Surfactant effect in heteroepitaxial growth. The Pb - Co/Cu(111) case

A MonteCarlo simulations study has been performed in order to study the effect of Pb as surfactant on the initial growth stage of Co/Cu(111). The main characteristics of Co growing over Cu(111) face, i.e. the decorated double layer steps, the multiple layer islands and the pools of vacancies, disappear with the pre-evaporation of a Pb monolayer. Through MC simulations, a full picture of these complex processes is obtained. Co quickly diffuses through the Pb monolayer exchanging place with Cu atoms at the substrate. The exchange process diffusion inhibits the formation of pure Co islands, reducing the surface stress and then the formation of multilayer islands and the pools of vacancies. On the other hand, the random exchange also suppress the nucleation preferential sites generated by Co atoms at Cu steps, responsible of the step decoration.Comment: 4 pages, latex, 2 figures embedded in the tex

Condiciones ambientales y diferenciación social en los patrones de movilidad: el caso de las desigualdades de género en el Área Metropolitana de Lisboa

Place determinants and social dimensions interact to produce mobility patterns. The article seeks to measure to what extent the physical and social conditions of the residency place modulate the intensity of mobility particularly in what concerns gender inequalities. To do so, we first present the theoretical framework, which guides our perspective on mobility inequalities and the geographical focus: Lisbon Metropolitan Area (LMA). Secondly, using logistic regression on representative data from a survey to LMA inhabitants we elaborate on the concept of environmental motility and its relationship to various types of inequality. Lastly, we systematize a view on accumulated inequalities examining how local environments may increase the mobilities gender gap.info:eu-repo/semantics/publishedVersio

Intentional and accidental poisoning of wild and domestic animals in Spain: differences between regions

[ES]: En este estudio se han analizado 1.157 casos sospechosos de intoxicación de fauna silvestre y doméstica en el medio natural (1.800 animales y 340 cebos) procedentes de diversas Comunidades Autónomas (CCAA) españolas durante el periodo 2004-2010. Se ha detectado un 41,2% de casos positivos (40,8% de animales y 52,6% de cebos). En los carnívoros domésticos la detección del tóxico llegó al 71,4%, lo que indica su utilidad como centinelas del uso de veneno en el medio natural. El 78,3% de los animales que fueron positivos a los análisis toxicológicos han sido considerados como intoxicaciones intencionadas. Las aves rapaces diurnas fueron el grupo más afectado por las intoxicaciones (43,6% del total de animales positivos), seguido de los mamíferos carnívoros (27,1%). Los tóxicos más frecuentemente detectados fueron insecticidas anticolinesterásicos (cebos/animales: 80,4%/65,8%), seguidos de rodenticidas anticoagulantes (5%/19,6%), estricnina (2,2%/6,5%) y arsénico (4,5%/2,3%). De las diferencias observadas entre CCAA destaca la preponderancia en el uso de estricnina en Asturias, rodenticidas anticoagulantes en Castilla y León, insecticidas organofosforados en Aragón, insecticidas carbamatos en Castilla-La Mancha y Madrid, y la aparición de otros venenos, como á-cloralosa o barbitúricos, en Cataluña. En resumen, el 82,3% de las intoxicaciones intencionadas fueron debidas a anticolinesterásicos y el 85,5% de las accidentales a rodenticidas anticoagulantes. En futuras regulaciones de plaguicidas y biocidas se debería tener en cuenta el riesgo del uso ilegal en la preparación de cebos envenenados que comporta la comercialización de formulados con alta riqueza de ingredientes activos con baja DL50.[EN]: In this study we have analyzed 1,157 suspected cases of poisoning of wild and domestic animals in the natural environment (1,800 animals and 340 baits) from different Spanish regions during the period 2004- 2010. We detected 41.2% of positive cases (40.8% of animals and 52.6% of baits). In domestic carnivores detection of toxic compounds reached 71.4%, indicating its usefulness as sentinels of the use of poison in the environment. In those animals positive for toxicological analysis, 78.3% have been considered as intentional poisonings. The diurnal raptors were most affected by poisoning (43.6% of positives), followed by carnivorous mammals (27.1%). The most frequently detected toxicants were anticholinesterase insecticides (baits/animals: 80.4%/65.8%), followed by anticoagulant rodenticides (5%/19.6%), strychnine (2.2%/6.5%) and arsenic (4.5%/2.3%). The differences observed between regions underlines the dominance in the use of strychnine in Asturias, anticoagulant rodenticides in Castilla y Leon, organophosphate insecticides in Aragon, carbamate insecticides in Castilla-La Mancha and Madrid, and the emergence of other poisons, such as á-chloralose or barbiturates, in Catalonia. In summary, 82.3% of intentional poisonings were due to anticholinesterase pesticides and 85.5% of accidental anticoagulant rodenticides. Future regulations of pesticides and biocides should take into account the risk of illegal use in the preparation of poisoned baits which involves the marketing of formulations with high richness of active ingredients with low LD50.Este trabajo ha sido financiado mediante los contratos establecidos entre el IREC y las CCAA de Aragón, Castilla-La Mancha, Cataluña, Madrid, Asturias, Cantabria, Navarra y País Vasco para llevar a cabo análisis toxicológicos de fauna salvaje.Peer Reviewe

