Substrate influence on aromatic plant growth in extensive green roofs in a Mediterranean climate

Green roofs have been described as technical solutions to overcome urban environmental problems, such as decrease of vegetation and stormwater management. In the present study, two pilot 20 m² extensive green roofs were implemented in an urban Mediterranean region, at a 1st storey on a warehouse building structure, in order to test the adequacy of different substrates for supporting aromatic plants (Lavandula dentata, Helichrysum italicum, Satureja montana, Thymus caespititius and Thymus pseudolanuginosus). Experimental substrates included expanded clay and granulated cork as main components, supplemented with organic matter and crushed egg shell. A commercial substrate that obeys to FLL guidelines was also tested. Plant growth was assessed and compared within each platform. All experimental substrates proved to be adequate for vegetation growth, with the combination of 70% expanded clay, 15% organic matter and 15% crushed egg shell showing the best results regarding plant establishment and growth over time. Water runoff quality parameters - turbidity, pH, conductivity, NH₄ ⁺, NO₃ ^?, PO₄ ^3? - met standard values required for water reuse for non-potable purposes, such as toilet flushing or irrigation. Preliminary qualitative thermographic measurements comparing surface temperature of different plant species and the substrate showed that temperature of vegetation surface was lower than substrate, reinforcing green roofs benefits of lowering air temperature in their surroundings. The present research shows that aromatic vegetation combined with clay substrates are suitable for green roofs located in countries of the Mediterranean region.     

Élaboration et validation d'un questionnaire sur le travail décent

Les auteurs cherchent à élaborer un outil de mesure du travail décent reposant sur un questionnaire inédit axé sur les perceptions des travailleurs. Les items proposés se fondent sur les «éléments fondamentaux» du travail décent selon l'OIT. Une première version de soixante‐douze items est administrée sur deux grands échantillons au Portugal et au Brésil. Les analyses factorielles exploratoire et confirmatoire menées sur cette base permettent d'isoler sept facteurs spécifiques et un facteur global du travail décent. Avec de bons coefficients de fiabilité et une bonne validité convergente et discriminante, le questionnaire proposé ouvre la voie à de nouvelles études empiriques dans le domaine.     

Estimation of the maximal moment exponent with censored data

Heavy-tailed distributions have been used to model phenomena in which extreme events occur with high probability. In these type of occurrences, it is likely that extreme events are not observable after a certain threshold. Appropriate estimators are needed to deal with this type of censored data. We show that the well-known Hill-Hall estimator is unable to deal with censored data and yields highly biased estimates. We propose and study an unbiased modified maximum likelihood estimator, as well as a truncated tail regression estimator. We assess the expected value and the variance of these estimators in the cases of stable- and Pareto-distributed data.