Analysis of Nd3+:glass, solar-pumped, high-powr laser systems

The operating characteristics of Nd(3+):glass lasers energized by a solar concentrator were analyzed for the hosts YAG, silicate glass, and phosphate glass. The modeling is based on the slab zigzag laser geometry and assumes that chemical hardening methods for glass are successful in increasing glass hardness by a factor of 4. On this basis, it was found that a realistic 1-MW solar-pumped laser might be constructed from phosphate glass 4 sq m in area and 2 mm thick. If YAG were the host medium, a 1-MW solar-pumped laser need only be 0.5 sq m in area and 0.5 cm thick, which is already possible. In addition, Nd(3+) doped glass fibers were found to be excellent solar-pumped laser candidates. The small diameter of fibers eliminates thermal stress problems, and if their diameter is kept small (10 microns), they propagate a Gaussian single mode which can be expanded and transmitted long distances in space. Fiber lasers could then be used for communications in space or could be bundled and the individual beams summed or phase-matched for high-power operation

The effects of news authorship, exclusiveness and media type in readers’ paying intent for online news: An experimental study

This study explores how news authorship, exclusiveness, and media type affect readers’ paying intent for digital contents. A web-based experiment involving 602 Spanish adults reveals that authorship (prestigious journalist), exclusiveness, and media type (legacy media and new media over unknown media) increase readers’ economic value assessments of online news. In addition, our results show that the interaction between authorship and media type is affected by the level of news exclusiveness: when an online article is written by a prestigious journalist and is exclusive, readers’ heuristic assessments of its economic value are biased toward new media over legacy ones, and thus privilege the former and penalize the latter in their pecuniary evaluations. These results might point to a change in readers’ consumption patterns, favoring the brand values, and news production processes of new media over legacy ones

Solar-pumped solid state Nd lasers

Solid state neodymium lasers are considered candidates for space-based polar-pumped laser for continuous power transmission. Laser performance for three different slab laser configurations has been computed to show the excellent power capability of such systems if heat problems can be solved. Ideas involving geometries and materials are offered as potential solutions to the heat problem

The APEX-CHAMP+ view of the Orion Molecular Cloud 1 core - Constraining the excitation with submillimeter CO multi-line observations

A high density portion of the Orion Molecular Cloud 1 (OMC-1) contains the prominent, warm Kleinmann-Low (KL) nebula that is internally powered by an energetic event plus a farther region in which intermediate to high mass stars are forming. Its outside is affected by ultraviolet radiation from the neighboring Orion Nebula Cluster and forms the archetypical photon-dominated region (PDR) with the prominent bar feature. Its nearness makes the OMC-1 core region a touchstone for research on the dense molecular interstellar medium and PDRs. Using the Atacama Pathfinder Experiment telescope (APEX), we have imaged the line emission from the multiple transitions of several carbon monoxide (CO) isotopologues over the OMC-1 core region. Our observations employed the 2x7 pixel submillimeter CHAMP+ array to produce maps (~ 300 arcsec x 350 arcsec) of 12CO, 13CO, and C18O from mid-J transitions (J=6-5 to 8-7). We also obtained the 13CO and C18O J=3-2 images toward this region. The 12CO line emission shows a well-defined structure which is shaped and excited by a variety of phenomena, including the energetic photons from hot, massive stars in the nearby Orion Nebula's central Trapezium cluster, active high- and intermediate-mass star formation, and a past energetic event that excites the KL nebula. Radiative transfer modeling of the various isotopologic CO lines implies typical H2 densities in the OMC-1 core region of ~10^4-10^6 cm^-3 and generally elevated temperatures (~ 50-250 K). We estimate a warm gas mass in the OMC-1 core region of 86-285 solar masses.Comment: 11 pages, 9 figures, accepted by A&

Análisis antracológico del yacimiento arqueológico de Peña Parda

Se presenta el estudio antracológico de los carbones recuperados en el abrigo de Peña Parda (Laguardia, Álava). El Nivel DI, de cronología calcolítica, es el de mayor fiabilidad estratigráfíca ya que el Nivel I incluye con bastante probabilidad restos vegetales de cronología reciente. En el Nivel III la madera más abundante es el boj (42%), seguido del tejo (33%). Otros taxones menores, presentes en porcentajes inferiores al 5% son: enebro, pino, gayuba/madroño, cornejo, fresno, hiedra, leguminosas, pomoidea, cerezo, roble/quejigo, grosellero y morrionera. Sugerimos que en el momento de ocupación del yacimiento las formaciones de bojedo debieron ser importantes en el entorno. La presencia del tejo debe responder a su capacidad de colonizar suelos delgados y rocosos

From Informal Housing to Housing at Risk, Preliminary Diagnosis of Some Neighborhoods in Quito

