47,357 research outputs found
Infrared diode laser spectroscopy of the fundamental band of NF(a1Δ)
Thirty-one lines of the fundamental vibration–rotation band of the NF free radical in its a 1 state have been detected in absorption near 8.6 µm using a tunable infrared diode laser. Linewidths were Doppler limited and several transitions were accompanied by resolved hyperfine structure due to fluorine and nitrogen nuclear moments. Wave number calibration using accurately determined N2O lines yielded v0 = 1165.952±0.001 cm^−1 for the band center. Rotational and centrifugal distortion constants for both v = 0 and 1 states have also been determined
Tidal stripping as a mechanism for placing globular clusters on wide orbits: the case of MGC1 in M31
The globular clusters of large spiral galaxies can be divided into two
populations: one which formed in-situ and one which comprises clusters tidally
stripped away from other galaxies. In this paper we investigate the
contribution to the outer globular cluster population in the M31 galaxy through
donation of clusters from dwarf galaxies. We test this numerically by comparing
the contribution of globular clusters from simulated encounters to the observed
M31 globular cluster population. To constrain our simulations, we specifically
investigate the outermost globular cluster in the M31 system, MGC1. The remote
location of MGC1 favours the idea of it being captured, however, the cluster is
devoid of features associated with tidal interactions. Hence we separate
simulations where tidal features are present and where they are hidden. We find
that our simulated encounters can place clusters on MGC1-like orbits. In
addition, we find that tidal stripping of clusters from dwarf galaxies leaves
them on orbits having a range of separations, broadly matching those observed
in M31. We find that the specific energies of globular clusters captured by M31
closely matches those of the incoming host dwarf galaxies. Furthermore, in our
simulations we find an equal number of accreted clusters on co-rotating and
counter-rotating orbits within M31 and use this to infer the fraction of
clusters that has been accreted. We find that even close in roughly 50% of the
clusters are accreted, whilst this figure increases to over 80% further out.Comment: 17 pages, 12 figures. Accepted for publication in MNRA
An Improved Method for Calibrating Purchase Intentions in Stated Preference Demand Models
The Orbit demand model allows the magnitude of the calibration to stated purchase intentions to vary based on the magnitude of the stated quantities. Using an empirical example of stated trips, we find that the extent of calibration varies substantially with less correction needed at small stated trips (–25%) but larger corrections at higher quantities of stated visits (–48%). We extend the Orbit model to calculate consumer surplus per stated trip of $26. Combining the calibrations in stated trips and value per trip, the Orbit model provides estimates of annual benefits from 60% to 111% less than the count data model.hypothetical bias, Orbit, ordered probit model, travel cost model, recreation, stated preference, Agribusiness, Agricultural Finance, Consumer/Household Economics, Demand and Price Analysis, Financial Economics, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics, Marketing, Production Economics, Productivity Analysis, Research Methods/ Statistical Methods, D12, H44, Q26, Q51,
A New Approach to Correct for Hypothetical Bias in Stated Preference Models
Many times economists are asked to estimate the demand for new consumer goods or services for which no market data exists. Typically market researchers and economists answer this challenge using surveys that ask about intended purchases (Louviere, et al. 2000) or what has become known as stated preference (SP) data. Tying this data to revealed preference (RP), or actual behavior, has been a target in a number of studies. Simplistic calibrations have been investigated in past RP-SP studies, such as Loomis, et al. 2001. This paper offers an alternative solution that allows the magnitude of the calibration correction to vary based on Klein and Sherman's (1997) Orbit procedure. This paper extends the original Orbit procedure of Klein and Sherman by Combining stated and revealed preference data on quantities and prices in the first stage, incorporating a correction for heteroskedasticity, and developing methods to calculate consumer surplus and elasticities.Research Methods/ Statistical Methods,
Monte Carlo Predictions of Far-Infrared Emission from Spiral Galaxies
We present simulations of Far Infrared (FIR) emission by dust in spiral
galaxies, based on the Monte Carlo radiative transfer code of Bianchi, Ferrara
& Giovanardi (1996). The radiative transfer is carried out at several
wavelength in the Ultraviolet, optical and Near Infrared, to cover the range of
the stellar Spectral Energy Distribution (SED). Together with the images of the
galactic model, a map of the energy absorbed by dust is produced. Using
Galactic dust properties, the spatial distribution of dust temperature is
derived under the assumption of thermal equilibrium. A correction is applied
for non-equilibrium emission in the Mid Infrared. Images of dust emission can
then be produced at any wavelength in the FIR.
We show the application of the model to the spiral galaxy NGC 6946. The
observed stellar SED is used as input and models are produced for different
star-dust geometries. It is found that only optically thick dust disks can
reproduce the observed amount of FIR radiation. However, it is not possible to
reproduce the large FIR scalelength suggested by recent observation of spirals
at 200 um, even when the scalelength of the dust disk is larger than that for
stars. Optically thin models have ratios of optical/FIR scalelengths closer to
the 200um observations, but with smaller absolute scalelengths than optically
thick cases. The modelled temperature distributions are compatible with
observations of the Galaxy and other spirals. We finally discuss the
approximations of the model and the impact of a clumpy stellar and dust
structure on the FIR simulations.Comment: 19 pages, 6 figures, accepted by A&
Massless interacting particles
We show that classical electrodynamics of massless charged particles and the
Yang--Mills theory of massless quarks do not experience rearranging their
initial degrees of freedom into dressed particles and radiation. Massless
particles do not radiate. We consider a version of the direct interparticle
action theory for these systems following the general strategy of Wheeler and
Feynman.Comment: LaTeX; 20 pages; V4: discussion is slightly modified to clarify some
important points, relevant references are adde
SCUBA imaging of NGC 7331 dust ring
We present observations of the spiral galaxy NGC 7331 using the
Sub-millimetre Common User Bolometer Array (SCUBA) on the James Clark Maxwell
Telescope. We have detected a dust ring of 45 arcsec radius (3.3 kpc) at
wavelengths of 450 and 850-micron. The dust ring is in good correspondence with
other observations of the ring in the mid-infrared (MIR), CO and
radio-continuum, suggesting that the observed dust is associated with the
molecular gas and star formation. A B-K colour map shows an analogous ring
structure with an asymmetry about the major axis, consistent with the
extinction being produced by a dust ring. The derived temperature of the dust
lies between 16 and 31 K and the gas-to-dust ratio between 150 and 570,
depending on the assumed dust emission efficiency index (beta=1.5 or 2.).Comment: 5 pages, 6 figures, to be published in MNRA
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