| 1. |
- Coustenis, A., et al.
(författare)
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TandEM : Titan and Enceladus mission
- 2009
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 893-946
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Tidskriftsartikel (refereegranskat)abstract
- TandEM was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (MontgolfiSre) and possibly several landing probes to be delivered through the atmosphere.
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| 2. |
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| 3. |
- van de Pol, L. A., et al.
(författare)
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White matter hyperintensities and medial temporal lobe atrophy in clinical subtypes of mild cognitive impairment: the DESCRIPA study
- 2009
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Ingår i: Journal of Neurology, Neurosurgery and Psychiatry. - : BMJ. - 1468-330X .- 0022-3050. ; 80:10, s. 1069-1074
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Tidskriftsartikel (refereegranskat)abstract
- Background: Clinical subtypes of mild cognitive impairment (MCI) may represent different underlying aetiologies. Methods: This European, multicentre, memory clinic based study (DESCRIPA) of non-demented subjects investigated whether MCI subtypes have different brain correlates on MRI and whether the relation between subtypes and brain pathology is modified by age. Using visual rating scales, medial temporal lobe atrophy (MTA) (0-4) and white matter hyperintensities (WMH) (0-30) were assessed. Results: Severity of MTA differed between MCI subtypes (p < 0.001), increasing from a mean of 0.8 (SD 0.7) in subjective complaints (n = 77) to 1.3 (0.8) in non-amnestic MCI (n = 93), and from 1.4 (0.9) in single domain amnestic MCI (n = 70) to 1.7 (0.9) in multiple domain amnestic MCI (n = 89). The association between MCI subtype and MTA was modified by age and mainly present in subjects >70 years of age. Severity of WMH did not differ between MCI subtypes (p = 0.21). However, the combination of MTA and WMH differed between MCI subtypes (p = 0.02) Conclusion: We conclude that MCI subtypes may have different brain substrates, especially in older subjects. Isolated MTA was mainly associated with amnestic MCI subtypes, suggesting AD as the underlying cause. In non-amnestic MCI, the relatively higher prevalence of MTA in combination with WMH may suggest a different pathophysiological origin.
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| 4. |
- Lammer, H., et al.
(författare)
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What makes a planet habitable?
- 2009
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Ingår i: The Astronomy and Astrophysics Review. - : Springer Science and Business Media LLC. - 0935-4956 .- 1432-0754. ; 17:2, s. 181-249
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Forskningsöversikt (refereegranskat)abstract
- This work reviews factors which are important for the evolution of habitable Earth-like planets such as the effects of the host star dependent radiation and particle fluxes on the evolution of atmospheres and initial water inventories. We discuss the geodynamical and geophysical environments which are necessary for planets where plate tectonics remain active over geological time scales and for planets which evolve to one-plate planets. The discoveries of methane-ethane surface lakes on Saturn's large moon Titan, subsurface water oceans or reservoirs inside the moons of Solar System gas giants such as Europa, Ganymede, Titan and Enceladus and more than 335 exoplanets, indicate that the classical definition of the habitable zone concept neglects more exotic habitats and may fail to be adequate for stars which are different from our Sun. A classification of four habitat types is proposed. Class I habitats represent bodies on which stellar and geophysical conditions allow Earth-analog planets to evolve so that complex multi-cellular life forms may originate. Class II habitats includes bodies on which life may evolve but due to stellar and geophysical conditions that are different from the class I habitats, the planets rather evolve toward Venus- or Mars-type worlds where complex life-forms may not develop. Class III habitats are planetary bodies where subsurface water oceans exist which interact directly with a silicate-rich core, while class IV habitats have liquid water layers between two ice layers, or liquids above ice. Furthermore, we discuss from the present viewpoint how life may have originated on early Earth, the possibilities that life may evolve on such Earth-like bodies and how future space missions may discover manifestations of extraterrestrial life.
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| 5. |
- Looi, JC, et al.
