Aceleración de iones por campos colectivos en descargas eléctricas focalizadas, similitud con los procesos físicos en fulguraciones solares

En experimentos con descargas eléctricas focalizadas en sistemas de electrodos coaxiales, haces de electrones con energías promedio de 300 keV e iones con energías superior al MeV, son generados en pequeños volúmenes de plasma altamente densificados. La observación de esta región antes, durante y después del momento de la máxima compresión, muestran estructuras de corriente ordenadas (filamentos), de rápida evolución. El decaimiento de estos campos en tiempos del orden del nanosegundo, inducen potenciales eléctricos capaces de acelerar a los iones y electrones existentes en el plasma hasta las energías observadas. En el presente trabajo se muestran imágenes de alta resolución espacial y temporal de las descargas, en luz visible, radiación X (E ≥ 1 KeV), y por impresión de láminas de policarbonatos, donde se puede apreciar la estructura filamentosa de la corriente. Se comparan estos resultados con los que se disponen de la observación de ciertas fulguraciones solares.Asociación Argentina de Astronomí

Reactive sputter magnetron reactor for preparation of thin films and simultaneous in-situ structural study by X-ray diffraction.

Reactive Sputter Magnetron (RSM) is a widely used technique to thin films growing\ud of compounds both, in research laboratories and in industrial processes. The nature\ud of the deposited compound will depend then on the nature of the magnetron target\ud and the nature of the ions generated in the plasma. One important aspect of the\ud problem is the knowledge of the evolution of the film during the process of growing\ud itself. In this work, we present the design, construction of a chamber to be installed\ud in the Huber goniometer in the XRD2 line of LNLS in Campinas, which allows in\ud situ growing kinetic studies of thin films.ANPCy

Anomalous Self-Generated Electrostatic Fields in Nanosecond Laser-Plasma Interaction

Electrostatic (E) fields associated with the interaction of a well-controlled, high-power, nanosecond laser pulse with an underdense plasma are diagnosed by proton radiography. Using a current 3D wave propagation code equipped with nonlinear and nonlocal hydrodynamics, we can model the measured E-fields that are driven by the laser ponderomotive force in the region where the laser undergoes filamentation. However, strong fields of up to 110 MV/m measured in the first millimeter of propagation cannot be reproduced in the simulations. This could point to the presence of unexpected strong thermal electron pressure gradients possibly linked to ion acoustic turbulence, thus emphasizing the need for the development of full kinetic collisional simulations in order to properly model laser-plasma interaction in these strongly nonlinear conditions.Comment: 12 pages, 4 figures, submitted to Physics of Plasma

Combined Inactivation of pRB and Hippo Pathways Induces Dedifferentiation in the Drosophila Retina

Functional inactivation of the Retinoblastoma (pRB) pathway is an early and obligatory event in tumorigenesis. The importance of pRB is usually explained by its ability to promote cell cycle exit. Here, we demonstrate that, independently of cell cycle exit control, in cooperation with the Hippo tumor suppressor pathway, pRB functions to maintain the terminally differentiated state. We show that mutations in the Hippo signaling pathway, wts or hpo, trigger widespread dedifferentiation of rbf mutant cells in the Drosophila eye. Initially, rbf wts or rbf hpo double mutant cells are morphologically indistinguishable from their wild-type counterparts as they properly differentiate into photoreceptors, form axonal projections, and express late neuronal markers. However, the double mutant cells cannot maintain their neuronal identity, dedifferentiate, and thus become uncommitted eye specific cells. Surprisingly, this dedifferentiation is fully independent of cell cycle exit defects and occurs even when inappropriate proliferation is fully blocked by a de2f1 mutation. Thus, our results reveal the novel involvement of the pRB pathway during the maintenance of a differentiated state and suggest that terminally differentiated Rb mutant cells are intrinsically prone to dedifferentiation, can be converted to progenitor cells, and thus contribute to cancer advancement