Física Aplicada
http://hdl.handle.net/10347/2919
2024-03-29T07:09:09ZVisual performance of new affordable and auto‐adherent lenses for presbyopia correction
http://hdl.handle.net/10347/33248
Visual performance of new affordable and auto‐adherent lenses for presbyopia correction
García Porta, Nery; Gómez Varela, Ana Isabel; Arines Piferrer, Justo
Presbyopia is a visual condition that affects all of us, evolving with time, reducing the range of accommodation and the ability to work at near. Reading glasses, bifocals or multifocal lenses are the most common solutions. In this work, we demonstrate the near visual performance of new elastomeric auto-adherent lenses developed for the correction of presbyopia. Visual acuity and contrast sensitivity were measured in 10 presbyopic subjects. The results showed that wearing either conventional trial ophthalmic lenses or the new elastomeric lenses provided similar visual quality. These elastomeric lenses can be placed in, or removed from the distance-vision spectacles of the wearers, providing an affordable solution for correcting presbyopia at its clinical onset, which might be especially useful in subjects with different refractive error in each eye and for those with astigmatism
2023-01-01T00:00:00ZTemperature and Thickness Dependence of the Thermal Conductivity in 2D Ferromagnet Fe3GeTe2
http://hdl.handle.net/10347/33247
Temperature and Thickness Dependence of the Thermal Conductivity in 2D Ferromagnet Fe3GeTe2
Santos Claro, Marcel; Corral Sertal, Javier; Otero Fumega, Adolfo; Blanco Canosa, Santiago; Suárez Rodríguez, Manuel; Hueso Arroyo, Luis E.; Pardo Castro, Víctor; Rivadulla Fernández, José Francisco
The emergence of symmetry-breaking orders such as ferromagnetism and the weak interlayer bonding in van der Waals materials offers a unique platform to engineer novel heterostructures and tune transport properties like thermal conductivity. Here, we report the experimental and theoretical study of the cross-plane thermal conductivity, κ⊥, of the van der Waals two-dimensional (2D) ferromagnet Fe3GeTe2. We observe an increase in κ⊥ with thickness, indicating a diffusive transport regime with ballistic contributions. These results are supported by the theoretical analyses of the accumulated thermal conductivity, which show an important contribution of phonons with mean free paths between 10 and 200 nm. Moreover, our experiments show a reduction of κ⊥ in the low-temperature ferromagnetic phase occurring at the magnetic transition. The calculations show that this reduction in κ⊥ is associated with a decrease in the group velocities of the acoustic phonons and an increase in the phonon–phonon scattering of the Raman modes that couple to the magnetic phase. These results demonstrate the potential of van der Waals ferromagnets for thermal transport engineering
2023-01-01T00:00:00ZSynthesizing small-sized monodisperse molybdenum nanoparticles as potential precursors for medical radioisotopes
http://hdl.handle.net/10347/33241
Synthesizing small-sized monodisperse molybdenum nanoparticles as potential precursors for medical radioisotopes
Arnosa Prieto, Ángela; González Gómez, Manuel Antonio; García Acevedo, Pelayo; Castro Alves, Lisandra de; Piñeiro Redondo, Yolanda; Rivas Rey, José
Molybdenum-99 (99Mo) is used to produce technetium-99 m (99mTc), one of the most used medical radioisotopes in the world. 99Mo is currently created by fission of uranium-235 (235U) in a small number of research nuclear fission reactors. Several problems related to the use of 235U as primary source is causing a global 99Mo generation crisis. Therefore, we are facing the need of finding new viable and safe production alternatives. Neutron activation of molybdenum is a promising candidate in which the ideal target for 99Mo production are small monodisperse molybdenum nanoparticles (Mo NPs). However, the reported procedures for the obtention of Mo NPs present either the lack of simplicity of the employed synthetic methods or the inappropriate size and monodispersity of the synthesized Mo NPs. Here, we report a simple synthetic procedure for the obtention of small-sized monodisperse metallic Mo NPs. In the studied conditions, thermal decomposition of Mo(CO)6 produced oleylamine coated Mo NPs. The oleylamine layer was included with the purpose of avoiding oxidation. Although an oxide patina was still formed on the surface of the Mo NPs, the core remains in a metallic phase after several weeks from its production, as it was confirmed by X-ray photoelectron spectroscopy analysis (XPS). The described synthetic procedure provides a simple method for the obtention of Mo NPs with optimum characteristics as non-fission method for 99Mo production
2024-01-01T00:00:00ZPredicting the energy properties of torrefied debarked pine pellets from torrefaction temperature and residence time
http://hdl.handle.net/10347/33193
Predicting the energy properties of torrefied debarked pine pellets from torrefaction temperature and residence time
Iglesias Canabal, Andrés; Proupín Castiñeiras, Jorge; Rodríguez Añón, José Antonio; Eimil Fraga, Cristina; Rodríguez Soalleiro, Roque
In this study, high quality radiata pine pellets were torrefied at a range of temperatures (T = 210, 240, 270 and 300 °C) and residence times (t = 20, 40 and 60 min). The effects of these treatments on mass yield (MY), ash content (A), volatile matter (VM) and fixed carbon (FC), high heating value on a dry basis (HHVdb) and low heating value on a wet basis (LHVwb) were investigated, and models were constructed to predict these energy properties from T and t. Untreated pellets were analysed as control samples. Threshold conditions of 240 °C 40 min yielded significant increases in HHVdb and carbon content and a significant decrease in oxygen content. This combination significantly increased A and FC and significantly decreased VM. Logistics models using T, t, t × T and T2 were able to predict A accurately, with no bias, whereas FC values tended to be underestimated. The variation in HHVdb and LHVwb was explained by linear models with t and t × T as variables. Use of the models enabled definition of torrefaction severity that ensures an A below 0.7% and a LHVwb value 30% higher than obtained with raw pine pellets. Torrefaction conditions of T = 260–270 °C and t = 50–60 min are proposed
2023-01-01T00:00:00Z