257 research outputs found
Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: The KINGFISH Sample
Interstellar dust and starlight are modeled for the galaxies of the project "Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel." The galaxies were observed by the Infrared Array Camera and the Multiband Imaging Photometer for Spitzer on Spitzer Space Telescope, and the Photodetector Array Camera and Spectrometer and the Spectral and Photometric Imaging Receiver on Herschel Space Observatory. With data from 3.6 to 500 μm, dust models are strongly constrained. Using a physical dust model, for each pixel in each galaxy we estimate (1) dust surface density, (2) dust mass fraction in polycyclic aromatic hydrocarbons (PAHs), (3) distribution of starlight intensities heating the dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR luminosity originating in subregions with high starlight intensity. The dust models successfully reproduce the observed global and resolved spectral energy distributions. With the angular resolution of Herschel, we obtain well-resolved maps (available online) for the dust properties. As in previous studies, we find the PAH fraction q_(PAH) to be an increasing function of metallicity, with a threshold oxygen abundance Z/Z⊙ ≈ 0.1, but we find the data to be fitted best with q_(PAH) increasing linearly with log(O/H) above a threshold value of 0.15(O/H)⊙. We obtain total dust masses for each galaxy by summing the dust mass over the individual map pixels; these "resolved" dust masses are consistent with the masses inferred from a model fit to the global photometry. The global dust-to-gas ratios obtained from this study are found to correlate with galaxy metallicities. Systems with Z/Z⊙ ≳ 0.5 have most of their refractory elements locked up in dust, whereas in systems with Z/Z⊙ ≾ 0.3 most of these elements tend to remain in the gas phase. Within galaxies, we find that q_(PAH) is suppressed in regions with unusually warm dust with vL_v(70 μm) ≳ 0.4L_(dust). With knowledge of one long-wavelength flux density ratio (e.g., f₁₆₀/f₅₀₀), the minimum starlight intensity heating the dust (U_(min)) can be estimated to within ~50%, despite a variation in U_(min) of more than two orders of magnitude. For the adopted dust model, dust masses can be estimated to within ~0.2 dex accuracy using the f₁₆₀/f₅₀₀ flux ratio and the integrated dust luminosity, and to ~0.07 dex accuracy using the 500 μm luminosity vL_v(500 µm) alone. There are additional systematic errors arising from the choice of dust model, but these are hard to estimate. These calibrated prescriptions for estimating starlight heating intensity and dust mass may be useful for studies of high-redshift galaxies
Common-Resolution Convolution Kernels for Space- and Ground-Based Telescopes
Multi-wavelength study of extended astronomical objects requires combining
images from instruments with differing point spread functions (PSFs). We
describe the construction of convolution kernels that allow one to generate
(multi-wavelength) images with a common PSF, thus preserving the colors of the
astronomical sources. We generate convolution kernels for the cameras of the
Spitzer Space Telescope, Herschel Space Observatory, Galaxy Evolution Explorer
(GALEX), Wide-field Infrared Survey Explorer (WISE), ground-based optical
telescopes (Moffat functions and sum of Gaussians), and Gaussian PSFs. These
kernels allow the study of the Spectral Energy Distribution (SED) of extended
objects, preserving the characteristic SED in each pixel. The convolution
kernels and the IDL packages used to construct and use them are made publicly
available
Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: The KINGFISH Sample
Interstellar dust and starlight are modeled for the galaxies of the project “Key Insights on Nearby Galaxies: A FarInfrared Survey with Herschel.” The galaxies were observed by the Infrared Array Camera and the Multiband
Imaging Photometer for Spitzer on Spitzer Space Telescope, and the Photodetector Array Camera and Spectrometer
and the Spectral and Photometric Imaging Receiver on Herschel Space Observatory. With data from 3.6 to
500 μm, dust models are strongly constrained. Using a physical dust model, for each pixel in each galaxy we
estimate (1) dust surface density, (2) dust mass fraction in polycyclic aromatic hydrocarbons (PAHs), (3)
distribution of starlight intensities heating the dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR
luminosity originating in subregions with high starlight intensity. The dust models successfully reproduce the
observed global and resolved spectral energy distributions. With the angular resolution of Herschel, we obtain
well-resolved maps (available online) for the dust properties. As in previous studies, we find the PAH fraction qPAH
to be an increasing function of metallicity, with a threshold oxygen abundance Z/Ze ≈ 0.1, but we find the data to
be fitted best with qPAH increasing linearly with log O H ( ) above a threshold value of 0.15(O/H)e. We obtain total
dust masses for each galaxy by summing the dust mass over the individual map pixels; these “resolved” dust
