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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (69,575 recursos)
E-prints UPC cobreix dues finalitats: per una banda, és el dipòsit institucional de la UPC que recull els articles de revista, les comunicacions de congrés i els reports de recerca generats en les activitats de recerca del personal docent i investigador de la universitat; per l'altra, és una eina que permet accelerar la producció científica, allotjant versions de documents prèvies a la publicació en una revista o a les actes d’un congrés.

Articles de revista

Mostrando recursos 1 - 20 de 430

1. Fracture and fatigue of rock bit cemented carbides: Mechanics and mechanisms of crack growth resistance under monotonic and cyclic loading - Torres, Y.; Tarragó Cifre, Jose María; Coureaux Mustelier, David; Tarrés, E.; Roebuck, C.; Chan, P.; James, M.; Liang, B.; Tillman, M.; Viswanadham, R.K.; Mingard, K.P.; Mestra Rodríguez, Álvaro Miguel; Llanes Pitarch, Luis Miguel
In an attempt to improve the material selection, design and reliability of rock bit WC-Co cemented carbides (hardmetals), an extensive and detailed study is conducted with the main goal of characterizing the fracture and fatigue crack growth (FCG) behavior of four hardmetal grades. Work includes basic microstructural and mechanical characterization of the materials, assessment of fracture toughness and FCG kinetics. It is found that rock bit cemented carbides exhibit relatively high fracture toughness values (between 17 and 20 MPa root m) in direct association with their specific microstructural characteristics, i.e. medium/coarse carbide grain size and medium cobalt content. The influence...

2. Micro-mechanical testing of afvanced ceramics: tools, procedures and first results - Camposilvan, Erik; Jiménez Piqué, Emilio; Anglada Gomila, Marcos Juan
Micro-mechanical testing has lately become a more accessible tool for understanding deformation, strengthening and failure mechanisms at small scales. It has been found that the often considered intrinsic or “intensive” properties of materials, i.e. not size dependent, start to exhibit an extrinsic behaviour if the volume of material tested is reduced down to the level of the micro- or nano-scale. This is true at least for metals, where diverse experimental approaches have shown that the ultimate strength strongly increases in enough small material volumes in the micro-nano range. In ceramics, the small scale testing approach has received much less attention probably because of the absence...

3. Micro-mechanical testing of afvanced ceramics: tools, procedures and first results - Camposilvan, Erik; Jiménez Piqué, Emilio; Anglada Gomila, Marcos Juan
Micro-mechanical testing has lately become a more accessible tool for understanding deformation, strengthening and failure mechanisms at small scales. It has been found that the often considered intrinsic or “intensive” properties of materials, i.e. not size dependent, start to exhibit an extrinsic behaviour if the volume of material tested is reduced down to the level of the micro- or nano-scale. This is true at least for metals, where diverse experimental approaches have shown that the ultimate strength strongly increases in enough small material volumes in the micro-nano range. In ceramics, the small scale testing approach has received much less attention probably because of the absence...

4. Low modulus Ti-Nb-Hf alloy for biomedical applications - González Colominas, Marta; Peña Andrés, Javier; Gil Mur, Francisco Javier; Manero Planella, José María
beta-Type titanium alloys with a low elastic modulus are a potential strategy to reduce stress shielding effect and to enhance bone remodeling in implants used to substitute failed hard tissue. For biomaterial application, investigation on the mechanical behavior, the corrosion resistance and the cell response is required. The new Ti25Nb16Hf alloy was studied before and after 95% cold rolling (95% C.R.). The mechanical properties were determined by tensile testing and its corrosion behavior was analyzed by potentiostatic equipment in Hank's solution at 37 degrees C. The cell response was studied by means of cytotoxicity evaluation, cell adhesion and proliferation measurements....

5. Fracture toughness of zirconia from a shallow notch produced by ultra-short pulsed laser ablation - Turón Viñas, Miquel; Anglada Gomila, Marcos Juan
Ceria partially stabilized zirconia ceramics (Ce-TZP) with identical grain size and different amounts of transformation toughening were processed to investigate the influence of phase transformation on static and cyclic fatigue crack growth. Static crack growth is governed by environmentally stress induced corrosion at the crack tip and it is highly influenced by the crack shielding due to the phase transformation. Three fatigue mechanisms are expected to be operative at different proportions depending on the amount of transformation: wedge effect due to debris, degradation of bridging and modification of the shielding effect of the transformation zone. However, it is difficult to separate...

