5,512 research outputs found
Water production in comet 81P/Wild 2 as determined by Herschel/HIFI
The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations
of water production rates in comets. In this Letter we present HIFI observations of the fundamental 1_(10)â1_(01) (557 GHz) ortho and 1_(11)â0_(00)
(1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission
with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and
solar infrared radiation. We derive a mean water production rate of 1.0 Ă 10^(28) molecules s^(â1) at a heliocentric distance of 1.61 AU about 20 days
before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we
constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes
A review of approaches to estimate wildfire plume injection height within large-scale atmospheric chemical transport models
Landscape fires produce smoke containing a very wide variety of chemical species, both gases and aerosols. For larger, more intense fires that produce the greatest amounts of emissions per unit time, the smoke tends initially to be transported vertically or semi-vertically close by the source region, driven by the intense heat and convective energy released by the burning vegetation. The column of hot smoke rapidly entrains cooler ambient air, forming a rising plume within which the fire emissions are transported. The characteristics of this plume, and in particular the height to which it rises before releasing the majority of the smoke burden into the wider atmosphere, are important in terms of how the fire emissions are ultimately transported, since for example winds at different altitudes may be quite different. This difference in atmospheric transport then may also affect the longevity, chemical conversion, and fate of the plumes chemical constituents, with for example very high plume injection heights being associated with extreme long-range atmospheric transport. Here we review how such landscape-scale fire smoke plume injection heights are represented in larger-scale atmospheric transport models aiming to represent the impacts of wildfire emissions on component of the Earth system. In particular we detail (i) satellite Earth observation data sets capable of being used to remotely assess wildfire plume height distributions and (ii) the driving characteristics of the causal fires. We also discuss both the physical mechanisms and dynamics taking place in fire plumes and investigate the efficiency and limitations of currently available injection height parameterizations. Finally, we conclude by suggesting some future parameterization developments and ideas on Earth observation data selection that may be relevant to the instigation of enhanced methodologies aimed at injection height representation
Underwater radiated noise levels of a research icebreaker in the central Arctic Ocean
U.S. Coast Guard Cutter Healy\u27s underwater radiated noise signature was characterized in the central Arctic Ocean during different types of ice-breaking operations. Propulsion modes included transit in variable ice cover, breaking heavy ice with backing-and-ramming maneuvers, and dynamic positioning with the bow thruster in operation. Compared to open-water transit, Healy\u27s noise signature increased approximately 10âdB between 20âHz and 2âkHz when breaking ice. The highest noise levels resulted while the ship was engaged in backing-and-ramming maneuvers, owing to cavitation when operating the propellers astern or in opposing directions. In frequency bands centered near 10, 50, and 100âHz, source levels reached 190â200âdB re: 1âÎŒPa at 1âm (full octave band) during ice-breaking operations
Bootstrapping pairs in Distance-Based Regression
Distance-based regression is a prediction method consisting of two steps: from distances between observations we obtain latent variables which, in turn, are the regressors in an ordinary least squares linear model. Distances are computed from actually observed predictors by means of a suitable dissimilarity function. Being in general nonlinearly related with the response their selection by the usual F tests is unavailable. In this paper we propose a solution to this predictor selection problem, by defining generalized test statistics and adapting a non-parametric bootstrap method to estimate their p-values. We include a numerical example with automobile insurance data.non-parametric bootstrap, automobile insurance data, predictors selection, distance-based regression
La cueva de Basaula (BarĂndano) y el arte postpaleolĂtico navarro
En este artĂculo se analiza y estudia el corpus parietal de los grafismos localizados en la GalerĂa
del Felino de la Cueva de Basaula, y se expone un estado de la cuestiĂłn sobre la comprensiĂłn del arte postpaleolĂtico
esquemĂĄtico peninsular y navarro; asĂ como del fenĂłmeno complejo del arte esquemĂĄtico abstracto
1864â1903: Progreso, academicismo y arte prehistĂłrico. Sustrato sociocultural del arte lĂșdico.
En este artĂculo se reflexiona sobre la manera en que influyeron en la primera fase
de la investigaciĂłn sobre el arte paleolĂtico, o del arte lĂșdico (1864â1903), el contexto social, cultural e intelectual de finales del s. XIX y las primeras dĂ©cadas del s. XX, el transformismo, el ideal de progreso, la etnografĂa, etc. Se hace especial hincapiĂ© en cĂłmo el contexto histĂłricoartĂstico (âarte por el arteâ, conflicto entre academicismo y la incipiente renovaciĂłn plĂĄstica) mediatizĂł la forma de mirar y enjuiciar las manifestaciones artĂsticas paleolĂticas.------This article reflects on the way the social, cultural and intellectual context at the end of nineteenth and the first decades of the XXth centuries, influenced the first phase of the
investigation about the palaeolithic art, or playful art (1864â1903), and also the transformism, the idea of progress, the ethnography, and so on. This article emphasized how the historicalâartistic context (ÊșArt for artÊčs sakeÊș, conflict between academic world and the incipient plastic renovation) mediatized the way of looking and judging the artistic palaeolithic manifestations
El yacimiento de Ordoiz (Estella)
Se expone un estado de la cuestiĂłn sobre el yacimiento de Ordoiz (Estella), con los datos
disponibles tras la intervenciĂłn de 1998. Partiendo de estos datos se analiza la cultura material del asentamiento,
modos de vida y rasgos ecolĂłgicos/paisajĂsticos. A la vista de las dificultades derivadas de su conservaciĂłn,
se le atribuye una cronologĂa del Edad del Bronce genĂ©rica
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