First-order phase transition in a 2D random-field Ising model with conflicting dynamics

The effects of locally random magnetic fields are considered in a nonequilibrium Ising model defined on a square lattice with nearest-neighbors interactions. In order to generate the random magnetic fields, we have considered random variables $\{h\}$ that change randomly with time according to a double-gaussian probability distribution, which consists of two single gaussian distributions, centered at $+h_{o}$ and $-h_{o}$, with the same width $\sigma$. This distribution is very general, and can recover in appropriate limits the bimodal distribution ($\sigma\to 0$) and the single gaussian one ($ho=0$). We performed Monte Carlo simulations in lattices with linear sizes in the range $L=32 - 512$. The system exhibits ferromagnetic and paramagnetic steady states. Our results suggest the occurence of first-order phase transitions between the above-mentioned phases at low temperatures and large random-field intensities $h_{o}$, for some small values of the width $\sigma$. By means of finite size scaling, we estimate the critical exponents in the low-field region, where we have continuous phase transitions. In addition, we show a sketch of the phase diagram of the model for some values of $\sigma$.Comment: 13 pages, 9 figures, accepted for publication in JSTA

Development and characterization of an injectable dextrin-based hydrogel for bone regeneration

Bone is a dynamic, highly vascularized tissue that remodels itself continuously over an individual ́s lifetime. It plays several important roles in maintaining homeostasis of the body systems [ 1 , 2 ] . However, this regenerative capac ity is limited and, as in the case of large bone defects, where the template for an orchestrated regeneration is absent, surgical proce dures are needed [ 2 ] . In this respect , bone tissue engineering is a very challe nging and promising field given the need to mimic bone mechanical and biological functions and also due to the failure of current orthoped ic implants. The general concept consists in the development of three - dimensional scaffolds, from biocompatible materials (natu ral or synthetic), which confer temporary support for the regeneration of bone tissue, while the scaffold itself will be resorbed and replaced by new ly formed tissue [ 2 , 3 ] . Hydrogels are cross - linked networks made of natural or synthetic polymers, which are able to support high water contents [ 4 ] . These materials are usua lly biocompatible, have the ability to mimic physiological conditions, promote an environment that can protect cells or unstable drugs, their physical characteristics can be controlled to some extent and some can be injected in vivo . These features make th em attractive materials in the biomedical field for cell encapsulation, drug or gene delivery or to act as an interfa ce between tissue and materials [ 4 - 7 ] . Natural polymers are advantageous for this kind of applications since they are cheap raw materials, bear a great biocompatibility and are usually biodegradable [ 8 ] . Dextrin is low molecular weight carbohydrate, generally regarded as safe (GRAS), obtained from partial hydrolysis of starch or glycogen [ 9 ] . It is a glucose polymer linked by α - 1,4 glycosidic linkages with some degree of branching due to the presence of α - 1,6 bonds [ 10 ] . I t is biocompatible and non - immunogenic, degradable by α - amylases and can undergo renal clearance avoiding tissue accumulation [ 11 , 12 ] . This work describes the preparation and characterization of an injectable dextrin - bas ed hydrogel (oDex) able to incorporate nanoparticles , cells, biomolecules or Bonelike ® granules [ 13 ] . Bonelike ® is a Biosckin - molecular and cell therapies S.A. proprietary synthetic bone graft, and the outcome of the project will result in a novel injectable presentation of this product. The hydrogel was produced by dextrin oxidation with sodium periodate followed by cross - linking with a dihydrazide [ 14 ] . In vitro characterization of oDex hydrogel has shown acceptable m echanical properties, overall good biocompatibility and the ability to be combined with other materials such as a nanogel and urinary bladder matrix, without affecting its structure. The cytotoxicity of the free dihydrazide was evaluated and only a mild in hibitory effect on cell proliferation was observed for the concentration used in the hydrogel crosslinking. The biocompatibilit y of oDex hydrogels was confirmed through the encapsulation of cells, which were able to endure the gelation process. Subcutaneou s implants were performed in Sasco Sprague Dawley rats in order to evaluate the inflammatory response and systemic effects of oDex hydrogels and their combination with Bonelike ® and human mesenchymal stem cells isolated from umbilical cord’s Wharton jelly. After 3 and 15 days post - implantation, a quantitative evaluation of both responses was performed according to ISO 10993 by a scoring system leading to a classification of the implanted material as s light irritant even when associated to Bonelike ® or to the cellular system. The performance of oDex hydrogel combined with Bonelike granules and/or UBM in bone defects was investigated in New Zealand rabbits. Bone defects in several anatomical locations (t ibiae and cranium) of non - critical and critical size were filled with those materials. Histological analysis showed that oDex does not constitute a barrier for cellular colonization and proliferation since the defects that were filled with these materials presented a higher degree of regeneration and a higher amount of collagen fibers with higher organization degrees, when compared with the empty defects. Even though oDex hydrogels purpose is to act as an injectable carrier for osteoconductive materials, li ke Bonelike ® granules, the hydrogel itself seems to assists the regenerative pro cess when compared with the empty defects. This is due to the 3D supp ort conferred by hydrogels that facilitates cell migration to the defect site. Moreover, the presence of UB M strongly stimulates the bone regeneration, for levels comparable with the Bonelike ® conditions, since an increase in cellular colonization and organization in the defect site can be denoted. A sterilization protocol for oDex hydrogels by gamma and beta r adiation was investigated through irradiation of oxidized dextrin solutions. Despite b oth kinds of radiation induced slight differences in the storage modulus of the hydrogels, indicating the occurrence of chain scission/cross - linking effects on the dextri n cha in, all materials were gelable after the irradiation treatments . These effects seem to not be dose or temperature dependent and the irradiation process in liquid or solid state also does not induce major differences in the rheology of the final hydrog els. Due to its known advantages, gamma radiation seems to be a suitable sterilization method for oxidized dextrin solutions. The stability of gamma irradiated dextrin solutions was evaluated up to 8 months. Despite the increase of storage modulus of the h ydrogels over the time, this effect does not constitute a disadvantage since it improves elastic behavior of the hydrogels. oDex hydrogels provides a system that can carry and stabilize cells, nanogels, Bonelike ® granules and other biomolecules. It is a pr omising biomaterial due to its biocompatibility, and potential to promote an adequate environment for bone regeneration. Its injectability allows a minimal invasive surgical procedure with decreased patient morbidity, lower risk of infection and reduced sc ar formation. This work has been developed in the scope of an European project that allowed collaborations with research groups, which have complementary expertise. The tight collaboration between University of Minho and Bioskin S.A. company, envisioning t echnology transfer and product valorization, has resulted in a published international patent of the product ( WO2011070529A2 ) [ 15 ] . Currently, a new set of pre - clinical trials in sheep model s are being planned as well as the submission of a request for the authorization for the clinical trialsGrant SFRH/BD/64571/2009 from Fundação para a Ciência e Tecnologia (FCT), Portugal. We thank FCT funding through EuroNanoMed ENMED/0002/2

