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| 2. |
- Garatti, A. Caratti o., et al.
(författare)
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The GRAVITY young stellar object survey: II. First spatially resolved observations of the CO bandhead emission in a high-mass YSO
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 635
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Tidskriftsartikel (refereegranskat)abstract
- Context. The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. Aims. We deploy near-infrared spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3-2.4 m). Methods. We present the first GRAVITY/VLTI observations at high spectral (R = 4000) and spatial (mas) resolution of the CO overtone transitions in NGC2024 IRS 2. Results. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases (8). Our best ellipsoid model provides a disc inclination of 34 1, a disc major axis position angle (PA) of 166 1, and a disc diameter of 3:99 0:09 mas (or 1.69 0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.740:08 0:07 mas (1.16 0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and PA matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of M 14:7 M by combining our interferometric and spectral modelling results.
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| 3. |
- Fouquet, Antoine, et al.
(författare)
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Integrative species delimitation and biogeography of the Rhinella margaritifera species group (Amphibia, Anura, Bufonidae) suggest an intense diversification throughout Amazonia during the last 10 million years
- 2024
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Ingår i: Systematics and Biodiversity. - 1477-2000. ; 22:1
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Tidskriftsartikel (refereegranskat)abstract
- The accumulation of studies delimiting species in Amazonia has not only shed light on the patterns of its outstanding species richness but also allowed a better understanding of the processes of diversification within this immense region. Nevertheless, vast knowledge gaps remain even for prominent anuran species complexes, such as the Rhinella margaritifera species group. This clade of toads comprises 23 valid species-level taxa, mainly distributed in Amazonia but also in South America’s Dry Diagonal and Atlantic and trans-Andean rainforests. Species boundaries and taxonomy in this group are notoriously complex, with studies suggesting the existence of several unnamed species. Available phylogenetic information suggests an Andean-western Amazonian origin of the group with subsequent diversification within Amazonian lowlands during the last 10 Myr and secondary dispersals into other Neotropical regions. To further test this biogeographic scenario and improve knowledge on species diversity, we used an unprecedentedly large mtDNA sampling (>800 16S sequences) across the clade’s distribution and comprising all but one described species. We delimited 54 Molecular Operational Taxonomic Units, which we tested further based on patterns of variation of a nuclear locus and acoustic and morphological data. This approach confirmed the existence of at least 25 candidate species, 19 of which correspond to currently recognized taxa whereas 30 remained ‘unconfirmed’. Our results clarify the taxonomic status of some species but also suggest multiple introgression events that blur some mtDNA-based species boundaries. Lastly, to provide a temporal framework for the clade’s diversification, we generated a time-calibrated phylogenetic tree based on a mitogenomic matrix, which confirmed a Miocene (∼9 Ma) western Amazonian origin and six major clades in the group, each having initially diversified in different regions within Amazonia. Most of these clades have later dispersed throughout Amazonia during the establishment of the modern Amazonian hydrographic system, i.e., in the last 6 Myr.
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| 4. |
- Malbet, F., et al.
(författare)
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Faint objects in motion: the new frontier of high precision astrometry
- 2021
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 51:3, s. 845-886
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Tidskriftsartikel (refereegranskat)abstract
- Sky survey telescopes and powerful targeted telescopes play complementary roles in astronomy. In order to investigate the nature and characteristics of the motions of very faint objects, a flexibly-pointed instrument capable of high astrometric accuracy is an ideal complement to current astrometric surveys and a unique tool for precision astrophysics. Such a space-based mission will push the frontier of precision astrometry from evidence of Earth-mass habitable worlds around the nearest stars, to distant Milky Way objects, and out to the Local Group of galaxies. As we enter the era of the James Webb Space Telescope and the new ground-based, adaptive-optics-enabled giant telescopes, by obtaining these high precision measurements on key objects that Gaia could not reach, a mission that focuses on high precision astrometry science can consolidate our theoretical understanding of the local Universe, enable extrapolation of physical processes to remote redshifts, and derive a much more consistent picture of cosmological evolution and the likely fate of our cosmos. Already several missions have been proposed to address the science case of faint objects in motion using high precision astrometry missions: NEAT proposed for the ESA M3 opportunity, micro-NEAT for the S1 opportunity, and Theia for the M4 and M5 opportunities. Additional new mission configurations adapted with technological innovations could be envisioned to pursue accurate measurements of these extremely small motions. The goal of this White Paper is to address the fundamental science questions that are at stake when we focus on the motions of faint sky objects and to briefly review instrumentation and mission profiles.
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| 6. |
- Knudsen, Endre, et al.
(författare)
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Challenging claims in the study of migratory birds and climate change.
- 2011
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Ingår i: Biological Reviews. - 1469-185X. ; 86, s. 928-946
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Tidskriftsartikel (refereegranskat)abstract
- Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support ('consensus view') for a claim increased and between-researcher variability in support ('expert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies.
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| 7. |
- Lopes-Oliveira, V., et al.