6. Fracture toughness of zirconia from a shallow notch produced by ultra-short pulsed laser ablation - Turón Viñas, Miquel; Anglada Gomila, Marcos Juan
Ceria partially stabilized zirconia ceramics (Ce-TZP) with identical grain size and different amounts of transformation toughening were processed to investigate the influence of phase transformation on static and cyclic fatigue crack growth. Static crack growth is governed by environmentally stress induced corrosion at the crack tip and it is highly influenced by the crack shielding due to the phase transformation. Three fatigue mechanisms are expected to be operative at different proportions depending on the amount of transformation: wedge effect due to debris, degradation of bridging and modification of the shielding effect of the transformation zone. However, it is difficult to separate...

7. Effect of structure, topography and chemistry on fibroblast adhesion and morphology - Mateos Timoneda, Miguel Angel; Castaño Linares, Óscar; Planell Estany, Josep Anton; Engel López, Elisabeth
Surface biofunctionalisation of many biodegradable polymers is one of the used strategies to improve the biological activity of such materials. In this work, the introduction of collagen type I over the surface of a biodegradable polymer (poly lactic acid) processed in the forms of films and fibers leads to an enhancing of the cellular adhesion of human dermal fibroblast when compared to unmodified polymer and biomolecule-physisorbed polymer surface. The change of topography of the material does not affect the cellular adhesion but results in a higher proliferation of the fibroblast cultured over the fibers. Moreover, the difference of topography governs...

8. Effect of structure, topography and chemistry on fibroblast adhesion and morphology - Mateos Timoneda, Miguel Angel; Castaño Linares, Óscar; Planell Estany, Josep Anton; Engel López, Elisabeth
Surface biofunctionalisation of many biodegradable polymers is one of the used strategies to improve the biological activity of such materials. In this work, the introduction of collagen type I over the surface of a biodegradable polymer (poly lactic acid) processed in the forms of films and fibers leads to an enhancing of the cellular adhesion of human dermal fibroblast when compared to unmodified polymer and biomolecule-physisorbed polymer surface. The change of topography of the material does not affect the cellular adhesion but results in a higher proliferation of the fibroblast cultured over the fibers. Moreover, the difference of topography governs...

9. Covalent immobilization of hLf1-11 peptide on a titanium surface reduces bacterial adhesion and biofilm formation - Godoy Gallardo, Maria; Mas Moruno, Carlos; Fernandez Calderon, Maria C.; Perez Giraldo, Ciro; Manero Planella, José María; Albericio, Fernando; Gil Mur, Francisco Javier; Rodríguez Rius, Daniel
Bacterial infection represents a major cause of implant failure in dentistry. A common approach to overcoming this issue and treating pen-implant infection consists in the use of antibiotics. However, the rise of multidrug-resistant bacteria poses serious concerns to this strategy. A promising alternative is the use of antimicrobial peptides due to their broad-spectrum activity against bacteria and reduced bacterial resistance responses. The aim of the present study was to determine the in vitro antibacterial activity of the human lactoferrin-derived peptide hLf1-11 anchored to titanium surfaces. To this end, titanium samples were functionalized with the hLf1-11 peptide either by silanization methods...

10. Covalent immobilization of hLf1-11 peptide on a titanium surface reduces bacterial adhesion and biofilm formation - Godoy Gallardo, Maria; Mas Moruno, Carlos; Fernandez Calderon, Maria C.; Perez Giraldo, Ciro; Manero Planella, José María; Albericio, Fernando; Gil Mur, Francisco Javier; Rodríguez Rius, Daniel
Bacterial infection represents a major cause of implant failure in dentistry. A common approach to overcoming this issue and treating pen-implant infection consists in the use of antibiotics. However, the rise of multidrug-resistant bacteria poses serious concerns to this strategy. A promising alternative is the use of antimicrobial peptides due to their broad-spectrum activity against bacteria and reduced bacterial resistance responses. The aim of the present study was to determine the in vitro antibacterial activity of the human lactoferrin-derived peptide hLf1-11 anchored to titanium surfaces. To this end, titanium samples were functionalized with the hLf1-11 peptide either by silanization methods...