Pinturas murales de la casa de Ariadna (Pompeya, Italia): un estudio multidisciplinar de su estado actual enfocado a una futura restauración y conservación preventiva

[EN] This paper deals with the development of a multidisciplinary study on the current state of conservation of Ariadne’s house (Pompeii, Italy), a domus of great archaeological value. The aim of this study is to undertake the preventive conservation actions required and increase the knowledge about its conservation and to generate discussions and points of view for a future restoration. Environmental studies, electromagnetic radiation measurements, study of materials and a photographical study were carried out. Those studies revealed that the rooftops covering the analyzed rooms resulting in adverse weather conditions causing grave damage to the conservation of the wall paintings. Thus, between 2009-2010 the rooftops were changed and new environmental studies were conducted. Studies of materials showed that the paintings match in execution and composition with those reported by other authors. The salts from modern mortars from previous restorations were affecting frescoes, also it is described a thin grayish surface layer from environmental contaminants.[ES] Este trabajo desarrolla un estudio multidisciplinar sobre el actual estado de conservación de la casa de Ariadna (Pompeya, Italia), domus de gran valor arqueológico. El objetivo es aumentar el conocimiento del estado actual de conservación de la casa para la discusión de una futura restauración. Para ello se realizaron estudios ambientales, mediciones de radiación electromagnética, estudio de materiales y un estudio fotográfico. Los estudios revelaron que los tejados que cubrían las salas analizadas estaban originando unas condiciones climatológicas adversas que se traducían en un grave daño para la conservación de las pinturas murales. Entre 2009-2010 se cambiaron las cubiertas y los estudios ambientales fueron repetidos. Los estudios de materiales demostraron que las pinturas coinciden en ejecución y composición con las señaladas por otros autores. Las sales procedentes de morteros modernos de anteriores restauraciones afectaban a las pinturas, también se describe una fina capa superficial de tonalidad grisácea procedente de contaminantes ambientales.This work was partially supported by the Spanish "Ministerio de Ciencia e Innovacion" under projects HAR2010-21944-C02-01 and HAR2010-21944-C02-02. The authors are grateful to J. Minguez for his English grammar corrections.Pérez García, MDC.; García Diego, FJ.; Merello Giménez, P.; D'antoni, P.; Fernández Navajas, A.; Ribera I Lacomba, A.; Ferrazza, L.... (2013). Ariadne's house (Pompeii, Italy) wall paintings: A multidisciplinary study of its present state focused on a future restoration and preventive conservation. Materiales de Construcción. 63(311):449-467. https://doi.org/10.3989/mc.2012.00812S4494676331

Ising critical behavior of a non-Halmiltonian lattice system

We study steady states in d-dimensional lattice systems that evolve in time by a probabilistic majority rule, which corresponds to the zero-temperature limit of a system with conflicting dynamics. The rule satisfies detailed balance for d=1 but not for d>1. We find numerically nonequilibrium critical points of the Ising class for d=2 and 3

Beverage waste derived biomaterials for tissue engineering

The waste material from the beverage manufacturing industry was valorized as a renewable source for the manufacture of biomaterials capable of acting as scaffolds for tissue engineering. Environmentally friendly design of both structural and textural properties produced biomaterials whose in vivo properties were similar to those of a commercial biomaterial.The authors wish to acknowledge the economic support of the Spanish Ministry of Economy and Competitiveness for the Research Projects “Valorisation of agroindustrial residues towards biomaterials to be used in dental implants (Ecomaterials)” (IPT-2011-1935-310000), “Valorisation of agri-residues for advanced uses” (201460E105) and “Development of substances and materials from agriresidues for biomedical uses” (201480E103)