Osteogenic properties of calcium phosphate ceramics and fibrin glue based composites

Calcium phosphate (Ca-P) ceramics are currently used in various types of orthopaedic and maxillofacial applications because of their osteoconductive properties. Fibrin glue is also used in surgery due to its haemostatic, chemotactic and mitogenic properties and also as scaffolds for cell culture and transplantation. In order to adapt to surgical sites, bioceramics are shaped in blocks or granules and preferably in porous forms. Combining these bioceramics with fibrin glue provides a mouldable and self-hardening composite biomaterial. The aim of this work is to study the osteogenic properties of this composite material using two different animal models. The formation of newly formed bone (osteoinduction) and bone healing capacity (osteconduction) have been study in the paravertebral muscles of sheep and in critical sized defects in the femoral condyle of rabbits, respectively. The different implantations sites were filled with composite material associating Ca-P granules and fibrin glue. Ca-P granules of 1–2 mm were composed with 60% of hydroxyapatite and 40% of beta tricalcium phosphate in weight. The fibrin glue was composed of fibrinogen, thrombin and other biological factors. After both intramuscular or intraosseous implantations for 24 weeks and 3, 6, 12 and 24 weeks, samples were analyzed using histology and histomorphometry and mechanical test. In all cases, the newly formed bone was observed in close contact and around the ceramic granules. Depending on method of quantification, 6.7% (with BSEM) or 17% (with μ CT) of bone had formed in the sheep muscles and around 40% in the critical sized bone rabbit defect after 24 weeks. The Ca-P/fibrin material could be used for filling bone cavities in various clinical indications.     

On the comparison of photocatalysts activity: A novel procedure for the measurement of titania surface in TiO2/SiO2 materials

The distribution of two different phases in a mixed oxide material could be investigated through several physicochemical characterization techniques. However, the estimation of the fraction of the total surface area corresponding to each oxide is a very difficult task. In this work, we present a novel procedure for the determination of the titanium dioxide surface in titania–silica materials. This new method is based on the measurement of the phosphorus content of the mixed oxide after reaction with phenylphosphonic acid. The quantification of the TiO₂ surface has permitted the comparison of the catalytic activity of different materials in processes in which titanium dioxide is the only catalytically active phase and silica behaves as an inert support, as, for instance, in photocatalytic reactions. The activity of several TiO₂/SiO₂ photocatalysts for cyanide and methanol photooxidation have been analysed and compared with pure TiO₂ materials in terms of equal mass of semiconductor, photonic efficiency and active surface area. The results suggest the possibility of achieving surface activity rates even higher than the material Degussa P25 when using nanocrystalline titania supported on silica.     

Economical assessment of a wind–hydrogen energy system using WindHyGen software

This paper considers the problem of analyzing the economical feasibility of a wind–hydrogen energy storage and transformation system. Energy systems based on certain renewable sources as wind power, have the drawback of random input making them a non-reliable supplier of energy. Regulation of output energy requires the introduction of new equipment with the capacity to store it. We have chosen the hydrogen as an energy storage system due to its versatility. The advantage of these energy storage systems is that the energy can be used (sold) when the demand for energy rises, and needs (prices) therefore are higher. There are two disadvantages: (a) the cost of the new equipment and (b) energy loss due to inefficiencies in the transformation processes. In this research we develop a simulation model to aid in the economic assessment of this type of energy systems, which also integrates an optimization phase to simulate optimal management policies. Finally we analyze a wind–hydrogen farm in order to determine its economical viability compared to current wind farms.     

Fluidity of cement pastes with mineral admixtures and superplasticizer—A study based on the Marsh cone test

The Marsh cone test is a simple approach for obtaining a practical measure of the fluidity of cement pastes containing superplasticizer and silica fume. Using this method, a study of the effect of water/cement ratio, type and dosage of mineral admixture, and superplasticizer type on cement pastes with different superplasticizer dosages is presented here. Results are presented for cement pastes with silica fume and micronized diatomites as mineral admixtures. In all cases, there is a superplasticizer saturation dosage beyond which there is no significant increase in fluidity and, therefore, can be used for the selection of superplasticizer type and dosage. The data obtained indicate that the relative fluidity generally decreases with an increase in the silica fume content. The Marsh cone approach is also used to compare the effects of the mixing sequence used in the preparation of the pastes. A study of the loss of fluidity over time as a function of the superplasticizer type shows that the trends can vary considerably from one product to another.     

Generalization of the Barcelona test for the toughness control of FRC

Through different researches and application in works, the Barcelona test has proven to be adequate for toughness control of fiber reinforced concrete (FRC) and has recently been standardized in Spain (UNE 83515-2010). However, to determine FRC toughness an extensometer is required for measuring the circumferential displacement of the specimen in the post-cracking regime. In order to generalize the use of this test, this paper shows the results of an extensive experimental campaign in which circumferential and axial displacements of specimens were measured during tests. Results show a linear correlation between these displacements in a wide range of post-cracking regime, with a scatter lower than bending tests, commonly used to quantify FRC toughness. These results allow to use axial displacement measurement in place of the circumferential displacement. Additionally, the axial displacement it related with the piston stroke reaching highly successful results.     

Cracking behavior of FRC slabs with traditional reinforcement

The combination of fibers with traditional reinforcement may be a very interesting design solution to achieve more durable and economical structures. This paper deals with the analysis of the aforementioned solution through the study at serviceability and ultimate limit states. For this purpose, a total of eighteen concrete slabs were produced (3 × 1 × 0.2 m) with different reinforcement configurations, types of fibers (steel and plastic) and the fiber dosage used (0.25 and 0.50%). These slabs were tested under the configuration of a four point bending test. The results of this experimental campaign were used in the study of the cracking and deflection of the various types of concrete, tackling the analysis from several points of view.     

kPCA-Based Parametric Solutions Within the PGD Framework

Parametric solutions make possible fast and reliable real-time simulations which, in turn allow real time optimization, simulation-based control and uncertainty propagation. This opens unprecedented possibilities for robust and efficient design and real-time decision making. The construction of such parametric solutions was addressed in our former works in the context of models whose parameters were easily identified and known in advance. In this work we address more complex scenarios in which the parameters do not appear explicitly in the model—complex microstructures, for instance. In these circumstances the parametric model solution requires combining a technique to find the relevant model parameters and a solution procedure able to cope with high-dimensional models, avoiding the well-known curse of dimensionality. In this work, kPCA (kernel Principal Component Analysis) is used for extracting the hidden model parameters, whereas the PGD (Proper Generalized Decomposition) is used for calculating the resulting parametric solution.