(författare)
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Strain and localization effects in InGaAs(N) quantum wells: Tuning the magnetic response
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 116:23
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Tidskriftsartikel (refereegranskat)abstract
- We investigated effects of localization and strain on the optical and magneto-optical properties of diluted nitrogen III-V quantum wells theoretically and experimentally. High-resolution x-ray diffraction, photoluminescence (PL), and magneto-PL measurements under high magnetic fields up to 15 T were performed at low temperatures. Bir-Pikus Hamiltonian formalism was used to study the influence of strain, confinement, and localization effects. The circularly polarized magneto-PL was interpreted considering localization aspects in the valence band ground state. An anomalous behavior of the electron-hole pair magnetic shift was observed at low magnetic fields, ascribed to the increase in the exciton reduced mass due to the negative effective mass of the valence band ground state.
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| 8. |
- O'Callaghan-Gordo, Cristina, et al.
(författare)
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Prevalence of and risk factors for chronic kidney disease of unknown aetiology in India : Secondary data analysis of three population-based cross-sectional studies
- 2019
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Ingår i: BMJ Open. - : BMJ. - 2044-6055. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Objectives To assess whether chronic kidney disease of unknown aetiology (CKDu) is present in India and to identify risk factors for it using population-based data and standardised methods. Design Secondary data analysis of three population-based cross-sectional studies conducted between 2010 and 2014. Setting Urban and rural areas of Northern India (states of Delhi and Haryana) and Southern India (states of Tamil Nadu and Andhra Pradesh). Participants 12 500 individuals without diabetes, hypertension or heavy proteinuria. Outcome measures Mean estimated glomerular filtration rate (eGFR) and prevalence of eGFR below 60 mL/min per 1.73 m 2 (eGFR <60) in individuals without diabetes, hypertension or heavy proteinuria (proxy definition of CKDu). Results The mean eGFR was 105.0±17.8 mL/min per 1.73 m 2. The prevalence of eGFR <60 was 1.6% (95% CI=1.4 to 1.7), but this figure varied markedly between areas, being highest in rural areas of Southern Indian (4.8% (3.8 to 5.8)). In Northern India, older age was the only risk factor associated with lower mean eGFR and eGFR <60 (regression coefficient (95% CI)=a '0.94 (0.97 to 0.91); OR (95% CI)=1.10 (1.08 to 1.11)). In Southern India, risk factors for lower mean eGFR and eGFR <60, respectively, were residence in a rural area (a '7.78 (-8.69 to -6.86); 4.95 (2.61 to 9.39)), older age (a '0.90 (-0.93 to -0.86); 1.06 (1.04 to 1.08)) and less education (a '0.94 (-1.32 to -0.56); 0.67 (0.50 to 0.90) for each 5 years at school). Conclusions CKDu is present in India and is not confined to Central America and Sri Lanka. Identified risk factors are consistent with risk factors previously reported for CKDu in Central America and Sri Lanka.
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| 9. |
- Prieto, E., et al.
(författare)
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Design and development of a new high entropy alloy by powder metallurgy
- 2016
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Ingår i: World Powder Metallurgy 2016 Congress and Exhibition, World PM 2016; Hamburg; Germany; 9 October 2016 through 13 October 2016. - 9781899072484
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Konferensbidrag (refereegranskat)abstract
- In this work a new high entropy alloy composition has been designed with the aim of tailoring the microstructure to achieve the required properties in cutting tools. For this purpose, it has been taken into account the characteristics of each of the elements involved, combined with the calculation of its phase diagram by thermodynamics simulations. The new composition has been developed by casting, and also by powder metallurgy. In most of the works found in the literature the powders are obtained by mechanical alloying, however in this work the powders are also obtained by atomization in order to reduce the contamination and to obtain powder particles with a more homogeneous composition. Finally the samples consolidation has been performed by spark plasma sintering.
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| 10. |
- Prieto, E., et al.
(författare)
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Processing of a new high entropy alloy: AlCrFeMoNiTi
- 2018
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Ingår i: Powder Metallurgy. - : Informa UK Limited. - 0032-5899 .- 1743-2901. ; 61:3, s. 258-265
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Tidskriftsartikel (refereegranskat)abstract
- This work, a new composition of high-entropy alloys (HEAs) was designed. The composition was carefully tailored with the aim to obtain a solid solution with a BCC crystalline structure to be an alternative binder in cermets. Thus, the composition of the HEA has been designed taking into account various criteria which has fulfilled a metallic binder of a Ti(C,N) cermet:(1) high hardness and oxidation resistance and (2) good wetting behaviour with Ti(C,N) particles because the processing of cermets is by LPS. The design of the alloy has been performed using theoretical calculations of physicochemical properties of the elements involved and the calculation of phase diagram by Thermocalc. The designed alloy has been processed by casting and powder metallurgy (PM) to study the influence of the processing route on the phases formed and on the resulting properties. The powders were produced by gas atomisation and then consolidated by hot pressing. Special theme block on high entropy alloys, guest edited by Paula Alvaredo Olmos, Universidad Carlos III de Madrid, Spain, and Sheng Guo, Chalmers University, Gothenburg, Sweden.
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