| 1. |
- Kankare, E., et al.
(author)
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Search for transient optical counterparts to high-energy IceCube neutrinos with Pan-STARRS1
- 2019
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 626
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Journal article (peer-reviewed)abstract
- In order to identify the sources of the observed diffuse high-energy neutrino flux, it is crucial to discover their electromagnetic counterparts. To increase the sensitivity of detecting counterparts of transient or variable sources by telescopes with a limited field of view, IceCube began releasing alerts for single high-energy (E-v > 60 TeV) neutrino detections with sky localisation regions of order 1 degrees radius in 2016. We used Pan-STARRS1 to follow-up five of these alerts during 2016-2017 to search for any optical transients that may be related to the neutrinos. Typically 10-20 faint m(ip1) less than or similar to 22.5 mag) extragalactic transients are found within the Pan-STARRS1 footprints and are generally consistent with being unrelated field supernovae (SNe) and AGN. We looked for unusual properties of the detected transients, such as temporal coincidence of explosion epoch with the IceCube timestamp, or other peculiar light curve and physical properties. We found only one transient that had properties worthy of a specific follow-up. In the Pan-STARRS1 imaging for IceCube-160427A (probability to be of astrophysical origin of similar to 50%), we found a SN PS16cgx, located at 10.0' from the nominal IceCube direction. Spectroscopic observations of PS16cgx showed that it was an H-poor SN at redshift z = 0.2895 +/- 0.0001. The spectra and light curve resemble some high-energy Type Ic SNe, raising the possibility of a jet driven SN with an explosion epoch temporally coincident with the neutrino detection. However, distinguishing Type Ia and Type Ic SNe at this redshift is notoriously difficult. Based on all available data we conclude that the transient is more likely to be a Type Ia with relatively weak Sin absorption and a fairly normal rest-frame r-band light curve. If, as predicted, there is no high-energy neutrino emission from Type Ia SNe, then PS16cgx must be a random coincidence, and unrelated to the IceCube-160427A. We find no other plausible optical transient for any of the five IceCube events observed down to a 5 sigma limiting magnitude of mip1 approximate to 22 mag, between 1 day and 25 days after detection.
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| 2. |
- Smartt, S. J., et al.
(author)
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A kilonova as the electromagnetic counterpart to a gravitational-wave source
- 2017
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 551:7678, s. 75-
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Journal article (peer-reviewed)abstract
- Gravitational waves were discovered with the detection of binary black-hole mergers(1) and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova(2-5). The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate(6). Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short.-ray burst(7,8). The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 +/- 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 +/- 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 +/- 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.
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| 3. |
- Smartt, S. J., et al.
(author)
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Pan-STARRS and PESSTO search for an optical counterpart to the LIGO gravitational-wave source GW150914
- 2016
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 462:4, s. 4094-4116
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Journal article (peer-reviewed)abstract
- We searched for an optical counterpart to the first gravitational-wave source discovered by LIGO (GW150914), using a combination of the Pan-STARRS1 wide-field telescope and the Public ESO Spectroscopic Survey of Transient Objects (PESSTO) spectroscopic follow-up programme. As the final LIGO sky maps changed during analysis, the total probability of the source being spatially coincident with our fields was finally only 4.2 per cent. Therefore, we discuss our results primarily as a demonstration of the survey capability of Pan-STARRS and spectroscopic capability of PESSTO. We mapped out 442 deg(2) of the northern sky region of the initial map. We discovered 56 astrophysical transients over a period of 41 d from the discovery of the source. Of these, 19 were spectroscopically classified and a further 13 have host galaxy redshifts. All transients appear to be fairly normal supernovae (SNe) and AGN variability and none is obviously linked with GW150914. We illustrate the sensitivity of our survey by defining parametrized light curves with time-scales of 4, 20 and 40 d and use the sensitivity of the Pan-STARRS1 images to set limits on the luminosities of possible sources. The Pan-STARRS1 images reach limiting magnitudes of iP1 = 19.2, 20.0 and 20.8, respectively, for the three time-scales. For long time-scale parametrized light curves (with full width half-maximum similar or equal to 40 d), we set upper limits of M-i <= -17.2(+1.4)(-0.9) if the distance to GW150914 is D-L = 400 +/- 200 Mpc. The number of Type Ia SN we find in the survey is similar to that expected from the cosmic SN rate, indicating a reasonably complete efficiency in recovering SN like transients out to D-L = 400 +/- 200 Mpc.
