, a cell line of intestinal origin, is saturable and independent of divalent cations. Complementary biochemical approaches reveal that NSP4 binds to sulfated glycosaminoglycans on the plasma membrane.</p> <p>Conclusion</p> <p>Our study is the first to analyze an authentic (i.e. non-recombinant) form of NSP4 that is secreted from virus-infected cells. Despite retention of the transmembrane domain, secreted NSP4 remains soluble in an aqueous environment as an oligomeric lipoprotein that can bind to various cell types via an interaction with glycosaminoglycans. This broad cellular tropism exhibited by NSP4 may have implications for the pathophysiology of rotavirus disease.</p

Deville rebooted – practical N 2 O 5 synthesis †

Dinitrogen pentoxide (N2O5), the anhydride of nitric acid, was synthesised by Henri Étienne Sainte-Claire Deville in Paris in 1849 using silver nitrate and chlorine gas. Herein, we revisit, optimise, and modify Deville's method using photocatalysis to enable a safe, clean, practical, and reproducible alternative for N2O5 synthesis in quantitative yields. Moreover, it is predicted that the modifications can accommodate an industrial scale-up, but the silver chloride generated must be recycled

Flow electrochemistry for the N‐Nitrosation of secondary amines

A flow electrochemical method towards the synthesis of N‐nitroso compounds from secondary amines using cheap and readily available sodium nitrite has been developed. Sodium nitrite dissolved in aqueous acetonitrile made additional electrolytes unnecessary. This mild and straightforward approach made the use of acids or other harsh and toxic chemicals redundant. This procedure was applied to an assortment of cyclic and acyclic secondary amines (27 examples) resulting in yields of N‐nitrosamines as high as 99 %. To demonstrate the practicality of the process, scaled‐up reactions were performed. Finally, selected products could be purified by using an in‐line acidic extraction

The priming effect of extracellular UTP on human neutrophils: Role of calcium released from thapsigargin-sensitive intracellular stores

P2Y2 receptors, which are equally responsive to ATP and UTP, can trigger intracellular signaling events, such as intracellular calcium mobilization and mitogen-activated protein (MAP) kinase phosphorylation in polymorphonuclear leukocytes (PMN). Moreover, extracellular nucleotides have been shown to prime chemoattractant-induced superoxide production. The aim of our study was to investigate the mechanism responsible for the priming effect of extracellular nucleotides on reactive oxygen species (ROS) production induced in human neutrophils by two different chemoattractants: formyl-methionyl-leucyl-phenylalanine (fMLP) and interleukin-8 (IL-8). Nucleotide-induced priming of ROS production was concentration- and time-dependent. When UTP was added to neutrophil suspensions prior to chemoattractant, the increase of the response reached the maximum at 1 min of pre-incubation with the nucleotide. UTP potentiated the phosphorylation of p44/42 and p38 MAP kinases induced by chemoattractants, however the P2 receptor-mediated potentiation of ROS production was still detectable in the presence of a SB203580 or U0126, supporting the view that MAP kinases do not play a major role in regulating the nucleotide-induced effect. In the presence of thapsigargin, an inhibitor of the ubiquitous sarco-endoplasmic reticulum Ca2+-ATPases in mammalian cells, the effect of fMLP was not affected, but UTP-induced priming was abolished, suggesting that the release of calcium from thapsigargin-sensitive intracellular stores is essential for nucleotide-induced priming in human neutrophils