Liner radius fluctuations in a high-gain Cherenkov free-electron laser

Phase shifts in the propagating electromagnetic field of a Cherenkov free-electron laser (CFEL) can affect its gain. The phase velocity of an electromagnetic wave varies, for example, when the lined waveguide is inhomogeneous along its length. In this paper, we study quantitatively the saturated power of a particular CFEL at both weak and strong electron-beam pumping when the inner radius of the liner contains fluctuations along the waveguide. We show that the gain bandwidth of the CFEL is substantially broadened when the CFEL is pumped with a high-current beam. We also show that the design of a CFEL needs to include optimization with respect to sensitivity to liner fluctuations, especially for weakly pumped CFELs, that is, CFELs that use a low-current electron-beam density. This optimization can be relaxed for more strongly pumped CFELs

El col·leccionisme d’antiguitats com a mitjà de promoció social: el cas de Josep de Maranges i Marimon. Anàlisi del Compendio histórico, resumen y descripción de la antiquisima ciudad de Empurias

L’antiquarisme clàssic fou una eina de promoció social durant la Il·lustració. Un món associat també als estudis d’història antiga. Aquest article dóna mostra d’això a partir de Josep de Maranges i Marimon i el seu Compendio. L’obra aporta noves dades sobre la seva biografia i analitza les motivacions que el dugueren a escriure-la. La primera redacció del Compendio es relaciona amb una oferta al Príncep d’Astúries d’una col·lecció d’antiguitats reco- llida per Maranges. Això no fou una estratègia aïllada. La família Maranges anteriorment ja havia utilitzat aquest recurs per obrir-se nous cercles socials

The 0.03-10Mo mass function of young open clusters

We report the present day mass functions (PDMFs) of 3 young open clusters over a mass range from 30 Jupiter masses to 10~\msunn. The PDMFs of the 3 clusters are remarkably similar, suggesting little impact of specific conditions (stellar density, metallicity, early dynamical evolution) on the mass distribution. Functional forms are provided to allow quantitative comparison with MFs derived in other environments.Comment: 6 pages, to appear in "IMF@50", Corbelli, Palla, Zinnecker ed

Detection of the Ammonium Ion in Space

We report on the detection of a narrow feature at 262816.73 MHz towards Orion and the cold prestellar core B1-bS, that we attribute to the 1(0)-0(0) line of the deuterated Ammonium ion, NH3D+. The observations were performed with the IRAM 30m radio telescope. The carrier has to be a light molecular species as it is the only feature detected over 3.6 GHz of bandwidth. The hyperfine structure is not resolved indicating a very low value for the electric quadrupolar coupling constant of Nitrogen which is expected for NH3D+ as the electric field over the N nucleus is practically zero. Moreover, the feature is right at the predicted frequency for the 1(0)-0(0) transition of the Ammonium ion, 262817(6) MHz (3sigma), using rotational constants derived from new infrared data obtained in our laboratory in Madrid. The estimated column density is 1.1(0.2)e12 cm-2. Assuming a deuterium enhancement similar to that of NH2D, we derive N(NH4+) sim 2.6e13 cm-2, i.e., an abundance for Ammonium of a few 1e(-11).Comment: Accepted for publication in the Astrophysical Journal Letters 04 June 201

Improved determination of the 1(0)-0(0) rotational frequency of NH3D+ from the high resolution spectrum of the v4 infrared band

The high resolution spectrum of the v4 band of NH3D+ has been measured by difference frequency IR laser spectroscopy in a multipass hollow cathode discharge cell. From the set of molecular constants obtained from the analysis of the spectrum, a value of 262817(6) MHz (3sigma) has been derived for the frequency of the 1(0)-0(0) rotational transition. This value supports the assignment to NH3D+ of lines at 262816.7 MHz recorded in radio astronomy observations in Orion-IRc2 and the cold prestellar core B1-bS.Comment: Accepted for publication in the Astrophysical Journal Letters 04 June 201

Near-Infrared Spectroscopy of Molecular Filaments in the Reflection Nebula NGC 7023

We present near-infrared spectroscopy of fluorescent molecular hydrogen (H_2) emission from molecular filaments in the reflection nebula NGC 7023. We derive the relative column densities of H_2 rotational-vibrational states from the measured line emission and compare these results with several model photodissociation regions covering a range of densities, incident UV-fields, and excitation mechanisms. Our best-fit models for one filament suggest, but do not require, either a combination of different densities, suggesting clumps of 10^6 cm^{-3} in a 10^4 - 10^5 cm^{-3} filament, or a combination of fluorescent excitation and thermally-excited gas, perhaps due to a shock from a bipolar outflow. We derive densities and UV fields for these molecular filaments that are in agreement with previous determinations.Comment: ApJ accepted, 26 pages including 5 embedded figures, uses AASTEX. Also available at http://www-astronomy.mps.ohio-state.edu/~martini/pubs.htm

La Técnica de Rejilla como Instrumento de Evaluación y Formulación de Hipótesis Clínicas

El presente artículo se inicia con una presentación de la Técnica de Rejilla (TR), enmarcada en el contexto de la Teoría de los Constructos Personales (TCP). A continuación, se expone la aplicación de la TR al caso de Ana diagnosticada por trastorno depresivo mayor, bulimia nerviosa y trastorno de personalidad por evitación, además de presentar otros síntomas variados. Se eligió este caso por su complejidad clínica y por la manera en que se ven reflejados los síntomas de la paciente en su estructura cognitiva, puesta de manifiesto por la TR. A pesar de que Ana pidió ayuda por iniciativa propia, en las sesiones se muestra reticente a hablar de sí misma, por lo que la TR resultó ser un buen medio de aproximación a la visión del mundo de la cliente, y un instrumento útil para formular hipótesis clínicas