| 1. |
- Anderberg, C., et al.
(author)
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Deficiency for endoglin in tumor vasculature weakens the endothelial barrier to metastatic dissemination
- 2013
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In: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 210:3, s. 563-579
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Journal article (peer-reviewed)abstract
- Therapy-induced resistance remains a significant hurdle to achieve long-lasting responses and cures in cancer patients. We investigated the long-term consequences of genetically impaired angiogenesis by engineering multiple tumor models deprived of endoglin, a co-receptor for TGF-β in endothelial cells actively engaged in angiogenesis. Tumors from endoglin-deficient mice adapted to the weakened angiogenic response, and refractoriness to diminished endoglin signaling was accompanied by increased metastatic capability. Mechanistic studies in multiple mouse models of cancer revealed that deficiency for endoglin resulted in a tumor vasculature that displayed hallmarks of endothelial-to-mesenchymal transition, a process of previously unknown significance in cancer biology, but shown by us to be associated with a reduced capacity of the vasculature to avert tumor cell intra- and extravasation. Nevertheless, tumors deprived of endoglin exhibited a delayed onset of resistance to anti-VEGF (vascular endothelial growth factor) agents, illustrating the therapeutic utility of combinatorial targeting of multiple angiogenic pathways for the treatment of cancer.
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| 2. |
- Biver, N., et al.
(author)
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Coma composition of comet 67P/Churyumov-Gerasimenko from radio-wave spectroscopy
- 2023
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 672
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Journal article (peer-reviewed)abstract
- We present the results of a molecular survey of comet 67P/Churyumov-Gerasimenko undertaken with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m radio telescope in November–December 2021, when it had its most favourable apparition in decades. Observations at IRAM 30-m during the 12–16 November period covered 8 GHz bandwidth at 3 mm, 16 GHz at 2 mm, and 60 GHz in the 1 mm window domain. These were completed by snapshots at 1 mm on 12–13 December and a short observation of the H2O line at 557 GHz with the Odin sub-millimetre observatory on 17.0 November 2021, and with 18-cm observations of OH with the Nançay radio telescope. Less sensitive observations obtained at a previous perihelion passage on 18–22 September 2015 with IRAM and 9–12 November 2015 with Odin are also presented. The gas outflow velocity, outgassing pattern, and temperature have been accurately constrained by the observations. They are perfectly consistent with those measured in situ with the Rosetta/MIRO sub-millimetre instrument in 2015. In particular, the asymmetry of the line is well represented by a jet concentrating three-quarters of the outgassing in about π steradians. We derived abundances relative to water for seven molecules and significant upper limits for approximately five others. The retrieved abundances were compared to those measured in situ at the previous perihelion with Rosetta. While those of HCN, CH3OH, and HNCO are comparable, 67P is found to be depleted in H2S and relatively normal in CS (H2S/CS ≈ 3) in strong contradiction with the Rosetta/ROSINA mass spectrometer measurement of the H2S/CS2 (≈100) abundance ratio. While the formaldehyde total abundance found with IRAM 30-m when assuming it to be mostly produced by a distributed source (Haser parent scale length ≈8000 km) is similar to the one derived by Rosetta/ROSINA, we find that the formaldehyde coming from the nucleus is one order of magnitude less abundant than measured in situ by Rosetta/ROSINA.
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| 3. |
- Unnikrishnan Nair, Ramlal, 1997, et al.
