CRACK BRIDGING AND TRAPPING IN BOROSILICATE MATRIX COMPOSITES WITH DISTRIBUTED METAL PARTICLES

Abstract One of the most efficient ways to improve the fracture toughness of ceramics is to reinforce them by large volume fraction of bonded metal particles (e.g., Krstic [1]; Evans and McMeekin

Soziale Arbeit im Wissenschaftssystem. Von der Fürsorgeschule zum Lehrstuhl Soziale Arbeit

Soziale

Community Studies aus der Sozialen Arbeit

Soziale

Soziale Arbeit zwischen Wissenschaft und Praxis. Zum Versuch einer Positionsbestimmung

Soziale

Determination of the Porosity of PLGA Microparticles by Tracking Their Sedimentation Velocity Using a Flow Imaging Microscope (FlowCAM)

PURPOSE: To investigate whether particle sedimentation velocity tracking using a flow imaging microscope (FlowCAM) can be used to determine microparticle porosity. METHODS: Two different methods were explored. In the first method the sedimentation rate of microparticles was tracked in suspending media with different densities. The porosity was calculated from the average apparent density of the particles derived by inter- or extrapolation to the density of a suspending medium in which the sedimentation velocity was zero. In the second method, the microparticle size and sedimentation velocity in one suspending fluid were used to calculate the density and porosity of individual particles by using the Stokes’ law of sedimentation. RESULTS: Polystyrene beads of different sizes were used for the development, optimization and validation of the methods. For both methods we found porosity values that were in excellent agreement with the expected values. Both methods were applied to determine the porosity of three PLGA microparticle batches with different porosities (between about 4 and 52%). With both methods we obtained microparticle porosity values similar to those obtained by mercury intrusion porosimetry. CONCLUSIONS: We developed two methods to determine average microparticle density and porosity by sedimentation velocity tracking, using only a few milligrams of powder. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11095-017-2120-8) contains supplementary material, which is available to authorized users

Experimental study comparing meshes made of polypropylene, polypropylene plus polyglactin and polypropylene plus titanium: inflammatory cytokines, histological changes and morphometric analysis of collagen

Incisional hernia occurs in approximately 11% of all laparotomies. Changes in collagen have been closely implicated in its pathogenesis. the high recurrence rate (45-54%) after primary suture has stimulated the development of meshes. Currently, meshes are the biomaterials implant group most used in medicine. This study aims to compare the serum and tissue inflammatory responses and collagen deposition caused by meshes made of polypropylene, polypropylene + polyglactin and polypropylene + titanium.Thirty Wistar rats were divided into three groups. in group I, a high-density polypropylene mesh was positioned on the abdominal wall. in groups II and III, low-density meshes were used in associations with polyglactin and titanium, respectively. Immediately before the operation and on the first, third and fortieth postoperative days, pro-inflammatory cytokines were assayed. On the 40th postoperative day, the region of the inserted prosthesis was biopsied. the tissue inflammatory reaction was evaluated using a scale for objective scoring. for collagen, picrosirius was used with data reading using the Image Tool computer software.Cytokines: there were no statistically significant differences between the groups. Histology: on the 40th postoperative day in group I, there were fewer inflammatory tissue response and greater collagen deposition (P < 0.01). in group II, there were greater inflammatory tissue response and less collagen deposition (P < 0.01). Group III presented intermediate values between groups I and II.There were no significant differences in cytokine levels between the groups in the present study. in the animals with the polypropylene + polyglactin mesh implant there was the most intense inflammatory process with lower tissue maturation and collagen deposition on the 40th postoperative day. the polypropylene mesh presented a less severe late inflammatory process, with greater tissue maturation and collagen deposition. the polypropylene + titanium mesh presented intermediate values between the others.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo, BR-04024002 São Paulo, BrazilUniversidade Federal de São Paulo, BR-04024002 São Paulo, BrazilFAPESP: 07/57100-6Web of Scienc