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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (72,177 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 433

1. Viabilidad del reaprovechamiento de residuos de PVC provenientes de cables eléctricos: propiedades mecánicas - Franco Urquiza, Edgar Adrian; Maspoch Rulduà, Mª Lluïsa
En este trabajo se han evaluado las propiedades mecánicas de desechos de cloruro de polivinilo (PVC) provenientes de cables eléctricos. El residuo contenía 60% de PVC, 30% de polietileno, 7% de goma y 3% de fracción metálica. La fracción metálica fue separada de forma manual. La recuperación de PVC se realizó mediante el método de flotación. Se prepararon 6 mezclas de PVC con residuo (R). El PVC y las mezclas se ensayaron a tracción, obteniendo una reducción de la resistencia y la ductilidad al incrementar el contenido de residuo. Esta reducción en las propiedades mecánicas se se halla relacionada con la heterogeneidad de los componentes de la mezcla.

2. Collagen-functionalised titanium surfaces for biological sealing of dental implants: Effect of immobilisation process on fibroblasts response - Marín Pareja, Nathalia; Salvagni, Emiliano; Guillem Martí, Jordi; Aparicio Bádenas, Conrado José; Ginebra Molins, Maria Pau
The clinical success of a dental implant requires not only an optimum osseointegration, but also the development of a biological sealing; i.e., a soft tissue seal around the transmucosal part of the implant. A promising approach to improve the biological seal of dental implants is the biomimetic modification of titanium surfaces with proteins or peptides that have specific cell-binding moieties. In this work we investigated the process of immobilising collagen on smooth and rough titanium surfaces and its effect on human dermal fibroblast (HDF) cell response. Titanium samples were activated by either oxygen plasma or acid etching to generate a...

3. Effect of Nb and Mo on the hot ductility behavior of a high-manganese austenitic Fe-21Mn-1.3Al-1.5Si-0.5C TWIP steel - Mejía, Ignacio; Salas Reyes, A.E.; Bedolla Jacuinde, Arnoldo; Calvo Muñoz, Jessica; Cabrera Marrero, José M.
This research work studies the influence of single microalloying elements (Nb and Mo) and the solidification route on the hot ductility behavior of a high-manganese austenitic Twinning Induced Plasticity (TWIP) steel. For this purpose uniaxial hot tensile tests in the temperature range of 700-1100 degrees C under a constant true strain rate (10(-3) s(-1)) were carried out to evaluate the hot ductility as a function of reduction in area (%RA). In general, results revealed a beneficial influence of Nb and Mo additions to TWIP steels on the hot ductility behavior, particularly in the intermediate temperature range of 800-900 degrees C,...

4. Isocyanate toughening of pCBT/organoclay nanocomposites with exfoliated structure and enhanced mechanical properties - Abt, Tobias Martin; Bou Serra, Jordi; Sánchez Soto, Miguel
Cyclic butylene terephthalate (CBT (R)) is an interesting matrix material for the preparation of nanocomposites due to its very low, water-like melt viscosity which favours clay exfoliation. Nevertheless, polymerized CBT (pCBT) is inherently brittle. This paper reports the preparation of isocyanate-toughened nanocomposites made from CBT and organo-modified montmorillonite. The role of the organoclay as reinforcement and the polymeric isocyanate (PMDI) as toughening agent on the properties of pCBT was studied. The organoclay increased the stiffness and strength by up to 20% whereas the PMDI improved the deformation behaviour. However, the PMDI did not affect the degree of clay dispersion or...

5. An efficient and reproducible method to culture Bergmann and cortical radial glia using textured PMMA - Álvarez Pinto, Zaída; Sena, Elena; Mattotti, Marta; Engel López, Elisabeth; Alcantara, Soledad
Radial glia cells comprise the principal population of neural stem cells (NSC) during development. Attempts to develop reproducible radial glia and NSC culture methods have met with variable results, yielding non-adherent cultures or requiring the addition of growth factors. Recent studies demonstrated that a 2-µm patterned poly-methyl methacrylate (ln2 PMMA) grooved scaffold, by mimicking the biophysical and microtopographic properties of the embryonic NSC niche, induces the de-differentiation of glial cells into functional radial glia cell

6. Corona plasma modification of polyamide 66 for the design of textile delivery systems for cosmetic therapy - Labay, Cedric Pierre; Canal Arias, José Ma; Navarro Sentanyes, Antonio; Canal Barnils, Cristina
Cosmetic and medical applications of technical textiles are a research expanding field. One of the added values of these new materials would be that they are suitable to contain and release active ingredients in a controlled manner. The influence of the initial state of the surface of polyamide 6.6 (PA66) fibers on the wetting properties of the fibers as well as on the incorporation of caffeine on the fibers and on its release kinetics from the fibers has been investigated. Comparison between industrially-finished PA66 fabrics and laboratory washed fabrics has been done to carry out this study. Furthermore, surface modification...

7. Mechanical properties and in vitro biological response to porous titanium alloys prepared for use in intervertebral implants - Caparrós Vázquez, Cristina Maria; Guillem Martí, Jordi; Molmeneu Trias, Meritxell; Punset Fusté, Miquel; Calero, J. A.; Gil Mur, Francisco Javier
The generation of titanium foams is a promising strategy for modifying the mechanical properties of intervertebral reinforcements. Thus, the aim of this study was to compare the in vitro biological response of Ti6Al4V alloys with different pore sizes for use in intervertebral implants in terms of the adhesion, proliferation, and differentiation of pre-osteoblastic cells. We studied the production of Ti6Al4V foams by powder metallurgy and the biological responses to Ti6Al4V foams were assessed in terms of different pore interconnectivities and elastic moduli. The Ti6Al4V foams obtained had similar porosities of approximately 34%, but different pore sizes (66 mu m for...

8. Berkovich nanoindentation and deformation mechanisms in a hardmetal binder-like cobalt alloy - Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Tarragó Cifre, Jose María; Zivcec, Maria; Broeckmann, C.; Llanes Pitarch, Luis Miguel
A cobalt-base solid solution is the most used binder for hardmetals (WC–Co cemented carbides) in a wide range of industrial applications. In the composite material such cobalt alloy is surrounded by hard carbides grains; thus, a direct evaluation of its intrinsic mechanical properties is not an easy task. In order to overcome this inconvenience, a model cobalt alloy with a composition similar to that exhibited by typical hardmetal binder (containing W and C in solid solution) was processed following a powder metallurgy route. Nanoindentation testing at different length scales has been performed to study the mechanical properties as well as...

9. 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...

10. 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...

11. 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....

12. 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...

13. 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...

14. 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...

15. 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....

16. 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...

17. 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...

18. 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...

19. 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,...

20. 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,...

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