(author)
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Charting circumstellar chemistry of carbon-rich asymptotic giant branch stars: I. ALMA 3 mm spectral surveys
- 2024
-
In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 684
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Journal article (peer-reviewed)abstract
- Context. Asymptotic giant branch (AGB) stars are major contributors to the chemical enrichment of the interstellar medium through nucleosynthesis and extensive mass loss. Direct measures of both processes can be obtained by studying their circumstellar envelopes in molecular line emission. Most of our current knowledge of circumstellar chemistry, in particular in a C-rich environment, is based on observations of the carbon star IRC +10216. Aims. We aim to obtain a more generalised understanding of the chemistry in C-rich AGB circumstellar envelopes by studying a sample of three carbon stars, IRAS 15194-5115, IRAS 15082-4808, and IRAS 07454-7112, and to observationally test the archetypal status often attributed to IRC +10216. Methods. We performed spatially resolved, unbiased spectral surveys in ALMA Band 3 (85-116 GHz). We estimated the sizes of the molecular emitting regions using azimuthally averaged radial profiles of the line brightness distributions. We derived abundance estimates, using a population diagram analysis for molecules with multiple detected lines, and using single-line analytical calculations for the others. Results. We identify a total of 132 rotational transitions from 49 molecular species. There are two main morphologies of the brightness distributions: centrally peaked (CS, SiO, SiS, HCN) and shell-like (CN, HNC, C2H, C3H, C4H, C3N, HC5N, c-C3H2). The brightness distributions of HC3N and SiC2 have both a central and a shell component. The qualitative behaviour of the brightness distributions of all detected molecules, in particular their relative locations with respect to the central star, is the same for all three stars, and consistent with those observed towards IRC +10216. Of the shell distributions, the cyanopolyynes peak at slightly smaller radii than the hydrocarbons, and CN and HNC show the most extended emission. The emitting regions for each species are the smallest for IRAS 07454-7112, consistent with this object having the lowest circumstellar density within our sample. We find that, within the uncertainties of the analysis, the three stars present similar abundances for most species, and also compared to IRC +10216. We find, tentatively, that SiO is more abundant in our three stars compared to IRC+10216, and that the hydrocarbons are under-abundant in IRAS 07454-7112 compared to the other stars and IRC +10216. Our estimated 12C/13C ratios match well the literature values for the three sources and our estimated silicon and sulphur isotopic ratios are very similar across the three stars and IRC +10216. Conclusions. The observed circumstellar chemistry appears very similar across our sample and compared to that of IRC +10216, both in terms of the relative location of the emitting regions and molecular abundances. This implies that, to a first approximation, the chemical models tailored to IRC +10216 are, at least, able to reproduce the observed chemistry in C-rich envelopes across roughly an order of magnitude in wind density.
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| 4. |
- Cordiner, M. A., et al.
(author)
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On the Nature of the Enigmatic Object IRAS 19312+1950: A Rare Phase of Massive Star Formation?
- 2016
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In: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 828:1
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Journal article (peer-reviewed)abstract
- IRAS 19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS 19312+1950 in the range 5–550 μm using the Herschel and Spitzer space observatories. The Herschel PACS maps exhibit a compact, slightly asymmetric continuum source at 170 μm, indicative of a large, dusty circumstellar envelope. The far-IR CO emission line spectrum reveals two gas temperature components: ≈0.22 solar masses of material at 280 ± 18 K, and ≈1.6 solar masses of material at 157 ± 3 K. The O i 63 μm line is detected on-source but no significant emission from atomic ions was found. The HIFI observations display shocked, high-velocity gas with outflow speeds up to 90 km/s along the line of sight. From Spitzer spectroscopy, we identify ice absorption bands due to H2O at 5.8 μm and CO2 at 15 μm. The spectral energy distribution is consistent with a massive, luminous (~2 × 10^4 solar luminosities) central source surrounded by a dense, warm circumstellar disk and envelope of total mass ~500–700 solar masses, with large bipolar outflow cavities. The combination of distinctive far-IR spectral features suggest that IRAS 19312+1950 should be classified as an accreting, high-mass YSO rather than an evolved star. In light of this reclassification, IRAS 19312+1950 becomes only the fifth high-mass protostar known to exhibit SiO maser activity, and demonstrates that 18 cm OH maser line ratios may not be reliable observational discriminators between evolved stars and YSOs.
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| 5. |
- Cordiner, M. A., et al.
