Neuroimagen y neurobiología de la adicción:un estudio sobre los cambios funcionales cerebrales en personas adictas a las cocaína

Decenes Jornades de Foment de la Investigació de la FCHS (Any 2004-2005)El consumo crónica de cocaína produce una reducción de la dopamina en ciertas áreas cerebrales, provocando una alteración en este sistema. (Volkow y cols., 1999; Wu y cols., 1997). El objetivo de este trabajo es estudiar mediante Resonancia Magnética Funcional, los efectos que el consumo crónico de cocaína provoca sobre el procesamiento emocional. Los participantes (10 pacientes adictos a la cocaína y 10 personas no adictas) realizaron una tarea de procesamiento emocional en la que visualizaban fotografías con contenido emocional positivo, negativo y neutro (Adaptación española del International Affective Pictures System, IAPS, moltó y cols. 2001) como fondo en un tarea de discriminación de letras. Los resultados muestran una menor activación en el núcleo accumbens, giro cingulado anterior y cortex orbitofrontal en personas adictas a la cocaína en comparación al grupo control, ante la visión de imágenes positivas. Mientras que, se observa una menor activación del giro cingulado anterior en pacientes en comparación a los controles, para la visión de imágenes negativas. Estos resultados sugieren que la tarea del IAPS es una buena tarea para activar áreas específicas de recompensa (N.acc y giro orbitofrontal). Y que los pacientes presentan una disfunción en el sistema de recompensa, lugar donde actúa la cocaína tras su administración, liberando dopamina. Esto podría tener como consecuencia una menor sensibilidad de estas personas para los reforzadores naturales

Dichroism for orbital angular momentum using parametric amplification

We theoretically analyze parametric amplification as a means to produce dichroism based on the orbital angular momentum (OAM) of an incident signal field. The nonlinear interaction is shown to provide differential gain between signal states of differing OAM, the peak gain occurring at half the OAM of the pump field

Self-healing high-dimensional quantum key distribution using hybrid spin-orbit Bessel states

Using spatial modes for quantum key distribution (QKD) has become highly topical due to their infinite dimensionality, promising high information capacity per photon. However, spatial distortions reduce the feasible secret key rates and compromise the security of a quantum channel. In an extreme form such a distortion might be a physical obstacle, impeding line-of-sight for free-space channels. Here, by controlling the radial degree of freedom of a photon's spatial mode, we are able to demonstrate hybrid high-dimensional QKD through obstacles with self-reconstructing single photons. We construct high-dimensional mutually unbiased bases using spin-orbit hybrid states that are radially modulated with a non-diffracting Bessel-Gaussian (BG) profile, and show secure transmission through partially obstructed quantum links. Using a prepare-measure protocol we report higher quantum state self-reconstruction and information retention for the non-diffracting BG modes as compared to Laguerre-Gaussian modes, obtaining a quantum bit error rate (QBER) that is up to 3 times lower. This work highlights the importance of controlling the radial mode of single photons in quantum information processing and communication as well as the advantages of QKD with hybrid states.Comment: Published version, 15 pages, 6 figures, 2 table

The contrasting activity of iodido versus chlorido ruthenium and osmium arene azo- and imino-pyridine anticancer complexes : control of cell selectivity, cross-resistance, p53 dependence, and apoptosis pathway

Organometallic half-sandwich complexes [M(p-cymene)(azo/imino-pyridine)X]+ where M = RuII or OsII and X ═ Cl or I, exhibit potent antiproliferative activity toward a range of cancer cells. Not only are the iodido complexes more potent than the chlorido analogues, but they are not cross-resistant with the clinical platinum drugs cisplatin and oxaliplatin. They are also more selective for cancer cells versus normal cells (fibroblasts) and show high accumulation in cell membranes. They arrest cell growth in G1 phase in contrast to cisplatin (S phase) with a high incidence of late-stage apoptosis. The iodido complexes retain potency in p53 mutant colon cells. All complexes activate caspase 3. In general, antiproliferative activity is greatly enhanced by low levels of the glutathione synthase inhibitor l-buthionine sulfoxime. The work illustrates how subtle changes to the design of low-spin d6 metal complexes can lead to major changes in cellular metabolism and to potent complexes with novel mechanisms of anticancer activity

CO Oxidation Catalysed by Pd-based Bimetallic Nanoalloys

Density functional theory based global geometry optimization has been used to demonstrate the crucial influence of the geometry of the catalytic cluster on the energy barriers for the CO oxidation reaction over Pd-based bimetallic nanoalloys. We show that dramatic geometry change between the reaction intermediates can lead to very high energy barriers and thus be prohibitive for the whole process. This introduces challenges for both the design of new catalysts, and theoretical methods employed. On the theory side, a careful choice of geometric configurations of all reaction intermediates is crucial for an adequate description of a possible reaction path. From the point of view of the catalyst design, the cluster geometry can be controlled by adjusting the level of interaction between the cluster and the dopant metal, as well as between the adsorbate molecules and the catalyst cluster by mixing different metals in a single nanoalloy particle. We show that substitution of a Pd atom in the Pd$_{5}$ cluster with a single Ag atom to form Pd$_{4}$Ag$_{1}$ leads to a potential improvement of the catalytic properties of the cluster for the CO oxidation reaction. On the other hand, a single Au atom does not enhance the properties of the catalyst, which is attributed to a weaker hybridization between the cluster's constituent metals and the adsorbate molecules. Such flexibility of properties of bimetallic nanoalloy clusters illustrates the possibility of fine-tuning, which might be used for design of novel efficient catalytic materials.Comment: 12 pages, 8 figure