7,577 research outputs found
Constraints on a strong X-ray flare in the Seyfert galaxy MCG-6-30-15
We discuss implications of a strong flare event observed in the Seyfert
galaxy MCG-6-30-15 assuming that the emission is due to localized magnetic
reconnection. We conduct detailed radiative transfer modeling of the
reprocessed radiation for a primary source that is elevated above the disk. The
model includes relativistic effects and Keplerian motion around the black hole.
We show that for such a model setup the observed time-modulation must be
intrinsic to the primary source. Using a simple analytical model we then
investigate time delays between hard and soft X-rays during the flare. The
model considers an intrinsic delay between primary and reprocessed radiation,
which measures the geometrical distance of the flare source to the reprocessing
sites. The observed time delays are well reproduced if one assumes that the
reprocessing happens in magnetically confined, cold clouds.Comment: 4 pages, 2 figures, proceedings of a talk given at the symposium 238
at the IAU General Assembly 200
Mammalian Enamel Prism Patterns and Enamel Deposition Rates
Enamel prism patterns and enamel deposition rates were compared for specimens representing six mammalian orders. Enamel samples were characterized by either pattern 1 or pattern 3 prisms. Each prism pattern cate-gory contained prisms from at least two mammalian orders. Enamel deposition rate was estimated for each sample by measuring prism cross striation repeat intervals. Statistical analysis of cross striation repeat intervals illustrates significant differences in deposition rate between prism patterns 1 and 3. No statistically significant differences were found in deposition rate between the higher-level taxa represented within each prism pat-tern category. That enamel deposition rate is not taxon-specific reinforces the close association between deposition rate and prism morphology. In accord with previous studies, pattern 1 enamel is deposited more slowly than is pattern 3 enamel. Correlation analyses illustrated a lack of association between enamel deposition rate and body mass, tooth size, and estimated ameloblast size. Evidence that enamel deposition rate is associated with enamel prism morphology, coupled with evidence that deposition rate is not correlated with size parameters, points to developmental homology (i.e., homogeneous deposition rate) within each prism pattern
A study of the effectiveness of intensive observation of patients' behavior followed by group discussion in teaching nursing students while in the clinical field of child psychiatry.
Includes 19 tables and 2 figures.
Thesis (M.S.)--Boston Universit
Enamel Prism Morphology in Molar Teeth of Small Eutherian Mammals
Data summarizing enamel prism shape, sire and spacing are reported for the molar enamel of 55 species of small eutherian mammals including primates, bats, tree shrews, flying lemurs, insectivorans and representatives of a variety of fossil families. Confocal photomicrographs reveal that the subsurface enamel of most species is characterized by arc-shaped prisms. The lack of a clear distinction between pattern 2 and pattern 3 prism configurations within single specimens suggests that the broad category arc-shaped prisms is the most appropriate descriptive grouping for these species. Of the total sample, three species exhibit only circular prisms while no evidence of prismatic enamel was found in two bats. Prism shape is not an informative phylogenetic character at the ordinal level for these morphologically primitive and relatively thin-enameled taxa. Significant differences between species in several prism sire and spacing variables (central distance between prisms, prism diameter, prism area and the ratio of prism area to estimated ameloblast area) suggest the potential for further analyses of quantitative variation to document evolutionary relationships within or among family-level groups
X-ray Variability of AGN and the Flare Model
Short-term variability of X-ray continuum spectra has been reported for
several Active Galactic Nuclei. Significant X-ray flux variations are observed
within time scales down to 10^3-10^5 seconds. We discuss short variability time
scales in the frame of the X-ray flare model, which assumes the release of a
large hard X-ray flux above a small portion of the accretion disk. The
resulting observed X-ray spectrum is composed of the primary radiation and of a
reprocessed Compton reflection component that we model with numerical radiative
transfer simulations. The incident hard X-rays of the flare will heat up the
atmosphere of the accretion disk and hence induce thermal expansion.
