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- Wagner, J., et al.
(författare)
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First 230? : GHz VLBI fringes on 3C 279 using the APEX Telescope (Research Note)
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 581
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We report about a 230? GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, the phased submillimeter array (SMA), and the SMT of the Arizona Radio Observatory (ARO). Methods. We installed VLBI equipment and measured the APEX station position to 1? cm accuracy (1σ). We then observed 3C 279 on 2012 May 7 in a 5? h 230? GHz VLBI track with baseline lengths of 2800? Mλ to 7200? Mλ and a finest fringe spacing of 28.6? μas. Results. Fringes were detected on all baselines with signal-to-noise ratios of 12 to 55 in 420? s. The correlated flux density on the longest baseline was ∼0.3? Jy beam-1, out of a total flux density of 19.8? Jy. Visibility data suggest an emission region ≤ 38? μas in size, and at least two components, possibly polarized. We find a lower limit of the brightness temperature of the inner jet region of about 1010? K. Lastly, we find an upper limit of 20% on the linear polarization fraction at a fringe spacing of ∼ 38? μas. Conclusions. With APEX the angular resolution of 230? GHz VLBI improves to 28.6? μas. This allows one to resolve the last-photon ring around the Galactic Center black hole event horizon, expected to be 40? μas in diameter, and probe radio jet launching at unprecedented resolution, down to a few gravitational radii in galaxies like M 87. To probe the structure in the inner parsecs of 3C 279 in detail, follow-up observations with APEX and five other mm-VLBI stations have been conducted (March 2013) and are being analyzed.
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- Bobrowski, N., et al.
(författare)
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Plume composition and volatile flux of Nyamulagira volcano, Democratic Republic of Congo, during birth and evolution of the lava lake, 2014–2015
- 2017
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Ingår i: Bulletin of Volcanology. - : Springer Science and Business Media LLC. - 0258-8900 .- 1432-0819. ; 79:12, s. 90-
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Tidskriftsartikel (refereegranskat)abstract
- Very little is known about the volatile element makeup of the gaseous emissions of Nyamulagira volcano. This paper tries to fill this gap by reporting the first gas composition measurements of Nyamulagira’s volcanic plume since the onset of its lava lake activity at the end of 2014. Two field surveys were carried out on 1 November 2014, and 13–15 October 2015. We applied a broad toolbox of volcanic gas composition measurement techniques in order to geochemically characterize Nyamulagira’s plume. Nyamulagira is a significant emitter of SO2, and our measurements confirm this, as we recorded SO2 emissions of up to ~ 14 kt/d during the studied period. In contrast to neighbouring Nyiragongo volcano, however, Nyamulagira exhibits relatively low CO2/SO2 molar ratios ( 92% of total gas emissions). Strong variations in the volatile composition, in particular for the CO2/SO2 ratio, were measured between 2014 and 2015, which appear to reflect the simultaneous variations in volcanic activity. We also determined the molar ratios for Cl/S, F/S and Br/S in the plume gas, finding values of 0.13 and 0.17, 0.06 and 0.11, and 2.3·10?4 and 1·10?4, in 2014 and 2015, respectively. A total gas emission flux of 48 kt/d was estimated for 2014. The I/S ratio in 2015 was found to be 3.6·10?6. In addition, we were able to distinguish between hydrogen halides and non-hydrogen halides in the volcanic plume. Considerable amounts of bromine (18–35% of total bromine) and iodine (8–18% of total iodine) were found in compounds other than hydrogen halides. However, only a negligible fraction of chlorine was found as compounds other than hydrogen chloride.
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| 10. |
- Duev, Dmitry, et al.
(författare)
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Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique: A test case of the Mars Express Phobos fly-by
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 593:A34
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Tidskriftsartikel (refereegranskat)abstract
- The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agency's Mars Express spacecraft, gives a unique opportunity to sharpen and test the Planetary Radio Interferometry and Doppler Experiments (PRIDE) technique in the interest of studying planet-satellite systems. Aims. The aim of this work is to demonstrate a technique of providing high precision positional and Doppler measurements of planetary spacecraft using the Mars Express spacecraft. The technique will be used in the framework of Planetary Radio Interferometry and Doppler Experiments in various planetary missions, in particular in fly-by mode. Methods. We advanced a novel approach to spacecraft data processing using the techniques of Doppler and phase-referenced very long baseline interferometry spacecraft tracking. Results. We achieved, on average, mHz precision (30 mu m/s at a 10 s integration time) for radial three-way Doppler estimates and sub-nanoradian precision for lateral position measurements, which in a linear measure (at a distance of 1.4 AU) corresponds to similar to 50 m.
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| 11. |
- Toller, W, et al.
(författare)
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Preoperative and perioperative use of levosimendan in cardiac surgery: European expert opinion.
