Nonlinear waves in a chain of magnetically coupled pendula

A motivation for the study of reduced models like one-dimensional systems in Solid State Physics is the complexity of the full problem. In recent years our group has studied theoretically, numerically and experimentally wave propagation in lattices of nonlinearly coupled oscillators. Here, we present the dynamics of magnetically coupled pendula lattices. These macroscopic systems can model the dynamical processes of matter or layered systems. We report the results obtained for harmonic wave propagation in these media, and the different regimes of mode conversion into higher harmonics strongly influenced by dispersion and discreteness, including the phenomenon of acoustic dilatation of the chain, as well as some results on the propagation of localized waves i.e., solitons and kinks.Generalitat Valenciana APOSTD/2017/042Umiversitat Politècnica de València PAID-01-14Ministerio de Economía y Competitividad (MINECO), Spain FIS2015-65998-C2-2-PJunta de Andalucía 2017/FQM-28

Material-driven fibronectin assembly for high-efficiency presentation of growth factors

Growth factors (GFs) are powerful signaling molecules with the potential to drive regenerative strategies, including bone repair and vascularization. However, GFs are typically delivered in soluble format at supraphysiological doses because of rapid clearance and limited therapeutic impact. These high doses have serious side effects and are expensive. Although it is well established that GF interactions with extracellular matrix proteins such as fibronectin control GF presentation and activity, a translation-ready approach to unlocking GF potential has not been realized. We demonstrate a simple, robust, and controlled material-based approach to enhance the activity of GFs during tissue healing. The underlying mechanism is based on spontaneous fibrillar organization of fibronectin driven by adsorption onto the polymer poly(ethyl acrylate). Fibrillar fibronectin on this polymer, but not a globular conformation obtained on control polymers, promotes synergistic presentation of integrin-binding sites and bound bone morphogenetic protein 2 (BMP-2), which enhances mesenchymal stem cell osteogenesis in vitro and drives full regeneration of a nonhealing bone defect in vivo at low GF concentrations. This simple and translatable technology could unlock the full regenerative potential of GF therapies while improving safety and cost-effectiveness

A tough act to follow: collagen hydrogel modifications to improve mechanical and growth factor loading capabilities

[EN] Collagen hydrogels are among the most well-studied platforms for drug delivery and in situ tissue engineering, thanks to their low cost, low immunogenicity, versatility, biocompatibility, and similarity to the natural extracellular matrix (ECM). Despite collagen being largely responsible for the tensile properties of native connective tissues, collagen hydrogels have relatively low mechanical properties in the absence of covalent cross-linking. This is particularly problematic when attempting to regenerate stiffer and stronger native tissues such as bone. Furthermore, in contrast to hydrogels based on ECM proteins such as fibronectin, collagen hydrogels do not have any growth factor (GF)-specific binding sites and often cannot sequester physiological (small) amounts of the protein. GF binding and in situ presentation are properties that can aid significantly in the tissue regeneration process by dictating cell fate without causing adverse effects such as malignant tumorigenic tissue growth. To alleviate these issues, researchers have developed several strategies to increase the mechanical properties of collagen hydrogels using physical or chemical modifications. This can expand the applicability of collagen hydrogels to tissues subject to a continuous load. GF delivery has also been explored, mathematically and experimentally, through the development of direct loading, chemical cross-linking, electrostatic interaction, and other carrier systems. This comprehensive article explores the ways in which these parameters, mechanical properties and GF delivery, have been optimized in collagen hydrogel systems and examines their in vitro or in vivo biological effect. This article can, therefore, be a useful tool to streamline future studies in the field, by pointing researchers into the appropriate direction according to their collagen hydrogel design requirements.This work was supported by Medical Research Scotland, EPSRC (through a programme grant EP/P001114/1) and a programme of research funded by the Sir Bobby Charlton Foundation. M.S.S. acknowledges support from a grant from the UK Regenerative Medicine Platform 'Acellular/Smart Materials - 3D Architecture' (MR/R015651/1). The graphical abstract was created using BioRender.com.Sarrigiannidis, S.; Rey, JM.; Dobre, O..; González-García, C.; Dalby, M.; Salmerón Sánchez, M. (2021). A tough act to follow: collagen hydrogel modifications to improve mechanical and growth factor loading capabilities. Materials Today Bio. 10(1):1-22. https://doi.org/10.1016/j.mtbio.2021.10009812210

Protease-degradable microgels for protein delivery for vascularization

Degradable hydrogels to deliver bioactive proteins represent an emerging platform for promoting tissue repair and vascularization in various applications. However, implanting these biomaterials requires invasive surgery, which is associated with complications such as inflammation, scarring, and infection. To address these shortcomings, we applied microfluidics-based polymerization to engineer injectable poly(ethylene glycol) microgels of defined size and crosslinked with a protease degradable peptide to allow for triggered release of proteins. The release rate of proteins covalently tethered within the microgel network was tuned by modifying the ratio of degradable to non-degradable crosslinkers, and the released proteins retained full bioactivity. Microgels injected into the dorsum of mice were maintained in the subcutaneous space and degraded within 2 weeks in response to local proteases. Furthermore, controlled release of VEGF from degradable microgels promoted increased vascularization compared to empty microgels or bolus injection of VEGF. Collectively, this study motivates the use of microgels as a viable method for controlled protein delivery in regenerative medicine applications

Spatial behavior of acid mine drainage in a peculiar stream : physical-chemical evolution from the source until the temporarlly receptor in the Iberian Pyrite Belt