Eventually, the flare source will be surrounded by an optically thick medium,
which should modify the observed spectra.Comment: 4 pages, 3 figures, accepted proceedings for a talk at the conference
"AGN variability from the X-rays to the radio", June 2004, Crimean
Observator
The projective translation equation and unramified 2-dimensional flows with rational vector fields
Let X=(x,y). Previously we have found all rational solutions of the
2-dimensional projective translation equation, or PrTE,
(1-z)f(X)=f(f(Xz)(1-z)/z); here f(X)=(u(x,y),v(x,y)) is a pair of two (real or
complex) functions. Solutions of this functional equation are called projective
flows. A vector field of a rational flow is a pair of 2-homogenic rational
functions. On the other hand, only special pairs of 2-homogenic rational
functions give rise to rational flows. In this paper we are interested in all
non-singular (satisfying the boundary condition) and unramified (without
branching points, i.e. single-valued functions in C^2\{union of curves})
projective flows whose vector field is still rational. We prove that, up to
conjugation with 1-homogenic birational plane transformation, these are of 6
types: 1) the identity flow; 2) one flow for each non-negative integer N -
these flows are rational of level N; 3) the level 1 exponential flow, which is
also conjugate to the level 1 tangent flow; 4) the level 3 flow expressable in
terms of Dixonian (equianharmonic) elliptic functions; 5) the level 4 flow
expressable in terms of lemniscatic elliptic functions; 6) the level 6 flow
expressable in terms of Dixonian elliptic functions again. This reveals another
aspect of the PrTE: in the latter four cases this equation is equivalent and
provides a uniform framework to addition formulas for exponential, tangent, or
special elliptic functions (also addition formulas for polynomials and the
logarithm, though the latter appears only in branched flows). Moreover, the
PrTE turns out to have a connection with Polya-Eggenberger urn models. Another
purpose of this study is expository, and we provide the list of open problems
and directions in the theory of PrTE; for example, we define the notion of
quasi-rational projective flows which includes curves of arbitrary genus.Comment: 34 pages, 2 figure
Post Hoc Analysis on the Effect of Early Intensive Behavioral Intervention Provided to Preschool Children on the Autism Spectrum
Early Intensive Behavioral Intervention (EIBI) provides a framework for educators to assist children diagnosed with autism spectrum disorder (ASD) to increase independence and positive social skills in the classroom (Reichow, 2012). Preschoolers with ASD who do not have access to programs tend to display negative and socially inappropriate behavior, such as acts of aggression, withdrawal, and inability to attend to lessons. Studies on program effectiveness documented that preschool children who received EIBI scored higher on IQ, language comprehension, imitation, expressive language, nonverbal communication, play, stereotyped behaviors and adaptive functioning compared to preschool children who do not receive EIBI. The literature revealed that children with ASD who received EIBI maintained successful relationships with peers through joint attention, displayed increased use of appropriate language, and demonstrated an interest in participating in group classroom activities (Barber, Saffo, Gilpin, Craft, & Goldsetin, 2015). The purpose of the study was to evaluate student development on language, behavior, and peer relationships by analyzing pre- and post- assessments gathered over a three-year period. The study included data collected on a child in a general education non-profit preschool setting. The study was evaluative in nature and documented student progress toward behavior improvement as part of the agency’s evaluation policy results indicated that EIBI contributed to increasing the child’s socially appropriate behavior, language development, and peer interaction. Keywords: Autism spectrum disorder (ASD), Early Intensive Behavioral Intervention (EIBI) Effects of Early Intervention for Children With AS
Analysis of Data on the Effect of Early Intervention for Children on the Autism Spectrum
Early Intervention promotes preschool age children, identified on the autism spectrum, with increased independence and positive social skills in the classroom. Preschool children who do not have access to such programs tend to display negative and socially inappropriate behavior, such as acts of aggression, withdrawal, and inability to attend to lessons. Lovaas as cited in Eikeseth and Smith (2011) is referred to as the pioneer of Early Intervention, who dedicated almost fifty years of his life to improving the lives of families among the autism community. Lovaas’ studies were the first documented to indicate that children who received early intensive intervention made dramatic gains in development (Eikeseth & Smith, 2011). Studies on program effectiveness documented that preschool-age children who received Early Intervention scored higher on IQ, language comprehension, imitation, expressive language, nonverbal communication, play, stereotyped behaviors and adaptive functioning compared to children who did not receive Early Intervention (Eikeseth, et. al, 2012).
The literature reveals that children who receive Early Intervention maintain successful relationships with peers through joint-attention, display increased use of appropriate language, as well as demonstrate an interest in participating in group classroom activities (Eldevik, et. al, 2012). The purpose of the study is to analyze data on children who receive Early Intervention and children who do not receive Early Intervention with a focus on the factors of independence and positive social skills.
Eikeseth, S., Klintwall, L., Jahr, E., & Karlsson, P. (2012). Outcome for children with autism receiving early and intensive behavioral intervention in mainstream preschool and kindergarten settings. Research in Autism Spectrum Disorders, 6, 829-835.
Eldevik, S., Hastings, R., Jahr, E., & Hughes, J. (2012). Outcomes of behavioral intervention for children with autism in mainstream pre-school settings. Journal of Autism & Developmental Disorders, 42(2), 210-220.
Smith, T., & Eikeseth, S. (2011). O. Ivar Lovaas: Pioneer of applied behavior analysis and intervention for children with autism.Journal of Autism & Developmental Disorders, 41(3), 375-378
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