Characterisation of secondary silver ion-exchange into potassium ion-exchanged glass waveguides

Local enhancement of refractive index in potassium-ion-exchanged optical waveguides in glass is of interest for realization of low-loss bends and intersections and more complex structures such as gratings for reflection and phase-matching. Local enhancement may be realized through subsequent ion exchange with an ion having higher polarizability, such as silver. However, in order to design such structures, the diffusion of silver ions into potassium ion-exchanged waveguides must be characterized. In this paper, we present and compare diffusion profiles and coefficients of silver ions in soda-lime glass and in potassium-ion-exchanged waveguides in this glass

Chronic manganese exposure impairs visuospatial associative learning in non-human primates.

Manganese (Mn) is an essential trace metal nutrient, however, excess Mn can be neurotoxic. The degree to which chronic environmental or occupational exposures to Mn in adults cause neuropsychological dysfunction is of considerable interest. Descriptions of neuropsychological dysfunction following chronic Mn exposure have been somewhat inconsistent though, likely owing to different measures of exposure in different populations, complicated by factors of mixed exposures and differences in neuropsychological tests administered. We previously described up-regulation of the mRNA expression for amyloid-beta (A-beta) precursor-like protein 1 (APLP1) and the presence of A-beta diffuse plaques in frontal cortex of Mn-exposed monkeys. The present study examined Mn-induced changes in performance on a paired associate learning (PAL) task that has been suggested as a marker for preclinical Alzheimer’s disease. Aspects of performance of this task were affected early following initiation of Mn exposure. Thus, PAL performance may be a sensitive and valuable tool for the early, preclinical detection of incipient dementia and it may also be a sensitive tool for detecting cognitive dysfunction from Mn exposure. The current cognitive data, combined with our previous findings, suggest that frontal cortex may be a particularly sensitive target for the effects of Mn on cognition and that chronic Mn exposure may initiate or accelerate a process that could lead to or predispose to Alzheimer’s like pathology and cognitive dysfunction