masses are consistent with the masses inferred from a model fit to the global photometry. The global dust-to-gas
ratios obtained from this study are found to correlate with galaxy metallicities. Systems with Z/Ze 0.5 have
most of their refractory elements locked up in dust, whereas in systems with Z/Ze 0.3 most of these elements
tend to remain in the gas phase. Within galaxies, we find that qPAH is suppressed in regions with unusually warm
dust with nL L n ( ) 70 m 0.4 m dust. With knowledge of one long-wavelength flux density ratio (e.g., f160/f500), the
minimum starlight intensity heating the dust (Umin) can be estimated to within ∼50%, despite a variation in Umin of
more than two orders of magnitude. For the adopted dust model, dust masses can be estimated to within ∼0.2 dex
accuracy using the f160/f500 flux ratio and the integrated dust luminosity, and to ∼0.07 dex accuracy using the
500 μm luminosity nLn ( ) 500 mm alone. There are additional systematic errors arising from the choice of dust model, but these are hard to estimate. These calibrated prescriptions for estimating starlight heating intensity and
dust mass may be useful for studies of high-redshift galaxies
Plan de viabilidad empresa exportaciones de apoyo al sector vinícola leonés
Con motivo del proyecto de fin de carrera de ‘Grado en Administración y Dirección de Empresas’ se ha propuesto realizar un estudio de la viabilidad, y la posible creación y puesta en marcha de una empresa de exportaciones asociada a productores de un importante y conocido gremio leonés. Gracias a esta idea de negocio, apoyaremos a pequeñas pymes con recursos económicos y conocimientos limitados, actualmente en dificultades para sacar al mercado su producción. De esta manera potenciaremos su negocio bajo una pequeña inversión rápidamente recuperable. Además, bajo la motivación anterior, comprobaremos que la inversión inicial de nuestra empresa es realmente saneable en un periodo no superior a dos años. Para ello, se proponen una serie de estrategias muy ligadas al comercio internacional, la logística y distribución del producto. De la misma manera, se han analizado los posibles problemas que podría conllevar la puesta en marcha de la empresa y como explotar las posibles oportunidades. Por último, también se ha proyectado un ‘Business plan’ a 5 años, dónde se propone una inversión inicial para concluir con un proyecto empresarial atractivo y sobre todo rentable para el posible inverso
The Chronic Social-employment Precariousness of the Canary Islands
En las tres últimas décadas, Canarias ha logrado insertarse en los selectos circuitos de la globalización
económica. Actividad turística, movimientos migratorios, comercio internacional,
inversiones públicas y privadas y avance tecnológico son, básicamente, las fuerzas que señalan
la globalización de Canarias. Sin embargo, la evolución del empleo y de las condiciones sociales
de vida no expresa un desarrollo tan satisfactorio. En este artículo analizamos las causas
principales que subyacen en el proceso crónico de precariedad sociolaboral de Canarias.
En la primera parte, nos detenemos en el sistema productivo, para resaltar las deficiencias
más evidentes de la oferta económica. En la segunda parte, analizamos los efectos sociales
que retroalimentan el deterioro: la pobreza, el desempleo masivo y la precariedad salarial.In the three last
decades, the Canary Islands have managed to be inserted in the select circuits of the economic
globalization. Tourist activity, migratory movements, international trade, public
and private investments, and technological advance is, basically, the forces that indicate
the globalization of the Canary Islands. Nevertheless, the evolution of the work and the
social conditions of life does not express a so satisfactory development. In this article we
analyzed the leading causes that underlie in the continuous process of precarious work of
the Canary Islands. In the first part, we pause in the productive system, to emphasize the
most evidence deficiencies of the economic supply. In the second part, we analyzed the social
effects that feed back the deterioration: the poverty, mass unemployment, and low wage
Dust models post-Planck: constraining the far-infrared opacity of dust in the diffuse interstellar medium
We compare the performance of several dust models in reproducing the dust
spectral energy distribution (SED) per unit extinction in the diffuse
interstellar medium (ISM). We use our results to constrain the variability of
the optical properties of big grains in the diffuse ISM, as published by the
Planck collaboration.
We use two different techniques to compare the predictions of dust models to
data from the Planck HFI, IRAS and SDSS surveys. First, we fit the far-infrared
emission spectrum to recover the dust extinction and the intensity of the
interstellar radiation field (ISRF). Second, we infer the ISRF intensity from
the total power emitted by dust per unit extinction, and then predict the
emission spectrum. In both cases, we test the ability of the models to
reproduce dust emission and extinction at the same time.
