Mechanical properties of co-doped zirconia ceramics

Tesi per compendi de publicacions, amb diferents seccions retallades pels drets d'editorPremi extraordinari doctorat UPC curs 2017-2018. Àmbit d’Enginyeria IndustrialTetragonal polycrystalline zirconia, commonly stabilised with 3 mol% yttria (3Y-TZP), became one of the most interesting ceramics for biomedical applications due to its biocompatibility and high mechanical properties. Among them, its high fracture toughness should be highlighted, which is due to the stress-induced tetragonal-to-monoclinic (t-m) phase transformation near a crack tip. However, the tetragonal grains on the Surface can also spontaneously transform to monoclinic phase in a humid environment, phenomenon known as low-temperature degradation (LTD), which is an important issue for applications in which water is present. Several methods have been proposed to increase the LTD resistance in zirconia, which range from improving the fabrication process in terms of grain size, density or residual stresses, to doping zirconia with other oxides, like magnesia or ceria. Particularly, ceria-stabilised zirconia (Ce-TZP) possesses higher LTD resistance and fracture toughness than 3Y-TZP, but lower fracture strength and hardness, partly because of its larger grain size. The approach proposed in this work consists in the improvement of mechanical properties of Ce-TZP by reducing grain size, without reducing LTD resistance. With this objective, starting from two compositions of Ce-TZP (10 and 12 mol% CeO2), different amounts of CaO and Y2O3 have been added to reduce the grain growth during sintering, and thus increasing the critical t-m transformation stress, and consequently flexural resistance and hardness. On the other hand, as flexural resistance is determined by fracture toughness from small superficial cracks, a novel reproducible methodology to produce superficial micro-notches by means of ultra-short pulsed laser ablation has been developed to measure this property. It has been highlighted that with the developed methodology very sharp cracks are produced, with the size in the order of natural cracks. Results show that small-crack fracture toughness is very different from values measured from methods using large cracks or from the indentation method. This thesis is submitted for the degree of Doctor of Philosophy in the program "Materials Science and Engineering" at the Universitat Politècnica de Catalunya as a compendium of published articles. The research described in this work was carried out by the author during the period from December 2012 to October 2017 under the supervision of Prof. M. Anglada in the Department of Materials Science and Metallurgical Engineering at the Universitat Politècnica de Catalunya, and during 3 research stays during 2015, 2016 and 2017 (406 days in total) in the Department of Materials Science (MTM) at KU Leuven (Belgium) under the supervision of Prof. J. Vleugels. The work described in this dissertation is original, unless otherwise detailed references are provided.L'òxid de zirconi estabilitzat amb un 3 mol% d'itria és una ceràmica policristal·lina amb estructura tetragonal (denominada freqüentment zircònia, o bé 3Y-TZP) presenta propietats molt interessants per a aplicacions biomèdiques degut a la seva biocompatibilidad i altes propietats mecàniques. Entre elles, destaca la seva alta tenacitat de fractura, la qual és deguda a la transformació de fase tetragonal a monoclínica (t-m) induïda sota tensió al voltant de la punta d'una esquerda. No obstant, els grans tetragonals superficials també poden transformar-se de forma espontània a fase monoclínica en ambients humits, fenomen conegut com a degradació a baixa temperatura (LTD, per les seves sigles en anglès), la qual és un problema important en aplicacions on l'aigua hi és present. Diversos mètodes s'han proposat per tal d'augmentar la resistència a la LTD de la zircònia, des de la millora dels processos de fabricació en termes de tamany de gra, densitat o tensions residuals, fins al dopatge de la zircònia amb altres òxids, com magnèsia o cèria. Particularment, la zircònia estabilitzada amb cèria (Ce-TZP) posseeix una alta resistència a la LTD i major tenacitat de fractura que la 3Y-TZP, però menor resistència a fractura i duresa, en part degut a la seva major grandària de gra. L'estratègia seguida en aquest treball consisteix en la millora de les propietats mecàniques de la Ce-TZP mitjançant la reducció de la grandària de gra, sense disminuir la resistència a la LTD. Amb aquest objectiu, partint de dues composicions de Ce-TZP (10 i 12 mol% de CeO2), s'han afegit diferents quantitats de CeO i de Y2O3 per a reduir el creixement de gra durant la sinterització i així augmentar la tensió crítica per a la transformació t-m, i per tant la resistència a flexió i duresa. Per altra banda, donat que la resistència a flexió ve determinada per la tenacitat de fractura d'esquerdes petites superficials, s'ha desenvolupat una metodologia reproduïble per a produir micro-entalles superficials mitjançant l'ablació làser de puls ultra-curt per així mesurar aquesta propietat. S'ha posat en relleu que amb la metodologia desenvolupada es produeixen esquerdes molt afilades i de dimensions de l'ordre de les esquerdes naturals presents. Els resultats posen de manifest que la tenacitat de fractura per esquerdes petites són molt diferents de les obtingudes per mètodes amb esquerdes grans o a partir del mètode d'indentació. Aquesta tesis és dipositada pel grau de doctor en el programa "Ciència i Enginyeria dels Materials" de la Universitat Politècnica de Catalunya com a compendi de publicacions. La investigació descrita en aquest treball es va desenvolupar per l'autor durant el període de desembre de 2012 a octubre de 2017 sota la supervisió del professor M. Anglada al Departament de Ciència dels Materials i Enginyeria Metal·lúrgica de la Universitat Politècnica de Catalunya, i durant tres estades d'investigació durant 2015, 2016 i 2017 (406 dies en total) al Departament de Ciència de Materials (MTM) de KU Leuven (Bèlgica), sota la supervisió del professor J. Vleugels. El treball descrit en aquesta dissertació és original, llevat quan es proporcionen referències detallades.Award-winningPostprint (published version

