| 1. |
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| 2. |
- Caselli, P., et al.
(författare)
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Water vapor toward starless cores : The Herschel view
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521, s. L29-
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Previous studies by the satellites SWAS and Odin provided stringent upper limits on the gas phase water abundance of dark clouds (x(H2O) < 7 × 10-9). We investigate the chemistry of water vapor in starless cores beyond the previous upper limits using the highly improved angular resolution and sensitivity of Herschel and measure the abundance of water vapor during evolutionary stages just preceding star formation. Methods: High spectral resolution observations of the fundamental ortho water (o-H2O) transition (557 GHz) were carried out with the Heterodyne Instrument for the Far Infrared onboard Herschel toward two starless cores: Barnard 68 (hereafter B68), a Bok globule, and LDN 1544 (L1544), a prestellar core embedded in the Taurus molecular cloud complex. Detailed radiative transfer and chemical codes were used to analyze the data. Results: The RMS in the brightness temperature measured for the B68 and L1544 spectra is 2.0 and 2.2 mK, respectively, in a velocity bin of 0.59 km s-1. The continuum level is 3.5 ± 0.2 mK in B68 and 11.4 ± 0.4 mK in L1544. No significant feature is detected in B68 and the 3σ upper limit is consistent with a column density of o-H2O N(o-H2O) < 2.5 × 1013 cm-2, or a fractional abundance x(o-H2O) < 1.3 × 10-9, more than an order of magnitude lower than the SWAS upper limit on this source. The L1544 spectrum shows an absorption feature at a 5σ level from which we obtain the first value of the o-H2O column density ever measured in dark clouds: N(o-H2O) = (8 ± 4) × 1012 cm-2. The corresponding fractional abundance is x(o-H2O) ≃ 5 × 10-9 at radii >7000 AU and ≃2 × 10-10 toward the center. The radiative transfer analysis shows that this is consistent with a x(o-H2O) profile peaking at ≃10-8, 0.1 pc away from the core center, where both freeze-out and photodissociation are negligible. Conclusions: Herschel has provided the first measurement of water vapor in dark regions. Column densities of o-H2O are low, but prestellar cores such as L1544 (with their high central densities, strong continuum, and large envelopes) appear to be very promising tools to finally shed light on the solid/vapor balance of water in molecular clouds and oxygen chemistry in the earliest stages of star formation. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
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| 3. |
- van Dishoeck, E. F., et al.
(författare)
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Water in Star-forming Regions with the Herschel Space Observatory (WISH). I. Overview of Key Program and First Results
- 2011
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 123:900, s. 138-170
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Tidskriftsartikel (refereegranskat)abstract
- Water In Star-forming regions with Herschel (WISH) is a key program on the Herschel Space Observatory designed to probe the physical and chemical structures of young stellar objects using water and related molecules and to follow the water abundance from collapsing clouds to planet-forming disks. About 80 sources are targeted, covering a wide ranee of luminosities-from low ( 10(5) L-circle dot)-and a wide range of evolutionary stages-from cold prestellar cores to warm protostellar envelopes and outflows to disks around young stars. Both the HIFI and PACS instruments are used to observe a variety of lines of H2O, (H2O)-O-18 and chemically related species at the source position and in small maps around the protostars and selected outflow positions. In addition, high-frequency lines of CO, (CO)-C-13, and (CO)-O-18 are obtained with Herschel and are complemented by ground-based observations of dust continuum, HDO, CO and its isotopologs, and other molecules to ensure a self-consistent data set for analysis. An overview of the scientific motivation and observational strategy of the program is given, together with the modeling approach and analysis tools that have been developed. Initial science results are presented. These include a lack of water in cold gas at abundances that are lower than most predictions, strong water emission from shocks in protostellar environments, the importance of UV radiation in heating the gas along outflow walls across the full range of luminosities, and surprisingly widespread detection of the chemically related hydrides OH+ and H2O+ in outflows and foreground gas. Quantitative estimates of the energy budget indicate that H2O is generally not the dominant coolant in the warm dense gas associated with protostars. Very deep limits on the cold gaseous water reservoir in the outer regions of protoplanetary disks are obtained that have profound implications for our understanding of grain growth and mixing in disks.
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| 4. |
- Kamp, I., et al.
(författare)
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The formation of planetary systems with SPICA
- 2021
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Ingår i: Publications Astronomical Society of Australia. - : Cambridge University Press (CUP). - 1323-3580 .- 1448-6083. ; 38
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Kalra, Hina, et al.
(författare)
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Vesiclepedia : a compendium for extracellular vesicles with continuous community annotation
- 2012
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Ingår i: PLoS biology. - : Public library of science. - 1544-9173 .- 1545-7885. ; 10:12, s. e1001450-
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular vesicles (EVs) are membraneous vesicles released by a variety of cells into their microenvironment. Recent studies have elucidated the role of EVs in intercellular communication, pathogenesis, drug, vaccine and gene-vector delivery, and as possible reservoirs of biomarkers. These findings have generated immense interest, along with an exponential increase in molecular data pertaining to EVs. Here, we describe Vesiclepedia, a manually curated compendium of molecular data (lipid, RNA, and protein) identified in different classes of EVs from more than 300 independent studies published over the past several years. Even though databases are indispensable resources for the scientific community, recent studies have shown that more than 50% of the databases are not regularly updated. In addition, more than 20% of the database links are inactive. To prevent such database and link decay, we have initiated a continuous community annotation project with the active involvement of EV researchers. The EV research community can set a gold standard in data sharing with Vesiclepedia, which could evolve as a primary resource for the field.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Asano, H., et al.