Publicado em "Proceedings of the Energy and Environment Knowledge Week 2014 (E2KW2014), ISBN 978-84-697-1162-0"The Iberian Pyrite Belt is a vast concentration of massive sulphide, located in the SW of the Iberian Peninsula. Historically, this area has undergone an intense mining activity, which has left a huge amount of mining facilities and unrestored waste dumps. Mineral-water interaction in the waste dumps is responsible for the generation of acid mine drainage (AMD), causing a strong impact in the water systems. The AMD occurs when the sulfide minerals are in the presence of atmospheric oxygen and humidity, suffering oxidation reactions. As a consequence, metals and acidity are mobilized into the receiving watercourses. Such conditions have created a unique scenario in the world by the extreme degradation that characterizes the network of channels and streams in the IPB. In this context, widely described in the scientific literature, the present study aims to monitoring a singular channel affected by AMD (Campanario stream), from its origin (in the waste dump) to its confluence with an unpolluted stream. Such monitoring procedure will allow characterizing the physicochemical evolution and the mineral-water processes that regulate it

Four abandoned mines, one acid mine drainage affected river and an unsolved issue for a water supply reservoir

Publicado em "Proceedings of the Energy and Environment Knowledge Week 2014(E2KW2014)". ISBN 978-84-697-1162-

Acoustic behavior of the VEGA launch pad environment

[EN] The acoustic pressure levels experienced by the spacecraft and launchers during the lift-off is due among other factor by the reflection of the sound waves on the launch pad. The acoustic load distribution in the area of the launcher depends on the geometric, mechanical and acoustic characteristics of the ground facilities. This work is intended to study the acoustic environment of the launch pad. A numerical and experimental investigation is developed in order to study in the linear regime the acoustic behaviour of a subscale model of the VEGA's launch pad. The acoustic measurements are performed in an anechoic chamber using an electroacoustic source that emits incoherent noise, mimicking the real acoustic source. The acoustic pressure field is measured at different positions in front of the launch pad mock-up, in the area where the acoustic waves are reflected. Among the future perspectives of this work is to study and develop new methods for the mitigation of the sound pressure levels.Authors acknowledge the support of the European Space Agency under contract ¿Sonic Crystals For Noise Reduction At The Launch Pad¿ ESA ITT 1-7094 (ITI) and the 441-2015 Co-Sponsered PhD ¿Acoustic Reduction Methods for the Launch Pad¿. The work was supported by Spanish Ministry of Economy and Innovation (MINECO) and European Union FEDER through project FIS2015-65998-C2-2. Authors aknowledge Dhéric Mutel, Cyril Bernard and Clément Jost for their contribution to this workPicó Vila, R.; Herrero-Durá, I.; Sánchez Morcillo, VJ.; Salmerón-Contreras, LJ.; García-Raffi, LM. (2016). Acoustic behavior of the VEGA launch pad environment. Universidade do Porto. 1-6. http://hdl.handle.net/10251/181097S1

Chitosan microparticles as injectable scaffolds for tissue engineering applications

[Excerpt] Microparticles may be used as a support for the adhesion and proliferation of cells. Therefore, the combination of isolated particles and previously incubated cells on their surface may have potential to be used, in the form of a suspension with media, as an injectable scaffold in the context of tissue regeneration: on expects that the particles might agglomerate after the implantation as a consequence of cells proliferation and extracellular matrix production. [...]info:eu-repo/semantics/publishedVersio

Solitary waves in nonlinear phononic crystals

[EN] We discuss two possible regimes of solitary wave formation in acoustic layered media. In the weakly dispersive limit, KdV-type solitons are formed, consisting of broad pulses with a width much larger than the lattice periodicity. Such KdV solitons are shown to exist even far from the weakly dispersive conditions. On the other hand, in the strongly dispersive regime, gap acoustic solitons are demonstrated. They are formed by a fast carrier wave inside the band-gap of the structure, near the Bragg frequency (whose propagation is not allowed in the case of linear waves), modulated by a wide envelope, whose width lies inside the gap. Gap solitons propagate slower than linear waves, or can be even reach a stationary non-propagating state within the medium. The parameters for a realistic acoustic medium supporting both types of solitary waves are discussedThe work was supported by Spanish Ministry of Economy and Innovation (MINECO) and European Union FEDER through project FIS2015-65998-C2-2.Mehrem, A.; Picó Vila, R.; Sánchez Morcillo, VJ.; García-Raffi, LM.; Salmerón-Contreras, LJ.; Jimenez, N.; Staliunas, K. (2016). Solitary waves in nonlinear phononic crystals. Universidade do Porto. 1-7. http://hdl.handle.net/10251/183355S1

Gap Solitons in acoustic layered media

[EN] In this work we study numerically the existence of gap solitons in an acoustic media. To approach the problem a set of coupled-mode equations are given. In order to obtain a solitary wave in a real media, it is necessary of two phenomena, dispersion and nonlinearity. Acoustic media, usually can present nonlinearity but also low dispersions. To increase dispersion, it is proposed to use a multi-layered medium, a kind of sonic crystal in 1D, that it is demonstrated to have high dispersion near some frequency bands. In this kind of media, it is possible to observe soliton wavesThis research was partially supported by Ministerio de Economía y ompetitividad under grant FIS2015-65998-C2-2. LJSC and AM acknowledge UPV for redoctoral contract FPI-Subprograma 1Salmerón Contreras, LJ.; García-Raffi, LM.; Jimenez, N.; Mehrem, A.; Picó Vila, R.; Sánchez Morcillo, VJ.; Staliunas, K. (2016). Gap Solitons in acoustic layered media. Universidade do Porto. 1-4. http://hdl.handle.net/10251/181071S1