123 research outputs found
Can LC structural and functional changes serve as a biomarker for Alzheimer’s diseaseA systematic review
No full textAlzheimer’s Disease (AD) is a chronic and progressive neurodegenerative disorder and the most common cause of dementia in older adults. It is characterized by gradual memory loss, cognitive dysfunction, and neuropathological hallmarks including extracellular amyloid-β plaques and intracellular neurofibrillary tangles composed of hyperphosphorylated tau. Recently, the Locus Coeruleus (LC)—a small brainstem nucleus and the principal source of norepinephrine in the brain—has been identified as one of the earliest sites of AD-related pathology. The LC plays critical roles in arousal, attention, memory consolidation, and sleep–wake regulation. Histopathological studies suggest that LC degeneration may precede cortical involvement and trigger downstream neurodegenerative processes. Advances in neuroimaging techniques, including neuromelanin-sensitive MRI (NM-MRI), positron emission tomography (PET), resting-state functional MRI (rs-fMRI), and diffusion tensor imaging (DTI), now enable in vivo assessment of LC structural and functional integrity. This systematic review aims to evaluate existing evidence of LC alterations across AD, Mild Cognitive Impairment (MCI), and healthy controls (HC), and to explore its potential as a diagnostic or prognostic biomarker
Functional connectivity changes of the locus coeruleus in Alzheimer’s Disease
No full textGrowing evidence indicates neurone loss in the Locus Coeruleus (LC) in patients with Alzheimer’s Disease (AD). The wide projection and rich connectivity of the LC with multiple brain regions and its interaction with different neural networks suggests the importance of investigating the functional connectivity of the LC, an area of research which has been less studied. The primary aim of this study was to test for differences in functional connectivity of the LC between AD subjects and matched controls using neuromelanin-sensitive MRI (NM-MRI). The secondary aim of this study was to investigate the change in the resting state networks in AD. Pre-processing of the fMRI and structural MRI data from 23 AD subjects and 23 Controls was completed using the FMRIB Software Library (FSL). The images were skull-stripped, registered, and normalised. LC masks were created from the NM-MRI also using FSL. The subsequent data was processed using the CONN toolbox. Seed-to-voxel and ROI-ROI analysis were used to produce connectivity maps and comparisons were conducted between AD and Controls, Left and Right LC, Mild and Moderate AD, and resting state networks. In comparison to Controls, AD subjects had reduced LC connectivity in the subcallosal (p-FDR=0.016417), increased LC connectivity in the right supramarginal and postcentral gyri (p-FDR=0.000002), and reduced connectivity in the default mode network (p-FDR=0.000286) and sensorimotor network (p-FDR=0.027524). The left LC in the AD subjects had a decreased number of significant connections to the amygdala and vermis, compared to the right LC. The number of significant LC connections decreased with progression from controls to mild AD to moderate AD. This study provides new evidence of reduced LC connectivity in AD patients and asymmetrical reduction in the LC skewed towards the left LC. LC connectivity reduction could indicate pathogenesis and progression of AD, aiding prediction of disease progression and development of novel intervention targets
Is CAPM a Behavioral Model? Estimating Sentiments from Rationalism
No full textThe authors investigate the role of investor sentiment in asset pricing. In particular, they explore whether this investor sentiment has the ability to be predicted by the residuals from the capital asset pricing model (CAPM). The analysis makes use of data for S&P500 firms on a daily basis, spanning the period of 1995–2015, as well as certain panel methodological approaches. The results suggest that the residuals from the CAPM model gain explanatory power for investor sentiment. In other words, investor sentiment is a priced factor. The implication of this finding is that overlooking the role of investor sentiment in classical finance theory could lead to an imperfect picture of describing the asset pricing
Asymmetric Nonlinear Impact of Oil Prices and Inflation on Residential Property Prices: a Case of US, UK and Canada
No full textThis paper examines the nonlinear impact of oil prices and inflation on residential prices in the US, the UK and Canada using quarterly data from 1975 to 2017. The study uses nonlinear autoregressive distributed lag (NARDL) bounds testing approach that allows possible asymmetric effects in both short- and long-run. Our results highlight that oil prices, interest and inflation rates and income have asymmetric relationship with residential prices in US, UK and Canada; however, the extent and magnitude of this relationship varies. Long run coefficients of Inflation rate highlights significance for residential prices in all three economies i.e. US, UK and Canada. For international oil prices however, the asymmetric effect is more pronounced in US as compared with UK and Canada. In case of US, long-run asymmetric relationship of residential prices with inflation and gross domestic product (GDP) per capita is also witnessed however, interest rate seems to influence residential prices in both UK and Canada. Our paper has implications for the investors in residential housing markets and government authorities regulating housing sectors
Antiproliferative Activity of Lignans from Olea ferruginea: In Vitro Evidence Supported by Docking Studies
No full textApplications of susceptibility-based brain imaging using 7T MRI
No full textMRI is a powerful non-invasive technique for imaging soft tissues and for providing information on chemical composition. In this thesis, the effects of magnetic susceptibility from iron contained in ferritin and haemoglobin, and of myelinated tissue were studied. These effects were measured using a range of imaging techniques, including susceptibility weighted imaging (SWI) and quantitative susceptibility mapping (QSM).
