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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (67,896 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 408

1. Development of a low pH cementitious material to enlarge bioreceptivity - Manso Blanco, Sandra; Mestres Beà, Gemma; Ginebra Molins, Maria Pau; de Belie, Nele; Segura Pérez, Ignacio; Aguado de Cea, Antonio
This paper presents a laboratory investigation into the development of a low-pH cementitious material in order to enlarge bioreceptivity. Two different options were tested; reduction of Ordinary Portland Cement (OPC) pH and assessment of the suitability of another hydraulic binder with lower pH, Magnesium-Phosphate Cement (MPC). Regarding OPC, additions of acidic compounds such as boric acid and oxalic acid were investigated. Furthermore, an in-depth characterization of MPC was carried out to evaluate its suitability as a binder for concrete. For this purpose, physico-chemical as well as mechanical properties were tested.

2. Relevance of PEG in PLA-based blends for tissue engineering 3D-printed scaffolds - Serra, Tiziano; Ortiz Hernández, Mónica; Engel López, Elisabeth; Planell Estany, Josep Anton; Navarro Toro, Melba Eugenia
Achieving high quality 3D-printed structures requires establishing the right printing conditions. Finding processing conditions that satisfy both the fabrication process and the final required scaffold properties is crucial. This work stresses the importance of studying the outcome of the plasticizing effect of PEG on PLA-based blends used for the fabrication of 3D-direct-printed scaffolds for tissue engineering applications. For this, PLA/PEG blends with 5, 10 and 20% (w/w) of PEG and PLA/PEG/bioactive CaP glass composites were processed in the form of 3D rapid prototyping scaffolds. Surface analysis and differential scanning calorimetry revealed a rearrangement of polymer chains and a topography, wettability...

3. Improvement of the thermal stability of branched poly(lactic acid) obtained by reactive extrusion - Carrasco Alonso, Félix Ángel; Cailloux, Jonathan; Sanchez Jimenez, P.E.; Maspoch Rulduà, Mª Lluïsa
One-step reactive extrusion-calendering process (REX-calendering) has been used in order to obtain sheets of 1 mm from poly(lactic acid) modified with a styrene-acrylic multifunctional oligomeric agent. In a preliminary internal mixer study, torque versus time has been monitored in order to ascertain chain extender ratios and reaction time. Once all the parameters were optimized, reactive extrusion experiments have been performed. An enhanced general analytical equation has been developed in order to evaluate the kinetic parameters of the thermal degradation of PLA sheets manufactured by reactive extrusion. This improvement has consisted of replacing the n-order conversion function by a modified form...

4. Role of porosity and pore architecture in the in vivo bone regeneration capacity of biodegradable glass scaffolds - Sanzana, Edgardo; Navarro Toro, Melba Eugenia; Ginebra Molins, Maria Pau; Planell Estany, Josep Anton; Ojeda, Alvaro; Montecinos, Hernan
The aim of this work is to shed light on the role of porosity and pore architecture in the in vivo bone regeneration capacity of biodegradable glass scaffolds. A calcium phosphate glass in the system P2O5-CaO-Na2O-TiO2 was foamed using two different porogens, namely albumen and hydrogen peroxide (H2O2); the resulting three-dimensional porous structures were characterized and implanted in New Zealand rabbits to study their in vivo behavior. Scaffolds foamed with albumen displayed a monomodal pore size distribution centered around 150 m and a porosity of 82%, whereas scaffolds foamed with H2O2 showed lower porosity (37%), with larger elongated pores, and...

5. Extracellular calcium and CaSR drive osteoinduction in mesenchymal stromal cells - Gonzalez Vazquez, Arlyng; Planell Estany, Josep Anton; Engel López, Elisabeth
Bone is the main store of calcium and progenitor cells in the body. During the resorption process, the local calcium concentration reaches 8-40 mM, and the surrounding cells are exposed to these fluctuations in calcium. This stimulus is a signal that is detected through the calcium sensing receptor (CaSR), which modulates chemotactic and proliferative G protein-dependent signaling pathways. The objective of the present work is to evaluate the roles of extracellular calcium ([Ca2+](o)) and the CaSR in osteoinduction. Rat bone marrow mesenchymal stromal cells (rBMSCs) were stimulated with 10 mM of Ca2+. Several experiments were conducted to demonstrate the effect...

