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- Kamp, I., et al.
(author)
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The formation of planetary systems with SPICA
- 2021
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In: Publications Astronomical Society of Australia. - : Cambridge University Press (CUP). - 1323-3580 .- 1448-6083. ; 38
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Journal article (peer-reviewed)abstract
- In this era of spatially resolved observations of planet-forming disks with Atacama Large Millimeter Array (ALMA) and large groundbased telescopes such as the Very Large Telescope (VLT), Keck, and Subaru, we still lack statistically relevant information on the quantity and composition of the material that is building the planets, such as the total disk gas mass, the ice content of dust, and the state of water in planetesimals. SPace Infrared telescope for Cosmology and Astrophysics (SPICA) is an infrared space mission concept developed jointly by Japan Aerospace Exploration Agency (JAXA) and European Space Agency (ESA) to address these questions. The key unique capabilities of SPICA that enable this research are (1) the wide spectral coverage 10-220 mu m, (2) the high line detection sensitivity of (1-2) x10(-19)Wm(-2) with R similar to 2 000-5 000 in the far-IR (SAFARI), and 10-20Wm(-2) with R similar to 29 000 in themid-IR (SPICA Mid-infrared Instrument (SMI), spectrally resolving line profiles), (3) the high far-IR continuum sensitivity of 0.45mJy (SAFARI), and (4) the observing efficiency for point source surveys. This paper details how mid- to far-IR infrared spectra will be unique in measuring the gas masses and water/ice content of disks and how these quantities evolve during the planet-forming period. These observations will clarify the crucial transition when disks exhaust their primordial gas and further planet formation requires secondary gas produced from planetesimals. The high spectral resolution mid-IR is also unique for determining the location of the snowline dividing the rocky and icy mass reservoirs within the disk and how the divide evolves during the build-up of planetary systems. Infrared spectroscopy (mid- to far-IR) of key solid-state bands is crucial for assessing whether extensive radial mixing, which is part of our Solar System history, is a general process occurring in most planetary systems and whether extrasolar planetesimals are similar to our Solar System comets/asteroids. We demonstrate that the SPICA mission concept would allow us to achieve the above ambitious science goals through large surveys of several hundred disks within similar to 2.5 months of observing time.
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| 3. |
- Mesa, D., et al.
(author)
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Signs of late infall and possible planet formation around DR Tau using VLT/SPHERE and LBTI/LMIRCam
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
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Journal article (peer-reviewed)abstract
- Context. Protoplanetary disks around young stars often contain substructures like rings, gaps, and spirals that could be caused by interactions between the disk and forming planets.Aims. We aim to study the young (1-3 Myr) star DR Tau in the near-infrared and characterize its disk, which was previously resolved through submillimeter interferometry with ALMA, and to search for possible substellar companions embedded into it.Methods. We observed DR Tau with VLT/SPHERE both in polarized light (H broad band) and total intensity (in Y, J, H, and K spectral bands). We also performed L' band observations with LBTI/LMIRCam on the Large Binocular Telescope (LBT). We applied differential imaging techniques to analyze both the polarized data, using dual beam polarization imaging, and the total intensity data, using angular and spectral differential imaging.Results. We found two previously undetected spirals extending north-east and south of the star, respectively. We further detected an arc-like structure north of the star. Finally a bright, compact and elongated structure was detected at a separation of 303 +/- 10 mas and a position angle 21.2 +/- 3.7 degrees, just at the root of the north-east spiral arm. Since this feature is visible both in polarized light and total intensity and has a blue spectrum, it is likely caused by stellar light scattered by dust.Conclusions. The two spiral arms are at different separations from the star, have very different pitch angles, and are separated by an apparent discontinuity, suggesting they might have a different origin. The very open southern spiral arm might be caused by infalling material from late encounters with cloudlets into the formation environment of the star itself. The compact feature could be caused by interaction with a planet in formation still embedded in its dust envelope and it could be responsible for launching the north-east spiral. We estimate a mass of the putative embedded object of the order of few M-Jup.
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- van Dishoeck, E. F., et al.