- 2015
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 184, s. 323-336
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Forskningsöversikt (refereegranskat)abstract
- In cardiac surgery, postoperative low cardiac output has been shown to correlate with increased rates of organ failure and mortality. Catecholamines have been the standard therapy for many years, although they carry substantial risk for adverse cardiac and systemic effects, and have been reported to be associated with increased mortality. On the other hand, the calcium sensitiser and potassium channel opener levosimendan has been shown to improve cardiac function with no imbalance in oxygen consumption, and to have protective effects in other organs. Numerous clinical trials have indicated favourable cardiac and non-cardiac effects of preoperative and perioperative administration of levosimendan. A panel of 27 experts from 18 countries has now reviewed the literature on the use of levosimendan in on-pump and off-pump coronary artery bypass grafting and in heart valve surgery. This panel discussed the published evidence in these various settings, and agreed to vote on a set of questions related to the cardioprotective effects of levosimendan when administered preoperatively, with the purpose of reaching a consensus on which patients could benefit from the preoperative use of levosimendan and in which kind of procedures, and at which doses and timing should levosimendan be administered. Here, we present a systematic review of the literature to report on the completed and ongoing studies on levosimendan, including the newly commenced LEVO-CTS phase III study (NCT02025621), and on the consensus reached on the recommendations proposed for the use of preoperative levosimendan.
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| 12. |
- Bittersohl, Bernd, et al.
(författare)
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Advanced Imaging in Femoroacetabular Impingement: Current State and Future Prospects.
- 2015
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Ingår i: Frontiers in surgery. - : Frontiers Media SA. - 2296-875X. ; 2, s. 34-34
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Forskningsöversikt (refereegranskat)abstract
- Symptomatic femoroacetabular impingement (FAI) is now a known precursor of early osteoarthritis (OA) of the hip. In terms of clinical intervention, the decision between joint preservation and joint replacement hinges on the severity of articular cartilage degeneration. The exact threshold during the course of disease progression when the cartilage damage is irreparable remains elusive. The intention behind radiographic imaging is to accurately identify the morphology of osseous structural abnormalities and to accurately characterize the chondrolabral damage as much as possible. However, both plain radiographs and computed tomography (CT) are insensitive for articular cartilage anatomy and pathology. Advanced magnetic resonance imaging (MRI) techniques include magnetic resonance arthrography and biochemically sensitive techniques of delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T1rho (T1ρ), T2/T2* mapping, and several others. The diagnostic performance of these techniques to evaluate cartilage degeneration could improve the ability to predict an individual patient-specific outcome with non-surgical and surgical care. This review discusses the facts and current applications of biochemical MRI for hip joint cartilage assessment covering the roles of dGEMRIC, T2/T2*, and T1ρ mapping. The basics of each technique and their specific role in FAI assessment are outlined. Current limitations and potential pitfalls as well as future directions of biochemical imaging are also outlined.
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| 13. |
- Hunkeler, Priska A., et al.
(författare)
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Improved 1D inversions for sea ice thickness and conductivity from electromagnetic induction data : Inclusion of nonlinearities caused by passive bucking
- 2016
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Ingår i: Geophysics. - 0016-8033 .- 1942-2156. ; 81:1, s. WA45-WA58
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Tidskriftsartikel (refereegranskat)abstract
- The porosity of sea ice is a fundamental physical parameter that governs the mechanical strength of sea ice and the mobility of gases and nutrients for biological processes and biogeochemical cycles in the sea ice layer. However, little is known about the spatial distribution of the sea ice porosity and its variability between different sea ice types; an efficient and nondestructive method to measure this property is currently missing. Sea ice porosity is linked to the bulk electrical conductivity of sea ice, a parameter routinely used to discriminate between sea ice and seawater by electromagnetic (EM) induction sensors. Here, we have evaluated the prospect of porosity retrieval of sea ice by means of bulk conductivity estimates using 1D multi-frequency EM inversion schemes. We have focused on two inversion algorithms, a smoothness-constrained inversion and a Marquardt-Levenberg inversion, which we modified for the nonlinear signal bias caused by a passive bucking coil operated in such a highly conductive environment. Using synthetic modeling studies, 1D inversion algorithms and multiple frequencies, we found that we can resolve the sea ice conductivity within +/- 0.01 S/m. Using standard assumptions for the conductivity-porosity relation of sea ice, we were able to estimate porosity with an uncertainty of +/- 1.2%, which enables efficient and nondestructive surveys of the internal state of the sea ice cover.
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| 14. |
- Marquardt, Kai S., et al.
