76 research outputs found
Two-Component Dust in Spherically Symmetric Motion
Two components of spherically symmetric, inhomogeneous dust penetrating each
other are introduced as a generalization of the well-known Tolman-Bondi dust
solution. The field equations of this model are formulated and general
properties are discussed. inhomogeneous Special solutions with additional
symmetries - an extra Killing- or homothetic vector - and their matching to the
corresponding Tolman-Bondi solution are investigated.Comment: 16 pages, LaTeX, 5 figures, accepted for publication in Class.
Quantum Gra
Self-Similarity in General Relativity \endtitle
The different kinds of self-similarity in general relativity are discussed,
with special emphasis on similarity of the ``first'' kind, corresponding to
spacetimes admitting a homothetic vector. We then survey the various classes of
self-similar solutions to Einstein's field equations and the different
mathematical approaches used in studying them. We focus mainly on spatially
homogenous and spherically symmetric self-similar solutions, emphasizing their
possible roles as asymptotic states for more general models. Perfect fluid
spherically symmetric similarity solutions have recently been completely
classified, and we discuss various astrophysical and cosmological applications
of such solutions. Finally we consider more general types of self-similar
models.Comment: TeX document, 53 page
Atherosclerotic pattern of coronary myocardial bridging assessed with CT coronary angiography
The aim of our study was to evaluate the atherosclerotic pattern of patients with coronary myocardial bridging (MB) by means of CT Coronary Angiography (CT-CA). 254 consecutive patients (166 male, mean age 58.6 ± 10.3) who underwent 64-slice CT-CA according to current clinical indications were reviewed for the presence of MB and concomitant segmental atherosclerotic pattern. Coronary plaques were assessed in all patients enrolled. 73 patients (29%) presented single (90%) or multiple (10%) MB, frequently (93%) localized in the mid-distal left anterior descending artery. The MB segment was always free of atherosclerosis. Segments proximal to the MB presented: no atherosclerotic disease (n = 37), positive remodeling (n = 23), 50% stenoses (n = 7). Distal segments presented a different atherosclerosis pattern (P < 0.0001): absence of disease (n = 73), no significant lesions (n = 8). No significant differences were found between segments proximal to MB and proximal coronary segments apart from left main trunk. Pattern of atherosclerotic lesions located in segments 6 and 7 significantly differs between patients with MB and patients without MB (P < 0.05). CT-CA is a reliable method to non-invasively demonstrate MB and related atherosclerotic pattern. CT-CA provides new insight regarding atherosclerosis distribution in segments close to MB
Cognitive Profile of Students Who Enter Higher Education with an Indication of Dyslexia
For languages other than English there is a lack of empirical evidence about the cognitive profile of students entering higher education with a diagnosis of dyslexia. To obtain such evidence, we compared a group of 100 Dutch-speaking students diagnosed with dyslexia with a control group of 100 students without learning disabilities. Our study showed selective deficits in reading and writing (effect sizes for accuracy between dâ=â1 and dâ=â2), arithmetic (dâ1), and phonological processing (d>0.7). Except for spelling, these deficits were larger for speed related measures than for accuracy related measures. Students with dyslexia also performed slightly inferior on the KAIT tests of crystallized intelligence, due to the retrieval of verbal information from long-term memory. No significant differences were observed in the KAIT tests of fluid intelligence. The profile we obtained agrees with a recent meta-analysis of English findings suggesting that it generalizes to all alphabetic languages. Implications for special arrangements for students with dyslexia in higher education are outlined
Group membership and racial bias modulate the temporal estimation of in-group/out-group body movements
