ALBERT

Description: La Antártica se ha constituido en una región de gran interés científico debido a las condiciones extremas que allí se presentan, en especial, de temperatura y radiación ultravioleta. En el campo de la microbiología, las investigaciones se han enfocado, principalmente, en el estudio de la biodiversidad bacteriana, lo que ha llevado a la descripción de nuevas especies, y también gran interés ha despertado la producción de compuestos con aplicaciones biotecnológicas. Entre éstos se encuentran los que pudieran presentar actividad antibacteriana, de gran importancia debido a que uno de los mayores problemas de los últimos años es la emergencia de patógenos intrahospitalarios con una amplia resistencia a los agentes antibacterianos disponibles, no existiendo alternativas terapéuticas para algunos de ellos. Resulta, por lo tanto, relevante la búsqueda de moléculas que pudieran ser desarrolladas como potenciales drogas antibacterianas.

Description: Published

Description: La Antártica se ha constituido en una región de gran interés científico debido a las condiciones extremas que allí se presentan, en especial, de temperatura y radiación ultravioleta. En el campo de la microbiología, las investigaciones se han enfocado, principalmente, en el estudio de la biodiversidad bacteriana, lo que ha llevado a la descripción de nuevas especies, y también gran interés ha despertado la producción de compuestos con aplicaciones biotecnológicas. Entre éstos se encuentran los que pudieran presentar actividad antibacteriana, de gran importancia debido a que uno de los mayores problemas de los últimos años es la emergencia de patógenos intrahospitalarios con una amplia resistencia a los agentes antibacterianos disponibles, no existiendo alternativas terapéuticas para algunos de ellos. Resulta, por lo tanto, relevante la búsqueda de moléculas que pudieran ser desarrolladas como potenciales drogas antibacterianas.

Description: Published

Description: Trees modify the physico-chemical and biological properties of the soil underneath. Here we present results for seven tree species planted at a site that was contaminated by a mine spill – after which soil was cleaned up and remediated – and later was afforested. We studied the chemical composition (24 elements) in five ecosystem compartments (leaves, forest floor, roots, topsoil and deep soil). The variation in chemical concentration was highest at the level of canopy leaves and lowest at deep soil. The identity of tree species significantly affected the composition of all elements in the canopies but none in the deep soil underneath. Although the observed tree effects on topsoil chemistry were weak, the footprint is expected to be reinforced with age of the plantation, contributing to the phytostabilization of contaminating elements and to the carbon sequestration.

Description: Propagation of large-amplitude waves in plasmas is subject to several sources of nonlinearity due to relativistic effects, either when particle quiver velocities in the wave field are large, or when thermal velocities are large due to relativistic temperatures. Wave propagation in these conditions has been studied for decades, due to its interest in several contexts such as pulsar emission models, laser-plasma interaction, and extragalactic jets. For large-amplitude circularly polarized waves propagating along a constant magnetic field, an exact solution of the fluid equations can be found for relativistic temperatures. Relativistic thermal effects produce: (a) a decrease in the effective plasma frequency (thus, waves in the electromagnetic branch can propagate for lower frequencies than in the cold case); and (b) a decrease in the upper frequency cutoff for the Alfvén branch (thus, Alfvén waves are confined to a frequency range that is narrower than in the cold case). It is also found that the Alfvén speed decreases with temperature, being zero for infinite temperature. We have also studied the same system, but based on the relativistic Vlasov equation, to include thermal effects along the direction of propagation. It turns out that kinetic and fluid results are qualitatively consistent, with several quantitative differences. Regarding the electromagnetic branch, the effective plasma frequency is always larger in the kinetic model. Thus, kinetic effects reduce the transparency of the plasma. As to the Alfvén branch, there is a critical, nonzero value of the temperature at which the Alfvén speed is zero. For temperatures above this critical value, the Alfvén branch is suppressed; however, if the background magnetic field increases, then Alfvén waves can propagate for larger temperatures. There are at least two ways in which the above results can be improved. First, nonlinear decays of the electromagnetic wave have been neglected; second, the kinetic treatment considers thermal effects only along the direction of propagation. We have approached the first subject by studying the parametric decays of the exact wave solution found in the context of fluid theory. The dispersion relation of the decays has been solved, showing several resonant and nonresonant instabilities whose dependence on the wave amplitude and plasma temperature has been studied systematically. Regarding the second subject, we are currently performing numerical 1-D particle in cell simulations, a work that is still in progress, although preliminary results are consistent with the analytical ones.