AlInN/GaN on Si high-electron mobility transistors (HEMTs) are irradiated with various fluences of 75-MeV sulfur ions to study the radiation-induced degradation mechanisms. Heavy-ion irradiation has been found to reduce saturation on- and off-state current and, at higher fluence, to induce a large positive threshold voltage shift. Irradiated structures reveal a consistent carrier density and mobility reduction as a function of fluence. To demonstrate the buffer-induced threshold shift, a series of samples with various GaN channel layer thicknesses defined by carbon-doped GaN buffer layers are characterized. By comparison of the threshold voltage of nonirradiated devices with reduced channel layer thickness, we assign the observed effects mainly to carrier depletion. Thus, formation of acceptor-like traps upon irradiation is concluded as primary degradation mechanism in GaN-based HEMTs. AlInN/GaN HEMT structures are, therefore, more tolerant to heavy-ion irradiation than AlGaN/GaN transistors as their intrinsic channel conductivity is higher.

A fossil bird (MLP-PV 15-I-7-52) from Marambio (Seymour) Island, Antarctica, is described, representing the best-preserved skull reported for a Cretaceous neornithine and associated postcranial elements. Morphological analysis of the articular portion of the mandible, the pterygoid, and the femur supports the assignment of this specimen to the genus Vegavis. The palatine morphology exhibits a combination of plesiomorphic and autapomorphic characters within Neognathae. Substantial differences in the size relationship between the ala preacetabularis and the femur, as well as differences between the femora of V. iaai and MLP-PV 15-I-7-52, indicate that the latter represents a new species of Vegavis. In addition, a third species of Vegavis is proposed based on the AMNH FARB 30899 specimen, previously assigned to V. iaai, which exhibits substantial differences with the above-mentioned specimens, particularly in the mandibular morphology.

Testing of single event effects caused by heavy ions in a PLL implemented on a CMOS 90 nm technology is reported in this work. The diagnosis of the circuit vulnerability has been conducted with a heavy ion micro beam line facility at the TANDAR tandem accelerator facility. The accuracy of the positioning system has been evaluated and the radiation dose has been accurately characterized. Single event effects were induced in the circuit and a map of the spatial correlation for the most sensitive blocks has been obtained.

Introducción y objetivos: El mercurio (II) acuoso, Hg2+, es todavía un contaminante peligroso ampliamente distribuido. Las estrategias de fitorremediación son ambientalmente amigables y de bajo costo. Con el fin de optimizar estos procesos, se utilizó Spirodela intermedia, una macrófita acuática autóctona, para remover Hg2+ en agua mineral, en condiciones de laboratorio, estudiando la distribución in vivo de mercurio y otros elementos por mapeo barriendo con una microsonda nuclear.M&M: Las exposiciones (concentraciones de Hg2+ de 1 y 10 mg.L-1) duraron al menos 2 semanas. Los parámetros: tasa de captación, factores de bioconcentración (BCFs) de mercurio en raíces y frondes y factores de translocación (TFs) fueron calculados a partir de cuantificaciones de microPIXE con el acelerador Tandar de Buenos Aires.Resultados: S. intermedia puede ser considerado un hiperacumulador. Los más altos BCFs (> 1000 raíces y > 200 frondes) correspondieron a 1 mg.L-1 a las 96 hs. En todos los casos, se constató que TFs < 1, indicando que no ocurre translocación de Hg2+. Se obtuvieron mapas 2D de alta resolución espacial de la distribución elemental in vivo para las diferentes condiciones. Se observó que la distribución de mercurio en frondes es más heterogénea que en raíces. Fue importante la detección de Hg en clorénquima donde sus efectos son más tóxicos. Se analizó una correlación entre la distribución de mercurio y calcio y la relación con respuestas fisiológicas.Conclusiones: La fitorremediación de Hg2+ con S. intermedia es una alternativa conveniente. Por haberse realizado en agua real, el protocolo es escalable.