(author)
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On the ubiquity of molecular anions in the dense interstellar medium
- 2013
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In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 770:1
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Journal article (peer-reviewed)abstract
- Results are presented from a survey for molecular anions in seven nearby Galactic star-forming cores and molecular clouds. The hydrocarbon anion C6H- is detected in all seven target sources, including four sources where no anions have been previously detected: L1172, L1389, L1495B, and TMC-1C. The C6H-/C6H column density ratio is greater than or similar to 1.0% in every source, with a mean value of 3.0% (and standard deviation 0.92%). Combined with previous detections, our results show that anions are ubiquitous in dense clouds wherever C6H is present. The C6H-/C6H ratio is found to show a positive correlation with molecular hydrogen number density, and with the apparent age of the cloud. We also report the first detection of C4H- in TMC-1 (at 4.8 sigma confidence), and derive an anion-to-neutral ratio C4H-/C4H = (1.2 +/- 0.4) x 10(-5)(= 0.0012% +/- 0.0004%). Such a low value compared with C6H- highlights the need for a revised radiative electron attachment rate for C4H. Chemical model calculations show that the observed C4H- could be produced as a result of reactions of oxygen atoms with C5H- and C6H-.
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| 6. |
- Cordiner, M. A., et al.
(author)
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Organic chemistry of low-mass star-forming cores I: 7 mm spectroscopy of Chamaeleon MMS1
- 2012
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In: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 744, s. 131-
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Journal article (peer-reviewed)abstract
- Observations are presented of emission lines from organic molecules at frequencies 32-50 GHz in the vicinity of Chamaeleon MMS1. This chemically rich dense cloud core harbors an extremely young, very low luminosity protostellar object and is a candidate first hydrostatic core. Column densities are derived and emission maps are presented for species including polyynes, cyanopolyynes, sulphuretted carbon chains, and methanol. The polyyne emission peak lies about 5000 AU from the protostar, whereas methanol peaks about 15,000 AU away. Averaged over the telescope beam, the molecular hydrogen number density is calculated to be 106 cm–3 and the gas kinetic temperature is in the range 5-7 K. The abundances of long carbon chains are very large and are indicative of a non-equilibrium carbon chemistry; C6H and HC7N column densities are 5.9+2.9 –1.3 × 1011 cm–2 and 3.3+8.0 –1.5 × 1012 cm–2, respectively, which are similar to the values found in the most carbon-chain-rich protostars and prestellar cores known, and are unusually large for star-forming gas. Column density upper limits were obtained for the carbon-chain anions C4H– and C6H–, with anion-to-neutral ratios [C4H–]/[C4H]
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| 7. |
- Desai, R. T., et al.
(author)
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Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan's Ionosphere
- 2017
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In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 844:2
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Journal article (peer-reviewed)abstract
- Cassini discovered a plethora of neutral and ionized molecules in Titan's ionosphere including, surprisingly, anions and negatively charged molecules extending up to 13,800 u q-1. In this Letter, we forward model the Cassini electron spectrometer response function to this unexpected ionospheric component to achieve an increased mass resolving capability for negatively charged species observed at Titan altitudes of 950-1300 km. We report on detections consistently centered between 25.8 and 26.0 u q-1 and between 49.0-50.1 u q(-1) which are identified as belonging to the carbon chain anions, CN-/C3N- and/or C2H-/C4H-, in agreement with chemical model predictions. At higher ionospheric altitudes, detections at 73-74 u q-1 could be attributed to the further carbon chain anions C5N-/C6H- but at lower altitudes and during further encounters extend over a higher mass/charge range. This, as well as further intermediary anions detected at > 100 u, provide the first evidence for efficient anion chemistry in space involving structures other than linear chains. Furthermore, at altitudes below < 1100 km, the low-mass anions (< 150 u q-1) were found to deplete at a rate proportional to the growth of the larger molecules, a correlation that indicates the anions are tightly coupled to the growth process. This study adds Titan to an increasing list of astrophysical environments where chain anions have been observed and shows that anion chemistry plays a role in the formation of complex organics within a planetary atmosphere as well as in the interstellar medium.
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| 8. |
- Lindberg, Johan E., et al.
