About the role of visual field defects in pure alexia

Pure alexia is an acquired reading disorder characterized by a disproportionate prolongation of reading time as a function of word length. Although the vast majority of cases reported in the literature show a right-sided visual defect, little is known about the contribution of this low-level visual impairment to their reading difficulties. The present study was aimed at investigating this issue by comparing eye movement patterns during text reading in six patients with pure alexia with those of six patients with hemianopic dyslexia showing similar right-sided visual field defects. We found that the role of the field defect in the reading difficulties of pure alexics was highly deficit-specific. While the amplitude of rightward saccades during text reading seems largely determined by the restricted visual field, other visuo-motor impairments-particularly the pronounced increases in fixation frequency and viewing time as a function of word length-may have little to do with their visual field defect. In addition, subtracting the lesions of the hemianopic dyslexics from those found in pure alexics revealed the largest group differences in posterior parts of the left fusiform gyrus, occipito-temporal sulcus and inferior temporal gyrus. These regions included the coordinate assigned to the centre of the visual word form area in healthy adults, which provides further evidence for a relation between pure alexia and a damaged visual word form area. Finally, we propose a list of three criteria that may improve the differential diagnosis of pure alexia and allow appropriate therapy recommendations

Remediation of Contaminated Groundwater

In order to decrease the health risk deriving from a contamination event,a number of cleanup and corrective actions, collectively called remediation, can beimplemented. Remediation can be applied directly at the site of contamination (insitu) or off site (ex situ), in which case the contaminated environmental compo-nent is physically extracted and treated in dedicated facilities at the surface. Thereare three main remedial approaches, generally categorized as: containment, whichaims at preventing the migration of the contamination and hence the exposure ofsensitive targets; active restoration, which entails removing or treating the contami-nation; and natural attenuation, which relies on naturally occurring biological, chem-ical and physical degradation or transformation processes that convert contaminantsinto harmless compounds. This Chapter reviews the main containment and remedialstrategies available for the management of a groundwater contamination event, andprovides valuable information to support the choice of the most suitable approach.The presented strategies include: free product recovery for light non-aqueous phaseliquid removal; vacuum enhanced extraction; subsurface containment; pump andtreat; air- and bio-sparging; permeable reactive barriers; in situ flushing; in situ oxi-dation;insitubioremediation.Applicability,designoptionsandoperatingconditions,as well as advantages and drawbacks of the presented methods are illustrated