| 1. |
- Bombarda, F., et al.
(författare)
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Runaway electron beam control
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Joffrin, E., et al.
(författare)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
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| 3. |
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| 4. |
- Krasilnikov, A., et al.
(författare)
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Evidence of 9 Be + p nuclear reactions during 2ω CH and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas
- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:2
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Tidskriftsartikel (refereegranskat)abstract
- The intensity of 9Be + p nuclear fusion reactions was experimentally studied during second harmonic (2ω CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to 9Be + p interaction, were observed with fast ion loss detectors, γ-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using 9Be(p, d)2α and 9Be(p, α)6Li nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.
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| 5. |
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| 6. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:1
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Forskningsöversikt (refereegranskat)
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| 7. |
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| 23. |
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| 25. |
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| 26. |
- Meyer, H.F., et al.
(författare)
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Overview of physics studies on ASDEX Upgrade
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- The ASDEX Upgrade (AUG) programme, jointly run with the EUROfusion MST1 task force, continues to significantly enhance the physics base of ITER and DEMO. Here, the full tungsten wall is a key asset for extrapolating to future devices. The high overall heating power, flexible heating mix and comprehensive diagnostic set allows studies ranging from mimicking the scrape-off-layer and divertor conditions of ITER and DEMO at high density to fully non-inductive operation (q 95 = 5.5, ) at low density. Higher installed electron cyclotron resonance heating power 6 MW, new diagnostics and improved analysis techniques have further enhanced the capabilities of AUG. Stable high-density H-modes with MW m-1 with fully detached strike-points have been demonstrated. The ballooning instability close to the separatrix has been identified as a potential cause leading to the H-mode density limit and is also found to play an important role for the access to small edge-localized modes (ELMs). Density limit disruptions have been successfully avoided using a path-oriented approach to disruption handling and progress has been made in understanding the dissipation and avoidance of runaway electron beams. ELM suppression with resonant magnetic perturbations is now routinely achieved reaching transiently . This gives new insight into the field penetration physics, in particular with respect to plasma flows. Modelling agrees well with plasma response measurements and a helically localised ballooning structure observed prior to the ELM is evidence for the changed edge stability due to the magnetic perturbations. The impact of 3D perturbations on heat load patterns and fast-ion losses have been further elaborated. Progress has also been made in understanding the ELM cycle itself. Here, new fast measurements of and E r allow for inter ELM transport analysis confirming that E r is dominated by the diamagnetic term even for fast timescales. New analysis techniques allow detailed comparison of the ELM crash and are in good agreement with nonlinear MHD modelling. The observation of accelerated ions during the ELM crash can be seen as evidence for the reconnection during the ELM. As type-I ELMs (even mitigated) are likely not a viable operational regime in DEMO studies of 'natural' no ELM regimes have been extended. Stable I-modes up to have been characterised using -feedback. Core physics has been advanced by more detailed characterisation of the turbulence with new measurements such as the eddy tilt angle - measured for the first time - or the cross-phase angle of and fluctuations. These new data put strong constraints on gyro-kinetic turbulence modelling. In addition, carefully executed studies in different main species (H, D and He) and with different heating mixes highlight the importance of the collisional energy exchange for interpreting energy confinement. A new regime with a hollow profile now gives access to regimes mimicking aspects of burning plasma conditions and lead to nonlinear interactions of energetic particle modes despite the sub-Alfvénic beam energy. This will help to validate the fast-ion codes for predicting ITER and DEMO.
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| 27. |
- Hoelzl, M., et al.