Initially, simulations of static and defusing spins were performed to gain an understanding of the behaviour of different systems, which agreed well with comparison to the results from analytical models. For dipoles randomly placed in a spherical volume and in the x-y plane, the R2* and ∆ω values were approximately constant, but increased for dipoles restricted to a line parallel to the z axis and decreased for dipoles in a line in the x-y plane. The fitting of the phase variation of a simulated cylinder was then used to calculate the susceptibility values of a ferritin-doped cylindrical agar phantom, which correlated well between 3T and 7T, and increased with iron concentration.
Post-mortem imaging allows MR parameters to be studied in greater detail than in vivo imaging, but it is also confounded by fixation and storage conditions. An experimental setup was assembled to allow temperature-controlled scanning of a post-mortem brain. The R1, R2* and susceptibility values all decreased with increasing temperature, due to the reduction in the susceptibility of iron dominating the effect of the increased rate of diffusion of water. This was similar for a ferritin-doped cylindrical agar phantom, but the R2* values increased, due to the uniformity of agar. A longitudinal imaging study of the post-mortem brain was performed with respect to fixation time. The volume of the tissue decreased. The R2* and susceptibility values decreased and the R1 values
increased overall, but were also dependent on the location and depth within the tissue.
The thalamus relays information between different areas of the brain. In 1.5T and 3T MRI, the contrast between the thalamic nuclei is limited, thus motivating an evaluation of 7T post-mortem and in vivo MR imaging. A range of imaging sequences were optimised and the thalamic nuclei were manually delineated in the histology and corresponding post-mortem MR images, with a high degree of confidence, with reference to the Morel atlas. These were corroborated with the use of k-means clustering, Canny edge detection and hierarchical clustering. The nuclei in the in vivo images were also delineated with a reasonable degree of confidence, by comparing the boundaries across
a range of imaging contrasts. For the groupings obtained from hierarchical clustering, the QSM clusters allowed the most nuclei to be identified on average, followed by the combined FLASH (fast low angle shot) magnitude and QSM clusters.
The brain has a high level of metabolic activity, which requires a significant supply of blood. Disruption to this can result in the loss of function, as cerebrovascular diseases. The cerebral blood vessels were imaged with optimised gradient echo and time of flight sequences, to calculate venous and arterial maps, overlap maps and a venous atlas. The distribution of vessels between subjects was similar, with little overlap between the venous and arterial maps. The venous atlas detailed the deep grey matter vessels better than the manually segmented Ward atlas. Finally, oximetry measurements were inferred from the susceptibility values, which were higher within grey matter compared to white matter, and were observed to increase up to a vein radius of 1mm and then decreased
Applications of susceptibility-based brain imaging using 7T MRI
No full textMRI is a powerful non-invasive technique for imaging soft tissues and for providing information on chemical composition. In this thesis, the effects of magnetic susceptibility from iron contained in ferritin and haemoglobin, and of myelinated tissue were studied. These effects were measured using a range of imaging techniques, including susceptibility weighted imaging (SWI) and quantitative susceptibility mapping (QSM).
Initially, simulations of static and defusing spins were performed to gain an understanding of the behaviour of different systems, which agreed well with comparison to the results from analytical models. For dipoles randomly placed in a spherical volume and in the x-y plane, the R2* and ∆ω values were approximately constant, but increased for dipoles restricted to a line parallel to the z axis and decreased for dipoles in a line in the x-y plane. The fitting of the phase variation of a simulated cylinder was then used to calculate the susceptibility values of a ferritin-doped cylindrical agar phantom, which correlated well between 3T and 7T, and increased with iron concentration.
Post-mortem imaging allows MR parameters to be studied in greater detail than in vivo imaging, but it is also confounded by fixation and storage conditions. An experimental setup was assembled to allow temperature-controlled scanning of a post-mortem brain. The R1, R2* and susceptibility values all decreased with increasing temperature, due to the reduction in the susceptibility of iron dominating the effect of the increased rate of diffusion of water. This was similar for a ferritin-doped cylindrical agar phantom, but the R2* values increased, due to the uniformity of agar. A longitudinal imaging study of the post-mortem brain was performed with respect to fixation time. The volume of the tissue decreased. The R2* and susceptibility values decreased and the R1 values
increased overall, but were also dependent on the location and depth within the tissue.
