57 research outputs found
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
Clusters of galaxies: setting the stage
Clusters of galaxies are self-gravitating systems of mass ~10^14-10^15 Msun.
They consist of dark matter (~80 %), hot diffuse intracluster plasma (< 20 %)
and a small fraction of stars, dust, and cold gas, mostly locked in galaxies.
In most clusters, scaling relations between their properties testify that the
cluster components are in approximate dynamical equilibrium within the cluster
gravitational potential well. However, spatially inhomogeneous thermal and
non-thermal emission of the intracluster medium (ICM), observed in some
clusters in the X-ray and radio bands, and the kinematic and morphological
segregation of galaxies are a signature of non-gravitational processes, ongoing
cluster merging and interactions. In the current bottom-up scenario for the
formation of cosmic structure, clusters are the most massive nodes of the
filamentary large-scale structure of the cosmic web and form by anisotropic and
episodic accretion of mass. In this model of the universe dominated by cold
dark matter, at the present time most baryons are expected to be in a diffuse
component rather than in stars and galaxies; moreover, ~50 % of this diffuse
component has temperature ~0.01-1 keV and permeates the filamentary
distribution of the dark matter. The temperature of this Warm-Hot Intergalactic
Medium (WHIM) increases with the local density and its search in the outer
regions of clusters and lower density regions has been the quest of much recent
observational effort. Over the last thirty years, an impressive coherent
picture of the formation and evolution of cosmic structures has emerged from
the intense interplay between observations, theory and numerical experiments.
Future efforts will continue to test whether this picture keeps being valid,
needs corrections or suffers dramatic failures in its predictive power.Comment: 20 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 2; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Dust in Supernovae and Supernova Remnants II: Processing and survival
Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations
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Hanford ferrocyanide waste chemistry and reactivity preliminary catalyst and initiator screening studies
During the 1950s, ferrocyanide was used to scavenge radiocesium from aqueous nitrate-containing Hanford wastes. During the production of defense materials and while these wastes were stored in high-level waste tanks at the Hanford Site, some of these wastes were likely mixed with other waste constituents and materials. Recently, Pacific Northwest Laboratory (PNL) was commissioned by Westinghouse Hanford Company (WHC) to investigate the chemical reactivity of these ferrocyanide-bearing wastes. Because of known or potential thermal reactivity hazards associated with ferrocyanide- and nitrate-bearing wastes, and because of the potential for different materials to act as catalysts or initiators of the reactions about which there is concern, we at PNL have begun investigating the effects of the other potential waste constituents. This report presents the results of a preliminary screening study to identify classes of materials that might be in the Hanford high-level waste tanks and that could accelerate or reduce the starting temperature of the reaction(s) of concern. We plan to use the resulted of this study to determine which materials or class of materials merit additional research
Core banking
Article adapted from authors book 'Banking: Restoring the Health & Profitability of the Banking System' published by Harper Collins 1991SIGLEAvailable from British Library Document Supply Centre- DSC:7755.0344(92/12) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
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Ferrocyanide safety project: Task 3. 5 cyanide species analytical methods development
This report summarizes the results of studies conducted in FY 1992 to develop methods for the identification and quantification of cyanide species in ferrocyanide tank waste. Currently there are 24 high-level waste storage tanks at the Hanford Site that have been placed on a Ferrocyanide Tank Watchlist because they contain an estimated 1,000 g-moles or greater amount of precipitated ferrocyanide. This amount of ferrocyanide is of concern because the consequences of a potential explosion may exceed those reported previously in safety analyses. The threshold concentration of total cyanide within the tank waste matrix that is expected to be a safety concern is estimated at approximately 1 to 3 wt%. Methods for detection and speciation of ferrocyanide complexes in actual waste are needed to definitively measure and quantitate the amount of ferrocyanides present within actual waste tanks to a lower limit of at least 0.1 wt% in order to bound the safety concern
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