Three-dimensional numerical simulation of 1GeV/Nucleon U92+ impact against atomic hydrogen

The impact of 1GeV/Nucleon U92+ projectiles against atomic hydrogen is studied by direct numerical resolution of the time-dependent wave equation for the atomic electron on a three-dimensional Cartesian lattice. We employ the fully relativistic expressions to describe the electromagnetic fields created by the incident ion. The wave equation for the atom interacting with the projectile is carefully derived from the time-dependent Dirac equation in order to retain all the relevant terms.Comment: 12 pages and 7 figures included in the tex

Regulation of Ace2-dependent genes requires components of the PBF complex in schizosaccharomyces pombe

The division cycle of unicellular yeasts is completed with the activation of a cell separation program that results in the dissolution of the septum assembled during cytokinesis between the 2 daughter cells, allowing them to become independent entities. Expression of the eng1+ and agn1+ genes, encoding the hydrolytic enzymes responsible for septum degradation, is activated at the end of each cell cycle by the transcription factor Ace2. Periodic ace2+ expression is regulated by the transcriptional complex PBF (PCB Binding Factor), composed of the forkhead-like proteins Sep1 and Fkh2 and the MADS box-like protein Mbx1. In this report, we show that Ace2-dependent genes contain several combinations of motifs for Ace2 and PBF binding in their promoters. Thus, Ace2, Fkh2 and Sep1 were found to bind in vivo to the eng1+ promoter. Ace2 binding was coincident with maximum level of eng1+ expression, whereas Fkh2 binding was maximal when mRNA levels were low, supporting the notion that they play opposing roles. In addition, we found that the expression of eng1+ and agn1+ was differentially affected by mutations in PBF components. Interestingly, agn1+ was a major target of Mbx1, since its ectopic expression resulted in the suppression of Mbx1 deletion phenotypes. Our results reveal a complex regulation system through which the transcription factors Ace2, Fkh2, Sep1 and Mbx1 in combination control the expression of the genes involved in separation at the end of the cell division cycle

Breakdown of stabilization of atoms interacting with intense, high-frequency laser pulses

Published versio

Efecto alelopático de especies invasoras de ribera sobre la germinación de especies del sotobosque

9 páginas. -- Trabajo presentado en la 50ª Reunión Científica de la SEEPLa producción de sustancias alelopáticas por las especies vegetales contribuye a incrementar su éxito competitivo frente a otras especies coexistentes dentro de un mismo hábitat, pudiendo llegar incluso a eliminarlas. Las sustancias alelopáticas pueden inhibir la germinación y el crecimiento de otras especies de la comunidad. En los bosques de ribera se ha detectado la presencia de árboles exóticos con potencial invasor en otros ecosistemas pero se desconoce su efecto sobre las especies autóctonas herbáceas. Nuestra hipótesis es que las especies invasoras podrían utilizar la producción de aleloquímicos de una manera eficiente para desplazar a las especies herbáceas autóctonas, pudiendo llegar a eliminarlas. El objetivo del presente trabajo fue estudiar el efecto extractos de hojarasca de especies alóctonas arbóreas (Ulmus pumila, Robinia pseudoacacia, Ailanthus altissima) y autóctonas (Populus alba) sobre la germinación de cuatro especies herbáceas frecuentes en el sotobosque del bosque de ribera del rio Henares (Madrid). Los resultados mostraron una disminución de la velocidad de germinación de B. phoenicoides y B. sylvaticum con los extractos de las especies alóctonas y autóctonas excepto para el olmo siberiano. Chenopodium album no se vio perjudicada por los extractos de las especies alóctonas pero sí por lo de la especie autóctona. La velocidad de germinación de Dactylis glomerata fue afectada por los extractos de todas las especies alóctonas. Se concluye que no existe un efecto consistente de los extractos de las hojas de árboles exóticos sobre las herbáceas nativas, sino que éstos dependen tanto de la naturaleza del árbol donante como de la herbácea receptora.Plants produce allelopathic substances increasing their competitive success over other species coexisting within the same habitat, being able to eliminate them. Allelopathic substances inhibit germination and growth of other species in the community. In the riverside forests, it has been detected, the presence of invasive tree species with demonstrated invasive potential in other ecosystems. Our hypothesis is that invasive species could use the production of allelochemicals in an efficient way to compete against native herbaceous species. The aim of this work was to assess the effects of leaf extracts of invasive species (Ulmus pumila, Robinia pseudoacacia, Ailanthus altissima) and native (Populus alba) on the germination of four grass species frequent in the forest understory bank of the river Henares (Madrid). The results showed that extracts of alien and native species (except Siberian elm) decreased the germination speed of B. phoenicoides and B. sylvaticum. The effect of extracts in Chenopodium album was not clear. The extracts of all alien species affected the germination speed of Dactylis glomerata.Agradecemos la ayuda de la Dra. Teodora Martínez en la localización de las zonas de campo. Este trabajo ha sido financiado por los proyectos POII10-0179-4700 de la Junta de Castilla La Mancha y CGL2010-16388/BOS del Ministerio de Ciencia e Innovación.Peer reviewe

Transferring orbital and spin angular momenta of light to atoms

Light beams carrying orbital angular momentum, such as Laguerre-Gaussian beams, give rise to the violation of the standard dipolar selection rules during the interaction with matter yielding, in general, an exchange of angular momentum larger than hbar per absorbed photon. By means of ab initio 3D numerical simulations, we investigate in detail the interaction of a hydrogen atom with intense Gaussian and Laguerre-Gaussian light pulses. We analyze the dependence of the angular momentum exchange with the polarization, the orbital angular momentum, and the carrier-envelope phase of light, as well as with the relative position between the atom and the light vortex. In addition, a quantum-trajectory approach based on the de Broglie-Bohm formulation of quantum mechanics is used to gain physical insight into the absorption of angular momentum by the hydrogen atom

Femtosecond infrared intrastromal ablation and backscattering-mode adaptive-optics multiphoton microscopy in chicken corneas

The performance of femtosecond (fs) laser intrastromal ablation was evaluated with backscattering-mode adaptive-optics multiphoton microscopy in ex vivo chicken corneas. The pulse energy of the fs source used for ablation was set to generate two different ablation patterns within the corneal stroma at a certain depth. Intrastromal patterns were imaged with a custom adaptive-optics multiphoton microscope to determine the accuracy of the procedure and verify the outcomes. This study demonstrates the potential of using fs pulses as surgical and monitoring techniques to systematically investigate intratissue ablation. Further refinement of the experimental system by combining both functions into a single fs laser system would be the basis to establish new techniques capable of monitoring corneal surgery without labeling in real-time. Since the backscattering configuration has also been optimized, future in vivo implementations would also be of interest in clinical environments involving corneal ablation procedures

Atoms interacting with intense, high-frequency laser pulses: Effect of the magnetic-field component on atomic stabilization

Published versio

Spin and magnetization effects in plasmas

We give a short review of a number of different models for treating magnetization effects in plasmas. In particular, the transition between kinetic models and fluid models is discussed. We also give examples of applications of such theories. Some future aspects are discussed.Comment: 18 pages, 1 figure. To appear in Plasma Physics and Controlled Fusion, Special Issue for the 37th ICPP, Santiago, Chil