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- Panuzzo, P., et al.
(author)
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Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry
- 2024
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 686
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Journal article (peer-reviewed)abstract
- Context. Gravitational waves from black-hole (BH) merging events have revealed a population of extra-galactic BHs residing in short-period binaries with masses that are higher than expected based on most stellar evolution models-And also higher than known stellar-origin black holes in our Galaxy. It has been proposed that those high-mass BHs are the remnants of massive metal-poor stars.Aims. Gaia astrometry is expected to uncover many Galactic wide-binary systems containing dormant BHs, which may not have been detected before. The study of this population will provide new information on the BH-mass distribution in binaries and shed light on their formation mechanisms and progenitors.Methods. As part of the validation efforts in preparation for the fourth Gaia data release (DR4), we analysed the preliminary astrometric binary solutions, obtained by the Gaia Non-Single Star pipeline, to verify their significance and to minimise false-detection rates in high-mass-function orbital solutions.Results. The astrometric binary solution of one source, Gaia BH3, implies the presence of a 32.70a ±a 0.82aM- BH in a binary system with a period of 11.6 yr. Gaia radial velocities independently validate the astrometric orbit. Broad-band photometric and spectroscopic data show that the visible component is an old, very metal-poor giant of the Galactic halo, at a distance of 590 pc.Conclusions. The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known thus far. The low metallicity of the star companion supports the scenario that metal-poor massive stars are progenitors of the high-mass BHs detected by gravitational-wave telescopes. The Galactic orbit of the system and its metallicity indicate that it might belong to the Sequoia halo substructure. Alternatively, and more plausibly, it could belong to the ED-2 stream, which likely originated from a globular cluster that had been disrupted by the Milky Way.
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- Andriuta, Daniela, et al.
(author)
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Perivascular spaces, plasma GFAP, and speeded executive function in neurodegenerative diseases
- 2024
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In: ALZHEIMERS & DEMENTIA. - 1552-5260 .- 1552-5279.
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Journal article (peer-reviewed)abstract
- INTRODUCTIONWe investigated the effect of perivascular spaces (PVS) volume on speeded executive function (sEF), as mediated by white matter hyperintensities (WMH) volume and plasma glial fibrillary acidic protein (GFAP) in neurodegenerative diseases.METHODSA mediation analysis was performed to assess the relationship between neuroimaging markers and plasma biomarkers on sEF in 333 participants clinically diagnosed with Alzheimer's disease/mild cognitive impairment, frontotemporal dementia, or cerebrovascular disease from the Ontario Neurodegenerative Disease Research Initiative.RESULTSPVS was significantly associated with sEF (c = -0.125 +/- 0.054, 95% bootstrap confidence interval [CI] [-0.2309, -0.0189], p = 0.021). This effect was mediated by both GFAP and WMH.DISCUSSIONIn this unique clinical cohort of neurodegenerative diseases, we demonstrated that the effect of PVS on sEF was mediated by the presence of elevated plasma GFAP and white matter disease. These findings highlight the potential utility of imaging and plasma biomarkers in the current landscape of therapeutics targeting dementia.HIGHLIGHTS Perivascular spaces (PVS) and white matter hyperintensities (WMH) are imaging markers of small vessel disease. Plasma glial fibrillary protein acidic protein (GFAP) is a biomarker of astroglial injury. PVS, WMH, and GFAP are relevant in executive dysfunction from neurodegeneration. PVS's effect on executive function was mediated by GFAP and white matter disease.
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- Farrow, R., et al.
(author)
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GO-GN Conceptual Frameworks Guide
- 2021
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Book (other academic/artistic)abstract
- If you’re a doctoral researcher (in any discipline) or someone who produces research in a professional capacity you’ve perhaps encountered the phrase “conceptual framework”. Sometimes a whole chapter of a Ph.D or Ed.D might be given over to investigating the relevance of different frameworks for an area of inquiry, or to synthesizing several frameworks together to ground the approach taken to answering a specific research question. Alternatively, you might not have heard much mention of conceptual frameworks or how they relate to what you are trying to achieve with your research. A conceptual framework brings together a set of ideas and articulates the different concepts that will be used in a study or research project. Because this is highly contextual - and often specific to a particular research question or approach - there aren’t really any general rules that cover how to do this. In addition, there is a lot of ambiguity and impreciseness in the language used to describe this stuff. Sometimes people talk about theoretical frameworks, or models, or a ‘theory of action’ that guides their research project. But do these mean different things? And are there differences between disciplines? In an empirical project the conceptual framework might be used to determine the kinds of questions to ask in a survey, or which data points to collect and focus on. A conceptual framework might be used to generate a hypothesis that is to be tested, or to facilitate the interpretation of results. On the qualitative side a conceptual framework might be used to provide the right kinds of descriptions at different stages of the research process; to identify or explore categories of analysis; or to guide and refine the conclusions drawn by a study. All of these things can happen in a single project! Given the importance and centrality of these frameworks, it might be surprising to learn that relatively little has been written about using them in research. There’s certainly a lot less published about this than research methods or methodology, for instance. (Though different methods often come with specific conceptual frameworks built in or with a more obvious alignment). So, to start making sense of all this we begin by looking at some of the papers that offer systematic guidance or understanding of the role of conceptual frameworks in research. As this guide progresses we’ll bring in perspectives from GO-GN members on their experiences with developing and using conceptual frameworks.