Mechanical properties of co-doped zirconia ceramics

Tetragonal polycrystalline zirconia, commonly stabilised with 3 mol% yttria (3Y-TZP), became one of the most interesting ceramics for biomedical applications due to its biocompatibility and high mechanical properties. Among them, its high fracture toughness should be highlighted, which is due to the stress-induced tetragonal-to-monoclinic (t-m) phase transformation near a crack tip. However, the tetragonal grains on the Surface can also spontaneously transform to monoclinic phase in a humid environment, phenomenon known as low-temperature degradation (LTD), which is an important issue for applications in which water is present. Several methods have been proposed to increase the LTD resistance in zirconia, which range from improving the fabrication process in terms of grain size, density or residual stresses, to doping zirconia with other oxides, like magnesia or ceria. Particularly, ceria-stabilised zirconia (Ce-TZP) possesses higher LTD resistance and fracture toughness than 3Y-TZP, but lower fracture strength and hardness, partly because of its larger grain size. The approach proposed in this work consists in the improvement of mechanical properties of Ce-TZP by reducing grain size, without reducing LTD resistance. With this objective, starting from two compositions of Ce-TZP (10 and 12 mol% CeO2), different amounts of CaO and Y2O3 have been added to reduce the grain growth during sintering, and thus increasing the critical t-m transformation stress, and consequently flexural resistance and hardness. On the other hand, as flexural resistance is determined by fracture toughness from small superficial cracks, a novel reproducible methodology to produce superficial micro-notches by means of ultra-short pulsed laser ablation has been developed to measure this property. It has been highlighted that with the developed methodology very sharp cracks are produced, with the size in the order of natural cracks. Results show that small-crack fracture toughness is very different from values measured from methods using large cracks or from the indentation method. This thesis is submitted for the degree of Doctor of Philosophy in the program "Materials Science and Engineering" at the Universitat Politècnica de Catalunya as a compendium of published articles. The research described in this work was carried out by the author during the period from December 2012 to October 2017 under the supervision of Prof. M. Anglada in the Department of Materials Science and Metallurgical Engineering at the Universitat Politècnica de Catalunya, and during 3 research stays during 2015, 2016 and 2017 (406 days in total) in the Department of Materials Science (MTM) at KU Leuven (Belgium) under the supervision of Prof. J. Vleugels. The work described in this dissertation is original, unless otherwise detailed references are provided.L'òxid de zirconi estabilitzat amb un 3 mol% d'itria és una ceràmica policristal·lina amb estructura tetragonal (denominada freqüentment zircònia, o bé 3Y-TZP) presenta propietats molt interessants per a aplicacions biomèdiques degut a la seva biocompatibilidad i altes propietats mecàniques. Entre elles, destaca la seva alta tenacitat de fractura, la qual és deguda a la transformació de fase tetragonal a monoclínica (t-m) induïda sota tensió al voltant de la punta d'una esquerda. No obstant, els grans tetragonals superficials també poden transformar-se de forma espontània a fase monoclínica en ambients humits, fenomen conegut com a degradació a baixa temperatura (LTD, per les seves sigles en anglès), la qual és un problema important en aplicacions on l'aigua hi és present. Diversos mètodes s'han proposat per tal d'augmentar la resistència a la LTD de la zircònia, des de la millora dels processos de fabricació en termes de tamany de gra, densitat o tensions residuals, fins al dopatge de la zircònia amb altres òxids, com magnèsia o cèria. Particularment, la zircònia estabilitzada amb cèria (Ce-TZP) posseeix una alta resistència a la LTD i major tenacitat de fractura que la 3Y-TZP, però menor resistència a fractura i duresa, en part degut a la seva major grandària de gra. L'estratègia seguida en aquest treball consisteix en la millora de les propietats mecàniques de la Ce-TZP mitjançant la reducció de la grandària de gra, sense disminuir la resistència a la LTD. Amb aquest objectiu, partint de dues composicions de Ce-TZP (10 i 12 mol% de CeO2), s'han afegit diferents quantitats de CeO i de Y2O3 per a reduir el creixement de gra durant la sinterització i així augmentar la tensió crítica per a la transformació t-m, i per tant la resistència a flexió i duresa. Per altra banda, donat que la resistència a flexió ve determinada per la tenacitat de fractura d'esquerdes petites superficials, s'ha desenvolupat una metodologia reproduïble per a produir micro-entalles superficials mitjançant l'ablació làser de puls ultra-curt per així mesurar aquesta propietat. S'ha posat en relleu que amb la metodologia desenvolupada es produeixen esquerdes molt afilades i de dimensions de l'ordre de les esquerdes naturals presents. Els resultats posen de manifest que la tenacitat de fractura per esquerdes petites són molt diferents de les obtingudes per mètodes amb esquerdes grans o a partir del mètode d'indentació. Aquesta tesis és dipositada pel grau de doctor en el programa "Ciència i Enginyeria dels Materials" de la Universitat Politècnica de Catalunya com a compendi de publicacions. La investigació descrita en aquest treball es va desenvolupar per l'autor durant el període de desembre de 2012 a octubre de 2017 sota la supervisió del professor M. Anglada al Departament de Ciència dels Materials i Enginyeria Metal·lúrgica de la Universitat Politècnica de Catalunya, i durant tres estades d'investigació durant 2015, 2016 i 2017 (406 dies en total) al Departament de Ciència de Materials (MTM) de KU Leuven (Bèlgica), sota la supervisió del professor J. Vleugels. El treball descrit en aquesta dissertació és original, llevat quan es proporcionen referències detallades

