Background Nutritional treatment in the intensive care unit (ICU) has evolved from meeting nutritional requirements to manipulating patient outcome. Pharmaconutrition, referring to nutrients that are applied for their pharmacological properties, forms part of the standard nutritional care plan. The most abundant amino acid in the body, glutamine, is also the most-researched pharmaconutrient. It is an independent predictor of mortality in ICU patients, at both deficient and very high levels. Glutamine supplementation is recommended in the ICU setting for its proven outcome benefits. However, recent data showed that glutamine supplementation increases mortality risk in certain patient groups. Moreover, it suggested that not all ICU patients are glutamine deficient. Therefore, the main aim of this study was to investigate the plasma glutamine levels of adult ICU patients, on admission to the ICU. In addition, to elucidate the profile of ICU patients that can be expected to present with a glutamine deficiency or excess, with regards to gender, diagnosis and inflammatory markers. Methods In this observational, cross-sectional study, 60 mixed ICU adult patients admitted to two hospitals in the North West province were included in the study group. Blood sampling was conducted within 24 hours following ICU admission, to determine plasma glutamine, interleukin (IL)-6 and C-reactive protein (CRP) levels. Plasma glutamine levels were compared with those of a control group of healthy individuals, matched by age, race, and gender. Gender-related differences in plasma glutamine levels were investigated, as well as differences between patients with various medical conditions. The relationship between plasma glutamine levels and IL-6 or CRP was examined. Additionally, a CRP concentration cut-off point at which glutamine becomes deficient was determined by means of a receiver operating characteristic (ROC) curve. Results and discussion Intensive care unit patients had significantly lower plasma glutamine levels than healthy individuals on day one of ICU admission (p < 0.0001). However, only 38.3% (n = 23) had deficient plasma glutamine levels (< 420 μmol/L), while 6.7% (n = 4) presented with supra-normal levels (> 930 μmol/L). No significant difference could be detected between the plasma glutamine levels of male and female ICU patients (p = 0.116). Likewise, levels between diagnosis categories were also not significantly different (p = 0.325). There was a significant inverse association between plasma glutamine levels and CRP concentrations (r = -0.44, p < 0.05), and a trend towards an inverse association with IL-6 (r = - 0.23, p = 0.08). A CRP cut-off value of 95.5 mg/L was determined, above which plasma glutamine values became deficient; however, more research is needed to confirm this result. Conclusion and recommendations This research therefore showed that ICU patients, when compared with healthy individuals, had lower plasma glutamine levels on day one of admission to the ICU. However, not all were glutamine deficient, as the majority had normal and some presented with supra-normal plasma glutamine levels. An individualised approach should therefore be followed in identifying candidates for glutamine supplementation. The patients‟ condition alone may not be sufficient to predict glutamine status, but an association between plasma glutamine levels and CRP was firmly established, as well as a cut- off CRP-value above which glutamine can be expected to become deficient, which could be of use in this regard. / MSc (Dietetics), North-West University, Potchefstroom Campus, 2015

Background Nutritional treatment in the intensive care unit (ICU) has evolved from meeting nutritional requirements to manipulating patient outcome. Pharmaconutrition, referring to nutrients that are applied for their pharmacological properties, forms part of the standard nutritional care plan. The most abundant amino acid in the body, glutamine, is also the most-researched pharmaconutrient. It is an independent predictor of mortality in ICU patients, at both deficient and very high levels. Glutamine supplementation is recommended in the ICU setting for its proven outcome benefits. However, recent data showed that glutamine supplementation increases mortality risk in certain patient groups. Moreover, it suggested that not all ICU patients are glutamine deficient. Therefore, the main aim of this study was to investigate the plasma glutamine levels of adult ICU patients, on admission to the ICU. In addition, to elucidate the profile of ICU patients that can be expected to present with a glutamine deficiency or excess, with regards to gender, diagnosis and inflammatory markers. Methods In this observational, cross-sectional study, 60 mixed ICU adult patients admitted to two hospitals in the North West province were included in the study group. Blood sampling was conducted within 24 hours following ICU admission, to determine plasma glutamine, interleukin (IL)-6 and C-reactive protein (CRP) levels. Plasma glutamine levels were compared with those of a control group of healthy individuals, matched by age, race, and gender. Gender-related differences in plasma glutamine levels were investigated, as well as differences between patients with various medical conditions. The relationship between plasma glutamine levels and IL-6 or CRP was examined. Additionally, a CRP concentration cut-off point at which glutamine becomes deficient was