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| 4. |
- Smartt, S. J., et al.
(author)
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A SEARCH FOR AN OPTICAL COUNTERPART TO THE GRAVITATIONAL-WAVE EVENT GW151226
- 2016
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In: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 827:2
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Journal article (peer-reviewed)abstract
- We present a search for an electromagnetic counterpart of the gravitational-wave source GW151226. Using the Pan-STARRS1 telescope we mapped out 290 square degrees in the optical i(P1) filter, starting 11.5 hr after the LIGO information release and lasting for an additional 28 days. The first observations started 49.5 hr after the time of the GW151226 detection. We typically reached sensitivity limits of i(P1) = 20.3-20.8 and covered 26.5% of the LIGO probability skymap. We supplemented this with ATLAS survey data, reaching 31% of the probability region to shallower depths of m similar or equal to 19. We found 49 extragalactic transients (that are not obviously active galactic nuclei), including a faint transient in a galaxy at 7 Mpc (a luminous blue variable outburst) plus a rapidly decaying M-dwarf flare. Spectral classification of 20 other transient events showed them all to be supernovae. We found an unusual transient, PS15dpn, with an explosion date temporally coincident with GW151226, that evolved into a type Ibn supernova. The redshift of the transient is secure at z = 0.1747 +/- 0.0001 and we find it unlikely to be linked, since the luminosity distance has a negligible probability of being consistent with that of GW151226. In the 290 square degrees surveyed we therefore do not find a likely counterpart. However we show that our survey strategy would be sensitive to NS-NS mergers producing kilonovae at D-L less than or similar to 100 Mpc, which is promising for future LIGO/Virgo searches.
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| 5. |
- Pastorello, A., et al.
(author)
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Supernovae 2016bdu and 2005gl, and their link with SN 2009ip-like transients : another piece of the puzzle
- 2018
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 474:1, s. 197-218
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Journal article (peer-reviewed)abstract
- Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN 2009ip-like events are characterized by a long-lasting phase of erratic variability that ends with two luminous outbursts a few weeks apart. The second outburst is significantly more luminous (about 3 mag) than the first. In the case of SN 2016bdu, the first outburst (Event A) reached an absolute magnitude M-r approximate to -15.3 mag, while the second one (Event B) occurred over one month later and reached M-r approximate to -18 mag. By inspecting archival data, a faint source at the position of SN 2016bdu is several times in the past few years. We interpret these detections as signatures of a phase of erratic variability, similar to that experienced by SN 2009ip between 2008 and mid-2012, and resembling the currently observed variability of the luminous blue variable SN 2000ch in NGC 3432. Spectroscopic monitoring of SN 2016bdu during the second peak initially shows features typical of an SN IIn. One month after the Event B maximum, the spectra develop broad Balmer lines with P Cygni profiles and broad metal features. At these late phases, the spectra resemble those of a typical Type II SN. All members of this SN 2009ip-like group are remarkably similar to the Type IIn SN 2005gl. For this object, the claim of a terminal SN explosion is supported by the disappearance of the progenitor star. While the similarity with SN 2005gl supports a genuine SN explosion scenario for SN 2009ip-like events, the unequivocal detection of nucleosynthesized elements in their nebular spectra is still missing.
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| 6. |
- Trkulja, C. L., et al.
(author)
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Rational antibody design for undruggable targets using kinetically controlled biomolecular probes
- 2021
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In: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:16
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Journal article (peer-reviewed)abstract
- Several important drug targets, e.g., ion channels and G protein-coupled receptors, are extremely difficult to approach with current antibody technologies. To address these targets classes, we explored kinetically controlled proteases as structural dynamics-sensitive druggability probes in native-state and disease-relevant proteins. By using low-Reynolds number flows, such that a single or a few protease incisions are made, we could identify antibody binding sites (epitopes) that were translated into short-sequence antigens for antibody production. We obtained molecular-level information of the epitope-paratope region and could produce high-affinity antibodies with programmed pharmacological function against difficult-to-drug targets. We demonstrate the first stimulus-selective monoclonal antibodies targeting the transient receptor potential vanilloid 1 (TRPV1) channel, a clinically validated pain target widely considered undruggable with antibodies, and apoptosis-inducing antibodies selectively mediating cytotoxicity in KRAS-mutated cells. It is our hope that this platform will widen the scope of antibody therapeutics for the benefit of patients.