Social group categorization has been mainly studied in relation to ownership manipulations involving highly-salient multisensory cues. Here, we propose a novel paradigm that can implicitly activate the embodiment process in the presence of group affiliation information, whilst participants complete a task irrelevant to social categorization. Ethnically White participants watched videos of White- and Black-skinned models writing a proverb. The writing was interrupted 7, 4 or 1 s before completion. Participants were tasked with estimating the residual duration following interruption. A video showing only hand kinematic traces acted as a control condition. Residual duration estimates for out-group and control videos were significantly lower than those for in-group videos only for the longest duration. Moreover, stronger implicit racial bias was negatively correlated to estimates of residual duration for out-group videos. The underestimation bias for the out-group condition might be mediated by implicit embodiment, affective and attentional processes, and finalized to a rapid out-group categorization
Monitoreo del progreso del alumno en la identificaciĂłn de riesgo en la lectura
Este estudo tem por nalidade analisar o uso da monitorização com base no currĂculo como sistema escolar de identi cação de alunos em risco na leitura, no contexto de um modelo educativo baseado no grau de resposta Ă intervenção. Realizou-se uma investigação quantitativa em que participaram todos os alunos do 3o ano (82 alunos) de um agrupamento de escolas do norte de Portugal. O tratamento de dados foi feito com recurso Ă estatĂstica descritiva e inferencial. Destacam-se, entre outras conclusĂ”es, a existĂȘncia de dez alunos em risco na leitura durante todo o ano letivo e o facto de, no nal do 3o ano de escolaridade, a mĂ©dia de resultados dos alunos que nunca estiveram em risco ser superior ao dobro da mĂ©dia de resultados dos alunos que estiveram em risco todo o ano.This study aims to analyze the use of curriculum-based monitoring as a school
system to identify students at risk in reading, in the context of an educational
model based on the degree of response to intervention. A quantitative investigation
was conducted with all third grade students (82 students) from a group of
schools in the north of Portugal. Data processing was done using descriptive and
inferential statistics. Among the conclusions, the following stand out: the existence
of ten students at risk in reading throughout the school year and the fact that, at
the end of the third year of schooling, the mean results of students who were never
at risk was more than double the mean results of students who were at risk for the
entire year.Cette Ă©tude a pour but dâanalyser lâusage du contĂŽle ayant pour base le coursus
comme systĂšme scolaire dâidentification des Ă©lĂšves prĂ©sentant des risques dans la
lecture, dans le contexte dâun modĂšle Ă©ducatif fondĂ© sur le degrĂ©e de rĂ©ponse Ă
lâintervention. On a fait une investigation quantitative Ă laquelle ont participĂ© tous
les Ă©lĂšves de CM1 (82 Ă©lĂšves) dâun groupement dâĂ©coles du nord du Portugal. Le
traitement des donnĂ©es a Ă©tĂ© fait Ă lâaide de la statistique descriptive et infĂ©rentielle.
On souligne, entre autres conclusions, lâexistence de dix Ă©lĂšves en risque dans la
lecture pendant toute lâannĂ©e scolaire et le fait quâĂ la fin de la troisiĂšmme annĂ©e
de scolaritĂ©, la moyenne des rĂ©sultats des Ă©lĂšves nâayant jamais Ă©tĂ© en risque soit
supérieur au double de la moyenne des résultats des élÚves qui ont été en risque
toute lâannĂ©e.Este estudio tiene la finalidad de analizar el uso del monitoreo del currĂculo como
sistema escolar de identificaciĂłn de alumnos en riesgo en la lectura, en el marco
de un modelo educativo basado en el grado de respuesta a la intervenciĂłn. Se llevĂł
a cabo una investigaciĂłn cuantitativa en la que participaron todos los alumnos
del 3er año (82 alumnos) de un agrupamiento de escuelas del norte de Portugal.
El tratamiento de datos se efectuĂł por medio de la estadĂstica descriptiva e de
inferencias. Se destacan, entre otras conclusiones, la existencia de diez alumnos en
riesgo en la lectura durante todo el año lectivo y el hecho de que, al final del 3er
año de escolaridad, el promedio de resultados de los alumnos que nunca estuvieron
en riesgo era superior al doble del promedio de resultados de los alumnos que
estuvieron en riesgo todo el año.(undefined)info:eu-repo/semantics/publishedVersio
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