determined by means of a receiver operating characteristic (ROC) curve. Results and discussion Intensive care unit patients had significantly lower plasma glutamine levels than healthy individuals on day one of ICU admission (p < 0.0001). However, only 38.3% (n = 23) had deficient plasma glutamine levels (< 420 μmol/L), while 6.7% (n = 4) presented with supra-normal levels (> 930 μmol/L). No significant difference could be detected between the plasma glutamine levels of male and female ICU patients (p = 0.116). Likewise, levels between diagnosis categories were also not significantly different (p = 0.325). There was a significant inverse association between plasma glutamine levels and CRP concentrations (r = -0.44, p < 0.05), and a trend towards an inverse association with IL-6 (r = - 0.23, p = 0.08). A CRP cut-off value of 95.5 mg/L was determined, above which plasma glutamine values became deficient; however, more research is needed to confirm this result. Conclusion and recommendations This research therefore showed that ICU patients, when compared with healthy individuals, had lower plasma glutamine levels on day one of admission to the ICU. However, not all were glutamine deficient, as the majority had normal and some presented with supra-normal plasma glutamine levels. An individualised approach should therefore be followed in identifying candidates for glutamine supplementation. The patients‟ condition alone may not be sufficient to predict glutamine status, but an association between plasma glutamine levels and CRP was firmly established, as well as a cut- off CRP-value above which glutamine can be expected to become deficient, which could be of use in this regard. / MSc (Dietetics), North-West University, Potchefstroom Campus, 2015

Redundant robotic systems, in terms of manipulators with one or twoarms, mobile manipulators, and multi-agent systems, have received an in-creasing amount of attention in recent years. In this thesis we describe severalways to improve robotic system performance by exploiting the redundancy. As the robot workspace becomes increasingly dynamic, it is common towork with imperfect geometric models of the robots or its workspace. Inorder to control the robot in a robust way in the presence of geometric uncer-tainties, we propose to assess the stability of our controller with respect to acertain task by deriving bounds on the geometric uncertainties. Preliminaryexperimental results support the fact that stability is ensured if the proposedbounds on the geometric uncertainties are fulfilled. As a non-contact measurement, computer vision could provide rich infor-mation for robot control. We introduce a two step method that transformsthe position-based visual servoing problem into a quadratic optimization prob-lem with linear constraints. This method is optimal in terms of minimizinggeodesic distance and allows us to integrate constraints, e.g. visibility con-straints, in a natural way. In the case of a single robot with redundant degrees of freedom, we canspecify a family of complex robotic tasks using constraint based programming(CBP). CBP allows us to represent robotic tasks with a set of equality andinequality constraints. Using these constraints we can formulate quadraticprogramming problems that exploit the redundancy of the robot and itera-tively resolve the trade-off between the different constraints. For example, wecould improve the velocity or force transmission ratios along a task-dependent direction using the priorities between different constraints in real time. Using the reactiveness of CBP, we formulated and implemented a dual-armpan cleaning task. If we mount a dual-arm robot on a mobile base, we proposeto use a virtual kinematic chain to specify the coordination between the mobilebase and two arms. Using the modularity of the CBP, we can integrate themobility and dual-arm manipulation by adding coordination constraints intoan optimization problem where dual-arm manipulation constraints are alreadyspecified. We also found that the reactiveness and modularity of the CBPapproach is important in the context of teleoperation. Inspired by the 3Ddesign community, we proposed a teleoperation interface control mode thatis identical to the ones being used to locally navigate the virtual viewpoint ofmost Computer Aided Design (CAD) softwares. In the case of multiple robots, we combine ideas from multi-agent coopera-tive coverage control, with problem formulations from the resource allocationfield, to create a distributed convergent approach to the resource positioningproblem. / <p>QC 20160224</p>

Secoisolariciresinol (SECO) is the major lignan present in flaxseed, but unlike the structurally related lignan nordihydroguaiaretic acid, it is not associated with toxicity. The major phase I metabolite of SECO is lariciresinol, likely formed as a result of para-quinone methide (p-QM) formation followed by an intramolecular cyclization, thereby minimizing any toxicity associated with the p-QM. Four analogues of SECO were used to investigate substituent effects on lignan metabolism and formation of reactive quinones. HPLC methods were developed for analysis of SECO analogues and their metabolites. The stability of SECO analogues (1 mM) in a 50 mM Na2HPO4 buffer at pH 6.0 and 7.4 were quantified. Enzymatic oxidation experiments using mushroom tyrosinase and microsomes harvested from male Sprague-Dawley rats were performed with and without a GSH trapping