Advances in the use of biological stabilisers and hyper-compaction for sustainable earthen construction materials.

In the majority of cases, earthen construction materials for real buildings require amendment to deliver suitable material properties, which could be some additional strength or resilience to erosion. In modern earthen construction, in India, Australia and other parts of the world, cement and lime have been successfully used as stabilisers, providing both strength and durability benefits. However, the use of cement is detrimental to the green credentials of earthen construction materials, due to the large carbon footprint of that material’s manufacture and, for some time, researchers have been motivated to find more appropriate stabilisers and manufacturing methods. In this paper, we present recent findings from two projects that are linked by this motivation, and involve the study of bio-based stabilisers and alternative manufacturing methods for insitu and unit-based materials. Results are presented from laboratory testing of strength and durability of a range of materials, bio-stabilisers and manufacturing processes, indicating that there could be viable alternatives to cement and lime, certainly for many current uses of earthen construction materials

Population Genomic Analysis of a Bacterial Plant Pathogen: Novel Insight into the Origin of Pierce's Disease of Grapevine in the U.S.

Invasive diseases present an increasing problem worldwide; however, genomic techniques are now available to investigate the timing and geographical origin of such introductions. We employed genomic techniques to demonstrate that the bacterial pathogen causing Pierce's disease of grapevine (PD) is not native to the US as previously assumed, but descended from a single genotype introduced from Central America. PD has posed a serious threat to the US wine industry ever since its first outbreak in Anaheim, California in the 1880s and continues to inhibit grape cultivation in a large area of the country. It is caused by infection of xylem vessels by the bacterium Xylella fastidiosa subsp. fastidiosa, a genetically distinct subspecies at least 15,000 years old. We present five independent kinds of evidence that strongly support our invasion hypothesis: 1) a genome-wide lack of genetic variability in X. fastidiosa subsp. fastidiosa found in the US, consistent with a recent common ancestor; 2) evidence for historical allopatry of the North American subspecies X. fastidiosa subsp. multiplex and X. fastidiosa subsp. fastidiosa; 3) evidence that X. fastidiosa subsp. fastidiosa evolved in a more tropical climate than X. fastidiosa subsp. multiplex; 4) much greater genetic variability in the proposed source population in Central America, variation within which the US genotypes are phylogenetically nested; and 5) the circumstantial evidence of importation of known hosts (coffee plants) from Central America directly into southern California just prior to the first known outbreak of the disease. The lack of genetic variation in X. fastidiosa subsp. fastidiosa in the US suggests that preventing additional introductions is important since new genetic variation may undermine PD control measures, or may lead to infection of other crop plants through the creation of novel genotypes via inter-subspecific recombination. In general, geographically mixing of previously isolated subspecies should be avoided

The phylogenetic landscape and nosocomial spread of the multidrug-resistant opportunist Stenotrophomonas maltophilia

yesRecent studies portend a rising global spread and adaptation of human- or healthcare- associated pathogens. Here, we analyse an international collection of the emerging, multi-drug-resistant, opportunistic pathogen Stenotrophomonas maltophilia from 22 countries to infer population structure and clonality at a global level. We show that the S. maltophilia complex is divided into 23 monophyletic lineages, most of which harbour strains of all degrees of human virulence. Lineage Sm6 comprises the highest rate of human-associated strains, linked to key virulence and resistance genes. Transmission analysis identifies potential outbreak events of genetically closely related strains isolated within days or weeks in the same hospitals

Effect of water content on noise attenuation over vegetated roofs:Results from two field studies

