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Plasma Assisted Catalytic Reduction (PACR) of NO x has been investigated at laboratory scale for gas stream compositions representative of marine diesel exhausts. PACR NO x reduction in excess of 90% was measured at 350°C, a plasma specific energy of 60 J/l and two NO x concentrations (1,200 and 1,800 ppm). PACR NO x reduction of over 50% was measured for simulated marine engine conditions at 250°C, 60 J/l and 1,200 ppm NO x . The performance under these conditions could be increased, achieving a peak of *74% NO x reduction, although at a relatively high plasma power. Water, present in diesel exhaust, was shown to inhibit the poisoning effects of fuel sulphur using SO 2 as a representative exhaust component. The PACR system performance demonstrated tolerance to simulated fuel sulphur levels of up to 1% for the duration of the tests. PACR performance was also shown to be sensitive to the amount of hydrocarbon reductant used.

A reaction mechanism has been developed that is appropriate for the plasma aftertreatment of diesel exhaust gas. It is based on a simulated gas mixture containing propene, nitric oxide, nitrogen dioxide, oxygen and nitrogen. The reaction mechanism has been used to determine the end-products from the plasma processing and their concentrations using a chemical kinetics modelling procedure. It has been validated by a range of experiments using the same gas mixture with a packed bed, a dielectric barrier plasma reactor and a wide range of end-product analysis techniques. Using a wide range of experimental conditions has enabled us to validate the model and its predictions and to critically evaluate several alternative reaction mechanisms for the oxidation of propene and the formation of end-products in a more systematic and reliable manner than before.

It has been demonstrated that a dielectric packed pellet-bed plasma reactor operating on a mixture of NO 2 in air at atmospheric pressure can be used as an efficient method for the synthesis of dinitrogen pentoxide, N 2 O 5 . The reactor is packed with glass beads and operates at high frequency (10-13 kHz) and high voltage (V pk−pk < 30 kV). Typically, the energy density is 38 J l −1 and 45 ppm of NO 2 is converted into 53 ppm of N 2 O 5 . The synthesis of N 2 O 5 is found to be plasma-assisted in the sense that sources of nitrogen in addition to the initial NO 2 are converted into N 2 O 5 by the plasma. There is an energy cost of ∼180 eV for every molecule of N 2 O 5 produced. The possible role played by surface and heterogeneous effects in the pellet bed reactor is considered.

IntroductionEvidence suggests that the rate of cardiovascular implantable electronic device (CIED) infections is increasing more rapidly than the rates of CIED implantation and is associated with considerable mortality, morbidity and health economic impact. Antimicrobial surface treatments are being developed for CIEDs to reduce the risk of postimplantation infection within the subcutaneous implant pocket.Methods and analysisThe feasibility of processing cardiac pacemakers with the Agluna antimicrobial silver ion surface technology and in vivo biocompatibility were evaluated. Antimicrobially processed (n=6) and control pacemakers (n=6) were implanted into subcutaneous pockets and connected to a part of the sacrospinalis muscle using an ovine model for 12 weeks. Pacemaker function was monitored preimplantation and postimplantation.ResultsNeither local infection nor systemic toxicity were detected in antimicrobial or control devices, and surrounding tissues showed no abnormal pathology or over-reactivity. Semiquantitative scores of membrane formation, cellular orientation and vascularity were applied over five regions of the pacemaker capsule and average scores compared. Results showed no significant difference between antimicrobially processed and control pacemakers. Silver analysis of whole blood at 7 days found that levels were a maximum of 10 parts per billion (ppb) for one sample, more typically ≤2 ppb, compared with <<2 ppb for preimplantation levels, well below reported toxic levels.ConclusionsThere was no evidence of adverse or abnormal pathology in tissue surrounding antimicrobially processed pacemakers, or deleterious effect on basic pacing capabilities and parameters at 12 weeks. This proof of concept study provides evidence of basic biocompatibility and feasibility of applying this silver ion-based antimicrobial surface to a titanium pacemaker surface.