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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (82,639 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 489

1. In vivo performance of novel soybean/gelatin-based bioactive and injectable hydroxyapatite foams - Kovtun, Anna; goeckelmann, Melanie J.; Montufar Jiménez, Edgar Benjamin; Ginebra Molins, Maria Pau; Planell Estany, Josep Anton; Santin, Matteo; Ignatius, Anita
Major limitations of calcium phosphate cements (CPCs) are their relatively slow degradation rate and the lack of macropores allowing the ingrowth of bone tissue. The development of self-setting cement foams has been proposed as a suitable strategy to overcome these limitations. In previous work we developed a gelatine-based hydroxyapatite foam (G-foam), which exhibited good injectability and cohesion, interconnected porosity and good biocompatibility in vitro. In the present study we evaluated the in vivo performance of the G-foam. Furthermore, we investigated whether enrichment of the foam with soybean extract (SG-foam) increased its bioactivity. G-foam, SG-foam and non-foamed CPC were implanted in...

2. Drug delivery from injectable calcium phosphate foams by tailoring the macroporosity-drug interaction - Pastorino Carraz, David; Canal Barnils, Cristina; Ginebra Molins, Maria Pau
In this work, novel injectable calcium phosphate foams (CPFs) were combined with an antibiotic (doxycycline) to design an innovative dosage form for bone regeneration. The material structure, its drug release profile and antibiotic activity were investigated, while its clinical applicability was assessed through cohesion and injectability tests. Doxycycline had a clear effect on both the micro and macro structure of the CPFs, owing to its role as a nucleating agent of hydroxyapatite and to a drying effect on the paste. Doxycycline-loaded CPFs presented interconnected macroporosity, which increased drug availability compared with calcium phosphate cements, and was a critical parameter controlling...

3. Effect of the filler on the nanomechanical properties of polypropylene in contact with paraffinic phase change material - Giró Paloma, Jessica; Rayón Encinas, Emilio; Roa Rovira, Joan Josep; Martínez López, Monica; Fernández Renna, Ana Inés
As the changes on the mechanical properties with depth of indentation provide valuable information that may be suitable for design purposes, nanoindentation is an adequate technique for investigating the nanomechanical changes in the surface and in the inner polymers. This research focuses on the study of the nanomechanical properties of two grades of polypropylene (PP) after the long term exposure to an organic fluid, such as paraffin wax used as a phase change materials (PCM). PCM are used for thermal energy storage (TES) in buildings applications for passive systems or heating and cooling usages. In any of these uses PCM must...

4. The role of adhesive forces and mechanical interaction on material transfer in hot forming of aluminium - Pujante, Jaume; Vilaseca, Montserrrat; Casellas, Daniel; Riera Colom, María Dolores
In this work, the mechanisms resulting in transfer of aluminium on hot forming tools have been analysed by means of two separate laboratory tests. The influence of chemical affinity in aluminium adhesion has been studied in contact tests, measuring the force used in pulling at low velocity an aluminium ball pressed against a tool surface. The role of mechanical interaction has been investigated through ball-on-disc sliding tests at high temperature, using tool steel discs with different surface finish against an aluminium counterpart. These tests have been used for the evaluation of different strategies in adhesive wear reduction, including different tool...

5. Characterization of cutting parameters in the minimum quantity lubricant (MQL) machining process of a gearbox - Travieso Rodriguez, Jose Antonio; Gómez Gras, David; García Vilana, Silvia; Mainau Noguer, Ferran; Jerez Mesa, Ramón
This paper aims to find the key process parameters for machining different parts of an automobile gearbox, commissioned by a company that needs to replace with the MQL lubrication system their current machining process based on cutting fluids. It particularly focuses on the definition of appropriate cutting parameters for machining under the MQL condition through a statistical method of Design of Experiments (DOE). Using a combination of recommended parameters, significant improvements in the surface roughness of different machined parts are shown. Production costs are also reduced by decreasing expenses on lubricants and by optimizing the cycle time reached under the...

6. Plastic deformation and damage induced by fatigue in twip steels - Roa Rovira, Joan Josep; Fargas Ribas, Gemma; Calvo Muñoz, Jessica; Jiménez Piqué, Emilio; Mateo García, Antonio Manuel
Twinning Induced Plasticity steels exhibit a high strain hardening rate which translates into a remarkable combination of ductility and strength. A thorough experimental approach was performed by advanced characterization techniques to study the deformation mechanisms developed under high cycle fatigue conditions. Results clearly lay out that the cumulative strain damage leads to strengthening but also induces micro-cracks at the intersection of twin boundaries which promote fracture

7. Toughened carbon fiber fabric-reinforced pCBT composites - Abt, Tobias Martin; Krager-Kocsis, Joseph; Sánchez Soto, Miguel
Toughened carbon fiber-fabric reinforced polymerized cyclic butylene terephthalate (pCBT) composites were obtained by chemical modification of cyclic butylene terephthalate (CBT) with small amounts of epoxy resin and isocyanates as chain extenders. Homogeneous CBT/epoxy and CBT/isocyanate blends were prepared by melt blending the components in a lab-scale batch mixer at low temperatures and high shear rate. Melt blending was stopped before the ring-opening polymerization of CBT could start. The modified CBT was the starting material for carbon fiber fabric-reinforced pCBT composites (fiber content at about 65 wt%) which were prepared by ring-opening polymerization during compression molding using a simple powder prepreg method. Interlaminar shear strength, flexural strength, and failure strain of the chemically modified composites increased up...

