https://hdl.handle.net/20.500.12412/2538 2026-07-05T22:12:51Z https://hdl.handle.net/20.500.12412/7330 Single-Atom Catalysts for Low-Temperature Thermocatalytic Ammonia Synthesis Arroyo-Caire, Javier; Abelleira Pereira, José María; Serrano-Ruiz, Juan Carlos Abstract Ammonia is indispensable to the fertilizer and chemical industries, yet its manufacture still relies predominantly on the energy-intensive Haber–Bosch process operated at 400–500 °C and 150–250 bar, with a substantial carbon footprint. Single-atom catalysts (SACs) and sub-nanometric clusters have recently emerged as promising alternatives for thermocatalytic ammonia synthesis under milder conditions because they maximize metal utilization and enable precise control of the active site environment. This review first summarizes how the transition from conventional Fe and Ru nanoparticles to isolated or few-atom sites fundamentally alters the kinetic landscape, favoring associative N2 activation pathways that lower apparent activation energies and alleviate H2 poisoning. We then discuss Ru-based SACs and SAAs supported on zeolites, carbons, ceria, and MXenes, highlighting how strong metal–support and promoter interactions, tandem single-atom/nanoparticle motifs, and alloying strategies tune N2 and H2 binding to deliver high NH3 productivities at 200–400 °C and ≤30 bar. In parallel, we review emerging non-noble systems based on Fe and Co, including high-loading Fe–N4 sites prepared via MOF-derived post-metal-replacement routes and Co single atoms or Co2 clusters on N-doped carbons, which already rival or surpass Ru benchmarks under similar conditions. Collectively, these studies show that tailoring the number of atom metal sites, coordination, and support polarity around isolated metal sites provides a useful tool to mitigate some aspects of volcano and scaling-relation limitations, indicating that SACs could contribute to low-temperature ammonia synthesis when combined with appropriate process design. 2026-04-17T00:00:00Z https://hdl.handle.net/20.500.12412/7329 Diamond-Like Carbons for 3-D-Printed Biomedical Components Endrino, José Luis Diamond-like carbon (DLC) coatings are increasingly explored as a practical route to enhance the surface performance of biomedical implants and tissue engineering scaffolds, particularly when combined with additive manufacturing. Rather than serving only as protective layers, DLC coatings allow for independent tuning of surface properties without modifying the bulk structure, which is especially relevant for complex 3D-printed components. This flexibility is often what makes them attractive for biomedical design. This review is structured around two main application areas: DLC coatings for prosthetic implants and DLC coatings for tissue engineering scaffolds. Within this context, the influence of DLC structure (e.g., sp2/sp3 bonding, hydrogen content, and doping) on mechanical, tribological, and biological behavior is discussed. Particular attention is given to additively manufactured metallic implants and porous scaffolds, where large surface area and internal architectures complicate coating uniformity and adhesion. Reports show that DLC coatings can improve corrosion resistance, reduce wear, and influence biological responses, such as antibacterial activity and cell interactions. Several challenges remain to be solved, especially in achieving uniform coating penetration in porous networks and in ensuring long-term stability under physiological conditions. The combination of additive manufacturing and DLC coatings has been shown to offer the potential to become an enabling technology for next-generation biomedical devices. 2026-04-30T00:00:00Z https://hdl.handle.net/20.500.12412/7321 Electrospray cone-jet mode for weakly viscoelastic liquids Blanco Trejo, Sergio; Herrada, Miguel Ángel; Gañán Calvo, Alfonso Miguel; Montanero, Jose María We study theoretically the influence of viscoelasticity on the steady cone-jet mode of electrospray for small stress relaxation times. For this purpose, we numerically integrate the leaky-dielectric model together with the Oldroyd-B constitutive relationship and calculate both the base flow and linear eigenmodes characterizing its stability as a function of the governing parameters. We describe the effect of the polymeric stresses on both the cone-jet mode and the minimum flow rate stability limit. There are considerable differences between the Newtonian and viscoelastic electrospray realizations even for relatively small stress relaxation times due to the intense extensional deformation suffered by the fluid particles in the cone-jet transition region The axial polymeric stress shrinks the liquid meniscus and stabilizes it by pushing the fluid particle in the cone-to-jet transition region.; Es la versión aceptada del artículo. Se puede consultar la versión final en https://doi.org/10.1103/PhysRevE.100.043114 2019-10-28T00:00:00Z https://hdl.handle.net/20.500.12412/7262 S-Graphicable Algebras and Specific Graph Families Ceballos González, Manuel This paper presents new developments in the relationship between S-graphicable algebras and graphs. Several general algebraic properties of S-graphicable evolution algebras are established, including characterizations of the annihilator, idempotent elements, and evolution subalgebras. It is also shown that S-graphicable algebras are nonsolvable, and several results concerning their perfectness are provided. In addition, new families of S-graphicable algebras are introduced, each associated with well-known graph types, and the structural relationships among these families are analyzed, revealing significant algebraic connections. Finally, an algorithmic method is presented to determine whether a given evolution algebra is S-graphicable and, if so, to construct its associated graph.; Es la versión aceptada del articulo. Se puede consultar la versión final en https://doi.org/10.1002/mma.70534 2026-01-28T00:00:00Z