Phase structure and thermal evolution in coating films and powders obtained by sol-gel process : Part II. ZrO2–2.5 mole% Y2O3

Powders and coatings of zirconia doped with 2.5 mole % yttria have been produced via the sol-gel route. The phase structure and subsequent thermal evolution in heating and cooling cycles have been investigated using mainly perturbed angular correlations spectroscopy. Thermal analyses and XRD as a function of temperature have also been performed to obtain complementary information. Upon heating, the amorphous gels crystallized into the tetragonal structure and showed the same hyperfine pattern and thermal behavior as observed in tetragonal zirconia obtained by the ceramic route: the two configurations of vacancies around zirconium ions denoted as t1 and t2 forms and their mutual t1 → t2 transformation. While the powder sample exhibited an incipient thermal instability above 1000 °C and underwent completely the t2 form to m–ZrO2 transition during subsequent, gradual cooling below 500 °C, the coating retained the tetragonal phase within the whole temperature range investigated. Hyperfine results suggest that the tetragonal phase stabilization is favored by the highly defective nature of the t1 form and consequently hardened by the availability of oxygen. The PAC derived activation energy for the fast diffusion of the oxygen vacancies inherent to the t2 form was determined as 0.54 ± 0.14 eV.Facultad de Ciencias Exacta

Recent collisional history of (65803) Didymos

The Double Asteroid Redirection Test (DART, NASA) spacecraft revealed that the primary of the (65803) Didymos near-Earth asteroid (NEA) binary system is not exactly the expected spinning top shape observed for other km-size asteroids. Ground based radar observations predicted that such shape was compatible with the uncertainty along the direction of the asteroid spin axis. Indeed, Didymos shows crater and landslide features, and evidence for boulder motion at low equatorial latitudes. Altogether, the primary seems to have undergone sudden structural failure in its recent history, which may even result in the formation of the secondary. The high eccentricity of Didymos sets its aphelion distance inside the inner main belt, where it spends more than 1/3 of its orbital period and it may undergo many more collisions than in the NEA region. In this work, we investigate the collisional environment of this asteroid and estimate the probability of collision with multi-size potential impactors. We analyze the possibility that such impacts produced the surface features observed on Didymos by comparing collisional intervals with estimated times for surface destabilization by the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect. We find that collisional effects dominate over potential local or global deformation due to YORP spin up.Project (PGC 2021) PID2021-125883NB-C21, by MICINN (Spanish Government): A.C.B., L.M.P., P.G.B. Call 2023 of the Italian National Institute for Astrophysics (INAF, act n. 38/2023): A.D.O. ESA funding through the Science Faculty—Funding reference ESA-SCI-SC-LE-191: P.G.B. “Margarita Salas” postdoctoral grant by the Spanish Ministry of University—NextGenerationEU: L.M.P. CIAPOS/2022/066 postdoctoral grant (European Social Fund. Generalitat Valenciana): L.M.P. Italian Space Agency (ASI) funding within the LICIACube project (ASI-INAF agreement n. 2019-31-HH.0): A.L., M.P. HERA project (ASI-INAF agreement n. 2022-8-HH.0): A.L., M.P

Phase structure and thermal evolution in coating films and powders obtained by sol-gel process : Part II. ZrO2–2.5 mole% Y2O3

Powders and coatings of zirconia doped with 2.5 mole % yttria have been produced via the sol-gel route. The phase structure and subsequent thermal evolution in heating and cooling cycles have been investigated using mainly perturbed angular correlations spectroscopy. Thermal analyses and XRD as a function of temperature have also been performed to obtain complementary information. Upon heating, the amorphous gels crystallized into the tetragonal structure and showed the same hyperfine pattern and thermal behavior as observed in tetragonal zirconia obtained by the ceramic route: the two configurations of vacancies around zirconium ions denoted as t1 and t2 forms and their mutual t1 → t2 transformation. While the powder sample exhibited an incipient thermal instability above 1000 °C and underwent completely the t2 form to m–ZrO2 transition during subsequent, gradual cooling below 500 °C, the coating retained the tetragonal phase within the whole temperature range investigated. Hyperfine results suggest that the tetragonal phase stabilization is favored by the highly defective nature of the t1 form and consequently hardened by the availability of oxygen. The PAC derived activation energy for the fast diffusion of the oxygen vacancies inherent to the t2 form was determined as 0.54 ± 0.14 eV.Facultad de Ciencias Exacta

La venganza de los huérfanos : las elecciones nacionales y subnacionales de 2015 en Argentina

El triunfo de Mauricio Macri en las elecciones presidenciales de 2015, junto con otros triunfos de la alianza Cambiemos (más o menos sorpresivos o esperables) en arenas provinciales y municipales, significó un punto de quiebre en una evolución política que había iniciado en diciembre de 2001, cuando Fernando de la Rúa se vio obligado a renunciar anticipadamente en un contexto de crisis política, económica y social. Si bien durante la campaña electoral puso en escena una retórica y una estética de cambio, las primeras medidas implementadas por el gobierno demostraron su interés por desmontar las políticas previas, antes que por definir rumbos innovadores. La sospecha de que asistimos a un reflujo parece permear el imaginario político, tanto en el oficialismo como en la oposición. La alusión metafórica de que las elecciones (nacionales) de 2015 significaron un flujo inverso al del mentado aluvión zoológico, o de que asistimos a la recuperación de la casa tomada, nos pareció pertinente para dotar de un sentido general al presente volumen. Los huérfanos de la política de partidos lograron imponerse luego de más de una década donde la retórica plebeya convocaba a mayorías ciudadanas. El presente volumen es el resultado de un proyecto radicado en el Centro de Estudios en Ciudadanía, Estado y Asuntos Políticos (CEAP) de la Facultad de Ciencias Sociales (UBA). El proyecto, denominado Observatorio de Procesos Electorales reunió a estudiantes avanzados y graduados recientes de las carreras de Ciencia Política y Sociología, con una premisa: describir la conformación de los escenarios electorales provinciales y nacionales en 2015