Borrell, Josep (2013). Del silici a la raó: La xarxa com a continu en l’emergentisme de Ferrater Mora

Borrell, Josep (2013)Del silici a la raó: La xarxa com a continu en l’emergentisme de Ferrater MoraGirona: Documenta Universitaria, 122 p.ISBN 978-84-9984-223-3Borrell, Josep (2013)Del silici a la raó: La xarxa com a continu en l’emergentisme de Ferrater MoraGirona: Documenta Universitaria, 122 p.ISBN 978-84-9984-223-3Borrell, Josep (2013)Del silici a la raó: La xarxa com a continu en l’emergentisme de Ferrater MoraGirona: Documenta Universitaria, 122 p.ISBN 978-84-9984-223-

Novel phosphate-based cements for clinical applications

This Thesis aims at the development of two novel families of inorganic phosphate cements with suitable characteristics for clinical applications in hard tissue regeneration or replacement. It is organized in two distinct parts. The first part focuses at the development of silicon-doped a-tricalcium phosphate and the subsequent preparation of a silicon-doped calcium phosphate cement for bone regeneration applications. For this purpose, silicon-doped a-tricalcium phosphate was synthesized by sintering a calcium-deficient hydroxyapatite at 1250ºC with different amounts of silicon oxide. The high temperature polymorph a-tricalcium phosphate was stabilized by the presence of silicon, which inhibited reversion of the b-a transformation, whereas in the Si-free a-tricalcium phosphate completely reverted to the b-polymorph. It was observed that the presence of Si did not alter the b-a transformation temperature. Both the Si-doped a-tricalcium phosphate and its Si-free counterpart were used as reactants in the formulation of calcium phosphate cements. While Si-doped a-tricalcium phosphate showed faster hydrolysis to calcium deficient hydroxyapatite, the composition, morphology and mechanical properties of both cements were similar upon completion of the reaction. When the samples were immersed in simulated body fluid, the Si-doped cement exhibited a faster deposition of an apatite layer on its surface than its Si-free counterpart, suggesting an enhanced bioactivity of the doped-cement. An in vitro cell culture study, in which osteoblast-like cells were exposed to a medium modified by the materials, showed a delay in cell proliferation and a stimulation of cell differentiation, the differentiation being more marked for the Si-containing cement. These results were attributed to the Ca depletion from the medium by both cements and to the continuous Si release detected for the Si-containing cement. The second part of this Thesis is focused on the development of a new family of inorganic phosphate-based cements for biomedical applications, namely magnesium phosphate cements. The magnesium phosphate cements have been extensively used in civil engineering due to their fast setting, early strength acquisition and adhesive properties, properties that can be also of use for biomedical applications. However, there are some aspects that should be improved before they can be used in the human body, namely their high exothermic setting reaction and the release of potentially harmful ammonium ions. Therefore, a new family of magnesium phosphate cements was explored as candidate biomaterials for hard tissue applications. These cements were prepared by mixing magnesium oxide with either sodium dihydrogen phosphate, ammonium dihydrogen phosphate or an equimolar mixture of both. The exothermia and the setting kinetics of the new cement formulations were tailored. The ammonium-containing magnesium phosphate cements resulted in struvite as the major reaction product, whereas the magnesium phosphate cement prepared with sodium dihydrogen phosphate resulted in an amorphous product. The magnesium phosphate cements studied showed an early compressive strength substantially higher than that of conventional apatitic calcium phosphate cements. Moreover, they showed antimicrobial properties against bacteria present in dental infections, which were attributed to the synergistic effect of a high osmolarity and high pH of the cement extracts. These properties make magnesium phosphate cements good candidates for endodontic applications. It is with this latter point in mind that some of the most relevant physico-chemical properties were further optimized and characterized. Particularly, their radiopacity was enhanced by the addition of bismuth oxide. The sealing efficiency of the magnesium phosphate cements and their adhesion to dentin were shown to be comparable or even higher than those presented by other inorganic cements used for endodontic treatments.Aquesta Tesi té com a objectiu el desenvolupament de dues noves famílies de ciments inorgànics de base fosfat amb propietats adequades per a aplicacions clíniques en regeneració o substitució de teixits durs. La Tesi està organitzada en dues parts. La primera part està centrada en el desenvolupament de fosfat tricàlcic a dopat amb silici i la subseqüent preparació de ciments de fosfat de calci dopats amb silici. Per a aquest objectiu, es va obtenir fosfat tricàlcic a dopat amb silici mitjançant la sinterització d’una hidroxiapatita deficient en calci amb diferents quantitats d’òxid de silici a 1250°C. La presència de silici va estabilitzar el polimorf d’alta temperatura (fosfat tricàlcic a), inhibint-se la reversió de la transformació b-a, mentre que el fosfat tricàlcic a sense silici va revertir completament a polimorf b. La presència de silici no va alterar la temperatura de la transformació b-a. Tant el fosfat tricàlcic a dopat amb silici com el seu homòleg sense silici van ser utilitzats com a reactius en la formulació de ciments de fosfat de calci. Si bé el fosfat tricàlcic a dopat amb silici va mostrar en les fases inicials una hidròlisi més ràpida a hidroxiapatita deficient en calci, un cop completada la reacció, la composició, morfologia i propietats mecàniques d’ambdós ciments van ser similars. L’estudi de bioactivitat mitjançant la immersió de les mostres en fluid corporal simulat va donar com a resultat la formació d’una capa d’apatita a la superfície del ciment dopat amb silici, més ràpida que al seu homòleg sense silici, fet que va suggerir una bioactivitat millorada del ciment dopat. L’estudi in vitro, en el qual cèl·lules osteoblàstiques es van exposar a un medi de cultiu que havia estat prèviament en contacte amb els ciments estudiats, va mostrar un retràs en la proliferació cel·lular i un estímul de la diferenciació cel·lular, aquest últim més marcat pel ciment que contenia silici. Aquests resultats es van atribuir a la reducció de calci en els medis en els quals estaven introduïts els ciments i a l’alliberament continu d’ions silici per part del ciment que en contenia.Postprint (published version