system. Mass spectrometry and LC-MS were used to identify metabolites. Life Technologies was contracted to perform IC50 inhibition assays on SECO and the SECO analogues against CYP3A4, CYP3A5, CYP2C9 and CYP2C19 cytochrome P450 isoforms. All SECO analogues were stable at pH 6.0. SECO-2 was stable at pH 7.4 but SECO-1, -3 and -4 were unstable at pH 7.4. Autoxidation of SECO -1, -3 and -4 were 1st order reactions with t1/2 of 9.0 h, 1.7 h and 7.0 h respectively. Mushroom tyrosinase oxidations were performed to generate ortho-quinone standards. SECO-1 -3 and -4 were oxidized by mushroom tyrosinase but SECO-2 was not. Trapping with GSH produces aromatic ring conjugates for SECO-1, -3, -4. Results from microsomal oxidations for SECO-1, -3 and -4 are consistent with these standards. SECO-2 was metabolized by a microsomal system to produce a benzyl GSH adduct. Dealkylation products were also observed. All SECO analogues formed quinones but interestingly, GSH conjugation was competitive with intramolecular cyclization. All cytochrome P450 isoforms were inhibited by every analogue tested to varying degrees, a potential cause of toxicity concerns. Quinones are known to cause toxicity in vivo, including cytotoxicity, immunotoxicity, and carcinogenesis. Our results suggest that since the phenol and catechol lignans form GSH adducts in addition to intramolecular cyclization products, this class of lignans have the potential to cause toxicity.

Brown algae have been the focus of metal ecotoxicology research for over 60 years, mainly because of their high metal accumulation capacity and reputed resistance. Now that Ectocarpus siliculosus has been positioned as a model for the study of brown algae, and that the genome has been recently sequenced and annotated, new lines of research have been made possible on these ecologically and economically important organisms, including the field of ecotoxicology. Several strains of E. siliculosus have been collected and isolated from locations around the world, thus providing the opportunity to study inter-population differences in their responses to environmental stress. This investigation can be split into three main sections. In the first part Cu exposure experiments were carried out under laboratory conditions using three strains of E. siliculosus: Es524 from a Cu polluted location in Chile, REP10-11 from a metal polluted (including Cu) location in England and LIA4A from a pristine site in Scotland. Strains were exposed for 10 d to concentrations ranging between 0 and 2.4 μM Cu. We measured different parameters: relative growth rates; metal accumulation (extracellular and intracellular); phytochelatins and the expression of related enzymes; oxidative stress responses as manifested in lipid peroxidation and levels of H2O2, and levels of pigments; levels of antioxidants glutathione and ascorbate (in reduced and oxidised forms), and phenolic compounds; and the activity of the antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidise. Strain Es524 was the most efficient in counteracting the effects of Cu stress as manifested by a combination of Cu exclusion production of metal chelators, upregulation of oxidative enzymes, and strong antioxidant metabolism. REP10-11 also showed effective Cu defences, especially related to glutathione-ascorbate interactions. LIA4A was the least tolerant strain, with metabolic defences significantly less effective against Cu exposure. In part two a novel transplantation experiment was developed to compare responses in the field with those obtained in the laboratory. The study was carried out at a metal polluted and a low-impacted site in central Chile using strain Es524 (as in the laboratory experiments) and Es147, isolated from a low metal-polluted site in Chile. From the biomass, we conducted similar measurements of Reactive Oxygen Metabolism (ROM) as for the laboratory experiments described in the first part. In agreement with the laboratory experiments, strain Es524 displayed a higher resistance to metal stress. Because they behaved similarly between strains, the best suggested biomarker candidates for future assessments are metal accumulation, glutathione and ascorbate in reduced and oxidised forms, phenolic compounds, and the activity of superoxide dismutase. The method is simple, widely applicable in temperate environments, cost-effective, and provides a reliable representation of metal bioavailability in the environment. In the final part of the study a novel technique for the co-extraction of RNA and DNA, using a high pH Tris-HCl buffer, from small amounts of biomass of different strains of E. siliculosus was successfully developed. The extraction of nucleic acids from brown algae is considered to be difficult and the product is of poor quality due to the high concentrations of interfering secondary metabolites such as phenolics and polysaccharides. The protocol devised here provided high yields of pure RNA and DNA that are suitable for molecular analyses. This investigation provides new insights on metal stress metabolism in brown algae, and demonstrates that metal resistance is dependent on inherited defences developed over a long history of exposure. Furthermore, the good agreement between the results obtained in the laboratory with those from the field study confirms that the responses expressed under controlled laboratory conditions are representative of stress metabolism of E. siliculosus under natural conditions.

