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- Bockelee-Morvan, D., et al.
(author)
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Composition and thermal properties of Ganymede's surface from JWST/NIRSpec and MIRI observations
- 2024
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 681, s. A27-
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Journal article (peer-reviewed)abstract
- Context. We present the first spectroscopic observations of Ganymede by the James Webb Space Telescope undertaken in August 2022 as part of the proposal "ERS observations of the Jovian system as a demonstration of JWST's capabilities for Solar System science".Aims. We aimed to investigate the composition and thermal properties of the surface, and to study the relationships of ice and non-water-ice materials and their distribution.Methods. NIRSpec IFU (2.9-5.3 mu m) and MIRI MRS (4.9-28.5 mu m) observations were performed on both the leading and trailing hemispheres of Ganymede, with a spectral resolution of similar to 2700 and a spatial sampling of 0.1 to 0.17 '' (while the Ganymede size was similar to 1.68 ''). We characterized the spectral signatures and their spatial distribution on the surface. The distribution of brightness temperatures was analyzed with standard thermophysical modeling including surface roughness.Results. Reflectance spectra show signatures of water ice, CO2, and H2O2. An absorption feature at 5.9 mu m, with a shoulder at 6.5 mu m, is revealed, and is tentatively assigned to sulfuric acid hydrates. The CO2 4.26-mu m band shows latitudinal and longitudinal variations in depth, shape, and position over the two hemispheres, unveiling different CO2 physical states. In the ice-rich polar regions, which are the most exposed to Jupiter's plasma irradiation, the CO2 band is redshifted with respect to other terrains. In the boreal region of the leading hemisphere, the CO2 band is dominated by a high wavelength component at similar to 4.27 mu m, consistent with CO2 trapped in amorphous water ice. At equatorial latitudes (and especially on dark terrains), the observed band is broader and shifted toward the blue, suggesting CO2 adsorbed on non-icy materials, such as minerals or salts. Maps of the H2O Fresnel peak area correlate with Bond albedo maps and follow the distribution of water ice inferred from H2O absorption bands. Amorphous ice is detected in the ice-rich polar regions, and is especially abundant on the northern polar cap of the leading hemisphere. Leading and trailing polar regions exhibit different H2O, CO2, and H2O2 spectral properties. However, in both hemispheres the north polar cap ice appears to be more processed than the south polar cap. A longitudinal modification of the H2O ice molecular structure and/or nanometer- and micrometer-scale texture, of diurnal or geographic origin, is observed in both hemispheres. Ice frost is tentatively observed on the morning limb of the trailing hemisphere, which possibly formed during the night from the recondensation of water subliming from the warmer subsurface. Reflectance spectra of the dark terrains are compatible with the presence of Na- and Mg-sulfate salts, sulfuric acid hydrates, and possibly phyllosilicates mixed with fine-grained opaque minerals, with a highly porous texture. Latitude and local time variations of the brightness temperatures indicate a rough surface with mean slope angles of 15 degrees-25 degrees and a low thermal inertia Gamma = 20 - 40 J m(-2) s(-0.5) K-1, consistent with a porous surface, with no obvious difference between the leading and trailing sides.
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| 2. |
- Brinkman, D. M., et al.
(author)
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Autologous stem cell transplantation in children with severe progressive systemic or polyarticular juvenile idiopathic arthritis: long-term follow-up of a prospective clinical trial
- 2007
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In: Arthritis Rheum. - : Wiley. - 0004-3591. ; 56:7, s. 2410-21
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Journal article (peer-reviewed)abstract
- OBJECTIVE: To assess the safety and efficacy of intensive immunosuppression followed by T cell-depleted autologous hematopoietic stem cell transplantation (ASCT) for induction of disease remission in children with refractory progressive juvenile idiopathic arthritis (JIA). METHODS: Twenty-two patients with progressive refractory JIA were followed up over a median period of 80 months after pretreatment with intensive immunosuppression followed by ASCT in a multicenter, prospective, phase II clinical trial. Hematopoietic stem cells were harvested from the patients' bone marrow, depleted of T cells, and kept frozen until used for ASCT. Pretreatment of patients consisted of a combination of antithymocyte globulin, cyclophosphamide, and low-dose total body irradiation. Patients were followed up for ASCT-related complications, recovery of hematologic and immune system parameters, and disease outcomes. RESULTS: Reconstitution of hematologic values to normal range was rapid. Recovery of immune system parameters, especially normalization of CD4+, CD45RA+ naive T cells, was delayed, occurring at >/=6 months after ASCT. The prolonged period of immune deficiency resulted in a large number of viral infections and may have contributed to the development of macrophage activation syndrome (MAS), leading to death, in 2 patients. After ASCT, 8 of the 20 evaluable patients reached complete clinical remission of their JIA, 7 were partial responders, and 5 experienced a relapse of their disease (occurring 7 years after ASCT in 1 patient). Later during followup, 2 of the patients whose disease relapsed died from infections that developed after restarting immunosuppressive medication. CONCLUSION: Intensive immunosuppression followed by ASCT resulted in sustained complete remission or marked improvement in 15 of 22 patients with progressive refractory JIA. The procedure, however, is associated with significant morbidity and risk of mortality due to prolonged and severe depression of T cell immunity. After fatal complications due to MAS were observed in some patients, the protocol was amended in 1999, to ensure less profound depletion of T cells, better control of systemic disease before transplantation, antiviral prophylaxis after transplantation, and slow tapering of corticosteroids. Following these protocol modifications, no additional ASCT-related deaths were observed among the 11 patients who received the modified treatment.
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| 3. |
- de Kleer, I. M., et al.
(author)
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Autologous stem cell transplantation for refractory juvenile idiopathic arthritis: analysis of clinical effects, mortality, and transplant related morbidity
- 2004
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In: Ann Rheum Dis. - : BMJ. - 0003-4967. ; 63:10, s. 1318-26
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Journal article (peer-reviewed)abstract
- OBJECTIVE: To evaluate the safety and efficacy of autologous stem cell transplantation (ASCT) for refractory juvenile idiopathic arthritis (JIA). DESIGN: Retrospective analysis of follow up data on 34 children with JIA who were treated with ASCT in nine different European transplant centres. Rheumatological evaluation employed a modified set of core criteria. Immunological reconstitution and infectious complications were monitored at three month intervals after transplantation. RESULTS: Clinical follow up ranged from 12 to 60 months. Eighteen of the 34 patients (53%) with a follow up of 12 to 60 months achieved complete drug-free remission. Seven of these patients had previously failed treatment with anti-TNF. Six of the 34 patients (18%) showed a partial response (ranging from 30% to 70% improvement) and seven (21%) were resistant to ASCT. Infectious complications were common. There were three cases of transplant related mortality (9%) and two of disease related mortality (6%). CONCLUSIONS: ASCT in severely ill patients with JIA induces a drug-free remission of the disease and a profound increase in general wellbeing in a substantial proportion of patients, but the procedure carries a significant mortality risk. The following adjustments are proposed for future protocols: (1) elimination of total body irradiation from the conditioning regimen; (2) prophylactic administration of antiviral drugs and intravenous immunoglobulins until there is a normal CD4+ T cell count.
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