A study of diet and health in the elderly; the gut microbiota as a source of bioactive agents

The global proportion of older persons is increasing rapidly. Diet and the intestinal microbiota independently and jointly contribute to health in the elderly. The habitual dietary patterns and functional microbiota components of elderly subjects were investigated in order to identify specific effector mechanisms. A study of the dietary intake of Irish community-dwelling elderly subjects showed that the consumption of foods high in fat and/or sugar was excessive, while consumption of dairy foods was inadequate. Elderly females typically had a more nutrient- dense diet than males and a considerable proportion of subjects, particularly males, had inadequate intakes of calcium, magnesium, vitamin D, folate, zinc and vitamin C. The association between dietary patterns, glycaemic index and cognitive function was also investigated. Elderly subjects consuming ‘prudent’ dietary patterns had better cognitive function compared to those consuming ‘Western’ dietary patterns. Furthermore, fully-adjusted regression models revealed that a high glycaemic diet was associated with poor cognitive function, demonstrating a new link between nutrition and cognition. An extensive screening study of the elderly faecal-derived microbiota was also undertaken to examine the prevalence of antimicrobial production by intestinal bacteria. A number of previously characterised bacteriocins were isolated (gassericin T, ABP-118, mutacin II, enterocin L-50 and enterocin P) in this study. Interestingly, a Lactobacillus crispatus strain was found to produce a potentially novel antimicrobial compound. Full genome sequencing of this strain revealed the presence of three loci which exhibited varying degrees of homology with the genes responsible for helveticin J production in Lb. helveticus. An additional study comparing the immunomodulatory capacity of ‘viable’ and ‘non-viable’ Bifidobacterium strains found that Bifidobacterium-fermented milks (BFMs) containing ‘non-viable’ cells could stimulate levels of IL-10 and TNF-α in a manner similar to those stimulated by BFMs containing ‘viable’ cells in vitro.

Resonant power conversion topologies for inductive charging of electrical vehicle batteries

This thesis is concerned with inductive charging of electric vehicle batteries. Rectified power form the 50/60 Hz utility feeds a dc-ac converter which delivers high-frequency ac power to the electric vehicle inductive coupling inlet. The inlet configuration has been defined by the Society of Automotive Engineers in Recommended Practice J-1773. This thesis studies converter topologies related to the series resonant converter. When coupled to the vehicle inlet, the frequency-controlled series-resonant converter results in a capacitively-filtered series-parallel LCLC (SP-LCLC) resonant converter topology with zero voltage switching and many other desirable features. A novel time-domain transformation analysis, termed Modal Analysis, is developed, using a state variable transformation, to analyze and characterize this multi-resonant fourth-orderconverter. Next, Fundamental Mode Approximation (FMA) Analysis, based on a voltage-source model of the load, and its novel extension, Rectifier-Compensated FMA (RCFMA) Analysis, are developed and applied to the SP-LCLC converter. The RCFMA Analysis is a simpler and more intuitive analysis than the Modal Analysis, and provides a relatively accurate closed-form solution for the converter behavior. Phase control of the SP-LCLC converter is investigated as a control option. FMA and RCFMA Analyses are used for detailed characterization. The analyses identify areas of operation, which are also validated experimentally, where it is advantageous to phase control the converter. A novel hybrid control scheme is proposed which integrates frequency and phase control and achieves reduced operating frequency range and improved partial-load efficiency. The phase-controlled SP-LCLC converter can also be configured with a parallel load and is an excellent option for the application. The resulting topology implements soft-switching over the entire load range and has high full-load and partial-load efficiencies. RCFMA Analysis is used to analyze and characterize the new converter topology, and good correlation is shown with experimental results. Finally, a novel single-stage power-factor-corrected ac-dc converter is introduced, which uses the current-source characteristic of the SP-LCLC topology to provide power factor correction over a wide output power range from zero to full load. This converter exhibits all the advantageous characteristics of its dc-dc counterpart, with a reduced parts count and cost. Simulation and experimental results verify the operation of the new converter.