(author)
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Water in star-forming regions: Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 648
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Journal article (peer-reviewed)abstract
- Context. Water is a key molecule in the physics and chemistry of star and planet formation, but it is difficult to observe from Earth. The Herschel Space Observatory provided unprecedented sensitivity as well as spatial and spectral resolution to study water. The Water In Star-forming regions with Herschel (WISH) key program was designed to observe water in a wide range of environments and provide a legacy data set to address its physics and chemistry. Aims. The aim of WISH is to determine which physical components are traced by the gas-phase water lines observed with Herschel and to quantify the excitation conditions and water abundances in each of these components. This then provides insight into how and where the bulk of the water is formed in space and how it is transported from clouds to disks, and ultimately comets and planets. Methods. Data and results from WISH are summarized together with those from related open time programs. WISH targeted ∼80 sources along the two axes of luminosity and evolutionary stage: from low- to high-mass protostars (luminosities from <1 to > 10Lpdbl) and from pre-stellar cores to protoplanetary disks. Lines of H2O and its isotopologs, HDO, OH, CO, and [O I], were observed with the HIFI and PACS instruments, complemented by other chemically-related molecules that are probes of ultraviolet, X-ray, or grain chemistry. The analysis consists of coupling the physical structure of the sources with simple chemical networks and using non-LTE radiative transfer calculations to directly compare models and observations. Results. Most of the far-infrared water emission observed with Herschel in star-forming regions originates from warm outflowing and shocked gas at a high density and temperature (> 10cm-3, 300-1000 K, v ∼ 25 km s-1), heated by kinetic energy dissipation. This gas is not probed by single-dish low-J CO lines, but only by CO lines with Jup > 14. The emission is compact, with at least two different types of velocity components seen. Water is a significant, but not dominant, coolant of warm gas in the earliest protostellar stages. The warm gas water abundance is universally low: orders of magnitude below the H2O/H2 abundance of 4 × 10-4 expected if all volatile oxygen is locked in water. In cold pre-stellar cores and outer protostellar envelopes, the water abundance structure is uniquely probed on scales much smaller than the beam through velocity-resolved line profiles. The inferred gaseous water abundance decreases with depth into the cloud with an enhanced layer at the edge due to photodesorption of water ice. All of these conclusions hold irrespective of protostellar luminosity. For low-mass protostars, a constant gaseous HDO/H2O ratio of ∼0.025 with position into the cold envelope is found. This value is representative of the outermost photodesorbed ice layers and cold gas-phase chemistry, and much higher than that of bulk ice. In contrast, the gas-phase NH3 abundance stays constant as a function of position in low-mass pre- and protostellar cores. Water abundances in the inner hot cores are high, but with variations from 5 × 10-6 to a few × 10-4 for low- and high-mass sources. Water vapor emission from both young and mature disks is weak. Conclusions. The main chemical pathways of water at each of the star-formation stages have been identified and quantified. Low warm water abundances can be explained with shock models that include UV radiation to dissociate water and modify the shock structure. UV fields up to 102-10times the general interstellar radiation field are inferred in the outflow cavity walls on scales of the Herschel beam from various hydrides. Both high temperature chemistry and ice sputtering contribute to the gaseous water abundance at low velocities, with only gas-phase (re-)formation producing water at high velocities. Combined analyses of water gas and ice show that up to 50% of the oxygen budget may be missing. In cold clouds, an elegant solution is that this apparently missing oxygen is locked up in larger μm-sized grains that do not contribute to infrared ice absorption. The fact that even warm outflows and hot cores do not show H2O at full oxygen abundance points to an unidentified refractory component, which is also found in diffuse clouds. The weak water vapor emission from disks indicates that water ice is locked up in larger pebbles early on in the embedded Class I stage and that these pebbles have settled and drifted inward by the Class II stage. Water is transported from clouds to disks mostly as ice, with no evidence for strong accretion shocks. Even at abundances that are somewhat lower than expected, many oceans of water are likely present in planet-forming regions. Based on the lessons for galactic protostars, the low-J H2O line emission (Eup < 300 K) observed in extragalactic sources is inferred to be predominantly collisionally excited and to originate mostly from compact regions of current star formation activity. Recommendations for future mid- to far-infrared missions are made.