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| 7. |
- Lunnan, Ragnhild, et al.
(author)
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Hydrogen-poor Superluminous Supernovae from the Pan-STARRS1 Medium Deep Survey
- 2018
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In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 852:2
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Journal article (peer-reviewed)abstract
- We present light curves and classification spectra of 17 hydrogen-poor superluminous supernovae (SLSNe) from the Pan-STARRS1 Medium Deep Survey (PS1 MDS). Our sample contains all objects from the PS1. MDS sample with spectroscopic classification that are similar to either of the prototypes SN 2005ap or SN 2007bi, without an explicit limit on luminosity. With a redshift range 0.3 < z < 1.6, PS1. MDS is the first SLSN sample primarily probing the high-redshift population; our multifilter PS1 light curves probe the rest-frame UV emission, and hence the peak of the spectral energy distribution. We measure the temperature evolution and construct bolometric light curves, and find peak luminosities of (0.5-5) x 10(44) erg s(-1) and lower limits on the total radiated energies of (0.3-2) x 10(51) erg. The light curve shapes are diverse, with both rise and decline times spanning a factor of similar to 5 and several examples of double-peaked light curves. When correcting for the flux-limited nature of our survey, we find a median peak luminosity at 4000 angstrom of M-4000 = -21.1 mag and a spread of sigma = 0.7 mag.
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| 8. |
- Botting, Joseph P., et al.
(author)
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A Middle Ordovician Burgess Shale-type fauna from Castle Bank, Wales (UK)
- 2023
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In: Nature Ecology & Evolution. - : Springer Nature. - 2397-334X. ; 7:5, s. 666-674
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Journal article (peer-reviewed)abstract
- Burgess Shale-type faunas are critical to our understanding of animal evolution during the Cambrian, giving an unrivalled view of the morphology of ancient organisms and the ecology of the earliest animal-dominated communities. Rare examples in Lower Ordovician strata such as the Fezouata Biota illustrate the subsequent evolution of ecosystems but only from before the main phase of the Great Ordovician Biodiversification Event. Later Ordovician Konservat-Lagerstätten are not directly comparable with the Burgess Shale-type faunas as they do not represent diverse, open-shelf communities, limiting our ability to track ecological development through the critical Ordovician biodiversification interval. Here we present the Castle Bank fauna: a highly diverse Middle Ordovician Burgess Shale-type fauna from Wales (UK) that is directly comparable with the Burgess Shale and Chengjiang biotas in palaeoenvironment and preservational style. The deposit includes animals with morphologies similar to the iconic Cambrian taxa Opabinia, Yohoia and Wiwaxia, combined with early examples of more derived groups such as barnacles. Many taxa such as kinorhynchs show the small sizes typical of modern faunas, illustrating post-Cambrian miniaturization. Castle Bank provides a new perspective on early animal evolution, revealing the next chapter in ecosystem development following the Chengjiang, Burgess Shale and Fezouata biotas.
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| 9. |
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| 10. |
- Johansson, Annette M.
