Understanding the reaction mechanism of the oxidative addition of ammonia by (PXP)Ir(i) complexes: the role of the X group.

An analysis of the electronic rearrangements for the oxidative addition of ammonia to a set of five representative (PXP)Ir pincer complexes (X = B, CH, O, N, SiH) is performed. We aim to understand the factors controlling the activation and reaction energies of this process by combining different theoretical strategies based on DFT calculations. Interestingly, complexes featuring higher activation barriers yield more exothermic reactions. The analysis of the reaction path using the bonding evolution theory shows that the main chemical events, N-H bond cleavage and Ir-H bond formation, take place before the transition structure is reached. Metal oxidation implies an electron density transfer from non-shared Ir pairs to the Ir-N bond. This decrement in the atomic charge of the metal provokes different effects in the ionic contribution of the Ir-X bonding depending on the nature of the X atom as shown by the interacting quantum atoms methodology.

Optical nanoantennas with tunable radiation patterns.

We address new optical nanoantenna systems with tunable highly directional radiation patterns. The antenna comprises a regular linear array of metal nanoparticles in the proximity of an interface with high dielectric contrast. We show that the radiation pattern of the system can be controlled by changing parameters of the excitation, such as the polarization and/or incidence angles. In the case of excitation under the total reflection condition, the system operates as a nanoscopic source of radiation, converting the macroscopic incident plane wavefront into a narrow beam of light with adjustable characteristics. We derive also simple analytical formulas which give an excellent description of the radiation pattern and provide a useful tool for analysis and antenna design.

Graphene nanoring as a tunable source of polarized electrons.

We propose a novel spin filter based on a graphene nanoring fabricated above a ferromagnetic strip. The exchange interaction between the magnetic moments of the ions in the ferromagnet and the electron spin splits the electronic states, and gives rise to spin polarization of the conductance and the total electric current. We demonstrate that both the current and its polarization can be controlled by a side-gate voltage. This opens the possibility to use the proposed device as a tunable source of polarized electrons.

Toward graphene-based quantum interference devices.

A new type of quantum interference device based on a graphene nanoring in which all edges are of the same type is studied theoretically. The superposition of the electron wavefunction propagating from the source to the drain along the two arms of the nanoring gives rise to interesting interference effects. We show that a side-gate voltage applied across the ring allows for control of the interference pattern at the drain. The electron current between the two leads can therefore be modulated by the side gate. The latter manifests itself as conductance oscillations as a function of the gate voltage. We study quantum nanorings with two edge types (zigzag or armchair) and argue that the armchair type is more advantageous for applications. We demonstrate finally that our proposed device operates as a quantum interference transistor with high on/off ratio.

Model for hand-over-hand motion of molecular motors.

A simple flashing ratchet model in two dimensions is proposed to simulate the hand-over-hand motion of two head molecular motors such as kinesin. Extensive Langevin simulations of the model are performed. Good qualitative agreement with the expected behavior is observed. We discuss different regimes of motion and efficiency depending on model parameters.

Meningitis por estreptococo agalactie en adulto joven / Meningitis due to estreptococcus agalactiae in young adult

Se ha detectado un incremento de infecciones en adultos por estreptococo del grupo B o agalactie los últimos años. Pueden causar bacteriemias, celulitis, neumonía, endocarditis, artritis y meningitis. Presentamos el caso de una mujer que sufrió una meningitis complicada con distress respiratorio y septicemia cuya evolución,sin embargo, fue favorable con el tratamiento instaurado. Este estreptococo es responsable de menos del 2% de casos de meningitis en adultos, siendo de alto riesgo las embarazadas y los pacientes con enfermedades crónicas como diabetes, cirrosis,cáncer, traumatizados, enfermedades autoinmunes, infectados por VIH o postoperatorios. Su mortalidad oscila del 27 al 34%. Aunque la incidencia es superior en mayores de 60 años con enfermedades crónicas hay un aumento progresivo en pacientes adultos inmunocompetentes, por lo que este agente causal no debe obviarse ante la presentica de meningitis de rápida instauración en un adulto joven

Its detected and increment of group B streptococcus or agalactie adults infection in recent years. Can be responsible of bacteremia, cellulites, pneumonia, endocarditis, arthritis and meningitis. We report a meningitis young female case, with serious complications like a distress respiratory syndrome and sepsis, but good evolution with antibiotics. Group B streptococcus is the responsible than near of 2% adult meningitis, and is associated to pregnancy and underlying conditions like diabetes, cirrhosis, cancer, trauma, inmunologic illness, HIV infection or surgery. The mortality is around 27,34%. The incidence is superior in elderly with debilitating diseases but there is a progressive increment in patients without diseases, so we mustn´t forget this etiology in fast instauration meningitis in a young adult

Reservorios venosos subcutáneos: disección versus punción / Subcutaneous venous indwelling: cutdown versus percutaneous puncture insertion

- Propósito: Los reservorios venosos subcutáneos (RVS) pueden ser implantados por punción o mediante disección. El objetivo de este estudio es comparar ambas técnicas.- Material y métodos: De una serie de 237 RVS (Healthport,, Baxter, Lessines, Belgica), 100 pacientes fueron aleatorizados a colocación por disección (CD) o por punción percutánea (PP). Los datos demográficos, complicaciones y duración del RVS (definida como duración hasta retirada, último control o exitus del paciente) fueron recogidos en un protocolo prospectivo. Las complicaciones en cada grupo fueron comparadas mediante el test de Fisher.- Resultados: El grupo CD constó de 20 hombres y 30 mujeres (16 cánceres de mama, 10 colorrectales, 6 linfomas, 6 cánceres de pulmón, 6 tumores ORL, 2 mielomas, 2 melanomas y 2 tumores ováricos) con una media de edad de 58.6 años (rango 19-83). El grupo PP constó de 23 hombres y 27 mujeres (20 cánceres colorrectales, 13 mamarios, 5 pulmonares, 5 gástricos, 2 melanomas, 2 ORL, 2 ováricos y 1 linfoma) con una media de edad de 58.2 años (rango 43-76). El grupo CD tuvo 4 (8 por ciento) complicaciones (2 oclusiones, 1 trombosis y 1 mal posición). El grupo PP tuvo 1 (2 por ciento) complicación (trombosis). El grupo CD tuvo una media de tiempo de duración del RVS de 214 días mientras que en el grupo PP fue de 201 días. El test de Fisher (complicaciones) resultó con un valor de 0.152, al que corresponde un p>0.05.- Conclusiones: En nuestra experiencia, la colocación de RVS por disección tiene un índice de complicaciones superior a la colocación mediante punción percutánea. Sin embargo, este aumento del índice de complicaciones no alcanza significancia estadística (AU)