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- Wood, Madeline E., et al.
(author)
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Sex differences in associations between APOE ε2 and longitudinal cognitive decline
- 2023
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In: Alzheimer's and Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 19:10, s. 4651-4661
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Journal article (peer-reviewed)abstract
- INTRODUCTION: We examined whether sex modifies the association between APOE ε2 and cognitive decline in two independent samples. METHODS: We used observational data from cognitively unimpaired non-Hispanic White (NHW) and non-Hispanic Black (NHB) adults. Linear mixed models examined interactive associations of APOE genotype (ε2 or ε4 carrier vs. ε3/ε3) and sex on cognitive decline in NHW and NHB participants separately. RESULTS: In both Sample 1 (N = 9766) and Sample 2 (N = 915), sex modified the association between APOE ε2 and cognitive decline in NHW participants. Specifically, relative to APOE ε3/ε3, APOE ε2 protected against cognitive decline in men but not women. Among APOE ε2 carriers, men had slower decline than women. Among APOE ε3/ε3 carriers, cognitive trajectories did not differ between sexes. There were no sex-specific associations of APOE ε2 with cognition in NHB participants (N = 2010). DISCUSSION: In NHW adults, APOE ε2 may protect men but not women against cognitive decline. Highlights: We studied sex-specific apolipoprotein E (APOE) ε2 effects on cognitive decline. In non-Hispanic White (NHW) adults, APOE ε2 selectively protects men against decline. Among men, APOE ε2 was more protective than APOE ε3/ε3. In women, APOE ε2 was no more protective than APOE ε3/ε3. Among APOE ε2 carriers, men had slower decline than women. There were no sex-specific APOE ε2 effects in non-Hispanic Black (NHB) adults.
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- Choi, Seo Eun, et al.
(author)
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Development and validation of language and visuospatial composite scores in ADNI
- 2020
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In: Alzheimer's and Dementia: Translational Research and Clinical Interventions. - : Wiley. - 2352-8737. ; 6:1
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Journal article (peer-reviewed)abstract
- Introduction: Composite scores may be useful to summarize overall language or visuospatial functioning in studies of older adults. Methods:We used item response theory to derive composite measures for language (ADNI-Lan) and visuospatial functioning (ADNI-VS) from the cognitive battery administered in the Alzheimer’s Disease Neuroimaging Initiative (ADNI). We evaluated the scores among groups of people with normal cognition, mild cognitive impairment (MCI), and Alzheimer’s disease (AD) in terms of responsiveness to change, association with imaging findings, and ability to differentiate between MCI participants who progressed to AD dementia and those who did not progress. Results: ADNI-Lan andADNI-VSwere able to detect change over time and predict conversion fromMCI toAD. Theywere associated with most of the pre-specified magnetic resonance imaging measures. ADNI-Lan had strong associations with a cerebrospinal fluid biomarker pattern. Discussion: ADNI-Lan and ADNI-VS may be useful composites for language and visuospatial functioning in ADNI.
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- Meng, Y., et al.
(author)
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Blood-brain barrier opening of the default mode network in Alzheimer's disease with magnetic resonance-guided focused ultrasound
- 2023
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In: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 146:3, s. 865-872
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Journal article (peer-reviewed)abstract
- In an open-label single-arm trial, Meng et al. investigate the feasibility and tolerability of opening the blood-brain barrier in the default mode network with MR-guided focused ultrasound in patients with Alzheimer's disease. The study intervention led to local amyloid reduction on PET imaging, but no change in disease-specific markers in plasma or CSF. The blood-brain barrier (BBB) protects the brain but is also an important obstacle for the effective delivery of therapeutics in Alzheimer's disease and other neurodegenerative disorders. Transcranial magnetic resonance-guided focused ultrasound (MRgFUS) has been shown to reversibly disrupt the BBB. However, treatment of diffuse regions across the brain along with the effect on Alzheimer's disease relevant pathology need to be better characterized. This study is an open-labelled single-arm trial (NCT04118764) to investigate the feasibility of modulating BBB permeability in the default mode network and the impact on cognition, amyloid and tau pathology as well as BBB integrity. Nine participants [mean age 70.2 +/- 7.2 years, mean Mini-Mental State Examination (MMSE) 21.9] underwent three biweekly procedures with follow-up visits up to 6 months. The BBB permeability of the bilateral hippocampi, anterior cingulate cortex and precuneus was transiently increased without grade 3 or higher adverse events. Participants did not experience worsening trajectory of cognitive decline (ADAS-cog11, MMSE). Whole brain vertex-based analysis of the F-18-florbetaben PET imaging demonstrated clusters of modest SUVR reduction in the right parahippocampal and inferior temporal lobe. However, CSF and blood biomarkers did not demonstrate any amelioration of Alzheimer's disease pathology (P-tau181, amyloid-beta 42/40 ratio), nor did it show persistent BBB dysfunction (plasma PDGFRbeta and CSF-to-plasma albumin ratio). This study provides neuroimaging and fluid biomarker data to characterize the safety profile of MRgFUS BBB modulation in neurodegeneration as a potential strategy for enhanced therapeutic delivery.
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