Rayleigh scattering and atomic dynamics in dissipative optical lattices

We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals [S. Guibal et al., Phys. Rev. Lett. 78, 4709 (1997); C. Jurczak et al., Phys. Rev. Lett. 77, 1727 (1996)], we study whether the Rayleigh resonance originates from the diffraction on a density grating and is therefore a probe of transport of atoms in optical lattices. It turns out that this is not the case: the Rayleigh line is instead a measure of the cooling rate, while spatial diffusion contributes to the scattering spectrum with a much broader resonance

Stochastic resonance in periodic potentials: realization in a dissipative optical lattice

We have observed the phenomenon of stochastic resonance on the Brillouin propagation modes of a dissipative optical lattice. Such a mode has been excited by applying a moving potential modulation with phase velocity equal to the velocity of the mode. Its amplitude has been characterized by the center-of-mass (CM) velocity of the atomic cloud. At Brillouin resonance, we studied the CM-velocity as a function of the optical pumping rate at a given depth of the potential wells. We have observed a resonant dependence of the CM velocity on the optical pumping rate, corresponding to the noise strength. This corresponds to the experimental observation of stochastic resonance in a periodic potential in the low-damping regime

Phase-control of directed diffusion in a symmetric optical lattice

We demonstrate the phenomenon of directed diffusion in a symmetric periodic potential. This has been realized with cold atoms in a one-dimensional dissipative optical lattice. The stochastic process of optical pumping leads to a diffusive dynamics of the atoms through the periodic structure, while a zero-mean force which breaks the temporal symmetry of the system is applied by phase-modulating one of the lattice beams. The atoms are set into directed motion as a result of the breaking of the temporal symmetry of the system

Discontinuous vs continuous approaches for the nonlinear dynamics of an historic masonry tower

The present paper investigates, from an advanced numerical point of view, the progressive damage of the Amatrice (Rieti, Italy) civic clock tower, after a long sequence of strong earthquakes that struck Central Italy in 2016. Two advanced numerical models are here used to provide an insight into the modalities of progressive damage and the behaviour of the structure under strong dynamic excitations, namely a Discrete Element Method (DEM), the Non-Smooth Contact Dynamics (NSCD) method, and a FE Concrete Damage Plasticity (CDP) model. In both cases, a full 3D detailed discretization is adopted. From the numerical results, the role played by both the actual geometries and the insufficient resistance of the constituent materials are envisaged, showing a good match with actual crack patterns observed after the seismic sequence

Temperature and spatial diffusion of atoms cooled in a 3D lin⊥\perplin bright optical lattice

We present a detailed experimental study of a three-dimensional lin$\perp$lin bright optical lattice. Measurements of the atomic temperature and spatial diffusion coefficients are reported for different angles between the lattice beams, i.e. for different lattice constants. The experimental findings are interpretated with the help of numerical simulations. In particular we show, both experimentally and theoretically, that the temperature is independent of the lattice constant.Comment: accepted for publication in Eur. Phys. J.

Mercados, Sistemas de Intercambio y Tecnologías de Cálculo: Antropología de los Dispositivos de coordinación económica en el sector agrario. 16H348

El proyecto buscan reconectar economía y sociedad, describiendo fenómenos situados en la confluencia de la organización económica y el conocimiento. La problemática tiene como foco el mercado, visto desde una perspectiva de construcción social, analizando su génesis y sin considerarlo un ordenamiento inevitable y natural. Comprende dos líneas principales: a) el estudio de las prestaciones y sistemas de intercambio al interior de la familia (circulación de bienes a través de la herencia, intercambios matrimoniales, formas de cooperación y ayuda mutua, agroindustrias familiares, etc.); y, b) el análisis de los procesos de institucionalización de la economía en el agro, mediante el estudio etnográfico de las prácticas de cálculo y estimación de pequeños productores y asalariados rurales (constitución del trabajo como mercancía, participación de los pequeños productores en mercados, cooperativas, grupos de crédito, cadenas agroindustriales, etc.). La principal hipótesis de trabajo es que la institucionalización de la economía depende de un conjunto de mediadores (redes sociales, instrumentos y tecnologías de cálculo, determinados tipos de expertise que actúan como “prescriptores del mercado”, orientando el encuentro de la oferta y la demanda a través de revistas especializadas, etc.), cuya existencia no es tenida en cuenta por la visión económica estándar y que nos proponemos explorar a partir de herramientas de la sociología económica, la etnografía económica y la antropología de las ciencias y las técnicas

Oxidative stress and cardiovascular disease

The endothelium is one of the most important, and certainly the most extensive, organs involved in cardio- vascular homeostasis. The endothelium-derived vasoactive factors inhibiting smooth muscular cells contraction and proliferation, and platelet function, include nitric oxide (NO), prostacyclin and endothelial-derived hyperpolarizing factor. However, endothelial cells can also produce vasoconstrictive, proaggregant, promitogen mediators, such as thromboxane A2, prostaglandin H2, endothelin 1, and angiotensin II. Therefore, any impair- ment of endothelial function may trigger the typical chain of events of atherogenesis, characterised by vasocon- striction, cellular proliferation and thrombosis. In this regard, the biological link between endothelial dysfunction and atherosclerosis is a reduced bioavailability of NO. However, the precise mechanisms by which the endothelial dysfunction occurs remain still unclear. A decreased bioavailability of NO can be caused by its enhanced reactive oxygen species (ROS) breakdown. Oxidative stress may represent a common mechanism by which different cardiovascular risk factors cause endothelial dysfunction and trigger atherothrombotic process

Chlamydia pneumoniae in asymptomatic carotid atherosclerosis.

We evaluated, in 415 patients with asymptomatic carotid atherosclerosis: (i) the prevalence of C. pneumoniae DNA in atherosclerotic carotid plaques and peripheral blood mononuclear cells (PBMC); (i..