5,717 research outputs found
Cold gas and a Milky Way-type 2175 {\AA} bump in a metal-rich and highly depleted absorption system
We report the detection of a strong Milky Way-type 2175 \AA extinction
bump at = 2.1166 in the quasar spectrum towards SDSS J121143.42+083349.7
from the Sloan Digital Sky Survey (SDSS) Data Release 10. We conduct follow up
observations with the Echelle Spectrograph and Imager (ESI) onboard the Keck-II
telescope and the Ultraviolet and Visual Echelle Spectrograph (UVES) on the
VLT. This 2175 \AA absorber is remarkable in that we simultaneously detect
neutral carbon (C I), neutral chlorine (Cl I), and carbon monoxide (CO). It
also qualifies as a damped Lyman alpha system. The J1211+0833 absorber is found
to be metal-rich and has a dust depletion pattern resembling that of the Milky
Way disk clouds. We use the column densities of the C I fine structure states
and the C II/C I ratio (under the assumption of ionization equilibrium) to
derive the temperature and volume density in the absorbing gas. A Cloudy
photoionization model is constructed, which utilizes additional atoms/ions to
constrain the physical conditions. The inferred physical conditions are
consistent with a canonical cold (T 100 K) neutral medium with a high
density ((H I) 100 cm) and a slightly higher pressure than the
local interstellar medium. Given the simultaneous presence of C I, CO, and the
2175 \AA bump, combined with the high metallicity, high dust depletion level
and overall low ionization state of the gas, the absorber towards J1211+0833
supports the scenario that the presence of the bump requires an evolved stellar
population.Comment: 18 pages, 17 figures, to be published in MNRA
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Tailored Palladium Catalysts for Selective Synthesis of Conjugated Enynes by Monocarbonylation of 1,3-Diynes
For the first time, the monoalkoxycarbonylation of easily available 1,3-diynes to give synthetically useful conjugated enynes has been realized. Key to success was the design and utilization of the new ligand 2,2â˛-bis(tert-butyl(pyridin-2-yl)phosphanyl)-1,1â˛-binaphthalene (Neolephos), which permits the palladium-catalyzed selective carbonylation under mild conditions, providing a general preparation of functionalized 1,3-enynes in good-to-high yields with excellent chemoselectivities. Synthetic applications that showcase the possibilities of this novel methodology include an efficient one-pot synthesis of 4-aryl-4H-pyrans as well as the rapid construction of various heterocyclic, bicyclic, and polycyclic compounds. Š 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA
Lethal and Sublethal Effects of Methoxyfenozide on the Development, Survival and Reproduction on of the Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)
The lethal and sublethal effects of the ecdysone agonist methoxyfenozide on the fall armyworm, Spodoptera frugiperda (J. E. Smith), were investigated by feeding a methoxyfenozide-treated diet to fifth instars until pupation in doses corresponding to the LC10 and LC25 for the compound. Larval mortality reached 8% and 26% in the low and high concentration groups, respectively, on the seventh day of the experiment. A progressive larval mortality of 12% for the LC10 and 60% for the LC25 was observed before pupation. Treated larvae exhibited lower pupal weights, higher pupal mortality, presence of deformed pupae, and more deformed adults than untreated larvae. The incorporation of methoxyfenozide into the diet had a significant effect on the timing of larval development. The development period for males and females was about seven days longer than the controls for both concentrations tested. In contrast, the compound affected neither pupae nor adult longevity. Finally, S. frugiperda adults that resulted from fifth instars treated with methoxyfenozide were not affected in their mean cumulative number of eggs laid per female (fecundity), nor percentages of eggs hatched (fertility), or the sex ratio. Our results suggest that the combination of lethal and sublethal effects of methoxyfenozide may have important implications for the population dynamics of the fall armyworm
External sources of clean technology: evidence from the clean development mechanism
New technology is fundamental to sustainable development. However, inventors from industrialized countries often refuse technology transfer because they worry about reverse-engineering. When can clean technology transfer succeed? We develop a formal model of the political economy of NorthâSouth technology transfer. According to the model, technology transfer is possible if (1) the technology in focus has limited global commercial potential or (2) the host developing country does not have the capacity to absorb new technologies for commercial use. If both conditions fail, inventors from industrialized countries worry about the adverse competitiveness effects of reverse-engineering, so technology transfer fails. Data analysis of technology transfer in 4,894 projects implemented under the Kyoto Protocolâs Clean Development Mechanism during the 2004â2010 period provides evidence in support of the model
Phase-resolved optical and X-ray spectroscopy of low-mass X-ray binary X1822-371
(Abridged) X1822-371 is the prototypical accretion disc corona X-ray source,
a low-mass X-ray binary viewed at very high inclination, thereby allowing the
disc structure and extended disc coronal regions to be visible. We study the
structure of the accretion disc in X1822-371 by modelling the phase-resolved
spectra both in optical and X-ray regime. We analyse high time resolution
optical ESO/VLT spectra of X1822-371 to study the variability in the emission
line profiles. In addition, we use data from XMM-Newton space observatory to
study phase-resolved as well as high resolution X-ray spectra. We apply the
Doppler tomography technique to reconstruct a map of the optical emission
distribution in the system. We fit multi-component models to the X-ray spectra.
