The aim of the present research is to assess the control and operation of a Spinning Disc Reactor (SDR), carried out via four separate investigations. Firstly, the effect of equipment size reduction on control is studied by comparing the performance of a PID controller applied to simulated intensified and conventional processes. It was found that superior control performance in terms of Integral of Absolute Error (IAE) is achieved for the simulated intensified system. However, the results showed that intensified systems are more susceptible to disturbances and the controlled variable exhibits larger overshoots. Furthermore, the frequency response analysis of the two systems showed that the simulated intensified system has reduced stability margins. The second part of the research investigates the task of pH control in a SDR using a PID controller by means of simulation and experimental studies. The effectiveness of a disturbance observer (DO) and a pH characteriser to compensate for the severe pH system nonlinearity is also explored in detail. The experimental studies showed that a PID controller provides adequate setpoint tracking and disturbance rejection performances. However, sluggish transient responses prevailed and the effluent pH limit cycled around the setpoint. There were indications of unstable behaviour at lower flowrates, which implied more advanced control schemas may be required to adapt to various operating regions dictated by the complex thin film hydrodynamics. The addition of the DO scheme improved the control performance by reducing the limit cycles. In the third segment of the investigations, the potential of exploiting the disc rotational speed as a manipulated variable is assessed for the process of barium sulphate precipitation. A PI controller is successfully used to regulate the conductivity of the effluent stream by adjusting the disc rotational speed. The results are immensely encouraging and show that the disc speed may be used as an extra degree of freedom in control system design. Finally, the flow regimes and wave characteristics of thin liquid films produced in a SDR are investigated by means of a thermal imaging camera. The film hydrodynamics strongly affect the heat and mass transfer processes within the processing films, and thus the intensification aspects of SDRs. Therefore, effective control and operation of such units is significantly dependent on the knowledge of film hydrodynamics and the underlying impact of the operating parameters and the manipulated variables on a given process. The results provided an interesting insight and unveiled promising potentials for characterisation of thin liquid film flow and temperature profiles across the disc by means of thermographic techniques. The present study reveals both challenges and opportunities regarding the control aspects of SDRs. It is recommended that equipment design and process control need to be considered simultaneously during the early stages of the future developments. Furthermore, intensified sensors and advanced controllers may be required to achieve an optimum control capability. Currently, the control performance is inhibited by the lack of sufficient considerations during the SDR design and manufacturing stages, and also by the characteristics of the commercially available instrumentation.

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The Weibel Palade body (WPB) is the major regulated secretory organelle of endothelial cells. The WPB is used here as a model system to investigate the formation and acquisition of membrane identity of regulated secretory organelles. Heterologous expression of von Willebrand (VWF), the main secretory cargo of WPBs, in cells lacking endogenous VWF, is able to induce the formation of structures that are not only morphologically indistinguishable from WPBs but also recruit the appropriate membrane components resulting in the correct membrane identity. The question arises as to how VWF acts within the lumen of the secretory pathway to do this. The working hypothesis is that VWF drives the formation of WPB and the acquisition of membrane identity by direct interaction with specific lipids on the lumenal face of the lipid bilayer. This thesis describes attempts to test this hypothesis both directly, by looking for putative interactions of VWF with membrane lipids and indirectly, by studying the role of glycosphingolipids in WPB formation. To look for direct interaction of VWF with membrane lipids, attempts were made to produce recombinant, enzymatically tagged VWF probes and develop an overlay assay. Glycoarrays were also probed with VWF to identify potential glycan binding partners. VWF was found to bind to a class of fucosylated glycans on the array. In order to look for the influence of glycosphingolipids on WPB formation two distinct approaches were taken The effect of drug-mediated inhibition of membrane glycosphingolipid synthesis on WPB formation in cultured human endothelial cells was investigated. Inhibition of glucosylceramide synthesis, and hence complex glycosphingolipids, by N-butyldeoxygalactonojirimycin had no apparent effect on VWF trafficking. Trafficking of heterologously expressed VWF was studied in two epithelial cell lines, known to have distinct glycosphingolipid compositions. The two cell lines were shown to differ in VWF trafficking both morphologically and biochemically. VWF was also shown to be differentially glycosylated between the two cell lines, suggesting a link between VWF glycosylation and trafficking.