In the second half of the twentieth century in Ecuador, collective housing projects undertaken by the state began to emerge, while informal settlements consolidated on the outskirts of the city. The way in which these neighborhoods were consolidated has had an impact on the quality of life of their inhabitants. By allowing them to identify natural, social, and anthropic risks, they have accentuated and conditioned the safety of users, such as hillside location, context, materiality, accessibility, mobility, infrastructure, etc. The research is based on a comparative study of risks in three neighborhoods of Quito, to understand that both the participation of the people and the cooperation of the regulating entity are important for giving rise to housing projects. Based on the method proposed by Livingston and supported by the literature and bibliographic review, we seek to identify the risks that are generated or emphasized in the different stages of housing, highlighting the importance of building an integrated city based on the inhabitants and their way of inhabiting the space. Finally, we seek to understand that in the creation of housing projects, the appropriation of space makes it possible to turn a neighborhood into a community that reflects the diverse way of living of the users. Keywords: citizen participation, social housing, informal settlements, Quito. Resumen En la segunda mitad del siglo XX en Ecuador empezaron a surgir proyectos de vivienda colectiva emprendidos por el estado central, en paralelo en la periferia de la ciudad se consolidaron asentamientos informales. La forma en la que se consolidaron estos barrios ha tenido un impacto en la calidad de vida de sus habitantes; esto ha permitido identificar riesgos naturales, sociales y antrópicos, los mismos que se han acentuado y condicionan la seguridad de los usuarios, tales como ubicación sobre laderas, contexto, materialidad, accesibilidad, movilidad, infraestructura, etc. La investigación se basa en un estudio comparativo sobre riesgos presentes en tres barrios de Quito, con el fin de entender que tanto la participación de las personas como la cooperación de la entidad reguladora, son importantes al momento de dar lugar a proyectos de vivienda. Partiendo del método propuesto por Livingston y apoyado en la revisión literaria y bibliográfica, se busca identificar los riesgos que se generan o enfatizan en las diferentes etapas de la vivienda, resaltando la importancia de construir una ciudad integrada que tiene como base a los habitantes y su forma de habitar el espacio. Finalmente, se busca entender que en la creación de proyectos habitacionales la apropiación del espacio permite convertir a un barrio en una comunidad que refleja la forma diversa de habitar de los usuarios. Palabras Clave: Participación Ciudadana, Vivienda Social, Asentamientos Informales, Quito

On the kinematics of massive star forming regions: the case of IRAS 17233-3606

Direct observations of accretion disks around high-mass young stellar objects would help to discriminate between different models of formation of massive stars. However, given the complexity of massive star forming regions, such studies are still limited in number. Additionally, there is still no general consensus on the molecular tracers to be used for such investigations. Because of its close distance and high luminosity, IRAS 17233-3606 is a potential good laboratory to search for traces of rotation in the inner gas around the protostar(s). Therefore, we selected the source for a detailed analysis of its molecular emission at 230 GHz with the SMA. We systematically investigated the velocity fields of transitions in the SMA spectra which are not affected by overlap with other transitions, and searched for coherent velocity gradients to compare them to the distribution of outflows in the region. Beside CO emission we also used high-angular H2 images to trace the outflow motions driven by the IRAS 17233-3606 cluster. We find linear velocity gradients in many transitions of the same molecular species and in several molecules. We report the first detection of HNCO in molecular outflows from massive YSOs. We discuss the CH3CN velocity gradient taking into account various scenarios: rotation, presence of multiple unresolved sources with different velocities, and outflow(s). Although other interpretations cannot be ruled out, we propose that the CH3CN emission might be affected by the outflows of the region. Higher angular observations are needed to discriminate between the different scenarios. The present observations, with the possible association of CH3CN with outflows in a few thousands AU around the YSOs' cluster, (i) question the choice of the tracer to probe rotating structures, and (ii) show the importance of the use of H2 images for detailed studies of kinematics.Comment: accepted for publication in A&

Precision stellar radial velocity measurements with FIDEOS at the ESO 1-m telescope of La Silla

We present results from the commissioning and early science programs of FIDEOS, the new high-resolution echelle spectrograph developed at the Centre of Astro Engineering of Pontificia Universidad Catolica de Chile, and recently installed at the ESO 1m telescope of La Silla. The instrument provides spectral resolution R = 43,000 in the visible spectral range 420-800 nm, reaching a limiting magnitude of 11 in V band. Precision in the measurement of radial velocity is guaranteed by light feeding with an octagonal optical fibre, suitable mechanical isolation, thermal stabilisation, and simultaneous wavelength calibration. Currently the instrument reaches radial velocity stability of = 8 m/s over several consecutive nights of observation

Voltage rectification by a SQUID ratchet

We argue that the phase across an asymmetric dc SQUID threaded by a magnetic flux can experience an effective ratchet (periodic and asymmetric) potential. Under an external ac current, a rocking ratchet mechanism operates whereby one sign of the time derivative of the phase is favored. We show that there exists a range of parameters in which a fixed sign (and, in a narrower range, even a fixed value) of the average voltage across the ring occurs, regardless of the sign of the external current dc component.Comment: 4 pages, 4 EPS figures, uses psfig.sty. Revised version, to appear in Physical Review Letters (26 August 1996