Docta Complutense
Open Access Institutional Repository of the Complutense University of Madrid, that compiles scientific production to promote the visibility and impact of Complutense research.
With the collaboration of the Ministerio de Ciencia e Innovación and the Spanish Foundation for Science and Technology (FECYT).
Recent Submissions
Atomistic mechanisms triggered by Joule heating effects in metallic Cu-Bi nanowires for spintronics
(Advanced Materials, 2025) Guedeja-Marrón Gil, Alejandra; Beltrán Fínez, Juan Ignacio; Saura Múzquiz, Matilde; Perna, Paolo; Muñoz de Pablo, Maria del Carmen; Pérez García, Lucas; Varela Del Arco, María
Joule heating may severely impact the response to electric current injection of nanomaterials for spintronics. Here, the effects of heating in Bi doped Cu nanowires, a system where 1% Bi doping promotes a giant spin Hall effect (SHE), are studied by in situ high resolution electron microscopy. High quality Bi-Cu nanowires are grown by room temperature electrodeposition. The large size of Bi cations precludes insertion into the dense Cu face-centered lattice. Still, homogeneous compositions up to a nominal 7% Bi are successfully obtained with thicknesses <100 nm and grain sizes in the micron longitudinal scale, coated by a native oxide. In situ injection of current promotes fast Bi segregation out of solution. Controlled in situ annealing shows that the onset for segregation starts above temperatures of 250 °C. Within minutes, Bi atoms diffuse to grain boundaries or to exposed surfaces, such as the nanowire tips. Monoatomic thick Bi ordered decorations appear, preferentially on surface planes of the (Formula presented.) type. Annealing at 400 °C promotes the growth of pure Bi nanocrystals, coherent with the underlying Cu matrix. Still, the intra-grain Bi concentration remains finite at values near 1%. Density-functional theory calculations show that small amounts of Bi atoms are stable as substitutional impurities, confirming the potential of this system as building block for future spintronic devices.
Reduced growth sensitivity to water availability as potential indicator of drought-induced tree mortality in Mediterranean Pinus sylvestris forests
(Frontiers in Forests and Global Change, 2023) Herrero, Asier; González Gascueña, Raquel; González Díaz, Patricia; Ruiz Benito, Paloma; Andivia Muñoz, Enrique
Introduction: Drought-associated tree mortality has been increasing worldwide since the last decades, impacting structure and functioning of forest ecosystems, with implications for energy, carbon and water fluxes. However, the understanding of the individual vulnerability to drought-induced mortality is still limited.
Methods: We aimed to identify the factors that triggered the mortality of the widely distributed Pinus sylvestris L. in an extensive forest area in central Spain. We compared radial growth patterns in pairs of alive and recently dead individuals that co-occur in close proximity and present similar age and size, thereby isolating the effects of size and environment from the mortality process. Temporal dynamics of growth, growth synchrony, and growth sensitivity to water availability (precipitation minus potential evapotranspiration) were compared between alive and recently dead trees.
Results and discussion: Over the last 50 years, although we did not detect significant differences in growth between alive and dead trees, an increase in the growth synchrony and sensitivity to water availability (i.e. slope of the climatic water balance in the growth model) was observed in all trees as drought intensity increased. 20 years before mortality, dead individuals showed lower growth synchrony and growth sensitivity to water availability than alive ones, without significant differences in growth. Recorded reduction in growth synchrony and growth sensitivity to water availability in dead trees suggests a decoupling between tree growth and climate, which could increase the risk of hydraulic failure and/or carbon starvation under increasingly arid conditions. Thus, the use of reduced growth sensitivity to water availability as potential early-warning signal of tree mortality, together with reduced growth synchrony, should be further explored, particularly in pine species in seasonally dry areas.
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