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- Keller, H., et al.
(författare)
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Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta
- 2007
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Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 187:1, s. 87-103
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Tidskriftsartikel (refereegranskat)abstract
- The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impactprojectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showedregular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness ofTempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structureswere created by the impact. Most of the material moved with ∼200 m s−1 . Much of it left the comet in the form of icy grains which sublimatedand fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet(4.5–9 × 106 kg of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions withgas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations ofthe density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain.
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| 3. |
- Marks, M. A. W., et al.
(författare)
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Sodic pyroxene and sodic amphibole as potential reference materials for in situ lithium isotope determinations by SIMS
- 2008
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Ingår i: Geostandards and Geoanalytical Research. - 1639-4488. ; 32:3, s. 295-310
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Tidskriftsartikel (refereegranskat)abstract
- Two large pegmatitic crystals of sodic pyroxene (aegirine) and sodic amphibole (arfvedsonite) from the agpaitic igneous Ilimaussaq Complex, south Greenland were found to be suitable as reference materials for in situ Li isotope determinations. Lithium concentrations determined by SIMS and micro-drilled material analysed by MC-ICP-MS generally agreed within analytical uncertainty. The arfvedsonite crystal was homogeneous with [Li] = 639 +/- 51 mu g g(-1) (2s, n = 69, MC-ICP-MS and SIMS results). The aegirine crystal shows strongly developed sector zoning, which is a common feature of aegirines. Using qualitative element mapping techniques (EPMA), the homogeneous core of the crystal was easily distinguished from the outermost sectors of the crystals. The core had a mean [Li] of 47.6 +/- 3.6 mu g g(-1) (2s, n = 33) as determined by SIMS. The seven micro-drilled regions measured by solution MC-ICP-MS returned slightly lower concentrations (41-46 mu g g(-1)), but still overlap with the SIMS data within uncertainty. Based on MC-ICP-MS and SIMS analyses, the variation in delta(7)Li was about 1 parts per thousand in each of the two crystals, which is smaller than that in widely used glass reference materials, making these two samples suitable to serve as reference materials. There was, however, a significant offset between the results of MC-ICP-MS and SIMS. The latter deviated from the MC-ICP-MS results by -6.0 +/- 1.9 parts per thousand (2s) for the amphibole and by -3.9 +/- 1.9 parts per thousand (2s) for the aegirine. This indicates the presence of a significant matrix effect in SIMS determinations of Li isotopes for amphibole and pyroxene relative to the basalt glasses used for calibration. Based on the MC-ICP-MS results, mean delta(7)Li values of +0.7 +/- 1.2 parts per thousand (2s, n = 10) for the arfvedsonite crystal and of -3.7 +/- 1.2 parts per thousand (2s, n = 7) for the core of the aegirine crystal were calculated. Adopting these values, SIMS users can correct for the specific IMF (instrumental mass fractionation) of the ion probe used. We propose that these two crystals serve as reference materials for in situ Li isotope determinations by SIMS and pieces of these two crystals are available from the first author upon request.
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| 4. |
- Wiese, Mie, et al.
(författare)
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Influence of cross-sectional temporomandibular joint (TMJ) tomography on diagnosis and management of patients with temporomandibular disorders (TMD)
- 2008
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Konferensbidrag (refereegranskat)abstract
- Objectives: To describe changes in diagnosis and management of TMD patients after radiographic examination and to evaluate the associations between specific TMJ tomographic findings and changes in management. Methods: 204 adult patients (48 males, 156 females, mean age 40 years) with TMJ pain/sounds or problems with mandibular motion were examined according to the Research Diagnostic Criteria (RDC/TMD) by one of six calibrated orofacial pain specialists. Diagnoses and management strategy reached without the aid of radiographs were recorded. It was possible to select from seven management categories (pharmacology, physiotherapy, psychological, occlusal stabilization, surgical, other examinations and referrals) each with a number of sub-categories. Bilateral sagittal corrected TMJ tomograms in closed position were obtained using conventional film in a Cranex Tome or a Scanora tomographic X-ray unit. The tomograms were assessed for the presence of flattening, erosion, osteophyte and sclerosis in the TMJ components and the condyle-to-mandibular fossa relation by one of five calibrated oral radiologists blinded to the clinical diagnosis and initial management strategy. After gaining access to the results from the radiographic examination the orofacial pain specialists re-evaluated their diagnoses and management strategy. All changes were calculated. Logistic regression analyses (with odds ratio (OR) and significance level (p)) were performed with changes in management as the dependent variable and with age and radiographic findings as the independent variables. Results: 41% of the clinical arthralgia diagnoses were changed into osteoarthritis after radiographic examination and the number of osteoarthrosis diagnoses increased with 200% (from 13 to 39). One or more changes in the management strategy were found for 27% (55) of the patients. Most often changes occurred in pharmacology and physiotherapy (29 and 28 patients respectively) followed by changes in psychological (13 patients), occlusal stabilization (8 patients), referrals (7 patients), other examinations (6 patients) and surgical (2 patients). For pharmacology, physiotherapy and psychological the changes were adjustments within the sub-categories in 51 out of 70 patients. For the other management categories most of the changes were addition or omission of the management category (in 20 out of 23 patients). The chance of “any change” in management (removal or addition of one or more sub-categories in one or more management categories) was more than twice as high with a finding of flattening (OR=2.28) and erosion (OR=2.03) compared to not having these radiographic findings. Increased chance of “any change” in management was also found with >1 radiographic finding (regardless of type) (OR=2.64) compared to having no radiographic findings. The chance of change in pharmacology was increased more than three times with erosion (OR=3.60) and more than two times with flattening (OR=2.56). The chance of change in physiotherapy was increased with >1 radiographic finding (OR=2.79). No statistically significant (p≤0.05) associations between osteophyte, sclerosis and age and changes in management were found. Conclusion: 27% of the patients had changes in management after radiographic examination. Radiographic findings did increase the chance of changes in management. However, as the changes were mostly adjustments in sub-categories radiography may have a minor impact on management of most TMD patients.
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