1,812 research outputs found
Global evolution in spherical symmetry for self-gravitating massive fields
We are interested in the global dynamics of a massive scalar field evolving
under its own gravitational field and, in this paper, we study spherically
symmetric solutions to Einstein's field equations coupled with a Klein-Gordon
equation with quadratic potential. For the initial value problem we establish a
global existence theory when initial data are prescribed on a future light cone
with vertex at the center of symmetry. A suitably generalized solution in Bondi
coordinates is sought which has low regularity and possibly large but finite
Bondi mass. A similar result was established first by Christodoulou for
massless fields. In order to deal with massive fields, we must overcome several
challenges and significantly modify Christodoulou's original method. First of
all, we formulate the Einstein-Klein-Gordon system in spherical symmetry as a
non-local and nonlinear hyperbolic equation and, by carefully investigating the
global dynamical behavior of the massive field, we establish various estimates
concerning the Einstein operator, the Hawking mass, and the Bondi mass,
including positivity and monotonicity properties. Importantly, in addition to a
regularization at the center of symmetry we find it necessary to also introduce
a regularization at null infinity. We also establish new energy and decay
estimates for, both, regularized and generalized solutions.Comment: 43 page
Low prevalence of coagulation F2 and F5 polymorphisms in mothers and children in a large cohort of patients with neonatal arterial ischemic stroke
International audienc
Anxious/depressed symptoms are related to microstructural maturation of white matter in typically developing youths
AbstractThere are multiple recent reports of an association between anxious/depressed (A/D) symptomatology and the rate of cerebral cortical thickness maturation in typically developing youths. We investigated the degree to which anxious/depressed symptoms are tied to age-related microstructural changes in cerebral fiber pathways. The participants were part of the NIH MRI Study of Normal Brain Development. Child Behavior Checklist A/D scores and diffusion imaging were available for 175 youths (84 males, 91 females; 241 magnetic resonance imagings) at up to three visits. The participants ranged from 5.7 to 18.4 years of age at the time of the scan. Alignment of fractional anisotropy data was implemented using FSL/Tract-Based Spatial Statistics, and linear mixed model regression was carried out using SPSS. Child Behavior Checklist A/D was associated with the rate of microstructural development in several white matter pathways, including the bilateral anterior thalamic radiation, bilateral inferior longitudinal fasciculus, left superior longitudinal fasciculus, and right cingulum. Across these pathways, greater age-related fractional anisotropy increases were observed at lower levels of A/D. The results suggest that subclinical A/D symptoms are associated with the rate of microstructural development within several white matter pathways that have been implicated in affect regulation, as well as mood and anxiety psychopathology.</jats:p
Web-based multimodal graphs for visually impaired people
This paper describes the development and evaluation of Web-based multimodal graphs designed for visually impaired and blind people. The information in the graphs is conveyed to visually impaired people through haptic and audio channels. The motivation of this work is to address problems faced by visually impaired people in accessing graphical information on the Internet, particularly the common types of graphs for data visualization. In our work, line graphs, bar charts and pie charts are accessible through a force feedback device, the Logitech WingMan Force Feedback Mouse. Pre-recorded sound files are used to represent graph contents to users. In order to test the usability of the developed Web graphs, an evaluation was conducted with bar charts as the experimental platform. The results showed that the participants could successfully use the haptic and audio features to extract information from the Web graphs
Some chemical constituents isolated from Acorus tatarinowii Shott.
Anew 8,1′-neolignan, tatarinone, 4-[2-(1,2,3-trimethoxybenz-5-yl)-1-methylethyl]-2,5-dimethoxy-4-(2-propenyl)-2,5-cyclohexadien-1-one, has been isolated from Acorus tatarinowii rhizome and  its structure determined by spectroscopic methods, including 2D-NMR spectra. Asarylaldehyde and a mixture of α-asarone and β-asarone were also isolated and  indentified.Keywords: Acorus tatarinowii;Araceae; 8,1′-neolignans; asarylaldehyde; α-asarone; β-asarone; NMR
Motor Outcomes After Neonatal Arterial Ischemic Stroke Related to Early MRI Data in a Prospective Study
OBJECTIVE: We aimed to correlate early imaging data with motor outcomes in a large, homogeneous, cohort of infants with neonatal (diagnosed before 29 days of life) arterial ischemic stroke (AIS).METHODS: From a prospective cohort of 100 children with neonatal AIS, we analyzed the MRI studies performed within the 28 first days of life for 80 infants evaluated at 2 years of age. The relationships between infarction location and corticospinal tract (CST) involvement and motor outcomes were studied RESULTS: Seventy-three infarctions involved the middle cerebral artery (MCA) territory. Of those, 50 were superficial infarctions, 5 deep infarctions, and 18 mixed infarctions. The CST was involved in 24 cases. Nineteen patients with MCA infarctions (26% [95% confidence interval: 16%–34%]) developed hemiplegia. Mixed infarctions (P < .0001) and CST involvement (P < .0001) were highly predictive of hemiplegia. In contrast, 88% of children with isolated superficial MCA infarctions did not exhibit impairment. CONCLUSIONS: Accurate prediction of motor outcomes can be obtained from early MRI scans after neonatal AIS. The absence of involvement of the CST resulted in normal motor development in 94% of cases. CST involvement resulted in congenital hemiplegia in 66% of cases
Staircase polygons: moments of diagonal lengths and column heights
We consider staircase polygons, counted by perimeter and sums of k-th powers
of their diagonal lengths, k being a positive integer. We derive limit
distributions for these parameters in the limit of large perimeter and compare
the results to Monte-Carlo simulations of self-avoiding polygons. We also
analyse staircase polygons, counted by width and sums of powers of their column
heights, and we apply our methods to related models of directed walks.Comment: 24 pages, 7 figures; to appear in proceedings of Counting Complexity:
An International Workshop On Statistical Mechanics And Combinatorics, 10-15
July 2005, Queensland, Australi
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