ALBERT

Description: The Gulf of Cadiz seismicity is characterized by persistent low to intermediate magnitude earthquakes, occasionally punctuated by high magnitude events such as the M ~ 8.7 1755 Great Lisbon earthquake and the M = 7.9 event of February 28th, 1969. Micro-seismicity was recorded during 11 months by a temporary network of 25 ocean bottom seismometers (OBSs) in an area of high seismic activity, encompassing the potential source areas of the mentioned large magnitude earthquakes. We combined micro-seismicity analysis with processing and interpretation of deep crustal seismic reflection profiles and available refraction data to investigate the possible tectonic control of the seismicity in the Gulf of Cadiz area. Three controlling mechanisms are explored: i) active tectonic structures, ii) transitions between different lithospheric domains and inherited Mesozoic structures, and iii) fault weakening mechanisms. Our results show that micro-seismicity is mostly located in the upper mantle and is associated with tectonic inversion of extensional rift structures and to the transition between different lithospheric/rheological domains. Even though the crustal structure is well imaged in the seismic profiles and in the bathymetry, crustal faults show low to negligible seismic activity. A possible explanation for this is that the crustal thrusts are thin-skinned structures rooting in relatively shallow sub-horizontal décollements associated with (aseismic) serpentinization levels at the top of the lithospheric mantle. Therefore, co-seismic slip along crustal thrusts may only occur during large magnitude events, while for most of the inter-seismic cycle these thrusts remain locked, or slip aseismically. We further speculate that high magnitude earthquake's ruptures may only nucleate in the lithospheric mantle and then propagate into the crust across the serpentinized layers.

Description: This paper presents a backward Euler stabilized-based control strategy applied to a neutral point clamped (NPC) back-to-back connected five level converters. A generalized method is used to obtain the back-to-back NPC converter system model. The backward Euler stabilized-based control strategy uses one set of calculations to compute the optimum voltage vector needed to reach the references and to balance the voltage of the DC-bus capacitors. The output voltage vector is selected using a modified cost functional that includes variable tracking errors in the functional weights, whereas in classic approaches, the weights are considered constant. The proposed modified cost functional enables AC current tracking and DC-bus voltage balancing in a wide range of operating conditions. The paper main contributions are: (i) a backward Euler stabilized-based control strategy applied to a double, back-to-back connected, five level NPC converter; (ii) the use of cost functional weight varying as a function of the controlled variable tracking errors to enforce the controlled variables and to balance the DC capacitor voltages; and (iii) the demonstration of system feasibility for this type of converter topology and control strategy, ensuring a high enough computational efficiency and extending the modulation index from 0.6 to 0.93. Experimental results are presented using a prototype of a five level NPC back-to-back converter.

Description: Chromium (Cr) contamination in arable soils and irrigating water remains a priority, particularly due to the challenges posed to crop production and food safety. Long-term Cr(VI) effects remain less addressed than short-term ones, particularly regarding organ-specific genotoxic profiles. Here we used the crop Lactuca sativa growing in a protected horticultural system and irrigated for 21 days with Cr(VI) (up to 200 mg/L). Besides the oxidative stress, the genotoxicity was evaluated. Shoots and roots showed distinctive oxidative stress status and genotoxic effects, in a dose-dependent manner. While 50 mg/L stimulated antioxidant activities and no major genotoxic effects were found, plants exposed to ≥150 showed an increase of oxidative disorders, together with cytostatic and DNA damage effects, and some mitotic impairment. Leaves showed less oxidative signs at 50 mg/L, while at 150/200 mg/L the antioxidant battery was stimulated. In Cr treated plants, the highest dose increased the DNA damage, reinforcing the idea that DNA breaks were related to mitotic disorders in higher doses. In conclusion, long-term exposure data show a highly responsive root, with a quadratic response meaning higher defenses at lower Cr doses, and higher oxidative and DNA damage and cytostatic effect at a higher dose.