(författare)
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Insights into type-I edge localized modes and edge localized mode control from JOREK non-linear magneto-hydrodynamic simulations
- 2018
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Ingår i: Contributions to Plasma Physics. - : Wiley-VCH Verlagsgesellschaft. - 0863-1042 .- 1521-3986. ; 58:6-8, s. 518-528
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Tidskriftsartikel (refereegranskat)abstract
- Edge localized modes (ELMs) are repetitive instabilities driven by the large pressure gradients and current densities in the edge of H-mode plasmas. Type-I ELMs lead to a fast collapse of the H-mode pedestal within several hundred microseconds to a few milliseconds. Localized transient heat fluxes to divertor targets are expected to exceed tolerable limits for ITER, requiring advanced insights into ELM physics and applicable mitigation methods. This paper describes how non-linear magneto-hydrodynamic (MHD) simulations can contribute to this effort. The JOREK code is introduced, which allows the study of large-scale plasma instabilities in tokamak X-point plasmas covering the main plasma, the scrape-off layer, and the divertor region with its finite element grid. We review key physics relevant for type-I ELMs and show to what extent JOREK simulations agree with experiments and help reveal the underlying mechanisms. Simulations and experimental findings are compared in many respects for type-I ELMs in ASDEX Upgrade. The role of plasma flows and non-linear mode coupling for the spatial and temporal structure of ELMs is emphasized, and the loss mechanisms are discussed. An overview of recent ELM-related research using JOREK is given, including ELM crashes, ELM-free regimes, ELM pacing by pellets and magnetic kicks, and mitigation or suppression by resonant magnetic perturbation coils (RMPs). Simulations of ELMs and ELM control methods agree in many respects with experimental observations from various tokamak experiments. On this basis, predictive simulations become more and more feasible. A brief outlook is given, showing the main priorities for further research in the field of ELM physics and further developments necessary.
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| 28. |
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| 29. |
- Cook, D. O., et al.
(författare)
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Star cluster catalogues for the LEGUS dwarf galaxies
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 484:4, s. 4897-4919
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Tidskriftsartikel (refereegranskat)abstract
- We present the star cluster catalogues for 17 dwarf and irregular galaxies in the HST Treasury Program 'Legacy ExtraGalactic UV Survey' (LEGUS). Cluster identification and photometry in this sub-sample are similar to that of the entire LEGUS sample, but special methods were developed to provide robust catalogues with accurate fluxes due to low cluster statistics. The colours and ages are largely consistent for two widely used aperture corrections, but a significant fraction of the clusters are more compact than the average training cluster. However, the ensemble luminosity, mass, and age distributions are consistent suggesting that the systematics between the two methods are less than the random errors. When compared with the clusters from previous dwarf galaxy samples, we find that the LEGUS catalogues are more complete and provide more accurate total fluxes. Combining all clusters into a composite dwarf galaxy, we find that the luminosity and mass functions can be described by a power law with the canonical index of -2 independent of age and global SFR binning. The age distribution declines as a power law, with an index of approximate to -0.80 +/- 0.15, independent of cluster mass and global SFR binning. This decline of clusters is dominated by cluster disruption since the combined star formation histories and integrated-light SFRs are both approximately constant over the last few hundred Myr. Finally, we find little evidence for an upper-mass cut-off (< 2 sigma) in the composite cluster mass function, and can rule out a truncation mass below approximate to 10(4.5)M(circle dot) but cannot rule out the existence of a truncation at higher masses.
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| 30. |
- Adamo, Angela, et al.
(författare)
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Legacy ExtraGalactic UV Survey with The Hubble Space Telescope : Stellar Cluster Catalogs and First Insights Into Cluster Formation and Evolution in NGC 628
- 2017
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 841:2
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Tidskriftsartikel (refereegranskat)abstract
- We report the large effort that is producing comprehensive high-level young star cluster (YSC) catalogs for a significant fraction of galaxies observed with the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. We present the methodology developed to extract cluster positions, verify their genuine nature, produce multiband photometry (from NUV to NIR), and derive their physical properties via spectral energy distribution fitting analyses. We use the nearby spiral galaxy NGC 628 as a test case for demonstrating the impact that LEGUS will have on our understanding of the formation and evolution of YSCs and compact stellar associations within their host galaxy. Our analysis of the cluster luminosity function from the UV to the NIR finds a steepening at the bright end and at all wavelengths suggesting a dearth of luminous clusters. The cluster mass function of NGC 628 is consistent with a power-law distribution of slopes similar to-2 and a truncation of a few times 10(5) M-circle dot. After their formation, YSCs and compact associations follow different evolutionary paths. YSCs survive for a longer time frame, confirming their being potentially bound systems. Associations disappear on timescales comparable to hierarchically organized star-forming regions, suggesting that they are expanding systems. We find massindependent cluster disruption in the inner region of NGC 628, while in the outer part of the galaxy there is little or no disruption. We observe faster disruption rates for low mass (<= 10(4) M-circle dot) clusters, suggesting that a massdependent component is necessary to fully describe the YSC disruption process in NGC 628.
