485 research outputs found
Lesion topography and microscopic white matter tract damage contribute to cognitive impairment in symptomatic carotid artery disease
Purpose: To investigate associations between neuroimaging markers of cerebrovascular disease, including lesion topography and extent and severity of strategic and global cerebral tissue injury, and cognition in carotid artery disease (CAD).
Materials and Methods: All participants gave written informed consent to undergo brain magnetic resonance imaging and the Addenbrookeâs Cognitive ExaminationâRevised. One hundred eight patients with symptomatic CAD but no dementia were included, and a score less than 82 represented cognitive impairment. Group comparison and interrelations between global cognitive and fluency performance, lesion topography, and ultrastructural damage were assessed with voxel-based statistics. Associations between cognition, medial temporal lobe atrophy (MTA), lesion volumes, and global white matter ultrastructural damage indexed as increased mean diffusivity were tested with regression analysis by controlling for age. Diagnostic accuracy of imaging markers selected from a multivariate prediction model was tested with receiver operating characteristic analysis.
Results: Cognitively impaired patients (n = 53 [49.1%], classified as having probable vascular cognitive disorder) were older than nonimpaired patients (P = .027) and had more frequent MTA (P<.001), more cortical infarctions (P = .016), and larger volumes of acute (P = .028) and chronic (P = .009) subcortical ischemic lesions. Lesion volumes did not correlate with global cognitive performance (lacunar infarctions, P = .060; acute lesions, P = .088; chronic subcortical ischemic lesions, P = .085). In contrast, cognitive performance correlated with presence of chronic ischemic lesions within the interhemispheric tracts and thalamic radiation (P< .05, false discovery rate corrected). Skeleton mean diffusivity showed the closest correlation with cognition (R2 = 0.311, P< .001) and promising diagnostic accuracy for vascular cognitive disorder (area under the curve, 0.82 [95% confidence interval: 0.75, 0.90]). Findings were confirmed in subjects with a low risk of preclinical Alzheimer disease indexed by the absence of MTA (n = 85).
Conclusion: Subcortical white matter ischemic lesion locations and severity of ultrastructural tract damage contribute to cognitive impairment in symptomatic CAD, which suggests that subcortical disconnection within large-scale cognitive neural networks is a key mechanism of vascular cognitive disorder
Strain evolution in GaN Nanowires: from free-surface objects to coalesced templates
Top-down fabricated GaN nanowires, 250 nm in diameter and with various
heights, have been used to experimentally determine the evolution of strain
along the vertical direction of 1-dimensional objects. X-ray diffraction and
photoluminescence techniques have been used to obtain the strain profile inside
the nanowires from their base to their top facet for both initial compressive
and tensile strains. The relaxation behaviors derived from optical and
structural characterizations perfectly match the numerical results of
calculations based on a continuous media approach. By monitoring the elastic
relaxation enabled by the lateral free-surfaces, the height from which the
nanowires can be considered strain-free has been estimated. Based on this
result, NWs sufficiently high to be strain-free have been coalesced to form a
continuous GaN layer. X-ray diffraction, photoluminescence and
cathodoluminescence clearly show that despite the initial strain-free nanowires
template, the final GaN layer is strained
Faraday Rotation as a diagnostic of Galactic foreground contamination of CMB maps
The contribution from the residuals of the foreground can have a significant
impact on the temperature maps of the Cosmic Microwave Background (CMB).
Mostly, the focus has been on the galactic plane, when foreground cleaning has
taken place. However, in this paper, we will investigate the possible
foreground contamination, from sources outside the galactic plane in the CMB
maps. We will analyze the correlation between the Faraday rotation map and the
CMB temperature map. The Faraday rotation map is dependent on the galactic
magnetic field, as well as the thermal electron density, and both may
contribute to the CMB temperature. We find that the standard deviation for the
mean cross correlation deviate from that of simulations at the 99.9% level.
