The extraction of gold, coal, nickel, uranium, copper and other earth-moving activities almost always leads to environmental damage. In metal and coal extraction, exposure of sulfide minerals to the atmosphere leads to generation of acid rock drainage (ARD) and in underground mining to acid mine drainage (AMD) due to contamination of infiltrating groundwater. This study proposes to develop a reactive cover system that inhibits infiltration of oxygen and also releases alkalinity to increase the pH of generated ARD and attenuate metal contaminants at the same time. The reactive cover system is constructed using steel slag, a waste product generated from steel industries. This study shows that this type of cover system has the potential to reduce some of the adverse effects of sulfide mine waste disposal on land. Geochemical and geotechnical characterization tests were carried out. Different proportions of sulfide mine waste and steel slag were studied in leachate extraction tests. The best proportion was 33% of steel slag in dry weight. Other tests were conducted as follows: soil consolidation, saturated permeability and soil water characteristic curve. The cover system was numerically modeled through unsaturated flux analysis using Vadose/w. The solution proposed is an oxygen transport barrier that allows rain water percolation to treat the ARD in the waste rock pile. The results showed that the waste pile slope is an important factor and the cover system must have 5 m thickness to achieve an acceptable effectiveness.

Transcranial direct current stimulation (tDCS) might modulate neural activity and promote neural plasticity. This factorial randomized clinical trial compared a-tDCS on the left dorsolateral prefrontal cortex (l-DLPFC) or sham (s-tDCS), and a-tDCS or s-tDCS on the primary motor cortex (M1) in the connectivity analyses in eight regions of interest (ROIs) across eight resting-state electroencephalography (EEG) frequencies. We included 48 women with fibromyalgia, aged 30 to 65, randomly assigned to 2:1:2:1 to receive 20 sessions during 20 minutes of a-tDCS 2mA  or s-tDCS at home, over l-DLPFC or M1, respectively. EEG recordings were obtained before and after treatment with eyes open (EO) and eyes closed (EC). In the EC condition, comparing pre to post-treatment, the a-tDCS on l-DLPFC decreased the lagged coherence connectivity in the delta frequency band between the right insula and left anterior cingulate cortex (ACC) (t=-3.542, p=.048). The l-DLPFC a-tDCS compared to s-tDCS decreased the lagged coherence connectivity in the delta frequency band between the right insula and left ACC (t=-4.000, p=.017). In the EO condition, the l-DLPFC a-tDCS compared to M1 s-tDCS increased the lagged coherence connectivity between the l-DLPFC and left ACC in the theta band (t=-4.059, p=.048). Regression analysis demonstrated that the a-tDCS effect on the l-DLPFC was positively correlated with sleep quality, while a-tDCS on l-DLPFC and M1 s-tDCS were positively correlated with pain catastrophizing. The application of a-tDCS over the l-DLPFC has modulated the connectivity between various brain regions involved in the affective-attentional aspects of pain, especially at lower EEG frequencies during the resting state. These findings suggest that the effects of a-tDCS on neural oscillations could serve as a neural marker associated with its impact on fibromyalgia symptoms.

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