The thalamus relays information between different areas of the brain. In 1.5T and 3T MRI, the contrast between the thalamic nuclei is limited, thus motivating an evaluation of 7T post-mortem and in vivo MR imaging. A range of imaging sequences were optimised and the thalamic nuclei were manually delineated in the histology and corresponding post-mortem MR images, with a high degree of confidence, with reference to the Morel atlas. These were corroborated with the use of k-means clustering, Canny edge detection and hierarchical clustering. The nuclei in the in vivo images were also delineated with a reasonable degree of confidence, by comparing the boundaries across
a range of imaging contrasts. For the groupings obtained from hierarchical clustering, the QSM clusters allowed the most nuclei to be identified on average, followed by the combined FLASH (fast low angle shot) magnitude and QSM clusters.
The brain has a high level of metabolic activity, which requires a significant supply of blood. Disruption to this can result in the loss of function, as cerebrovascular diseases. The cerebral blood vessels were imaged with optimised gradient echo and time of flight sequences, to calculate venous and arterial maps, overlap maps and a venous atlas. The distribution of vessels between subjects was similar, with little overlap between the venous and arterial maps. The venous atlas detailed the deep grey matter vessels better than the manually segmented Ward atlas. Finally, oximetry measurements were inferred from the susceptibility values, which were higher within grey matter compared to white matter, and were observed to increase up to a vein radius of 1mm and then decreased
The Renovation Wave: An opportunity to tackle energy poverty?: A Case Study-Mixed Methods (CS-MM) approach to including justice in renovation policies considering the socio-spatial vulnerability to energy poverty
No full textIn the wake of tackling energy poverty by its roots and protecting vulnerable groups, the European Commission introduced the so-called Renovation Wave, aiming to renovate 35 million inefficient buildings by 2050. However, even though the Renovation Wave was aimed to tackle energy poverty, recent studies have shown that renovation policies have failed to address energy poverty as renovation and social policies lack intersectoral integration resulting in the exclusion of vulnerable groups and an increased risk of social inequity. Moreover, various scholars have tried to identify vulnerability indicators that give rise to energy poverty; however, these have only focused on identifying socio-economic and energy indicators. Consequently, scholars have called to include justice in renovation policies and explore how vulnerable groups can be identified. To address this knowledge gap, the following main research question was formulated: Using a Case-Study Mixed Methods (CS-MM) approach, how can justice be included in renovation policies considering the socio-spatial vulnerability to energy poverty?The results showed that by identifying vulnerable groups based on a locally developed index of the socio-spatial vulnerability to energy poverty and acknowledging their vulnerability, recognitional justice can be included in renovation policies. Besides, identifying tailored policy strategies in a multi-stakeholder environment that, on the one hand, focus on the distribution of renovation resources based on the needs and characteristics of the identified vulnerable groups and, on the other hand, on how the vulnerable groups can be included in the decision-making, distributional and procedural justice can be included in renovation policies. Thus, it can be concluded that by deploying the current CS-MM approach, justice can be included. The outcomes of the present study are twofold. Firstly, from a scientific perspective, the present study contributes to the current body of scientific knowledge on: (1) how vulnerable groups in need of renovation can be identified, (2) how justice can be included in renovation policies to address energy poverty and (3) how a CS-MM approach can be deployed to research how justice can be included in renovation policies considering the socio-spatial vulnerability to energy poverty. Secondly, from a societal perspective, this study provides insights to improve policy strategies that enable local decision-makers to identify vulnerable groups and include justice in renovation, considering the socio-spatial vulnerability to energy poverty.Engineering and Policy Analysi
Dynamic risk spillovers and portfolio risk management between precious metals and global foreign exchange markets
No full textThis study examines portfolio management and risk spillovers between four major precious metals (gold, silver, palladium and platinum) and 20 important U.S. exchange markets. To this end, we employ the multivariate DECO-GARCH model and the spillover index developed by Diebold and Yilmaz (2014, 2016) to examine the spillovers between those metal prices and the exchange rates and design portfolios and hedging strategies using different risk measures. The results show evidence of weak average conditional equicorrelations among the considered markets over time, excluding the turbulent 2008–2010 period. Furthermore, the precious metals (excluding platinum) and the currencies (with the exception of the Australian, Brazilian, Denmark, Euro, Mexican, Norwegian, New Zealand and Swedish currencies) are net receivers of shocks. Finally, the four precious metals provide strong risk and downside risk reductions, underscoring the usefulness of including precious metals in a traditional foreign exchange-dominated portfolio.The fourth author (Alanoud Ali S A Al-Maadid) acknowledges the financial support by Qatar University internal research grant [QUCP-CBE-2018-1]. The last author (Sang Hoon Kang) acknowledges the financial support by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea (NRF-2017S1A5B8057488)
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