Additionally, a comparison between the CMB temperature extrema and the extremum
points of the Faraday rotation is also performed, showing a general overlap
between the two. Also we find that the CMB Cold Spot is located at an area of
strong negative cross correlation, meaning that it may be explained by a
galactic origin. Further, we investigate nearby supernova remnants in the
galaxy, traced by the galactic radio loops. These super nova remnants are
located at high and low galactic latitude, and thus well outside the galactic
plane. We find some correlation between the Faraday Rotation and the CMB
temperature, at select radio loops. This indicate, that the galactic
foregrounds may affect the CMB, at high galactic latitudesComment: 13 pages, 22 figures, 6 table
Impact of atrial fibrillation diagnosis or carotid enderterectomy requirement on outcome in patients from the triple antiplatelets for reducing dependency after ischaemic stroke (TARDIS) trial
Spectra of weighted algebras of holomorphic functions
We consider weighted algebras of holomorphic functions on a Banach space. We
determine conditions on a family of weights that assure that the corresponding
weighted space is an algebra or has polynomial Schauder decompositions. We
study the spectra of weighted algebras and endow them with an analytic
structure. We also deal with composition operators and algebra homomorphisms,
in particular to investigate how their induced mappings act on the analytic
structure of the spectrum. Moreover, a Banach-Stone type question is addressed.Comment: 25 pages Corrected typo
Work-Unit Absenteeism: Effects of Satisfaction, Commitment, Labor Market Conditions, and Time
Prior research is limited in explaining absenteeism at the unit level and over time. We developed and tested a model of unit-level absenteeism using five waves of data collected over six years from 115 work units in a large state agency. Unit-level job satisfaction, organizational commitment, and local unemployment were modeled as time-varying predictors of absenteeism. Shared satisfaction and commitment interacted in predicting absenteeism but were not related to the rate of change in absenteeism over time. Unit-level satisfaction and commitment were more strongly related to absenteeism when units were located in areas with plentiful job alternatives
Non-Gaussianity detections in the Bianchi VIIh corrected WMAP 1-year data made with directional spherical wavelets
Many of the current anomalies reported in the Wilkinson Microwave Anisotropy
Probe (WMAP) 1-year data disappear after `correcting' for the best-fit embedded
Bianchi type VII_h component (Jaffe et al. 2005), albeit assuming no dark
energy component. We investigate the effect of this Bianchi correction on the
detections of non-Gaussianity in the WMAP data that we previously made using
directional spherical wavelets (McEwen et al. 2005a). As previously discovered
by Jaffe et al. (2005), the deviations from Gaussianity in the kurtosis of
spherical Mexican hat wavelet coefficients are eliminated once the data is
corrected for the Bianchi component. This is due to the reduction of the cold
spot at Galactic coordinates (l,b)=(209^\circ,-57\circ), which Cruz et al.
(2005) claim to be the source of non-Gaussianity introduced in the kurtosis.
Our previous detections of non-Gaussianity observed in the skewness of
spherical wavelet coefficients are not reduced by the Bianchi correction.
Indeed, the most significant detection of non-Gaussianity made with the
spherical real Morlet wavelet at a significant level of 98.4% remains (using a
very conservative method to estimate the significance). We make our code to
simulate Bianchi induced temperature fluctuations publicly available.Comment: 11 pages, 8 figures, replaced to match version accepted by MNRA
Rapid assessment of visual impairment (RAVI) in marine fishing communities in South India - study protocol and main findings
<p>Abstract</p> <p>Background</p> <p>Reliable data are a pre-requisite for planning eye care services. Though conventional cross sectional studies provide reliable information, they are resource intensive. A novel rapid assessment method was used to investigate the prevalence and causes of visual impairment and presbyopia in subjects aged 40 years and older. This paper describes the detailed methodology and study procedures of Rapid Assessment of Visual Impairment (RAVI) project.</p> <p>Methods</p> <p>A population-based cross-sectional study was conducted using cluster random sampling in the coastal region of Prakasam district of Andhra Pradesh in India, predominantly inhabited by fishing communities. Unaided, aided and pinhole visual acuity (VA) was assessed using a Snellen chart at a distance of 6 meters. The VA was re-assessed using a pinhole, if VA was < 6/12 in either eye. Near vision was assessed using N notation chart binocularly. Visual impairment was defined as presenting VA < 6/18 in the better eye. Presbyopia is defined as binocular near vision worse than N8 in subjects with binocular distance VA of 6/18 or better.