418 research outputs found
Intrinsically triple-linked graphs in RP^3
Flapan--Naimi--Pommersheim showed that every spatial embedding of ,
the complete graph on ten vertices, contains a non-split three-component link;
that is, is intrinsically triple-linked in . The work of
Bowlin--Foisy and Flapan--Foisy--Naimi--Pommersheim extended the list of known
intrinsically triple-linked graphs in to include several other
families of graphs. In this paper, we will show that while some of these graphs
can be embedded 3-linklessly in , is intrinsically
triple-linked in .Comment: 23 pages, 6 figures; v2: revised introduction, minor corrections, new
outlines to longer proof
Better branch prediction through prophet/critic hybrids
The prophet/critic hybrid conditional branch predictor has two component predictors. The prophet uses a branch's history to predict its direction. We call this prediction and the ones for branches following it the branch future. The critic uses the branch's history and future to critique the prophet's prediction. The hybrid combines the prophet's prediction with the critique, either agrees or disagree, forming the branch's overall prediction. Results shows these hybrids can reduce mispredicts by 39 percent and improve processor performance by 7.8 percent.Peer ReviewedPostprint (published version
On the Morphology and Chemical Composition of the HR 4796A Debris Disk
[abridged] We present resolved images of the HR 4796A debris disk using the
Magellan adaptive optics system paired with Clio-2 and VisAO. We detect the
disk at 0.77 \microns, 0.91 \microns, 0.99 \microns, 2.15 \microns, 3.1
\microns, 3.3 \microns, and 3.8 \microns. We find that the deprojected center
of the ring is offset from the star by 4.761.6 AU and that the deprojected
eccentricity is 0.060.02, in general agreement with previous studies. We
find that the average width of the ring is 14, also comparable to
previous measurements. Such a narrow ring precludes the existence of
shepherding planets more massive than \about 4 \mj, comparable to hot-start
planets we could have detected beyond \about 60 AU in projected separation.
Combining our new scattered light data with archival HST/STIS and HST/NICMOS
data at \about 0.5-2 \microns, along with previously unpublished Spitzer/MIPS
thermal emission data and all other literature thermal data, we set out to
constrain the chemical composition of the dust grains. After testing 19
individual root compositions and more than 8,400 unique mixtures of these
compositions, we find that good fits to the scattered light alone and thermal
emission alone are discrepant, suggesting that caution should be exercised if
fitting to only one or the other. When we fit to both the scattered light and
thermal emission simultaneously, we find mediocre fits (reduced chi-square
\about 2). In general, however, we find that silicates and organics are the
most favored, and that water ice is usually not favored. These results suggest
that the common constituents of both interstellar dust and solar system comets
also may reside around HR 4796A, though improved modeling is necessary to place
better constraints on the exact chemical composition of the dust.Comment: Accepted to ApJ on October 27, 2014. 21 pages, 12 figures, 4 table
Cytochrome P450 20A1 in zebrafish: Cloning, regulation and potential involvement in hyperactivity disorders
Cytochrome P450 (CYP) enzymes for which there is no functional information are considered "orphan" CYPs. Previous studies showed that CYP20A1, an orphan, is expressed in human hippocampus and substantia nigra, and in zebrafish (Danio rerio) CYP20A1 maternal transcript occurs in eggs, suggesting involvement in brain and in early development. Moreover, hyperactivity is reported in humans with chromosome 2 microdeletions including CYP20A1. We examined CYP20A1 in zebrafish, including impacts of chemical exposure on expression. Zebrafish CYP20A1 cDNA was cloned, sequenced, and aligned with cloned human CYP20A1 and predicted vertebrate orthologs. CYP20A1s share a highly conserved N-terminal region and unusual sequences in the I-helix and the heme-binding CYP signature motifs. CYP20A1 mRNA expression was observed in adult zebrafish organs including the liver, heart, gonads, spleen and brain, as well as the eye and optic nerve. Putative binding sites in proximal promoter regions of CYP20A1s, and response of zebrafish CYP20A1 to selected nuclear and xenobiotic receptor agonists, point to up-regulation by agents involved in steroid hormone response, cholesterol and lipid metabolism. There also was a dose-dependent reduction of CYP20A1 expression in embryos exposed to environmentally relevant levels of methylmercury. Morpholino knockdown of CYP20A1 in developing zebrafish resulted in behavioral effects, including hyperactivity and a slowing of the optomotor response in larvae. The results suggest that altered expression of CYP20A1 might be part of a mechanism linking methylmercury exposure to neurobehavioral deficits. The expanded information on CYP20A1 brings us closer to "deorphanization" CYP20A1 functions and its roles in health and disease
Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector
Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02 TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1 μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos2Δϕ modulation for all ΣETPb ranges and particle pT
Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS
The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured
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