(författare)
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Putaminal volume in frontotemporal lobar degeneration and Alzheimer disease: differential volumes in dementia subtypes and controls
- 2009
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Ingår i: American Journal of Neuroradiology. - 0195-6108 .- 1936-959X. ; 30:8, s. 1552-1560
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Frontostriatal (including the putamen) circuit-mediated cognitive dysfunction has been implicated in frontotemporal lobar degeneration (FTLD), but not in Alzheimer disease (AD) or healthy aging. We sought to assess putaminal volume as a measure of the structural basis of relative frontostriatal dysfunction in these groups. MATERIALS AND METHODS: We measured putaminal volume in FTLD subtypes: frontotemporal dementia (FTD, n = 12), semantic dementia (SD, n = 13), and progressive nonfluent aphasia (PNFA, n = 9) in comparison with healthy controls (n = 25) and patients with AD (n = 18). Diagnoses were based on accepted clinical criteria. We conducted manual volume measurement of the putamen blinded to the diagnosis on T1 brain MR imaging by using a standardized protocol. RESULTS: Paired t tests (P < .05) showed that the left putaminal volume was significantly larger than the right in all groups combined. Multivariate analysis of covariance with a Bonferroni correction was used to assess statistical significance among the subject groups (AD, FTD, SD, PNFA, and controls) as independent variables and right/left putaminal volumes as dependent variables (covariates, age and intracranial volume; P < .05). The right putamen in FTD was significantly smaller than in AD and controls; whereas in SD, it was smaller compared with controls with a trend toward being smaller than in AD. There was also a trend toward the putamen in the PNFA being smaller than that in controls and in patients with AD. Across the groups, there was a positive partial correlation between putaminal volume and Mini-Mental State Examination (MMSE). CONCLUSIONS: Right putaminal volume was significantly smaller in FTD, the FTLD subtype with the greatest expected frontostriatal dysfunction; whereas in SD and PNFA, it showed a trend towards being smaller, consistent with expectation, compared to controls and AD; and in SD, compared with AD and controls. Putaminal volume weakly correlated with MMSE.
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| 6. |
- Ryberg, C, et al.
(författare)
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White matter changes contribute to corpus callosum atrophy in the elderly: the LADIS study.
- 2008
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Ingår i: AJNR. American journal of neuroradiology. - 1936-959X. ; 29:8, s. 1498-504
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: The corpus callosum (CC) is the most important structure involved in the transmission of interhemispheric information. The aim of this study was to investigate the potential correlation between regional age-related white matter changes (ARWMC) and atrophy of CC in elderly subjects. MATERIALS AND METHODS: In 578 subjects with ARWMC from the Leukoaraiosis And DISability (LADIS) study, the cross-sectional area of the CC was automatically segmented on the normalized midsagittal MR imaging section and subdivided into 5 regions. The ARWMC volumes were measured quantitatively by using a semiautomated technique and segmented into 6 brain regions. RESULTS: Significant correlation between the area of the rostrum and splenium regions of the CC and the ARWMC load in most brain regions was identified. This correlation persisted after correction for global atrophy. CONCLUSION: Increasing loads of ARWMC volume were significantly correlated with atrophy of the CC and its subregions in nondisabled elderly subjects with leukoaraiosis. However, the pattern of correlation between CC subregions and ARWMC was not specifically related to the topographic location of ARWMC. The results suggest that ARWMC may lead to a gradual loss of CC tissue.
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| 7. |
- Visser, P. J., et al.
(författare)
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Development of screening guidelines and clinical criteria for predementia Alzheimer's disease
- 2008
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Ingår i: Neuroepidemiology. - : S. Karger AG. - 1423-0208 .- 0251-5350. ; 30:4, s. 254-265
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Tidskriftsartikel (refereegranskat)abstract
- Background: There is an urgent need to identify subjects with Alzheimer's disease (AD) in the predementia phase, but validated diagnostic approaches are currently lacking. In this paper, we present the background, design and methods of a study, which aims to develop clinical criteria for predementia AD. We also present baseline characteristics of the subjects included. The study was part of the multicentre DESCRIPA project, which is being conducted within the network of the European Alzheimer's Disease Consortium. Methods: Clinical criteria will be based on a prospective cohort study of non-demented subjects older than 55 years and referred to a memory clinic. At baseline, a number of markers and risk factors for AD were collected, including demographic variables, measures of performance in activities of daily living, cognitive, neuroimaging and genetic markers, and serum and cerebrospinal fluid markers. Subjects will be reassessed annually for 2 - 3 years, and we will evaluate which combination of variables best predicts AD-type dementia at follow-up. Results: Between 2003 and 2005, 881 subjects were included from 20 memory clinics. Subjects were on average 70.3 years old, and had 10.4 years of education. The average score on the Mini-Mental State Examination was 27.4.