</p> <p>Results</p> <p>The data collection was completed in <12 weeks using two teams each consisting of one paramedical ophthalmic personnel and two community eye health workers. The prevalence of visual impairment was 30% (95% CI, 27.6-32.2). This included 111 (7.1%; 95% CI, 5.8-8.4) individuals with blindness. Cataract was the leading cause of visual impairment followed by uncorrected refractive errors. The prevalence of blindness according to WHO definition (presenting VA < 3/60 in the better eye) was 2.7% (95% CI, 1.9-3.5).</p> <p>Conclusion</p> <p>There is a high prevalence of visual impairment in marine fishing communities in Prakasam district in India. The data from this rapid assessment survey can now be used as a baseline to start eye care services in this region. The rapid assessment methodology (RAVI) reported in this paper is robust, quick and has the potential to be replicated in other areas.</p
Largeâscale network dysfunction in vascular cognitive disorder supports connectional diaschisis in advanced arteriosclerosis
Background and PurposeThe interrelation of cognitive performance, cerebrovascular damage and brain functional connectivity (FC) in advanced arteriosclerosis remains unclear. Our aim was to investigate the associations between FC, white matter damage and cognitive impairment in carotid artery disease.MethodsSeventyâone participants with recent cerebrovascular event and with written informed consent underwent restingâstate functional MRI (fMRI) and the Addenbrooke's Cognitive ExaminationâRevised (ACEâR). Network and interâhemispheric FC metrics were compared between cognitively normal and impaired subjects, and interrelated with cognition. In order to explore the nature of FC changes, we investigated their associations with microstructural damage of related white matter tracts and cognitive performance, followed by mediation analysis.ResultsParticipants with global cognitive impairment showed reduced FC compared to the cognitively intact subjects within the central executive network (CEN), and between hemispheres. Patients with executive dysfunction had decreased CEN FC while patients with memory loss demonstrated low FC in both CEN and default mode network (DMN). Global performance correlated with connectivity metrics of the CEN hub with DMN nodes, and between hemispheres. Cingulum mean diffusivity (MD) was negatively correlated with the ACEâR and CENâDMN FC. The cingulum MDâcognition association was partially mediated by CEN DMN FC.ConclusionsLongârange functional disconnection of CEN with DMN nodes is the main feature of cognitive impairment in elderly subjects with symptomatic carotid artery disease. Our findings provide further support for the connectional diaschisis concept of vascular cognitive disorder (VCD), and highlight a mediation role of functional disconnection to explain associations between microstructural white matter tract damage and cognitive impairment
SIOP Ependymoma I: Final results, long term follow-up and molecular analysis of the trial cohort: A BIOMECA Consortium Study
BACKGROUND: SIOP Ependymoma I was a non-randomised trial assessing event free and overall survival (EFS/OS) of non-metastatic intracranial ependymoma in children aged 3 to 21 years treated with a staged management strategy. A further aim was to assess the response rate (RR) of subtotally resected (STR) ependymoma to vincristine, etoposide and cyclophosphamide (VEC). We report final results with 12-year follow-up and post hoc analyses of recently described biomarkers. METHODS: 74 participants were eligible. Children with gross total resection (GTR) received radiotherapy, whilst those with STR received VEC before radiotherapy. DNA methylation, 1q, hTERT, ReLA, Tenascin-C, H3K27me3 and pAKT status were evaluated. RESULTS: Five- and ten-year EFS was 49.5% and 46.7%, OS was 69.3% and 60.5%. GTR was achieved in 33/74 (44.6%) and associated with improved EFS (p=0.003, HR=2.6, 95% confidence interval (CI) 1.4-5.1). Grade 3 tumours were associated with worse OS (p=0.005, HR=2.8, 95%CI 1.3-5.8). 1q gain and hTERT expression were associated with poorer EFS (p=0.003, HR=2.70, 95%CI 1.49-6.10 and p=0.014, HR=5.8, 95%CI 1.2-28) and H3K27me3 loss with worse OS (p=0.003, HR=4.6, 95%CI 1.5-13.2). Methylation profiles showed expected patterns. 12 participants with STR did not receive chemotherapy; a protocol violation. However, best chemotherapy RR was 65.5% (19/29, 95%CI 45.7-82.1), exceeding the prespecified 45%. CONCLUSIONS: Participants with totally resected ependymoma had the best outcomes. RR of STR to VEC exceeded the pre-specified efficacy criterion. However, cases of inaccurate stratification highlighted the need for rapid central review. 1q gain, H3K27me3 loss and hTERT expression were all associated with poorer survival outcomes
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