6. Novel peptide-based platform for the dual presentation of biologically active peptide motifs on biomaterials - Mas Moruno, Carlos; Fraioli, Roberta; Abericio, Fernando; Manero Planella, José María; Gil Mur, Francisco Javier
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...

7. Strengthening zones in the Co matrix of WC-Co cemented carbides - Konyashin, Igor Yu; Lachmann, Frank Friedrich; Ries, Bernd Heinrich; Mazilkin, Andrei A.; Straumal, Boris B.; Kübel, Christian; Llanes Pitarch, Luis Miguel; Baretzky, Brigitte
For conventional structural and tool materials, in particular WC-Co cemented carbides, hardness and wear-resistance can usually be increased only at the expense of toughness and strength. For the first time we have achieved a dramatically increased combination of hardness, wear-resistance, fracture toughness and strength as a result of precipitation of extremely fine nanoparticles in the cobalt binder of cemented carbides. These nanoparticles are similar to 3 nm in size, coherent with the Co matrix and consist of a metastable phase. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

8. Angiogenesis in bone regeneration: tailored calcium release in hybrid fibrous scaffolds - Castaño Linares, Óscar; Sachot, Nadège; Xuriguera Martin, Elena; Engel López, Elisabeth; Planell Estany, Josep Anton; Park, Jaegyun; Jin, Guang-Zhen; Kim, Tae-Hyun; Kim, Joong-Hyun; Kim, Hae-Won
In bone regeneration, silicon-based calcium phosphate glasses (Bioglasses) have been widely used since the 1970s. However, they dissolve very slowly because of their high amount of Si (SiO2 > 45%). Recently, our group has found that calcium ions released by the degradation of glasses in which the job of silicon is done by just 5% of TiO2 are effective angiogenic promoters, because of their stimulation of a cell-membrane calcium sensing receptor (CaSR). Based on this, other focused tests on angiogenesis have found that Bioglasses also have the potential to be angiogenic promoters even with high contents of silicon (80%); however,...

9. Effect of superelastic shape memory alloy wires on the impact behaviour of carbon fiber reinforced in situ polymerized poly(butylene terephthalate) composites - Aurrekoetxea Narbarte, Jon; Zurbitu, J.; Ortiz de Mendibil, I.; Aguirregomezkorta, A.; Sánchez Soto, Miguel; Sarrionandia, Mariasun
Low-velocity impact properties of shape memory alloy (SMA) wires and carbon fi ber reinforced poly (butylene terephthalate) obtained by resin transfer molding were characterized. At the subcritical regime the dissipated energy is not affected by the presence of the wires. However SMA has a positive effect on the maximum absorbed energy, since the maximum allowable load is higher. The contribution of the SMA wires to the higher impact performance of the hybrid composite is suggested to be due to their energy absorbing capability, and also to the high reversible force that acts as a healing force.

10. Propiedades mecánicas de residuos de PVC provenientes de cables eléctricos - Franco Urquiza, Edgar Adrian; Maspoch Rulduà, Mª Lluïsa
En este trabajo se evaluaron las propiedades mecánicas de desechos de cloruro de polivinilo (PVC) proveniente de cables eléctricos. El residuo contenía 60% de PVC , 30% de polietileno, 7% de goma y 3% de fracción metálica. La fracción metálica de separó 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 adjudicó a la heterogeniedad...