\u3cp\u3eUrban traffic noise is mitigated when propagating over vegetated roofs. It is known from results of laboratory measurements that the sound absorption performance of vegetated roofs is affected by its substrate water content. In a previous study on one extensive green roof, a significant decrease of noise attenuation was found when the substrate water content increased, specifically in the frequency range between 250 Hz and 1250 Hz. This work presents new results from long-lasting in-situ experiments on two extensive vegetated roofs in Eindhoven (Netherlands), together with two different methods for obtaining the results. One scenario involves traffic noise and an artificial noise source is used in the other scenario. The sound pressure level differences over the vegetated roofs, substrate water content and meteorological conditions are measured and collected. Although a descending tendency of noise attenuation with the increase of the substrate water content as in previous research can be confirmed, the extent and frequency of this effect vary significantly between the two vegetated roofs, specifically between 400 Hz and 2000 Hz on the Cascade roof and between 800 Hz and 1000 Hz on the Strijp-S roof.\u3c/p\u3

Determination of the impedance of vegetated roofs with a double-layer Miki model

Vegetated roof systems on the top of buildings can act as absorbers for traffic noise mitigation. Recent research explains the properties of vegetated roofs that are important for their sound absorptive and scattering properties. Although it has been identified that the substratum is the major contributor to the acoustic absorption of a vegetated roof, coverage of this substratum by plants may have a significant effect on the acoustic absorption. Short-range acoustic propagation experiments have previously been used for in-situ measurements to determine the acoustic impedance of surfaces as forest floors, grasslands, and gravel. However, it is still less practical to estimate the impedance of a non-locally reacting layer of leaves on substratum using the proposed method. The Miki model provides a satisfactory prediction of the fundamental acoustic properties of soils, plants, and their combinations with the advantage of computational simplicity. Here, the double-layer Miki model is examined based on the short-range acoustic propagation method over substratum (with and without layer of leaves) in the laboratory, and considered through in-situ outdoor measurements over green roofs. In addition, the application of the double-layer Miki model on the prediction of the non-locally reacting surface impedance is evaluated by a comparison with other impedance models

A Single Dose of Azithromycin Does Not Improve Clinical Outcomes of Children Hospitalised with Bronchiolitis: A Randomised, Placebo-Controlled Trial

Objective:Bronchiolitis, one of the most common reasons for hospitalisation in young children, is particularly problematic in Indigenous children. Macrolides may be beneficial in settings where children have high rates of nasopharyngeal bacterial carriage and frequent prolonged illness. The aim of our double-blind placebo-controlled randomised trial was to determine if a large single dose of azithromycin (compared to placebo) reduced length of stay (LOS), duration of oxygen (O2) and respiratory readmissions within 6 months of children hospitalised with bronchiolitis. We also determined the effect of azithromycin on nasopharyngeal microbiology.Methods:Children aged ≤18 months were randomised to receive a single large dose (30 mg/kg) of either azithromycin or placebo within 24 hrs of hospitalisation. Nasopharyngeal swabs were collected at baseline and 48hrs later. Primary endpoints (LOS, O2) were monitored every 12 hrs. Hospitalised respiratory readmissions 6-months post discharge was collected.Results:97 children were randomised (n = 50 azithromycin, n = 47 placebo). Median LOS was similar in both groups; azithromycin = 54 hours, placebo = 58 hours (difference between groups of 4 hours 95%CI -8, 13, p = 0.6). O2 requirement was not significantly different between groups; Azithromycin = 35 hrs; placebo = 42 hrs (difference 7 hours, 95%CI -9, 13, p = 0.7). Number of children re-hospitalised was similar 10 per group (OR = 0.9, 95%CI 0.3, 2, p = 0.8). At least one virus was detected in 74% of children. The azithromycin group had reduced nasopharyngeal bacterial carriage (p = 0.01) but no difference in viral detection at 48 hours.Conclusion:Although a single dose of azithromycin reduces carriage of bacteria, it is unlikely to be beneficial in reducing LOS, duration of O2 requirement or readmissions in children hospitalised with bronchiolitis. It remains uncertain if an earlier and/or longer duration of azithromycin improves clinical and microbiological outcomes for children. The trial was registered with the Australian and New Zealand Clinical Trials Register. Clinical trials number: ACTRN12608000150347. http://www. anzctr.org.au/TrialSearch.aspx