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PubMed2006

Synthesis and characterization of SiC materials with hierarchical porosity obtained by replication techniques.

Porous silicon carbide monoliths were obtained using the infiltration of preformed SiO(2) frameworks with appropriate carbon precursors such as mesophase pitch. The initial SiO(2) monoliths possessed a hierarchical pore system, composed of an interpenetrating bicontinuous macropore structure and 13 nm mesopores confined in the macropore walls. After carbonization, further heat treatment at ca. 1,400 degrees C resulted in the formation of a SiC-SiO(2) composite, which was converted into a porous SiC monolith by post-treatment with ammonium fluoride solution. The resulting porous SiC featured high crystallinity, high chemical purity and showed a surface area of 280 m(2) g(-1) and a pore volume of 0.8 ml g(-1).

Carbon Compounds, Inorganic↗
PubMed1999

Allergic contact cheilitis due to effervescent dental cleanser: combined responsibilities of the allergen persulfate and prosthesis porosity.

A 55-year-old man with a dental prosthesis for 3 years had had a chronic relapsing cheilitis for more than 1 year. He was patch tested with the European standard series, his own topicals, and the dental cleanser at 10% pet. A relevant positive reaction ++ was found to the cleansing agent, which contained 20% potassium persulfate. The breakdown of the test confirmed sensitivity to this agent and to ammonium persulfate, both positive (++) at 2.5% pet. The patient was free of symptoms after he had avoided the cleanser. Subsequent chemical investigations performed with a fragment of a used dental prosthesis revealed strong adsorption of persulfate, both on the resin and on the dental tartar. Cleansing agents, adsorbed on tartar and porous resins of worn dental prostheses, should be considered as potential sensitizers and consequently patch tested on such patients with chronic cheilitis.

Cheilitis↗
PubMed2006

Imbibition, desiccation and mechanical deformations of zein pills in relation to their porosity.

This paper deals with the interaction between zein (the main protein component of corn grain) and water. It induces macroscopic properties changes and may allow for the understanding of the basis of zein endosperm structure: vitreous endosperm is compact and floury endosperm is porous, giving the endosperm its hard and soft textures, respectively. In that aim porous pills made by compaction of zein powder submitted to different hydration/dehydration processes have been prepared and studied. In particular, imbibition measurements of a pure-water drop deposited onto a zein pill were performed. Also, desiccation of a zein pill previously imbibed induces strong mechanical stresses leading to crack formation and/or large deformations.

Mechanics↗
PubMed1994

Porosity and biological properties of polyethylene glycol-conjugated collagen materials.

Collagen-based materials can be designed for use as scaffolds for connective tissue reconstruction. The goal of the present study was to evaluate the behavior of collagen materials as well as cell and tissue reactions after the conjugation of activated polyethylene glycols (PEGs) with collagen. It is known that proteins conjugated with PEGs exhibit a decrease in their biodegradation rate and their immunogenicity. Different concentrations and molecular weights of activated PEGs (PEG-750 and PEG-5000) were conjugated to collagen materials (films or sponges) which were then investigated by collagenase assay, fibroblast cell culture, and subcutaneous implantation. PEG-conjugated collagen sponge degradation by collagenase was delayed in comparison to untreated sponges. In culture, fibroblasts with a normal morphology reached confluency on PEG-conjugated collagen films. In vivo, the porous structure of non-modified sponges collapsed by day 15 with a few observable fibroblasts between the collagen fibers. In PEG-modified collagen sponges, the porous structure remained stable for 30 days. Cell infiltration was particularly enhanced in PEG-750-conjugated collagen sponges. In conclusion, PEGs conjugated onto collagen sponges stabilize the porous structure without deactivating the biological properties of collagen. These porous composite materials could function as a scaffold to organize tissue ingrowth.

Animals↗