Atmospheric corrosion in the Canary Islands

Corrosion is a process that occurs naturally and irreversibly. It is defined as the deterioration of a material (usually a metal) due to its interaction with the surrounding environment. Economic losses related to corrosive processes account for about 5% of the Gross National Product (GNP) of Western countries, China and India. Only in the United States, the costs related to metal corrosion are estimated at app. $1,000 annual per capita, and responsible for a substantial portion of this cost is atmospheric corrosion. Within the various types of corrosive processes, atmospheric corrosion attracts great interest since it affects the entirety of metal materials exposed to air, including urban and industrial infrastructures. It is a widelystudied process, and there are national and international standardized norms for its characterization classifying the aggressiveness of a given environment for a specific metal type (usually those most widely used by the industry). However, major discrepancies between the results of direct exposure and those obtained from the application of standardized norms and predictive models occur for fragmented geographical areas, as in the case of archipelagos. In the Canary Islands, due to their characteristic orography and the regime of winds that affects the archipelago, a multitude of microclimates is generated in a very small geographical area. This variability of atmospheric environments in different islands means, even for the same metal, that the extent of the atmospheric attack may vary substantially between two locations separated only a few miles away. This fact imposes the need for the development of specific prediction models to characterize the corrosion rate for different metals. Investigations carried out in the Canary Islands allowed the characterization of the atmospheric corrosion for metals of wide industrial use (namely mild steel, galvanized steel, zinc, copper, and aluminium), and to obtain maps of atmospheric corrosivity for all the islands. Specific mathematical models have been developed for the prediction of the corrosion rates for these metals exposed on the various islands that make up the archipelag

Fluoride removal from natural volcanic underground water by an electrocoagulation process: Parametric and cost evaluations

The water supply on the island of Tenerife (Canary Islands, Spain) comes mainly from aquifers of volcanic origin that are notable for the high content of fluorides that make it unviable for human consumption without prior conditioning treatment. The treatments that generate a high rejection of water are not viable, since water is a scarce natural resource of high value. An electrocoagulation process was investigated as a method to treat natural groundwater from volcanic soils containing a dangerously high fluoride content. The operating parameters of an electrocoagulation reactor model with parallel plate aluminum electrodes were optimized for batch and continuous flow operations. In the case of batch operation, it was found that acidification of the water improved fluoride elimination efficiency, with a maximum at pH 3. Yet, operation at the natural pH of the water achieved elimination efficiencies between 82 and 92% depending on the applied current density. An optimum current density of 5 mA/cm2 was found in terms of the highest removal efficiency, and the kinetics of fluoride removal was adjusted to a pseudo-second-order kinetics. In the continuous-flow operation, with an optimal residence time of 10 min and a separation of 0.5 cm between the electrodes, it was observed that the current density that would be applied would depend on the initial concentration of fluoride in the raw water. Then, an initial fluoride concentration of 6.02 mg/L required a current density > 7.5 mA/cm2 to comply with the legal guidelines in the product water, while for an initial concentration of 8.98 mg/L, the optimum current density was 10 mA/cm2. Under these operating conditions, the operating costs will vary between 0.20 and 0.26 €/m3 of treated wate

Flower Development

Flowers are the most complex structures of plants. Studies of Arabidopsis thaliana, which has typical eudicot flowers, have been fundamental in advancing the structural and molecular understanding of flower development. The main processes and stages of Arabidopsis flower development are summarized to provide a framework in which to interpret the detailed molecular genetic studies of genes assigned functions during flower development and is extended to recent genomics studies uncovering the key regulatory modules involved. Computational models have been used to study the concerted action and dynamics of the gene regulatory module that underlies patterning of the Arabidopsis inflorescence meristem and specification of the primordial cell types during early stages of flower development. This includes the gene combinations that specify sepal, petal, stamen and carpel identity, and genes that interact with them. As a dynamic gene regulatory network this module has been shown to converge to stable multigenic profiles that depend upon the overall network topology and are thus robust, which can explain the canalization of flower organ determination and the overall conservation of the basic flower plan among eudicots. Comparative and evolutionary approaches derived from Arabidopsis studies pave the way to studying the molecular basis of diverse floral morphologies