Laboratory diagnosis of brucellosis in a rural endemic area in northeastern Spain

Sera obtained from 62 patients from four mountain counties in Catalonia (Northeastern Spain), in whom brucellosis had been diagnosed on the basis of clinical evidence and/or personal history, were analyzed using the rose Bengal test, standard serum agglutination test (SAT), Coombs’ test, ELISA, and complement fixation. The diagnosis was further confirmed through blood cultures. Clinical evidence, epidemiology, and the results from serologic tests were used to assign patients to one of two groups: group 1 (n = 38) patients had primary infections, whereas group 2 (n = 24) patients had been previously exposed to the microorganism, i.e. re-infection of group 2 individuals occurred after long periods of time during which no active infection by Brucella had been detected. Receivingoperating charts (ROC) were used to determine the diagnostic value of the different tests and to establish discriminant values. Blood culture was a valuable diagnostic tool in group 1 (0.92 sensitivity) but was inappropriate in group 2 (0.08). The combination of positive rose Bengal test and agglutination ≥1/160 was valid for diagnosis in group 1. In group 2, agglutination < 1/160 (including negative agglutination) did not rule out brucellosis. The combination of positive rose Bengal test and Coombs’ test ≥1/320 was the best diagnostic criterion (0.8 specificity; 1 sensitivity). ELISA (for IgG, IgM, or both) did not improve diagnostic accuracy. [Int Microbiol 7(1):53–58, 2004

The 24th Congress of the Spanish Society for Microbiology (L'Hospitalet de Llobregat, Barcelona, 10-13 July 2013)

The 24th Congress of the Spanish Society for Microbiology (SEM) took place on 10-13 July, 2013 at the Bellvitge Campus of the University of Barcelona (UB), in L'Hospitalet de Llobregat, Barcelona [http://congresosem2013.semicro-biologia.org](Fig. 1). This meeting brought together 618 microbiologists from several prestigious universities and research centers throughou Spain, as well as experts from 24 countries including the United States, the United Kingdom, Germany, Australia, Canada, France, Italy, Belgium, Mexico, Austria, Chile, China, Denmark, Slovenia, the Netherlands, Peru, Sweden, Scotland, Turkey, Uruguay, and Venezuela

Proteins influencing foam formation in wine and beer: the role of yeast

This review focuses on the role of proteins in the production and maintenance of foam in both sparkling winesand beer. The quality of the foam in beer but especially in sparkling wines depends, among other factors, on the presence ofmannoproteins released from the yeast cell walls during autolysis. These proteins are hydrophobic, highly glycosylated, andtheir molecular masses range from 10 to 200 kDa- characteristics that allow mannoproteins to surround and thus stabilizethe gas bubbles of the foam. Both the production and stabilization of foam also depend on other proteins. In wine, theseinclude grape-derived proteins such as vacuolar invertase; in beer, barley-derived proteins, such as LTP1, protein Z, andhordein-derived polypeptides, are even more important in this respect than mannoproteins