In the current work, the photophysics and photochemistry of the phototoxic red fluorescent protein (RFP) KillerRed was investigated. KillerRed's phototoxicity makes it useful for studying oxidative stress on cell physiology and for cell killing in photodynamic therapy. Spectroscopic probes were used to show that the phototoxicity of KillerRed stems primarily from a type I photosensitization mechanism producing radicals. The production of radicals was supported by electron paramagnetic resonance (EPR) studies, where a long-lived radical was observed in KillerRed and two other RFPs (mRFP and DsRed) following excitation. Transient absorption spectroscopy, various other spectroscopic techniques, and the published crystal structure of KillerRed indicate that the long-filled water channel is likely responsible for the increased phototoxicity of KillerRed. In the blue fluorescent protein (BFP) mKalama1, some of the same techniques were applied to understand the photophysics and photochemistry on the timescale ranging from femtoseconds to seconds. Transient absorption spectroscopy and previously published results demonstrate that two-photon excitation of mKalama1 likely results in the formation of a radical cation and solvated electrons. This may explain the blinking behavior which has been observed on the single molecule level for many fluorescent proteins, the identity of which has remained elusive. It was also shown that the chromophore, while neutral in the ground state, does not exhibit excited-state proton transfer (ESPT) during its nanosecond excited-state lifetime; however, the chromophore undergoes a deprotonation in the ground state after electronic relaxation. This work plays a key role in our understanding of fluorescent proteins and will help pave the way to developing new ones. The research on the BFPs was extended to improve them for cellular imaging. This was accomplished by identification of dark states in the BFPs which are longer in wavelength than the collected fluorescence. Using dual lasers, it was shown that these dark states could be optically depleted, thereby increasing the overall fluorescence without enhancing the background fluorescence. Rational site-directed mutagenesis was carried out on the BFPs and the mutants were screened for fluorescence enhancement. These proteins were then analyzed using transient absorption spectroscopy to elucidate the identity of the dark state(s) used for fluorescence enhancement.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This dissertation presents a circuit-based design technique that leads to benefits in terms of the physical size, manufacturability, and exibility in the design of N-way conical line power combiners. An equivalent circuit model for the peripheral input ports of conical line power combiners is extracted, as well as empirical equations that allow the circuit element values to be calculated directly from the physical dimensions of the combiner, and vice versa. This allows for rapid optimization of various dimensions of the combiner at a significantly reduced computational cost compared to full-wave simulations. A design procedure is presented and a conical combiner designed with a measured reflection coefficient of better than -18 dB over a 46 % bandwidth around 10 GHz. The designed prototype is much smaller compared to previous designs while exhibiting similar performance. Design procedures for single-section and multi-section impedance tapered conical to coaxial line transitions are also presented, which can be used to simplify the design of conical combiners and reduce the manufacturing effort. Two combiners are designed, one with a single-section and one with a multi-section transition, and output port reflection coefficients of -23 dB and -17 dB over bandwidths of 20 % and 43 % around 10 GHz are measured, respectively. This dissertation additionally presents a method that can be used in general to improve the input port isolation of N-way power combiners without affecting their reciprocity. A simple S-parameter proof is presented, followed by a derivation of equations that can be used to estimate the worst-case performance. Some design examples are presented, showing that terminations can be used for isolation loads. A prototype based on microstrip transmission lines is manufactured and a much improved input port reflection and isolation performance of -15 dB and 20 dB is measured, respectively, compared to a simulated input port reflection coefficient of -2:5 dB and isolation of 2:5 dB before the method was applied. ii / AFRIKAANSE OPSOMMING: Hierdie proefskrif stel 'n stroombaangebaseerde ontwerpsmetode voor wat lei tot voordele in terme van die fisiese grootte, vervaardigbaarheid, en vryheid in die ontwerp van koniese lyn kombineerders. 