11. Estudio de la adhesión en uniones poliméricas sobreinyectadas rígido-rígido (ABS/SAN) - Dávila, Everling A.; Candal Pazos, Maria Virginia; Sánchez Soto, Miguel
El objetivo de esta investigación fue estudiar el efecto de las variables del proceso de sobre inyección sobre la resistencia de la unión adhesiva rígido–rígido entre un par de materiales poliméricos. Se emplearon como materiales el estireno –acrilonitrilo (SAN) y el acrilonitrilo–butadieno –estireno (ABS). Se evaluó el efecto de las condiciones de proceso (Psostenida, vinyección , Tfundido)del material sobreinyectado en la adhesión mediante ensayos mecánicos de tracción, trabajo esencial de fractura interfacial empleando geometría DENT, además de mecánica de la fractura interfacial elástico –lineal. Se obtuvo un incremento de la resistencia de unión adhesiva al aumentar la temperatura de fundido y la rugosidad de la superficie de contacto del sustrato con...

12. Efecto de las variables del proceso de inyección sobre la adhesión polímero-tela usando la técnica de decoración en molde - Dávila, Everling A.; Candal Pazos, Maria Virginia; Sánchez Soto, Miguel
El objetivo de esta investigación es estudiar el efecto de las variables del proceso de inyección sobre la adhesión entre un polímero y una tela utilizando la técnica de decoración en el molde. Se usaron fibras textiles y PEBD formándose una unión del tipo adhesivo. Se evaluó el efecto de las condiciones de proceso en la adhesión, aplicando una matriz de diseño de experimentos y se evaluó mediante la técnica de Pelado. Se obtuvo que la variable de mayor influencia en la adhesión es la temperatura de inyección, observándose que al incrementar la misma, la resistencia de la unión adhesiva...

13. La adhesión en uniones poliméricas sobreinyectadas rígido-rígido - Candal Pazos, Maria Virginia; Sánchez Soto, Miguel
En el mundo del procesamiento, especialmente en el moldeo por inyección, se busca mejorar y avanzar tecnológicamente con la finalidad de cumplir con las exigencias del mercado, el cual demanda procesos más eficientes, ciclos más cortos, mayor productividad y menores costos. La inyección multicomponente (bi-inyección o sobreinyección) es una nueva técnica del proceso de inyección que busca la unión de dos o más materiales diferentes de manera secuencial o simultánea, produciendo así piezas terminadas sin necesidad de realizar ensamblajes posteriores, modificando y/o mejorando sus propiedades finales.

14. Polycarbonate foams with tailor-made cellular structures by controlling the dissolution temperature in a two-step supercritical carbon dioxide foaming process - Gedler, Gabriel; Sousa Pais Antunes, Marcelo de; Velasco Perero, José Ignacio
Closed-cell polycarbonate foams were prepared using a two-step foaming process, which consisted of the initial dissolution of supercritical CO2(scCO2) into PC foaming precursors and their later expansion by heating using a double contact restriction method. The effects of the parameters of both CO2 dissolution and heating stages on the cellular structure characteristics as well as on the physical aging of PC in the obtained foams were investigated. A higher amount of CO2 was dissolved in PC with increasing the dissolution temperature from 80 to 100 ºC, with similar CO2 desorption trends and diffusion coefficients being found for both conditions. PC...

15. Foamlike xanthan gum/clay aerogel composites and tailoring properties by blending with agar - Wang, Liang; Schiraldi, David A.; Sánchez Soto, Miguel
Foamlike aerogel composites based on renewable xanthan gum (XG) and sodium montmorillonite clay (Na+- MMT) have been prepared using an environmentally friendly freeze-drying process. Additionally, the biobased polysaccharide agar was used to improve the properties of XG/clay aerogels. Fourier transform infrared spectroscopy showed molecular interactions between biopolymers and clay in the aerogel composites. A wide range of microstructures and mechanical properties were obtained with a minimal variation in the density by changing the blended ratio of xanthan gum and agar, with particular emphasis on the addition of 2.5% agar to XG/clay aerogels, which significantly enhanced the mechanical properties. Thermogravimetric analysis revealed that clay improved the thermal...