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| 31. |
- Dalaei, Farima, et al.
(författare)
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Body Contouring Surgery after Bariatric Surgery Improves Long-Term Health-Related Quality of Life and Satisfaction with Appearance : An International Longitudinal Cohort Study Using the BODY-Q
- 2024
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Ingår i: Annals of Surgery. - 0003-4932. ; 279:6, s. 1008-1017
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To examine health-related quality of life (HRQL) and satisfaction with appearance in patients who have undergone bariatric surgery (BS) with or without subsequent body contouring surgery (BCS) in relation to the general population normative for the BODY-Q. Background: The long-term impact of BS with or without BCS has not been established using rigorously developed and validated patient-reported outcome measures. The BODY-Q is a patient-reported outcome measure developed to measure changes in HRQL and satisfaction with appearance in patients with BS and BCS. Methods: Prospective BODY-Q data were collected from 6 European countries (Denmark, the Netherlands, Finland, Germany, Italy, and Poland) from June 2015 to February 2022 in a cohort of patients who underwent BS. Mixed-effects regression models were used to analyze changes in HRQL and appearance over time between patients who did and did not receive BCS and to examine the impact of patient-level covariates on outcomes. Results: This study included 24,604 assessments from 5620 patients. BS initially led to improved HRQL and appearance scores throughout the first postbariatric year, followed by a gradual decrease. Patients who underwent subsequent BCS after BS experienced a sustained improvement in HRQL and appearance or remained relatively stable for up to 10 years postoperatively. Conclusions: Patients who underwent BCS maintained an improvement in HRQL and satisfaction with appearance in contrast to patients who only underwent BS, who reported a decline in scores 1 to 2 years postoperatively. Our results emphasize the pivotal role that BCS plays in the completion of the weight loss trajectory.
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| 32. |
- Jalilehvand, F., et al.
(författare)
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New class of oligonuclear platinum-thallium compounds with a direct metal-metal bond. 5. Structure determination of heterodimetallic cyano complexes in aqueous solution by EXAFS and vibrational spectroscopy
- 2001
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 40:16, s. 3889-3899
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Tidskriftsartikel (refereegranskat)abstract
- The structures of three closely related heterodimetallic cyano complexes, [(NC)(5)Pt-Tl(CN)(n)](n-) (n = 1-3), formed in reactions between [Pt-II(CN)(4)](2-) and Tl-III cyano complexes, have been studied in aqueous solution. Multinuclear NMR data ((TI)-T-205, Pt-195, and C-13) were used for identification and quantitative analysis. X-ray absorption spectra were recorded at the Pt and TlLIII edges. The EXAFS data show, after developing a model describing the extensive multiple scattering within the linearly coordinated cyano ligands, short Pt-Tl bond distances in the [(NC)(5)Pt-Tl(CN)(n)](n-) complexes: 2.60(1), 2.62(1), and 2.64(1) Angstrom for n = 1-3, respectively. Thus, the Pt-Tl bond distance increases with increasing number of cyano ligands on the thallium atom. In all three complexes the thallium atom and five cyano ligands, with a mean Pt-C distance of 2.00-2.01 Angstrom, octahedrally coordinate the platinum atom. In the hydrated [(NC)(5)Pt-Tl(CN)(H2O)(4)](-) species