3,956 research outputs found
A vapor barrier for cold testing printed circuit cards
Cold testing method prevents formation of frost on printed circuit boards and part holders during testing at sub-zero temperatures. Freon permits rapid attainment of the required testing temperature
Supernova Constraints and Systematic Uncertainties from the First Three Years of the Supernova Legacy Survey
We combine high-redshift Type Ia supernovae from the first three years of the Supernova Legacy Survey (SNLS) with other supernova (SN) samples, primarily at lower redshifts, to form a high-quality joint sample of 472 SNe (123 low-z, 93 SDSS, 242 SNLS, and 14 Hubble Space Telescope). SN data alone require cosmic acceleration at >99.999% confidence, including systematic effects. For the dark energy equation of state parameter (assumed constant out to at least z = 1.4) in a flat universe, we find w = –0.91^(+0.16)_(–0.20)(stat)^(+0.07)_(–0.14)(sys) from SNe only, consistent with a cosmological constant. Our fits include a correction for the recently discovered relationship between host-galaxy mass and SN absolute brightness. We pay particular attention to systematic uncertainties, characterizing them using a systematic covariance matrix that incorporates the redshift dependence of these effects, as well as the shape-luminosity and color-luminosity relationships. Unlike previous work, we include the effects of systematic terms on the empirical light-curve models. The total systematic uncertainty is dominated by calibration terms. We describe how the systematic uncertainties can be reduced with soon to be available improved nearby and intermediate-redshift samples, particularly those calibrated onto USNO/SDSS-like systems
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Requirements Engineering as Creative Problem Solving: A Research Agenda for Idea Finding
This vision paper frames requirements engineering as a creative problem solving process. Its purpose is to enable requirements researchers and practitioners to recruit relevant theories, models, techniques and tools from creative problem solving to understand and support requirements processes more effectively. It uses 4 drivers to motivate the case for requirements engineering as a creative problem solving process. It then maps established requirements activities onto one of the longest-established creative problem solving processes, and uses these mappings to locate opportunities for the application of creative problem solving in requirements engineering. The second half of the paper describes selected creativity theories, techniques, software tools and training that can be adopted to improve requirements engineering research and practice. The focus is on support for problem and idea finding - two creative problem solving processes that our investigation revealed are poorly supported in requirements engineering. The paper ends with a research agenda to incorporate creative processes, techniques, training and tools in requirements projects
Higgs Boson Phenomenology in a Simple Model with Vector Resonances
In this paper we consider a simple scenario where the Higgs boson and two
vector resonances are supposed to arise from a new strong interacting sector.
We use the ATLAS measurements of the dijet spectrum to set limits on the masses
of the resonances. Additionally we compute the Higgs boson decay to two photons
and found, when compare to the Standard Model prediction, a small excess which
is compatible with ATLAS measurements. Finally we make prediction for
Higgs-strahlung processes for the LHC running at 14 TeV
Herschel observations of EXtra-Ordinary Sources: Analysis of the HIFI 1.2 THz Wide Spectral Survey Toward Orion KL II. Chemical Implications
We present chemical implications arising from spectral models fit to the
Herschel/HIFI spectral survey toward the Orion Kleinmann-Low nebula (Orion KL).
We focus our discussion on the eight complex organics detected within the HIFI
survey utilizing a novel technique to identify those molecules emitting in the
hottest gas. In particular, we find the complex nitrogen bearing species
CHCN, CHCN, CHCN, and NHCHO systematically
trace hotter gas than the oxygen bearing organics CHOH, CHOH,
CHOCH, and CHOCHO, which do not contain nitrogen. If these
complex species form predominantly on grain surfaces, this may indicate
N-bearing organics are more difficult to remove from grain surfaces than
O-bearing species. Another possibility is that hot (T300 K)
gas phase chemistry naturally produces higher complex cyanide abundances while
suppressing the formation of O-bearing complex organics. We compare our derived
rotation temperatures and molecular abundances to chemical models, which
include gas-phase and grain surface pathways. Abundances for a majority of the
detected complex organics can be reproduced over timescales 10
years, with several species being under predicted by less than 3.
Derived rotation temperatures for most organics, furthermore, agree reasonably
well with the predicted temperatures at peak abundance. We also find that
sulfur bearing molecules which also contain oxygen (i.e. SO, SO, and OCS)
tend to probe the hottest gas toward Orion KL indicating the formation pathways
for these species are most efficient at high temperatures.Comment: 31 pages, 6 figures, 1 Table, accepted to the Astrophysical Journa
5-micron photometry of late-type dwarfs
We present narrowband-M photometry of nine low-mass dwarfs with spectral
types ranging from M2.5 to L0.5. Combining the (L'-M') colours derived from our
observations with data from the literature, we find colours consistent with a
Rayleigh-Jeans flux distribution for spectral types earlier than M5, but
enhanced F_3.8/F_4.7 flux ratios (negative (L'-M') colours) at later spectral
types. This probably reflects increased absorption at M' due to the CO
fundamental band. We compare our results against recent model predictions and
briefly discuss the implications.Comment: accepted for the Astronomical Journa
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