16. Pharmacophoric modifications lead to superpotent avß3 integrin ligands with suppressed a5ß1 activity - Neubauer, Stefanie; Rechenmacher, Florian; Brimioulle, Richard; Di Leva, Francisco Saverio; Bochen, Alexander; Sobahi, Tariq R.; Schottelius, Margret; Novellino, Ettore; Mas Moruno, Carlos; Marinelli, Luciana; Kessler, Horst
The selective targeting of the avß3 integrin subtype without affecting the structurally closely related receptor a5ß1 is crucial for understanding the details of their biological and pathological functions and thus of great relevance for diagnostic and therapeutic approaches in cancer treatment. Here, we present the synthesis of highly active RGD peptidomimetics for the avß3 integrin with remarkable selectivity against a5ß1. Incorporation of a methoxypyridine building block into a ligand scaffold and variation of different functional moieties led to avß3-antagonistic activities in the low nanomolar or even subnanomolar range. Furthermore, docking studies were performed to give insights into the binding modes...

17. Fatigue life of bioactive titanium dental implants treated by means of grit-blasting and thermo-chemical treatment - Gil Mur, Francisco Javier; Espinar Escalona, Eduardo; Llamas Carreras, Jose Maria; Sevilla Sánchez, Pablo
Objective: This study focuses on the fatigue behavior of titanium dental implants as-received, with a grit-blasted surface and with a new bioactive surface treatment (2Steps). Background: The 2Step process consists of (1) an initial grit-blasting process to produce a micro-rough surface, followed by (2) a combined thermo-chemical treatment that produces a potentially bioactive surface, that is, that can form an apatitic layer when exposed to biomimetic conditions in vitro. The 2Step treatment produced micro-rough and apatitic coating implants. Methods: Residual stresses were determined by means of X-ray diffraction. The fatigue tests were carried out at 37°C on 500 dental implants,...

18. Influence of the notch sharpening on the impact fracture toughness of ethylene-propylene block copolymers - Martínez Benasat, Antonio; Arencón Osuna, David; Rodríguez Pérez, Jesús; Salazar López, Alicia
The impact fracture toughness of several ethylene-propylene block copolymers has been evaluated using the traditional contact notch sharpening technique of tapping and a new non-contact technique based on femtolaser ablation. The fracture toughness values obtained with the specimens notched by the femtolaser ablation technique were always lower than the tapped specimens. The impact fracture toughness values of these block copolymers does not depend only on the ethylene content, but also the molecular weight has a remarkable influence. © 2014 Elsevier Ltd. All rights reserved.

19. Sharp indentation crystal plasticity finite element simulations: Assessment of crystallographic anisotropy effects on the mechanical response of thin fcc single crystalline films - Esque de los Ojos, Daniel; Ocenášek, J.; Alcalá Cabrelles, Jorge
Continuum crystal plasticity finite element modeling has been used to address size-effects during indentation of thin-metallic films. Berkovich indentation simulations were performed in the frame of continuum crystal plasticity to study the influence of a rigid fcc single-crystalline silicon substrate on a soft thin-metallic copper fcc single crystal film with different crystallographic orientations. It has been observed that crystallographic orientation of the indented plane has a great influence on the penetration depth at which substrate effects come into play, particularly in terms of hardness evolution. This effect has been related to the spatial arrangement of the active slip systems and...

20. Development and characterization of biphasic hydroxyapatite/ß-TCP cements - Gallinetti, Sara; Canal Barnils, Cristina; Ginebra Molins, Maria Pau
Biphasic calcium phosphate bioceramics composed of hydroxyapatite (HA) and ß-tricalcium phosphate (ß-TCP) have relevant properties as synthetic bone grafts, such as tunable resorption, bioactivity, and intrinsic osteoinduction. However, they have some limitations associated to their condition of high-temperature ceramics. In this work self-setting Biphasic Calcium Phosphate Cements (BCPCs) with different HA/ß-TCP ratios were obtained from self-setting a-TCP/ß-TCP pastes. The strategy used allowed synthesizing BCPCs with modulated composition, compressive strength, and specific surface area. Due to its higher solubility, a-TCP was fully hydrolyzed to a calcium-deficient HA (CDHA), whereas ß-TCP remained unreacted and completely embedded in the CDHA matrix. Increasing amounts...

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