12,409 research outputs found
Investigations with satellite data. 2: Temperature retrievals
A method for retrieving atmospheric temperatures in a severe storm situation was investigated. Retrieval was accomplished through the aid of satellite radiance measurements and nearby radiosondes. A set of coefficients was derived which when multiplied by the measured radiances, yielded smaller temperature retrieval errors than the minimum-information retrieval method
Wilderness attribute mapping in the United Kingdom
A wilderness continuum concept can identify the wilder areas of Britain. Geographical Information Systems are used to present information on these areas and solicit public opinion as to which factors are perceived to be important wilderness quality indicators. Consensus maps are compiled from a composite of individual responses and the results compared to Britain’s network of protected areas
Dense gas and star formation in individual Giant Molecular Clouds in M31
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.9 pages, 6 figures, accepted for publication in MNRASStudies both of entire galaxies and of local Galactic star formation indicate a dependency of a molecular cloud's star formation rate (SFR) on its dense gas mass. In external galaxies, such measurements are derived from HCN(1-0) observations, usually encompassing many Giant Molecular Clouds (GMCs) at once. The Andromeda galaxy (M31) is a unique laboratory to study the relation of the SFR and HCN emission down to GMC scales at solar-like metallicities. In this work, we correlate our composite SFR determinations with archival HCN, HCO+, and CO observations, resulting in a sample of nine reasonably representative GMCs. We find that, at the scale of individual clouds, it is important to take into account both obscured and unobscured star formation to determine the SFR. When correlated against the dense-gas mass from HCN, we find that the SFR is low, in spite of these refinements. We nevertheless retrieve an SFR - dense-gas mass correlation, confirming that these SFR tracers are still meaningful on GMC scales. The correlation improves markedly when we consider the HCN/CO ratio instead of HCN by itself. This nominally indicates a dependency of the SFR on the dense-gas fraction, in contradiction to local studies. However, we hypothesize that this partly reflects the limited dynamic range in dense-gas mass, and partly that the ratio of single-pointing HCN and CO measurements may be less prone to systematics like sidelobes. In this case, the HCN/CO ratio would importantly be a better empirical measure of the dense-gas content itself.Peer reviewedFinal Published versio
Hydrodynamic Limit for an Hamiltonian System with Boundary Conditions and Conservative Noise
We study the hyperbolic scaling limit for a chain of N coupled anharmonic
oscillators. The chain is attached to a point on the left and there is a force
(tension) acting on the right. In order to provide good ergodic
properties to the system, we perturb the Hamiltonian dynamics with random local
exchanges of velocities between the particles, so that momentum and energy are
locally conserved. We prove that in the macroscopic limit the distributions of
the elongation, momentum and energy, converge to the solution of the Euler
system of equations, in the smooth regime.Comment: New deeply revised version. 1 figure adde
Survey- and fishery-derived estimates of Pacific cod (Gadus macrocephalus) biomass: implications for strategies to reduce interactions between groundfish fisheries and Steller sea lions (Eumetopias jubatus)
Survey- and fishery-derived biomass estimates have
indicated that the harvest indices for Pacific cod (Gadus macrocephalus) within a portion of Steller sea lion (Eumetopias jubatus) critical habitat in February and March 2001 were five to 16 times greater than the annual rate for the entire Bering Sea-Aleutian Islands stock. A bottom
trawl survey yielded a cod biomass estimate of 49,032 metric tons (t) for the entire area surveyed, of which
less than half (23,329 t) was located within the area used primarily by the commercial fishery, which caught 11,631 t of Pacific cod. Leslie depletion analyses of fishery data yielded biomass estimates of approximately 14,500 t (95% confidence intervals of approximately 9,000–25,000 t), which
are within the 95% confidence interval on the fished area survey estimate (12,846–33,812 t). These data indicate
that Leslie analyses may be useful in estimating local fish biomass and harvest indices for certain marine fisheries that are well constrained spatially and relatively short in duration (weeks). In addition, fishery effects on prey availability within the time and space scales relevant
to foraging sea lions may be much greater than the effects indicated by annual harvest rates estimated from stock assessments averaged across the range of the target spe
The Diversity of Type Ia Supernovae from Broken Symmetries
Type Ia supernovae result when carbon-oxygen white dwarfs in binary systems
accrete mass from companion stars, reach a critical mass, and explode. The near
uniformity of their light curves makes these supernovae good standard candles
for measuring cosmic expansion, but a correction must be applied to account for
the fact that the brighter supernovae have broader light curves.