(author)
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Implementation of Videoconsultation to Increase Accessibility to Care and Specialist Care in Rural Areas : Residents, patients and healthcare personnel´s views
- 2015
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Doctoral thesis (other academic/artistic)abstract
- The overall aim of this doctoral thesis was to explore videoconsultation as a working tool to increase accessibility to care in rural areas for residents, patients and healthcare personnel. This thesis consists of four studies, two with a qualitative approach (II, III), one with a quantitative approach (I) and one with mix methods (IV). In study II, focus group discussions were conducted with healthcare personnel at five primary healthcare centres aimed to describe their views on videoconsultation before the centres implemented the technology. The data were analysed with qualitative content analysis. In study I, a questionnaire was constructed to describe residents’ views on accessibility to specialist care and on using videoconsultation as a tool to increase the accessibility. Data was analysed with descriptive statistics. In study III, 26 patients who have participated in videoconsultation were interviewed about their experiences with specialists care via videoconsultation. The interviews were analysed with thematic content analysis. In study IV, individual interviews were conducted with eight general practitioners and one district nurse to have them describe their experiences of using videoconsultation in rural areas. Consultation reports were developed to give knowledge about technical functionality and the VC. These data were analysed with content analysis and, descriptive statistics respectively. The results show that a patient-centered videoconsultation was important. An advantage for the patient was reduced travels for specialist care but a disadvantage was not to have the opportunity to meet the specialist physician face to face. An important prerequisite for the patient to feel safe in videoconsultation was that the personnel be comfortable with the technology. The results also reveal that it was important to evaluate costs and personal recourses before implementing the technology (II). The respondents first chose to meet the specialist physician face to face and in second hand via videoconsultation with their general practitioner beside them. Videoconsultation was considered to save time, money and environment when patients did not have to travel (II, III). Residents felt secure when they were allowed to choose for themselves if they should participate in videoconsultation or receive a referral (III). Healthcare personnel considered that videoconsultation encounter were a useful opportunities for education and discussions with the specialist physician (IV). To conclude, videoconsultation increase the accessibility to specialist care for residents in rural areas. Although videoconsultation is considered important for the specialist care accessibility, participants thought that there was times when face-to-face meeting was to prefer. Distance videoconsultation saves time and money for the patient, the healthcare organization and the environment.Key words: videoconsultation, e-health, rural areas, nursing, primary healthcare, specialist care
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| 11. |
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| 12. |
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| 13. |
- Nguyen-Cong, K., et al.
(author)
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Billion atom molecular dynamics simulations of carbon at extreme conditions and experimental time and length scales
- 2021
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In: SC '21: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis. - New York, NY, USA : Association for Computing Machinery (ACM).
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Conference paper (peer-reviewed)abstract
- Billion atom molecular dynamics (MD) using quantum-Accurate machine-learning Spectral Neighbor Analysis Potential (SNAP) observed long-sought high pressure BC8 phase of carbon at extreme pressure (12 Mbar) and temperature (5,000 K). 24-hour, 4650 node production simulation on OLCF Summit demonstrated an unprecedented scaling and unmatched real-world performance of SNAP MD while sampling 1 nanosecond of physical time. Efficient implementation of SNAP force kernel in LAMMPS using the Kokkos CUDA backend on NVIDIA GPUs combined with excellent strong scaling (better than 97% parallel efficiency) enabled a peak computing rate of 50.0 PFLOPs (24.9% of theoretical peak) for a 20 billion atom MD simulation on the full Summit machine (27,900 GPUs). The peak MD performance of 6.21 Matom-steps/node-s is 22.9 times greater than a previous record for quantum-Accurate MD. Near perfect weak scaling of SNAP MD highlights its excellent potential to advance the frontier of quantum-Accurate MD to trillion atom simulations on upcoming exascale platforms.
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| 14. |
- Nguyen-Cong, Kien, et al.
(author)
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Extreme Metastability of Diamond and its Transformation to the BC8 Post-Diamond Phase of Carbon
- 2024
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In: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 15:4, s. 1152-1160
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Journal article (peer-reviewed)abstract
- Diamond possesses exceptional physical properties due to its remarkably strong carbon-carbon bonding, leading to significant resilience to structural transformations at very high pressures and temperatures. Despite several experimental attempts, synthesis and recovery of the theoretically predicted post-diamond BC8 phase remains elusive. Through quantum-accurate multimillion atom molecular dynamics (MD) simulations, we have uncovered the extreme metastability of diamond at very high pressures, significantly exceeding its range of thermodynamic stability. We predict the post-diamond BC8 phase to be experimentally accessible only within a narrow high pressure-temperature region of the carbon phase diagram. The diamond to BC8 transformation proceeds through premelting followed by BC8 nucleation and growth in the metastable carbon liquid. We propose a double-shock compression pathway for BC8 synthesis, which is currently being explored in experiments at the National Ignition Facility.
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