We find that our results from both the optical and X-ray analysis can be
explained with a model where the accretion disc has a thick rim in the region
where the accretion stream impacts the disc. The behaviour of the H_beta line
complex implies that some of the accreting matter creates an outburst around
the accretion stream impact location and that the resulting outflow of matter
moves both away from the accretion disc and towards the centre of the disc.
Such behaviour can be explained by an almost isotropic outflow of matter from
the accretion stream impact region. The optical emission lines of HeII 4686 and
5411 show double peaked profiles, typical for an accretion disc at high
inclination. However, their velocities are slower than expected for an
accretion disc in a system like X1822-371. This, combined with the fact that
the HeII emission lines do not get eclipsed during the partial eclipse in the
continuum, suggests that the line emission does not originate in the orbital
plane and is more likely to come from above the accretion disc, for example the
accretion disc wind.Comment: 10 pages, 13 figures, accepted for publication in A&
Discovery of Balmer Broad Absorption Lines in the Quasar LBQS 1206+1052
We report the discovery of Balmer broad absorption lines (BALs) in the quasar
LBQS 1206+1052 and present a detailed analysis of the peculiar absorption line
spectrum. Besides Mg II doublet, BALs are also
detected in He I* multiplet at \AA arising
from metastable helium level, and in H and H from excited
hydrogen H I* level, which are rarely seen in quasar spectra. We identify
two components in the BAL troughs of 2000 km s width: One
component shows an identical profile in H I*, \hei* and \mgii with its centroid
blueshifted by km\ s. The other component is
detected in \hei* and \mgii with km s. We
estimate the column densities of H I*, He I*, and Mg II, and compare them with
possible level population mechanisms. Our results favor the scenario that the
Balmer BALs originate in a partially ionized region with a column density of
cm for an electron density of cm via Ly resonant scattering pumping. The harsh
conditions needed may help to explain the rarity of Balmer absorption line
systems in quasar spectra. With an -band PSF magnitude of 16.50, LBQS
1206+1052 is the brightest Balmer-BAL quasar ever reported. Its high brightness
and unique spectral properties make LBQS 1206+1052 a promising candidate for
follow-up high-resolution spectroscopy, multi-band observations, and long-term
monitoring.Comment: 16 pages,4 figure
Carbonylâ β âCyclodextrin as a Novel Binder for Sulfur Composite Cathodes in Rechargeable Lithium Batteries
As one of the essential components in electrodes, the binder affects the performance of a rechargeable battery. By modifying β âcyclodextrin ( β âCD), an appropriate binder for sulfur composite cathodes is identified. Through a partial oxidation reaction in H 2 O 2 solution, β âCD is successfully modified to carbonylâ β âcyclodextrin (Câ β âCD), which exhibits a water solubility ca. 100 times that of β âCD at room temperature. Câ β âCD possesses the typical properties of an aqueous binder: strong bonding strength, high solubility in water, moderate viscosity, and wide electrochemical windows. Sulfur composite cathodes with Câ β âCD as the binder demonstrate a high reversible capacity of 694.2 mA h g (composite) â1 and 1542.7 mA h g (sulfur) â1 , with a sulfur utilization approaching 92.2%. The discharge capacity remains at 1456 mA h g (sulfur) â1 after 50 cycles, which is much higher than that of the cathode with unmodified β âCD as binder. Combined with its low cost and environmental benignity, Câ β âCD is a promising binder for sulfur cathodes in rechargeable lithium batteries with high electrochemical performance. The sulfur utilization and cycling stability of composite cathodes in rechargeable lithium batteries are enhanced by carbonylâ β âcyclodextrin (Câ β âCD) as the binder in sulfur composite cathodes. This is made possible by the fact that Câ β âCD is highly soluble in water, ca. 100 times more soluble than β âCD at room temperature, and because it exhibits strong bonding strength.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96706/1/adfm_201201847_sm_suppl.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/96706/2/1194_ftp.pd
BRICS as formation to study visual online communication? A dialogue on historical origins, perspectives on theory and future directions
In this paper, contributions from scholars working in the field of visual communication and/or online communication are gathered whose scholarly work falls into the BRICS countries realm. The interviews are framed by a brief sketch of the relevance of BRICS countries research in communication and media studies and some prospective comments on this novel field. The contributing scholars in this issue focus on China and Brazil in particular and work across the globe in Germany, the Netherlands, Austria, Switzerland, PR China, the UK and Brazil. They shared their ideas on the subject even though they are scholarly roots lie in fields as diverse as regional studies, political studies, communication and media studies and educational studies. Their thoughts were collected through email interviews and they are presented here in form of a cross-disciplinary dialogue on the issue of visual online communication in BRICS countries and the De-Westernization discourse. Gratefulness goes out to all the ones who have contributed and hopefully this project will contribute to many future dialogues between scholars from across the world
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