11. The integrin ligand c(RGDf(NMe)Nal) reduces neointimal hyperplasia in a polymer-free drug-eluting stent system - Rechenmacher, Florian; Steigerwald, Kristin; Laufer, Burkhardt; Neubauer, Stefanie; Kapp, Tobias G.; Li, Liang; Mas Moruno, Carlos; Joner, Michael; Kessler, Horst
The use of highly active and selective integrin ligands in combination with stent implantation is emerging as a promising alternative to the release of classical immunosuppressive drugs by current drug-eluting stents (DES), which has been associated with delayed vascular healing and late stent thrombosis. Herein we present the development and biological evaluation of the integrin ligand c(RGDf(NMe)Nal) as a potent anti-proliferative molecule that targets coronary artery smooth muscle cells (CASMCs). This peptide showed an antagonistic activity for alpha v beta 3 and alpha v beta 5 in the low-nanomolar range, and selectivity against the platelet receptor alpha IIb beta 3....

12. The integrin ligand c(RGDf(NMe)Nal) reduces neointimal hyperplasia in a polymer-free drug-eluting stent system - Rechenmacher, Florian; Steigerwald, Kristin; Laufer, Burkhardt; Neubauer, Stefanie; Kapp, Tobias G.; Li, Liang; Mas Moruno, Carlos; Joner, Michael; Kessler, Horst
The use of highly active and selective integrin ligands in combination with stent implantation is emerging as a promising alternative to the release of classical immunosuppressive drugs by current drug-eluting stents (DES), which has been associated with delayed vascular healing and late stent thrombosis. Herein we present the development and biological evaluation of the integrin ligand c(RGDf(NMe)Nal) as a potent anti-proliferative molecule that targets coronary artery smooth muscle cells (CASMCs). This peptide showed an antagonistic activity for alpha v beta 3 and alpha v beta 5 in the low-nanomolar range, and selectivity against the platelet receptor alpha IIb beta 3....

13. Fracture micromechanisms and mechanical behavior of YBCO bulk superconductors at 77 and 300 K - Konstantopoulou, K; Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Segarra Rubi, Merce; Pastor, J. Y.
In this study two YBa2Cu3O7-delta bulk superconductors were evaluated, with the aim of analyzing the influence of the processing method (TSMG and Bridgman) and the test temperature on their mechanical behavior. The relationship between their mechanical properties and fracture micromechanisms has also been studied. Both materials were tested at room and at service temperature. TPB tests were carried out to determine their mechanical behavior, strength and toughness. Moreover, one of the two materials, characterized by transversal microstructural anisotropy, was tested in two directions. Hardness of both materials at nano and micro scale was studied. The results show that the mechanical...

14. Fracture micromechanisms and mechanical behavior of YBCO bulk superconductors at 77 and 300 K - Konstantopoulou, K; Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Segarra Rubi, Merce; Pastor, J. Y.
In this study two YBa2Cu3O7-delta bulk superconductors were evaluated, with the aim of analyzing the influence of the processing method (TSMG and Bridgman) and the test temperature on their mechanical behavior. The relationship between their mechanical properties and fracture micromechanisms has also been studied. Both materials were tested at room and at service temperature. TPB tests were carried out to determine their mechanical behavior, strength and toughness. Moreover, one of the two materials, characterized by transversal microstructural anisotropy, was tested in two directions. Hardness of both materials at nano and micro scale was studied. The results show that the mechanical...

15. Robocasting of biomimetic hydroxyapatite scaffolds using self-setting inks - Maazouz, Yassine; Montufar Jiménez, Edgar Benjamin; Guillem Martí, Jordi; Fleps, I.; Ohman, C.; Persson, C.; Ginebra Molins, Maria Pau
Low temperature self-setting ceramic inks have been scarcely investigated for solid freeform fabrication processes. This work deals with the robocasting of alpha-tricalcium phosphate/gelatine reactive slurries as a bioinspired self-setting ink for the production of biomimetic hydroxyapatite/gelatine scaffolds. A controlled and totally interconnected pore network of similar to 300 mu m was obtained after ink printing and setting, with the struts consisting of a micro/nanoporous matrix of needle-shaped calcium deficient hydroxyapatite crystals, with a high specific surface area. Gelatine was effectively retained by chemical crosslinking. The setting reaction of the ink resulted in a significant increase of both the elastic modulus...

