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Matrix Swelling (matrix + swelling)
Selected AbstractsSorption irreversibility of 1,4-dichlorobenzene in two natural organic matter,rich geosorbentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2009Michael Sander Abstract Hysteresis, a frequently observed phenomenon in sorption studies, is inconsistent with the key assumption of sorption reversibility in most fate and bioavailability models. Therefore, a study of the underlying causes of hysteresis is essential. Carbon-radiolabeled 1,4-dichlorobenzene (DCB) isotope tracer exchange was carried out at select points along the isotherms of DCB in a brown coal and a peat soil, holding total DCB concentration constant. Tracer exchange was performed both in the forward (sorption) and reverse (desorption) directions at the bulk sorption points and in the desorption direction at the corresponding bulk desorption points. Bulk DCB isotherms showed concentration-dependent hysteresis. However, tracer reequilibration in all cases was consistent with free exchange between sorbed and aqueous-phase molecules. These results rule out common experimental artifacts and demonstrate that sorption of bulk DCB is truly hysteretic (i.e., irreversible). The differences in rates between bulk and tracer sorption and desorption are consistent with the coupling of bulk DCB diffusion to other processes that retard equilibration, which we assign to matrix swelling or shrinking. Hysteresis is attributed to matrix deformation,specifically, to inelastic expansion and creation of voids accommodating sorbate molecules in the matrix, which leads to enhanced affinity in the desorption step. Comparing the results to previous results for naphthalene in the coal, we find that irreversible effects are similar for DCB and naphthalene in the coal but differ for DCB between the two sorbents. An explanation based on the different physical properties of these sorbents is provided. Solid-phase extraction of equilibrated DCB with Tenax® revealed a highly desorption-resistant fraction. While too small to account for the observed hysteresis, this fraction may represent molecules that become trapped as the matrix collapses and simultaneously stiffens during abrupt desorption. [source] Physical indicators of cartilage health: the relevance of compliance, thickness, swelling and fibrillar textureJOURNAL OF ANATOMY, Issue 6 2003Neil D. Broom Abstract This study uses a bovine patella model to compare the relative merits of on-bone compliance and thickness measurements, free-swelling behaviour, and structural imaging with differential interference contrast (DIC) light microscopy to assess the biomechanical normality of the cartilage matrix. The results demonstrate that across a spectrum of cartilage tissues from immature, mature, through to mildly degenerate, and all with intact articular surfaces, there is a consistent pattern of increased free swelling of the isolated general matrix with age and degeneration. High swelling was always associated with major structural alterations of the general matrix that were readily imaged using DIC light microscopy. Conversely, for all tissue groups, no relationship was observed between thickness vs. compliance and compliance vs. general matrix swelling. Only in the proximal aspects of the normal mature and degenerate tissues was there a correlation between thickness and general matrix swelling. Free-swelling measurements combined with fibrillar texture imaging using DIC light microscopy are therefore recommended as providing a reliable and quick method of assessing the biomechanical condition of the cartilage general matrix. [source] Darcy's law-based model for wicking in paper-like swelling porous mediaAICHE JOURNAL, Issue 9 2010Reza Masoodi Abstract The wicking of liquid into a paper-like swelling porous medium made from cellulose and superabsorbent fibers was modeled using Darcy's law. The work is built on a previous study in which the Washburn equation, modified to account for swelling, was used to predict wicking in a composite of cellulose and superabsorbent fibers. In a new wicking model proposed here, Darcy's law for flow in porous media is coupled with the mass conservation equation containing an added sink or source term to account for matrix swelling and liquid absorption. The wicking-rate predicted by the new model compares well with the previous experimental data, as well as the modified Washburn equation predictions. The effectiveness of various permeability models used with the new wicking model is also investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Effect of amyloid ,-peptide on permeability transition pore: A comparative studyJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2002Paula I. Moreira Abstract A potentially central factor in neurodegeneration is the permeability transition pore (PTP). Because of the tissue-specific differences in pore properties, we directly compared isolated brain and liver mitochondria responses to the neurotoxic A, peptides. For this purpose, the following parameters were examined: mitochondrial membrane potential (,,m), respiration, swelling, ultrastructural morphology, and content of cytochrome c. Both peptides, A,25,35 (50 ,M) and A,1,40 (2 ,M), had a similar toxicity, exacerbating the effects of Ca2+, although, per se, they did not induce (PTP). In liver mitochondria, A, led to a drop in ,,m and potentiated matrix swelling and disruption induced by Ca2+. In contrast, brain mitochondria, exposed to the same conditions, demonstrated a higher capacity to accumulate Ca2+ before the ,,m drop and a slight increase of mitochondrial swelling compared with liver mitochondria. Furthermore, mitochondrial respiratory state 3 was depressed in the presence of A,, whereas state 4 was unaltered, resulting in an uncoupling of respiration. In both types of mitochondria, A, did not affect the content of cytochrome c. The ,,m drop was reversed when Ca2+ was removed by EGTA or when ADP plus oligomycin was present. Pretreatment with cyclosporin A or ADP plus oligomycin prevented the deleterious effects promoted by A, and/or Ca2+. It can be concluded that brain and liver mitochondria show a different susceptibility to the deleterious effect of A, peptide, brain mitochondria being more resistant to the potentiation by A, of Ca2+ -induced PTP. © 2002 Wiley-Liss, Inc. [source] Comparison of the roles of two shrinkage-controlled low-profile additives in water aging of polyster resin,glass fiber compositesPOLYMER COMPOSITES, Issue 5 2000G. Camino A model previously formulated or water sorption in polyester resin-glass fiber composites has been applied to the kinetic analysis of experimental data for two composites containing a hydrolysable (polyvinyl acetate-PVAc) and a non-hydrolyzable (polystyrene-PS) shrinkage-controlling low-profile additive (LPA) respectively. It was found that the equilibrium water uptake in the composites and their unreinforced matrix is not drastically affected by the type of LPA. The kinetics of water sorption in the composites, however, were substantially different. The PVAc composite displayed a two-stage sorption process, the first stage being attributed to diffusion combined with hydrolysis, and the second to matrix swelling and plasticizing. A maximum in the kinetic curve was observed, and was due to changes in water solubility inside the matrix during sorption. In contrast, the PS composite displayed the typical kinetics of materials with slowly increasing hydrophilicity. [source] | ||||||||||