Continuous atom laser with Bose-Einstein condensates involving three-body interactions

We demonstrate, through numerical simulations, the emission of a coherent continuous matter wave of constant amplitude from a Bose-Einstein Condensate in a shallow optical dipole trap. The process is achieved by spatial control of the variations of the scattering length along the trapping axis, including elastic three body interactions due to dipole interactions. In our approach, the outcoupling mechanism are atomic interactions and thus, the trap remains unaltered. We calculate analytically the parameters for the experimental implementation of this CW atom laser.Comment: 11 pages, 4 figure

BN 52021 (a platelet activating factor-receptor antagonist) decreases alveolar macrophage-mediated lung injury in experimental extrinsic allergic alveolitis.

Several lines of research indirectly suggest that platelet activating factor (PAF) may intervene in the pathogenesis of extrinsic allergic alveolitis (EAA). The specific aim of our study was to evaluate the participation of PAF on macrophage activation during the acute phase of EAA in an experimental model of this disease developed in guinea pigs. Initially we measured the concentration of PAF in bronchoalvedar lavage fluid, blood and lung tissue. In a second phase we evaluate the participation of PAF on alveolar macrophage activation and parenchymal lung injury. The effect of PAF on parenchymal lung injury was evaluated by measuring several lung parenchymatous lesion indices (lung index, bronchoalvedar lavage fluid (BALF) lactic hydrogenase activity and BALF alkaline phosphatase activity) and parameters of systemic response to the challenge (acute phase reagents). We observed that induction of the experimental EAA gave rise to an increase in the concentration of PAF in blood and in lung tissue. The use of the PAF-receptor antagonist BN52021 decreases the release of lysosomal enzymes (beta-glucuronidase and tartrate-sensitive acid phosphatase) to the extracellular environment both in vivo and in vitro. Furthermore, antagonism of the PAF receptors notably decreases pulmonary parenchymatous lesion. These data suggest that lung lesions from acute EAA are partly mediated by local production of PAF

Resolving the mystery of milliwatt-threshold opto-mechanical self-oscillation in dual-nanoweb fiber

It is interesting to pose the question: How best to design an optomechanical device, with no electronics, optical cavity, or laser gain, that will self-oscillate when pumped in a single pass with only a few mW of single-frequency laser power? One might begin with a mechanically resonant and highly compliant system offering very high optomechanical gain. Such a system, when pumped by single-frequency light, might self-oscillate at its resonant frequency. It is well-known, however, that this will occur only if the group velocity dispersion of the light is high enough so that phonons causing pump-to-Stokes conversion are sufficiently dissimilar to those causing pump-to-anti-Stokes conversion. Recently it was reported that two light-guiding membranes 20 μm wide, ∼500 nm thick and spaced by ∼500 nm, suspended inside a glass fiber capillary, oscillated spontaneously at its mechanical resonant frequency (∼6 MHz) when pumped with only a few mW of single-frequency light. This was surprising, since perfect Raman gain suppression would be expected. In detailed measurements, using an interferometric side-probing technique capable of resolving nanoweb movements as small as 10 pm, we map out the vibrations along the fiber and show that stimulated intermodal scattering to a higher-order optical mode frustrates gain suppression, permitting the structure to self-oscillate. A detailed theoretical analysis confirms this picture. This novel mechanism makes possible the design of single-pass optomechanical oscillators that require only a few mW of optical power, no electronics nor any optical resonator. The design could also be implemented in silicon or any other suitable material

Generation of a VUV-to-visible Raman frequency comb in hydrogen-filled kagom\'e photonic crystal fiber

We report the generation of a purely vibrational Raman comb, extending from the vacuum ultraviolet (184 nm) to the visible (478 nm), in hydrogen-filled kagom\'e-style photonic crystal fiber pumped at 266 nm. Stimulated Raman scattering and molecular modulation processes are enhanced by higher Raman gain in the ultraviolet. Owing to the pressure-tunable normal dispersion landscape of the fiber-gas system in the ultraviolet, higher-order anti-Stokes bands are generated preferentially in higher-order fiber modes. The results pave the way towards tunable fiber-based sources of deep- and vacuum ultraviolet light for applications in, e.g., spectroscopy and biomedicine.Comment: 4 pages, 5 figures, 1 tabl

Coherent control of flexural vibrations in dual-nanoweb fibers using phase-modulated two-frequency light