16. Design and facile solid-phase synthesis of peptide-based LPS-inhibitors containing PEG-like functionalities - Mas Moruno, Carlos; Cascales, L.; Mora, P.; Cruz, L.J.; Perez-Paya, E.; Albericio, F.
LPS release from Gram-negative bacteria can result in sepsis, a serious systemic inflammatory response to infection that can lead to septic shock and multiple organ failure. Thus, easy-to-synthesize, effective, and safe LPS-inhibitors are required to develop new agents for the treatment of sepsis. On the basis of the chemical features of the toxic part of LPS, lipid A, here we present peptide-based LPS-neutralizers that can be readily obtained using solid-phase methodologies. The presence of PEG-like moieties yielded the most active compounds, thereby indicating that these functionalities may be of great value in the design of new inhibitors. In this regard,...

17. The impact of amino acid side chain mutations in conformational design of peptides and proteins - Laufer, B.; Frank, A.O.; Chatterjee, J.; Neubauer, T.; Mas Moruno, Carlos; Kummerlöwe, G.; Kessler, H.
Local energetic effects of amino acid replacements are often considered to have only a moderate influence on the backbone conformation of proteins or peptides. As these effects are difficult to determine experimentally, no comparison has yet been performed. However, knowledge of the influence of side chain mutations is essential in protein homology modeling and in optimizing biologically active peptide ligands in medicinal chemistry. Furthermore, the tool of N-methylation of peptides is of increasing importance for the design of peptidic drugs to gain oral availability or receptor selectivity. However, N-methylation is often accompanied by considerable population of cis-peptide bond structures, resulting...

18. Polymer-free immobilization of a cyclic RGD peptide on a nitinol stent promotes integrin-dependent endothelial coverage of strut surfaces - Joner, M.; Cheng, Q.; Schönhofer-Merl, S.; Lopez, M.; Neubauer, S.; Mas Moruno, Carlos; Laufer, B.; Kolodgie, F.D.; Kessler, H.; Virmani, R.
This study examined the utility of a stabilized cyclic RGD peptide chemically modified to selectively bind to titanium-oxide for enhanced biocompatibility of self-expanding nitinol stents. Endothelial cells express integrin receptors that promote attachment to subendothelial matrix proteins. Integrin binding to arginine-glycine-aspartic acid (RGD) peptide derivatives mimic naturally occurring adherent interactions. Irreversible covalent surface coating of conventional nitinol stents with a cyclic RGD (cRGD) peptide highly specific for integrin alpha v beta 3 might foster endothelialization after stent implantation. A selective cRGD peptide was irreversibly immobilized onto titanium oxide-rich nitinol coupons or self-expanding stents. Functionality of the engrafted RGD peptide was...

19. Solid-phase-assisted synthesis of targeting peptide-PEG-oligo(ethane amino)amides for receptor-mediated gene delivery - Martin, I.; Dohmen, C.; Mas Moruno, Carlos; Troiber, C.; Kos, P.; Schaffert, D.; Lächelt, U.; Teixidó, M.; Günther, M.; Kessler, H.; Giralt, E.; Wagner, E.
In the forthcoming era of cancer gene therapy, efforts will be devoted to the development of new efficient and non-toxic gene delivery vectors. In this regard, the use of Fmoc/Boc-protected oligo(ethane amino)acids as building blocks for solid-phase-supported assembly represents a novel promising approach towards fully controlled syntheses of effective gene vectors. Here we report on the synthesis of defined polymers containing the following: (i) a plasmid DNA (pDNA) binding domain of eight succinoyl-tetraethylenpentamine (Stp) units and two terminal cysteine residues; (ii) a central polyethylene glycol (PEG) chain (with twenty-four oxyethylene units) for shielding; and (iii) specific peptides for targeting towards...

20. Low-pressure plasma treatment of polylactide fibers for enhanced mechanical performance of fiber-reinforced calcium phosphate cements - Canal Barnils, Cristina; Gallinetti, Sara; Ginebra Molins, Maria Pau
Calcium phosphate cements (CPCs) are extensively used as synthetic bone grafts, but their poor mechanical properties limit their applicability to non-stress-bearing applications. The aim of the present work is to evaluate the potential of plasma surface modification of polylactide (PLA) fibers for reinforcement of CPCs. Oxygen low-pressure plasma was employed at different treatment times and the surface properties of the untreated and plasma-treated PLA were evaluated. Plasma treatment on the PLA fibers reduced the setting times of the PLA-CPC composites and improved their flexural properties.

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