Characterization of the porous structure of biodegradable scaffolds obtained with supercritical CO2 as foaming agent

in Journal of Porous Materials (2008), 15(4), 397-403

Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury ... [more ▼]

Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury pycnometry, scanning electron microscopy (SEM) and X-ray microtomography observations coupled with image analysis. The pore size distributions obtained by these two latter techniques show that the pore structure is more homogeneous when the foaming process is performed under a high CO2 saturation pressure (higher than 250 bars). [less ▲]

Effect of b-cyclodextrin and its methylated derivatives on the ex-vivo rat aortic ring angiogenesis assay

Poster (2008, May)

Effect of far-infrared radiation assisted drying on microstructure of banana slices: An illustrative use of X-ray microtomography in microstructural evaluation of a food product

in Journal of Food Engineering (2008), 85(1), 154-162

X-ray microtomography coupled with image analysis represents a non-destructive technique, which allows scanning an entire sample to obtain such information as total pore volume and pore size distribution ... [more ▼]

X-ray microtomography coupled with image analysis represents a non-destructive technique, which allows scanning an entire sample to obtain such information as total pore volume and pore size distribution without the need of serial cuts as in the case of scanning electron microscopy (SEM). The technique has been applied successfully to obtain reliable microstructural information of many products undergoing different physical and chemical processes. However, the technique has still found limited use in food processing. To illustrate the use of X-ray microtomography the technique was applied to investigate the effect of far-infrared radiation (FIR) assisted drying on microstructure of a food product viz. banana. Two representative drying techniques, i.e., low-pressure superheated steam drying (LPSSD) and vacuum drying (VACUUM) were tested. Banana slices were dried by LPSSD-FIR at two different temperatures (80 and 90 degrees C) at a fixed pressure of 7 kPa. The total pore volume and pore size distribution of dried banana slices were then determined using X-ray microtomography. The results were also compared with those of products dried by LPSSD without FIR. Far-infrared radiation was found to modify the structure of the dried bananas by increasing their final porosity. The same effect of FIR was also observed in the case of vacuum drying with FIR (VACUUM-FIR). An increase of the drying temperature was also found to globally lead to an increase in the final porosity of the products. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

The lymphatic ring assay: a new in vitro model of lymphangiogenesis

in Acta Clinica Belgica (2008), 63

Formation mechanism of Y-junctions in arrays of multi-walled carbon nanotubes

in Colloids and Surfaces A : Physicochemical and Engineering Aspects (2008), 327(1-3), 140-143

Transmission electron microscopy of arrays of multi-walled carbon nanotubes reveals the presence of numerous Y-junctions. The diameter distributions of the samples are found to be bimodal, with one mode ... [more ▼]

Transmission electron microscopy of arrays of multi-walled carbon nanotubes reveals the presence of numerous Y-junctions. The diameter distributions of the samples are found to be bimodal, with one mode corresponding to the branches and the other mode to the trunk of the Y-junctions. The analysis of the micrographs shows that the junctions form via the merger of metal particles during the tip-growth of the tubes. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

Critical opalescence points to thermodynamic instability:relevance to small-angle X-ray scattering of resorcinol–formaldehyde gel formation at low pH

in Journal of Applied Crystallography (2008), 41(4), 663-668

During the formation at low pH of resorcinol–formaldehyde gels with a structure in the micrometre range, small-angle X-ray scattering exhibits a nonmonotonic intensity variation as a function of reaction ... [more ▼]

During the formation at low pH of resorcinol–formaldehyde gels with a structure in the micrometre range, small-angle X-ray scattering exhibits a nonmonotonic intensity variation as a function of reaction time. The data are analyzed in terms of scattering by statistical fluctuations of polymer concentration, the amplitude of which is maximal close to the critical point for phase separation between polymer and solvent. The data do not carry any morphological information, but they unambiguously show that the driving force of the gel formation is a thermodynamic instability of the polymerizing solution. [less ▲]

Persistence of an intact endometrial matrix and vessels structure in women exposed to VA-2914, a selective progesterone receptor modulator.

in Journal of Clinical Endocrinology and Metabolism (2008), 93(11), 4525-31

Background: VA-2914 is a selective progesterone receptor modulator with potential contraceptive activity that induces amenorrhea, whereas progestins cause endometrial spotting and bleeding. This abnormal ... [more ▼]