8. Role of ECM/peptide coatings on SDF-1a triggered mesenchymal stromal cell migration from microcarriers for cell therapy - Levato, Riccardo; Planell Estany, Josep Anton; Mateos Timoneda, Miguel Ángel; Engel López, Elisabeth
Many cell therapies rely on the ability of mesenchymal stromal cells (MSCs) to diffuse and localize throughout the target tissue-such as tumoral and ischemic tissues-, in response to specific cytokine signals, rather than being concentrated at the site of implantation. Therefore, it is fundamental to engineer biomaterial carriers as reservoirs, from which cells can migrate, possibly in a controlled manner. In this work, microcarriers (µCs) made of polylactic acid are characterized as MSC delivery vehicles capable of modulating key chemotactic pathways. The effect of different functionalization strategies on MSC migratory behavior from the µCs is studied in vitro in relation...

9. Transportation conditions for prompt use of Ex Vivo expanded and freshly harvested clinical-grade bone marrow mesenchymal stromal/stem cells for bone regeneration - Varonesi, E; Murgia, A; Caselli, A; Grisendi, G; Piccinno, M.S; Rasini, V; Giordano, Roberto; Montemurro, T; Bourin, P; Sensebe, L; Rojewski, M.T; Schrezenmeier, H; Layrolle, P; Ginebra Molins, Maria Pau; Penaitescu, C.B; Gomez Barrena, E; Catani, F; Paolucci, P; Burns, J.S; Dominici, M
Successful preliminary studies have encouraged a more translational phase for stem cell research. Nevertheless, advances in the culture of human bone marrow-derived mesenchymal stromal/stem cells (hBM-MSC) and osteoconductive qualities of combined biomaterials can be undermined if necessary cell transportation procedures prove unviable. We aimed at evaluating the effect of transportation conditions on cell function, including the ability to form bone in vivo, using procedures suited to clinical application. hBM-MSC expanded in current Good Manufacturing Practice (cGMP) facilities (cGMP-hBM-MSC) to numbers suitable for therapy were transported overnight within syringes and subsequently tested for viability. Scaled-down experiments mimicking shipment for 18 h...

10. Mechanical properties and in vitro biological response to porous titanium alloys for intervertebrae implants - Gil Mur, Francisco Javier; Punset Fusté, Miquel; Guillem Martí, Jordi; Molmeneu Trias, Meritxell; Calero, Jose Antonio
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 µm for fine...

11. Silver deposition on titanium surface by electrochemical anodizing process reduces bacterial adhesion of Streptococcus sanguinis and Lactobacillus salivarius - Gil Mur, Francisco Javier; Godoy Gallardo, María; Mas Moruno, Carlos; Fernandez Calderon, M.Coronada; Perez Giraldo, Ciro; Manero Planella, José María; Albericio Palomera, Fernando; Rodríguez Rius, Daniel
Bacterial infection represents a major cause of implant failure in dentistry. A common approach to overcoming this issue and treating peri-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...

12. Relevance of the setting reaction to the injectability of tricalcium phosphate pastes - Ginebra Molins, Maria Pau; Montufar Jiménez, Edgar Benjamin; Maazouz, Yassine
The ai m of the present work was to analyze the influence of the setting reaction on the injectability of tricalcium phosphate (TCP) pastes. Even if the injection was performed early after mixing powder and liquid, powder reactivity was shown to play a significan t role in the injectability of TCP pastes. Significant differences were observed between the injection behavior of non - hardening β - TCP pastes and that of self - hardening α - TCP pastes. The differences were more marked at low liquid - to - powder ratios, using fi ne powders and injecting through thin needles. α - TCP was in general less injectable than β - TCP and required higher injection loads. Moreover, clogging...

13. Hardness of FRHC-Cu Determined by Statistical Analysis - Roa Rovira, Joan Josep; Martínez López, Mónica; Rayón Encinas, Emilio; Ferrer Cruselles, Núria; Espiell Álvarez, Ferran; Segarra Rubi, Merce
A statistical indentation method has been employed to study the hardness value of fire-refined high conductivity copper, using nanoindentation technique. The Joslin and Oliver approach was used with the aim to separate the hardness (H) influence of copper matrix, from that of inclusions and grain boundaries. This approach relies on a large array of imprints (around 400 indentations), performed at 150 nm of indentation depth. A statistical study using a cumulative distribution function fit and Gaussian simulated distributions, exhibits that H for each phase can be extracted when the indentation depth is much lower than the size of the secondary phases. It is found that the...