the thallium atom coordinates one cyano ligand, probably as a linear Pt-TI-CN entity with a Tl-C bond distance of 2.13(1) Angstrom, and possibly four loosely bound water molecules with a mean Tl-O bond distance of about 2.51 Angstrom. In the [(NC)(5)Pt-Tl(CN)(2)](2-) species, the thallium atom probably coordinates the cyano ligands trigonally with two TI-C bond distances at 2.20(2) Angstrom, and in [(NC)(5)Pt-Tl(CN)(3)]Tl3- coordinates tetrahedrally with three TI-C distances at 2.22(2) Angstrom. EXAFS data were reevaluated for previously studied mononuclear thallium(III)-cyano complexes in aqueous solution, [Tl(CN)(2)(H2O)(4)](+), [Tl(CN)(3)(H2O)], and [Tl(CN)(4)](-), and also for the solid K[TI(CN)(4)] compound. A comparison shows that the TI-C bond distances are longer in the dinuclear complexes [(NC)(5)Pt-TI(CN)(n)](n-) (it = 1-3) for the same coordination number. Relative oxidation states of the metal atoms were estimated from their Pt-195 and (TI)-T-205 chemical shifts, confirming that the I(NC)5Pt-TI(CN),]n- complexes can be considered as metastable intermediates in a two-electron-transfer redox reaction from platinum(II) to thallium(III). Vibrational spectra were recorded and force constants from normal-coordinate analyses are used for discussing the delocalized bonding in these species.
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| 33. |
- Jalilehvand, F., et al.
(författare)
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Structure studies of dimeric Pt-2(CN)(10) (4-) pentacyanoplatinum(III) and monomeric pentacyanoplatinum(IV) complexes by EXAFS, vibrational spectroscopy, and X-ray crystallography
- 2002
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 106:14, s. 3501-3516
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Tidskriftsartikel (refereegranskat)abstract
- The Structures of the dimeric bispentacyanoplatinate (III) (Pt-Pt) complex [Pt-2(CN)(10)](4-) and the pentacyanoplatinuni(IV) species [Pt(CN)(5)(OH)](2-), [Pt(CN)(5)(H2O)](-), and [Pt(CN)(5)I](2-) have been studied in aqueous solution by the EXAFS technique. A nonsupported Pt-Pt bond, 2.73(l) Angstrom, connects two Pt(CN)(5) entities in the dimer. Normal coordinate analyses have been made on the basis of the Raman spectra, and the force constants have been used for discussions of the bonding. The metal-metal stretching force constants for the [Pt-2(CN)(10)](4-) Complex, the [(NC)(5)Pt-TI(CN)(n)](n-) (n = 1, 2, and 3) complexes, and some other dimetallic complexes have been correlated with the metal-metal bond distances. In the [Pt(CN)(5)X](n-) complexes, the mean Pt-C bond distance of the pentacyanoplatinum group was found to increase, and the corresponding Pt-C force constants were found to decrease, with increasing donor ability of the ligand X in the order X = H2O, OH, I, and Pt(CN)(5). The crystal structures of the compounds Tl-2[Pt(CN)(5)(OH)] and K-2[Pt(CN)(5)I].0.6H(2)O were determined by single-crystal X-ray diffraction techniques and used for comparisons with the EXAFS models. The Pt-I bond distance of the [Pt(CN)(5)I](2)- complex is 2.676(2) Angstrom in the crystal structure and 2.66(1) Angstrom in solution by EXAFS. A method is described for estimating the force constant for the metal-metal bond stretch in dimetallic complexes with heavy metal atoms, based on the use of an effective spectroscopic mass of the metal atoms in a diatomic model. The 18-electron rule is found to be useful for rationalizing the structures of the metal-metal bonded cyano complexes and a guideline in searching for metal cyano complexes analogous to those currently described.
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| 34. |
- Jalilehvand, F., et al.
