Proc. 28th ICRC Tsukuba, 2003, pp.1929-1932 The diffusion of galactic cosmic rays (CR) is considered. It is anticipated
that the nonlinear MHD cascade sets the power-law spectrum of turbulence from
...the principle scale 100 pc to much smaller scales. We found that the
dissipation of waves due to the resonant interaction with energetic particles
may terminate the cascade at less than 1.e13 cm. The shape of CR diffusion
coefficient that was found may explain the observed peaks of secondary to
primary nuclei ratios at a few GeV/n.
Astron.Astrophys. 410 (2003) 189-198 We study the production of cosmic rays (CRs) in supernova remnants (SNRs),
including the reacceleration of background galactic cosmic rays (GCRs) - thus
refining ...the early considerations by Blandford & Ostriker (1980) and Wandel et
al. (1987) - and the effects of the nuclear spallation inside the sources (the
SNRs). This combines for the first time nuclear spallation inside CR sources
and in the diffuse interstellar medium, as well as reacceleration, with the
injection and subsequent acceleration of suprathermal particles from the
postshock thermal pool. Selfconsistent CR spectra are calculated on the basis
of the nonlinear kinetic model. It is shown that GCR reacceleration and CR
spallation produce a measurable effect at high energies, especially in the
secondary to primary (s/p) ratio, making its energy-dependence substantially
flatter than predicted by the standard model. Quantitatively, the effect
depends strongly upon the density of the surrounding circumstellar matter. GCR
reacceleration dominates secondary CR production for a low circumstellar
density. It increases the expected s/p ratio substantially and flattens its
spectrum to an almost energy-independent form for energies larger than 100
GeV/n if the supernovae explode on average into a hot dilute medium with
hydrogen number density $N_H=0.003$cm$^{-3}$. The contribution of CR spallation
inside SNRs to the s/p ratio increases with increasing circumstellar density
and becomes dominant for $N_H\gsim 1$ cm$^{-3}$, leading at high energies to a
flat s/p ratio which is only by a factor of three lower than in the case of the
hot medium. Measurements of the boron to carbon ratio at energies above 100
GeV/n could be used in comparison with the values predicted here as a
consistency test for the supernova origin of the GCRs.
The physical processes involved in diffusion of Galactic cosmic rays in the interstellar medium are addressed. We study the possibility that the nonlinear MHD cascade sets the power-law spectrum of ...turbulence which scatters charged energetic particles. We find that the dissipation of waves due to the resonant interaction with cosmic ray particles may terminate the Kraichnan-type cascade below wavelengths 10^13 cm. The effect of this wave dissipation has been incorporated in the GALPROP numerical propagation code in order to asses the impact on measurable astrophysical data. The energy-dependence of the cosmic-ray diffusion coefficient found in the resulting self-consistent model may explain the peaks in the secondary to primary nuclei ratios observed at about 1 GeV/nucleon.
Nonlinear damping of parallel propagating Alfvén waves in high-\(\beta\) plasma is considered. Trapping of thermal ions and Coulomb collisions are taken into account. Saturated damping rate is ...calculated. Applications are made for cosmic ray propagation in the Galaxy.
The diffusion of galactic cosmic rays (CR) is considered. It is anticipated that the nonlinear MHD cascade sets the power-law spectrum of turbulence from the principle scale 100 pc to much smaller ...scales. We found that the dissipation of waves due to the resonant interaction with energetic particles may terminate the cascade at less than 1.e13 cm. The shape of CR diffusion coefficient that was found may explain the observed peaks of secondary to primary nuclei ratios at a few GeV/n.
We study the production of cosmic rays (CRs) in supernova remnants (SNRs), including the reacceleration of background galactic cosmic rays (GCRs) - thus refining the early considerations by Blandford ...& Ostriker (1980) and Wandel et al. (1987) - and the effects of the nuclear spallation inside the sources (the SNRs). This combines for the first time nuclear spallation inside CR sources and in the diffuse interstellar medium, as well as reacceleration, with the injection and subsequent acceleration of suprathermal particles from the postshock thermal pool. Selfconsistent CR spectra are calculated on the basis of the nonlinear kinetic model. It is shown that GCR reacceleration and CR spallation produce a measurable effect at high energies, especially in the secondary to primary (s/p) ratio, making its energy-dependence substantially flatter than predicted by the standard model. Quantitatively, the effect depends strongly upon the density of the surrounding circumstellar matter. GCR reacceleration dominates secondary CR production for a low circumstellar density. It increases the expected s/p ratio substantially and flattens its spectrum to an almost energy-independent form for energies larger than 100 GeV/n if the supernovae explode on average into a hot dilute medium with hydrogen number density \(N_H=0.003\)cm\(^{-3}\). The contribution of CR spallation inside SNRs to the s/p ratio increases with increasing circumstellar density and becomes dominant for \(N_H\gsim 1\) cm\(^{-3}\), leading at high energies to a flat s/p ratio which is only by a factor of three lower than in the case of the hot medium. Measurements of the boron to carbon ratio at energies above 100 GeV/n could be used in comparison with the values predicted here as a consistency test for the supernova origin of the GCRs.
Introduction
Despite the fact that 95% of all <5 years of age children with developmental disabilities including Autism Spectrum Disorders (ASD) live in low- and middle-income countries (LAMI), to ...date there is an information gap in LAMI studies including Republic of Georgia.
Objectives
To estimate the prevalence and describe the clinical characteristics of ASDs among the third-grade school students using a total population approach.
Methods
The target population (N=27,336) included all 3rd grade students of schools of five main cities of Georgia. The study was conducted in four steps: phase I screening, sampling of screen positive students, phase II confirmative diagnostic assessment, and best-estimate diagnosis. Parents and teachers completed two screening questionnaires in phase I: 27-item Autism Spectrum Screening Questionnaire (ASSQ) and 25-item Strengths and Difficulties Questionnaire (SDQ). In phase II, screen-positive children were evaluated using standardized diagnostic assessments.
Results
Overall, 16,654 students (82%) were assessed by either parent and/or teacher. Students whose ASSQ and/or SDQ scores were in the top 10
th
percentile were considered as screened positive for diagnostic assessment (N=1976). Of 300 students completed diagnostic assessment 53 were diagnosed ASD. Crude prevalence of ASDs was estimated to be 4.5%. 75% of cases of ASD were first diagnosed. Efforts are currently underway to compute adjusted prevalence, which will be available for the Conference presentation.
Conclusions
The prevalence data of ASD is important to assess the burden of the disorder and facilitate better understanding of specifics of the disorder in different part of the world.
Disclosure
No significant relationships.