One-dimensional modelling, with a certain choice of parameters, can reproduce
this general trend in the width-luminosity relation, but the processes of
ignition and detonation have recently been shown to be intrinsically
asymmetric. Here we report on multi-dimensional modelling of the explosion
physics and radiative transfer that reveals that the breaking of spherical
symmetry is a critical factor in determining both the width luminosity relation
and the observed scatter about it. The deviation from sphericity can also
explain the finite polarization detected in the light from some supernovae. The
slope and normalization of the width-luminosity relation has a weak dependence
on certain properties of the white dwarf progenitor, in particular the trace
abundances of elements other than carbon and oxygen. Failing to correct for
this effect could lead to systematic overestimates of up to 2% in the distance
to remote supernovae.Comment: Accepted to Natur
Rapid, Specific Determination of Iodine and Iodide by Combined Solid-Phase Extraction/Diffuse Reflectance Spectroscopy
A new, rapid methodology for trace analysis using solid-phase extraction is described. The two-step methodology is based on the concentration of an analyte onto a membrane disk and on the determination by diffuse reflectance spectroscopy of the amount of analyte extracted on the disk surface. This method, which is adaptable to a wide range of analytes, has been used for monitoring ppm levels of iodine and iodide in spacecraft water. Iodine is used as a biocide in spacecraft water. For these determinations, a water sample is passed through a membrane disk by means of a 10-mL syringe that is attached to a disk holder assembly. The disk, which is a polystyrene−divinylbenzene composite, is impregnated with poly(vinylpyrrolidone) (PVP), which exhaustively concentrates iodine as a yellow iodine−PVP complex. The amount of concentrated iodine is then determined in only 2 s by using a hand-held diffuse reflectance spectrometer by comparing the result with a calibration curve based on the Kubelka−Munk function. The same general procedure can be used to determine iodide levels after its facile and exhaustive oxidation to iodine by peroxymonosulfate (i.e., Oxone reagent). For samples containing both analytes, a two-step procedure can be used in which the iodide concentration is calculated from the difference in iodine levels before and after treatment of the sample with peroxymonosulfate. With this methodology, iodine and iodide levels in the 0.1−5.0 ppm range can be determined with a total workup time of ∼60 s with a RSD of ∼6%
Nonlocality with less Complementarity
In quantum mechanics, nonlocality (a violation of a Bell inequality) is
intimately linked to complementarity, by which we mean that consistently
assigning values to different observables at the same time is not possible.
Nonlocality can only occur when some of the relevant observables do not
commute, and this noncommutativity makes the observables complementary. Beyond
quantum mechanics, the concept of complementarity can be formalized in several
distinct ways. Here we describe some of these possible formalizations and ask
how they relate to nonlocality. We partially answer this question by describing
two toy theories which display nonlocality and obey the no-signaling principle,
although each of them does not display a certain kind of complementarity. The
first toy theory has the property that it maximally violates the CHSH
inequality, although the corresponding local observables are pairwise jointly
measurable. The second toy theory also maximally violates the CHSH inequality,
although its state space is classical and all measurements are mutually
nondisturbing: if a measurement sequence contains some measurement twice with
any number of other measurements in between, then these two measurements give
the same outcome with certainty.Comment: 6 pages, published versio
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