14. A novel peptide-based platform for the dual presentation of biologically-active peptide motifs on biomaterials - Gil Mur, Francisco Javier; Mas Moruno, Carlos; Fraioli, Roberta; Albericio Palomera, Fernando; Manero Planella, José María
Biofunctionalization of metallic materials with cell adhesive molecules derived from the extracellular matrix is a feasible approach to improve cell–material interactions and enhance the biointegration of implant materials (e.g., osseointegration of bone implants). However, classical biomimetic strategies may prove insufficient to elicit complex and multiple biological signals required in the processes of tissue regeneration. Thus, newer strategies are focusing on installing multifunctionality on biomaterials. In this work, we introduce a novel peptide-based divalent platform with the capacity to simultaneously present distinct bioactive peptide motifs in a chemically controlled fashion. As a proof of concept, the integrin-binding sequences RGD and PHSRN...

15. Low modulus Ti–Nb–Hf alloy for biomedical applications - González, Marta; Peña, Javier; Gil Mur, Francisco Javier; Manero Planella, José María
ß-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 °C. The cell response was studied by means of cytotoxicity evaluation, cell adhesion and proliferation measurements. The...

16. Implant-abutment connections: influence of the design on the microgap and their fatigue and fracture behavior of dental implants - Gil Mur, Francisco Javier; Herrero Climent, Mariano; Lázaro, Pedro; Rios Santos, Jose Vicente
Microgap between implant and abutment can produce biological and mechanical problems such as peri-implantitis and/or fatigue failures. The aim of this study was to evaluate microgap size and fatigue behavior of external and internal connections. In both systems the torque to tighten the abutment screw of single crown abutments was 45 Ncm. Fifty implants for each connection type were studied. One subgroup (n=5) was used by the observation and evaluation of the microgap, other (n=5) was tested for fracture strength and the other (n=40) was subjected to dynamic loading. The internal connection presents a lower microgap than the external ones. From fatigue results,...

17. Sheets of branched poly(lactic acid) obtained by one step reactive extrusion calendering process: Physical Aging and Fracture Behaviour - Cailloux, Jonathan; Santana Pérez, Orlando Onofre; Franco-Urquiza, Edgar; Bou, Jordi; Carrasco Alonso, Félix Ángel; Maspoch Rulduà, Mª Lluïsa
Peer Reviewed

18. Mechanical Properties of a New Superelastic Polymer Orthodontic Archwire - Gil Mur, Francisco Javier; Manero Planella, José María; Rupérez de Gracia, Elisa
A new thermoplastic polymer for orthodontic applications was obtained and extruded into wires with round and rectangular cross sections. We evaluated the potential of new aesthetic archwire: tensile, three point bending, friction and stress relaxation behaviour, and formability characteristics were assessed. Stresses delivered were generally slightly lower than typical beta-titanium and nickel-titanium archwires. The polymer wire has good instantaneous mechanical properties; tensile stress decayed about 2% over 2h depending on the initial stress relaxation for up to 120h. High formability allowed shape bending similar to that associated with stainless steel wires. The friction coefficients were lower than the metallic conventional...

19. Methods for the preparation of doxycycline-loaded phb micro- and nano-spheres. - Gil Mur, Francisco Javier; Rodríguez Contreras, Alejandra María; Ginebra Molins, Maria Pau; Canal Barnils, Cristina; Calafell Monfort, Margarita; Marqués Calvo, M. Soledad
Natural and synthetic biodegradable polymers have been investigated for controlled drug release. Poly(3-hydroxybutyrate) can be produced by bacteria and is remarkable for this application due to its excellent biocompatibility and biodegradability. The objective of this work was to study different drug-entrapment and emulsification methods for the obtaining of doxycycline-loaded PHB micro- and nano-spheres. The micro-/nano-particles were prepared by polymer precipitation via dialysis, simple emulsion (O/W) or multiple emulsion (W1/O/W2) applying solvent evaporation in the last two cases. This was carried out either by ultrasonication, dripping and/or high speed stirring. Different processing conditions were varied in order to evaluate their influence on morphology, size, and drug entrapment capabilities. The highest...

20. Tendencias en el campo de la fundición inyectada - Martín Fuentes, Enrique; Menargues Muñoz, Sergi; Picas Barrachina, Josep Anton; Baile Puig, Maria Teresa
Este artículo recoge una visión actualizada de la problemática en el campo de la fundición inyectada, fundamentalmente en la industria de componentes de aluminio. Se muestran las principales limitaciones y se expone cómo la conformación en estado semisólido es una de las alternativas para resolver parte de esos inconvenientes.

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