'n Ekwivalente stroombaanmodel vir die voerpoorte word onttrek, asook empiriese vergelykings wat gebruik kan word om die stroombaanelement waardes vanaf die afmetings van die kombineerder te bepaal. Dit laat die ontwerper toe om verskeie afmetings van die kombineerder te optimeer teen 'n beduidende laer koste in vergelyking met volgolf simulasies. 'n Ontwerpsprosedure word voorgestel en gebruik om 'n koniese kombineerder te ontwerp en 'n weerkaatskoëffisient van beter as -18 dB met 'n bandwydte van 46 % om 10 GHz word gemeet. Die prototipe is aansienlik kleiner as vorige ontwerpe, maar toon soortgelyke werkverrigting. Ontwerpsprosedures vir enkel en veelvoudige deel koniese na koaksiale lyn oorgange word ook voorgestel, wat gebruik kan word om die ontwerp en vervaardiging van koniese kombineerders te vereenvoudig. Twee kombineerders word ontwerp, een met 'n enkel deel oorgang en een met veelvoudige dele, en onderskeidelike uittree weerkaatskoëffisiente van -23 dB en -17 dB oor bandwydtes van 20 % en 43 % word gemeet. Hierdie proefskrif stel ook 'n metode voor wat gebruik kan word om die intree poort isolasie van N-rigting kombineerders in die algemeen te verbeter, sonder om die wederkerigheid daarvan te beïnvloed. 'n Bewys van die metode word gelewer, gevolg deur 'n afleiding van vergelykings wat gebruik kan word om die slegste-geval werkverrigting af te skat. Verskillende voorbeelde van kombineerders word getoon waarop die metode toegepas is, en wys dat terminasies gebruik kan word vir die isolasie laste. 'n Prototipe gebaseer op mikrostrook transmissielyne word vervaardig en 'n verbeterde intreepoort weerkaatskoëffisient en isolasie van onderskeidelik -15 dB en 20 dB word gemeet, in vergelyking met 'n weerkaatskoëffisient van -2:5 dB en isolasie van 2:5 dB voordat die metode toegepas is.

<p>In Sweden more than 400 000 private households have not yet sufficient wastewater purification. These effluent is considered as an increasing problem and many onsite purification methods have been studied. In this investigation, the method of reactive bed filters have been tested by column and batch experiments. Five different kinds of filter materials with reactive surfaces have been studied concerning their capacity to absorb ammonium and phosphorus from wastewater. The materials that were examined are Filtra N, wollastonite Filtra P, blast furnace slag and Polonite®. The first two materials were examined for their capacity to remove ammonium, and the others for their phosphorus removal capacity.</p><p>Ten columns were used, two for each material. A synthetic solution with the ammonium and phosphate concentration similar to that of domestic wastewater (NH4-N 30 mg/l; PO4-P 5 mg/l) were pumped to the columns under two flow regimes. Five columns were continuously saturated with solution and the other five columns were saturated under three one hour periods a day The solution was pumped three times a day to the columns at a volume equal to the pore volume of each material. The objective of the batch experiment was to find out how variations in pH-value and concentration of the nutrients influenced the sorption capacity of the materials. The result was then used for modelling in the computer program Visual Minteq to determine the probability of precipitation of known compounds.</p><p>Results from the column experiment showed that sorption of phosphorus in both saturated columns and intermittently saturated columns were 96 % or more for blast furnace slag, Filtra P and Polonite®. Filtra N showed the best ammonium sorption with 92 %. Sorption of ammonium was much better in periodically saturated columns for the material wollastonite. The wollastonite used in this experiment showed a higher phosphorus sorption capacity than expected. A possible explanation could be that the easy weathering of Ca-silicate compounds favoured the sorption of phosphorus. Results from Visual Minteq modelling showed that the probability of calcite formation in Filtra P and Polonite® are very likely. The two materials had high pH-values and the calcite was most likely formed at values of pH > 10. Hydroxyapatite is the most common precipitation when phosphorus sorption occurs and is suggested to be formed in wollastonite.