14,735 research outputs found
The Manchester occulting mask imager (MOMI) - first results on the environment of P Cygni
The design and first use of the Manchester occulting mask imager (MOMI) is
described. This device, when combined with the Cassegrain or Ritchey-Chretien
foci of large telescopes, is dedicated to the imagery of faint line emission
regions around bright central sources.
Initial observations, with MOMI on the Nordic Optical telescope (NOT), of the
V=4.8 mag P~Cygni environment, have revealed a ~5~arcmin long [NII] 6584A
emitting filament projecting from the outer nebular shell of this luminous blue
variable (LBV) star. The presence of a mono-polar lobe older than both the
inner (22 arcsec diameter) and outer (1.6 arcmin diameter) shells is suggested.Comment: 4 pages, 4 figures, accepted MNRAS 1998 June 1
A Second Relativistic Mean Field and Virial Equation of State for Astrophysical Simulations
We generate a second equation of state (EOS) of nuclear matter for a wide
range of temperatures, densities, and proton fractions for use in supernovae,
neutron star mergers, and black hole formation simulations. We employ full
relativistic mean field (RMF) calculations for matter at intermediate density
and high density, and the Virial expansion of a non-ideal gas for matter at low
density. For this EOS we use the RMF effective interaction FSUGold, whereas our
earlier EOS was based on the RMF effective interaction NL3. The FSUGold
interaction has a lower pressure at high densities compared to the NL3
interaction. We calculate the resulting EOS at over 100,000 grid points in the
temperature range = 0 to 80 MeV, the density range = 10 to 1.6
fm, and the proton fraction range = 0 to 0.56. We then interpolate
these data points using a suitable scheme to generate a thermodynamically
consistent equation of state table on a finer grid. We discuss differences
between this EOS, our NL3 based EOS, and previous EOSs by Lattimer-Swesty and
H. Shen et al for the thermodynamic properties, composition, and neutron star
structure. The original FSUGold interaction produces an EOS, that we call
FSU1.7, that has a maximum neutron star mass of 1.7 solar masses. A
modification in the high density EOS is introduced to increase the maximum
neutron star mass to 2.1 solar masses and results in a slightly different EOS
that we call FSU2.1. The EOS tables for FSU1.7 and FSU2.1 are available for
download.Comment: updated version according to referee's comments. Phys. Rev. C in
pres
The disjointness of stabilizer codes and limitations on fault-tolerant logical gates
Stabilizer codes are a simple and successful class of quantum
error-correcting codes. Yet this success comes in spite of some harsh
limitations on the ability of these codes to fault-tolerantly compute. Here we
introduce a new metric for these codes, the disjointness, which, roughly
speaking, is the number of mostly non-overlapping representatives of any given
non-trivial logical Pauli operator. We use the disjointness to prove that
transversal gates on error-detecting stabilizer codes are necessarily in a
finite level of the Clifford hierarchy. We also apply our techniques to
topological code families to find similar bounds on the level of the hierarchy
attainable by constant depth circuits, regardless of their geometric locality.
For instance, we can show that symmetric 2D surface codes cannot have non-local
constant depth circuits for non-Clifford gates.Comment: 8+3 pages, 2 figures. Comments welcom
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Estimating drizzle drop size and precipitation rate using two-colour lidar measurements
A method to estimate the size and liquid water content of drizzle drops using lidar measurements at two wavelengths is described. The method exploits the differential absorption of infrared light by liquid water at 905 nm and 1.5 μm, which leads to a different backscatter cross section for water drops larger than ≈50 μm. The ratio of backscatter measured from drizzle samples below cloud base at these two wavelengths (the colour ratio) provides a measure of the median volume drop diameter D0. This is a strong effect: for D0=200 μm, a colour ratio of ≈6 dB is predicted. Once D0 is known, the measured backscatter at 905 nm can be used to calculate the liquid water content (LWC) and other moments of the drizzle drop distribution.
The method is applied to observations of drizzle falling from stratocumulus and stratus clouds. High resolution (32 s, 36 m) profiles of D0, LWC and precipitation rate R are derived. The main sources of error in the technique are the need to assume a value for the dispersion parameter μ in the drop size spectrum (leading to at most a 35% error in R) and the influence of aerosol returns on the retrieval (≈10% error in R for the cases considered here). Radar reflectivities are also computed from the lidar data, and compared to independent measurements from a colocated cloud radar, offering independent validation of the derived drop size distributions
ELISA detection of phenazepam, etizolam, pyrazolam, flubromazepam, diclazepam and delorazepam in blood using Immunalysis® benzodiazepine kit
Phenazepam and etizolam were the first uncontrolled benzodiazepines available for sale in the UK. Pyrazolam, flubromazepam and diclazepam are not used medicinally anywhere in the world; they are produced exclusively for the uncontrolled, recreational market. It is important to know whether potentially abused drugs like these can be detected in routine toxicological screening tests. The purpose of this study was to evaluate whether the Immunalysis® Benzodiazepines ELISA kit could detect phenazepam, etizolam, pyrazolam, flubromazepam, diclazepam and its metabolite delorazepam. Their cross-reactivity was assessed by comparing the absorbance of the drug with that of oxazepam, the reference standard. This study found that these uncontrolled benzodiazepines cross-react sufficiently to produce a positive result with the Immunalysis® Benzodiazepine ELISA kit. Cross-reactivity ranged from 79 to 107% for phenazepam, etizolam, pyrazolam, flubromazepam, diclazepam and delorazepam fortified into blood. The results show that it is possible to detect these newer benzodiazepines with traditional forensic toxicology laboratory tools and it is important to include these benzodiazepines in the confirmation tests
Core-Collapse Supernova Simulations including Neutrino Interactions from the Virial EOS
Core-collapse supernova explosions are driven by a central engine that
converts a small fraction of the gravitational binding energy released during
core collapse to outgoing kinetic energy. The suspected mode for this energy
conversion is the neutrino mechanism, where a fraction of the neutrinos emitted
from the newly formed protoneutron star are absorbed by and heat the matter
behind the supernova shock. Accurate neutrino-matter interaction terms are
crucial for simulating these explosions. In this proceedings for IAUS 331, SN
1987A, 30 years later, we explore several corrections to the neutrino-nucleon
scattering opacity and demonstrate the effect on the dynamics of the
core-collapse supernova central engine via two dimensional
neutrino-radiation-hydrodynamics simulations. Our results reveal that the
explosion properties are sensitive to corrections to the neutral-current
scattering cross section at the 10-20% level, but only for densities at or
above g cmComment: 6 pages, 3 figures, appears in Proc. IAU Symposium 331, SN 1987A, 30
years later - Cosmic Rays and Nuclei from Supernovae and Their Aftermath
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