48 research outputs found
Azimuth Quadrupole Systematics in Au-Au Collisions
We have measured -dependent two-particle number correlations on azimuth
and pseudorapidity for eleven centralities of and 200~GeV
Au-Au collisions at STAR. 2D fits to these angular correlations isolate the
azimuth quadrupole amplitude, denoted , from
localized same-side correlations. Event-plane measurements within
the STAR TPC acceptance can be expressed as a sum of the azimuth quadrupole and
the quadrupole component of the same-side peak. can be
transformed to reveal quadrupole spectra which are approximately
described by a fixed transverse boost and universal L\'evy form nearly
independent of centrality. A parametrization of can be
factored into centrality and -dependent pieces with a simple
dependence above 0.75 GeV/c. Results from STAR are compared to published data
and model predictions.Comment: Conference proceedings for Hot Quarks 201
THE GEOLOGIC CONTEXT OF WONDERSTONE: A COMPLEX, OUTCROP-SCALED PATTERN OF IRONOXIDE CEMENT
Although siderite is a widespread early diagenetic mineral in fluvial systems, it is unstable in oxidizing environments and destroyed in permeable rocks that experience uplift and exhumation. The products of siderite oxidation, however, (mm- to cm-scale rhombs, concretions, and complex bands of iron-oxide cement) are widespread in the rock record of fluvial systems. The fluvial channels of the Shinarump Member of the Chinle Formation in southern Utah and northern Arizona, U.S.A., provide an excellent suite of examples of diagenetic features produced by Triassic and Neogene oxidation of early diagenetic siderite. These diagenetic features also provide direct evidence of the level of the water table during deposition of the Shinarump member. Large, in situ, discoidal concretions containing preserved siderite are present in Shinarump floodplain siltstones. Rip-up clasts derived from the siltstones developed iron-oxide rinds during late-stage, near-surface oxidation. These two structures show that floodplain silts contained abundant organic matter and methanic pore water. Groundwater recharging through these silts carried reducing water through underlying sand bodies and discharged into active channels. Degassing of CO2 and methanogenesis caused rhombic crystals of siderite to precipitate in channel sands during these wet intervals. Some of this siderite may have been oxidized during dry intervals when groundwater circulation reversed, but most siderite in the channel sands was preserved until the Shinarump was exhumed during the Neogene. As oxygenated near-surface water entered joints in the lithified Shinarump, colonies of iron-oxidizing microbes living in the phreatic zone occupied redox boundaries and used the rhombic crystals of siderite in the sandstone and the spherulitic siderite in transported siltstone intraclasts as their sources of energy and carbon. The ferrous iron released from dissolving siderite within the intraclasts was oxidized at the siltstone–sandstone contact, generating rinded concretions similar to those in the Cretaceous Dakota Formation. Complex banding known as wonderstone was produced in the channel sandstones from oxidation of the rhombic siderite; the pattern is a combination of Liesegang bands and microbially mediated cements. The preserved rhombs are pseudomorphs after siderite crystals that were either oxidized during Triassic dry intervals, or escaped Neogene microbial oxidation in the phreatic zone, only to be oxidized abiotically in the vadose zone. Microbes are likely oxidizing Shinarump siderite a few kilometers down dip of outcrops with exposed wonderstone. At such locations, the Shinarump is in contact with overlying watersaturated Quaternary alluvium
Jurassic earthquake sequence recorded by multiple generations of sand blows, Zion National Park, Utah
Earthquakes along convergent plate boundaries commonly occur in sequences that are complete within 1 yr, and may include 8–10 events strong enough to generate sand blows. Dune crossbeds within the Jurassic Navajo Sandstone of Utah (western United States) enclose intact and truncated sand blows, and the intrusive structures that fed them. We mapped the distribution of more than 800 soft-sediment dikes and pipes at two small sites. All water-escape structures intersect a single paleo-surface, and are limited to the upper portion of the underlying set of cross-strata and the lower portion of the overlying set. A small portion of one set of crossbeds that represents ~1 yr of dune migration encloses eight generations of eruptive events. We interpret these superimposed depositional and deformational structures as the record of a single shock-aftershock earthquake sequence. The completeness and temporal detail of this paleoseismic record are unique, and were made possible when sand blows repeatedly erupted onto lee slopes of migrating dunes. Similar records should be sought in modern dunefields with shallow water tables
The azimuth structure of nuclear collisions -- I
We describe azimuth structure commonly associated with elliptic and directed
flow in the context of 2D angular autocorrelations for the purpose of precise
separation of so-called nonflow (mainly minijets) from flow. We extend the
Fourier-transform description of azimuth structure to include power spectra and
autocorrelations related by the Wiener-Khintchine theorem. We analyze several
examples of conventional flow analysis in that context and question the
relevance of reaction plane estimation to flow analysis. We introduce the 2D
angular autocorrelation with examples from data analysis and describe a
simulation exercise which demonstrates precise separation of flow and nonflow
using the 2D autocorrelation method. We show that an alternative correlation
measure based on Pearson's normalized covariance provides a more intuitive
measure of azimuth structure.Comment: 27 pages, 12 figure
Structure, Function, and Evolution of the Thiomonas spp. Genome
Bacteria of the Thiomonas genus are ubiquitous in extreme environments, such as arsenic-rich acid mine drainage (AMD). The genome of one of these strains, Thiomonas sp. 3As, was sequenced, annotated, and examined, revealing specific adaptations allowing this bacterium to survive and grow in its highly toxic environment. In order to explore genomic diversity as well as genetic evolution in Thiomonas spp., a comparative genomic hybridization (CGH) approach was used on eight different strains of the Thiomonas genus, including five strains of the same species. Our results suggest that the Thiomonas genome has evolved through the gain or loss of genomic islands and that this evolution is influenced by the specific environmental conditions in which the strains live