Surface microstructural changes of spark plasma sintered zirconia after grinding and annealing

Spark plasma sintered zirconia (3Y-TZP) specimens have been produced of 140 nm 372 nm and 753 nm grain sizes by sintering at 1250 °C, 1450 °C and 1600 °C, respectively. The sintered zirconia specimens were grinded using a diamond grinding disc with an average diamond particle size of about 60 µm, under a pressure of 0.9 MPa. The influence of grinding and annealing on the grain size has been analysed. It was shown that thermal etching after a ruff grinding of specimens at 1100 °C for one hour induced an irregular surface layer of about a few hundred nanometres in thickness of recrystallized nano-grains, independently of the initial grain size. However, if the ground specimens were exposed to higher temperature, e.g. annealing at 1575 °C for one hour, the nano-grain layer was not observed. The resulted grain size was similar to that achieved by the same heat treatments on carefully polished specimens. Therefore, by appropriate grinding and thermal etching treatments, nanograined surface layer can be obtained which increases the resistance to low temperature degradation.Peer ReviewedPostprint (author's final draft

1,4-Benzodiazepines and New Derivatives: Description, Analysis, and Organic Synthesis

Benzodiazepines are widely used drugs for several indications. This study provides, on the other hand, a global vision of the family starting for their fortuitous discovery, the synthesis of their derivatives, their mechanism of action widely known nowadays, the actual classification according to the chemical structure and pharmacokinetic properties, and their uses and indications, the traditional and the new ones. On the other hand,the study is focused in the mainly problems of benzodiazepines, depedence, and tolerance, many times led by a misuse of the patient, wrong prescriptions, or extended treatments. A withdrawal program is proposed that includes the important factors or criteria to success, with a slow and gradual reduction of these drugs, avoiding relapse or severe adverse effects. New lines of research related to benzodiazepines are taken into account, which not only include the new therapeutic uses but also the adverse effects in short and long term. They are also analyzed the new discoveries concerning the nonbenzodiazepine drugs due to the close relation they have with benzodiazepines

A new disruption vector (pDHO) to obtain heterothallic strains from both Saccharomyces cerevisiae and Saccharomyces pastorianus

Yeasts are responsible for several traits in fermented beverages, including wine and beer, and their genetic manipulation is often necessary to improve the quality of the fermentation product. Improvement of wild-type strains of Saccharomyces cerevisiae and Saccharomyces pastorianus is difficult due to their homothallic character and variable ploidy level. Homothallism is determined by the HO gene in S. cerevisiae and the Sc-HO gene in S. pastorianus. In this work, we describe the construction of an HO disruption vector (pDHO) containing an HO disruption cassette and discuss its use in generating heterothallic yeast strains from homothallic Saccharomyces species

When Combined with Colistin, an Otherwise Ineffective Rifampicin-Linezolid Combination Becomes Active in Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii

The synergistic action of colistin, with two antibiotics active in Gram-positive bacteria but unable to kill gram negatives (linezolid and rifampicin), was investigated, since triple combinations are emerging as a tool to overtake multidrug resistance. Checkerboard determinations demonstrated that, when combined with colistin, the combination of linezolid and rifampicin turns active in multidrug-resistant Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii. Thus, the presence of sublethal concentrations of colistin resulted in a strongly synergistic interaction between these two drugs. Moreover, the minimum inhibitory concentrations of linezolid-rifampicin combinations in the presence of colistin were lower than the maximal concentrations of these antimicrobials ain blood. These findings suggest the use of this triple combination as an effective treatment of multidrug-resistant (MDR) bacterial infections

Atomic force microscopy visualization of injuries in Enterococcus faecalis surface caused by Er,Cr:YSGG and diode lasers

Aim: To visualize by atomic force microscopy the alterations induced on Enterococcus. faecalis surface after treatment with 2 types of laser: Erbium chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser and Diode laser. Material and methods: Bacterial suspensions from overnight cultures of E. faecalis were irradiated during 30 seconds with the laser-lights at 1 W and 2 W of power, leaving one untreated sample as control. Surface alterations on treated E. faecalis were visualized by atomic force microscopy (AFM) and its surface roughness determined. Results: AFM imaging showed that at high potency of laser both cell morphology and surface roughness resulted altered, and that several cell lysis signs were easily visualized. Surface roughness clearly increase after the treatment with Er,Cr:YSGG at 2W of power, while the other treatments gave similar values of surface roughness. The effect of lasers on bacterial surfaces visualized by AFM revealed drastic alterations. Conclusions: AFM is a good tool to evaluate surface injuries after laser treatment; and could constitute a measure of antimicrobial effect that can complete data obtained by determination of microbial viability