(författare)
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Spectroscopic study of the Λ(1405) resonance via the d (K-, n) reaction at J-PARC
- 2019
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Ingår i: 13th International Conference on Hypernuclear and Strange Particle Physics, HYP 2018. - : AIP Publishing. - 9780735418721 ; 2130
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Konferensbidrag (refereegranskat)abstract
- The structure of the Λ(1405) hyperon is an important and long-standing issue related to the K̄-nucleus interaction. The J-PARC E31 experiment has been performed to investigate the Λ(1405) spectrum shape. Because it is hard to form the Λ(1405) directly by a K̄N scattering in free space, E31 uses the d(K-, n) reaction with an incident kaon momentum of 1 GeV/c. We will identify three final states - ς-π+, ς+π-, ς0π0-so that the isospin structure of hyperon resonance states produced can be decomposed. The first physics run of the E31 experiment was performed in 2016. To enhance the statistics of the data set, we have performed the second physics run in the beginning of 2018. During the second run of E31, around 3.9×1010 kaons impacted on the deuteron target.
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| 11. |
- Cataldi, Gianni, et al.
(författare)
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Primordial or Secondary? Testing Models of Debris Disk Gas with ALMA*
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 951:2
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Tidskriftsartikel (refereegranskat)abstract
- The origin and evolution of gas in debris disks are still not well understood. Secondary gas production from cometary material or a primordial origin have been proposed. So far, observations have mostly concentrated on CO, with only a few C observations available. We overview the C and CO content of debris disk gas and test state-of-the-art models. We use new and archival Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO and C i emission, complemented by C ii data from Herschel, for a sample of 14 debris disks. This expands the number of disks with ALMA measurements of both CO and C i by 10 disks. We present new detections of C i emission toward three disks: HD 21997, HD 121191, and HD 121617. We use a simple disk model to derive gas masses and column densities. We find that current state-of-the-art models of secondary gas production overpredict the C-0 content of debris disk gas. This does not rule out a secondary origin, but might indicate that the models require an additional C removal process. Alternatively, the gas might be produced in transient events rather than a steady-state collisional cascade. We also test a primordial gas origin by comparing our results to a simplified thermochemical model. This yields promising results, but more detailed work is required before a conclusion can be reached. Our work demonstrates that the combination of C and CO data is a powerful tool to advance our understanding of debris disk gas.
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| 12. |
- Jorgensen, A. A., et al.
(författare)
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Petabit-per-second data transmission using a chip-scale microcomb ring resonator source
- 2022
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 16:11, s. 798-802
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Tidskriftsartikel (refereegranskat)abstract
- Optical fibre communication is the backbone of the internet. As essential core technologies are approaching their limits of size, speed and energy-efficiency, there is a need for new technologies that offer further scaling of data transmission capacity. Here we show that a single optical frequency-comb source based on a silicon nitride ring resonator supports data capacities in the petabit-per-second regime. We experimentally demonstrate transmission of 1.84 Pbit s–1 over a 37-core, 7.9-km-long fibre using 223 wavelength channels derived from a single microcomb ring resonator producing a stabilized dark-pulse Kerr frequency comb. We also present a theoretical analysis that indicates that a single, chip-scale light source should be able to support 100 Pbit s–1 in massively parallel space-and-wavelength multiplexed data transmission systems. Our findings could mark a shift in the design of future communication systems, targeting device-efficient transmitters and receivers.
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| 13. |
- Kim, Dae-Kyum, et al.
(författare)
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EVpedia: A Community Web Portal for Extracellular Vesicles Research
- 2015
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Ingår i: Bioinformatics. - : Oxford University Press (OUP). - 1367-4803 .- 1367-4811. ; 31:6, s. 933-939
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Tidskriftsartikel (refereegranskat)abstract
- Motivation: Extracellular vesicles (EVs) are spherical bilayered proteolipids, harboring various bioactive molecules. Due to the complexity of the vesicular nomenclatures and components, online searches for EV-related publications and vesicular components are currently challenging. Results: We present an improved version of EVpedia, a public database for EVs research. This community web portal contains a database of publications and vesicular components, identification of orthologous vesicular components, bioinformatic tools and a personalized function. EVpedia includes 6879 publications, 172 080 vesicular components from 263 high-throughput datasets, and has been accessed more than 65 000 times from more than 750 cities. In addition, about 350 members from 73 international research groups have participated in developing EVpedia. This free web-based database might serve as a useful resource to stimulate the emerging field of EV research.
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| 14. |
- Kong, D., et al.
(författare)
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Single Dark-Pulse Kerr Comb Supporting 1.84 Pbit/s Transmission over 37-Core Fiber
- 2020
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Ingår i: Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS. - 1092-8081. ; 2020-May
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Konferensbidrag (refereegranskat)abstract
- We show that a single dark-pulse Kerr comb can generate high enough OSNR to carry 1.84 Pbit/s data, achieved by 223 WDM spectral lines modulated with 32-Gbaud, SNR-adapted probabilistically shaped DP-QAM, over a 37-core fiber.
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| 15. |
- van Dishoeck, E. F., et al.
(författare)
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Triennial Report, International Astronomical Union, Division VI/Commission 34/Working Group Astrochemistry
- 2012
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 7:Transactions T28A, s. 236-239
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The study of molecules in space, known as astrochemistry or molecular astrophysics, is a rapidly growing field. Molecules exist in a wide range of environments in both gaseous and solid form, from our own solar system to the distant early universe. To astronomers, molecules are indispensable and unique probes of the physical conditions and dynamics of regions in which they are detected, especially the interstellar medium. In particular, the many stages of both low-mass and high-mass star formation are better understood today thanks to the analysis of molecular observations. Molecules can also yield a global picture of the past and present of sources. Moreover, molecules affect their environment by contributing to the heating and cooling processes that occur.
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