The elaboration of indices to assess biological water quality. A case study

Here we tested the application of a nodal analysis for the elaboration of biotic indices for particular stressing conditions. The work was carried out in an intermittent Mediterranean stream where superficial flow was absent during summer. The river was perturbed by an effluent with high pH, sulphates, nitrates and conductivity. "Summer" and "winter" samples were treated separately. We first identified groups of sites differing in taxonomical composition by cluster analysis. Then we tested whether groups of sites also differed in their abiotic characteristics. In the following step, groups of cooccurring taxa were also identified by cluster analysis. The indicator value of a taxa group was measured by fidelity measurements for site groups. Indicator taxa were incorporated in a water quality table. The biotic index in the water quality table clearly discriminated impacted from reference sites in the two following years and was correlated with the first axis of a correspondence analysis biplot which also discriminated impacted from clean sites. We suggest that nodal analysis can be a reliable technique for the identification of bioindicators and the elaboration of biotic indices.http://www.sciencedirect.com/science/article/B6V73-3SX5H1V-F/1/2ddcd6137e173976c270b458bbb4c99

The elaboration of indices to assess biological water quality. A case study

Here we tested the application of a nodal analysis for the elaboration of biotic indices for particular stressing conditions. The work was carried out in an intermittent Mediterranean stream where superficial flow was absent during summer. The river was perturbed by an effluent with high pH, sulphates, nitrates and conductivity. "Summer" and "winter" samples were treated separately. We first identified groups of sites differing in taxonomical composition by cluster analysis. Then we tested whether groups of sites also differed in their abiotic characteristics. In the following step, groups of cooccurring taxa were also identified by cluster analysis. The indicator value of a taxa group was measured by fidelity measurements for site groups. Indicator taxa were incorporated in a water quality table. The biotic index in the water quality table clearly discriminated impacted from reference sites in the two following years and was correlated with the first axis of a correspondence analysis biplot which also discriminated impacted from clean sites. We suggest that nodal analysis can be a reliable technique for the identification of bioindicators and the elaboration of biotic indices.http://www.sciencedirect.com/science/article/B6V73-3SX5H1V-F/1/2ddcd6137e173976c270b458bbb4c99

Generalised Space-time and Gauge Transformations

We consider the generalised space-time introduced by the author in 2003 in the context of the non-linear realisation of the semi-direct product of E11 and its first fundamental representation. For all the fields we propose gauge transformations which are compatible with the underlying E11 structure. A crucial role is played by the generalised vielbein that the generalised space-time possess. We work out the explicit form of the gauge transformations, at low levels, in four, five and eleven dimensions.Comment: 33 page

Evidences of exopolysaccharide production by Helicobacter pylori submitted to hydrodynamic stress

Helicobacter pylori is a widespread Gram-negative bacterium that infects the stomach of humans leading to the onset of several gastric disorders, such as gastritis, gastric ulcers, and cancers. The transmission of H. pylori remains unclear but two different pathways have been suggested: faecal-oral and oraloral. It has been reported that H. pylori has the ability to incorporate in biofilms formed on water-exposed surfaces thus providing a route of infection. On the other hand, a polysaccharide-containing biofilm has been observed at the air-liquid interface when H. pylori is grown in a glass fermenter1. Because exopolysaccharides (EPS) play a determinant role in bacterial adhesion by conferring protection against adverse conditions such as starvation and environmental aggressions, EPS production would be expected to be higher if the bacterium is exposed to water. In this work the capability of H. pylori to produce EPS when exposed to water and under hydrodynamic stress has been evaluated. H. pylori was inoculated in autoclaved distilled water and allowed to stand under gentle stirring at room temperature. The significant and continuous increase in the sugar content 192 hours after inoculation suggests the production of exopolysaccharides. This evidence is reinforced by epiflourescence microscopical observation of the bacteria stained with DAPI (4,6-diamidino-2-phenylindole) that revealed the presence of bacterial aggregates 318 hours after inoculation

