| 1. |
- Dima, Danai, et al.
(author)
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Subcortical volumes across the lifespan : Data from 18,605 healthy individuals aged 3-90 years.
- 2022
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In: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 43:1, s. 452-469
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Journal article (peer-reviewed)abstract
- Age has a major effect on brain volume. However, the normative studies available are constrained by small sample sizes, restricted age coverage and significant methodological variability. These limitations introduce inconsistencies and may obscure or distort the lifespan trajectories of brain morphometry. In response, we capitalized on the resources of the Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) Consortium to examine age-related trajectories inferred from cross-sectional measures of the ventricles, the basal ganglia (caudate, putamen, pallidum, and nucleus accumbens), the thalamus, hippocampus and amygdala using magnetic resonance imaging data obtained from 18,605 individuals aged 3-90 years. All subcortical structure volumes were at their maximum value early in life. The volume of the basal ganglia showed a monotonic negative association with age thereafter; there was no significant association between age and the volumes of the thalamus, amygdala and the hippocampus (with some degree of decline in thalamus) until the sixth decade of life after which they also showed a steep negative association with age. The lateral ventricles showed continuous enlargement throughout the lifespan. Age was positively associated with inter-individual variability in the hippocampus and amygdala and the lateral ventricles. These results were robust to potential confounders and could be used to examine the functional significance of deviations from typical age-related morphometric patterns.
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| 2. |
- Frangou, Sophia, et al.
(author)
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Cortical thickness across the lifespan : Data from 17,075 healthy individuals aged 3-90 years
- 2022
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In: Human Brain Mapping. - : John Wiley & Sons. - 1065-9471 .- 1097-0193. ; 43:1, s. 431-451
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Journal article (peer-reviewed)abstract
- Delineating the association of age and cortical thickness in healthy individuals is critical given the association of cortical thickness with cognition and behavior. Previous research has shown that robust estimates of the association between age and brain morphometry require large-scale studies. In response, we used cross-sectional data from 17,075 individuals aged 3-90 years from the Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) Consortium to infer age-related changes in cortical thickness. We used fractional polynomial (FP) regression to quantify the association between age and cortical thickness, and we computed normalized growth centiles using the parametric Lambda, Mu, and Sigma method. Interindividual variability was estimated using meta-analysis and one-way analysis of variance. For most regions, their highest cortical thickness value was observed in childhood. Age and cortical thickness showed a negative association; the slope was steeper up to the third decade of life and more gradual thereafter; notable exceptions to this general pattern were entorhinal, temporopolar, and anterior cingulate cortices. Interindividual variability was largest in temporal and frontal regions across the lifespan. Age and its FP combinations explained up to 59% variance in cortical thickness. These results may form the basis of further investigation on normative deviation in cortical thickness and its significance for behavioral and cognitive outcomes.
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| 3. |
- Kaufmann, Tobias, et al.
(author)
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Common brain disorders are associated with heritable patterns of apparent aging of the brain
- 2019
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In: Nature Neuroscience. - : Nature Publishing Group. - 1097-6256 .- 1546-1726. ; 22:10, s. 1617-
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Journal article (peer-reviewed)abstract
- Common risk factors for psychiatric and other brain disorders are likely to converge on biological pathways influencing the development and maintenance of brain structure and function across life. Using structural MRI data from 45,615 individuals aged 3-96 years, we demonstrate distinct patterns of apparent brain aging in several brain disorders and reveal genetic pleiotropy between apparent brain aging in healthy individuals and common brain disorders.
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| 4. |
- Mohammadi, Siawoosh, et al.
(author)
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Characterising the temporal evolution of fixation in human post mortem brain via linear relaxometry modelling – a marker of cross-linking?
- 2019
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In: Characterising the temporal evolution of fixation in human post mortem brain via linear relaxometry modelling – a marker of cross-linking?. ; 27
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Conference paper (peer-reviewed)abstract
- MRI-based biophysical models are typically validated by comparison to ex-vivo histology of fixed tissue. The fixation process itself and the accompanied autolysis processes strongly modify tissue composition, and lead to MR signal changes, making the validation of biophysical models for in vivo MRI particularly challenging. To better understand the temporal evolution of the fixation process within the whole brain and its influence on MRI parameters, we monitor the temporal evolution of the fixation process of a whole human post-mortem brain using the linear relaxometry model across 15 time-points comprised of one unfixed, in-situ MRI scan and 14 ex-vivo MRI scans at different stages of the fixation process (days 1-93).
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| 5. |
- Stevens, Renaud, 1972-, et al.
(author)
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High-speed visible VCSEL for POF data links
- 2000
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In: Proc. SPIE 3946, SPIE’s Optoelectronics 2000, Photonics West, San Jose, US, January 2000.. - : SPIE. ; , s. 88-94
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Conference paper (peer-reviewed)abstract
- We report on two AlGaInP-based visible VCSEL designs based on different current confinement schemes, ion implantation and selective oxidation, and we compare the respective performances with a particular interest on the modulation properties. The implanted device operated continuous wave (CW) up to 40 degrees Celsius. Threshold current of 7 mA, threshold voltage of 2.5 V and maximum optical power of 0.3 mW were measured at room temperature. The small signal modulation responses were fitted using a 3-poles model, allowing the estimation of various parameters such as resonance frequency, damping factor and parasitic cut-off. The maximum 3dB- bandwidth was shown to be 2.1 GHz, limited both by thermal and parasitic effects. 'Error-free' transmission at 1 Gb/s was demonstrated through 50-meter of graded-index POF. The selectivity oxidized devices achieve much higher output power (1.8 mW for the 10 micrometer opening diameter) with threshold current as low a 1.5 mA and threshold voltage of 2.1 V at room temperature, and operate CW up to 49 degrees Celsius. The maximum 3 dB-bandwidth was 4.5 GHz. Modulation current efficiency factor up to 2.8 GHz/(root)[mA] was measured.
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| 6. |
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| 7. |
- Öberg, Magnus, et al.
(author)
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Increased modulation bandwidth up to 20 GHz of a detuned-loaded DBR laser
- 1994
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In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 6:2, s. 161-163
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Journal article (peer-reviewed)abstract
- A small signal amplitude modulation bandwidth of 20 GHz has been obtained with a three-section tunable DBR laser fabricated with semi-insulating current blocking layers grown by hydride VPE. The modulation bandwidth and laser linewidth are strongly dependent on the position of the lasing mode relative to the Bragg reflection peak.
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