Moringa oleifera plasticity to face climatic changes

Extreme abiotic factors, such drought combined with heat waves and/or high UVB radiation are predicted to become more frequent in the future. The impact on plant production of these challenges on multipurpose Moringa oleifera L. remains unclear. A susceptibility of this species may lead to increase poverty in endangered regions. M. oleifera is a woody species native from sub-Himalaya regions under high climate stress pressure. The interest on this species is emerging due to its several medicinal properties and its nutritional value. Agropharmaceutical industry is interest in this species too. To understand the impact of increased climate factors, young (2 months old) plants of this species were exposed to water deficit (WD) and UVB (alone or combined). WD and WD+UVB imposition consists of unwater for 4 days. After 1 day withholding water, UVB and WD+UVB were irradiated with 26.3 kJ m-2 distributed per 3 days. Immediately after treatment exposition (1 day) and after 10 days, plant water status, growth, carbon metabolism and oxidative stress were measured. Overall no significant differences were observed in WD, regarding the parameters analysed, except on gas exchanges, MDA and phenols. The plants exposed to UVB showed, in general, more severe effects, as higher pigment content, MDA and membrane permeability, while no changes were observed in the total antioxidant activity. Plants exposed to UVB+WD, despite changes observed, the impact was lower than the one observed in UVB exposed plants, meaning that a protective/adaptive mechanism was developed in the plants under combined stressors. On the other hand, in all treatments the net CO2 assimilation rate decreased. Results suggest that M. oleifera has some tolerance to WD and UVB, and that develops mechanism of adaptation to these two types of stress that often arise in combination under a climate change scenario.

Materials and concepts for CO2 lean ironmaking by pyroelectrolysis

The main purpose of this PhD thesis was to provide convincing demonstration for a breakthrough concept of pyroelectrolysis at laboratory scale. One attempted to identify fundamental objections and/or the most critical constraints, to propose workable concepts for the overall process and for feasible electrodes, and to establish the main requirements on a clearer basis. The main effort was dedicated to studying suitable anode materials to be developed for large scale industrial units with molten silicate electrolyte. This concept relies on consumable anodes based on iron oxides, and a liquid Fe cathode, separated from the refractory materials by a freeze lining (solid) layer. In addition, one assessed an alternative concept of pyroelectrolysis with electron blocking membranes, and developed a prototype at small laboratory scale. The main composition of the molten electrolyte was based on a magnesium aluminosilicate composition, with minimum liquidus temperature, and with different additions of iron oxide. One studied the dynamics of devitrification of these melts, crystallization of iron oxides or other phases, and Fe2+/Fe3+ redox changes under laser zone melting, at different pulling rates. These studies were intended to provide guidelines for dissolution of raw materials (iron oxides) in the molten electrolyte, to assess compatibility with magnetite based consumable anodes, and to account for thermal gradients or insufficient thermal management in large scale cells. Several laboratory scale prototype cells were used to demonstrate the concept of pyroelectrolysis with electron blocking, and to identify the most critical issues and challenges. Operation with and without electron blocking provided useful information on transport properties of the molten electrolyte (i.e., ionic and electronic conductivities), their expected dependence on anodic and cathodic overpotentials, limitations in faradaic efficiency, and onset of side electrochemical reactions. The concept of consumable anodes was based on magnetite and derived spinel compositions, for their expected redox stability at high temperatures, even under oxidising conditions. Spinel compositions were designed for prospective gains in refractoriness and redox stability in wider ranges of conditions (T, pO2 and anodic overpotentials), without excessive penalty for electrical conductivity, thermomechanical stability or other requirements. Composition changes were also mainly based on components of the molten aluminosilicate melt, to avoid undue contamination and to minimize the dissolution rate of consumable anodes. Additional changes in composition were intended for prospective pyroelectrolysis of Fe alloys, with additions of different elements (Cr, Mn, Ni, Ti).