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- Allanach, Benjamin C., et al.
(author)
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Simple and statistically sound strategies for analysing physical theories
- 2022
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In: Reports on progress in physics (Print). - : Institute of Physics Publishing (IOPP). - 0034-4885 .- 1361-6633. ; 85:5
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Research review (peer-reviewed)abstract
- Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at Zenodo.
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| 6. |
- Papp, Zoltan, et al.
(author)
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Levosimendan Efficacy and Safety : 20 Years of SIMDAX in Clinical Use
- 2020
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In: Journal of Cardiovascular Pharmacology. - : Ovid Technologies (Wolters Kluwer Health). - 0160-2446 .- 1533-4023. ; 76:1, s. 4-22
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Journal article (peer-reviewed)abstract
- Levosimendan was first approved for clinical use in 2000, when authorization was granted by Swedish regulatory authorities for the hemodynamic stabilization of patients with acutely decompensated chronic heart failure (HF). In the ensuing 20 years, this distinctive inodilator, which enhances cardiac contractility through calcium sensitization and promotes vasodilatation through the opening of adenosine triphosphate-dependent potassium channels on vascular smooth muscle cells, has been approved in more than 60 jurisdictions, including most of the countries of the European Union and Latin America. Areas of clinical application have expanded considerably and now include cardiogenic shock, takotsubo cardiomyopathy, advanced HF, right ventricular failure, pulmonary hypertension, cardiac surgery, critical care, and emergency medicine. Levosimendan is currently in active clinical evaluation in the United States. Levosimendan in IV formulation is being used as a research tool in the exploration of a wide range of cardiac and noncardiac disease states. A levosimendan oral form is at present under evaluation in the management of amyotrophic lateral sclerosis. To mark the 20 years since the advent of levosimendan in clinical use, 51 experts from 23 European countries (Austria, Belgium, Croatia, Cyprus, Czech Republic, Estonia, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Russia, Slovenia, Spain, Sweden, Switzerland, the United Kingdom, and Ukraine) contributed to this essay, which evaluates one of the relatively few drugs to have been successfully introduced into the acute HF arena in recent times and charts a possible development trajectory for the next 20 years.
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| 7. |
- Tabanera-Bravo, Jorge, et al.
(author)
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Stability of long-sustained oscillations induced by electron tunneling
- 2024
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In: Physical Review Research. - 2643-1564. ; 6:1
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Journal article (peer-reviewed)abstract
- Self-oscillations are the result of an efficient mechanism generating periodic motion from a constant power source. In quantum devices, these oscillations may arise due to the interaction between single electron dynamics and mechanical motion. We show that, due to the complexity of this mechanism, these self-oscillations may irrupt, vanish, or exhibit a bistable behavior causing hysteresis cycles. We observe these hysteresis cycles and characterize the stability of different regimes in both single- and double-quantum-dot configurations. In particular cases, we find these oscillations stable for over 20 s, many orders of magnitude above electronic and mechanical characteristic timescales, revealing the robustness of the mechanism at play.
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| 9. |
- Vigneau, Florian, et al.
(author)
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Ultrastrong coupling between electron tunneling and mechanical motion
- 2022
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In: Physical Review Research. - 2643-1564. ; 4:4
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Journal article (peer-reviewed)abstract
- The ultrastrong coupling of single-electron tunneling and nanomechanical motion opens exciting opportunities to explore fundamental questions and develop new platforms for quantum technologies. We have measured and modeled this electromechanical coupling in a fully suspended carbon nanotube device and report a ratio of gm/ωm=2.72±0.14, where gm/2π=0.80±0.04GHz is the coupling strength and ωm/2π=294.5MHz is the mechanical resonance frequency. This is well within the ultrastrong coupling regime and the highest among all other electromechanical platforms. We show that, although this regime was present in similar fully suspended carbon nanotube devices, it went unnoticed. Even higher ratios could be achieved with improvement on device design.
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