(författare)
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Tl-Pt(CN)(5) in the solid state - A multimethod study of an unusual compound containing inorganic wires
- 2001
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Ingår i: Chemistry - A European Journal. - 0947-6539 .- 1521-3765. ; 7:10, s. 2167-2177
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Tidskriftsartikel (refereegranskat)abstract
- The crystal and molecular structure of a polycrystalline powder with a metal-metal bond and the composition TlPt(CN)(5) has been determined by combining results from X-ray powder diffraction (XRD), extended X-ray absorption fine structure (EXAFS) and vibrational spectroscopic studies. The XRD data gave the tetragonal space group P4/nmm (No. 129). with a = 7.647(3), c = 8.049(3) Angstrom, Z = 2, and well-determined positions of the heavy metal atoms. The Pt-Tl bond length in the compound is 2.627(2) Angstrom. The platinum atom coordinates four equivalent equatorial cyano ligands, with a fifth axial CN ligand and a thallium atom completing a distorted octahedral coordination geometry. The Tl-Pt(CN)(5) entities are linked together in linear -NC-Pt-Tl-NC-Pt-Tl chains through the axial cyano ligand. These linear wires are the essential structural features and influence the properties of the com-pound. A three-dimensional network is formed by the four equatorial cyano ligands of the platinum atom that form bridges to the thallium atoms of neighbouring antiparallel chains. The platinum atom and the five nitrogen atoms from the bridging cyano groups form a distorted octahedron around the thallium atom. EXAFS data were recorded at the Pt and Tl L-III edges for a more complete description of the local structure around the Pt and Tl atoms. The excessive multiple scattering was evaluated by means of the FEFF program. Raman and infrared absorption spectroscopy reveal strong coupling of the vibrational modes of the TlPt(CN)(5) entities, in particular the metal - metal stretching mode, which is split into four Raman and two IR bands. Factor group theory shows that a structural unit larger than the crystallographic unit cell must be used to assign vibrational bands. Intra- and intermolecular force constants have also been calculated. The compound exhibits red luminescence at 700+/- 3 nm in glycerol and has a corresponding excitation maximum at 240 nm. X-ray photoelectron spectra (XPS) show that the metal atoms have intermediate oxidation states, Pt3.2+ and Tl1.6+, between those in the parent Pt-II and Tl-III species and the decomposition products, Pt-IV and Tl-I. The solid compound TlPt(CN)(5) is stable to 520 degreesC. However in presence of water, a two-electron transfer between the metal atoms results in the cleavage of the metal-metal bond at 80 degreesC, forming a Pt-IV pentacyanohydrate complex and a monovalent thallium ion.
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| 35. |
- Kahre, L., et al.
(författare)
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Extinction Maps and Dust-to-gas Ratios in Nearby Galaxies with LEGUS
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 855:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the dust-to-gas ratios in five nearby galaxies: NGC 628 (M74), NGC 6503, NGC 7793, UGC 5139 (Holmberg I), and UGC 4305 (Holmberg II). Using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury program Legacy ExtraGalactic UV Survey (LEGUS) combined with archival HST/Advanced Camera for Surveys data, we correct thousands of individual stars for extinction across these five galaxies using an isochrone-matching (reddening-free Q) method. We generate extinction maps for each galaxy from the individual stellar extinctions using both adaptive and fixed resolution techniques and correlate these maps with neutral H I and CO gas maps from the literature, including the H I Nearby Galaxy Survey and the HERA CO-Line Extragalactic Survey. We calculate dust-to-gas ratios and investigate variations in the dust-to-gas ratio with galaxy metallicity. We find a power-law relationship between dust-to-gas ratio and metallicity, consistent with other studies of dust-to-gas ratio compared to metallicity. We find a change in the relation when H-2 is not included. This implies that underestimation of N-H2 in low-metallicity dwarfs from a too-low CO-to-H-2 conversion factor X-CO could have produced too low a slope in the derived relationship between dust-to-gas ratio and metallicity. We also compare our extinctions to those derived from fitting the spectral energy distribution (SED) using the Bayesian Extinction and Stellar Tool for NGC 7793 and find systematically lower extinctions from SED fitting as compared to isochrone matching.
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| 36. |
- Kamann, S., et al.