(author)
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EXTERNALLY HEATED PROTOSTELLAR CORES in the OPHIUCHUS STAR-FORMING REGION
- 2017
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In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 835:1, s. 3-
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Journal article (peer-reviewed)abstract
- We present APEX 218 GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H2CO and c-C3H2 rotational temperatures, both of which are good tracers of the kinetic temperature of the molecular gas. We find that the H2CO temperatures range between 16 K and 124 K, with the highest H2CO temperatures toward the hot corino source IRAS 16293-2422 (69-124 K) and the sources in the ? Oph A cloud (23-49 K) located close to the luminous Herbig Be star S1, which externally irradiates the ? Oph A cores. On the other hand, the c-C3H2 rotational temperature is consistently low (7-17 K) in all sources. Our results indicate that the c-C3H2 emission is primarily tracing more shielded parts of the envelope whereas the H2CO emission (at the angular scale of the APEX beam; 3600 au in Ophiuchus) mainly traces the outer irradiated envelopes, apart from in IRAS 16293-2422, where the hot corino emission dominates. In some sources, a secondary velocity component is also seen, possibly tracing the molecular outflow.
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| 9. |
- Linnartz, H., et al.
(author)
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C-60(+) as a diffuse interstellar band carrier; a spectroscopic story in 6 acts
- 2020
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In: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852 .- 1096-083X. ; 367
-
Journal article (peer-reviewed)abstract
- In 2019 it was exactly 100 years ago that the first two DIBs, diffuse interstellar bands, were discovered by Mary Lea Heger. Today some 500 + DIBs are known. In numerous observational, modelling and laboratory studies, efforts have been made to identify the carriers of these absorption features that are observed in the light of reddened stars crossing diffuse and translucent clouds. Despite several claims over the years that specific DIBs could be assigned to specific species, not one of these withstood dedicated follow-up studies. An exception is C-60(+). In 2015, Campbell et al. showed that two strong bands, recorded in the laboratory around 960 nm, coincided precisely with known DIBs and in follow-up studies three more matches between C-60(+) transitions and new observational DIB studies were claimed. Over the last four years the evidence for C-60(+) as the first identified DIB carrier - including new laboratory data and Hubble Space Telescope observations - has been accumulating, but not all open issues have been solved yet. This article summarizes 6 spectroscopic achievements that sequentially contributed to what seems to become the first DIB story with a happy end.
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| 10. |
- Patat, F., et al.
(author)
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Multi epoch high resolution spectroscopy of sn 2011fe linking the progenitor to its environment
- 2013
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 549, s. A62-
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Journal article (peer-reviewed)abstract
- Aims. The nearby Type Ia supernova (SN) 2011fe has provided an unprecedented opportunity for deriving some of the properties of its progenitor. This work provides additional and independent information on the circumstellar environment in which the explosion took place. Methods. We obtained high-resolution spectroscopy of SN 2011fe for 12 epochs, from 8 to 86 days after the estimated date of explosion, testing in particular the time evolution of Ca II and Na I. Results. Three main absorption systems are identified from Ca II and Na I, one associated to the Milky Way, one probably arising within a high-velocity cloud, and one most likely associated to the halo of M101. The total (Galactic and host galaxy) reddening, deduced from the integrated equivalent widths (EW) of the Na I lines, is EB-V less than or similar to 0.05 mag. The host galaxy absorption is dominated by a component detected at the same velocity measured from the 21-cm H 1 line at the projected SN position (similar to 180 km s(-1)). During the similar to 3 months covered by our observations its EW peak-to-peak variation is 15.6 +/- 6.5 m angstrom. This small and marginally significant change is shown to be compatible with the geometric effects produced by the rapid SN photosphere expansion coupled to the patchy fractal structure of the interstellar medium (ISM). The observed behavior is fully consistent with ISM properties similar to those derived for our own Galaxy, with evidences for structures on scales less than or similar to 100 AU. Conclusions. SN 2011fe appears to be surrounded by a clean environment. The lack of blueshifted, time-variable absorption features is fully consistent with the progenitor being a binary system with a main-sequence, or even another degenerate star.
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