Coherent control of the resonant response in spatially extended optomechanical structures is complicated by the fact that the optical drive is affected by the back-action from the generated phonons. Here we report a new approach to coherent control based on stimulated Raman-like scattering, in which the optical pressure can remain unaffected by the induced vibrations even in the regime of strong optomechanical interactions. We demonstrate experimentally coherent control of flexural vibrations simultaneously along the whole length of a dual-nanoweb fiber, by imprinting steps in the relative phase between the components of a two-frequency pump signal,the beat frequency being chosen to match a flexural resonance. Furthermore, sequential switching of the relative phase at time intervals shorter than the lifetime of the vibrations reduces their amplitude to a constant value that is fully adjustable by tuning the phase-modulation depth and switching rate. The results may trigger new developments in silicon photonics, since such coherent control uniquely decouples the amplitude of optomechanical oscillations from power-dependent thermal effects and nonlinear optical loss.Comment: This 11 pages-long document includes the main text with 8 figures and an appendix with one figur

The values of intrapleural pressure before the removal of chest tube in non-complicated pulmonary lobectomies

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A first-principles analysis of the magnetism of CuII polynuclear coordination complexes: the case of [Cu4(bpy)4(aspartate)2(H2O)3](ClO4)4·2.5H2O

The magnetic structure of the [Cu4(bpy)4(aspartate)2(H2O)3](ClO4)4·2.5 H2Ocrystal - using fractional coordinates determined at room-temperature ¿ has beenanalysed in detail. This analysis has been carried out by extending our first principlesbottom-up theoretical approach, which was initially designed to study through-spacemagnetic interactions, to handle through-bond magnetic interactions. The only input datarequired by this approach are the values of the computed JAB exchange parameters for allthe unique pairs of spin-containing centres. The results allow the magnetic structure ofthe crystal, which presents two types of isolated tetranuclear CuII clusters, to be definedin quantitative terms. Each of these clusters presents ferro and antiferromagneticinteractions, the former being stronger, although outnumbered by the latter. Thecomputed magnetic susceptibility curve shows the same qualitative features as theexperimental data. However, there are small differences that are presumed to beassociated with the use of room-temperature crystal coordinates

Content and distribution of glycogen in relation to the gametogenic cycle of a natural population of Ruditapes decussatus (L., 1758) located in the Baldaio lagoons (Galicia, northwestern Spain)

Bivalve reproduction is associated with complex cycles of energy reserve storage. We studied the gametogenic cycle of the clam Ruditapes decussatus (L., 1758), as well as variations in its glycogen composition, using individuals from a natural population located in the Baldaio lagoons (Galicia, northwestern Spain). The gametogenic cycle, as well as variations in glycogen composition, were studied throughout the life cycle of the clam Ruditapes decussatus (L., 1758), using individuals from a natural population located in the Baldaio lagoons (Galicia, northwestern Spain). The gametogenesis begins in December and January, after a period of sexual inactivity during the months of November and December. This population reaches sexual maturity during a period extending from mid-May until August, and spawning takes place from June to August, followed by a post-spawning period. To study of glycogen content and its distribution, the clams were dissected out into different parts: foot, ledge of the mantle, gills, adductor muscle and gonad-digestive gland. The lowest content of glycogen was found at maturity, especially during spawning. The gonad and the visceral mass accumulate between 36 and a 50% of the total glycogen present in the animal, whereas the lowest values are in the foot, which contains 6%.La reproducción en bivalvos está asociada a ciclos complejos de almacenamiento de reservas energéticas. Se ha estudiado la gametogénesis de la almeja fina Ruditapes decussatus (L., 1758), y la variación en ella de la composición de glucógeno, con ejemplares de una población natural de las lagunas de Baldaio (A Coruña). La gametogénesis se inicia entre diciembre y enero, después de un periodo de reposo sexual durante noviembre y diciembre, y la madurez sexual se alcanza desde mediados de mayo hasta agosto; la puesta tiene lugar de junio a agosto y va seguida de un periodo de pospuesta. Para el estudio del contenido en glucógeno y su distribución, se diseccionaron las siguientes partes de las almejas: el pie, el reborde muscular del manto, las branquias, los sifones, el músculo aductor y la gónada con la masa visceral, que incluye el aparato digestivo, los palpos labiales, los ganglios nerviosos y la región reno-pericárdica. El contenido en glucógeno más bajo se obtiene en la madurez y, sobre todo, en época de puesta. La gónada y la masa visceral acumulan entre el 36 y el 50% del glucógeno total existente en el animal, mientras que los valores más bajos se encuentran en el pie, con el 6%.Instituto Español de Oceanografí