Long-term evaluation of geotechnical and environmental properties of ash-stabilised road.

In 2009, a low-volume gravel road in Sweden was stabilised using fly ash from a local paper mill. The objective was to examine whether fly ash could be used to enhance the stability of the road and how the nearby environment would be affected. The technical and environmental properties of the road have been monitored for two, six, and eleven years. Because the construction costs are higher for ash upgrading than for conventional upgrading, knowing for how long the improved properties will remain is relevant. Strength development was studied using a falling weight deflectometer and compressive strength tests. Environmental properties were studied by chemical analysis of road samples, soil, soil pore water, and vegetation. The results showed that the ash sections had higher stiffness than the reference sections. Leaching tests of road samples showed that the mobility of potassium, sodium, chloride, and sulfate decreased with time. Trace element concentrations in soil samples, except barium, were below the Swedish guideline values for sensitive land use. Chromium, lead, and copper were as high or even higher along the reference section than along the ash section. After 11 years, the pH closest to the ash section was slightly enhanced. Concentrations of zinc and cadmium in the soil pore water were the lowest closest to the ash road, although the total concentrations in the soil were at their highest at the same distance. No toxic levels of trace elements were found in the vegetation close to the road, although a clear difference was observed between plants from the ash section and the reference section, using multivariate data analysis. The positive effects on the geotechnical road properties from ash stabilisation remained after 11 years. The environmental impacts on nearby soil and vegetation can be considered low and acceptable. This study demonstrates that the use of biofuel fly ash in infrastructure projects can contribute to the circular economy and effective use of resources because the demand for pristine materials will be reduced.

Investigation into the effect of the general anaesthetic etomidate on local neuronal synchrony in the mouse neocortical slice.

How general anaesthetic drugs cause unconsciousness is a topic of ongoing clinical and scientific interest. It is becoming increasingly apparent that they disrupt cortical information processing, but the effects appear to depend on the spatial scale under investigation. In this study we investigated whether the intravenous anaesthetic etomidate synchronises neuronal activity on a sub-millimetre scale in mouse neocortical slices. In slices generating no-magnesium seizure-like event (SLE) field activity, we analysed the morphology of field potential activity recorded with 50µm extracellular electrodes. The analysis was based on the understanding that the amplitude and sheerness of field potential oscillations correlates with the synchrony of the underlying neural activity. When recorded from the region of the slice initiating SLE activity, etomidate consistently increased both population event amplitude (median(range) 85(24-350) to 101(30-427) µV) and slope 16.6(1.5-106.2) to 20.2(1.7-111.1) µV/ms (p=0.016 and p=0.0013, respectively). The results are consistent with an increase in neuronal synchrony within the receptive field of the recording electrode, estimated to be a circle diameter of 300µm. In conclusion, the neocortical slice preparation supports in vivo data showing that general anaesthetics increase neuronal synchrony on a local scale and provides an ideal model for investigating underlying mechanisms.

Investigation into the effect of the general anaesthetics etomidate and ketamine on long-range coupling of population activity in the mouse neocortical slice.

General anaesthetics have been hypothesised to ablate consciousness by decoupling intracortical neural connectivity. We explored this by investigating the effect of etomidate and ketamine on coupling of neural population activity using the low magnesium neocortical slice model. Four extracellular electrodes (50 µm) were positioned in mouse neocortical slices (400 µm thick) with varying separation. The effect of etomidate (24 µM) and ketamine (16 µM) on the timing of population activity recorded between channels was analysed. No decoupling was observed at the closest electrode separation of 0.2 mm. At 4mm separation, decoupling was observed in 50% and 42% of slices during etomidate and ketamine delivery, respectively (P<0.0001 and P=0.002, compared to 0.2 mm separation). A lower rate of decoupling was observed with 1mm separation (21% and 8%, respectively, P<0.03 for etomidate compared to 0.2mm separation). The data support the hypothesis that mechanistically diverse general anaesthetics disrupt neuronal connectivity across widely distributed intracortical networks.