Steady-state sound propagation through hot exhaust jets in cooler cross-flow: A computational study.

An analysis has been carried out to investigate the sound radiation through a heated jet in cooler cross-flow, which is representative of many industrial exhaust systems, using a hybrid steady-state computational fluid dynamics and computational acoustic model. The mean flow and temperature fields are modelled using steady-state computational fluid dynamics, with the turbulence modelled using Reynolds Averaged Navier-Stokes equations. The corresponding mean flow and temperature fields are used in the computational sound propagation model using linearised acoustic wave equation with mean flow based on a scalar flow potential. The results obtained from the computational simulations show that the flow significantly changes the sound propagation path and that the sound levels downstream of the duct outlet are higher than expected from using an acoustic monopole radiation pattern. The dominant mechanism affecting the propagation of sound is the refraction arising from the plume's temperature and velocity gradients. The sound propagation is highly dependent on the proximity from the duct outlet, normalised wavenumber, temperature and the jet to cross-flow mean velocity ratio. This computational study builds upon previous experimental work to analyse the fluid-acoustic interaction for heated jets in cooler cross-flow to understand the complex radiation pattern that leads to higher-than-expected sound levels downstream of the duct outlet.

Antioxidant and antifungal activities of marrubiin, extracts and essential oil from Marrubium vulgare L. against pathogenic dermatophyte strains.

OBJECTIVE: Medicinal plants extracts and plant-derived compounds are one of the natural sources for discovering new antifungal agents, the objectives of this work were to investigate for the first time the antidermatophytic, antipathogenic activities of methanol, acetone extracts, and essential oil of Marrubium vulgare L. grown in Tunisia and its active compound marrubiin on pathogenic for animals and humans, such as some dermatophytes and pathogenic for plants, and to evaluate antioxidant activities of different extracts with consideration to their chemical compositions. MATERIAL AND METHODS: Acetone and methanol extracts were evaluated by HPLC, the essential oil was also analyzed by GC/MS. PCL assay was used to determine the antioxidant activity. RESULTS: Results showed that methanol and acetone extracts exhibited a significant antioxidant activity (261.41 and 272.90µmol TE/g respectively), while the lowest one was observed in the case of marrubiin and essential oil. The antifungal activity of different extracts, marrubiin and essential oil at two concentrations (20 and 100µg/mL) were screened against the dermatophytes fungi Microsporum gypseum, Microsporum canis, Arthroderma cajetani, Trichophyton mentagrophytes, Trichophyton tonsurans, Epidermophyton floccosum and against two fungi strains (Botrytis cinerea, Pythium ultimum). Among tested extracts, marrubiin at 100µg/mL showed about 50% inhibition for T. mentagrophytes and E. floccosum. The anti-phytopathogenic activity was also carried out, only marrubiin had in activity against B. cinerea at the highest dose (32.40%), while methanol extract of M.vulgare and marrubiin are able to increase the mycelial growth of P. ultimum at the highest concentration (45.15 and 40.30% respectively). CONCLUSION: In our study, we conclude that M.vulgare and marrubiin can be used as natural antioxidants and antifungal agent for treatment of skin dermatophyte infections.

Is climate change a threat for water uses in the Mediterranean region? Results from a survey at local scale.

Water scarcity and water security are linked, not only through the direct effects of water shortages on each water users' access to water, but also because of water conflicts generated. Climate change is predicted to raise temperatures in the Mediterranean region and reduce rainfall, leading to a reduction in water yield and possibly worsening the situation of water resource shortages that Mediterranean regions are already experiencing. In its dissemination strategy, the EU FP7 CLIMB project addressed water security threats through an analysis of water uses and water use rivalries within a few target catchments distributed over the Mediterranean region. The present work explores whether climate change is locally perceived by stakeholders (water users and managers) as a key issue for their water uses and water security. Individual interviews, meetings, and compilation of questionnaires were conducted at five sites located in the Mediterranean region. The methodology permitted an analysis of water use and its evolution in the water management context, an identification of the state of awareness of local stakeholders and of the pressures on water use and water use rivalries, and a prioritization of water uses. Currently, the main response to increasing water demand in the Mediterranean region, while not yet considering climate change as a driving force, is a progressive externalization of water resources, with limits represented by national borders and technological possibilities. Overall, 'climate change' was not mentioned by stakeholders during both interviews and in answers to the questionnaires. Even the prospect of decreasing precipitation was not considered a relevant or threatening issue in the coming 20years. This confirms the need to continue all efforts to disseminate the state of knowledge on climate change impacts in the Mediterranean region, such as water scarcity, especially to local water managers, as initiated by various research programs of the European Commission.