(författare)
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The effects of stellar rotation along the main sequence of the 100-Myr-old massive cluster NGC 1850
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 518:1, s. 1505-1521
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Tidskriftsartikel (refereegranskat)abstract
- Young star clusters enable us to study the effects of stellar rotation on an ensemble of stars of the same age and across a wide range in stellar mass and are therefore ideal targets for understanding the consequences of rotation on stellar evolution. We combine MUSE spectroscopy with HST photometry to measure the projected rotational velocities (Vsin i) of 2184 stars along the split main sequence and on the main sequence turn-off (MSTO) of the 100 Myr-old massive (10(5) M-circle dot) star cluster NGC 1850 in the Large Magellanic Cloud. At fixed magnitude, we observe a clear correlation between Vsin i and colour, in the sense that fast rotators appear redder. The average Vsin i values for stars on the blue and red branches of the split main sequence are similar to 100 km s(-1) and similar to 200 km s(-1), respectively. The values correspond to about 25 - 30 per cent and 50 - 60 per cent of the critical rotation velocity and imply that rotation rates comparable to those observed in field stars of similar masses can explain the split main sequence. Our spectroscopic sample contains a rich population of similar to 200 fast rotating Be stars. The presence of shell features suggests that 23 per cent of them are observed through their decretion discs, corresponding to a disc opening angle of 15 degrees. These shell stars can significantly alter the shape of the MSTO, hence care should be taken when interpreting this photometric feature. Overall, our findings impact our understanding of the evolution of young massive clusters and provide new observational constraints for testing stellar evolutionary models.
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| 37. |
- Kocsis, L., et al.
(författare)
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Vibrational spectroscopic study of the hydrated platinum(II), palladium(II) and cis-diammineplatinum(II) ions in acidic aqueous solutions
- 2009
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:5, s. 481-490
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Tidskriftsartikel (refereegranskat)abstract
- Mid infrared, far-infrared and Raman spectroscopic studies, combined with force field analyses, were performed for the 1 hydrated platinum(II) and palladium(II) ions and cis-diammineplatinum(II) complex in acidic aqueous solutions. Simplified Density Functional Theory (DFT) calculations were made for the equatorial plane of the platinum complexes. Careful subtraction of solvent spectra allowed a number of 'internal' modes of coordinated H2O and NH3 to be determined as weak residual bands. The [Pt(OH2)(6)](2+) and [cis-Pt(NH3)(2)(OH2)(4)](2+) complexes were found to be six-coordinated with four ligands strongly bound in an equatorial plane. The assignments of the vibrational modes in the equatorial plane could be performed on the basis of the experimental observations and by comparison with metal-ligand vibrations of square-planar complexes, aided by normal coordinate calculations. For the weakly coordinated axial aqua ligands, the low wavenumber range and the polarizibility properties allowed the assignments of the bands at about 365 and 325 cm(-1) to the stretching modes of one short and one longer Pt - O* bound to axial aqua ligands, respectively. A similar picture with even less strongly bound axial water molecules emerges from Raman spectroscopy data for the hydrated palladium(II) ion, [Pd(OH2)(6)](2+). The results are consistent with a description of the [Pt(OH2)(6)](2+) and [Pd(OH2)(6)](2+) aqua ions in C-4v symmetry, and with the [cis-Pt(NH3)(2)(OH2)(4)](2+) complex in the Cs point group, and also in qualitative agreement with the structures devised from previous extended X-ray absorption fine structure (EXAFS) measurements.
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| 38. |
- Kranak, Verina F., et al.