Climate and CO2 saturation in an alpine lake throughout the Holocene

This study shows that diatom sediment records can be used to investigate the long-term inorganic carbon dynamics in oligotrophic and poorly acid-buffered lakes. Using a training set of 115 high-mountain lakes in the Pyrenees, we found that both alkalinity and potential hydrogen (pH) independently explained some of the variability in diatom assemblages. Transfer functions for both variables were developed and applied to a Holocene record from Lake Redon and CO2 changes calculated. CO2 saturation broadly followed alkalinity, which in turn was related to summer and autumn air-temperature fluctuations. In general, warmer climate during the ice-free period led to higher supersaturation, due to increased alkalinity, which facilitated retention of CO2 from respiration, and decreased primary production (assessed by diatom fluxes). Only during the early Holocene, there were periods of extreme undersaturation, corresponding to cold periods of low alkalinity (<20 microequivalents per liter [meq L21]), and suggesting carbon limitation of primary production. The winter and spring climate, which determines the ice cover duration, appears to be relevant for CO2 saturation only during periods when the organic-matter content of the sediments was low (,22%). Longer periods of ice cover led to lower lake CO2 saturation, suggesting that the ice cover influence on internal nutrient loading may regulate lake productivity fluctuations under low allocthonous nutrient and organic-matter inputs. Alkalinity ,20 meq L21 and sediment organic matter ,22% appear as critical thresholds in the way lake CO2 levels respond to climate fluctuations.Peer ReviewedPostprint (published version

Magnetic relaxation measurements of exchange biased (Pt/Co) multilayers with perpendicular anisotropy

Magnetic relaxation measurements were carried out by magneto-optical Kerr effect on exchange biased (Pt/Co)5/Pt/FeMn multilayers with perpendicular anisotropy. In these films the coercivity and the exchange bias field vary with Pt spacer thickness, and have a maximum for 0.2 nm. Hysteresis loops do not reveal important differences between the reversal for ascending and descending fields. Relaxation measurements were fitted using Fatuzzo's model, which assumes that reversal occurs by domain nucleation and domain wall propagation. For 2 nm thick Pt spacer (no exchange bias) the reversal is dominated by domain wall propagation starting from a few nucleation centers. For 0.2 nm Pt spacer (maximum exchange bias) the reversal is strongly dominated by nucleation, and no differences between the behaviour of the ascending and descending branches can be observed. For 0.4 nm Pt spacer (weaker exchange bias) the nucleation density becomes less important, and the measurements reveal a much stronger density of nucleation centers in the descending branch.Comment: Europhysical Journal B, in print DOI: 10.1140/epjb/e2005-00053-

Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/Al_2\_2O_3\_3/Co magnetic tunnel junctions

We have studied the magnetization reversal dynamics of FeNi/Al$\_2$O$\_3$/Co magnetic tunnel junctions deposited on step-bunched Si substrates using magneto-optical Kerr effect and time-resolved x-ray photoelectron emission microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM). Different reversal mechanisms have been found depending on the substrate miscut angle. Larger terraces (smaller miscut angles) lead to a higher nucleation density and stronger domain wall pinning. The width of domain walls with respect to the size of the terraces seems to play an important role in the reversal. We used the element selectivity of XMCD-PEEM to reveal the strong influence of the stray field of domain walls in the hard magnetic layer on the magnetic switching of the soft magnetic layer.Comment: 8 Pages, 7 Figure

