15 research outputs found
Influence of Impact Parameter on Thermal Description of Relativistic Heavy Ion Collisions at GSI/SIS
Attention is drawn to the role played by the size of the system in the
thermodynamic analysis of particle yields in relativistic heavy ion collisions
at SIS energies. This manifests itself in the non-linear dependence of K+ and
K- yields in collisions at 1 -- 2 A.GeV on the number of participants. It
is shown that this dependence can be quantitatively well described in terms of
a thermal model with a canonical strangeness conservation. The measured
particle multiplicity ratios (pi+/p, pi-/pi+, d/p, K+/pi+ and K+/K- but not
eta/pi0) in central Au-Au and Ni-Ni collisions at 0.8 -- 2.0 A.GeV are also
explained in the context of a thermal model with a common freeze-out
temperature and chemical potential. Including the concept of collective flow a
consistent picture of particle energy distributions is derived with the flow
velocity being strongly impact-parameter dependent.Comment: revtex, 20 figure
The Stroop revisited: a meta-analysis of interference control in AD/HD
Background: An inhibition deficit, including poor interference control, has been implicated as one of the core deficits in AD/HD. Interference control is clinically measured by the Stroop Colour-Word Task. The aim of this meta-analysis was to investigate the strength of an interference deficit in AD/HD as measured by the Stroop Colour-Word Task and to assess the role of moderating variables that could explain the results. These moderating variables included: methods of calculating the interference score, comorbid reading and psychiatric disorders, AD/HD-subtypes, gender, age, intellectual functioning, medication, and sample size. Methods: Seventeen independent studies were located including 1395 children, adolescents, and young adults, in the age range of 6-27 years. A meta-analysis was conducted to assess the effect sizes for the scores on the word and the colour card as well as the interference score. Results: Children with AD/HD performed more poorly on all three dependent variables. The effect sizes for word reading (d = .49) and colour naming (d = .58) were larger and more homogeneous than the effect size for the interference score (d = .35). The method used to calculate the interference score strongly influenced the findings for this measure. When interference control was calculated as the difference between the score on the colour card minus the score on the colour-word card, no differences were found between AD/HD groups and normal control groups. Discussion: The Stroop Colour-Word Task, in standard form, does not provide strong evidence for a deficit in interference control in AD/HD. However, the Stroop Colour-Word Task may not be a valid measure of interference control in AD/HD and alternative methodologies may be needed to test this aspect of the inhibitory deficit model in AD/HD. © Association for Child Psychology Psychiatry, 2004
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age