(författare)
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Structural and Vibrational Properties of Silyl (SiH3-) Anions in KSiH3 and RbSiH3 : New Insight into Si-H Interactions
- 2015
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 54:5, s. 2300-2309
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Tidskriftsartikel (refereegranskat)abstract
- The alkali metal silyl hydrides ASiH(3) (A = K, Rb) and their deuteride analogues were prepared from the Zintl phases ASi. The crystal structures of ASiH(3) consist of metal cations and pyramidal SiH3 ions. At room temperature SiH3 moieties are randomly oriented (alpha modifications). At temperatures below 200 K ASiH(3) exist as ordered low-temperature (beta) modifications. Structural and vibrational properties of SiH3- in ASiH(3) were characterized by a combination of neutron total scattering experiments, infrared and Raman spectroscopy, as well as density functional theory calculations. In disordered alpha-ASiH(3) SiH3 ions relate closely to freely rotating moieties with C(3)v symmetry (Si-H bond length = 1.52 angstrom; HSiH angle 92.2 degrees). Observed stretches and bends are at 1909/1903 cm(-1) (nu(1), A(1)), 1883/1872 cm(-1) (nu(3), E), 988/986 cm(-1) (nu(4), E), and 897/894 cm(-1) (nu(2), A(1)) for A = K/Rb. In ordered beta-ASiH(3) silyl anions are slightly distorted with respect to their ideal C-3v symmetry. Compared to a-ASiH(3) the molar volume is by about 15% smaller and the SiH stretching force constant is reduced by 4%. These peculiarities are attributed to reorientational dynamics of SiH3 anions in a-ASiH(3). SiH stretching force constants for SiH3 moieties in various environments fall in a range from 1.9 to 2.05 N cm(-1). These values are considerably smaller compared to silane, SiH4 (2.77 N cm(-1)). The reason for the drastic reduction of bond strength in SiH3- remains to be explored.
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| 39. |
- Ricke-Hoch, Melanie, et al.
(författare)
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Impaired immune response mediated by prostaglandin E2 promotes severe COVID-19 disease
- 2021
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 16:8
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Tidskriftsartikel (refereegranskat)abstract
- The SARS-CoV-2 coronavirus has led to a pandemic with millions of people affected. The present study finds that risk-factors for severe COVID-19 disease courses, i.e. male sex, older age and sedentary life style are associated with higher prostaglandin E2 (PGE2) serum levels in blood samples from unaffected subjects. In COVID-19 patients, PGE2 blood levels are markedly elevated and correlate positively with disease severity. SARS-CoV-2 induces PGE2 generation and secretion in infected lung epithelial cells by upregulating cyclo-oxygenase (COX)-2 and reducing the PG-degrading enzyme 15-hydroxyprostaglan-din-dehydrogenase. Also living human precision cut lung slices (PCLS) infected with SARS-CoV-2 display upregulated COX-2. Regular exercise in aged individuals lowers PGE2 serum levels, which leads to increased Paired-Box-Protein-Pax-5 (PAX5) expression, a master regulator of B-cell survival, proliferation and differentiation also towards long lived memory B-cells, in human pre-B-cell lines. Moreover, PGE2 levels in serum of COVID-19 patients lowers the expression of PAX5 in human pre-B-cell lines. The PGE2 inhibitor Taxifolin reduces SARS-CoV-2-induced PGE2 production. In conclusion, SARS-CoV-2, male sex, old age, and sedentary life style increase PGE2 levels, which may reduce the early anti-viral defense as well as the development of immunity promoting severe disease courses and multiple infections. Regular exercise and Taxifolin treatment may reduce these risks and prevent severe disease courses.
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| 40. |
- Robberto, Massimo, et al.
(författare)
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HST Survey of the Orion Nebula Cluster in the H2O 1.4 μm Absorption Band. I. A Census of Substellar and Planetary-mass Objects
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 896:1
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain a complete census of the stellar and substellar population, down to a few MJup in the ∼1 Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the 1.4 μm H2O absorption feature and an adjacent line-free continuum region. Out of 4504 detected sources, 3352 (about 75%) appear fainter than m 130 = 14 (Vega mag) in the F130N filter, a brightness corresponding to the hydrogen-burning limit mass (M ≃ 0.072 M⊙) at ∼1 Myr. Of these, however, only 742 sources have a negative F130M-F139N color index, indicative of the presence of H2O vapor in absorption, and can therefore be classified as bona fide M and L dwarfs, with effective temperatures T ≲ 2850 K at an assumed 1 Myr cluster age. On our color-magnitude diagram (CMD), this population of sources with H2O absorption appears clearly distinct from the larger background population of highly reddened stars and galaxies with positive F130M-F139N color index and can be traced down to the sensitivity limit of our survey, m 130 ≃ 21.5, corresponding to a 1 Myr old ≃3 MJup planetary-mass object under about 2 mag of visual extinction. Theoretical models of the BT-Settl family predicting substellar isochrones of 1, 2, and 3 Myr down to ∼1 MJup fail to reproduce the observed H2O color index at M ≲ 20 MJup. We perform a Bayesian analysis to determine extinction, mass, and effective temperature of each substellar member of our sample, together with its membership probability.
