Otoño 1999

Since the discovery of the magnetic properties of the Prussian Blue, a number of structurally analogous hexacyanometallate derivatives have been isolated and characterized. In the last years, the origin of the magnetic interaction between A and B, as well as its relationship with the stoichiometry and with the nature of the metal ions or their oxidation have been deeply investigated. After a brief review on the electronic origin of the magnetic coupling in these systems, we will discuss on the advantages and disadvantages of electrochemical thin film deposition of two interesting samples of the Prussian Blues analogues.

The calculation of the reactive properties of chemical systems is a key step of the modelling of several modern technologies. These calculations are, in general, based upon the integration of the stationary Schrodinger equation for the motion of the atomic nuclei under the effect of the potential generated by the motion of the electrons. Related numerical procedures are highly demanding in terms of computer time and memory space.

In my talk, I will describe an exact 3D time independent quantum parallel code based on the APH coordinates dormalism used to investigate in detail the dynamical properties of an atom diatom scattering event.

Galactose Oxidase (GO) is a copper containing enzyme that catalyzes the two electron oxidation of a variety of primary alcohols to their corresponding aldehydes, coupled with the reduction of dioxygen to hydrogen peroxide. The enzyme contains one-electron redox centers: a mononuclear copper center and a ligating tyrosyl radical (Tyr272) that is covalently cross-linked, at the ortho position to the OH, to a cysteine residue (Cys228).

In the seminar, density functional calculations examining the mechanism of Galactose Oxidase will be presented. Also recent IMOMM calculations will be discussed.

Complejos carbeno-rutenio del tipo [RuCl2 (=CHR) (PR'3)2] son catalizadores muy eficaces para la metátesis de olefinas. Debido a su gran estabilidad y tolerancia a una amplia gama de grupos funcionales se aplican con frecuencia en la síntesis orgánica. Sin embargo, los precursores de carbenos, como los diazoalcanos, son muy difíciles de obtener y de tratar. Recientemente se ha desarrollado una síntesis que no necesita precursores de carbenos: [{RuCl2 (C8H12)}n] reacciona con H2, PiPr3 y acetileno para dar [RuCl2 (=CHR) (PiPr3)2]. Como producto intermedio de la reacción se puede aislar [RuH2Cl2 (PiPr3)2].
Se ha encontrado que, después de ser aislado de la mezcla de reacción, [RuH2Cl2 (PiPr3)2] reacciona con acetileno para formar principalmente el complejo de vinilideno [RuCl2 (=C=CHR) (PiPr3)2]. No obstante el complejo de carbeno se forma como producto secundario.

Se ha propuesto que la formación del carbeno procede vía la adición de HCl al vinilideno. Sin embargo se ha encontrado que en ausencia de ácido se forma la misma cantidad de carbeno. Hemos realizado un estudio teórico a nivel DFT de diferentes mecanismos de reacción para la formación de un complejo carbeno-rutenio a partir de [RuH2Cl2 (PiPr3)2].

We present dynamic user-level page migration, a runtime technique that transparently enables parallel programs to self-tune their memory performance monitoring via feedback obtained through runtime performance monitoring on distributed shared memory multiprocessors. Runtime onformation from page reference counters is used to trigger page migrations, towards reducing the latency of remote memory accesses. Our technique exploits information available to the program both at compile time and at runtime in order to improve the accuracy and the timeliness of page migrations, as well as to amortize better the cost of page migrations, compared to a page migration engine implemented in the operating system.
We present a competitive and a predictive algorithm for dynamic user-level page migration. These algorithms work in synergy to improve the responsiveness of the program to external events that may necessitate page migrations, such as preemptions and migrations of threads. We also present a new technique for preventing page ping-pongs and a page forwarding mechanism for tuning applications with phase changes. Our experimental evidence on a SGI Origin2000, shows that unmodified OpenMP codes linked with our runtime system for dynamic page migration are effectively immune to the initial memory placement of the operating system. This result suggests that it might not be necessary to compromise the simplicity of the OpenMP shared-memory programming standard with data placement directives. Furthermore, our runtime system achieves solid performance improvements compared to the IRIX 6.5.5 page migration engine, for single parallel OpenMP codes and multiprogrammed workloads.

The magnetic properties of the tittle systems have been analyzed using a classical spin Monte Carloapproach. This method has been applied for discrete systems as well as for simple regular and alternated networks, and the results compared when possible to those obtained using exact or approximate expressions. The same approach has been employed for the study of the magnetic behavior of several experimental known systems.

El receptor nicotínico acetilcolinérgico (nAChR) se encuentra implicado en un gran número de enfermedades neurodegenerativas de gran importancia como las alteraciones cognitivas y las enfermedades de Alzheimer y Parkinson por citar alguna.
El estudio del centro activo (lugar de unión con el ligando), es decir, el conocimiento del tipo de interacciones presentes, es un punto fundamental para diseñar nuevos compuestos con el perfil terapéutico adecuado.
A través de estudios de Mecánica y Dinámica Molecular hemos construido lo que se denomina un minireceptor: un conjunto de amino ácidos no unidos entre sí que forman el centro activo.
Para caracterizar correctamente las interacciones anteriores, es necesario recurrir a métodos de la Química Cuántica, y en particular a métodos híbridos QM/MM tales como IMOMM.
El protocolo computacional que hemos desarrollado para abordar el estudio consiste en calcular de forma QM los átomos implicados directamente en cada interacción, mientras que el resto del sistema se tratará de forma MM, actuando como el entorno de la interacción. La idea por tanto, trata de cuantificar las interacciones existentes entre el ligando y los distintos amino ácidos que forman el centro activo en primer lugar, y tratar de buscar la correlación de dichos datos de interacción con la actividad biológica de los ligandos.