ABSTRACT
Understanding water absorbency in paper is challenging as fibre swelling and out-of-plane deformation occur simultaneously during liquid imbibition. Liquid absorption is commonly accessed by gravimetric tests, which provides limited information on the local spatial and temporal distribution of fluid in the substrate. In this work, we developed iron tracers to map liquid imbibition in paper by in situ precipitation of iron oxide nanoparticles during passage of the wetting front. The iron oxide tracers were found to be robustly attached to the cellulosic fibres. After liquid absorption tests, absorbency was investigated by mapping the distribution of iron in 3D using X-ray micro-computed tomography (µCT) and in 2D using energy-dispersive X-ray spectroscopy. We demonstrate a difference in tracer distribution between the wetting front and the fully saturated region supporting that imbibition proceeds in two phases, i.e. liquid percolation through the cell wall initially prior to filling of the external pore spaces. Critically, we demonstrate that these iron tracers enhance image contrast and allow for new imaging modalities in µCT for fibre networks.
ABSTRACT
The aim of the present study was to examine, using a radioenzymatic assay technique, nitric oxide synthase (NOS) activity in the bilateral medial vestibular nuclei (MVN) and prepositus hypoglossi (PH), during the development of vestibular compensation for unilateral vestibular deafferentation (UVD) in the guinea pig. In the MVN ipsilateral to the UVD, and bilaterally in PH, NOS activity decreased following UVD compared to sham controls and did not recover significantly up to 50 h later, when a substantial degree of behavioural vestibular compensation had occurred. These results suggest that UVD causes a decrease in NOS activity in the ipsilateral MVN and the bilateral PH, and that a consequent decrease in NO may be responsible for some of the ocular motor and postural symptoms of UVD.