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| 41. |
- Sabbi, E., et al.
(författare)
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The Resolved Stellar Populations in the LEGUS Galaxies
- 2018
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 235:1
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Tidskriftsartikel (refereegranskat)abstract
- The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in 5 bands from the near-UV to the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. Photometric catalogs and mosaicked images for all filters are available for download. We present optical and near-UV color-magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color-magnitude diagrams to identify stars more massive than 14 Me, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the timescale for evaporation of unbound structures is comparable or longer than 10 Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems.
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| 42. |
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| 43. |
- Welch, Brian, et al.
(författare)
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A highly magnified star at redshift 6.2
- 2022
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 603:7903, s. 815-818
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Tidskriftsartikel (refereegranskat)abstract
- Galaxy clusters magnify background objects through strong gravitational lensing. Typical magnifications for lensed galaxies are factors of a few but can also be as high as tens or hundreds, stretching galaxies into giant arcs(1,2). Individual stars can attain even higher magnifications given fortuitous alignment with the lensing cluster. Recently, several individual stars at redshifts between approximately 1 and 1.5 have been discovered, magnified by factors of thousands, temporarily boosted by microlensing(3-6). Here we report observations of a more distant and persistent magnified star at a redshift of 6.2 +/- 0.1, 900 million years after the Big Bang. This star is magnified by a factor of thousands by the foreground galaxy cluster lens WHL0137-08 (redshift 0.566), as estimated by four independent lens models. Unlike previous lensed stars, the magnification and observed brightness (AB magnitude, 27.2) have remained roughly constant over 3.5 years of imaging and follow-up. The delensed absolute UV magnitude, -10 +/- 2, is consistent with a star of mass greater than 50 times the mass of the Sun. Confirmation and spectral classification are forthcoming from approved observations with the James Webb Space Telescope.
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| 44. |
- Welch, Brian, et al.
(författare)
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JWST Imaging of Earendel, the Extremely Magnified Star at Redshift z=6.2
- 2022
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Ingår i: Astrophysical Journal Letters. - : Institute of Physics (IOP). - 2041-8205 .- 2041-8213. ; 940
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Tidskriftsartikel (refereegranskat)abstract
- The gravitationally lensed star WHL 0137-LS, nicknamed Earendel, was identified with a photometric redshift z (phot) = 6.2 +/- 0.1 based on images taken with the Hubble Space Telescope. Here we present James Webb Space Telescope (JWST) Near Infrared Camera images of Earendel in eight filters spanning 0.8-5.0 mu m. In these higher-resolution images, Earendel remains a single unresolved point source on the lensing critical curve, increasing the lower limit on the lensing magnification to mu > 4000 and restricting the source plane radius further to r < 0.02 pc, or similar to 4000 au. These new observations strengthen the conclusion that Earendel is best explained by an individual star or multiple star system and support the previous photometric redshift estimate. Fitting grids of stellar spectra to our photometry yields a stellar temperature of T (eff) similar to 13,000-16,000 K, assuming the light is dominated by a single star. The delensed bolometric luminosity in this case ranges from log(L)=5.8 L-theta, which is in the range where one expects luminous blue variable stars. Follow-up observations, including JWST NIRSpec scheduled for late 2022, are needed to further unravel the nature of this object, which presents a unique opportunity to study massive stars in the first billion years of the universe.
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