A marine derived polysaccharide, ulvan, extracted from green algae, was combined with poly-d, l-lactic acid (PDLLA) in order to produce a novel scaffold for bone tissue engineering applications. Three dimensional (3D) scaffolds of PDLLA loaded with ulvan particles were originally prepared by subcritical fluid sintering with carbon dioxide at 40°C and 50 bar. Prepared matrixes were characterized in order to validate their suitability to be used as scaffolds for bone tissue regeneration. Characterization included micro-computed tomography, mechanical compression testing, water uptake and degradation testing, and cytotoxicity assays. In addition, ulvan particles loaded with dexamethasone, were also dispersed within the PDLLA matrix and the respective release profile from the samples was evaluated. Prepared PDLLA scaffolds enriched with ulvan particles demonstrated appropriate physicochemical and cytocompatible features to be used for the envisaged applications. On the other hand, the release of dexamethasone from ulvan particles embedded within the PDLLA matrix revealed that the designed systems can be potentially suitable for localized drug delivery. These results further contribute to the establishment of ulvan as a potential novel biomaterial. © 2012 Elsevier B.V. All rights reserved.

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The aim of this study was to evaluate the possibility of preparing chitosan porous matrixes using supercritical fluid technology. Supercritical immersion precipitation technique was used to prepare scaffolds of a natural biocompatible polymer, chitosan for tissue engineering purposes. The physicochemical and biological properties of chitosan make it an excellent material for the preparation of drug delivery systems and for the development of new biomedical applications in many fields from skin to bone or cartilage. Supercritical assisted phase inversion experiments were carried out and the effect of different organic solvents on the morphology of the scaffolds was assessed. Chitosan scaffold morphology, porosity and pore size were evaluated by SEM and micro-CT. A thermodynamic analysis of the process was carried out and insights on the solubility parameter and Flory-Huggins interaction parameters are given. The preparation of a highly porous and interconnected structure of a natural material, chitosan, using a clean and environmentally friendly technology constitutes a new processing technology for the preparation of scaffolds for tissue engineering using these materials. © 2011 Elsevier B.V.

High temperature superconducting (HTS) machines are recognized to offer several advantageous features when comparing to conventional ones. Amongst these, highlights the decrease in weight and volume of the machines, due to increased current density in conductors or the absence of iron slots' teeth; or the decrease in AC losses and consequent higher efficiency of the machines, even accounting for cryogenics. These concepts have been already demonstrated and some machines have even achieved commercial stage. In this paper, several alternative approaches are applied to electrical motors employing HTS materials. The first one is an all superconducting linear motor, where copper conductors and permanent magnets are replaced by Bi-2223 windings and trapped flux magnets, taking advantage of stable levitation due to flux pinning, higher current densities and higher excitation field. The second is an induction disk motor with Bi-2223 armature, where iron, ironless and hybrid approaches are compared. Finally, an innovative command strategy, consisting of an electronically variable pole pairs' number approach, is applied to a superconducting hysteresis disk motor. All these concepts are being investigated and simulation and experimental results are presented.

The deactivation reaction of the [CoCp(1,4-sigma-C(4)-[Ph](4))PPh(3)] catalyst for the cyclotrimerization of acetylenes has been kinetico-mechanistically studied under different temperature, pressure, and solvent conditions. The results indicate a dramatic change in mechanism from conventional to ionic liquid solvents due to the polarity of the medium.

The activation mechanism of Pseudomonas stutzeri cytochrome c peroxidase (CCP) was probed through the mediated electrochemical catalysis by its physiological electron donor, P. stutzeri cytochrome c-551. A comparative study was carried out, by performing assays with the enzyme in the resting oxidized state as well as in the mixed-valence activated form, using cyclic voltammetry and a pyrolytic graphite membrane electrode. In the presence of both the enzyme and hydrogen peroxide, the peak-like signal of cytochrome c-551 is converted into a sigmoidal wave form characteristic of an E(r)C'(i) catalytic mechanism. An intermolecular electron transfer rate constant of (4 +/- 1) x 10(5) M(-1) s(-1) was estimated for both forms of the enzyme, as well as a similar Michaelis-Menten constant. These results show that neither the intermolecular electron transfer nor the catalytic activity is kinetically controlled by the activation mechanism of CCP in the case of the P. stutzeri enzyme. Direct enzyme catalysis using protein film voltammetry was unsuccessful for the analysis of the activation mechanism, since P. stutzeri CCP undergoes an undesirable interaction with the pyrolytic graphite surface. This interaction, previously reported for the Paracoccus pantotrophus CCP, induces the formation of a non-native conformation state of the electron-transferring haem, which has a redox potential 200 mV lower than that of the native state and maintains peroxidatic activity.