The interferon alpha receptor (IFNAR) and T-cell receptor (TCR) are expressed upon the T-cell surface. The dimeric Class I interferon receptor is a cytokine receptor that recognises interferons such as IFNα. Interferons (IFNs) are pluripotent, antiviral cytokines that causes antiproliferative effects, primarily through Jak/STAT signalling. The T-cell receptor is an antigenic receptor that recognises antigenically-derived peptides in the context of the MHC complex located on an antigen presenting cell, resulting in a cellular proliferation. Although both receptors elicit opposing cellular outcomes, both the TCR and IFNAR activate the ERK MAPK signalling pathway, albeit with a different time course. Furthermore, studies have shown that the IFNAR and TCR utilise an overlapping subset of proteins for this pathway to occur such as CD45, Lck and Zap70. In this study evidence is presented to show that two further TCR-associated proteins are phosphorylated in response to the IFNAR; the 95kDa guanosine nucleotide exchange factor, Vav, and the 76kDa adaptor protein Slp76. This proceeds in a similar manner to that observed at the TCR. Furthermore, the absence of either protein impairs IFNAR-induced ERK MAPK signalling. The similarities between TCR and IFNAR signalling led to questioning of whether crosstalk occurs between the two receptors. To address this possibility a TCRβ deficient cell line, which lacks functional TCR expression, was utilised. It was demonstrated that the absence of the TCR completely abrogates the ERK MAPK response emanating from the IFNAR yet Jak/STAT signalling is unaffected. These results highlight for the first time an intimate connection between the TCR and IFNAR.

Gamma-amino butyric acid (GABA) is the principal inhibitory neurotransmitter in the adult central nervous system (CNS) and signals via ionotropic GABAA receptors and metabotropic GABAB receptors. GABAB receptors are obligate heterodimers comprised of GABAB(i) and GABAB(2) subunits, members of the Family 3 G-protein coupled receptors (GPCRs). GABABL is an orphan Family 3 GPCR of unknown function, most closely related to GABAB receptors. To investigate the functions of these genes during vertebrate development, Xenopus laevis GABAB(1), GABAB(2) and GABABL cDNAs were isolated, and their spatiotemporal expression patterns during embryogenesis analysed by RT-PCR and in situ hybridization. Maternal GABAB(2) transcripts were detected by RT-PCR in blastulae, whereas GABAB(1) and GABABL transcripts were not detected until gastrulation and neurulation respectively. In situ hybridization revealed that GABAB(i} and GABAB{2) transcripts were co-expressed in most brain regions, although areas of unique GABAB(i} expression also existed, and GABABL transcripts were located primarily in the brain and otic vesicle of the tailbud embryo. Co-expression of GABAB(1) and GABAB(2) transcripts suggests a role for metabotropic GABA receptor signalling in the developing brain of Xenopus embryos. However, overexpression of GABAB(1) and GABAB(2) transcripts together or in isolation, during embryonic development did not generate a distinct morphological phenotype. In contrast, embryos overexpressing GABABL during embryonic development exhibited a significant body truncation phenotype. Animal cap assays indicated that GABABL overexpression interferes with mesodermal convergent extension, whilst RT-PCR shows that the expression of mesoderm-specific markers is not affected, demonstrating morphogenetic but not biochemical activity of GABABL. Whilst the temporal expression pattern of GABABL does not support an endogenous role in the regulation of convergent extension in Xenopus , these experiments demonstrate that GABABL is a functional protein that acts in a manner reminiscent of a GPCR by disrupting intracellular signalling cascades.

The calcium channel alpha-2-delta (0,28) subunit is an auxiliary subunit associated with voltage-dependent calcium channels. It is implicated in the trafficking and functional expression of the calcium channel complex. This study expands the functional role of the VWA domain and the RRR motif of the 0:26 subunit, and the interaction between this subunit and the anti-epileptic drug, gabapentin The VWA domain is normally found in integrins, where it mediates binding to extracellular proteins. A mutation in the 0:28-2 subunit VWA domain (uMIDAS) did not produce the increase in current amplitude elicited by the wildtype (WT) 0:28-2 control. Co-immunoprecipitation studies using tsA-201 cells (stably expressing OC28-2 containing a mid-HA tag) co-cultured with cerebellar granule cells identified potential proteins from the cerebellar cultures that co-immunoprecipitate with the 0:28-2 protein. This suggests that protein from cerebellar cultures may bind the 0:28-2 subunit. Secondly, an RRR motif found in 0128-I subunit has been implicated as important for binding of the anticonvulsant drug gabapentin (Wang et al., 1999). The electrophysiological properties of the RRA mutant OC28 proteins were examined, and found not to enhance current amplitude to the full extent seen by WT 0:28-1 and 0:28-2 coexpression. Binding studies using both membrane and lipid raft of tsA-201 cells expressing 0:28-1 confirmed a lack of 3H-gabapentin in the R217A mutant condition. Chronic exposure of tsA-201 cells expressing Cav2.1, p4, 0:28-2 or Cav2.2, pib, 0:28-1 to gabapentin resulted in a reduction in size of the resultant currents. The inhibitory action of gabapentin was prevented by pre-incubation of cells with the system-L amino-acid transport inhibitor, suggesting gabapentin acts intracellularly after uptake via this transport mechanism. The inhibitory effects of gabapentin exposure were not replicated using co-expression of 0:28-3, or the non gabapentin-binding mutant 0128-I R217A or a28-2 R282A proteins. This indicated the inhibitory effect was mediated through gabapentin-binding calcium channel a28 subunits.

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No description available.