(författare)
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Type Ia supernovae from exploding oxygen-neon white dwarfs
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 580
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Tidskriftsartikel (refereegranskat)abstract
- Context: The progenitor problem of Type Ia supernovae (SNe Ia) is still unsolved. Most of these events are thought to be explosions of carbon-oxygen (CO) white dwarfs (WDs), but for many of the explosion scenarios, particularly those involving the externally triggered detonation of a sub-Chandrasekhar mass WD (sub-M-Ch, WD), there is also a possibility of having an oxygen-neon (ONe) WD as progenitor.Aims: We simulate detonations of ONe WDs and calculate synthetic observables from these models. The results are compared with detonations in CO WDs of similar mass and observational data of SNe Ia.Methods: We perform hydrodynamic explosion simulations of detonations in initially hydrostatic ONe WDs for a range of masses below the Chandrasekhar mass (M-Ch), followed by detailed nucleosynthetic postprocessing with a 384-isotope nuclear reaction network. The results are used to calculate synthetic spectra and light curves, which are then compared with observations of SNe Ia. We also perform binary evolution calculations to determine the number of SNe Ia involving ONe WDs relative to the number of other promising progenitor channels.Results: The ejecta structures of our simulated detonations in sub-M-Ch, ONe WDs are similar to those from CO WDs. There are, however, small systematic deviations in the mass fractions and the ejecta velocities. These lead to spectral features that are systematically less blueshifted. Nevertheless, the synthetic observables of our ONe WD explosions are similar to those obtained from CO models.Conclusions: Our binary evolution calculations show that a significant fraction (3-10%) of potential progenitor systems should contain an ONe WD. The comparison of our ONe models with our CO models of comparable mass (similar to 1.2 M-circle dot) shows that the less blueshifted spectral features fit the observations better, although they are too bright for normal SNe Ia.
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| 15. |
- Morriën, Elly, et al.
(författare)
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Soil networks become more connected and take up more carbon as nature restoration progresses
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Soil organisms have an important role in aboveground community dynamics and ecosystem functioning in terrestrial ecosystems. However, most studies have considered soil biota as a black box or focussed on specific groups, whereas little is known about entire soil networks. Here we show that during the course of nature restoration on abandoned arable land a compositional shift in soil biota, preceded by tightening of the belowground networks, corresponds with enhanced efficiency of carbon uptake. In mid- and long-term abandoned field soil, carbon uptake by fungi increases without an increase in fungal biomass or shift in bacterial-to-fungal ratio. The implication of our findings is that during nature restoration the efficiency of nutrient cycling and carbon uptake can increase by a shift in fungal composition and/or fungal activity. Therefore, we propose that relationships between soil food web structure and carbon cycling in soils need to be reconsidered.
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| 16. |
- Nieminen, Markku S., et al.
(författare)
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The patient perspective : Quality of life in advanced heart failure with frequent hospitalisations
- 2015
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 191, s. 256-264
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Forskningsöversikt (refereegranskat)abstract
- End of life is an unfortunate but inevitable phase of the heart failure patients' journey. It is often preceded by a stage in the progression of heart failure defined as advanced heart failure, and characterised by poor quality of life and frequent hospitalisations. In clinical practice, the efficacy of treatments for advanced heart failure is often assessed by parameters such as clinical status, haemodynamics, neurohormonal status, and echo/MRI indices. From the patients' perspective, however, quality-of-life-related parameters, such as functional capacity, exercise performance, psychological status, and frequency of re-hospitalisations, are more significant. The effects of therapies and interventions on these parameters are, however, underrepresented in clinical trials targeted to assess advanced heart failure treatment efficacy, and data are overall scarce. This is possibly due to a non-universal definition of the quality-of-life-related endpoints, and to the difficult standardisation of the data collection. These uncertainties also lead to difficulties in handling trade-off decisions between quality of life and survival by patients, families and healthcare providers. A panel of 34 experts in the field of cardiology and intensive cardiac care from 21 countries around the world convened for reviewing the existing data on quality-of-life in patients with advanced heart failure, discussing and reaching a consensus on the validity and significance of quality-of-life assessment methods. Gaps in routine care and research, which should be addressed, were identified. Finally, published data on the effects of current i.v. vasoactive therapies such as inotropes, inodilators, and vasodilators on quality-of-life in advanced heart failure patients were analysed.
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| 17. |
- Tuccari, Gino, et al.
(författare)
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DBBC3 — The new wide-band backend for VLBI
- 2018
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Ingår i: Proceedings of Science. - 1824-8039. ; 344
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Konferensbidrag (refereegranskat)abstract
- The DBBC3 VLBI digital backend is the successor of the most widely adapted digital VLBI backend DBBC2. The DBBC3 offers much wider bandwidth and integrated Ethernet output. Three different firmwares for observing have been implemented until now: Direct Sampling Conversion (DSC), arbitrary selection of bands (OCT), and Digital Down Conversion (DDC). These modes cover all the requirements of the astronomical, VGOS and legacy geodetic VLBI of today, but also of the near future. In addition the DBBC3 offers unsurpassed compatibility to the relatively large number of other existing VLBI backends. A number of DBBC3 systems have been deployed and more are currently under construction, with the number of 4 GHz bands ranging from 2 up to 8 with resulting typical output data-rates from 32 Gbps to 128 Gbps. Laboratory and field tests have been performed.
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