Physicochemical parameters and bioactive compounds of strawberry Ttee (Arbutus unedo L.) honey

Botanical origin, physicochemical properties (ash, colour, diastase activity, electrical conductivity (EC), hydroxymethylfurfural (HMF), moisture, optical rotation (OP), pH, reducing sugars, total acidity, total soluble solids, and water activity), bioactive compounds (BC), and antioxidant activity obtained from strawberry tree honey from South Portugal were investigated. Results showed that the pollen analysis and physicochemical parameters were found within to meet international honey specifications. Significant differences (P < 0.05) in results of ash content, EC, HMF, OP and colour when were compared with analogous famous Italian honey (Sardinia island). For BC, total phenolic and total flavonoid content were 94.47mg gallic acid/100 g and 5.33 mg quercetin/100 g, respectively. Concerning Portuguese honey, it was also found that radical scavenging activity (DPPH assay) was 43.46% and antioxidant activity was 18.85 mg ascorbic acid equivalent/100 g and 9.92 mg quercetin equivalent/100 g. These results confirmed that Portuguese strawberry tree honey has the highest antioxidant activity, when compared with other kinds of honey. This complete report demonstrates advantages and can help to promote consumption and shown their benefical properties (e.g., antioxidant); which will may increase the commercial value.Erasmus Mundus European Program [2008-1022/002

Optimització aliatges Al-Si-Cu microaliats

[CATALÀ] L’objectiu principal d’aquest treball és fer-ne un estudi dels diferents elements d’aliatge afegits al AlSi9Cu3, també designat com EN AC 46500. Aquets elements són el Zn, Mg, Cr, Zr i el refinant de gra TiB que s’afegeixen en petites quantitats. La intenció es millorar les propietats mecàniques del material base. Es realitzen distintes colades d’aquests microaliatges, dels quals es vol saber quin és el pic de duresa més alt en un temps de maduració més curt després de realitzar-li un tractament T6. Aquest tractament tèrmic té una posta en solució de 515°C durant 6h seguit d’un tremp amb aigua i posteriorment una maduració artificial a 170°C durant vuit intervals de temps diferents. Aquests paràmetres venen definits per resultats obtinguts en estudis previs. Per comprovar l’efectivitat del T6 s’han analitzat les dureses i s’han realitzat micrografies. Amb les mostres de les dureses s’ha pogut determinar que l’aliatge AlSi9Cu3 + 3 %Zn + 2%Mg + 0,2% Cr + 0,2% Zr presenta un major pic de duresa en menys temps que la resta de les colades. Amb aquest aliatge s’ha realitzat una colada major per fer un assaig de tracció i comparar la resistència a tracció de l’aliatge modificat amb l’aliatge base. L’assaig no ha sigut satisfactori degut a les impureses (òxids i porositats) de les provetes sorgides durant la fabricació. No obstant, s’ha pogut comprovar un lleuger augment de la resistència a la tracció en l’aliatge modificat.[ANGLÈS] The main objective of this work is to realize a study of the different alloy elements added to AlSi9Cu3, also designated as EN AC 46500. These elements are Zn, Mg, Cr, Zr and the grain refiner TiB which are added in small amounts. The intention is to improve the mechanical properties of the base material. Different casts are made of these micro-alloys, which are intended to know what is the highest peak strength in a shorter aging time after performing a T6 treatment. This heat treatment has a temperature solution of 515 ° C for 6 hours followed by a quench with water and then an artificial aging at 170 ° C for eight different time intervals. These parameters are defined by results obtained in previous studies. To verify the effectiveness of the T6, the hardness has been analyzed and micrographs have been performed. With the samples of the hardness it has been possible to determine that the alloy AlSi9Cu3 + 3% Zn + 2% Mg + 0.2% Cr + 0.2% Zr presents a greater peak of hardness in less time than the rest of the casts With this alloy, a larger leakage has been performed to perform a tensile test and compare the tensile strength of the modified alloy with the base alloy. The test has not been satisfactory due to the impurities (oxides and porosities) of the test tubes produced during manufacture. However, it has been possible to check a slight increase in the tensile strength in the modified alloy