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| 8. |
- Baezner, H, et al.
(författare)
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Association of gait and balance disorders with age-related white matter changes: the LADIS study.
- 2008
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Ingår i: Neurology. - : Ovid Technologies (Wolters Kluwer Health). - 1526-632X .- 0028-3878. ; 70:12, s. 935-42
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: In the Leukoaraiosis and Disability (LADIS) Study, 11 European centers are evaluating the role of age-related white matter changes (ARWMC) as an independent determinant of the transition to disability in the elderly (65 to 84 years). We aimed at determining the influence of ARWMC on different objective measures of gait and balance. METHODS: Six hundred thirty-nine nondisabled individuals were prospectively enrolled and are being followed-up for 3 years. Subjects are graded in three standardized categories of ARWMC (mild, moderate, and severe) according to central MRI reading. Quantitative tests of gait and balance include the Short Physical Performance Battery (SPPB; range: 0 [poor] to 12 [normal]), a timed 8-m walk, and a timed single leg stance test. RESULTS: In cross-sectional analysis, deficiencies in gait and balance performance were correlated with the severity of ARWMC (SPPB: 10.2 +/- 2.1 in the mild, 9.9 +/- 2.0 in the moderate, 8.9 +/- 2.6 in the severe group; p < 0.001). Walking speed correlated with the severity of ARWMC (1.24 +/- 0.28 m/second in the mild, 1.18 +/- 0.32 m/second in the moderate, and 1.09 +/- 0.31 m/second in the severe group; p < 0.001). Balance was best in individuals with mild ARWMC (single leg stance time: 18.9 +/- 10.8 seconds) compared with moderate and severe ARWMC (16.4 +/- 10.8 and 13.6 +/- 11.2 seconds) (p < 0.001). Physically inactive individuals had a higher risk of a pathologic SPPB score (moderate vs mild ARWMC: odds ratio 1.60, 95% CI 1.02 to 2.52; severe vs mild ARWMC: odds ratio 1.75, 95% CI 1.09 to 2.80). CONCLUSIONS: Our findings support a strong association between the severity of age-related white matter changes and the severity of gait and motor compromise. Physical activity might have the potential to reduce the risk of limitations in mobility.
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| 9. |
- Blahak, C, et al.
(författare)
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Deep frontal and periventricular age related white matter changes but not basal ganglia and infratentorial hyperintensities are associated with falls: cross sectional results from the LADIS study.
- 2009
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Ingår i: Journal of neurology, neurosurgery, and psychiatry. - : BMJ. - 1468-330X .- 0022-3050. ; 80:6, s. 608-13
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Global age related white matter changes (ARWMC) are associated with progressive gait disturbances and falls, hypothesised to result from interruptions of cortico-subcortical circuits controlling balance, posture and locomotion. METHODS: The location of ARWMC in a large cohort of elderly non-disabled individuals with reported falls was analysed, using the cross sectional data of the Leukoaraiosis and Disability (LADIS) study. Detailed anatomical distributions of ARWMC assessed by MRI studies were analysed with respect to falls and balance performance. RESULTS: The severity of global ARWMC was significantly associated with a history of falls in the year prior to study inclusion (22.2% in the mild, 31.6% in the moderate and 37.3% in the severe ARWMC group according to the Fazekas scale; p = 0.002). Analysing the anatomical distribution of ARWMC, using the semiquantitative Scheltens scale, in multivariate analysis, periventricular (p = 0.006) and frontal deep (p = 0.033) ARWMC were independently associated with falls. Furthermore, logistic regression identified frontal deep (p = 0.003) ARWMC, but not basal ganglia and infratentorial hyperintensities, as significantly associated with balance disturbances. CONCLUSION: The association of frontal and periventricular ARWMC with falls supports the hypothesis that interruption of frontal subcortical motor circuits lead to balance disturbances and hence to an increased risk for falls in ARWMC.
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