</p> / <p>Mer än hälften av Sveriges enskilda avlopp bedöms inte uppfylla kraven i miljöbalken på längre gående rening än slamavskiljning. Dessa står för en betydande del av fosfor- och kväveutsläppen till hav, sjöar och vattendrag. Åtskilliga systemlösningar utreds, men i denna rapport har filter med fosfor- och kvävesorberande förmågor testats eller s.k. reaktiva filter. Mineraliska filter som ingått i studien är Filtra N, wollastonit, Filtra P, hyttsand och Polonite®. De två första filtren studerades speciellt på deras förmåga att avskilja ammonium och de tre övriga främst på deras fosforavskiljnings förmåga.</p><p>Kolonnförsök utfördes med tio kolonner där fem belastades med mättat flöde och de övriga med intermittent mättat flöde. Kolonnuppsättningen var två kolonner per filtermaterial med vardera olika flödesförhållanden. Belastningen på kolonnerna sattes till betydligt högre än traditionell infiltration/markbädd. Ett artificiellt avloppsvatten användes och tillreddes med en koncentration av kväve (NH4-N) på 30 mg/l och fosforkoncentration (PO4-P) på 5 mg/l. De valda koncentrationerna efterliknar ett vanligt hushållsspillvatten. Skakförsök utfördes för att undersöka sorptionsförmågan hos de olika mineraliska filtren där vikten låg på hur koncentrationen av näringsämnena och pH påverkar sorptionen. Resultaten från skakförsöken utvärderades med jämviktsmodellen Visual Minteq. Sannolikheten att kända utfällningar bildas studerades.</p><p>Resultaten från kolonnförsöken visade att hyttsand, Filtra P och Polonite® gav bäst fosforavskiljning med över 96 % för båda flödesregimerna. Filtra N var den bästa ammoniumavskiljaren med över 92 %. Wollastonit hade en bättre avskiljning med intermittent mättat flöde med 65 % jämfört med 11 % för mättat flöde. En intressant iakttagelse var att wollastonit hade en bättre fosforavskiljning än ammoniumavskiljning med ca 60 % för båda flödena. Det kan bero på att filtret innehåller lättvittrade Ca-silikatföreningar som ökar fosfatavskiljningen. Skakförsöken resulterade i att för Filtra P, hyttsand och Polonite® sorberades all tillsatt fosfat. Filtra N visade samma resultat som i kolonnförsöken med över 92 % sorption. Endast fosfat sorberades vid försök med tillsättning av både fosfat och ammonium till hyttsand och wollastonit. Vid modellering i Visual Minteq finns det en viss sannolikhet att kalcit bildats i Filtra P och Polonite® p g a deras höga pH, kalcit fälls ut vid pH > 10. Hydroxyapatit som är den vanligaste utfällningen av kalciumfosfat vid avskiljning av fosfor bildades mycket troligt i wollastonit.</p>

The research programme at the University of Canterbury includes the development and applications of partial core inductors and transformers for high voltage testing of generator insulation. Unlike a conventional full core transformer, a partial core transformer has no limbs and yokes. A partial core transformer is a compromise between a full core and coreless transformer. It is superior to its full core counterpart as far as cost, weight and ease of transportation are concerned. Partial core transformers have a low magnetising reactance and hence draw a high magnetising current. This characteristic makes them a perfect fit in applications where the load is capacitive in nature, such as a.c. power frequency high voltage testing of generator insulation and cable testing etc. The work carried out for this thesis focuses on automatically controlling the amount of reactive power on the supply side of a partial core transformer. The considered design includes a third winding around the existing two windings. A power electronic controller is connected to the third winding, which modifies the VAr absorption characteristics of the magnetically coupled supply winding. Two options are considered to achieve continuous reactive power control in the partial core transformer as explained below. First, a thyristor controlled reactor (TCR) is proposed as the VAr controller. It is modelled using PSCAD/EMTDC software. Simulations reveal the design criteria, overall performance and the limitations of the suggested proposal. The TCR connected tertiary winding takes the capacitive burden of the supply. The model demonstrates the ability of the automatically controlled TCR to provide a continuous variation of reactive