We identify two issues. Not all models can reproduce the average dust
emission per unit extinction: there are differences of up to a factor
between models, and the best accord between model and observation is obtained
with the more emissive grains derived from recent laboratory data on silicates
and amorphous carbons. All models fail to reproduce the variations in the
emission per unit extinction if the only variable parameter is the ISRF
intensity: this confirms that the optical properties of dust are indeed
variable in the diffuse ISM.
Diffuse ISM observations are consistent with a scenario where both ISRF
intensity and dust optical properties vary. The ratio of the far-infrared
opacity to the band extinction cross-section presents variations of the
order of ( in extreme cases), while ISRF intensity varies
by ( in extreme cases). This must be accounted for in
future modelling.Comment: A&A, in pres
Experiencias formativas en el área de conocimiento artístico en la carrera Maestro en Primera Infancia
El presente trabajo de investigación tuvo como propósito profundizar en las experiencias
formativas en el área de Conocimiento Artístico llevadas a cabo por las estudiantes que
transitan por la Carrera Maestro en Primera Infancia del Consejo de Formación en Educación.
La decisión se basó en que muchas veces las prácticas educativas perpetúan técnicas, modelos
y estrategias, dificultando así propuestas innovadoras que impliquen contemplar ideas,
experiencia o nuevos paradigmas. Al contar con una carrera novel con especificidad en la
Primera Infancia se consideró importante observar los procesos llevados a cabo por las
estudiantes y visualizar las construcciones sobre la enseñanza; es decir, las apropiaciones,
prácticas, experiencias, transferencias y confianza en las formas de enseñar.
Los trayectos fueron observados utilizando una metodología que integró la encuesta a
estudiantes en diferentes momentos de la cursada, la observación participante y la entrevista
en profundidad. Se utilizaron además aspectos de la investigación artística por el valor que la
misma puede aportar al tema. Se integró en ella la etnografía visual ya que permite el análisis
de los productos artísticos realizados por los niños y planificados por las estudiantes.
Al finalizar se plantearon aportes para continuar pensando aspectos sustanciales como la
interdisciplinariedad, el valor del arte en el proceso formativo y la importancia de la
experiencia
Poly(arylene Ether Sulfones): Synthesis, Modifications and Applications.
Poly(arylene ether sulfones) were synthesized by aromatic nucleophilic polymerization of the monomers; 4,4\sp\prime-biphenol, 4-chlorophenyl sulfone, hydroquinone, and tert-butylhydroquinone. Different conditions of temperature and solvent systems were used to determine the best synthetic approaches for the preparation of poly-(4,4\sp\prime-biphenol/4-chlorophenyl sulfone) (1:1), poly-(4-4\sp\prime-biphenol/4-chlorophenyl sulfone/hydroquinone) (1:2:1), and poly (4-4\sp\prime-biphenol/4-chlorophenyl sulfone/tert-butylhydroquinone) (1:2:1). The use of aprotic high boiling solvent mixtures of N-methyl-2-pyrrolidone (NMP), and N-cyclohexyl-2-pyrrolidone (CHP), facilitated the formation of polymers with structures which can easily be controlled by varying the ratio of monomers, and by varying the concentration of reactants. The polymers were functionalized and modified by silylation, amination and aminomethylation. Directed silylation by electrophilic substitution ortho to the ether group was effected by bromination, followed by lithiation with butyllithium before quenching with chlorotrimethyl-silane. Silylation ortho to the sulfonyl group was effected by metal hydrogen exchange with butyllithium before quenching with chlorotrimethysilane. A maximum of two trimethylsilyl substituents can be introduced for every repeat unit. Modification by amination was accomplished by the introduction of a nitro group and subsequent reduction of the nitro group to an amine. Sodium dithionite was more effective than sulfur/sodium borohydride, or titanium tetrachloride/lithium aluminum hydride as a reducing agent. Degrees of functionalization up to 2 amino groups per repeat unit were achieved. Aminomethylation was performed in a two step process. The first step involved introduction of an N-methylphthalimide substituent by condensation of the activated arylene repeat units with N-hydroxymethyl-phthalimide in the presence of a highly protic solvent mixture, trifluoroacetic acid and trifluoromethanesulfonic acid. The second step involved hydrazinolysis to cleave the phthalimide group and to release aminomethyl substituents. The polymers and their functionalized derivatives were characterized by \sp1H and \sp{13}C NMR, infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and viscosity measurements. \sp{13}C NMR chemical shifts calculated from additivity rule were compared with the assigned chemical shifts. The spectroscopic results are consistent with the assigned structures. The glass transition temperatures (Tg) of the polymers were compared with predicted values based upon molar additivity of incremental values for the structural units. As predicted, tert-butyl substituents raised the Tg while introduction of the more flexible trimethylsilyl groups reduced the Tg\u27s compared to unsubstituted polymers
- …