Exopolysaccharide production by Helicobacter pylori

Helicobacter pylori is a widespread Gram-negative bacterium that infects the stomach of humans leading to the onset of several gastric disorders, such as, gastritis, gastric ulcers, and cancers. Studies from developing countries with low socioeconomic status and poor management of the drinking water suggest that it may serve as an environmental reservoir of H. pylori and therefore contribute to human infection. It has been reported that H. pylori has the ability to form microbial consortia embedded by a highly hydrated exopolysaccharidic matrix (biofilms) on surfaces exposed to water. The enhanced protection provided to microbial cells by the exopolysaccharides (EPS) brings added concerns about the possibility of H. pylori being transmitted through drinking water. H. pylori EPS as been reported to be composed mainly by Gal:Glc:GlcN in a proportion of 1.0:2.1:7.0, respectively (Stark et al., 1999). The present work brings about microscopical evidences of the capability of H. pilory to form free swimming bacterial aggregates and biofilms when submitted to nutrient depletion and hydrodynamic stress. Evidences that H. pylori aggregation is an exopolysaccharidic mediated phenomena both in planktonic and sessile states are also showed. Ethanol fractioning of the material recovered from these aggregates revealed an EPS composed of Gal:Glc:GlcN in a proportion of 1.0:0.4:1.6 respectively. A further structural detail about this EPS is under progress

Financial cycles with heterogeneous intermediaries

We develop a dynamic macroeconomic model with heterogeneous financial intermediaries and endogenous entry. Time-varying endogenous macroeconomic risk arises from the risk-shifting behaviour of the cross-section of financial intermediaries. When interest rates are high, a decrease in interest rates stimulates investment and decreases aggregate risk. In contrast, when they are low, further stimulus can increase financial instability while inducing a fall in the risk premium. In this case, there is a trade-off between stimulating the economy and financial stability. This provides a model of the risk-taking channel of monetary policy

Green Microalgae Scenedesmus Obliquus Utilization for the Adsorptive Removal of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) from Water Samples

In view of the valorisation of the green microalga Scenedesmus obliquus biomass, it was used for the biosorption of two nonsteroidal anti-inflammatory drugs, namely salicylic acid and ibuprofen, from water. Microalgae biomass was characterized, namely by the determination of the point of zero charge (pHPZC), by Fourier transform infrared (FT-IR) analysis, simultaneous thermal analysis (STA) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Kinetic and equilibrium batch experiments were carried out and results were found to fit the pseudo-second order equation and the Langmuir isotherm model, respectively. The Langmuir maximum capacity determined for salicylic acid (63 mg g−1) was larger than for ibuprofen (12 mg g−1), which was also verified for a commercial activated carbon used as reference (with capacities of 250 and 147 mg g−1, respectively). For both pharmaceuticals, the determination of thermodynamic parameters allowed us to infer that adsorption onto microalgae biomass was spontaneous, favourable and exothermic. Furthermore, based on the biomass characterization after adsorption and energy associated with the process, it was deduced that the removal of salicylic acid and ibuprofen by Scenedesmus obliquus biomass occurred by physical interaction.The Fundação para a Ciência e a Tecnologia (FCT, Lisboa, Portugal) is acknowledged for support through the FCT Investigator Program (IF/00314/2015) and for Andreia Silva’s Ph.D. Grant SFRH/BD/138/780/2018. Thanks are due to FCT/ Ministério da Ciência, Tecnologia e Ensino Superior (MCTES), for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020), through national funds. Likewise, the financial support of the Associate Laboratory for Green Chemistry-LAQV through national funds from FCT/MCTES (UIDB/50006/2020) is acknowledged, co-financed by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007265). This research was funded also by the EU and FCT/UEFISCDI/FORMAS, in the frame of the collaborative international consortium REWATER financed under the ERA-NET Cofund WaterWorks2015 Call, this ERA-NET is an integral part of the 2016 Joint Activities developed by the Water Challenges for a Changing World Joint Program Initiative (Water JPI).info:eu-repo/semantics/publishedVersio