1,234 research outputs found
WMAP5 constraints on the unified model of dark energy and dark matter
We derive constraints on the parameter space of the unified model of dark
energy and dark matter, the Generalized Chaplygin Gas (GCG), from the
amplitudes and positions of the first few peaks and first trough of the cosmic
microwave background radiation (CMBR) power spectrum, using the latest WMAP
five year data.Comment: 5 pages, 6 figure
Fermi Surface Nesting and the Origin of the Charge Density Wave in NbSe
We use highly accurate density functional calculations to study the band
structure and Fermi surfaces of NbSe2. We calculate the real part of the
non-interacting susceptibility, Re chi_0(q), which is the relevant quantity for
a charge density wave (CDW) instability and the imaginary part, Im chi_0(q),
which directly shows Fermi surface (FS) nesting. We show that there are very
weak peaks in Re chi_0(q) near the CDW wave vector, but that no such peaks are
visible in Im chi_0(q), definitively eliminating FS nesting as a factor in CDW
formation. Because the peak in Re chi_0(q) is broad and shallow, it is unlikely
to be the direct cause of the CDW instability. We briefly address the
possibility that electron-electron interactions (local field effects) produce
additional structure in the total (renormalized) susceptibility, and we discuss
the role of electron-ion matrix elements.Comment: Replacement of Table II values, minor changes to tex
Hatch Dates, Growth, Survival, and Overwinter Mortality of Ageâ0 Alewives in Lake Michigan: Implications for HabitatâSpecific Recruitment Success
Alewives Alosa pseudoharengus are key components of Laurentian Great Lakes ecosystems and spawn in multiple habitat types. Exploration of alewife early life history dynamics within these different habitats should help identify important recruitment processes. During 2001â2003, we quantified physical (temperature, transparency) and biotic (chlorophyll a, zooplankton densities) habitat factors and collected ageâ0 alewives (using ichthyoplankton nets and trawls) in a nearshore region of Lake Michigan and Muskegon Lake, Michigan (a drowned river mouth lake connected to Lake Michigan). We characterized alewife hatch dates, individual condition, growth, mortality, and sizeâdependent overwinter survival to infer differences in habitatâspecific recruitment success. Temperature, turbidity, chlorophyllâa concentrations, and densities of zooplankton prey were consistently higher in Muskegon Lake than in nearshore Lake Michigan. On average, young alewives in Muskegon Lake hatched earlier, grew faster, were in better condition (based on a biphasic lengthâweight relationship), and had greater survival than alewives in Lake Michigan. By the end of the growing season, young alewives in Muskegon Lake obtained a larger size than those residing in nearshore Lake Michigan, suggesting that they were more likely to survive through winter (a period of intense sizeâselective mortality) and ultimately recruit to the adult population.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141621/1/tafs1298.pd
The Effects of Hydrofluoric Acid Addition on the Hydrothermal Synthesis of Templated Uranium Sulfates
The effects of addition of a second acid source (HF) on the formation of uranium sulfates are described in this article. -- author-supplied description
Role of subtyping in detecting Salmonella cross contamination in the laboratory
<p>Abstract</p> <p>Background</p> <p>With the exception of <it>M. tuberculosis</it>, little has been published on the problems of cross-contamination in bacteriology laboratories. We performed a retrospective analysis of subtyping data from the National <it>Salmonella </it>Reference Laboratory (Ireland) from 2000â2007 to identify likely incidents of laboratory cross contamination.</p> <p>Methods</p> <p>Serotyping and antimicrobial susceptibility testing was performed on all <it>Salmonella </it>isolates received in the NSRL. Phage typing was performed on all <it>S</it>. Typhimurium and <it>S</it>. Enteritidis isolates while multi-locus variance analysis (MLVA) was performed on selected <it>S</it>. Typhimurium isolates. Pulsed field gel electrophoresis (PFGE) using the PulseNet standard protocol was performed on selected isolates of various serovars.</p> <p>Results</p> <p>Twenty-three incidents involving fifty-six isolates were identified as likely to represent cross contamination. The probable sources of contamination identified were the laboratory positive control isolate (n = 13), other test isolates (n = 9) or proficiency test samples (n = 1).</p> <p>Conclusion</p> <p>The scale of laboratory cross-contamination in bacteriology is most likely under recognized. Testing laboratories should be aware of the potential for cross-contamination, regularly review protocols to minimize its occurrence and consider it as a possibility when unexpected results are obtained.</p
Structural diversity in organically templated uranium sulfates
The potential of organic amine templates to direct the synthesis of metal sulfate frameworks has been investigated. Eight novel uranyl sulfates have been prepared using a templated uranyl sulfate precursor under hydrothermal conditions. The topologis of the isolated phases vary from the molecular (0-D), to chains (1-D) to layered (2-D) frameworks. [N4C6H 22]2[(UO2)2(SO4) 6] (USO-10) is molecular or zero-dimensional. Two different types of onedimensional uranyl-containing chains have been observed. [N2C 4H12][UO2(H2O)(SO4) 2 (USO-3), [N2C5H14]-[UO 2(H2O)(SO4)2] (USO-4) and [N 2C3H12][UO2(H2O)(SO 4)2 (USO-9) contain chains based upon a [UO 2(SO4)4/2] backbone. [N2C 10H10][UO2(SO4)2· H2O (USO-6) and [N2C6H18][(UO 2)2(H2O)3(SO4) 3] (USO-7) contain chains based upon a [UO2(SO 4)3/3] backbone. Two layered or two-dimensional compounds, [N2C6H14][UO2(H2O) (SO4)2 (USO-5) and [N2C3H 5]2[(UO2)2(SO4) 3] (USO-8) have also been isolated. All the new phases have been characterised using a range of physical techniques including single crystal X-ray structure analysis. © The Royal Society of Chemistry 2003
- âŠ