Background: VA-2914 is a selective progesterone receptor modulator with potential contraceptive activity that induces amenorrhea, whereas progestins cause endometrial spotting and bleeding. This abnormal bleeding due to progestins is a consequence of focal stromal proteolysis by an increase in naked vessel size and density. Objective: Our objective was to quantify the effects of VA-2914 on endometrial vascularization, fibrillar matrix, and vascular endothelial growth factor (VEGF)-A expression in endometrial biopsies from 41 women before and after 12 wk daily treatment with a placebo, or 2.5, 5, or 10 mg VA-2914. Methods: Collagen fibrillar network was stained by silver impregnation. Vessel area, density, and structure were quantified with a computer-assisted image analysis system after double immunostaining using an anti-von Willebrand factor (endothelial cells) and an anti- smooth muscle actin (vascular smooth muscle cells) marker antibody. VEGF-A mRNAs were quantified by RT-PCR and localized by immunohistochemistry. Results: The endometrial vessels, collagen network, and mRNA levels of VEGF-A were identical during the luteal phase at baseline and in VA-2914 treated women. VEGF-A distribution was unchanged. Conclusions: VA-2914 does not alter the endometrial matrix and cells, and does not modify the endometrial vessel morphology as compared with baseline biopsies. [less ▲]

Evolution of mechanical properties and final textural properties of resorcinol-formaldehyde xerogels during ambient air drying

in Journal of Non-Crystalline Solids (2008), 354(10-11), 831-838

Porous carbon xerogels can be obtained by convective drying of resorcinol (R)-formaldehyde (F) hydrogels, followed by pyrolysis. Drying conditions have to be carefully controlled when crack-free monoliths ... [more ▼]

Porous carbon xerogels can be obtained by convective drying of resorcinol (R)-formaldehyde (F) hydrogels, followed by pyrolysis. Drying conditions have to be carefully controlled when crack-free monoliths with well-defined shape and size are required. The knowledge of the mechanical properties of the RF xerogels and their evolution with water content is essential to model their thermo-hygro-mechanical behavior during convective drying and avoid mechanical stresses leading to deformation and cracking of the sample. The shrinkage behavior and the mechanical properties of RF xerogels obtained with R/C ratio ranging from 300 to 1500 were investigated. R/C greatly influences the shrinkage and mechanical properties of the wet gel, on the one hand, and the mechanical and textural properties of the dried gel, on the other hand. The smaller the R/C, the higher the shrinkage, the stiffening, and the viscoelastic character of the xerogels. Water content has an influence on both the stiffness of the gels and the viscoelastic response. Generally, samples lose their mechanical viscous character and become more rigid when they are dried. Finally., mercury porosimetry measurements showed that the gels exhibit a marked lowering of their stiffness upon compression, interpreted as a result of the heterogeneity of the microstructure. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

Implication of VEGF receptor soluble forms, sVEGFR-1 and sVEGFR-2, in angiogenesis

in Acta Clinica Belgica (2008), 63/1

Endometrial vessel maturation in women exposed to levonorgestrel-releasing intrauterine system for a short or prolonged period of time

in Human Reproduction (2007), 22(12), 3084-3091

BACKGROUND: Levonorgestrel-releasing intrauterine system (LNG-IUS), although inserted to reduce heavy menstruation, causes irregular early transient bleeding. The objective of the study was to document ... [more ▼]

BACKGROUND: Levonorgestrel-releasing intrauterine system (LNG-IUS), although inserted to reduce heavy menstruation, causes irregular early transient bleeding. The objective of the study was to document quantitative changes in endometrial vessels of short- (< or =3 months) and long-term (> or =12 months) LNG users. The area, density and maturation of endometrial vessels were quantified in 19 endometrial biopsies of women with LNG-IUS and in 10 normally ovulating patients during mid-luteal phase. METHODS: Vessel maturation was evaluated by double immunostaining using anti-von Willebrand factor (endothelial cell marker) and anti-alpha Smooth Muscle Actin (vascular smooth muscle cells) antibodies. Vessel area, number and density were quantified with a novel computer-assisted image analysis system. RESULTS: Endometrium exposed to LNG-IUS for 1-3 months displayed a 11.5-fold increase in small naked vessel number. The partially mature vessel (alphaSMA partially positive) number increased six times. After long-term LNG-IUS treatment, the immature and partially mature vessel number remained four times higher than in the control group. Vessel area and density also increased dramatically in a time-dependent pattern with LNG-IUS use. CONCLUSIONS: Levonorgestrel affects blood vessel number, area, density and maturation in a time-dependent pattern that may explain the early transient increase in breakthrough bleeding with the LNG-IUS. [less ▲]