Efficient Statistical Model for Predicting Electromagnetic Wave Distribution in Coupled Enclosures

The random coupling model (RCM) has been successfully applied to predicting the statistics of currents and voltages at ports in complex electromagnetic (EM) enclosures operating in the short-wavelength limit. Recent studies have extended the RCM to systems of multimode aperture-coupled enclosures. However, as the size (as measured in wavelengths) of a coupling aperture grows, the coupling matrix used in the RCM increases as well, and the computation becomes more complex and time consuming. A simple power balance (PWB) model can provide fast predictions for the averaged power density of waves inside electrically large systems for a wide range of cavity and coupling scenarios. However, the important interference-induced fluctuations of the wave field retained in the RCM are absent in the PWB model. Here we aim to combine the best aspects of each model to create a hybrid treatment and study the EM fields in coupled enclosure systems. The proposed hybrid approach provides both mean and fluctuation information of the EM fields without the full computational complexity of the coupled-cavity RCM. We compare the hybrid model predictions with experiments on linear cascades of over-moded cavities. We find good agreement over a set of different loss parameters and for different coupling strengths between cavities. The range of validity and applicability of the hybrid method are tested and discussed

Cyanobacterial lipopolysaccharides and human health – a review

Cyanobacterial lipopolysaccharide/s (LPS) are frequently cited in the cyanobacteria literature as toxins responsible for a variety of heath effects in humans, from skin rashes to gastrointestinal, respiratory and allergic reactions. The attribution of toxic properties to cyanobacterial LPS dates from the 1970s, when it was thought that lipid A, the toxic moiety of LPS, was structurally and functionally conserved across all Gram-negative bacteria. However, more recent research has shown that this is not the case, and lipid A structures are now known to be very different, expressing properties ranging from LPS agonists, through weak endotoxicity to LPS antagonists. Although cyanobacterial LPS is widely cited as a putative toxin, most of the small number of formal research reports describe cyanobacterial LPS as weakly toxic compared to LPS from the Enterobacteriaceae. We systematically reviewed the literature on cyanobacterial LPS, and also examined the much lager body of literature relating to heterotrophic bacterial LPS and the atypical lipid A structures of some photosynthetic bacteria. While the literature on the biological activity of heterotrophic bacterial LPS is overwhelmingly large and therefore difficult to review for the purposes of exclusion, we were unable to find a convincing body of evidence to suggest that heterotrophic bacterial LPS, in the absence of other virulence factors, is responsible for acute gastrointestinal, dermatological or allergic reactions via natural exposure routes in humans. There is a danger that initial speculation about cyanobacterial LPS may evolve into orthodoxy without basis in research findings. No cyanobacterial lipid A structures have been described and published to date, so a recommendation is made that cyanobacteriologists should not continue to attribute such a diverse range of clinical symptoms to cyanobacterial LPS without research confirmation

Extending membrane longevity by using MIEX as a pre-treatment

The use of membrane technology and in particular microfiltration (MF) is becoming more popular as a water treatment technology. The operational lifetime of MF membranes can be reduced by natural organic matter (NOM) which is a known foulant. The MIEX DOC (Magnetic Ion EXchange for Dissolved Organic Carbon removal) process was developed to remove NOM from raw water sources. It was anticipated that a reduction in NOM resulting from the MIEX DOC process would also improve the performance of MF systems. A pilot plant study was undertaken to directly measure the impact of MIEX pre-treatment on MF performance. A long term study with a regular cleaning strategy revealed little benefit in MIEX pre-treatment to improve the lifetime of the MF membrane. However, by applying less frequent cleaning it was immediately apparent that fouling was occurring at a faster rate without MIEX pre-treatment. Further studies showed that irreversible fouling also occurred at a faster rate on the membrane without pre-treatment.M. B. Dixon, J. Y. Morran and M. Drika