power without significant under or over compensation. This feature limits the supply current to its real component only, so the supply provides only the losses of the system. Second, a voltage source converter is considered as the VAr controller. This is modelled in PSCAD/EMTDC and a hardware prototype is designed and built. Based on the analysis, the control algorithm (including a digital PI controller) is implemented using an 8 bit micro-controller, PIC18LF4680. The prototype is tested in the laboratory for both active and inductive load conditions as seen from the supply side. Performance of the hardware prototype is discussed in detail. The PSCAD/EMTDC model and the hardware prototype successfully demonstrate the feasibility of a STATCOM controlled partial core transformer. The proposed system is capable of compensating a wide range of capacitive loads as compared with its TCR counterpart. It is proved that the system is very robust and remains dynamically stable for a large system disturbance such as change in load from full capacitive to inductive and vice versa. This confirms that the system is capable of providing continuous VAr control.

Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and superoxide (O2 • −) have been shown to serve as messengers in biological signal transduction, and many prokaryotic and eukaryotic proteins are now known to have their function controlled via ROS-mediated oxidation reactions occurring on critical cysteine residues. The tumour-suppressor protein p53 is involved in the regulation of a diverse range of cellular processes including apoptosis, differentiation, senescence, DNArepair, cell-cycle arrest, autophagy, glycolysis and oxidative stress. However, little is understood about the specific molecular mechanisms that allow p53 to discriminate between these various different functions. p53 is a multiple cysteine-containing protein and there is mounting evidence to suggest that redox-modification of p53 Cys residues participate in control of its biological activity. Furthermore, p53 activity has been linked to intracellular ROS levels. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers superior mass resolving power and mass measurement accuracy, which is beneficial for the study of intact proteins and the characterisation of their posttranslational modifications (PTMs). The primary goal of the work described in this thesis was to employ FT-ICR mass spectrometry to investigate the molecular details of p53 redox-regulation. The relative reactivity of each of the ten cysteine residues in the DNA-binding core domain of recombinant human p53 was characterised by treatment with the Cys-alkylating reagent N-ethylmaleimide (NEM) under various conditions. A combination of top-down and middle-down FT-ICR MS was used to unambiguously identify Cys182 and Cys277 as sites of preferential alkylation. These results were confirmed by site-directed mutagenesis. Interestingly, Cys182 and Cys277 have previously been implicated in p53 redox-regulation. Alkylation beyond these two residues was found to trigger rapid alkylation of the remaining Cys residues, presumably accompanied by protein unfolding. These observations have implications for the re-activation of mutant p53 with Cys-targeting compounds which result in the death of cancer-cells. Furthermore, the molecular interaction between p53 and the ROS hydrogen peroxide was investigated. p53 was found to form two disulfide bonds upon treatment with H2O2. An enrichment strategy was developed to purify oxidised p53 and top-down FT-ICR mass spectrometry revealed unambiguously that Cys176, 182, 238 and 242 were the oxidised residues. Interestingly, Cys176, 238 and 242 are Zn2+- binding residues suggesting that p53 contains a zinc-redox switch. The mechanism of H2O2 oxidation was investigated, and revealed that oxidation via an alternative pathway results in indiscriminate over-oxidation of p53. Moreover, Cys176, 238 or 242 was shown to act as a nucleophile, and the intracellular antioxidant glutathione (GSH) did not prevent oxidation of the Zn2+-binding Cys residues, providing further evidence for a role in p53 redox-regulation. This study has revealed hitherto unknown details regarding the chemistry of cysteine residues within the important tumour-suppressor protein p53. Furthermore, the analytical power of FT-ICR MS for the study of multiple Cys-containing proteins has been very clearly demonstrated.