Additive manufactured, highly resilient, elastic, and biodegradable poly(ester)urethane scaffolds with chondroinductive properties for cartilage tissue engineering

Articular cartilage was thought to be one of the first tissues to be successfully engineered. Despite the avascular and non-innervated nature of the tissue, the cells within articular cartilage - chondrocytes - account for a complex phenotype that is difficult to be maintained in vitro. The use of bone marrow-derived stromal cells (BMSCs) has emerged as a potential solution to this issue. Differentiation of BMSCs toward stable and non-hypertrophic chondrogenic phenotypes has also proved to be challenging. Moreover, hyaline cartilage presents a set of mechanical properties - relatively high Young's modulus, elasticity, and resilience - that are difficult to reproduce. Here, we report on the use of additive manufactured biodegradable poly(ester)urethane (PEU) scaffolds of two different structures (500 mu m pore size and 90 degrees or 60 degrees deposition angle) that can support the loads applied onto the knee while being highly resilient, with a permanent deformation lower than 1% after 10 compression-relaxation cycles. Moreover, these scaffolds appear to promote BMSC differentiation, as shown by the deposition of glycosaminoglycans and collagens (in particular collagen II). At gene level, BMSCs showed an upregulation of chondrogenic markers, such as collagen II and the Sox trio, to higher or similar levels than that of traditional pellet cultures, with a collagen II/collagen I relative expression of 2-3, depending on the structure of the scaffold. Moreover, scaffolds with different pore architectures influenced the differentiation process and the final BMSC phenotype. These data suggest that additive manufactured PEU scaffolds could be good candidates for cartilage tissue regeneration in combination with microfracture interventions.</p

Dynamics of magnetic domain wall motion after nucleation: Dependence on the wall energy

The dynamics of magnetic domain wall motion in the FeNi layer of a FeNi/Al2O3/Co trilayer has been investigated by a combination of x-ray magnetic circular dichroism, photoelectron emission microscopy, and a stroboscopic pump-probe technique. The nucleation of domains and subsequent expansion by domain wall motion in the FeNi layer during nanosecond-long magnetic field pulses was observed in the viscous regime up to the Walker limit field. We attribute an observed delay of domain expansion to the influence of the domain wall energy that acts against the domain expansion and that plays an important role when domains are small.Comment: Accepted for publication in Physical Review Letter

Developing double-crosslinking 3D printed hydrogels for bone tissue engineering

Bone defects are one of the main causes of disability worldwide. Due to the disadvantages associated with autografts, the latest advances have been focused on tissue regeneration approaches that use injectable hydrogels or 3D printed hydrogel-based structures that could refill appropriately the bone gap area without the need for external fixatives, leading to bone formation in the long term. Injectable hydrogels could be applied in extrusion-based 3D printing as inks; in this sense, double-crosslinking hydrogels appear as ideal candidates. In this work, injectable and printable double crosslinkable hydrogels based on oxidized xanthan gum (XGox) and methacrylate polyaspartylhydrazide (PAHy-MA) were produced. The formation of dynamic hydrazone bonds, occurring between aldehyde groups on the polysaccharide backbone and hydrazine moieties of PAHy-MA, induced an instant gelation, conferring, also, injectability and self-healing properties to the hydrogels. The presence of methacrylic moieties on the synthetic polymer allowed further crosslinking upon UV irradiation that stabilized the hydrogel shape and mitigated its susceptibility to hydrolytic degradation. Obtained hydrogels showed pseudoplastic behaviour and good recovery of viscoelastic properties over time. The physicochemical and rheological characterization highlighted increased stability and higher viscoelastic moduli after photo-crosslinking. The hydrogels also showed good printability, cytocompatibility and the early formation of a bone-like matrix when osteosarcoma-derived cells (MG-63) were cultured in the scaffolds for 21 days, with an increased collagen I deposition, mineralization and the expression of characteristic osteogenic markers